fs/btrfs/ctree.c

   1 /*
   2  * Copyright (C) 2007,2008 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/sched.h>
  20 #include <linux/slab.h>
  21 #include <linux/rbtree.h>
  22 #include <linux/mm.h>
  23 #include "ctree.h"
  24 #include "disk-io.h"
  25 #include "transaction.h"
  26 #include "print-tree.h"
  27 #include "locking.h"
  28
  29 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
  30                       *root, struct btrfs_path *path, int level);
  31 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  32                       const struct btrfs_key *ins_key, struct btrfs_path *path,
  33                       int data_size, int extend);
  34 static int push_node_left(struct btrfs_trans_handle *trans,
  35                           struct btrfs_fs_info *fs_info,
  36                           struct extent_buffer *dst,
  37                           struct extent_buffer *src, int empty);
  38 static int balance_node_right(struct btrfs_trans_handle *trans,
  39                               struct btrfs_fs_info *fs_info,
  40                               struct extent_buffer *dst_buf,
  41                               struct extent_buffer *src_buf);
  42 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
  43                     int level, int slot);
  44 static int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
  45                                  struct extent_buffer *eb);
  46
  47 struct btrfs_path *btrfs_alloc_path(void)
  48 {
  49         return kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);
  50 }
  51
  52 /*
  53  * set all locked nodes in the path to blocking locks.  This should
  54  * be done before scheduling
  55  */
  56 noinline void btrfs_set_path_blocking(struct btrfs_path *p)
  57 {
  58         int i;
  59         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
  60                 if (!p->nodes[i] || !p->locks[i])
  61                         continue;
  62                 btrfs_set_lock_blocking_rw(p->nodes[i], p->locks[i]);
  63                 if (p->locks[i] == BTRFS_READ_LOCK)
  64                         p->locks[i] = BTRFS_READ_LOCK_BLOCKING;
  65                 else if (p->locks[i] == BTRFS_WRITE_LOCK)
  66                         p->locks[i] = BTRFS_WRITE_LOCK_BLOCKING;
  67         }
  68 }
  69
  70 /*
  71  * reset all the locked nodes in the patch to spinning locks.
  72  *
  73  * held is used to keep lockdep happy, when lockdep is enabled
  74  * we set held to a blocking lock before we go around and
  75  * retake all the spinlocks in the path.  You can safely use NULL
  76  * for held
  77  */
  78 noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
  79                                         struct extent_buffer *held, int held_rw)
  80 {
  81         int i;
  82
  83         if (held) {
  84                 btrfs_set_lock_blocking_rw(held, held_rw);
  85                 if (held_rw == BTRFS_WRITE_LOCK)
  86                         held_rw = BTRFS_WRITE_LOCK_BLOCKING;
  87                 else if (held_rw == BTRFS_READ_LOCK)
  88                         held_rw = BTRFS_READ_LOCK_BLOCKING;
  89         }
  90         btrfs_set_path_blocking(p);
  91
  92         for (i = BTRFS_MAX_LEVEL - 1; i >= 0; i--) {
  93                 if (p->nodes[i] && p->locks[i]) {
  94                         btrfs_clear_lock_blocking_rw(p->nodes[i], p->locks[i]);
  95                         if (p->locks[i] == BTRFS_WRITE_LOCK_BLOCKING)
  96                                 p->locks[i] = BTRFS_WRITE_LOCK;
  97                         else if (p->locks[i] == BTRFS_READ_LOCK_BLOCKING)
  98                                 p->locks[i] = BTRFS_READ_LOCK;
  99                 }
 100         }
 101
 102         if (held)
 103                 btrfs_clear_lock_blocking_rw(held, held_rw);
 104 }
 105
 106 /* this also releases the path */
 107 void btrfs_free_path(struct btrfs_path *p)
 108 {
 109         if (!p)
 110                 return;
 111         btrfs_release_path(p);
 112         kmem_cache_free(btrfs_path_cachep, p);
 113 }
 114
 115 /*
 116  * path release drops references on the extent buffers in the path
 117  * and it drops any locks held by this path
 118  *
 119  * It is safe to call this on paths that no locks or extent buffers held.
 120  */
 121 noinline void btrfs_release_path(struct btrfs_path *p)
 122 {
 123         int i;
 124
 125         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
 126                 p->slots[i] = 0;
 127                 if (!p->nodes[i])
 128                         continue;
 129                 if (p->locks[i]) {
 130                         btrfs_tree_unlock_rw(p->nodes[i], p->locks[i]);
 131                         p->locks[i] = 0;
 132                 }
 133                 free_extent_buffer(p->nodes[i]);
 134                 p->nodes[i] = NULL;
 135         }
 136 }
 137
 138 /*
 139  * safely gets a reference on the root node of a tree.  A lock
 140  * is not taken, so a concurrent writer may put a different node
 141  * at the root of the tree.  See btrfs_lock_root_node for the
 142  * looping required.
 143  *
 144  * The extent buffer returned by this has a reference taken, so
 145  * it won't disappear.  It may stop being the root of the tree
 146  * at any time because there are no locks held.
 147  */
 148 struct extent_buffer *btrfs_root_node(struct btrfs_root *root)
 149 {
 150         struct extent_buffer *eb;
 151
 152         while (1) {
 153                 rcu_read_lock();
 154                 eb = rcu_dereference(root->node);
 155
 156                 /*
 157                  * RCU really hurts here, we could free up the root node because
 158                  * it was COWed but we may not get the new root node yet so do
 159                  * the inc_not_zero dance and if it doesn't work then
 160                  * synchronize_rcu and try again.
 161                  */
 162                 if (atomic_inc_not_zero(&eb->refs)) {
 163                         rcu_read_unlock();
 164                         break;
 165                 }
 166                 rcu_read_unlock();
 167                 synchronize_rcu();
 168         }
 169         return eb;
 170 }
 171
 172 /* loop around taking references on and locking the root node of the
 173  * tree until you end up with a lock on the root.  A locked buffer
 174  * is returned, with a reference held.
 175  */
 176 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root)
 177 {
 178         struct extent_buffer *eb;
 179
 180         while (1) {
 181                 eb = btrfs_root_node(root);
 182                 btrfs_tree_lock(eb);
 183                 if (eb == root->node)
 184                         break;
 185                 btrfs_tree_unlock(eb);
 186                 free_extent_buffer(eb);
 187         }
 188         return eb;
 189 }
 190
 191 /* loop around taking references on and locking the root node of the
 192  * tree until you end up with a lock on the root.  A locked buffer
 193  * is returned, with a reference held.
 194  */
 195 struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
 196 {
 197         struct extent_buffer *eb;
 198
 199         while (1) {
 200                 eb = btrfs_root_node(root);
 201                 btrfs_tree_read_lock(eb);
 202                 if (eb == root->node)
 203                         break;
 204                 btrfs_tree_read_unlock(eb);
 205                 free_extent_buffer(eb);
 206         }
 207         return eb;
 208 }
 209
 210 /* cowonly root (everything not a reference counted cow subvolume), just get
 211  * put onto a simple dirty list.  transaction.c walks this to make sure they
 212  * get properly updated on disk.
 213  */
 214 static void add_root_to_dirty_list(struct btrfs_root *root)
 215 {
 216         struct btrfs_fs_info *fs_info = root->fs_info;
 217
 218         if (test_bit(BTRFS_ROOT_DIRTY, &root->state) ||
 219             !test_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state))
 220                 return;
 221
 222         spin_lock(&fs_info->trans_lock);
 223         if (!test_and_set_bit(BTRFS_ROOT_DIRTY, &root->state)) {
 224                 /* Want the extent tree to be the last on the list */
 225                 if (root->objectid == BTRFS_EXTENT_TREE_OBJECTID)
 226                         list_move_tail(&root->dirty_list,
 227                                        &fs_info->dirty_cowonly_roots);
 228                 else
 229                         list_move(&root->dirty_list,
 230                                   &fs_info->dirty_cowonly_roots);
 231         }
 232         spin_unlock(&fs_info->trans_lock);
 233 }
 234
 235 /*
 236  * used by snapshot creation to make a copy of a root for a tree with
 237  * a given objectid.  The buffer with the new root node is returned in
 238  * cow_ret, and this func returns zero on success or a negative error code.
 239  */
 240 int btrfs_copy_root(struct btrfs_trans_handle *trans,
 241                       struct btrfs_root *root,
 242                       struct extent_buffer *buf,
 243                       struct extent_buffer **cow_ret, u64 new_root_objectid)
 244 {
 245         struct btrfs_fs_info *fs_info = root->fs_info;
 246         struct extent_buffer *cow;
 247         int ret = 0;
 248         int level;
 249         struct btrfs_disk_key disk_key;
 250
 251         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 252                 trans->transid != fs_info->running_transaction->transid);
 253         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 254                 trans->transid != root->last_trans);
 255
 256         level = btrfs_header_level(buf);
 257         if (level == 0)
 258                 btrfs_item_key(buf, &disk_key, 0);
 259         else
 260                 btrfs_node_key(buf, &disk_key, 0);
 261
 262         cow = btrfs_alloc_tree_block(trans, root, 0, new_root_objectid,
 263                         &disk_key, level, buf->start, 0);
 264         if (IS_ERR(cow))
 265                 return PTR_ERR(cow);
 266
 267         copy_extent_buffer_full(cow, buf);
 268         btrfs_set_header_bytenr(cow, cow->start);
 269         btrfs_set_header_generation(cow, trans->transid);
 270         btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
 271         btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
 272                                      BTRFS_HEADER_FLAG_RELOC);
 273         if (new_root_objectid == BTRFS_TREE_RELOC_OBJECTID)
 274                 btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
 275         else
 276                 btrfs_set_header_owner(cow, new_root_objectid);
 277
 278         write_extent_buffer_fsid(cow, fs_info->fsid);
 279
 280         WARN_ON(btrfs_header_generation(buf) > trans->transid);
 281         if (new_root_objectid == BTRFS_TREE_RELOC_OBJECTID)
 282                 ret = btrfs_inc_ref(trans, root, cow, 1);
 283         else
 284                 ret = btrfs_inc_ref(trans, root, cow, 0);
 285
 286         if (ret)
 287                 return ret;
 288
 289         btrfs_mark_buffer_dirty(cow);
 290         *cow_ret = cow;
 291         return 0;
 292 }
 293
 294 enum mod_log_op {
 295         MOD_LOG_KEY_REPLACE,
 296         MOD_LOG_KEY_ADD,
 297         MOD_LOG_KEY_REMOVE,
 298         MOD_LOG_KEY_REMOVE_WHILE_FREEING,
 299         MOD_LOG_KEY_REMOVE_WHILE_MOVING,
 300         MOD_LOG_MOVE_KEYS,
 301         MOD_LOG_ROOT_REPLACE,
 302 };
 303
 304 struct tree_mod_move {
 305         int dst_slot;
 306         int nr_items;
 307 };
 308
 309 struct tree_mod_root {
 310         u64 logical;
 311         u8 level;
 312 };
 313
 314 struct tree_mod_elem {
 315         struct rb_node node;
 316         u64 logical;
 317         u64 seq;
 318         enum mod_log_op op;
 319
 320         /* this is used for MOD_LOG_KEY_* and MOD_LOG_MOVE_KEYS operations */
 321         int slot;
 322
 323         /* this is used for MOD_LOG_KEY* and MOD_LOG_ROOT_REPLACE */
 324         u64 generation;
 325
 326         /* those are used for op == MOD_LOG_KEY_{REPLACE,REMOVE} */
 327         struct btrfs_disk_key key;
 328         u64 blockptr;
 329
 330         /* this is used for op == MOD_LOG_MOVE_KEYS */
 331         struct tree_mod_move move;
 332
 333         /* this is used for op == MOD_LOG_ROOT_REPLACE */
 334         struct tree_mod_root old_root;
 335 };
 336
 337 static inline void tree_mod_log_read_lock(struct btrfs_fs_info *fs_info)
 338 {
 339         read_lock(&fs_info->tree_mod_log_lock);
 340 }
 341
 342 static inline void tree_mod_log_read_unlock(struct btrfs_fs_info *fs_info)
 343 {
 344         read_unlock(&fs_info->tree_mod_log_lock);
 345 }
 346
 347 static inline void tree_mod_log_write_lock(struct btrfs_fs_info *fs_info)
 348 {
 349         write_lock(&fs_info->tree_mod_log_lock);
 350 }
 351
 352 static inline void tree_mod_log_write_unlock(struct btrfs_fs_info *fs_info)
 353 {
 354         write_unlock(&fs_info->tree_mod_log_lock);
 355 }
 356
 357 /*
 358  * Pull a new tree mod seq number for our operation.
 359  */
 360 static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
 361 {
 362         return atomic64_inc_return(&fs_info->tree_mod_seq);
 363 }
 364
 365 /*
 366  * This adds a new blocker to the tree mod log's blocker list if the @elem
 367  * passed does not already have a sequence number set. So when a caller expects
 368  * to record tree modifications, it should ensure to set elem->seq to zero
 369  * before calling btrfs_get_tree_mod_seq.
 370  * Returns a fresh, unused tree log modification sequence number, even if no new
 371  * blocker was added.
 372  */
 373 u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
 374                            struct seq_list *elem)
 375 {
 376         tree_mod_log_write_lock(fs_info);
 377         spin_lock(&fs_info->tree_mod_seq_lock);
 378         if (!elem->seq) {
 379                 elem->seq = btrfs_inc_tree_mod_seq(fs_info);
 380                 list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
 381         }
 382         spin_unlock(&fs_info->tree_mod_seq_lock);
 383         tree_mod_log_write_unlock(fs_info);
 384
 385         return elem->seq;
 386 }
 387
 388 void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
 389                             struct seq_list *elem)
 390 {
 391         struct rb_root *tm_root;
 392         struct rb_node *node;
 393         struct rb_node *next;
 394         struct seq_list *cur_elem;
 395         struct tree_mod_elem *tm;
 396         u64 min_seq = (u64)-1;
 397         u64 seq_putting = elem->seq;
 398
 399         if (!seq_putting)
 400                 return;
 401
 402         spin_lock(&fs_info->tree_mod_seq_lock);
 403         list_del(&elem->list);
 404         elem->seq = 0;
 405
 406         list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
 407                 if (cur_elem->seq < min_seq) {
 408                         if (seq_putting > cur_elem->seq) {
 409                                 /*
 410                                  * blocker with lower sequence number exists, we
 411                                  * cannot remove anything from the log
 412                                  */
 413                                 spin_unlock(&fs_info->tree_mod_seq_lock);
 414                                 return;
 415                         }
 416                         min_seq = cur_elem->seq;
 417                 }
 418         }
 419         spin_unlock(&fs_info->tree_mod_seq_lock);
 420
 421         /*
 422          * anything that's lower than the lowest existing (read: blocked)
 423          * sequence number can be removed from the tree.
 424          */
 425         tree_mod_log_write_lock(fs_info);
 426         tm_root = &fs_info->tree_mod_log;
 427         for (node = rb_first(tm_root); node; node = next) {
 428                 next = rb_next(node);
 429                 tm = rb_entry(node, struct tree_mod_elem, node);
 430                 if (tm->seq > min_seq)
 431                         continue;
 432                 rb_erase(node, tm_root);
 433                 kfree(tm);
 434         }
 435         tree_mod_log_write_unlock(fs_info);
 436 }
 437
 438 /*
 439  * key order of the log:
 440  *       node/leaf start address -> sequence
 441  *
 442  * The 'start address' is the logical address of the *new* root node
 443  * for root replace operations, or the logical address of the affected
 444  * block for all other operations.
 445  *
 446  * Note: must be called with write lock (tree_mod_log_write_lock).
 447  */
 448 static noinline int
 449 __tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
 450 {
 451         struct rb_root *tm_root;
 452         struct rb_node **new;
 453         struct rb_node *parent = NULL;
 454         struct tree_mod_elem *cur;
 455
 456         tm->seq = btrfs_inc_tree_mod_seq(fs_info);
 457
 458         tm_root = &fs_info->tree_mod_log;
 459         new = &tm_root->rb_node;
 460         while (*new) {
 461                 cur = rb_entry(*new, struct tree_mod_elem, node);
 462                 parent = *new;
 463                 if (cur->logical < tm->logical)
 464                         new = &((*new)->rb_left);
 465                 else if (cur->logical > tm->logical)
 466                         new = &((*new)->rb_right);
 467                 else if (cur->seq < tm->seq)
 468                         new = &((*new)->rb_left);
 469                 else if (cur->seq > tm->seq)
 470                         new = &((*new)->rb_right);
 471                 else
 472                         return -EEXIST;
 473         }
 474
 475         rb_link_node(&tm->node, parent, new);
 476         rb_insert_color(&tm->node, tm_root);
 477         return 0;
 478 }
 479
 480 /*
 481  * Determines if logging can be omitted. Returns 1 if it can. Otherwise, it
 482  * returns zero with the tree_mod_log_lock acquired. The caller must hold
 483  * this until all tree mod log insertions are recorded in the rb tree and then
 484  * call tree_mod_log_write_unlock() to release.
 485  */
 486 static inline int tree_mod_dont_log(struct btrfs_fs_info *fs_info,
 487                                     struct extent_buffer *eb) {
 488         smp_mb();
 489         if (list_empty(&(fs_info)->tree_mod_seq_list))
 490                 return 1;
 491         if (eb && btrfs_header_level(eb) == 0)
 492                 return 1;
 493
 494         tree_mod_log_write_lock(fs_info);
 495         if (list_empty(&(fs_info)->tree_mod_seq_list)) {
 496                 tree_mod_log_write_unlock(fs_info);
 497                 return 1;
 498         }
 499
 500         return 0;
 501 }
 502
 503 /* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
 504 static inline int tree_mod_need_log(const struct btrfs_fs_info *fs_info,
 505                                     struct extent_buffer *eb)
 506 {
 507         smp_mb();
 508         if (list_empty(&(fs_info)->tree_mod_seq_list))
 509                 return 0;
 510         if (eb && btrfs_header_level(eb) == 0)
 511                 return 0;
 512
 513         return 1;
 514 }
 515
 516 static struct tree_mod_elem *
 517 alloc_tree_mod_elem(struct extent_buffer *eb, int slot,
 518                     enum mod_log_op op, gfp_t flags)
 519 {
 520         struct tree_mod_elem *tm;
 521
 522         tm = kzalloc(sizeof(*tm), flags);
 523         if (!tm)
 524                 return NULL;
 525
 526         tm->logical = eb->start;
 527         if (op != MOD_LOG_KEY_ADD) {
 528                 btrfs_node_key(eb, &tm->key, slot);
 529                 tm->blockptr = btrfs_node_blockptr(eb, slot);
 530         }
 531         tm->op = op;
 532         tm->slot = slot;
 533         tm->generation = btrfs_node_ptr_generation(eb, slot);
 534         RB_CLEAR_NODE(&tm->node);
 535
 536         return tm;
 537 }
 538
 539 static noinline int
 540 tree_mod_log_insert_key(struct btrfs_fs_info *fs_info,
 541                         struct extent_buffer *eb, int slot,
 542                         enum mod_log_op op, gfp_t flags)
 543 {
 544         struct tree_mod_elem *tm;
 545         int ret;
 546
 547         if (!tree_mod_need_log(fs_info, eb))
 548                 return 0;
 549
 550         tm = alloc_tree_mod_elem(eb, slot, op, flags);
 551         if (!tm)
 552                 return -ENOMEM;
 553
 554         if (tree_mod_dont_log(fs_info, eb)) {
 555                 kfree(tm);
 556                 return 0;
 557         }
 558
 559         ret = __tree_mod_log_insert(fs_info, tm);
 560         tree_mod_log_write_unlock(fs_info);
 561         if (ret)
 562                 kfree(tm);
 563
 564         return ret;
 565 }
 566
 567 static noinline int
 568 tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
 569                          struct extent_buffer *eb, int dst_slot, int src_slot,
 570                          int nr_items)
 571 {
 572         struct tree_mod_elem *tm = NULL;
 573         struct tree_mod_elem **tm_list = NULL;
 574         int ret = 0;
 575         int i;
 576         int locked = 0;
 577
 578         if (!tree_mod_need_log(fs_info, eb))
 579                 return 0;
 580
 581         tm_list = kcalloc(nr_items, sizeof(struct tree_mod_elem *), GFP_NOFS);
 582         if (!tm_list)
 583                 return -ENOMEM;
 584
 585         tm = kzalloc(sizeof(*tm), GFP_NOFS);
 586         if (!tm) {
 587                 ret = -ENOMEM;
 588                 goto free_tms;
 589         }
 590
 591         tm->logical = eb->start;
 592         tm->slot = src_slot;
 593         tm->move.dst_slot = dst_slot;
 594         tm->move.nr_items = nr_items;
 595         tm->op = MOD_LOG_MOVE_KEYS;
 596
 597         for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
 598                 tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
 599                     MOD_LOG_KEY_REMOVE_WHILE_MOVING, GFP_NOFS);
 600                 if (!tm_list[i]) {
 601                         ret = -ENOMEM;
 602                         goto free_tms;
 603                 }
 604         }
 605
 606         if (tree_mod_dont_log(fs_info, eb))
 607                 goto free_tms;
 608         locked = 1;
 609
 610         /*
 611          * When we override something during the move, we log these removals.
 612          * This can only happen when we move towards the beginning of the
 613          * buffer, i.e. dst_slot < src_slot.
 614          */
 615         for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
 616                 ret = __tree_mod_log_insert(fs_info, tm_list[i]);
 617                 if (ret)
 618                         goto free_tms;
 619         }
 620
 621         ret = __tree_mod_log_insert(fs_info, tm);
 622         if (ret)
 623                 goto free_tms;
 624         tree_mod_log_write_unlock(fs_info);
 625         kfree(tm_list);
 626
 627         return 0;
 628 free_tms:
 629         for (i = 0; i < nr_items; i++) {
 630                 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
 631                         rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
 632                 kfree(tm_list[i]);
 633         }
 634         if (locked)
 635                 tree_mod_log_write_unlock(fs_info);
 636         kfree(tm_list);
 637         kfree(tm);
 638
 639         return ret;
 640 }
 641
 642 static inline int
 643 __tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
 644                        struct tree_mod_elem **tm_list,
 645                        int nritems)
 646 {
 647         int i, j;
 648         int ret;
 649
 650         for (i = nritems - 1; i >= 0; i--) {
 651                 ret = __tree_mod_log_insert(fs_info, tm_list[i]);
 652                 if (ret) {
 653                         for (j = nritems - 1; j > i; j--)
 654                                 rb_erase(&tm_list[j]->node,
 655                                          &fs_info->tree_mod_log);
 656                         return ret;
 657                 }
 658         }
 659
 660         return 0;
 661 }
 662
 663 static noinline int
 664 tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
 665                          struct extent_buffer *old_root,
 666                          struct extent_buffer *new_root,
 667                          int log_removal)
 668 {
 669         struct tree_mod_elem *tm = NULL;
 670         struct tree_mod_elem **tm_list = NULL;
 671         int nritems = 0;
 672         int ret = 0;
 673         int i;
 674
 675         if (!tree_mod_need_log(fs_info, NULL))
 676                 return 0;
 677
 678         if (log_removal && btrfs_header_level(old_root) > 0) {
 679                 nritems = btrfs_header_nritems(old_root);
 680                 tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *),
 681                                   GFP_NOFS);
 682                 if (!tm_list) {
 683                         ret = -ENOMEM;
 684                         goto free_tms;
 685                 }
 686                 for (i = 0; i < nritems; i++) {
 687                         tm_list[i] = alloc_tree_mod_elem(old_root, i,
 688                             MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
 689                         if (!tm_list[i]) {
 690                                 ret = -ENOMEM;
 691                                 goto free_tms;
 692                         }
 693                 }
 694         }
 695
 696         tm = kzalloc(sizeof(*tm), GFP_NOFS);
 697         if (!tm) {
 698                 ret = -ENOMEM;
 699                 goto free_tms;
 700         }
 701
 702         tm->logical = new_root->start;
 703         tm->old_root.logical = old_root->start;
 704         tm->old_root.level = btrfs_header_level(old_root);
 705         tm->generation = btrfs_header_generation(old_root);
 706         tm->op = MOD_LOG_ROOT_REPLACE;
 707
 708         if (tree_mod_dont_log(fs_info, NULL))
 709                 goto free_tms;
 710
 711         if (tm_list)
 712                 ret = __tree_mod_log_free_eb(fs_info, tm_list, nritems);
 713         if (!ret)
 714                 ret = __tree_mod_log_insert(fs_info, tm);
 715
 716         tree_mod_log_write_unlock(fs_info);
 717         if (ret)
 718                 goto free_tms;
 719         kfree(tm_list);
 720
 721         return ret;
 722
 723 free_tms:
 724         if (tm_list) {
 725                 for (i = 0; i < nritems; i++)
 726                         kfree(tm_list[i]);
 727                 kfree(tm_list);
 728         }
 729         kfree(tm);
 730
 731         return ret;
 732 }
 733
 734 static struct tree_mod_elem *
 735 __tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
 736                       int smallest)
 737 {
 738         struct rb_root *tm_root;
 739         struct rb_node *node;
 740         struct tree_mod_elem *cur = NULL;
 741         struct tree_mod_elem *found = NULL;
 742
 743         tree_mod_log_read_lock(fs_info);
 744         tm_root = &fs_info->tree_mod_log;
 745         node = tm_root->rb_node;
 746         while (node) {
 747                 cur = rb_entry(node, struct tree_mod_elem, node);
 748                 if (cur->logical < start) {
 749                         node = node->rb_left;
 750                 } else if (cur->logical > start) {
 751                         node = node->rb_right;
 752                 } else if (cur->seq < min_seq) {
 753                         node = node->rb_left;
 754                 } else if (!smallest) {
 755                         /* we want the node with the highest seq */
 756                         if (found)
 757                                 BUG_ON(found->seq > cur->seq);
 758                         found = cur;
 759                         node = node->rb_left;
 760                 } else if (cur->seq > min_seq) {
 761                         /* we want the node with the smallest seq */
 762                         if (found)
 763                                 BUG_ON(found->seq < cur->seq);
 764                         found = cur;
 765                         node = node->rb_right;
 766                 } else {
 767                         found = cur;
 768                         break;
 769                 }
 770         }
 771         tree_mod_log_read_unlock(fs_info);
 772
 773         return found;
 774 }
 775
 776 /*
 777  * this returns the element from the log with the smallest time sequence
 778  * value that's in the log (the oldest log item). any element with a time
 779  * sequence lower than min_seq will be ignored.
 780  */
 781 static struct tree_mod_elem *
 782 tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info, u64 start,
 783                            u64 min_seq)
 784 {
 785         return __tree_mod_log_search(fs_info, start, min_seq, 1);
 786 }
 787
 788 /*
 789  * this returns the element from the log with the largest time sequence
 790  * value that's in the log (the most recent log item). any element with
 791  * a time sequence lower than min_seq will be ignored.
 792  */
 793 static struct tree_mod_elem *
 794 tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq)
 795 {
 796         return __tree_mod_log_search(fs_info, start, min_seq, 0);
 797 }
 798
 799 static noinline int
 800 tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
 801                      struct extent_buffer *src, unsigned long dst_offset,
 802                      unsigned long src_offset, int nr_items)
 803 {
 804         int ret = 0;
 805         struct tree_mod_elem **tm_list = NULL;
 806         struct tree_mod_elem **tm_list_add, **tm_list_rem;
 807         int i;
 808         int locked = 0;
 809
 810         if (!tree_mod_need_log(fs_info, NULL))
 811                 return 0;
 812
 813         if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
 814                 return 0;
 815
 816         tm_list = kcalloc(nr_items * 2, sizeof(struct tree_mod_elem *),
 817                           GFP_NOFS);
 818         if (!tm_list)
 819                 return -ENOMEM;
 820
 821         tm_list_add = tm_list;
 822         tm_list_rem = tm_list + nr_items;
 823         for (i = 0; i < nr_items; i++) {
 824                 tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
 825                     MOD_LOG_KEY_REMOVE, GFP_NOFS);
 826                 if (!tm_list_rem[i]) {
 827                         ret = -ENOMEM;
 828                         goto free_tms;
 829                 }
 830
 831                 tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
 832                     MOD_LOG_KEY_ADD, GFP_NOFS);
 833                 if (!tm_list_add[i]) {
 834                         ret = -ENOMEM;
 835                         goto free_tms;
 836                 }
 837         }
 838
 839         if (tree_mod_dont_log(fs_info, NULL))
 840                 goto free_tms;
 841         locked = 1;
 842
 843         for (i = 0; i < nr_items; i++) {
 844                 ret = __tree_mod_log_insert(fs_info, tm_list_rem[i]);
 845                 if (ret)
 846                         goto free_tms;
 847                 ret = __tree_mod_log_insert(fs_info, tm_list_add[i]);
 848                 if (ret)
 849                         goto free_tms;
 850         }
 851
 852         tree_mod_log_write_unlock(fs_info);
 853         kfree(tm_list);
 854
 855         return 0;
 856
 857 free_tms:
 858         for (i = 0; i < nr_items * 2; i++) {
 859                 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
 860                         rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
 861                 kfree(tm_list[i]);
 862         }
 863         if (locked)
 864                 tree_mod_log_write_unlock(fs_info);
 865         kfree(tm_list);
 866
 867         return ret;
 868 }
 869
 870 static inline void
 871 tree_mod_log_eb_move(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
 872                      int dst_offset, int src_offset, int nr_items)
 873 {
 874         int ret;
 875         ret = tree_mod_log_insert_move(fs_info, dst, dst_offset, src_offset,
 876                                        nr_items);
 877         BUG_ON(ret < 0);
 878 }
 879
 880 static noinline void
 881 tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
 882                           struct extent_buffer *eb, int slot, int atomic)
 883 {
 884         int ret;
 885
 886         ret = tree_mod_log_insert_key(fs_info, eb, slot,
 887                                         MOD_LOG_KEY_REPLACE,
 888                                         atomic ? GFP_ATOMIC : GFP_NOFS);
 889         BUG_ON(ret < 0);
 890 }
 891
 892 static noinline int
 893 tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
 894 {
 895         struct tree_mod_elem **tm_list = NULL;
 896         int nritems = 0;
 897         int i;
 898         int ret = 0;
 899
 900         if (btrfs_header_level(eb) == 0)
 901                 return 0;
 902
 903         if (!tree_mod_need_log(fs_info, NULL))
 904                 return 0;
 905
 906         nritems = btrfs_header_nritems(eb);
 907         tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), GFP_NOFS);
 908         if (!tm_list)
 909                 return -ENOMEM;
 910
 911         for (i = 0; i < nritems; i++) {
 912                 tm_list[i] = alloc_tree_mod_elem(eb, i,
 913                     MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
 914                 if (!tm_list[i]) {
 915                         ret = -ENOMEM;
 916                         goto free_tms;
 917                 }
 918         }
 919
 920         if (tree_mod_dont_log(fs_info, eb))
 921                 goto free_tms;
 922
 923         ret = __tree_mod_log_free_eb(fs_info, tm_list, nritems);
 924         tree_mod_log_write_unlock(fs_info);
 925         if (ret)
 926                 goto free_tms;
 927         kfree(tm_list);
 928
 929         return 0;
 930
 931 free_tms:
 932         for (i = 0; i < nritems; i++)
 933                 kfree(tm_list[i]);
 934         kfree(tm_list);
 935
 936         return ret;
 937 }
 938
 939 static noinline void
 940 tree_mod_log_set_root_pointer(struct btrfs_root *root,
 941                               struct extent_buffer *new_root_node,
 942                               int log_removal)
 943 {
 944         int ret;
 945         ret = tree_mod_log_insert_root(root->fs_info, root->node,
 946                                        new_root_node, log_removal);
 947         BUG_ON(ret < 0);
 948 }
 949
 950 /*
 951  * check if the tree block can be shared by multiple trees
 952  */
 953 int btrfs_block_can_be_shared(struct btrfs_root *root,
 954                               struct extent_buffer *buf)
 955 {
 956         /*
 957          * Tree blocks not in reference counted trees and tree roots
 958          * are never shared. If a block was allocated after the last
 959          * snapshot and the block was not allocated by tree relocation,
 960          * we know the block is not shared.
 961          */
 962         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 963             buf != root->node && buf != root->commit_root &&
 964             (btrfs_header_generation(buf) <=
 965              btrfs_root_last_snapshot(&root->root_item) ||
 966              btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)))
 967                 return 1;
 968 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 969         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 970             btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
 971                 return 1;
 972 #endif
 973         return 0;
 974 }
 975
 976 static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 977                                        struct btrfs_root *root,
 978                                        struct extent_buffer *buf,
 979                                        struct extent_buffer *cow,
 980                                        int *last_ref)
 981 {
 982         struct btrfs_fs_info *fs_info = root->fs_info;
 983         u64 refs;
 984         u64 owner;
 985         u64 flags;
 986         u64 new_flags = 0;
 987         int ret;
 988
 989         /*
 990          * Backrefs update rules:
 991          *
 992          * Always use full backrefs for extent pointers in tree block
 993          * allocated by tree relocation.
 994          *
 995          * If a shared tree block is no longer referenced by its owner
 996          * tree (btrfs_header_owner(buf) == root->root_key.objectid),
 997          * use full backrefs for extent pointers in tree block.
 998          *
 999          * If a tree block is been relocating
1000          * (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID),
1001          * use full backrefs for extent pointers in tree block.
1002          * The reason for this is some operations (such as drop tree)
1003          * are only allowed for blocks use full backrefs.
1004          */
1005
1006         if (btrfs_block_can_be_shared(root, buf)) {
1007                 ret = btrfs_lookup_extent_info(trans, fs_info, buf->start,
1008                                                btrfs_header_level(buf), 1,
1009                                                &refs, &flags);
1010                 if (ret)
1011                         return ret;
1012                 if (refs == 0) {
1013                         ret = -EROFS;
1014                         btrfs_handle_fs_error(fs_info, ret, NULL);
1015                         return ret;
1016                 }
1017         } else {
1018                 refs = 1;
1019                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
1020                     btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
1021                         flags = BTRFS_BLOCK_FLAG_FULL_BACKREF;
1022                 else
1023                         flags = 0;
1024         }
1025
1026         owner = btrfs_header_owner(buf);
1027         BUG_ON(owner == BTRFS_TREE_RELOC_OBJECTID &&
1028                !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));
1029
1030         if (refs > 1) {
1031                 if ((owner == root->root_key.objectid ||
1032                      root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) &&
1033                     !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)) {
1034                         ret = btrfs_inc_ref(trans, root, buf, 1);
1035                         if (ret)
1036                                 return ret;
1037
1038                         if (root->root_key.objectid ==
1039                             BTRFS_TREE_RELOC_OBJECTID) {
1040                                 ret = btrfs_dec_ref(trans, root, buf, 0);
1041                                 if (ret)
1042                                         return ret;
1043                                 ret = btrfs_inc_ref(trans, root, cow, 1);
1044                                 if (ret)
1045                                         return ret;
1046                         }
1047                         new_flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
1048                 } else {
1049
1050                         if (root->root_key.objectid ==
1051                             BTRFS_TREE_RELOC_OBJECTID)
1052                                 ret = btrfs_inc_ref(trans, root, cow, 1);
1053                         else
1054                                 ret = btrfs_inc_ref(trans, root, cow, 0);
1055                         if (ret)
1056                                 return ret;
1057                 }
1058                 if (new_flags != 0) {
1059                         int level = btrfs_header_level(buf);
1060
1061                         ret = btrfs_set_disk_extent_flags(trans, fs_info,
1062                                                           buf->start,
1063                                                           buf->len,
1064                                                           new_flags, level, 0);
1065                         if (ret)
1066                                 return ret;
1067                 }
1068         } else {
1069                 if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
1070                         if (root->root_key.objectid ==
1071                             BTRFS_TREE_RELOC_OBJECTID)
1072                                 ret = btrfs_inc_ref(trans, root, cow, 1);
1073                         else
1074                                 ret = btrfs_inc_ref(trans, root, cow, 0);
1075                         if (ret)
1076                                 return ret;
1077                         ret = btrfs_dec_ref(trans, root, buf, 1);
1078                         if (ret)
1079                                 return ret;
1080                 }
1081                 clean_tree_block(fs_info, buf);
1082                 *last_ref = 1;
1083         }
1084         return 0;
1085 }
1086
1087 /*
1088  * does the dirty work in cow of a single block.  The parent block (if
1089  * supplied) is updated to point to the new cow copy.  The new buffer is marked
1090  * dirty and returned locked.  If you modify the block it needs to be marked
1091  * dirty again.
1092  *
1093  * search_start -- an allocation hint for the new block
1094  *
1095  * empty_size -- a hint that you plan on doing more cow.  This is the size in
1096  * bytes the allocator should try to find free next to the block it returns.
1097  * This is just a hint and may be ignored by the allocator.
1098  */
1099 static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
1100                              struct btrfs_root *root,
1101                              struct extent_buffer *buf,
1102                              struct extent_buffer *parent, int parent_slot,
1103                              struct extent_buffer **cow_ret,
1104                              u64 search_start, u64 empty_size)
1105 {
1106         struct btrfs_fs_info *fs_info = root->fs_info;
1107         struct btrfs_disk_key disk_key;
1108         struct extent_buffer *cow;
1109         int level, ret;
1110         int last_ref = 0;
1111         int unlock_orig = 0;
1112         u64 parent_start = 0;
1113
1114         if (*cow_ret == buf)
1115                 unlock_orig = 1;
1116
1117         btrfs_assert_tree_locked(buf);
1118
1119         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1120                 trans->transid != fs_info->running_transaction->transid);
1121         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1122                 trans->transid != root->last_trans);
1123
1124         level = btrfs_header_level(buf);
1125
1126         if (level == 0)
1127                 btrfs_item_key(buf, &disk_key, 0);
1128         else
1129                 btrfs_node_key(buf, &disk_key, 0);
1130
1131         if ((root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) && parent)
1132                 parent_start = parent->start;
1133
1134         cow = btrfs_alloc_tree_block(trans, root, parent_start,
1135                         root->root_key.objectid, &disk_key, level,
1136                         search_start, empty_size);
1137         if (IS_ERR(cow))
1138                 return PTR_ERR(cow);
1139
1140         /* cow is set to blocking by btrfs_init_new_buffer */
1141
1142         copy_extent_buffer_full(cow, buf);
1143         btrfs_set_header_bytenr(cow, cow->start);
1144         btrfs_set_header_generation(cow, trans->transid);
1145         btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
1146         btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
1147                                      BTRFS_HEADER_FLAG_RELOC);
1148         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1149                 btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
1150         else
1151                 btrfs_set_header_owner(cow, root->root_key.objectid);
1152
1153         write_extent_buffer_fsid(cow, fs_info->fsid);
1154
1155         ret = update_ref_for_cow(trans, root, buf, cow, &last_ref);
1156         if (ret) {
1157                 btrfs_abort_transaction(trans, ret);
1158                 return ret;
1159         }
1160
1161         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
1162                 ret = btrfs_reloc_cow_block(trans, root, buf, cow);
1163                 if (ret) {
1164                         btrfs_abort_transaction(trans, ret);
1165                         return ret;
1166                 }
1167         }
1168
1169         if (buf == root->node) {
1170                 WARN_ON(parent && parent != buf);
1171                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
1172                     btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
1173                         parent_start = buf->start;
1174
1175                 extent_buffer_get(cow);
1176                 tree_mod_log_set_root_pointer(root, cow, 1);
1177                 rcu_assign_pointer(root->node, cow);
1178
1179                 btrfs_free_tree_block(trans, root, buf, parent_start,
1180                                       last_ref);
1181                 free_extent_buffer(buf);
1182                 add_root_to_dirty_list(root);
1183         } else {
1184                 WARN_ON(trans->transid != btrfs_header_generation(parent));
1185                 tree_mod_log_insert_key(fs_info, parent, parent_slot,
1186                                         MOD_LOG_KEY_REPLACE, GFP_NOFS);
1187                 btrfs_set_node_blockptr(parent, parent_slot,
1188                                         cow->start);
1189                 btrfs_set_node_ptr_generation(parent, parent_slot,
1190                                               trans->transid);
1191                 btrfs_mark_buffer_dirty(parent);
1192                 if (last_ref) {
1193                         ret = tree_mod_log_free_eb(fs_info, buf);
1194                         if (ret) {
1195                                 btrfs_abort_transaction(trans, ret);
1196                                 return ret;
1197                         }
1198                 }
1199                 btrfs_free_tree_block(trans, root, buf, parent_start,
1200                                       last_ref);
1201         }
1202         if (unlock_orig)
1203                 btrfs_tree_unlock(buf);
1204         free_extent_buffer_stale(buf);
1205         btrfs_mark_buffer_dirty(cow);
1206         *cow_ret = cow;
1207         return 0;
1208 }
1209
1210 /*
1211  * returns the logical address of the oldest predecessor of the given root.
1212  * entries older than time_seq are ignored.
1213  */
1214 static struct tree_mod_elem *
1215 __tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
1216                            struct extent_buffer *eb_root, u64 time_seq)
1217 {
1218         struct tree_mod_elem *tm;
1219         struct tree_mod_elem *found = NULL;
1220         u64 root_logical = eb_root->start;
1221         int looped = 0;
1222
1223         if (!time_seq)
1224                 return NULL;
1225
1226         /*
1227          * the very last operation that's logged for a root is the
1228          * replacement operation (if it is replaced at all). this has
1229          * the logical address of the *new* root, making it the very
1230          * first operation that's logged for this root.
1231          */
1232         while (1) {
1233                 tm = tree_mod_log_search_oldest(fs_info, root_logical,
1234                                                 time_seq);
1235                 if (!looped && !tm)
1236                         return NULL;
1237                 /*
1238                  * if there are no tree operation for the oldest root, we simply
1239                  * return it. this should only happen if that (old) root is at
1240                  * level 0.
1241                  */
1242                 if (!tm)
1243                         break;
1244
1245                 /*
1246                  * if there's an operation that's not a root replacement, we
1247                  * found the oldest version of our root. normally, we'll find a
1248                  * MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
1249                  */
1250                 if (tm->op != MOD_LOG_ROOT_REPLACE)
1251                         break;
1252
1253                 found = tm;
1254                 root_logical = tm->old_root.logical;
1255                 looped = 1;
1256         }
1257
1258         /* if there's no old root to return, return what we found instead */
1259         if (!found)
1260                 found = tm;
1261
1262         return found;
1263 }
1264
1265 /*
1266  * tm is a pointer to the first operation to rewind within eb. then, all
1267  * previous operations will be rewound (until we reach something older than
1268  * time_seq).
1269  */
1270 static void
1271 __tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
1272                       u64 time_seq, struct tree_mod_elem *first_tm)
1273 {
1274         u32 n;
1275         struct rb_node *next;
1276         struct tree_mod_elem *tm = first_tm;
1277         unsigned long o_dst;
1278         unsigned long o_src;
1279         unsigned long p_size = sizeof(struct btrfs_key_ptr);
1280
1281         n = btrfs_header_nritems(eb);
1282         tree_mod_log_read_lock(fs_info);
1283         while (tm && tm->seq >= time_seq) {
1284                 /*
1285                  * all the operations are recorded with the operator used for
1286                  * the modification. as we're going backwards, we do the
1287                  * opposite of each operation here.
1288                  */
1289                 switch (tm->op) {
1290                 case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
1291                         BUG_ON(tm->slot < n);
1292                         /* Fallthrough */
1293                 case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
1294                 case MOD_LOG_KEY_REMOVE:
1295                         btrfs_set_node_key(eb, &tm->key, tm->slot);
1296                         btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1297                         btrfs_set_node_ptr_generation(eb, tm->slot,
1298                                                       tm->generation);
1299                         n++;
1300                         break;
1301                 case MOD_LOG_KEY_REPLACE:
1302                         BUG_ON(tm->slot >= n);
1303                         btrfs_set_node_key(eb, &tm->key, tm->slot);
1304                         btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1305                         btrfs_set_node_ptr_generation(eb, tm->slot,
1306                                                       tm->generation);
1307                         break;
1308                 case MOD_LOG_KEY_ADD:
1309                         /* if a move operation is needed it's in the log */
1310                         n--;
1311                         break;
1312                 case MOD_LOG_MOVE_KEYS:
1313                         o_dst = btrfs_node_key_ptr_offset(tm->slot);
1314                         o_src = btrfs_node_key_ptr_offset(tm->move.dst_slot);
1315                         memmove_extent_buffer(eb, o_dst, o_src,
1316                                               tm->move.nr_items * p_size);
1317                         break;
1318                 case MOD_LOG_ROOT_REPLACE:
1319                         /*
1320                          * this operation is special. for roots, this must be
1321                          * handled explicitly before rewinding.
1322                          * for non-roots, this operation may exist if the node
1323                          * was a root: root A -> child B; then A gets empty and
1324                          * B is promoted to the new root. in the mod log, we'll
1325                          * have a root-replace operation for B, a tree block
1326                          * that is no root. we simply ignore that operation.
1327                          */
1328                         break;
1329                 }
1330                 next = rb_next(&tm->node);
1331                 if (!next)
1332                         break;
1333                 tm = rb_entry(next, struct tree_mod_elem, node);
1334                 if (tm->logical != first_tm->logical)
1335                         break;
1336         }
1337         tree_mod_log_read_unlock(fs_info);
1338         btrfs_set_header_nritems(eb, n);
1339 }
1340
1341 /*
1342  * Called with eb read locked. If the buffer cannot be rewound, the same buffer
1343  * is returned. If rewind operations happen, a fresh buffer is returned. The
1344  * returned buffer is always read-locked. If the returned buffer is not the
1345  * input buffer, the lock on the input buffer is released and the input buffer
1346  * is freed (its refcount is decremented).
1347  */
1348 static struct extent_buffer *
1349 tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
1350                     struct extent_buffer *eb, u64 time_seq)
1351 {
1352         struct extent_buffer *eb_rewin;
1353         struct tree_mod_elem *tm;
1354
1355         if (!time_seq)
1356                 return eb;
1357
1358         if (btrfs_header_level(eb) == 0)
1359                 return eb;
1360
1361         tm = tree_mod_log_search(fs_info, eb->start, time_seq);
1362         if (!tm)
1363                 return eb;
1364
1365         btrfs_set_path_blocking(path);
1366         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1367
1368         if (tm->op == MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1369                 BUG_ON(tm->slot != 0);
1370                 eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
1371                 if (!eb_rewin) {
1372                         btrfs_tree_read_unlock_blocking(eb);
1373                         free_extent_buffer(eb);
1374                         return NULL;
1375                 }
1376                 btrfs_set_header_bytenr(eb_rewin, eb->start);
1377                 btrfs_set_header_backref_rev(eb_rewin,
1378                                              btrfs_header_backref_rev(eb));
1379                 btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
1380                 btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
1381         } else {
1382                 eb_rewin = btrfs_clone_extent_buffer(eb);
1383                 if (!eb_rewin) {
1384                         btrfs_tree_read_unlock_blocking(eb);
1385                         free_extent_buffer(eb);
1386                         return NULL;
1387                 }
1388         }
1389
1390         btrfs_clear_path_blocking(path, NULL, BTRFS_READ_LOCK);
1391         btrfs_tree_read_unlock_blocking(eb);
1392         free_extent_buffer(eb);
1393
1394         extent_buffer_get(eb_rewin);
1395         btrfs_tree_read_lock(eb_rewin);
1396         __tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
1397         WARN_ON(btrfs_header_nritems(eb_rewin) >
1398                 BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1399
1400         return eb_rewin;
1401 }
1402
1403 /*
1404  * get_old_root() rewinds the state of @root's root node to the given @time_seq
1405  * value. If there are no changes, the current root->root_node is returned. If
1406  * anything changed in between, there's a fresh buffer allocated on which the
1407  * rewind operations are done. In any case, the returned buffer is read locked.
1408  * Returns NULL on error (with no locks held).
1409  */
1410 static inline struct extent_buffer *
1411 get_old_root(struct btrfs_root *root, u64 time_seq)
1412 {
1413         struct btrfs_fs_info *fs_info = root->fs_info;
1414         struct tree_mod_elem *tm;
1415         struct extent_buffer *eb = NULL;
1416         struct extent_buffer *eb_root;
1417         struct extent_buffer *old;
1418         struct tree_mod_root *old_root = NULL;
1419         u64 old_generation = 0;
1420         u64 logical;
1421
1422         eb_root = btrfs_read_lock_root_node(root);
1423         tm = __tree_mod_log_oldest_root(fs_info, eb_root, time_seq);
1424         if (!tm)
1425                 return eb_root;
1426
1427         if (tm->op == MOD_LOG_ROOT_REPLACE) {
1428                 old_root = &tm->old_root;
1429                 old_generation = tm->generation;
1430                 logical = old_root->logical;
1431         } else {
1432                 logical = eb_root->start;
1433         }
1434
1435         tm = tree_mod_log_search(fs_info, logical, time_seq);
1436         if (old_root && tm && tm->op != MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1437                 btrfs_tree_read_unlock(eb_root);
1438                 free_extent_buffer(eb_root);
1439                 old = read_tree_block(fs_info, logical, 0);
1440                 if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) {
1441                         if (!IS_ERR(old))
1442                                 free_extent_buffer(old);
1443                         btrfs_warn(fs_info,
1444                                    "failed to read tree block %llu from get_old_root",
1445                                    logical);
1446                 } else {
1447                         eb = btrfs_clone_extent_buffer(old);
1448                         free_extent_buffer(old);
1449                 }
1450         } else if (old_root) {
1451                 btrfs_tree_read_unlock(eb_root);
1452                 free_extent_buffer(eb_root);
1453                 eb = alloc_dummy_extent_buffer(fs_info, logical);
1454         } else {
1455                 btrfs_set_lock_blocking_rw(eb_root, BTRFS_READ_LOCK);
1456                 eb = btrfs_clone_extent_buffer(eb_root);
1457                 btrfs_tree_read_unlock_blocking(eb_root);
1458                 free_extent_buffer(eb_root);
1459         }
1460
1461         if (!eb)
1462                 return NULL;
1463         extent_buffer_get(eb);
1464         btrfs_tree_read_lock(eb);
1465         if (old_root) {
1466                 btrfs_set_header_bytenr(eb, eb->start);
1467                 btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
1468                 btrfs_set_header_owner(eb, btrfs_header_owner(eb_root));
1469                 btrfs_set_header_level(eb, old_root->level);
1470                 btrfs_set_header_generation(eb, old_generation);
1471         }
1472         if (tm)
1473                 __tree_mod_log_rewind(fs_info, eb, time_seq, tm);
1474         else
1475                 WARN_ON(btrfs_header_level(eb) != 0);
1476         WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1477
1478         return eb;
1479 }
1480
1481 int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
1482 {
1483         struct tree_mod_elem *tm;
1484         int level;
1485         struct extent_buffer *eb_root = btrfs_root_node(root);
1486
1487         tm = __tree_mod_log_oldest_root(root->fs_info, eb_root, time_seq);
1488         if (tm && tm->op == MOD_LOG_ROOT_REPLACE) {
1489                 level = tm->old_root.level;
1490         } else {
1491                 level = btrfs_header_level(eb_root);
1492         }
1493         free_extent_buffer(eb_root);
1494
1495         return level;
1496 }
1497
1498 static inline int should_cow_block(struct btrfs_trans_handle *trans,
1499                                    struct btrfs_root *root,
1500                                    struct extent_buffer *buf)
1501 {
1502         if (btrfs_is_testing(root->fs_info))
1503                 return 0;
1504
1505         /* ensure we can see the force_cow */
1506         smp_rmb();
1507
1508         /*
1509          * We do not need to cow a block if
1510          * 1) this block is not created or changed in this transaction;
1511          * 2) this block does not belong to TREE_RELOC tree;
1512          * 3) the root is not forced COW.
1513          *
1514          * What is forced COW:
1515          *    when we create snapshot during committing the transaction,
1516          *    after we've finished coping src root, we must COW the shared
1517          *    block to ensure the metadata consistency.
1518          */
1519         if (btrfs_header_generation(buf) == trans->transid &&
1520             !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) &&
1521             !(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
1522               btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)) &&
1523             !test_bit(BTRFS_ROOT_FORCE_COW, &root->state))
1524                 return 0;
1525         return 1;
1526 }
1527
1528 /*
1529  * cows a single block, see __btrfs_cow_block for the real work.
1530  * This version of it has extra checks so that a block isn't COWed more than
1531  * once per transaction, as long as it hasn't been written yet
1532  */
1533 noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
1534                     struct btrfs_root *root, struct extent_buffer *buf,
1535                     struct extent_buffer *parent, int parent_slot,
1536                     struct extent_buffer **cow_ret)
1537 {
1538         struct btrfs_fs_info *fs_info = root->fs_info;
1539         u64 search_start;
1540         int ret;
1541
1542         if (trans->transaction != fs_info->running_transaction)
1543                 WARN(1, KERN_CRIT "trans %llu running %llu\n",
1544                        trans->transid,
1545                        fs_info->running_transaction->transid);
1546
1547         if (trans->transid != fs_info->generation)
1548                 WARN(1, KERN_CRIT "trans %llu running %llu\n",
1549                        trans->transid, fs_info->generation);
1550
1551         if (!should_cow_block(trans, root, buf)) {
1552                 trans->dirty = true;
1553                 *cow_ret = buf;
1554                 return 0;
1555         }
1556
1557         search_start = buf->start & ~((u64)SZ_1G - 1);
1558
1559         if (parent)
1560                 btrfs_set_lock_blocking(parent);
1561         btrfs_set_lock_blocking(buf);
1562
1563         ret = __btrfs_cow_block(trans, root, buf, parent,
1564                                  parent_slot, cow_ret, search_start, 0);
1565
1566         trace_btrfs_cow_block(root, buf, *cow_ret);
1567
1568         return ret;
1569 }
1570
1571 /*
1572  * helper function for defrag to decide if two blocks pointed to by a
1573  * node are actually close by
1574  */
1575 static int close_blocks(u64 blocknr, u64 other, u32 blocksize)
1576 {
1577         if (blocknr < other && other - (blocknr + blocksize) < 32768)
1578                 return 1;
1579         if (blocknr > other && blocknr - (other + blocksize) < 32768)
1580                 return 1;
1581         return 0;
1582 }
1583
1584 /*
1585  * compare two keys in a memcmp fashion
1586  */
1587 static int comp_keys(const struct btrfs_disk_key *disk,
1588                      const struct btrfs_key *k2)
1589 {
1590         struct btrfs_key k1;
1591
1592         btrfs_disk_key_to_cpu(&k1, disk);
1593
1594         return btrfs_comp_cpu_keys(&k1, k2);
1595 }
1596
1597 /*
1598  * same as comp_keys only with two btrfs_key's
1599  */
1600 int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2)
1601 {
1602         if (k1->objectid > k2->objectid)
1603                 return 1;
1604         if (k1->objectid < k2->objectid)
1605                 return -1;
1606         if (k1->type > k2->type)
1607                 return 1;
1608         if (k1->type < k2->type)
1609                 return -1;
1610         if (k1->offset > k2->offset)
1611                 return 1;
1612         if (k1->offset < k2->offset)
1613                 return -1;
1614         return 0;
1615 }
1616
1617 /*
1618  * this is used by the defrag code to go through all the
1619  * leaves pointed to by a node and reallocate them so that
1620  * disk order is close to key order
1621  */
1622 int btrfs_realloc_node(struct btrfs_trans_handle *trans,
1623                        struct btrfs_root *root, struct extent_buffer *parent,
1624                        int start_slot, u64 *last_ret,
1625                        struct btrfs_key *progress)
1626 {
1627         struct btrfs_fs_info *fs_info = root->fs_info;
1628         struct extent_buffer *cur;
1629         u64 blocknr;
1630         u64 gen;
1631         u64 search_start = *last_ret;
1632         u64 last_block = 0;
1633         u64 other;
1634         u32 parent_nritems;
1635         int end_slot;
1636         int i;
1637         int err = 0;
1638         int parent_level;
1639         int uptodate;
1640         u32 blocksize;
1641         int progress_passed = 0;
1642         struct btrfs_disk_key disk_key;
1643
1644         parent_level = btrfs_header_level(parent);
1645
1646         WARN_ON(trans->transaction != fs_info->running_transaction);
1647         WARN_ON(trans->transid != fs_info->generation);
1648
1649         parent_nritems = btrfs_header_nritems(parent);
1650         blocksize = fs_info->nodesize;
1651         end_slot = parent_nritems - 1;
1652
1653         if (parent_nritems <= 1)
1654                 return 0;
1655
1656         btrfs_set_lock_blocking(parent);
1657
1658         for (i = start_slot; i <= end_slot; i++) {
1659                 int close = 1;
1660
1661                 btrfs_node_key(parent, &disk_key, i);
1662                 if (!progress_passed && comp_keys(&disk_key, progress) < 0)
1663                         continue;
1664
1665                 progress_passed = 1;
1666                 blocknr = btrfs_node_blockptr(parent, i);
1667                 gen = btrfs_node_ptr_generation(parent, i);
1668                 if (last_block == 0)
1669                         last_block = blocknr;
1670
1671                 if (i > 0) {
1672                         other = btrfs_node_blockptr(parent, i - 1);
1673                         close = close_blocks(blocknr, other, blocksize);
1674                 }
1675                 if (!close && i < end_slot) {
1676                         other = btrfs_node_blockptr(parent, i + 1);
1677                         close = close_blocks(blocknr, other, blocksize);
1678                 }
1679                 if (close) {
1680                         last_block = blocknr;
1681                         continue;
1682                 }
1683
1684                 cur = find_extent_buffer(fs_info, blocknr);
1685                 if (cur)
1686                         uptodate = btrfs_buffer_uptodate(cur, gen, 0);
1687                 else
1688                         uptodate = 0;
1689                 if (!cur || !uptodate) {
1690                         if (!cur) {
1691                                 cur = read_tree_block(fs_info, blocknr, gen);
1692                                 if (IS_ERR(cur)) {
1693                                         return PTR_ERR(cur);
1694                                 } else if (!extent_buffer_uptodate(cur)) {
1695                                         free_extent_buffer(cur);
1696                                         return -EIO;
1697                                 }
1698                         } else if (!uptodate) {
1699                                 err = btrfs_read_buffer(cur, gen);
1700                                 if (err) {
1701                                         free_extent_buffer(cur);
1702                                         return err;
1703                                 }
1704                         }
1705                 }
1706                 if (search_start == 0)
1707                         search_start = last_block;
1708
1709                 btrfs_tree_lock(cur);
1710                 btrfs_set_lock_blocking(cur);
1711                 err = __btrfs_cow_block(trans, root, cur, parent, i,
1712                                         &cur, search_start,
1713                                         min(16 * blocksize,
1714                                             (end_slot - i) * blocksize));
1715                 if (err) {
1716                         btrfs_tree_unlock(cur);
1717                         free_extent_buffer(cur);
1718                         break;
1719                 }
1720                 search_start = cur->start;
1721                 last_block = cur->start;
1722                 *last_ret = search_start;
1723                 btrfs_tree_unlock(cur);
1724                 free_extent_buffer(cur);
1725         }
1726         return err;
1727 }
1728
1729 /*
1730  * search for key in the extent_buffer.  The items start at offset p,
1731  * and they are item_size apart.  There are 'max' items in p.
1732  *
1733  * the slot in the array is returned via slot, and it points to
1734  * the place where you would insert key if it is not found in
1735  * the array.
1736  *
1737  * slot may point to max if the key is bigger than all of the keys
1738  */
1739 static noinline int generic_bin_search(struct extent_buffer *eb,
1740                                        unsigned long p, int item_size,
1741                                        const struct btrfs_key *key,
1742                                        int max, int *slot)
1743 {
1744         int low = 0;
1745         int high = max;
1746         int mid;
1747         int ret;
1748         struct btrfs_disk_key *tmp = NULL;
1749         struct btrfs_disk_key unaligned;
1750         unsigned long offset;
1751         char *kaddr = NULL;
1752         unsigned long map_start = 0;
1753         unsigned long map_len = 0;
1754         int err;
1755
1756         if (low > high) {
1757                 btrfs_err(eb->fs_info,
1758                  "%s: low (%d) > high (%d) eb %llu owner %llu level %d",
1759                           __func__, low, high, eb->start,
1760                           btrfs_header_owner(eb), btrfs_header_level(eb));
1761                 return -EINVAL;
1762         }
1763
1764         while (low < high) {
1765                 mid = (low + high) / 2;
1766                 offset = p + mid * item_size;
1767
1768                 if (!kaddr || offset < map_start ||
1769                     (offset + sizeof(struct btrfs_disk_key)) >
1770                     map_start + map_len) {
1771
1772                         err = map_private_extent_buffer(eb, offset,
1773                                                 sizeof(struct btrfs_disk_key),
1774                                                 &kaddr, &map_start, &map_len);
1775
1776                         if (!err) {
1777                                 tmp = (struct btrfs_disk_key *)(kaddr + offset -
1778                                                         map_start);
1779                         } else if (err == 1) {
1780                                 read_extent_buffer(eb, &unaligned,
1781                                                    offset, sizeof(unaligned));
1782                                 tmp = &unaligned;
1783                         } else {
1784                                 return err;
1785                         }
1786
1787                 } else {
1788                         tmp = (struct btrfs_disk_key *)(kaddr + offset -
1789                                                         map_start);
1790                 }
1791                 ret = comp_keys(tmp, key);
1792
1793                 if (ret < 0)
1794                         low = mid + 1;
1795                 else if (ret > 0)
1796                         high = mid;
1797                 else {
1798                         *slot = mid;
1799                         return 0;
1800                 }
1801         }
1802         *slot = low;
1803         return 1;
1804 }
1805
1806 /*
1807  * simple bin_search frontend that does the right thing for
1808  * leaves vs nodes
1809  */
1810 int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
1811                      int level, int *slot)
1812 {
1813         if (level == 0)
1814                 return generic_bin_search(eb,
1815                                           offsetof(struct btrfs_leaf, items),
1816                                           sizeof(struct btrfs_item),
1817                                           key, btrfs_header_nritems(eb),
1818                                           slot);
1819         else
1820                 return generic_bin_search(eb,
1821                                           offsetof(struct btrfs_node, ptrs),
1822                                           sizeof(struct btrfs_key_ptr),
1823                                           key, btrfs_header_nritems(eb),
1824                                           slot);
1825 }
1826
1827 static void root_add_used(struct btrfs_root *root, u32 size)
1828 {
1829         spin_lock(&root->accounting_lock);
1830         btrfs_set_root_used(&root->root_item,
1831                             btrfs_root_used(&root->root_item) + size);
1832         spin_unlock(&root->accounting_lock);
1833 }
1834
1835 static void root_sub_used(struct btrfs_root *root, u32 size)
1836 {
1837         spin_lock(&root->accounting_lock);
1838         btrfs_set_root_used(&root->root_item,
1839                             btrfs_root_used(&root->root_item) - size);
1840         spin_unlock(&root->accounting_lock);
1841 }
1842
1843 /* given a node and slot number, this reads the blocks it points to.  The
1844  * extent buffer is returned with a reference taken (but unlocked).
1845  */
1846 static noinline struct extent_buffer *
1847 read_node_slot(struct btrfs_fs_info *fs_info, struct extent_buffer *parent,
1848                int slot)
1849 {
1850         int level = btrfs_header_level(parent);
1851         struct extent_buffer *eb;
1852
1853         if (slot < 0 || slot >= btrfs_header_nritems(parent))
1854                 return ERR_PTR(-ENOENT);
1855
1856         BUG_ON(level == 0);
1857
1858         eb = read_tree_block(fs_info, btrfs_node_blockptr(parent, slot),
1859                              btrfs_node_ptr_generation(parent, slot));
1860         if (!IS_ERR(eb) && !extent_buffer_uptodate(eb)) {
1861                 free_extent_buffer(eb);
1862                 eb = ERR_PTR(-EIO);
1863         }
1864
1865         return eb;
1866 }
1867
1868 /*
1869  * node level balancing, used to make sure nodes are in proper order for
1870  * item deletion.  We balance from the top down, so we have to make sure
1871  * that a deletion won't leave an node completely empty later on.
1872  */
1873 static noinline int balance_level(struct btrfs_trans_handle *trans,
1874                          struct btrfs_root *root,
1875                          struct btrfs_path *path, int level)
1876 {
1877         struct btrfs_fs_info *fs_info = root->fs_info;
1878         struct extent_buffer *right = NULL;
1879         struct extent_buffer *mid;
1880         struct extent_buffer *left = NULL;
1881         struct extent_buffer *parent = NULL;
1882         int ret = 0;
1883         int wret;
1884         int pslot;
1885         int orig_slot = path->slots[level];
1886         u64 orig_ptr;
1887
1888         if (level == 0)
1889                 return 0;
1890
1891         mid = path->nodes[level];
1892
1893         WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
1894                 path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
1895         WARN_ON(btrfs_header_generation(mid) != trans->transid);
1896
1897         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
1898
1899         if (level < BTRFS_MAX_LEVEL - 1) {
1900                 parent = path->nodes[level + 1];
1901                 pslot = path->slots[level + 1];
1902         }
1903
1904         /*
1905          * deal with the case where there is only one pointer in the root
1906          * by promoting the node below to a root
1907          */
1908         if (!parent) {
1909                 struct extent_buffer *child;
1910
1911                 if (btrfs_header_nritems(mid) != 1)
1912                         return 0;
1913
1914                 /* promote the child to a root */
1915                 child = read_node_slot(fs_info, mid, 0);
1916                 if (IS_ERR(child)) {
1917                         ret = PTR_ERR(child);
1918                         btrfs_handle_fs_error(fs_info, ret, NULL);
1919                         goto enospc;
1920                 }
1921
1922                 btrfs_tree_lock(child);
1923                 btrfs_set_lock_blocking(child);
1924                 ret = btrfs_cow_block(trans, root, child, mid, 0, &child);
1925                 if (ret) {
1926                         btrfs_tree_unlock(child);
1927                         free_extent_buffer(child);
1928                         goto enospc;
1929                 }
1930
1931                 tree_mod_log_set_root_pointer(root, child, 1);
1932                 rcu_assign_pointer(root->node, child);
1933
1934                 add_root_to_dirty_list(root);
1935                 btrfs_tree_unlock(child);
1936
1937                 path->locks[level] = 0;
1938                 path->nodes[level] = NULL;
1939                 clean_tree_block(fs_info, mid);
1940                 btrfs_tree_unlock(mid);
1941                 /* once for the path */
1942                 free_extent_buffer(mid);
1943
1944                 root_sub_used(root, mid->len);
1945                 btrfs_free_tree_block(trans, root, mid, 0, 1);
1946                 /* once for the root ptr */
1947                 free_extent_buffer_stale(mid);
1948                 return 0;
1949         }
1950         if (btrfs_header_nritems(mid) >
1951             BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
1952                 return 0;
1953
1954         left = read_node_slot(fs_info, parent, pslot - 1);
1955         if (IS_ERR(left))
1956                 left = NULL;
1957
1958         if (left) {
1959                 btrfs_tree_lock(left);
1960                 btrfs_set_lock_blocking(left);
1961                 wret = btrfs_cow_block(trans, root, left,
1962                                        parent, pslot - 1, &left);
1963                 if (wret) {
1964                         ret = wret;
1965                         goto enospc;
1966                 }
1967         }
1968
1969         right = read_node_slot(fs_info, parent, pslot + 1);
1970         if (IS_ERR(right))
1971                 right = NULL;
1972
1973         if (right) {
1974                 btrfs_tree_lock(right);
1975                 btrfs_set_lock_blocking(right);
1976                 wret = btrfs_cow_block(trans, root, right,
1977                                        parent, pslot + 1, &right);
1978                 if (wret) {
1979                         ret = wret;
1980                         goto enospc;
1981                 }
1982         }
1983
1984         /* first, try to make some room in the middle buffer */
1985         if (left) {
1986                 orig_slot += btrfs_header_nritems(left);
1987                 wret = push_node_left(trans, fs_info, left, mid, 1);
1988                 if (wret < 0)
1989                         ret = wret;
1990         }
1991
1992         /*
1993          * then try to empty the right most buffer into the middle
1994          */
1995         if (right) {
1996                 wret = push_node_left(trans, fs_info, mid, right, 1);
1997                 if (wret < 0 && wret != -ENOSPC)
1998                         ret = wret;
1999                 if (btrfs_header_nritems(right) == 0) {
2000                         clean_tree_block(fs_info, right);
2001                         btrfs_tree_unlock(right);
2002                         del_ptr(root, path, level + 1, pslot + 1);
2003                         root_sub_used(root, right->len);
2004                         btrfs_free_tree_block(trans, root, right, 0, 1);
2005                         free_extent_buffer_stale(right);
2006                         right = NULL;
2007                 } else {
2008                         struct btrfs_disk_key right_key;
2009                         btrfs_node_key(right, &right_key, 0);
2010                         tree_mod_log_set_node_key(fs_info, parent,
2011                                                   pslot + 1, 0);
2012                         btrfs_set_node_key(parent, &right_key, pslot + 1);
2013                         btrfs_mark_buffer_dirty(parent);
2014                 }
2015         }
2016         if (btrfs_header_nritems(mid) == 1) {
2017                 /*
2018                  * we're not allowed to leave a node with one item in the
2019                  * tree during a delete.  A deletion from lower in the tree
2020                  * could try to delete the only pointer in this node.
2021                  * So, pull some keys from the left.
2022                  * There has to be a left pointer at this point because
2023                  * otherwise we would have pulled some pointers from the
2024                  * right
2025                  */
2026                 if (!left) {
2027                         ret = -EROFS;
2028                         btrfs_handle_fs_error(fs_info, ret, NULL);
2029                         goto enospc;
2030                 }
2031                 wret = balance_node_right(trans, fs_info, mid, left);
2032                 if (wret < 0) {
2033                         ret = wret;
2034                         goto enospc;
2035                 }
2036                 if (wret == 1) {
2037                         wret = push_node_left(trans, fs_info, left, mid, 1);
2038                         if (wret < 0)
2039                                 ret = wret;
2040                 }
2041                 BUG_ON(wret == 1);
2042         }
2043         if (btrfs_header_nritems(mid) == 0) {
2044                 clean_tree_block(fs_info, mid);
2045                 btrfs_tree_unlock(mid);
2046                 del_ptr(root, path, level + 1, pslot);
2047                 root_sub_used(root, mid->len);
2048                 btrfs_free_tree_block(trans, root, mid, 0, 1);
2049                 free_extent_buffer_stale(mid);
2050                 mid = NULL;
2051         } else {
2052                 /* update the parent key to reflect our changes */
2053                 struct btrfs_disk_key mid_key;
2054                 btrfs_node_key(mid, &mid_key, 0);
2055                 tree_mod_log_set_node_key(fs_info, parent, pslot, 0);
2056                 btrfs_set_node_key(parent, &mid_key, pslot);
2057                 btrfs_mark_buffer_dirty(parent);
2058         }
2059
2060         /* update the path */
2061         if (left) {
2062                 if (btrfs_header_nritems(left) > orig_slot) {
2063                         extent_buffer_get(left);
2064                         /* left was locked after cow */
2065                         path->nodes[level] = left;
2066                         path->slots[level + 1] -= 1;
2067                         path->slots[level] = orig_slot;
2068                         if (mid) {
2069                                 btrfs_tree_unlock(mid);
2070                                 free_extent_buffer(mid);
2071                         }
2072                 } else {
2073                         orig_slot -= btrfs_header_nritems(left);
2074                         path->slots[level] = orig_slot;
2075                 }
2076         }
2077         /* double check we haven't messed things up */
2078         if (orig_ptr !=
2079             btrfs_node_blockptr(path->nodes[level], path->slots[level]))
2080                 BUG();
2081 enospc:
2082         if (right) {
2083                 btrfs_tree_unlock(right);
2084                 free_extent_buffer(right);
2085         }
2086         if (left) {
2087                 if (path->nodes[level] != left)
2088                         btrfs_tree_unlock(left);
2089                 free_extent_buffer(left);
2090         }
2091         return ret;
2092 }
2093
2094 /* Node balancing for insertion.  Here we only split or push nodes around
2095  * when they are completely full.  This is also done top down, so we
2096  * have to be pessimistic.
2097  */
2098 static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
2099                                           struct btrfs_root *root,
2100                                           struct btrfs_path *path, int level)
2101 {
2102         struct btrfs_fs_info *fs_info = root->fs_info;
2103         struct extent_buffer *right = NULL;
2104         struct extent_buffer *mid;
2105         struct extent_buffer *left = NULL;
2106         struct extent_buffer *parent = NULL;
2107         int ret = 0;
2108         int wret;
2109         int pslot;
2110         int orig_slot = path->slots[level];
2111
2112         if (level == 0)
2113                 return 1;
2114
2115         mid = path->nodes[level];
2116         WARN_ON(btrfs_header_generation(mid) != trans->transid);
2117
2118         if (level < BTRFS_MAX_LEVEL - 1) {
2119                 parent = path->nodes[level + 1];
2120                 pslot = path->slots[level + 1];
2121         }
2122
2123         if (!parent)
2124                 return 1;
2125
2126         left = read_node_slot(fs_info, parent, pslot - 1);
2127         if (IS_ERR(left))
2128                 left = NULL;
2129
2130         /* first, try to make some room in the middle buffer */
2131         if (left) {
2132                 u32 left_nr;
2133
2134                 btrfs_tree_lock(left);
2135                 btrfs_set_lock_blocking(left);
2136
2137                 left_nr = btrfs_header_nritems(left);
2138                 if (left_nr >= BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 1) {
2139                         wret = 1;
2140                 } else {
2141                         ret = btrfs_cow_block(trans, root, left, parent,
2142                                               pslot - 1, &left);
2143                         if (ret)
2144                                 wret = 1;
2145                         else {
2146                                 wret = push_node_left(trans, fs_info,
2147                                                       left, mid, 0);
2148                         }
2149                 }
2150                 if (wret < 0)
2151                         ret = wret;
2152                 if (wret == 0) {
2153                         struct btrfs_disk_key disk_key;
2154                         orig_slot += left_nr;
2155                         btrfs_node_key(mid, &disk_key, 0);
2156                         tree_mod_log_set_node_key(fs_info, parent, pslot, 0);
2157                         btrfs_set_node_key(parent, &disk_key, pslot);
2158                         btrfs_mark_buffer_dirty(parent);
2159                         if (btrfs_header_nritems(left) > orig_slot) {
2160                                 path->nodes[level] = left;
2161                                 path->slots[level + 1] -= 1;
2162                                 path->slots[level] = orig_slot;
2163                                 btrfs_tree_unlock(mid);
2164                                 free_extent_buffer(mid);
2165                         } else {
2166                                 orig_slot -=
2167                                         btrfs_header_nritems(left);
2168                                 path->slots[level] = orig_slot;
2169                                 btrfs_tree_unlock(left);
2170                                 free_extent_buffer(left);
2171                         }
2172                         return 0;
2173                 }
2174                 btrfs_tree_unlock(left);
2175                 free_extent_buffer(left);
2176         }
2177         right = read_node_slot(fs_info, parent, pslot + 1);
2178         if (IS_ERR(right))
2179                 right = NULL;
2180
2181         /*
2182          * then try to empty the right most buffer into the middle
2183          */
2184         if (right) {
2185                 u32 right_nr;
2186
2187                 btrfs_tree_lock(right);
2188                 btrfs_set_lock_blocking(right);
2189
2190                 right_nr = btrfs_header_nritems(right);
2191                 if (right_nr >= BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 1) {
2192                         wret = 1;
2193                 } else {
2194                         ret = btrfs_cow_block(trans, root, right,
2195                                               parent, pslot + 1,
2196                                               &right);
2197                         if (ret)
2198                                 wret = 1;
2199                         else {
2200                                 wret = balance_node_right(trans, fs_info,
2201                                                           right, mid);
2202                         }
2203                 }
2204                 if (wret < 0)
2205                         ret = wret;
2206                 if (wret == 0) {
2207                         struct btrfs_disk_key disk_key;
2208
2209                         btrfs_node_key(right, &disk_key, 0);
2210                         tree_mod_log_set_node_key(fs_info, parent,
2211                                                   pslot + 1, 0);
2212                         btrfs_set_node_key(parent, &disk_key, pslot + 1);
2213                         btrfs_mark_buffer_dirty(parent);
2214
2215                         if (btrfs_header_nritems(mid) <= orig_slot) {
2216                                 path->nodes[level] = right;
2217                                 path->slots[level + 1] += 1;
2218                                 path->slots[level] = orig_slot -
2219                                         btrfs_header_nritems(mid);
2220                                 btrfs_tree_unlock(mid);
2221                                 free_extent_buffer(mid);
2222                         } else {
2223                                 btrfs_tree_unlock(right);
2224                                 free_extent_buffer(right);
2225                         }
2226                         return 0;
2227                 }
2228                 btrfs_tree_unlock(right);
2229                 free_extent_buffer(right);
2230         }
2231         return 1;
2232 }
2233
2234 /*
2235  * readahead one full node of leaves, finding things that are close
2236  * to the block in 'slot', and triggering ra on them.
2237  */
2238 static void reada_for_search(struct btrfs_fs_info *fs_info,
2239                              struct btrfs_path *path,
2240                              int level, int slot, u64 objectid)
2241 {
2242         struct extent_buffer *node;
2243         struct btrfs_disk_key disk_key;
2244         u32 nritems;
2245         u64 search;
2246         u64 target;
2247         u64 nread = 0;
2248         struct extent_buffer *eb;
2249         u32 nr;
2250         u32 blocksize;
2251         u32 nscan = 0;
2252
2253         if (level != 1)
2254                 return;
2255
2256         if (!path->nodes[level])
2257                 return;
2258
2259         node = path->nodes[level];
2260
2261         search = btrfs_node_blockptr(node, slot);
2262         blocksize = fs_info->nodesize;
2263         eb = find_extent_buffer(fs_info, search);
2264         if (eb) {
2265                 free_extent_buffer(eb);
2266                 return;
2267         }
2268
2269         target = search;
2270
2271         nritems = btrfs_header_nritems(node);
2272         nr = slot;
2273
2274         while (1) {
2275                 if (path->reada == READA_BACK) {
2276                         if (nr == 0)
2277                                 break;
2278                         nr--;
2279                 } else if (path->reada == READA_FORWARD) {
2280                         nr++;
2281                         if (nr >= nritems)
2282                                 break;
2283                 }
2284                 if (path->reada == READA_BACK && objectid) {
2285                         btrfs_node_key(node, &disk_key, nr);
2286                         if (btrfs_disk_key_objectid(&disk_key) != objectid)
2287                                 break;
2288                 }
2289                 search = btrfs_node_blockptr(node, nr);
2290                 if ((search <= target && target - search <= 65536) ||
2291                     (search > target && search - target <= 65536)) {
2292                         readahead_tree_block(fs_info, search);
2293                         nread += blocksize;
2294                 }
2295                 nscan++;
2296                 if ((nread > 65536 || nscan > 32))
2297                         break;
2298         }
2299 }
2300
2301 static noinline void reada_for_balance(struct btrfs_fs_info *fs_info,
2302                                        struct btrfs_path *path, int level)
2303 {
2304         int slot;
2305         int nritems;
2306         struct extent_buffer *parent;
2307         struct extent_buffer *eb;
2308         u64 gen;
2309         u64 block1 = 0;
2310         u64 block2 = 0;
2311
2312         parent = path->nodes[level + 1];
2313         if (!parent)
2314                 return;
2315
2316         nritems = btrfs_header_nritems(parent);
2317         slot = path->slots[level + 1];
2318
2319         if (slot > 0) {
2320                 block1 = btrfs_node_blockptr(parent, slot - 1);
2321                 gen = btrfs_node_ptr_generation(parent, slot - 1);
2322                 eb = find_extent_buffer(fs_info, block1);
2323                 /*
2324                  * if we get -eagain from btrfs_buffer_uptodate, we
2325                  * don't want to return eagain here.  That will loop
2326                  * forever
2327                  */
2328                 if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
2329                         block1 = 0;
2330                 free_extent_buffer(eb);
2331         }
2332         if (slot + 1 < nritems) {
2333                 block2 = btrfs_node_blockptr(parent, slot + 1);
2334                 gen = btrfs_node_ptr_generation(parent, slot + 1);
2335                 eb = find_extent_buffer(fs_info, block2);
2336                 if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
2337                         block2 = 0;
2338                 free_extent_buffer(eb);
2339         }
2340
2341         if (block1)
2342                 readahead_tree_block(fs_info, block1);
2343         if (block2)
2344                 readahead_tree_block(fs_info, block2);
2345 }
2346
2347
2348 /*
2349  * when we walk down the tree, it is usually safe to unlock the higher layers
2350  * in the tree.  The exceptions are when our path goes through slot 0, because
2351  * operations on the tree might require changing key pointers higher up in the
2352  * tree.
2353  *
2354  * callers might also have set path->keep_locks, which tells this code to keep
2355  * the lock if the path points to the last slot in the block.  This is part of
2356  * walking through the tree, and selecting the next slot in the higher block.
2357  *
2358  * lowest_unlock sets the lowest level in the tree we're allowed to unlock.  so
2359  * if lowest_unlock is 1, level 0 won't be unlocked
2360  */
2361 static noinline void unlock_up(struct btrfs_path *path, int level,
2362                                int lowest_unlock, int min_write_lock_level,
2363                                int *write_lock_level)
2364 {
2365         int i;
2366         int skip_level = level;
2367         int no_skips = 0;
2368         struct extent_buffer *t;
2369
2370         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
2371                 if (!path->nodes[i])
2372                         break;
2373                 if (!path->locks[i])
2374                         break;
2375                 if (!no_skips && path->slots[i] == 0) {
2376                         skip_level = i + 1;
2377                         continue;
2378                 }
2379                 if (!no_skips && path->keep_locks) {
2380                         u32 nritems;
2381                         t = path->nodes[i];
2382                         nritems = btrfs_header_nritems(t);
2383                         if (nritems < 1 || path->slots[i] >= nritems - 1) {
2384                                 skip_level = i + 1;
2385                                 continue;
2386                         }
2387                 }
2388                 if (skip_level < i && i >= lowest_unlock)
2389                         no_skips = 1;
2390
2391                 t = path->nodes[i];
2392                 if (i >= lowest_unlock && i > skip_level && path->locks[i]) {
2393                         btrfs_tree_unlock_rw(t, path->locks[i]);
2394                         path->locks[i] = 0;
2395                         if (write_lock_level &&
2396                             i > min_write_lock_level &&
2397                             i <= *write_lock_level) {
2398                                 *write_lock_level = i - 1;
2399                         }
2400                 }
2401         }
2402 }
2403
2404 /*
2405  * This releases any locks held in the path starting at level and
2406  * going all the way up to the root.
2407  *
2408  * btrfs_search_slot will keep the lock held on higher nodes in a few
2409  * corner cases, such as COW of the block at slot zero in the node.  This
2410  * ignores those rules, and it should only be called when there are no
2411  * more updates to be done higher up in the tree.
2412  */
2413 noinline void btrfs_unlock_up_safe(struct btrfs_path *path, int level)
2414 {
2415         int i;
2416
2417         if (path->keep_locks)
2418                 return;
2419
2420         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
2421                 if (!path->nodes[i])
2422                         continue;
2423                 if (!path->locks[i])
2424                         continue;
2425                 btrfs_tree_unlock_rw(path->nodes[i], path->locks[i]);
2426                 path->locks[i] = 0;
2427         }
2428 }
2429
2430 /*
2431  * helper function for btrfs_search_slot.  The goal is to find a block
2432  * in cache without setting the path to blocking.  If we find the block
2433  * we return zero and the path is unchanged.
2434  *
2435  * If we can't find the block, we set the path blocking and do some
2436  * reada.  -EAGAIN is returned and the search must be repeated.
2437  */
2438 static int
2439 read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
2440                       struct extent_buffer **eb_ret, int level, int slot,
2441                       const struct btrfs_key *key)
2442 {
2443         struct btrfs_fs_info *fs_info = root->fs_info;
2444         u64 blocknr;
2445         u64 gen;
2446         struct extent_buffer *b = *eb_ret;
2447         struct extent_buffer *tmp;
2448         int ret;
2449
2450         blocknr = btrfs_node_blockptr(b, slot);
2451         gen = btrfs_node_ptr_generation(b, slot);
2452
2453         tmp = find_extent_buffer(fs_info, blocknr);
2454         if (tmp) {
2455                 /* first we do an atomic uptodate check */
2456                 if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
2457                         *eb_ret = tmp;
2458                         return 0;
2459                 }
2460
2461                 /* the pages were up to date, but we failed
2462                  * the generation number check.  Do a full
2463                  * read for the generation number that is correct.
2464                  * We must do this without dropping locks so
2465                  * we can trust our generation number
2466                  */
2467                 btrfs_set_path_blocking(p);
2468
2469                 /* now we're allowed to do a blocking uptodate check */
2470                 ret = btrfs_read_buffer(tmp, gen);
2471                 if (!ret) {
2472                         *eb_ret = tmp;
2473                         return 0;
2474                 }
2475                 free_extent_buffer(tmp);
2476                 btrfs_release_path(p);
2477                 return -EIO;
2478         }
2479
2480         /*
2481          * reduce lock contention at high levels
2482          * of the btree by dropping locks before
2483          * we read.  Don't release the lock on the current
2484          * level because we need to walk this node to figure
2485          * out which blocks to read.
2486          */
2487         btrfs_unlock_up_safe(p, level + 1);
2488         btrfs_set_path_blocking(p);
2489
2490         free_extent_buffer(tmp);
2491         if (p->reada != READA_NONE)
2492                 reada_for_search(fs_info, p, level, slot, key->objectid);
2493
2494         btrfs_release_path(p);
2495
2496         ret = -EAGAIN;
2497         tmp = read_tree_block(fs_info, blocknr, 0);
2498         if (!IS_ERR(tmp)) {
2499                 /*
2500                  * If the read above didn't mark this buffer up to date,
2501                  * it will never end up being up to date.  Set ret to EIO now
2502                  * and give up so that our caller doesn't loop forever
2503                  * on our EAGAINs.
2504                  */
2505                 if (!btrfs_buffer_uptodate(tmp, 0, 0))
2506                         ret = -EIO;
2507                 free_extent_buffer(tmp);
2508         } else {
2509                 ret = PTR_ERR(tmp);
2510         }
2511         return ret;
2512 }
2513
2514 /*
2515  * helper function for btrfs_search_slot.  This does all of the checks
2516  * for node-level blocks and does any balancing required based on
2517  * the ins_len.
2518  *
2519  * If no extra work was required, zero is returned.  If we had to
2520  * drop the path, -EAGAIN is returned and btrfs_search_slot must
2521  * start over
2522  */
2523 static int
2524 setup_nodes_for_search(struct btrfs_trans_handle *trans,
2525                        struct btrfs_root *root, struct btrfs_path *p,
2526                        struct extent_buffer *b, int level, int ins_len,
2527                        int *write_lock_level)
2528 {
2529         struct btrfs_fs_info *fs_info = root->fs_info;
2530         int ret;
2531
2532         if ((p->search_for_split || ins_len > 0) && btrfs_header_nritems(b) >=
2533             BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 3) {
2534                 int sret;
2535
2536                 if (*write_lock_level < level + 1) {
2537                         *write_lock_level = level + 1;
2538                         btrfs_release_path(p);
2539                         goto again;
2540                 }
2541
2542                 btrfs_set_path_blocking(p);
2543                 reada_for_balance(fs_info, p, level);
2544                 sret = split_node(trans, root, p, level);
2545                 btrfs_clear_path_blocking(p, NULL, 0);
2546
2547                 BUG_ON(sret > 0);
2548                 if (sret) {
2549                         ret = sret;
2550                         goto done;
2551                 }
2552                 b = p->nodes[level];
2553         } else if (ins_len < 0 && btrfs_header_nritems(b) <
2554                    BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 2) {
2555                 int sret;
2556
2557                 if (*write_lock_level < level + 1) {
2558                         *write_lock_level = level + 1;
2559                         btrfs_release_path(p);
2560                         goto again;
2561                 }
2562
2563                 btrfs_set_path_blocking(p);
2564                 reada_for_balance(fs_info, p, level);
2565                 sret = balance_level(trans, root, p, level);
2566                 btrfs_clear_path_blocking(p, NULL, 0);
2567
2568                 if (sret) {
2569                         ret = sret;
2570                         goto done;
2571                 }
2572                 b = p->nodes[level];
2573                 if (!b) {
2574                         btrfs_release_path(p);
2575                         goto again;
2576                 }
2577                 BUG_ON(btrfs_header_nritems(b) == 1);
2578         }
2579         return 0;
2580
2581 again:
2582         ret = -EAGAIN;
2583 done:
2584         return ret;
2585 }
2586
2587 static void key_search_validate(struct extent_buffer *b,
2588                                 const struct btrfs_key *key,
2589                                 int level)
2590 {
2591 #ifdef CONFIG_BTRFS_ASSERT
2592         struct btrfs_disk_key disk_key;
2593
2594         btrfs_cpu_key_to_disk(&disk_key, key);
2595
2596         if (level == 0)
2597                 ASSERT(!memcmp_extent_buffer(b, &disk_key,
2598                     offsetof(struct btrfs_leaf, items[0].key),
2599                     sizeof(disk_key)));
2600         else
2601                 ASSERT(!memcmp_extent_buffer(b, &disk_key,
2602                     offsetof(struct btrfs_node, ptrs[0].key),
2603                     sizeof(disk_key)));
2604 #endif
2605 }
2606
2607 static int key_search(struct extent_buffer *b, const struct btrfs_key *key,
2608                       int level, int *prev_cmp, int *slot)
2609 {
2610         if (*prev_cmp != 0) {
2611                 *prev_cmp = btrfs_bin_search(b, key, level, slot);
2612                 return *prev_cmp;
2613         }
2614
2615         key_search_validate(b, key, level);
2616         *slot = 0;
2617
2618         return 0;
2619 }
2620
2621 int btrfs_find_item(struct btrfs_root *fs_root, struct btrfs_path *path,
2622                 u64 iobjectid, u64 ioff, u8 key_type,
2623                 struct btrfs_key *found_key)
2624 {
2625         int ret;
2626         struct btrfs_key key;
2627         struct extent_buffer *eb;
2628
2629         ASSERT(path);
2630         ASSERT(found_key);
2631
2632         key.type = key_type;
2633         key.objectid = iobjectid;
2634         key.offset = ioff;
2635
2636         ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
2637         if (ret < 0)
2638                 return ret;
2639
2640         eb = path->nodes[0];
2641         if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
2642                 ret = btrfs_next_leaf(fs_root, path);
2643                 if (ret)
2644                         return ret;
2645                 eb = path->nodes[0];
2646         }
2647
2648         btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
2649         if (found_key->type != key.type ||
2650                         found_key->objectid != key.objectid)
2651                 return 1;
2652
2653         return 0;
2654 }
2655
2656 /*
2657  * btrfs_search_slot - look for a key in a tree and perform necessary
2658  * modifications to preserve tree invariants.
2659  *
2660  * @trans:      Handle of transaction, used when modifying the tree
2661  * @p:          Holds all btree nodes along the search path
2662  * @root:       The root node of the tree
2663  * @key:        The key we are looking for
2664  * @ins_len:    Indicates purpose of search, for inserts it is 1, for
2665  *              deletions it's -1. 0 for plain searches
2666  * @cow:        boolean should CoW operations be performed. Must always be 1
2667  *              when modifying the tree.
2668  *
2669  * If @ins_len > 0, nodes and leaves will be split as we walk down the tree.
2670  * If @ins_len < 0, nodes will be merged as we walk down the tree (if possible)
2671  *
2672  * If @key is found, 0 is returned and you can find the item in the leaf level
2673  * of the path (level 0)
2674  *
2675  * If @key isn't found, 1 is returned and the leaf level of the path (level 0)
2676  * points to the slot where it should be inserted
2677  *
2678  * If an error is encountered while searching the tree a negative error number
2679  * is returned
2680  */
2681 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
2682                       const struct btrfs_key *key, struct btrfs_path *p,
2683                       int ins_len, int cow)
2684 {
2685         struct btrfs_fs_info *fs_info = root->fs_info;
2686         struct extent_buffer *b;
2687         int slot;
2688         int ret;
2689         int err;
2690         int level;
2691         int lowest_unlock = 1;
2692         int root_lock;
2693         /* everything at write_lock_level or lower must be write locked */
2694         int write_lock_level = 0;
2695         u8 lowest_level = 0;
2696         int min_write_lock_level;
2697         int prev_cmp;
2698
2699         lowest_level = p->lowest_level;
2700         WARN_ON(lowest_level && ins_len > 0);
2701         WARN_ON(p->nodes[0] != NULL);
2702         BUG_ON(!cow && ins_len);
2703
2704         if (ins_len < 0) {
2705                 lowest_unlock = 2;
2706
2707                 /* when we are removing items, we might have to go up to level
2708                  * two as we update tree pointers  Make sure we keep write
2709                  * for those levels as well
2710                  */
2711                 write_lock_level = 2;
2712         } else if (ins_len > 0) {
2713                 /*
2714                  * for inserting items, make sure we have a write lock on
2715                  * level 1 so we can update keys
2716                  */
2717                 write_lock_level = 1;
2718         }
2719
2720         if (!cow)
2721                 write_lock_level = -1;
2722
2723         if (cow && (p->keep_locks || p->lowest_level))
2724                 write_lock_level = BTRFS_MAX_LEVEL;
2725
2726         min_write_lock_level = write_lock_level;
2727
2728 again:
2729         prev_cmp = -1;
2730         /*
2731          * we try very hard to do read locks on the root
2732          */
2733         root_lock = BTRFS_READ_LOCK;
2734         level = 0;
2735         if (p->search_commit_root) {
2736                 /*
2737                  * the commit roots are read only
2738                  * so we always do read locks
2739                  */
2740                 if (p->need_commit_sem)
2741                         down_read(&fs_info->commit_root_sem);
2742                 b = root->commit_root;
2743                 extent_buffer_get(b);
2744                 level = btrfs_header_level(b);
2745                 if (p->need_commit_sem)
2746                         up_read(&fs_info->commit_root_sem);
2747                 if (!p->skip_locking)
2748                         btrfs_tree_read_lock(b);
2749         } else {
2750                 if (p->skip_locking) {
2751                         b = btrfs_root_node(root);
2752                         level = btrfs_header_level(b);
2753                 } else {
2754                         /* we don't know the level of the root node
2755                          * until we actually have it read locked
2756                          */
2757                         b = btrfs_read_lock_root_node(root);
2758                         level = btrfs_header_level(b);
2759                         if (level <= write_lock_level) {
2760                                 /* whoops, must trade for write lock */
2761                                 btrfs_tree_read_unlock(b);
2762                                 free_extent_buffer(b);
2763                                 b = btrfs_lock_root_node(root);
2764                                 root_lock = BTRFS_WRITE_LOCK;
2765
2766                                 /* the level might have changed, check again */
2767                                 level = btrfs_header_level(b);
2768                         }
2769                 }
2770         }
2771         p->nodes[level] = b;
2772         if (!p->skip_locking)
2773                 p->locks[level] = root_lock;
2774
2775         while (b) {
2776                 level = btrfs_header_level(b);
2777
2778                 /*
2779                  * setup the path here so we can release it under lock
2780                  * contention with the cow code
2781                  */
2782                 if (cow) {
2783                         bool last_level = (level == (BTRFS_MAX_LEVEL - 1));
2784
2785                         /*
2786                          * if we don't really need to cow this block
2787                          * then we don't want to set the path blocking,
2788                          * so we test it here
2789                          */
2790                         if (!should_cow_block(trans, root, b)) {
2791                                 trans->dirty = true;
2792                                 goto cow_done;
2793                         }
2794
2795                         /*
2796                          * must have write locks on this node and the
2797                          * parent
2798                          */
2799                         if (level > write_lock_level ||
2800                             (level + 1 > write_lock_level &&
2801                             level + 1 < BTRFS_MAX_LEVEL &&
2802                             p->nodes[level + 1])) {
2803                                 write_lock_level = level + 1;
2804                                 btrfs_release_path(p);
2805                                 goto again;
2806                         }
2807
2808                         btrfs_set_path_blocking(p);
2809                         if (last_level)
2810                                 err = btrfs_cow_block(trans, root, b, NULL, 0,
2811                                                       &b);
2812                         else
2813                                 err = btrfs_cow_block(trans, root, b,
2814                                                       p->nodes[level + 1],
2815                                                       p->slots[level + 1], &b);
2816                         if (err) {
2817                                 ret = err;
2818                                 goto done;
2819                         }
2820                 }
2821 cow_done:
2822                 p->nodes[level] = b;
2823                 btrfs_clear_path_blocking(p, NULL, 0);
2824
2825                 /*
2826                  * we have a lock on b and as long as we aren't changing
2827                  * the tree, there is no way to for the items in b to change.
2828                  * It is safe to drop the lock on our parent before we
2829                  * go through the expensive btree search on b.
2830                  *
2831                  * If we're inserting or deleting (ins_len != 0), then we might
2832                  * be changing slot zero, which may require changing the parent.
2833                  * So, we can't drop the lock until after we know which slot
2834                  * we're operating on.
2835                  */
2836                 if (!ins_len && !p->keep_locks) {
2837                         int u = level + 1;
2838
2839                         if (u < BTRFS_MAX_LEVEL && p->locks[u]) {
2840                                 btrfs_tree_unlock_rw(p->nodes[u], p->locks[u]);
2841                                 p->locks[u] = 0;
2842                         }
2843                 }
2844
2845                 ret = key_search(b, key, level, &prev_cmp, &slot);
2846                 if (ret < 0)
2847                         goto done;
2848
2849                 if (level != 0) {
2850                         int dec = 0;
2851                         if (ret && slot > 0) {
2852                                 dec = 1;
2853                                 slot -= 1;
2854                         }
2855                         p->slots[level] = slot;
2856                         err = setup_nodes_for_search(trans, root, p, b, level,
2857                                              ins_len, &write_lock_level);
2858                         if (err == -EAGAIN)
2859                                 goto again;
2860                         if (err) {
2861                                 ret = err;
2862                                 goto done;
2863                         }
2864                         b = p->nodes[level];
2865                         slot = p->slots[level];
2866
2867                         /*
2868                          * slot 0 is special, if we change the key
2869                          * we have to update the parent pointer
2870                          * which means we must have a write lock
2871                          * on the parent
2872                          */
2873                         if (slot == 0 && ins_len &&
2874                             write_lock_level < level + 1) {
2875                                 write_lock_level = level + 1;
2876                                 btrfs_release_path(p);
2877                                 goto again;
2878                         }
2879
2880                         unlock_up(p, level, lowest_unlock,
2881                                   min_write_lock_level, &write_lock_level);
2882
2883                         if (level == lowest_level) {
2884                                 if (dec)
2885                                         p->slots[level]++;
2886                                 goto done;
2887                         }
2888
2889                         err = read_block_for_search(root, p, &b, level,
2890                                                     slot, key);
2891                         if (err == -EAGAIN)
2892                                 goto again;
2893                         if (err) {
2894                                 ret = err;
2895                                 goto done;
2896                         }
2897
2898                         if (!p->skip_locking) {
2899                                 level = btrfs_header_level(b);
2900                                 if (level <= write_lock_level) {
2901                                         err = btrfs_try_tree_write_lock(b);
2902                                         if (!err) {
2903                                                 btrfs_set_path_blocking(p);
2904                                                 btrfs_tree_lock(b);
2905                                                 btrfs_clear_path_blocking(p, b,
2906                                                                   BTRFS_WRITE_LOCK);
2907                                         }
2908                                         p->locks[level] = BTRFS_WRITE_LOCK;
2909                                 } else {
2910                                         err = btrfs_tree_read_lock_atomic(b);
2911                                         if (!err) {
2912                                                 btrfs_set_path_blocking(p);
2913                                                 btrfs_tree_read_lock(b);
2914                                                 btrfs_clear_path_blocking(p, b,
2915                                                                   BTRFS_READ_LOCK);
2916                                         }
2917                                         p->locks[level] = BTRFS_READ_LOCK;
2918                                 }
2919                                 p->nodes[level] = b;
2920                         }
2921                 } else {
2922                         p->slots[level] = slot;
2923                         if (ins_len > 0 &&
2924                             btrfs_leaf_free_space(fs_info, b) < ins_len) {
2925                                 if (write_lock_level < 1) {
2926                                         write_lock_level = 1;
2927                                         btrfs_release_path(p);
2928                                         goto again;
2929                                 }
2930
2931                                 btrfs_set_path_blocking(p);
2932                                 err = split_leaf(trans, root, key,
2933                                                  p, ins_len, ret == 0);
2934                                 btrfs_clear_path_blocking(p, NULL, 0);
2935
2936                                 BUG_ON(err > 0);
2937                                 if (err) {
2938                                         ret = err;
2939                                         goto done;
2940                                 }
2941                         }
2942                         if (!p->search_for_split)
2943                                 unlock_up(p, level, lowest_unlock,
2944                                           min_write_lock_level, &write_lock_level);
2945                         goto done;
2946                 }
2947         }
2948         ret = 1;
2949 done:
2950         /*
2951          * we don't really know what they plan on doing with the path
2952          * from here on, so for now just mark it as blocking
2953          */
2954         if (!p->leave_spinning)
2955                 btrfs_set_path_blocking(p);
2956         if (ret < 0 && !p->skip_release_on_error)
2957                 btrfs_release_path(p);
2958         return ret;
2959 }
2960
2961 /*
2962  * Like btrfs_search_slot, this looks for a key in the given tree. It uses the
2963  * current state of the tree together with the operations recorded in the tree
2964  * modification log to search for the key in a previous version of this tree, as
2965  * denoted by the time_seq parameter.
2966  *
2967  * Naturally, there is no support for insert, delete or cow operations.
2968  *
2969  * The resulting path and return value will be set up as if we called
2970  * btrfs_search_slot at that point in time with ins_len and cow both set to 0.
2971  */
2972 int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key,
2973                           struct btrfs_path *p, u64 time_seq)
2974 {
2975         struct btrfs_fs_info *fs_info = root->fs_info;
2976         struct extent_buffer *b;
2977         int slot;
2978         int ret;
2979         int err;
2980         int level;
2981         int lowest_unlock = 1;
2982         u8 lowest_level = 0;
2983         int prev_cmp = -1;
2984
2985         lowest_level = p->lowest_level;
2986         WARN_ON(p->nodes[0] != NULL);
2987
2988         if (p->search_commit_root) {
2989                 BUG_ON(time_seq);
2990                 return btrfs_search_slot(NULL, root, key, p, 0, 0);
2991         }
2992
2993 again:
2994         b = get_old_root(root, time_seq);
2995         level = btrfs_header_level(b);
2996         p->locks[level] = BTRFS_READ_LOCK;
2997
2998         while (b) {
2999                 level = btrfs_header_level(b);
3000                 p->nodes[level] = b;
3001                 btrfs_clear_path_blocking(p, NULL, 0);
3002
3003                 /*
3004                  * we have a lock on b and as long as we aren't changing
3005                  * the tree, there is no way to for the items in b to change.
3006                  * It is safe to drop the lock on our parent before we
3007                  * go through the expensive btree search on b.
3008                  */
3009                 btrfs_unlock_up_safe(p, level + 1);
3010
3011                 /*
3012                  * Since we can unwind ebs we want to do a real search every
3013                  * time.
3014                  */
3015                 prev_cmp = -1;
3016                 ret = key_search(b, key, level, &prev_cmp, &slot);
3017
3018                 if (level != 0) {
3019                         int dec = 0;
3020                         if (ret && slot > 0) {
3021                                 dec = 1;
3022                                 slot -= 1;
3023                         }
3024                         p->slots[level] = slot;
3025                         unlock_up(p, level, lowest_unlock, 0, NULL);
3026
3027                         if (level == lowest_level) {
3028                                 if (dec)
3029                                         p->slots[level]++;
3030                                 goto done;
3031                         }
3032
3033                         err = read_block_for_search(root, p, &b, level,
3034                                                     slot, key);
3035                         if (err == -EAGAIN)
3036                                 goto again;
3037                         if (err) {
3038                                 ret = err;
3039                                 goto done;
3040                         }
3041
3042                         level = btrfs_header_level(b);
3043                         err = btrfs_tree_read_lock_atomic(b);
3044                         if (!err) {
3045                                 btrfs_set_path_blocking(p);
3046                                 btrfs_tree_read_lock(b);
3047                                 btrfs_clear_path_blocking(p, b,
3048                                                           BTRFS_READ_LOCK);
3049                         }
3050                         b = tree_mod_log_rewind(fs_info, p, b, time_seq);
3051                         if (!b) {
3052                                 ret = -ENOMEM;
3053                                 goto done;
3054                         }
3055                         p->locks[level] = BTRFS_READ_LOCK;
3056                         p->nodes[level] = b;
3057                 } else {
3058                         p->slots[level] = slot;
3059                         unlock_up(p, level, lowest_unlock, 0, NULL);
3060                         goto done;
3061                 }
3062         }
3063         ret = 1;
3064 done:
3065         if (!p->leave_spinning)
3066                 btrfs_set_path_blocking(p);
3067         if (ret < 0)
3068                 btrfs_release_path(p);
3069
3070         return ret;
3071 }
3072
3073 /*
3074  * helper to use instead of search slot if no exact match is needed but
3075  * instead the next or previous item should be returned.
3076  * When find_higher is true, the next higher item is returned, the next lower
3077  * otherwise.
3078  * When return_any and find_higher are both true, and no higher item is found,
3079  * return the next lower instead.
3080  * When return_any is true and find_higher is false, and no lower item is found,
3081  * return the next higher instead.
3082  * It returns 0 if any item is found, 1 if none is found (tree empty), and
3083  * < 0 on error
3084  */
3085 int btrfs_search_slot_for_read(struct btrfs_root *root,
3086                                const struct btrfs_key *key,
3087                                struct btrfs_path *p, int find_higher,
3088                                int return_any)
3089 {
3090         int ret;
3091         struct extent_buffer *leaf;
3092
3093 again:
3094         ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
3095         if (ret <= 0)
3096                 return ret;
3097         /*
3098          * a return value of 1 means the path is at the position where the
3099          * item should be inserted. Normally this is the next bigger item,
3100          * but in case the previous item is the last in a leaf, path points
3101          * to the first free slot in the previous leaf, i.e. at an invalid
3102          * item.
3103          */
3104         leaf = p->nodes[0];
3105
3106         if (find_higher) {
3107                 if (p->slots[0] >= btrfs_header_nritems(leaf)) {
3108                         ret = btrfs_next_leaf(root, p);
3109                         if (ret <= 0)
3110                                 return ret;
3111                         if (!return_any)
3112                                 return 1;
3113                         /*
3114                          * no higher item found, return the next
3115                          * lower instead
3116                          */
3117                         return_any = 0;
3118                         find_higher = 0;
3119                         btrfs_release_path(p);
3120                         goto again;
3121                 }
3122         } else {
3123                 if (p->slots[0] == 0) {
3124                         ret = btrfs_prev_leaf(root, p);
3125                         if (ret < 0)
3126                                 return ret;
3127                         if (!ret) {
3128                                 leaf = p->nodes[0];
3129                                 if (p->slots[0] == btrfs_header_nritems(leaf))
3130                                         p->slots[0]--;
3131                                 return 0;
3132                         }
3133                         if (!return_any)
3134                                 return 1;
3135                         /*
3136                          * no lower item found, return the next
3137                          * higher instead
3138                          */
3139                         return_any = 0;
3140                         find_higher = 1;
3141                         btrfs_release_path(p);
3142                         goto again;
3143                 } else {
3144                         --p->slots[0];
3145                 }
3146         }
3147         return 0;
3148 }
3149
3150 /*
3151  * adjust the pointers going up the tree, starting at level
3152  * making sure the right key of each node is points to 'key'.
3153  * This is used after shifting pointers to the left, so it stops
3154  * fixing up pointers when a given leaf/node is not in slot 0 of the
3155  * higher levels
3156  *
3157  */
3158 static void fixup_low_keys(struct btrfs_fs_info *fs_info,
3159                            struct btrfs_path *path,
3160                            struct btrfs_disk_key *key, int level)
3161 {
3162         int i;
3163         struct extent_buffer *t;
3164
3165         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
3166                 int tslot = path->slots[i];
3167                 if (!path->nodes[i])
3168                         break;
3169                 t = path->nodes[i];
3170                 tree_mod_log_set_node_key(fs_info, t, tslot, 1);
3171                 btrfs_set_node_key(t, key, tslot);
3172                 btrfs_mark_buffer_dirty(path->nodes[i]);
3173                 if (tslot != 0)
3174                         break;
3175         }
3176 }
3177
3178 /*
3179  * update item key.
3180  *
3181  * This function isn't completely safe. It's the caller's responsibility
3182  * that the new key won't break the order
3183  */
3184 void btrfs_set_item_key_safe(struct btrfs_fs_info *fs_info,
3185                              struct btrfs_path *path,
3186                              const struct btrfs_key *new_key)
3187 {
3188         struct btrfs_disk_key disk_key;
3189         struct extent_buffer *eb;
3190         int slot;
3191
3192         eb = path->nodes[0];
3193         slot = path->slots[0];
3194         if (slot > 0) {
3195                 btrfs_item_key(eb, &disk_key, slot - 1);
3196                 BUG_ON(comp_keys(&disk_key, new_key) >= 0);
3197         }
3198         if (slot < btrfs_header_nritems(eb) - 1) {
3199                 btrfs_item_key(eb, &disk_key, slot + 1);
3200                 BUG_ON(comp_keys(&disk_key, new_key) <= 0);
3201         }
3202
3203         btrfs_cpu_key_to_disk(&disk_key, new_key);
3204         btrfs_set_item_key(eb, &disk_key, slot);
3205         btrfs_mark_buffer_dirty(eb);
3206         if (slot == 0)
3207                 fixup_low_keys(fs_info, path, &disk_key, 1);
3208 }
3209
3210 /*
3211  * try to push data from one node into the next node left in the
3212  * tree.
3213  *
3214  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
3215  * error, and > 0 if there was no room in the left hand block.
3216  */
3217 static int push_node_left(struct btrfs_trans_handle *trans,
3218                           struct btrfs_fs_info *fs_info,
3219                           struct extent_buffer *dst,
3220                           struct extent_buffer *src, int empty)
3221 {
3222         int push_items = 0;
3223         int src_nritems;
3224         int dst_nritems;
3225         int ret = 0;
3226
3227         src_nritems = btrfs_header_nritems(src);
3228         dst_nritems = btrfs_header_nritems(dst);
3229         push_items = BTRFS_NODEPTRS_PER_BLOCK(fs_info) - dst_nritems;
3230         WARN_ON(btrfs_header_generation(src) != trans->transid);
3231         WARN_ON(btrfs_header_generation(dst) != trans->transid);
3232
3233         if (!empty && src_nritems <= 8)
3234                 return 1;
3235
3236         if (push_items <= 0)
3237                 return 1;
3238
3239         if (empty) {
3240                 push_items = min(src_nritems, push_items);
3241                 if (push_items < src_nritems) {
3242                         /* leave at least 8 pointers in the node if
3243                          * we aren't going to empty it
3244                          */
3245                         if (src_nritems - push_items < 8) {
3246                                 if (push_items <= 8)
3247                                         return 1;
3248                                 push_items -= 8;
3249                         }
3250                 }
3251         } else
3252                 push_items = min(src_nritems - 8, push_items);
3253
3254         ret = tree_mod_log_eb_copy(fs_info, dst, src, dst_nritems, 0,
3255                                    push_items);
3256         if (ret) {
3257                 btrfs_abort_transaction(trans, ret);
3258                 return ret;
3259         }
3260         copy_extent_buffer(dst, src,
3261                            btrfs_node_key_ptr_offset(dst_nritems),
3262                            btrfs_node_key_ptr_offset(0),
3263                            push_items * sizeof(struct btrfs_key_ptr));
3264
3265         if (push_items < src_nritems) {
3266                 /*
3267                  * don't call tree_mod_log_eb_move here, key removal was already
3268                  * fully logged by tree_mod_log_eb_copy above.
3269                  */
3270                 memmove_extent_buffer(src, btrfs_node_key_ptr_offset(0),
3271                                       btrfs_node_key_ptr_offset(push_items),
3272                                       (src_nritems - push_items) *
3273                                       sizeof(struct btrfs_key_ptr));
3274         }
3275         btrfs_set_header_nritems(src, src_nritems - push_items);
3276         btrfs_set_header_nritems(dst, dst_nritems + push_items);
3277         btrfs_mark_buffer_dirty(src);
3278         btrfs_mark_buffer_dirty(dst);
3279
3280         return ret;
3281 }
3282
3283 /*
3284  * try to push data from one node into the next node right in the
3285  * tree.
3286  *
3287  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
3288  * error, and > 0 if there was no room in the right hand block.
3289  *
3290  * this will  only push up to 1/2 the contents of the left node over
3291  */
3292 static int balance_node_right(struct btrfs_trans_handle *trans,
3293                               struct btrfs_fs_info *fs_info,
3294                               struct extent_buffer *dst,
3295                               struct extent_buffer *src)
3296 {
3297         int push_items = 0;
3298         int max_push;
3299         int src_nritems;
3300         int dst_nritems;
3301         int ret = 0;
3302
3303         WARN_ON(btrfs_header_generation(src) != trans->transid);
3304         WARN_ON(btrfs_header_generation(dst) != trans->transid);
3305
3306         src_nritems = btrfs_header_nritems(src);
3307         dst_nritems = btrfs_header_nritems(dst);
3308         push_items = BTRFS_NODEPTRS_PER_BLOCK(fs_info) - dst_nritems;
3309         if (push_items <= 0)
3310                 return 1;
3311
3312         if (src_nritems < 4)
3313                 return 1;
3314
3315         max_push = src_nritems / 2 + 1;
3316         /* don't try to empty the node */
3317         if (max_push >= src_nritems)
3318                 return 1;
3319
3320         if (max_push < push_items)
3321                 push_items = max_push;
3322
3323         tree_mod_log_eb_move(fs_info, dst, push_items, 0, dst_nritems);
3324         memmove_extent_buffer(dst, btrfs_node_key_ptr_offset(push_items),
3325                                       btrfs_node_key_ptr_offset(0),
3326                                       (dst_nritems) *
3327                                       sizeof(struct btrfs_key_ptr));
3328
3329         ret = tree_mod_log_eb_copy(fs_info, dst, src, 0,
3330                                    src_nritems - push_items, push_items);
3331         if (ret) {
3332                 btrfs_abort_transaction(trans, ret);
3333                 return ret;
3334         }
3335         copy_extent_buffer(dst, src,
3336                            btrfs_node_key_ptr_offset(0),
3337                            btrfs_node_key_ptr_offset(src_nritems - push_items),
3338                            push_items * sizeof(struct btrfs_key_ptr));
3339
3340         btrfs_set_header_nritems(src, src_nritems - push_items);
3341         btrfs_set_header_nritems(dst, dst_nritems + push_items);
3342
3343         btrfs_mark_buffer_dirty(src);
3344         btrfs_mark_buffer_dirty(dst);
3345
3346         return ret;
3347 }
3348
3349 /*
3350  * helper function to insert a new root level in the tree.
3351  * A new node is allocated, and a single item is inserted to
3352  * point to the existing root
3353  *
3354  * returns zero on success or < 0 on failure.
3355  */
3356 static noinline int insert_new_root(struct btrfs_trans_handle *trans,
3357                            struct btrfs_root *root,
3358                            struct btrfs_path *path, int level)
3359 {
3360         struct btrfs_fs_info *fs_info = root->fs_info;
3361         u64 lower_gen;
3362         struct extent_buffer *lower;
3363         struct extent_buffer *c;
3364         struct extent_buffer *old;
3365         struct btrfs_disk_key lower_key;
3366
3367         BUG_ON(path->nodes[level]);
3368         BUG_ON(path->nodes[level-1] != root->node);
3369
3370         lower = path->nodes[level-1];
3371         if (level == 1)
3372                 btrfs_item_key(lower, &lower_key, 0);
3373         else
3374                 btrfs_node_key(lower, &lower_key, 0);
3375
3376         c = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
3377                                    &lower_key, level, root->node->start, 0);
3378         if (IS_ERR(c))
3379                 return PTR_ERR(c);
3380
3381         root_add_used(root, fs_info->nodesize);
3382
3383         memzero_extent_buffer(c, 0, sizeof(struct btrfs_header));
3384         btrfs_set_header_nritems(c, 1);
3385         btrfs_set_header_level(c, level);
3386         btrfs_set_header_bytenr(c, c->start);
3387         btrfs_set_header_generation(c, trans->transid);
3388         btrfs_set_header_backref_rev(c, BTRFS_MIXED_BACKREF_REV);
3389         btrfs_set_header_owner(c, root->root_key.objectid);
3390
3391         write_extent_buffer_fsid(c, fs_info->fsid);
3392         write_extent_buffer_chunk_tree_uuid(c, fs_info->chunk_tree_uuid);
3393
3394         btrfs_set_node_key(c, &lower_key, 0);
3395         btrfs_set_node_blockptr(c, 0, lower->start);
3396         lower_gen = btrfs_header_generation(lower);
3397         WARN_ON(lower_gen != trans->transid);
3398
3399         btrfs_set_node_ptr_generation(c, 0, lower_gen);
3400
3401         btrfs_mark_buffer_dirty(c);
3402
3403         old = root->node;
3404         tree_mod_log_set_root_pointer(root, c, 0);
3405         rcu_assign_pointer(root->node, c);
3406
3407         /* the super has an extra ref to root->node */
3408         free_extent_buffer(old);
3409
3410         add_root_to_dirty_list(root);
3411         extent_buffer_get(c);
3412         path->nodes[level] = c;
3413         path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
3414         path->slots[level] = 0;
3415         return 0;
3416 }
3417
3418 /*
3419  * worker function to insert a single pointer in a node.
3420  * the node should have enough room for the pointer already
3421  *
3422  * slot and level indicate where you want the key to go, and
3423  * blocknr is the block the key points to.
3424  */
3425 static void insert_ptr(struct btrfs_trans_handle *trans,
3426                        struct btrfs_fs_info *fs_info, struct btrfs_path *path,
3427                        struct btrfs_disk_key *key, u64 bytenr,
3428                        int slot, int level)
3429 {
3430         struct extent_buffer *lower;
3431         int nritems;
3432         int ret;
3433
3434         BUG_ON(!path->nodes[level]);
3435         btrfs_assert_tree_locked(path->nodes[level]);
3436         lower = path->nodes[level];
3437         nritems = btrfs_header_nritems(lower);
3438         BUG_ON(slot > nritems);
3439         BUG_ON(nritems == BTRFS_NODEPTRS_PER_BLOCK(fs_info));
3440         if (slot != nritems) {
3441                 if (level)
3442                         tree_mod_log_eb_move(fs_info, lower, slot + 1,
3443                                              slot, nritems - slot);
3444                 memmove_extent_buffer(lower,
3445                               btrfs_node_key_ptr_offset(slot + 1),
3446                               btrfs_node_key_ptr_offset(slot),
3447                               (nritems - slot) * sizeof(struct btrfs_key_ptr));
3448         }
3449         if (level) {
3450                 ret = tree_mod_log_insert_key(fs_info, lower, slot,
3451                                               MOD_LOG_KEY_ADD, GFP_NOFS);
3452                 BUG_ON(ret < 0);
3453         }
3454         btrfs_set_node_key(lower, key, slot);
3455         btrfs_set_node_blockptr(lower, slot, bytenr);
3456         WARN_ON(trans->transid == 0);
3457         btrfs_set_node_ptr_generation(lower, slot, trans->transid);
3458         btrfs_set_header_nritems(lower, nritems + 1);
3459         btrfs_mark_buffer_dirty(lower);
3460 }
3461
3462 /*
3463  * split the node at the specified level in path in two.
3464  * The path is corrected to point to the appropriate node after the split
3465  *
3466  * Before splitting this tries to make some room in the node by pushing
3467  * left and right, if either one works, it returns right away.
3468  *
3469  * returns 0 on success and < 0 on failure
3470  */
3471 static noinline int split_node(struct btrfs_trans_handle *trans,
3472                                struct btrfs_root *root,
3473                                struct btrfs_path *path, int level)
3474 {
3475         struct btrfs_fs_info *fs_info = root->fs_info;
3476         struct extent_buffer *c;
3477         struct extent_buffer *split;
3478         struct btrfs_disk_key disk_key;
3479         int mid;
3480         int ret;
3481         u32 c_nritems;
3482
3483         c = path->nodes[level];
3484         WARN_ON(btrfs_header_generation(c) != trans->transid);
3485         if (c == root->node) {
3486                 /*
3487                  * trying to split the root, lets make a new one
3488                  *
3489                  * tree mod log: We don't log_removal old root in
3490                  * insert_new_root, because that root buffer will be kept as a
3491                  * normal node. We are going to log removal of half of the
3492                  * elements below with tree_mod_log_eb_copy. We're holding a
3493                  * tree lock on the buffer, which is why we cannot race with
3494                  * other tree_mod_log users.
3495                  */
3496                 ret = insert_new_root(trans, root, path, level + 1);
3497                 if (ret)
3498                         return ret;
3499         } else {
3500                 ret = push_nodes_for_insert(trans, root, path, level);
3501                 c = path->nodes[level];
3502                 if (!ret && btrfs_header_nritems(c) <
3503                     BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 3)
3504                         return 0;
3505                 if (ret < 0)
3506                         return ret;
3507         }
3508
3509         c_nritems = btrfs_header_nritems(c);
3510         mid = (c_nritems + 1) / 2;
3511         btrfs_node_key(c, &disk_key, mid);
3512
3513         split = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
3514                         &disk_key, level, c->start, 0);
3515         if (IS_ERR(split))
3516                 return PTR_ERR(split);
3517
3518         root_add_used(root, fs_info->nodesize);
3519
3520         memzero_extent_buffer(split, 0, sizeof(struct btrfs_header));
3521         btrfs_set_header_level(split, btrfs_header_level(c));
3522         btrfs_set_header_bytenr(split, split->start);
3523         btrfs_set_header_generation(split, trans->transid);
3524         btrfs_set_header_backref_rev(split, BTRFS_MIXED_BACKREF_REV);
3525         btrfs_set_header_owner(split, root->root_key.objectid);
3526         write_extent_buffer_fsid(split, fs_info->fsid);
3527         write_extent_buffer_chunk_tree_uuid(split, fs_info->chunk_tree_uuid);
3528
3529         ret = tree_mod_log_eb_copy(fs_info, split, c, 0, mid, c_nritems - mid);
3530         if (ret) {
3531                 btrfs_abort_transaction(trans, ret);
3532                 return ret;
3533         }
3534         copy_extent_buffer(split, c,
3535                            btrfs_node_key_ptr_offset(0),
3536                            btrfs_node_key_ptr_offset(mid),
3537                            (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
3538         btrfs_set_header_nritems(split, c_nritems - mid);
3539         btrfs_set_header_nritems(c, mid);
3540         ret = 0;
3541
3542         btrfs_mark_buffer_dirty(c);
3543         btrfs_mark_buffer_dirty(split);
3544
3545         insert_ptr(trans, fs_info, path, &disk_key, split->start,
3546                    path->slots[level + 1] + 1, level + 1);
3547
3548         if (path->slots[level] >= mid) {
3549                 path->slots[level] -= mid;
3550                 btrfs_tree_unlock(c);
3551                 free_extent_buffer(c);
3552                 path->nodes[level] = split;
3553                 path->slots[level + 1] += 1;
3554         } else {
3555                 btrfs_tree_unlock(split);
3556                 free_extent_buffer(split);
3557         }
3558         return ret;
3559 }
3560
3561 /*
3562  * how many bytes are required to store the items in a leaf.  start
3563  * and nr indicate which items in the leaf to check.  This totals up the
3564  * space used both by the item structs and the item data
3565  */
3566 static int leaf_space_used(struct extent_buffer *l, int start, int nr)
3567 {
3568         struct btrfs_item *start_item;
3569         struct btrfs_item *end_item;
3570         struct btrfs_map_token token;
3571         int data_len;
3572         int nritems = btrfs_header_nritems(l);
3573         int end = min(nritems, start + nr) - 1;
3574
3575         if (!nr)
3576                 return 0;
3577         btrfs_init_map_token(&token);
3578         start_item = btrfs_item_nr(start);
3579         end_item = btrfs_item_nr(end);
3580         data_len = btrfs_token_item_offset(l, start_item, &token) +
3581                 btrfs_token_item_size(l, start_item, &token);
3582         data_len = data_len - btrfs_token_item_offset(l, end_item, &token);
3583         data_len += sizeof(struct btrfs_item) * nr;
3584         WARN_ON(data_len < 0);
3585         return data_len;
3586 }
3587
3588 /*
3589  * The space between the end of the leaf items and
3590  * the start of the leaf data.  IOW, how much room
3591  * the leaf has left for both items and data
3592  */
3593 noinline int btrfs_leaf_free_space(struct btrfs_fs_info *fs_info,
3594                                    struct extent_buffer *leaf)
3595 {
3596         int nritems = btrfs_header_nritems(leaf);
3597         int ret;
3598
3599         ret = BTRFS_LEAF_DATA_SIZE(fs_info) - leaf_space_used(leaf, 0, nritems);
3600         if (ret < 0) {
3601                 btrfs_crit(fs_info,
3602                            "leaf free space ret %d, leaf data size %lu, used %d nritems %d",
3603                            ret,
3604                            (unsigned long) BTRFS_LEAF_DATA_SIZE(fs_info),
3605                            leaf_space_used(leaf, 0, nritems), nritems);
3606         }
3607         return ret;
3608 }
3609
3610 /*
3611  * min slot controls the lowest index we're willing to push to the
3612  * right.  We'll push up to and including min_slot, but no lower
3613  */
3614 static noinline int __push_leaf_right(struct btrfs_fs_info *fs_info,
3615                                       struct btrfs_path *path,
3616                                       int data_size, int empty,
3617                                       struct extent_buffer *right,
3618                                       int free_space, u32 left_nritems,
3619                                       u32 min_slot)
3620 {
3621         struct extent_buffer *left = path->nodes[0];
3622         struct extent_buffer *upper = path->nodes[1];
3623         struct btrfs_map_token token;
3624         struct btrfs_disk_key disk_key;
3625         int slot;
3626         u32 i;
3627         int push_space = 0;
3628         int push_items = 0;
3629         struct btrfs_item *item;
3630         u32 nr;
3631         u32 right_nritems;
3632         u32 data_end;
3633         u32 this_item_size;
3634
3635         btrfs_init_map_token(&token);
3636
3637         if (empty)
3638                 nr = 0;
3639         else
3640                 nr = max_t(u32, 1, min_slot);
3641
3642         if (path->slots[0] >= left_nritems)
3643                 push_space += data_size;
3644
3645         slot = path->slots[1];
3646         i = left_nritems - 1;
3647         while (i >= nr) {
3648                 item = btrfs_item_nr(i);
3649
3650                 if (!empty && push_items > 0) {
3651                         if (path->slots[0] > i)
3652                                 break;
3653                         if (path->slots[0] == i) {
3654                                 int space = btrfs_leaf_free_space(fs_info, left);
3655                                 if (space + push_space * 2 > free_space)
3656                                         break;
3657                         }
3658                 }
3659
3660                 if (path->slots[0] == i)
3661                         push_space += data_size;
3662
3663                 this_item_size = btrfs_item_size(left, item);
3664                 if (this_item_size + sizeof(*item) + push_space > free_space)
3665                         break;
3666
3667                 push_items++;
3668                 push_space += this_item_size + sizeof(*item);
3669                 if (i == 0)
3670                         break;
3671                 i--;
3672         }
3673
3674         if (push_items == 0)
3675                 goto out_unlock;
3676
3677         WARN_ON(!empty && push_items == left_nritems);
3678
3679         /* push left to right */
3680         right_nritems = btrfs_header_nritems(right);
3681
3682         push_space = btrfs_item_end_nr(left, left_nritems - push_items);
3683         push_space -= leaf_data_end(fs_info, left);
3684
3685         /* make room in the right data area */
3686         data_end = leaf_data_end(fs_info, right);
3687         memmove_extent_buffer(right,
3688                               BTRFS_LEAF_DATA_OFFSET + data_end - push_space,
3689                               BTRFS_LEAF_DATA_OFFSET + data_end,
3690                               BTRFS_LEAF_DATA_SIZE(fs_info) - data_end);
3691
3692         /* copy from the left data area */
3693         copy_extent_buffer(right, left, BTRFS_LEAF_DATA_OFFSET +
3694                      BTRFS_LEAF_DATA_SIZE(fs_info) - push_space,
3695                      BTRFS_LEAF_DATA_OFFSET + leaf_data_end(fs_info, left),
3696                      push_space);
3697
3698         memmove_extent_buffer(right, btrfs_item_nr_offset(push_items),
3699                               btrfs_item_nr_offset(0),
3700                               right_nritems * sizeof(struct btrfs_item));
3701
3702         /* copy the items from left to right */
3703         copy_extent_buffer(right, left, btrfs_item_nr_offset(0),
3704                    btrfs_item_nr_offset(left_nritems - push_items),
3705                    push_items * sizeof(struct btrfs_item));
3706
3707         /* update the item pointers */
3708         right_nritems += push_items;
3709         btrfs_set_header_nritems(right, right_nritems);
3710         push_space = BTRFS_LEAF_DATA_SIZE(fs_info);
3711         for (i = 0; i < right_nritems; i++) {
3712                 item = btrfs_item_nr(i);
3713                 push_space -= btrfs_token_item_size(right, item, &token);
3714                 btrfs_set_token_item_offset(right, item, push_space, &token);
3715         }
3716
3717         left_nritems -= push_items;
3718         btrfs_set_header_nritems(left, left_nritems);
3719
3720         if (left_nritems)
3721                 btrfs_mark_buffer_dirty(left);
3722         else
3723                 clean_tree_block(fs_info, left);
3724
3725         btrfs_mark_buffer_dirty(right);
3726
3727         btrfs_item_key(right, &disk_key, 0);
3728         btrfs_set_node_key(upper, &disk_key, slot + 1);
3729         btrfs_mark_buffer_dirty(upper);
3730
3731         /* then fixup the leaf pointer in the path */
3732         if (path->slots[0] >= left_nritems) {
3733                 path->slots[0] -= left_nritems;
3734                 if (btrfs_header_nritems(path->nodes[0]) == 0)
3735                         clean_tree_block(fs_info, path->nodes[0]);
3736                 btrfs_tree_unlock(path->nodes[0]);
3737                 free_extent_buffer(path->nodes[0]);
3738                 path->nodes[0] = right;
3739                 path->slots[1] += 1;
3740         } else {
3741                 btrfs_tree_unlock(right);
3742                 free_extent_buffer(right);
3743         }
3744         return 0;
3745
3746 out_unlock:
3747         btrfs_tree_unlock(right);
3748         free_extent_buffer(right);
3749         return 1;
3750 }
3751
3752 /*
3753  * push some data in the path leaf to the right, trying to free up at
3754  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3755  *
3756  * returns 1 if the push failed because the other node didn't have enough
3757  * room, 0 if everything worked out and < 0 if there were major errors.
3758  *
3759  * this will push starting from min_slot to the end of the leaf.  It won't
3760  * push any slot lower than min_slot
3761  */
3762 static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
3763                            *root, struct btrfs_path *path,
3764                            int min_data_size, int data_size,
3765                            int empty, u32 min_slot)
3766 {
3767         struct btrfs_fs_info *fs_info = root->fs_info;
3768         struct extent_buffer *left = path->nodes[0];
3769         struct extent_buffer *right;
3770         struct extent_buffer *upper;
3771         int slot;
3772         int free_space;
3773         u32 left_nritems;
3774         int ret;
3775
3776         if (!path->nodes[1])
3777                 return 1;
3778
3779         slot = path->slots[1];
3780         upper = path->nodes[1];
3781         if (slot >= btrfs_header_nritems(upper) - 1)
3782                 return 1;
3783
3784         btrfs_assert_tree_locked(path->nodes[1]);
3785
3786         right = read_node_slot(fs_info, upper, slot + 1);
3787         /*
3788          * slot + 1 is not valid or we fail to read the right node,
3789          * no big deal, just return.
3790          */
3791         if (IS_ERR(right))
3792                 return 1;
3793
3794         btrfs_tree_lock(right);
3795         btrfs_set_lock_blocking(right);
3796
3797         free_space = btrfs_leaf_free_space(fs_info, right);
3798         if (free_space < data_size)
3799                 goto out_unlock;
3800
3801         /* cow and double check */
3802         ret = btrfs_cow_block(trans, root, right, upper,
3803                               slot + 1, &right);
3804         if (ret)
3805                 goto out_unlock;
3806
3807         free_space = btrfs_leaf_free_space(fs_info, right);
3808         if (free_space < data_size)
3809                 goto out_unlock;
3810
3811         left_nritems = btrfs_header_nritems(left);
3812         if (left_nritems == 0)
3813                 goto out_unlock;
3814
3815         if (path->slots[0] == left_nritems && !empty) {
3816                 /* Key greater than all keys in the leaf, right neighbor has
3817                  * enough room for it and we're not emptying our leaf to delete
3818                  * it, therefore use right neighbor to insert the new item and
3819                  * no need to touch/dirty our left leaft. */
3820                 btrfs_tree_unlock(left);
3821                 free_extent_buffer(left);
3822                 path->nodes[0] = right;
3823                 path->slots[0] = 0;
3824                 path->slots[1]++;
3825                 return 0;
3826         }
3827
3828         return __push_leaf_right(fs_info, path, min_data_size, empty,
3829                                 right, free_space, left_nritems, min_slot);
3830 out_unlock:
3831         btrfs_tree_unlock(right);
3832         free_extent_buffer(right);
3833         return 1;
3834 }
3835
3836 /*
3837  * push some data in the path leaf to the left, trying to free up at
3838  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3839  *
3840  * max_slot can put a limit on how far into the leaf we'll push items.  The
3841  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us do all the
3842  * items
3843  */
3844 static noinline int __push_leaf_left(struct btrfs_fs_info *fs_info,
3845                                      struct btrfs_path *path, int data_size,
3846                                      int empty, struct extent_buffer *left,
3847                                      int free_space, u32 right_nritems,
3848                                      u32 max_slot)
3849 {
3850         struct btrfs_disk_key disk_key;
3851         struct extent_buffer *right = path->nodes[0];
3852         int i;
3853         int push_space = 0;
3854         int push_items = 0;
3855         struct btrfs_item *item;
3856         u32 old_left_nritems;
3857         u32 nr;
3858         int ret = 0;
3859         u32 this_item_size;
3860         u32 old_left_item_size;
3861         struct btrfs_map_token token;
3862
3863         btrfs_init_map_token(&token);
3864
3865         if (empty)
3866                 nr = min(right_nritems, max_slot);
3867         else
3868                 nr = min(right_nritems - 1, max_slot);
3869
3870         for (i = 0; i < nr; i++) {
3871                 item = btrfs_item_nr(i);
3872
3873                 if (!empty && push_items > 0) {
3874                         if (path->slots[0] < i)
3875                                 break;
3876                         if (path->slots[0] == i) {
3877                                 int space = btrfs_leaf_free_space(fs_info, right);
3878                                 if (space + push_space * 2 > free_space)
3879                                         break;
3880                         }
3881                 }
3882
3883                 if (path->slots[0] == i)
3884                         push_space += data_size;
3885
3886                 this_item_size = btrfs_item_size(right, item);
3887                 if (this_item_size + sizeof(*item) + push_space > free_space)
3888                         break;
3889
3890                 push_items++;
3891                 push_space += this_item_size + sizeof(*item);
3892         }
3893
3894         if (push_items == 0) {
3895                 ret = 1;
3896                 goto out;
3897         }
3898         WARN_ON(!empty && push_items == btrfs_header_nritems(right));
3899
3900         /* push data from right to left */
3901         copy_extent_buffer(left, right,
3902                            btrfs_item_nr_offset(btrfs_header_nritems(left)),
3903                            btrfs_item_nr_offset(0),
3904                            push_items * sizeof(struct btrfs_item));
3905
3906         push_space = BTRFS_LEAF_DATA_SIZE(fs_info) -
3907                      btrfs_item_offset_nr(right, push_items - 1);
3908
3909         copy_extent_buffer(left, right, BTRFS_LEAF_DATA_OFFSET +
3910                      leaf_data_end(fs_info, left) - push_space,
3911                      BTRFS_LEAF_DATA_OFFSET +
3912                      btrfs_item_offset_nr(right, push_items - 1),
3913                      push_space);
3914         old_left_nritems = btrfs_header_nritems(left);
3915         BUG_ON(old_left_nritems <= 0);
3916
3917         old_left_item_size = btrfs_item_offset_nr(left, old_left_nritems - 1);
3918         for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
3919                 u32 ioff;
3920
3921                 item = btrfs_item_nr(i);
3922
3923                 ioff = btrfs_token_item_offset(left, item, &token);
3924                 btrfs_set_token_item_offset(left, item,
3925                       ioff - (BTRFS_LEAF_DATA_SIZE(fs_info) - old_left_item_size),
3926                       &token);
3927         }
3928         btrfs_set_header_nritems(left, old_left_nritems + push_items);
3929
3930         /* fixup right node */
3931         if (push_items > right_nritems)
3932                 WARN(1, KERN_CRIT "push items %d nr %u\n", push_items,
3933                        right_nritems);
3934
3935         if (push_items < right_nritems) {
3936                 push_space = btrfs_item_offset_nr(right, push_items - 1) -
3937                                                   leaf_data_end(fs_info, right);
3938                 memmove_extent_buffer(right, BTRFS_LEAF_DATA_OFFSET +
3939                                       BTRFS_LEAF_DATA_SIZE(fs_info) - push_space,
3940                                       BTRFS_LEAF_DATA_OFFSET +
3941                                       leaf_data_end(fs_info, right), push_space);
3942
3943                 memmove_extent_buffer(right, btrfs_item_nr_offset(0),
3944                               btrfs_item_nr_offset(push_items),
3945                              (btrfs_header_nritems(right) - push_items) *
3946                              sizeof(struct btrfs_item));
3947         }
3948         right_nritems -= push_items;
3949         btrfs_set_header_nritems(right, right_nritems);
3950         push_space = BTRFS_LEAF_DATA_SIZE(fs_info);
3951         for (i = 0; i < right_nritems; i++) {
3952                 item = btrfs_item_nr(i);
3953
3954                 push_space = push_space - btrfs_token_item_size(right,
3955                                                                 item, &token);
3956                 btrfs_set_token_item_offset(right, item, push_space, &token);
3957         }
3958
3959         btrfs_mark_buffer_dirty(left);
3960         if (right_nritems)
3961                 btrfs_mark_buffer_dirty(right);
3962         else
3963                 clean_tree_block(fs_info, right);
3964
3965         btrfs_item_key(right, &disk_key, 0);
3966         fixup_low_keys(fs_info, path, &disk_key, 1);
3967
3968         /* then fixup the leaf pointer in the path */
3969         if (path->slots[0] < push_items) {
3970                 path->slots[0] += old_left_nritems;
3971                 btrfs_tree_unlock(path->nodes[0]);
3972                 free_extent_buffer(path->nodes[0]);
3973                 path->nodes[0] = left;
3974                 path->slots[1] -= 1;
3975         } else {
3976                 btrfs_tree_unlock(left);
3977                 free_extent_buffer(left);
3978                 path->slots[0] -= push_items;
3979         }
3980         BUG_ON(path->slots[0] < 0);
3981         return ret;
3982 out:
3983         btrfs_tree_unlock(left);
3984         free_extent_buffer(left);
3985         return ret;
3986 }
3987
3988 /*
3989  * push some data in the path leaf to the left, trying to free up at
3990  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3991  *
3992  * max_slot can put a limit on how far into the leaf we'll push items.  The
3993  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us push all the
3994  * items
3995  */
3996 static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
3997                           *root, struct btrfs_path *path, int min_data_size,
3998                           int data_size, int empty, u32 max_slot)
3999 {
4000         struct btrfs_fs_info *fs_info = root->fs_info;
4001         struct extent_buffer *right = path->nodes[0];
4002         struct extent_buffer *left;
4003         int slot;
4004         int free_space;
4005         u32 right_nritems;
4006         int ret = 0;
4007
4008         slot = path->slots[1];
4009         if (slot == 0)
4010                 return 1;
4011         if (!path->nodes[1])
4012                 return 1;
4013
4014         right_nritems = btrfs_header_nritems(right);
4015         if (right_nritems == 0)
4016                 return 1;
4017
4018         btrfs_assert_tree_locked(path->nodes[1]);
4019
4020         left = read_node_slot(fs_info, path->nodes[1], slot - 1);
4021         /*
4022          * slot - 1 is not valid or we fail to read the left node,
4023          * no big deal, just return.
4024          */
4025         if (IS_ERR(left))
4026                 return 1;
4027
4028         btrfs_tree_lock(left);
4029         btrfs_set_lock_blocking(left);
4030
4031         free_space = btrfs_leaf_free_space(fs_info, left);
4032         if (free_space < data_size) {
4033                 ret = 1;
4034                 goto out;
4035         }
4036
4037         /* cow and double check */
4038         ret = btrfs_cow_block(trans, root, left,
4039                               path->nodes[1], slot - 1, &left);
4040         if (ret) {
4041                 /* we hit -ENOSPC, but it isn't fatal here */
4042                 if (ret == -ENOSPC)
4043                         ret = 1;
4044                 goto out;
4045         }
4046
4047         free_space = btrfs_leaf_free_space(fs_info, left);
4048         if (free_space < data_size) {
4049                 ret = 1;
4050                 goto out;
4051         }
4052
4053         return __push_leaf_left(fs_info, path, min_data_size,
4054                                empty, left, free_space, right_nritems,
4055                                max_slot);
4056 out:
4057         btrfs_tree_unlock(left);
4058         free_extent_buffer(left);
4059         return ret;
4060 }
4061
4062 /*
4063  * split the path's leaf in two, making sure there is at least data_size
4064  * available for the resulting leaf level of the path.
4065  */
4066 static noinline void copy_for_split(struct btrfs_trans_handle *trans,
4067                                     struct btrfs_fs_info *fs_info,
4068                                     struct btrfs_path *path,
4069                                     struct extent_buffer *l,
4070                                     struct extent_buffer *right,
4071                                     int slot, int mid, int nritems)
4072 {
4073         int data_copy_size;
4074         int rt_data_off;
4075         int i;
4076         struct btrfs_disk_key disk_key;
4077         struct btrfs_map_token token;
4078
4079         btrfs_init_map_token(&token);
4080
4081         nritems = nritems - mid;
4082         btrfs_set_header_nritems(right, nritems);
4083         data_copy_size = btrfs_item_end_nr(l, mid) - leaf_data_end(fs_info, l);
4084
4085         copy_extent_buffer(right, l, btrfs_item_nr_offset(0),
4086                            btrfs_item_nr_offset(mid),
4087                            nritems * sizeof(struct btrfs_item));
4088
4089         copy_extent_buffer(right, l,
4090                      BTRFS_LEAF_DATA_OFFSET + BTRFS_LEAF_DATA_SIZE(fs_info) -
4091                      data_copy_size, BTRFS_LEAF_DATA_OFFSET +
4092                      leaf_data_end(fs_info, l), data_copy_size);
4093
4094         rt_data_off = BTRFS_LEAF_DATA_SIZE(fs_info) - btrfs_item_end_nr(l, mid);
4095
4096         for (i = 0; i < nritems; i++) {
4097                 struct btrfs_item *item = btrfs_item_nr(i);
4098                 u32 ioff;
4099
4100                 ioff = btrfs_token_item_offset(right, item, &token);
4101                 btrfs_set_token_item_offset(right, item,
4102                                             ioff + rt_data_off, &token);
4103         }
4104
4105         btrfs_set_header_nritems(l, mid);
4106         btrfs_item_key(right, &disk_key, 0);
4107         insert_ptr(trans, fs_info, path, &disk_key, right->start,
4108                    path->slots[1] + 1, 1);
4109
4110         btrfs_mark_buffer_dirty(right);
4111         btrfs_mark_buffer_dirty(l);
4112         BUG_ON(path->slots[0] != slot);
4113
4114         if (mid <= slot) {
4115                 btrfs_tree_unlock(path->nodes[0]);
4116                 free_extent_buffer(path->nodes[0]);
4117                 path->nodes[0] = right;
4118                 path->slots[0] -= mid;
4119                 path->slots[1] += 1;
4120         } else {
4121                 btrfs_tree_unlock(right);
4122                 free_extent_buffer(right);
4123         }
4124
4125         BUG_ON(path->slots[0] < 0);
4126 }
4127
4128 /*
4129  * double splits happen when we need to insert a big item in the middle
4130  * of a leaf.  A double split can leave us with 3 mostly empty leaves:
4131  * leaf: [ slots 0 - N] [ our target ] [ N + 1 - total in leaf ]
4132  *          A                 B                 C
4133  *
4134  * We avoid this by trying to push the items on either side of our target
4135  * into the adjacent leaves.  If all goes well we can avoid the double split
4136  * completely.
4137  */
4138 static noinline int push_for_double_split(struct btrfs_trans_handle *trans,
4139                                           struct btrfs_root *root,
4140                                           struct btrfs_path *path,
4141                                           int data_size)
4142 {
4143         struct btrfs_fs_info *fs_info = root->fs_info;
4144         int ret;
4145         int progress = 0;
4146         int slot;
4147         u32 nritems;
4148         int space_needed = data_size;
4149
4150         slot = path->slots[0];
4151         if (slot < btrfs_header_nritems(path->nodes[0]))
4152                 space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
4153
4154         /*
4155          * try to push all the items after our slot into the
4156          * right leaf
4157          */
4158         ret = push_leaf_right(trans, root, path, 1, space_needed, 0, slot);
4159         if (ret < 0)
4160                 return ret;
4161
4162         if (ret == 0)
4163                 progress++;
4164
4165         nritems = btrfs_header_nritems(path->nodes[0]);
4166         /*
4167          * our goal is to get our slot at the start or end of a leaf.  If
4168          * we've done so we're done
4169          */
4170         if (path->slots[0] == 0 || path->slots[0] == nritems)
4171                 return 0;
4172
4173         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= data_size)
4174                 return 0;
4175
4176         /* try to push all the items before our slot into the next leaf */
4177         slot = path->slots[0];
4178         space_needed = data_size;
4179         if (slot > 0)
4180                 space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
4181         ret = push_leaf_left(trans, root, path, 1, space_needed, 0, slot);
4182         if (ret < 0)
4183                 return ret;
4184
4185         if (ret == 0)
4186                 progress++;
4187
4188         if (progress)
4189                 return 0;
4190         return 1;
4191 }
4192
4193 /*
4194  * split the path's leaf in two, making sure there is at least data_size
4195  * available for the resulting leaf level of the path.
4196  *
4197  * returns 0 if all went well and < 0 on failure.
4198  */
4199 static noinline int split_leaf(struct btrfs_trans_handle *trans,
4200                                struct btrfs_root *root,
4201                                const struct btrfs_key *ins_key,
4202                                struct btrfs_path *path, int data_size,
4203                                int extend)
4204 {
4205         struct btrfs_disk_key disk_key;
4206         struct extent_buffer *l;
4207         u32 nritems;
4208         int mid;
4209         int slot;
4210         struct extent_buffer *right;
4211         struct btrfs_fs_info *fs_info = root->fs_info;
4212         int ret = 0;
4213         int wret;
4214         int split;
4215         int num_doubles = 0;
4216         int tried_avoid_double = 0;
4217
4218         l = path->nodes[0];
4219         slot = path->slots[0];
4220         if (extend && data_size + btrfs_item_size_nr(l, slot) +
4221             sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(fs_info))
4222                 return -EOVERFLOW;
4223
4224         /* first try to make some room by pushing left and right */
4225         if (data_size && path->nodes[1]) {
4226                 int space_needed = data_size;
4227
4228                 if (slot < btrfs_header_nritems(l))
4229                         space_needed -= btrfs_leaf_free_space(fs_info, l);
4230
4231                 wret = push_leaf_right(trans, root, path, space_needed,
4232                                        space_needed, 0, 0);
4233                 if (wret < 0)
4234                         return wret;
4235                 if (wret) {
4236                         space_needed = data_size;
4237                         if (slot > 0)
4238                                 space_needed -= btrfs_leaf_free_space(fs_info,
4239                                                                       l);
4240                         wret = push_leaf_left(trans, root, path, space_needed,
4241                                               space_needed, 0, (u32)-1);
4242                         if (wret < 0)
4243                                 return wret;
4244                 }
4245                 l = path->nodes[0];
4246
4247                 /* did the pushes work? */
4248                 if (btrfs_leaf_free_space(fs_info, l) >= data_size)
4249                         return 0;
4250         }
4251
4252         if (!path->nodes[1]) {
4253                 ret = insert_new_root(trans, root, path, 1);
4254                 if (ret)
4255                         return ret;
4256         }
4257 again:
4258         split = 1;
4259         l = path->nodes[0];
4260         slot = path->slots[0];
4261         nritems = btrfs_header_nritems(l);
4262         mid = (nritems + 1) / 2;
4263
4264         if (mid <= slot) {
4265                 if (nritems == 1 ||
4266                     leaf_space_used(l, mid, nritems - mid) + data_size >
4267                         BTRFS_LEAF_DATA_SIZE(fs_info)) {
4268                         if (slot >= nritems) {
4269                                 split = 0;
4270                         } else {
4271                                 mid = slot;
4272                                 if (mid != nritems &&
4273                                     leaf_space_used(l, mid, nritems - mid) +
4274                                     data_size > BTRFS_LEAF_DATA_SIZE(fs_info)) {
4275                                         if (data_size && !tried_avoid_double)
4276                                                 goto push_for_double;
4277                                         split = 2;
4278                                 }
4279                         }
4280                 }
4281         } else {
4282                 if (leaf_space_used(l, 0, mid) + data_size >
4283                         BTRFS_LEAF_DATA_SIZE(fs_info)) {
4284                         if (!extend && data_size && slot == 0) {
4285                                 split = 0;
4286                         } else if ((extend || !data_size) && slot == 0) {
4287                                 mid = 1;
4288                         } else {
4289                                 mid = slot;
4290                                 if (mid != nritems &&
4291                                     leaf_space_used(l, mid, nritems - mid) +
4292                                     data_size > BTRFS_LEAF_DATA_SIZE(fs_info)) {
4293                                         if (data_size && !tried_avoid_double)
4294                                                 goto push_for_double;
4295                                         split = 2;
4296                                 }
4297                         }
4298                 }
4299         }
4300
4301         if (split == 0)
4302                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
4303         else
4304                 btrfs_item_key(l, &disk_key, mid);
4305
4306         right = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
4307                         &disk_key, 0, l->start, 0);
4308         if (IS_ERR(right))
4309                 return PTR_ERR(right);
4310
4311         root_add_used(root, fs_info->nodesize);
4312
4313         memzero_extent_buffer(right, 0, sizeof(struct btrfs_header));
4314         btrfs_set_header_bytenr(right, right->start);
4315         btrfs_set_header_generation(right, trans->transid);
4316         btrfs_set_header_backref_rev(right, BTRFS_MIXED_BACKREF_REV);
4317         btrfs_set_header_owner(right, root->root_key.objectid);
4318         btrfs_set_header_level(right, 0);
4319         write_extent_buffer_fsid(right, fs_info->fsid);
4320         write_extent_buffer_chunk_tree_uuid(right, fs_info->chunk_tree_uuid);
4321
4322         if (split == 0) {
4323                 if (mid <= slot) {
4324                         btrfs_set_header_nritems(right, 0);
4325                         insert_ptr(trans, fs_info, path, &disk_key,
4326                                    right->start, path->slots[1] + 1, 1);
4327                         btrfs_tree_unlock(path->nodes[0]);
4328                         free_extent_buffer(path->nodes[0]);
4329                         path->nodes[0] = right;
4330                         path->slots[0] = 0;
4331                         path->slots[1] += 1;
4332                 } else {
4333                         btrfs_set_header_nritems(right, 0);
4334                         insert_ptr(trans, fs_info, path, &disk_key,
4335                                    right->start, path->slots[1], 1);
4336                         btrfs_tree_unlock(path->nodes[0]);
4337                         free_extent_buffer(path->nodes[0]);
4338                         path->nodes[0] = right;
4339                         path->slots[0] = 0;
4340                         if (path->slots[1] == 0)
4341                                 fixup_low_keys(fs_info, path, &disk_key, 1);
4342                 }
4343                 /*
4344                  * We create a new leaf 'right' for the required ins_len and
4345                  * we'll do btrfs_mark_buffer_dirty() on this leaf after copying
4346                  * the content of ins_len to 'right'.
4347                  */
4348                 return ret;
4349         }
4350
4351         copy_for_split(trans, fs_info, path, l, right, slot, mid, nritems);
4352
4353         if (split == 2) {
4354                 BUG_ON(num_doubles != 0);
4355                 num_doubles++;
4356                 goto again;
4357         }
4358
4359         return 0;
4360
4361 push_for_double:
4362         push_for_double_split(trans, root, path, data_size);
4363         tried_avoid_double = 1;
4364         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= data_size)
4365                 return 0;
4366         goto again;
4367 }
4368
4369 static noinline int setup_leaf_for_split(struct btrfs_trans_handle *trans,
4370                                          struct btrfs_root *root,
4371                                          struct btrfs_path *path, int ins_len)
4372 {
4373         struct btrfs_fs_info *fs_info = root->fs_info;
4374         struct btrfs_key key;
4375         struct extent_buffer *leaf;
4376         struct btrfs_file_extent_item *fi;
4377         u64 extent_len = 0;
4378         u32 item_size;
4379         int ret;
4380
4381         leaf = path->nodes[0];
4382         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4383
4384         BUG_ON(key.type != BTRFS_EXTENT_DATA_KEY &&
4385                key.type != BTRFS_EXTENT_CSUM_KEY);
4386
4387         if (btrfs_leaf_free_space(fs_info, leaf) >= ins_len)
4388                 return 0;
4389
4390         item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4391         if (key.type == BTRFS_EXTENT_DATA_KEY) {
4392                 fi = btrfs_item_ptr(leaf, path->slots[0],
4393                                     struct btrfs_file_extent_item);
4394                 extent_len = btrfs_file_extent_num_bytes(leaf, fi);
4395         }
4396         btrfs_release_path(path);
4397
4398         path->keep_locks = 1;
4399         path->search_for_split = 1;
4400         ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
4401         path->search_for_split = 0;
4402         if (ret > 0)
4403                 ret = -EAGAIN;
4404         if (ret < 0)
4405                 goto err;
4406
4407         ret = -EAGAIN;
4408         leaf = path->nodes[0];
4409         /* if our item isn't there, return now */
4410         if (item_size != btrfs_item_size_nr(leaf, path->slots[0]))
4411                 goto err;
4412
4413         /* the leaf has  changed, it now has room.  return now */
4414         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= ins_len)
4415                 goto err;
4416
4417         if (key.type == BTRFS_EXTENT_DATA_KEY) {
4418                 fi = btrfs_item_ptr(leaf, path->slots[0],
4419                                     struct btrfs_file_extent_item);
4420                 if (extent_len != btrfs_file_extent_num_bytes(leaf, fi))
4421                         goto err;
4422         }
4423
4424         btrfs_set_path_blocking(path);
4425         ret = split_leaf(trans, root, &key, path, ins_len, 1);
4426         if (ret)
4427                 goto err;
4428
4429         path->keep_locks = 0;
4430         btrfs_unlock_up_safe(path, 1);
4431         return 0;
4432 err:
4433         path->keep_locks = 0;
4434         return ret;
4435 }
4436
4437 static noinline int split_item(struct btrfs_fs_info *fs_info,
4438                                struct btrfs_path *path,
4439                                const struct btrfs_key *new_key,
4440                                unsigned long split_offset)
4441 {
4442         struct extent_buffer *leaf;
4443         struct btrfs_item *item;
4444         struct btrfs_item *new_item;
4445         int slot;
4446         char *buf;
4447         u32 nritems;
4448         u32 item_size;
4449         u32 orig_offset;
4450         struct btrfs_disk_key disk_key;
4451
4452         leaf = path->nodes[0];
4453         BUG_ON(btrfs_leaf_free_space(fs_info, leaf) < sizeof(struct btrfs_item));
4454
4455         btrfs_set_path_blocking(path);
4456
4457         item = btrfs_item_nr(path->slots[0]);
4458         orig_offset = btrfs_item_offset(leaf, item);
4459         item_size = btrfs_item_size(leaf, item);
4460
4461         buf = kmalloc(item_size, GFP_NOFS);
4462         if (!buf)
4463                 return -ENOMEM;
4464
4465         read_extent_buffer(leaf, buf, btrfs_item_ptr_offset(leaf,
4466                             path->slots[0]), item_size);
4467
4468         slot = path->slots[0] + 1;
4469         nritems = btrfs_header_nritems(leaf);
4470         if (slot != nritems) {
4471                 /* shift the items */
4472                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + 1),
4473                                 btrfs_item_nr_offset(slot),
4474                                 (nritems - slot) * sizeof(struct btrfs_item));
4475         }
4476
4477         btrfs_cpu_key_to_disk(&disk_key, new_key);
4478         btrfs_set_item_key(leaf, &disk_key, slot);
4479
4480         new_item = btrfs_item_nr(slot);
4481
4482         btrfs_set_item_offset(leaf, new_item, orig_offset);
4483         btrfs_set_item_size(leaf, new_item, item_size - split_offset);
4484
4485         btrfs_set_item_offset(leaf, item,
4486                               orig_offset + item_size - split_offset);
4487         btrfs_set_item_size(leaf, item, split_offset);
4488
4489         btrfs_set_header_nritems(leaf, nritems + 1);
4490
4491         /* write the data for the start of the original item */
4492         write_extent_buffer(leaf, buf,
4493                             btrfs_item_ptr_offset(leaf, path->slots[0]),
4494                             split_offset);
4495
4496         /* write the data for the new item */
4497         write_extent_buffer(leaf, buf + split_offset,
4498                             btrfs_item_ptr_offset(leaf, slot),
4499                             item_size - split_offset);
4500         btrfs_mark_buffer_dirty(leaf);
4501
4502         BUG_ON(btrfs_leaf_free_space(fs_info, leaf) < 0);
4503         kfree(buf);
4504         return 0;
4505 }
4506
4507 /*
4508  * This function splits a single item into two items,
4509  * giving 'new_key' to the new item and splitting the
4510  * old one at split_offset (from the start of the item).
4511  *
4512  * The path may be released by this operation.  After
4513  * the split, the path is pointing to the old item.  The
4514  * new item is going to be in the same node as the old one.
4515  *
4516  * Note, the item being split must be smaller enough to live alone on
4517  * a tree block with room for one extra struct btrfs_item
4518  *
4519  * This allows us to split the item in place, keeping a lock on the
4520  * leaf the entire time.
4521  */
4522 int btrfs_split_item(struct btrfs_trans_handle *trans,
4523                      struct btrfs_root *root,
4524                      struct btrfs_path *path,
4525                      const struct btrfs_key *new_key,
4526                      unsigned long split_offset)
4527 {
4528         int ret;
4529         ret = setup_leaf_for_split(trans, root, path,
4530                                    sizeof(struct btrfs_item));
4531         if (ret)
4532                 return ret;
4533
4534         ret = split_item(root->fs_info, path, new_key, split_offset);
4535         return ret;
4536 }
4537
4538 /*
4539  * This function duplicate a item, giving 'new_key' to the new item.
4540  * It guarantees both items live in the same tree leaf and the new item
4541  * is contiguous with the original item.
4542  *
4543  * This allows us to split file extent in place, keeping a lock on the
4544  * leaf the entire time.
4545  */
4546 int btrfs_duplicate_item(struct btrfs_trans_handle *trans,
4547                          struct btrfs_root *root,
4548                          struct btrfs_path *path,
4549                          const struct btrfs_key *new_key)
4550 {
4551         struct extent_buffer *leaf;
4552         int ret;
4553         u32 item_size;
4554
4555         leaf = path->nodes[0];
4556         item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4557         ret = setup_leaf_for_split(trans, root, path,
4558                                    item_size + sizeof(struct btrfs_item));
4559         if (ret)
4560                 return ret;
4561
4562         path->slots[0]++;
4563         setup_items_for_insert(root, path, new_key, &item_size,
4564                                item_size, item_size +
4565                                sizeof(struct btrfs_item), 1);
4566         leaf = path->nodes[0];
4567         memcpy_extent_buffer(leaf,
4568                              btrfs_item_ptr_offset(leaf, path->slots[0]),
4569                              btrfs_item_ptr_offset(leaf, path->slots[0] - 1),
4570                              item_size);
4571         return 0;
4572 }
4573
4574 /*
4575  * make the item pointed to by the path smaller.  new_size indicates
4576  * how small to make it, and from_end tells us if we just chop bytes
4577  * off the end of the item or if we shift the item to chop bytes off
4578  * the front.
4579  */
4580 void btrfs_truncate_item(struct btrfs_fs_info *fs_info,
4581                          struct btrfs_path *path, u32 new_size, int from_end)
4582 {
4583         int slot;
4584         struct extent_buffer *leaf;
4585         struct btrfs_item *item;
4586         u32 nritems;
4587         unsigned int data_end;
4588         unsigned int old_data_start;
4589         unsigned int old_size;
4590         unsigned int size_diff;
4591         int i;
4592         struct btrfs_map_token token;
4593
4594         btrfs_init_map_token(&token);
4595
4596         leaf = path->nodes[0];
4597         slot = path->slots[0];
4598
4599         old_size = btrfs_item_size_nr(leaf, slot);
4600         if (old_size == new_size)
4601                 return;
4602
4603         nritems = btrfs_header_nritems(leaf);
4604         data_end = leaf_data_end(fs_info, leaf);
4605
4606         old_data_start = btrfs_item_offset_nr(leaf, slot);
4607
4608         size_diff = old_size - new_size;
4609
4610         BUG_ON(slot < 0);
4611         BUG_ON(slot >= nritems);
4612
4613         /*
4614          * item0..itemN ... dataN.offset..dataN.size .. data0.size
4615          */
4616         /* first correct the data pointers */
4617         for (i = slot; i < nritems; i++) {
4618                 u32 ioff;
4619                 item = btrfs_item_nr(i);
4620
4621                 ioff = btrfs_token_item_offset(leaf, item, &token);
4622                 btrfs_set_token_item_offset(leaf, item,
4623                                             ioff + size_diff, &token);
4624         }
4625
4626         /* shift the data */
4627         if (from_end) {
4628                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4629                               data_end + size_diff, BTRFS_LEAF_DATA_OFFSET +
4630                               data_end, old_data_start + new_size - data_end);
4631         } else {
4632                 struct btrfs_disk_key disk_key;
4633                 u64 offset;
4634
4635                 btrfs_item_key(leaf, &disk_key, slot);
4636
4637                 if (btrfs_disk_key_type(&disk_key) == BTRFS_EXTENT_DATA_KEY) {
4638                         unsigned long ptr;
4639                         struct btrfs_file_extent_item *fi;
4640
4641                         fi = btrfs_item_ptr(leaf, slot,
4642                                             struct btrfs_file_extent_item);
4643                         fi = (struct btrfs_file_extent_item *)(
4644                              (unsigned long)fi - size_diff);
4645
4646                         if (btrfs_file_extent_type(leaf, fi) ==
4647                             BTRFS_FILE_EXTENT_INLINE) {
4648                                 ptr = btrfs_item_ptr_offset(leaf, slot);
4649                                 memmove_extent_buffer(leaf, ptr,
4650                                       (unsigned long)fi,
4651                                       BTRFS_FILE_EXTENT_INLINE_DATA_START);
4652                         }
4653                 }
4654
4655                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4656                               data_end + size_diff, BTRFS_LEAF_DATA_OFFSET +
4657                               data_end, old_data_start - data_end);
4658
4659                 offset = btrfs_disk_key_offset(&disk_key);
4660                 btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
4661                 btrfs_set_item_key(leaf, &disk_key, slot);
4662                 if (slot == 0)
4663                         fixup_low_keys(fs_info, path, &disk_key, 1);
4664         }
4665
4666         item = btrfs_item_nr(slot);
4667         btrfs_set_item_size(leaf, item, new_size);
4668         btrfs_mark_buffer_dirty(leaf);
4669
4670         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4671                 btrfs_print_leaf(leaf);
4672                 BUG();
4673         }
4674 }
4675
4676 /*
4677  * make the item pointed to by the path bigger, data_size is the added size.
4678  */
4679 void btrfs_extend_item(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
4680                        u32 data_size)
4681 {
4682         int slot;
4683         struct extent_buffer *leaf;
4684         struct btrfs_item *item;
4685         u32 nritems;
4686         unsigned int data_end;
4687         unsigned int old_data;
4688         unsigned int old_size;
4689         int i;
4690         struct btrfs_map_token token;
4691
4692         btrfs_init_map_token(&token);
4693
4694         leaf = path->nodes[0];
4695
4696         nritems = btrfs_header_nritems(leaf);
4697         data_end = leaf_data_end(fs_info, leaf);
4698
4699         if (btrfs_leaf_free_space(fs_info, leaf) < data_size) {
4700                 btrfs_print_leaf(leaf);
4701                 BUG();
4702         }
4703         slot = path->slots[0];
4704         old_data = btrfs_item_end_nr(leaf, slot);
4705
4706         BUG_ON(slot < 0);
4707         if (slot >= nritems) {
4708                 btrfs_print_leaf(leaf);
4709                 btrfs_crit(fs_info, "slot %d too large, nritems %d",
4710                            slot, nritems);
4711                 BUG_ON(1);
4712         }
4713
4714         /*
4715          * item0..itemN ... dataN.offset..dataN.size .. data0.size
4716          */
4717         /* first correct the data pointers */
4718         for (i = slot; i < nritems; i++) {
4719                 u32 ioff;
4720                 item = btrfs_item_nr(i);
4721
4722                 ioff = btrfs_token_item_offset(leaf, item, &token);
4723                 btrfs_set_token_item_offset(leaf, item,
4724                                             ioff - data_size, &token);
4725         }
4726
4727         /* shift the data */
4728         memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4729                       data_end - data_size, BTRFS_LEAF_DATA_OFFSET +
4730                       data_end, old_data - data_end);
4731
4732         data_end = old_data;
4733         old_size = btrfs_item_size_nr(leaf, slot);
4734         item = btrfs_item_nr(slot);
4735         btrfs_set_item_size(leaf, item, old_size + data_size);
4736         btrfs_mark_buffer_dirty(leaf);
4737
4738         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4739                 btrfs_print_leaf(leaf);
4740                 BUG();
4741         }
4742 }
4743
4744 /*
4745  * this is a helper for btrfs_insert_empty_items, the main goal here is
4746  * to save stack depth by doing the bulk of the work in a function
4747  * that doesn't call btrfs_search_slot
4748  */
4749 void setup_items_for_insert(struct btrfs_root *root, struct btrfs_path *path,
4750                             const struct btrfs_key *cpu_key, u32 *data_size,
4751                             u32 total_data, u32 total_size, int nr)
4752 {
4753         struct btrfs_fs_info *fs_info = root->fs_info;
4754         struct btrfs_item *item;
4755         int i;
4756         u32 nritems;
4757         unsigned int data_end;
4758         struct btrfs_disk_key disk_key;
4759         struct extent_buffer *leaf;
4760         int slot;
4761         struct btrfs_map_token token;
4762
4763         if (path->slots[0] == 0) {
4764                 btrfs_cpu_key_to_disk(&disk_key, cpu_key);
4765                 fixup_low_keys(fs_info, path, &disk_key, 1);
4766         }
4767         btrfs_unlock_up_safe(path, 1);
4768
4769         btrfs_init_map_token(&token);
4770
4771         leaf = path->nodes[0];
4772         slot = path->slots[0];
4773
4774         nritems = btrfs_header_nritems(leaf);
4775         data_end = leaf_data_end(fs_info, leaf);
4776
4777         if (btrfs_leaf_free_space(fs_info, leaf) < total_size) {
4778                 btrfs_print_leaf(leaf);
4779                 btrfs_crit(fs_info, "not enough freespace need %u have %d",
4780                            total_size, btrfs_leaf_free_space(fs_info, leaf));
4781                 BUG();
4782         }
4783
4784         if (slot != nritems) {
4785                 unsigned int old_data = btrfs_item_end_nr(leaf, slot);
4786
4787                 if (old_data < data_end) {
4788                         btrfs_print_leaf(leaf);
4789                         btrfs_crit(fs_info, "slot %d old_data %d data_end %d",
4790                                    slot, old_data, data_end);
4791                         BUG_ON(1);
4792                 }
4793                 /*
4794                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
4795                  */
4796                 /* first correct the data pointers */
4797                 for (i = slot; i < nritems; i++) {
4798                         u32 ioff;
4799
4800                         item = btrfs_item_nr(i);
4801                         ioff = btrfs_token_item_offset(leaf, item, &token);
4802                         btrfs_set_token_item_offset(leaf, item,
4803                                                     ioff - total_data, &token);
4804                 }
4805                 /* shift the items */
4806                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + nr),
4807                               btrfs_item_nr_offset(slot),
4808                               (nritems - slot) * sizeof(struct btrfs_item));
4809
4810                 /* shift the data */
4811                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4812                               data_end - total_data, BTRFS_LEAF_DATA_OFFSET +
4813                               data_end, old_data - data_end);
4814                 data_end = old_data;
4815         }
4816
4817         /* setup the item for the new data */
4818         for (i = 0; i < nr; i++) {
4819                 btrfs_cpu_key_to_disk(&disk_key, cpu_key + i);
4820                 btrfs_set_item_key(leaf, &disk_key, slot + i);
4821                 item = btrfs_item_nr(slot + i);
4822                 btrfs_set_token_item_offset(leaf, item,
4823                                             data_end - data_size[i], &token);
4824                 data_end -= data_size[i];
4825                 btrfs_set_token_item_size(leaf, item, data_size[i], &token);
4826         }
4827
4828         btrfs_set_header_nritems(leaf, nritems + nr);
4829         btrfs_mark_buffer_dirty(leaf);
4830
4831         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4832                 btrfs_print_leaf(leaf);
4833                 BUG();
4834         }
4835 }
4836
4837 /*
4838  * Given a key and some data, insert items into the tree.
4839  * This does all the path init required, making room in the tree if needed.
4840  */
4841 int btrfs_insert_empty_items(struct btrfs_trans_handle *trans,
4842                             struct btrfs_root *root,
4843                             struct btrfs_path *path,
4844                             const struct btrfs_key *cpu_key, u32 *data_size,
4845                             int nr)
4846 {
4847         int ret = 0;
4848         int slot;
4849         int i;
4850         u32 total_size = 0;
4851         u32 total_data = 0;
4852
4853         for (i = 0; i < nr; i++)
4854                 total_data += data_size[i];
4855
4856         total_size = total_data + (nr * sizeof(struct btrfs_item));
4857         ret = btrfs_search_slot(trans, root, cpu_key, path, total_size, 1);
4858         if (ret == 0)
4859                 return -EEXIST;
4860         if (ret < 0)
4861                 return ret;
4862
4863         slot = path->slots[0];
4864         BUG_ON(slot < 0);
4865
4866         setup_items_for_insert(root, path, cpu_key, data_size,
4867                                total_data, total_size, nr);
4868         return 0;
4869 }
4870
4871 /*
4872  * Given a key and some data, insert an item into the tree.
4873  * This does all the path init required, making room in the tree if needed.
4874  */
4875 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4876                       const struct btrfs_key *cpu_key, void *data,
4877                       u32 data_size)
4878 {
4879         int ret = 0;
4880         struct btrfs_path *path;
4881         struct extent_buffer *leaf;
4882         unsigned long ptr;
4883
4884         path = btrfs_alloc_path();
4885         if (!path)
4886                 return -ENOMEM;
4887         ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
4888         if (!ret) {
4889                 leaf = path->nodes[0];
4890                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
4891                 write_extent_buffer(leaf, data, ptr, data_size);
4892                 btrfs_mark_buffer_dirty(leaf);
4893         }
4894         btrfs_free_path(path);
4895         return ret;
4896 }
4897
4898 /*
4899  * delete the pointer from a given node.
4900  *
4901  * the tree should have been previously balanced so the deletion does not
4902  * empty a node.
4903  */
4904 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
4905                     int level, int slot)
4906 {
4907         struct btrfs_fs_info *fs_info = root->fs_info;
4908         struct extent_buffer *parent = path->nodes[level];
4909         u32 nritems;
4910         int ret;
4911
4912         nritems = btrfs_header_nritems(parent);
4913         if (slot != nritems - 1) {
4914                 if (level)
4915                         tree_mod_log_eb_move(fs_info, parent, slot,
4916                                              slot + 1, nritems - slot - 1);
4917                 memmove_extent_buffer(parent,
4918                               btrfs_node_key_ptr_offset(slot),
4919                               btrfs_node_key_ptr_offset(slot + 1),
4920                               sizeof(struct btrfs_key_ptr) *
4921                               (nritems - slot - 1));
4922         } else if (level) {
4923                 ret = tree_mod_log_insert_key(fs_info, parent, slot,
4924                                               MOD_LOG_KEY_REMOVE, GFP_NOFS);
4925                 BUG_ON(ret < 0);
4926         }
4927
4928         nritems--;
4929         btrfs_set_header_nritems(parent, nritems);
4930         if (nritems == 0 && parent == root->node) {
4931                 BUG_ON(btrfs_header_level(root->node) != 1);
4932                 /* just turn the root into a leaf and break */
4933                 btrfs_set_header_level(root->node, 0);
4934         } else if (slot == 0) {
4935                 struct btrfs_disk_key disk_key;
4936
4937                 btrfs_node_key(parent, &disk_key, 0);
4938                 fixup_low_keys(fs_info, path, &disk_key, level + 1);
4939         }
4940         btrfs_mark_buffer_dirty(parent);
4941 }
4942
4943 /*
4944  * a helper function to delete the leaf pointed to by path->slots[1] and
4945  * path->nodes[1].
4946  *
4947  * This deletes the pointer in path->nodes[1] and frees the leaf
4948  * block extent.  zero is returned if it all worked out, < 0 otherwise.
4949  *
4950  * The path must have already been setup for deleting the leaf, including
4951  * all the proper balancing.  path->nodes[1] must be locked.
4952  */
4953 static noinline void btrfs_del_leaf(struct btrfs_trans_handle *trans,
4954                                     struct btrfs_root *root,
4955                                     struct btrfs_path *path,
4956                                     struct extent_buffer *leaf)
4957 {
4958         WARN_ON(btrfs_header_generation(leaf) != trans->transid);
4959         del_ptr(root, path, 1, path->slots[1]);
4960
4961         /*
4962          * btrfs_free_extent is expensive, we want to make sure we
4963          * aren't holding any locks when we call it
4964          */
4965         btrfs_unlock_up_safe(path, 0);
4966
4967         root_sub_used(root, leaf->len);
4968
4969         extent_buffer_get(leaf);
4970         btrfs_free_tree_block(trans, root, leaf, 0, 1);
4971         free_extent_buffer_stale(leaf);
4972 }
4973 /*
4974  * delete the item at the leaf level in path.  If that empties
4975  * the leaf, remove it from the tree
4976  */
4977 int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4978                     struct btrfs_path *path, int slot, int nr)
4979 {
4980         struct btrfs_fs_info *fs_info = root->fs_info;
4981         struct extent_buffer *leaf;
4982         struct btrfs_item *item;
4983         u32 last_off;
4984         u32 dsize = 0;
4985         int ret = 0;
4986         int wret;
4987         int i;
4988         u32 nritems;
4989         struct btrfs_map_token token;
4990
4991         btrfs_init_map_token(&token);
4992
4993         leaf = path->nodes[0];
4994         last_off = btrfs_item_offset_nr(leaf, slot + nr - 1);
4995
4996         for (i = 0; i < nr; i++)
4997                 dsize += btrfs_item_size_nr(leaf, slot + i);
4998
4999         nritems = btrfs_header_nritems(leaf);
5000
5001         if (slot + nr != nritems) {
5002                 int data_end = leaf_data_end(fs_info, leaf);
5003
5004                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
5005                               data_end + dsize,
5006                               BTRFS_LEAF_DATA_OFFSET + data_end,
5007                               last_off - data_end);
5008
5009                 for (i = slot + nr; i < nritems; i++) {
5010                         u32 ioff;
5011
5012                         item = btrfs_item_nr(i);
5013                         ioff = btrfs_token_item_offset(leaf, item, &token);
5014                         btrfs_set_token_item_offset(leaf, item,
5015                                                     ioff + dsize, &token);
5016                 }
5017
5018                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot),
5019                               btrfs_item_nr_offset(slot + nr),
5020                               sizeof(struct btrfs_item) *
5021                               (nritems - slot - nr));
5022         }
5023         btrfs_set_header_nritems(leaf, nritems - nr);
5024         nritems -= nr;
5025
5026         /* delete the leaf if we've emptied it */
5027         if (nritems == 0) {
5028                 if (leaf == root->node) {
5029                         btrfs_set_header_level(leaf, 0);
5030                 } else {
5031                         btrfs_set_path_blocking(path);
5032                         clean_tree_block(fs_info, leaf);
5033                         btrfs_del_leaf(trans, root, path, leaf);
5034                 }
5035         } else {
5036                 int used = leaf_space_used(leaf, 0, nritems);
5037                 if (slot == 0) {
5038                         struct btrfs_disk_key disk_key;
5039
5040                         btrfs_item_key(leaf, &disk_key, 0);
5041                         fixup_low_keys(fs_info, path, &disk_key, 1);
5042                 }
5043
5044                 /* delete the leaf if it is mostly empty */
5045                 if (used < BTRFS_LEAF_DATA_SIZE(fs_info) / 3) {
5046                         /* push_leaf_left fixes the path.
5047                          * make sure the path still points to our leaf
5048                          * for possible call to del_ptr below
5049                          */
5050                         slot = path->slots[1];
5051                         extent_buffer_get(leaf);
5052
5053                         btrfs_set_path_blocking(path);
5054                         wret = push_leaf_left(trans, root, path, 1, 1,
5055                                               1, (u32)-1);
5056                         if (wret < 0 && wret != -ENOSPC)
5057                                 ret = wret;
5058
5059                         if (path->nodes[0] == leaf &&
5060                             btrfs_header_nritems(leaf)) {
5061                                 wret = push_leaf_right(trans, root, path, 1,
5062                                                        1, 1, 0);
5063                                 if (wret < 0 && wret != -ENOSPC)
5064                                         ret = wret;
5065                         }
5066
5067                         if (btrfs_header_nritems(leaf) == 0) {
5068                                 path->slots[1] = slot;
5069                                 btrfs_del_leaf(trans, root, path, leaf);
5070                                 free_extent_buffer(leaf);
5071                                 ret = 0;
5072                         } else {
5073                                 /* if we're still in the path, make sure
5074                                  * we're dirty.  Otherwise, one of the
5075                                  * push_leaf functions must have already
5076                                  * dirtied this buffer
5077                                  */
5078                                 if (path->nodes[0] == leaf)
5079                                         btrfs_mark_buffer_dirty(leaf);
5080                                 free_extent_buffer(leaf);
5081                         }
5082                 } else {
5083                         btrfs_mark_buffer_dirty(leaf);
5084                 }
5085         }
5086         return ret;
5087 }
5088
5089 /*
5090  * search the tree again to find a leaf with lesser keys
5091  * returns 0 if it found something or 1 if there are no lesser leaves.
5092  * returns < 0 on io errors.
5093  *
5094  * This may release the path, and so you may lose any locks held at the
5095  * time you call it.
5096  */
5097 int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
5098 {
5099         struct btrfs_key key;
5100         struct btrfs_disk_key found_key;
5101         int ret;
5102
5103         btrfs_item_key_to_cpu(path->nodes[0], &key, 0);
5104
5105         if (key.offset > 0) {
5106                 key.offset--;
5107         } else if (key.type > 0) {
5108                 key.type--;
5109                 key.offset = (u64)-1;
5110         } else if (key.objectid > 0) {
5111                 key.objectid--;
5112                 key.type = (u8)-1;
5113                 key.offset = (u64)-1;
5114         } else {
5115                 return 1;
5116         }
5117
5118         btrfs_release_path(path);
5119         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5120         if (ret < 0)
5121                 return ret;
5122         btrfs_item_key(path->nodes[0], &found_key, 0);
5123         ret = comp_keys(&found_key, &key);
5124         /*
5125          * We might have had an item with the previous key in the tree right
5126          * before we released our path. And after we released our path, that
5127          * item might have been pushed to the first slot (0) of the leaf we
5128          * were holding due to a tree balance. Alternatively, an item with the
5129          * previous key can exist as the only element of a leaf (big fat item).
5130          * Therefore account for these 2 cases, so that our callers (like
5131          * btrfs_previous_item) don't miss an existing item with a key matching
5132          * the previous key we computed above.
5133          */
5134         if (ret <= 0)
5135                 return 0;
5136         return 1;
5137 }
5138
5139 /*
5140  * A helper function to walk down the tree starting at min_key, and looking
5141  * for nodes or leaves that are have a minimum transaction id.
5142  * This is used by the btree defrag code, and tree logging
5143  *
5144  * This does not cow, but it does stuff the starting key it finds back
5145  * into min_key, so you can call btrfs_search_slot with cow=1 on the
5146  * key and get a writable path.
5147  *
5148  * This does lock as it descends, and path->keep_locks should be set
5149  * to 1 by the caller.
5150  *
5151  * This honors path->lowest_level to prevent descent past a given level
5152  * of the tree.
5153  *
5154  * min_trans indicates the oldest transaction that you are interested
5155  * in walking through.  Any nodes or leaves older than min_trans are
5156  * skipped over (without reading them).
5157  *
5158  * returns zero if something useful was found, < 0 on error and 1 if there
5159  * was nothing in the tree that matched the search criteria.
5160  */
5161 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
5162                          struct btrfs_path *path,
5163                          u64 min_trans)
5164 {
5165         struct btrfs_fs_info *fs_info = root->fs_info;
5166         struct extent_buffer *cur;
5167         struct btrfs_key found_key;
5168         int slot;
5169         int sret;
5170         u32 nritems;
5171         int level;
5172         int ret = 1;
5173         int keep_locks = path->keep_locks;
5174
5175         path->keep_locks = 1;
5176 again:
5177         cur = btrfs_read_lock_root_node(root);
5178         level = btrfs_header_level(cur);
5179         WARN_ON(path->nodes[level]);
5180         path->nodes[level] = cur;
5181         path->locks[level] = BTRFS_READ_LOCK;
5182
5183         if (btrfs_header_generation(cur) < min_trans) {
5184                 ret = 1;
5185                 goto out;
5186         }
5187         while (1) {
5188                 nritems = btrfs_header_nritems(cur);
5189                 level = btrfs_header_level(cur);
5190                 sret = btrfs_bin_search(cur, min_key, level, &slot);
5191
5192                 /* at the lowest level, we're done, setup the path and exit */
5193                 if (level == path->lowest_level) {
5194                         if (slot >= nritems)
5195                                 goto find_next_key;
5196                         ret = 0;
5197                         path->slots[level] = slot;
5198                         btrfs_item_key_to_cpu(cur, &found_key, slot);
5199                         goto out;
5200                 }
5201                 if (sret && slot > 0)
5202                         slot--;
5203                 /*
5204                  * check this node pointer against the min_trans parameters.
5205                  * If it is too old, old, skip to the next one.
5206                  */
5207                 while (slot < nritems) {
5208                         u64 gen;
5209
5210                         gen = btrfs_node_ptr_generation(cur, slot);
5211                         if (gen < min_trans) {
5212                                 slot++;
5213                                 continue;
5214                         }
5215                         break;
5216                 }
5217 find_next_key:
5218                 /*
5219                  * we didn't find a candidate key in this node, walk forward
5220                  * and find another one
5221                  */
5222                 if (slot >= nritems) {
5223                         path->slots[level] = slot;
5224                         btrfs_set_path_blocking(path);
5225                         sret = btrfs_find_next_key(root, path, min_key, level,
5226                                                   min_trans);
5227                         if (sret == 0) {
5228                                 btrfs_release_path(path);
5229                                 goto again;
5230                         } else {
5231                                 goto out;
5232                         }
5233                 }
5234                 /* save our key for returning back */
5235                 btrfs_node_key_to_cpu(cur, &found_key, slot);
5236                 path->slots[level] = slot;
5237                 if (level == path->lowest_level) {
5238                         ret = 0;
5239                         goto out;
5240                 }
5241                 btrfs_set_path_blocking(path);
5242                 cur = read_node_slot(fs_info, cur, slot);
5243                 if (IS_ERR(cur)) {
5244                         ret = PTR_ERR(cur);
5245                         goto out;
5246                 }
5247
5248                 btrfs_tree_read_lock(cur);
5249
5250                 path->locks[level - 1] = BTRFS_READ_LOCK;
5251                 path->nodes[level - 1] = cur;
5252                 unlock_up(path, level, 1, 0, NULL);
5253                 btrfs_clear_path_blocking(path, NULL, 0);
5254         }
5255 out:
5256         path->keep_locks = keep_locks;
5257         if (ret == 0) {
5258                 btrfs_unlock_up_safe(path, path->lowest_level + 1);
5259                 btrfs_set_path_blocking(path);
5260                 memcpy(min_key, &found_key, sizeof(found_key));
5261         }
5262         return ret;
5263 }
5264
5265 static int tree_move_down(struct btrfs_fs_info *fs_info,
5266                            struct btrfs_path *path,
5267                            int *level)
5268 {
5269         struct extent_buffer *eb;
5270
5271         BUG_ON(*level == 0);
5272         eb = read_node_slot(fs_info, path->nodes[*level], path->slots[*level]);
5273         if (IS_ERR(eb))
5274                 return PTR_ERR(eb);
5275
5276         path->nodes[*level - 1] = eb;
5277         path->slots[*level - 1] = 0;
5278         (*level)--;
5279         return 0;
5280 }
5281
5282 static int tree_move_next_or_upnext(struct btrfs_path *path,
5283                                     int *level, int root_level)
5284 {
5285         int ret = 0;
5286         int nritems;
5287         nritems = btrfs_header_nritems(path->nodes[*level]);
5288
5289         path->slots[*level]++;
5290
5291         while (path->slots[*level] >= nritems) {
5292                 if (*level == root_level)
5293                         return -1;
5294
5295                 /* move upnext */
5296                 path->slots[*level] = 0;
5297                 free_extent_buffer(path->nodes[*level]);
5298                 path->nodes[*level] = NULL;
5299                 (*level)++;
5300                 path->slots[*level]++;
5301
5302                 nritems = btrfs_header_nritems(path->nodes[*level]);
5303                 ret = 1;
5304         }
5305         return ret;
5306 }
5307
5308 /*
5309  * Returns 1 if it had to move up and next. 0 is returned if it moved only next
5310  * or down.
5311  */
5312 static int tree_advance(struct btrfs_fs_info *fs_info,
5313                         struct btrfs_path *path,
5314                         int *level, int root_level,
5315                         int allow_down,
5316                         struct btrfs_key *key)
5317 {
5318         int ret;
5319
5320         if (*level == 0 || !allow_down) {
5321                 ret = tree_move_next_or_upnext(path, level, root_level);
5322         } else {
5323                 ret = tree_move_down(fs_info, path, level);
5324         }
5325         if (ret >= 0) {
5326                 if (*level == 0)
5327                         btrfs_item_key_to_cpu(path->nodes[*level], key,
5328                                         path->slots[*level]);
5329                 else
5330                         btrfs_node_key_to_cpu(path->nodes[*level], key,
5331                                         path->slots[*level]);
5332         }
5333         return ret;
5334 }
5335
5336 static int tree_compare_item(struct btrfs_path *left_path,
5337                              struct btrfs_path *right_path,
5338                              char *tmp_buf)
5339 {
5340         int cmp;
5341         int len1, len2;
5342         unsigned long off1, off2;
5343
5344         len1 = btrfs_item_size_nr(left_path->nodes[0], left_path->slots[0]);
5345         len2 = btrfs_item_size_nr(right_path->nodes[0], right_path->slots[0]);
5346         if (len1 != len2)
5347                 return 1;
5348
5349         off1 = btrfs_item_ptr_offset(left_path->nodes[0], left_path->slots[0]);
5350         off2 = btrfs_item_ptr_offset(right_path->nodes[0],
5351                                 right_path->slots[0]);
5352
5353         read_extent_buffer(left_path->nodes[0], tmp_buf, off1, len1);
5354
5355         cmp = memcmp_extent_buffer(right_path->nodes[0], tmp_buf, off2, len1);
5356         if (cmp)
5357                 return 1;
5358         return 0;
5359 }
5360
5361 #define ADVANCE 1
5362 #define ADVANCE_ONLY_NEXT -1
5363
5364 /*
5365  * This function compares two trees and calls the provided callback for
5366  * every changed/new/deleted item it finds.
5367  * If shared tree blocks are encountered, whole subtrees are skipped, making
5368  * the compare pretty fast on snapshotted subvolumes.
5369  *
5370  * This currently works on commit roots only. As commit roots are read only,
5371  * we don't do any locking. The commit roots are protected with transactions.
5372  * Transactions are ended and rejoined when a commit is tried in between.
5373  *
5374  * This function checks for modifications done to the trees while comparing.
5375  * If it detects a change, it aborts immediately.
5376  */
5377 int btrfs_compare_trees(struct btrfs_root *left_root,
5378                         struct btrfs_root *right_root,
5379                         btrfs_changed_cb_t changed_cb, void *ctx)
5380 {
5381         struct btrfs_fs_info *fs_info = left_root->fs_info;
5382         int ret;
5383         int cmp;
5384         struct btrfs_path *left_path = NULL;
5385         struct btrfs_path *right_path = NULL;
5386         struct btrfs_key left_key;
5387         struct btrfs_key right_key;
5388         char *tmp_buf = NULL;
5389         int left_root_level;
5390         int right_root_level;
5391         int left_level;
5392         int right_level;
5393         int left_end_reached;
5394         int right_end_reached;
5395         int advance_left;
5396         int advance_right;
5397         u64 left_blockptr;
5398         u64 right_blockptr;
5399         u64 left_gen;
5400         u64 right_gen;
5401
5402         left_path = btrfs_alloc_path();
5403         if (!left_path) {
5404                 ret = -ENOMEM;
5405                 goto out;
5406         }
5407         right_path = btrfs_alloc_path();
5408         if (!right_path) {
5409                 ret = -ENOMEM;
5410                 goto out;
5411         }
5412
5413         tmp_buf = kvmalloc(fs_info->nodesize, GFP_KERNEL);
5414         if (!tmp_buf) {
5415                 ret = -ENOMEM;
5416                 goto out;
5417         }
5418
5419         left_path->search_commit_root = 1;
5420         left_path->skip_locking = 1;
5421         right_path->search_commit_root = 1;
5422         right_path->skip_locking = 1;
5423
5424         /*
5425          * Strategy: Go to the first items of both trees. Then do
5426          *
5427          * If both trees are at level 0
5428          *   Compare keys of current items
5429          *     If left < right treat left item as new, advance left tree
5430          *       and repeat
5431          *     If left > right treat right item as deleted, advance right tree
5432          *       and repeat
5433          *     If left == right do deep compare of items, treat as changed if
5434          *       needed, advance both trees and repeat
5435          * If both trees are at the same level but not at level 0
5436          *   Compare keys of current nodes/leafs
5437          *     If left < right advance left tree and repeat
5438          *     If left > right advance right tree and repeat
5439          *     If left == right compare blockptrs of the next nodes/leafs
5440          *       If they match advance both trees but stay at the same level
5441          *         and repeat
5442          *       If they don't match advance both trees while allowing to go
5443          *         deeper and repeat
5444          * If tree levels are different
5445          *   Advance the tree that needs it and repeat
5446          *
5447          * Advancing a tree means:
5448          *   If we are at level 0, try to go to the next slot. If that's not
5449          *   possible, go one level up and repeat. Stop when we found a level
5450          *   where we could go to the next slot. We may at this point be on a
5451          *   node or a leaf.
5452          *
5453          *   If we are not at level 0 and not on shared tree blocks, go one
5454          *   level deeper.
5455          *
5456          *   If we are not at level 0 and on shared tree blocks, go one slot to
5457          *   the right if possible or go up and right.
5458          */
5459
5460         down_read(&fs_info->commit_root_sem);
5461         left_level = btrfs_header_level(left_root->commit_root);
5462         left_root_level = left_level;
5463         left_path->nodes[left_level] = left_root->commit_root;
5464         extent_buffer_get(left_path->nodes[left_level]);
5465
5466         right_level = btrfs_header_level(right_root->commit_root);
5467         right_root_level = right_level;
5468         right_path->nodes[right_level] = right_root->commit_root;
5469         extent_buffer_get(right_path->nodes[right_level]);
5470         up_read(&fs_info->commit_root_sem);
5471
5472         if (left_level == 0)
5473                 btrfs_item_key_to_cpu(left_path->nodes[left_level],
5474                                 &left_key, left_path->slots[left_level]);
5475         else
5476                 btrfs_node_key_to_cpu(left_path->nodes[left_level],
5477                                 &left_key, left_path->slots[left_level]);
5478         if (right_level == 0)
5479                 btrfs_item_key_to_cpu(right_path->nodes[right_level],
5480                                 &right_key, right_path->slots[right_level]);
5481         else
5482                 btrfs_node_key_to_cpu(right_path->nodes[right_level],
5483                                 &right_key, right_path->slots[right_level]);
5484
5485         left_end_reached = right_end_reached = 0;
5486         advance_left = advance_right = 0;
5487
5488         while (1) {
5489                 if (advance_left && !left_end_reached) {
5490                         ret = tree_advance(fs_info, left_path, &left_level,
5491                                         left_root_level,
5492                                         advance_left != ADVANCE_ONLY_NEXT,
5493                                         &left_key);
5494                         if (ret == -1)
5495                                 left_end_reached = ADVANCE;
5496                         else if (ret < 0)
5497                                 goto out;
5498                         advance_left = 0;
5499                 }
5500                 if (advance_right && !right_end_reached) {
5501                         ret = tree_advance(fs_info, right_path, &right_level,
5502                                         right_root_level,
5503                                         advance_right != ADVANCE_ONLY_NEXT,
5504                                         &right_key);
5505                         if (ret == -1)
5506                                 right_end_reached = ADVANCE;
5507                         else if (ret < 0)
5508                                 goto out;
5509                         advance_right = 0;
5510                 }
5511
5512                 if (left_end_reached && right_end_reached) {
5513                         ret = 0;
5514                         goto out;
5515                 } else if (left_end_reached) {
5516                         if (right_level == 0) {
5517                                 ret = changed_cb(left_path, right_path,
5518                                                 &right_key,
5519                                                 BTRFS_COMPARE_TREE_DELETED,
5520                                                 ctx);
5521                                 if (ret < 0)
5522                                         goto out;
5523                         }
5524                         advance_right = ADVANCE;
5525                         continue;
5526                 } else if (right_end_reached) {
5527                         if (left_level == 0) {
5528                                 ret = changed_cb(left_path, right_path,
5529                                                 &left_key,
5530                                                 BTRFS_COMPARE_TREE_NEW,
5531                                                 ctx);
5532                                 if (ret < 0)
5533                                         goto out;
5534                         }
5535                         advance_left = ADVANCE;
5536                         continue;
5537                 }
5538
5539                 if (left_level == 0 && right_level == 0) {
5540                         cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5541                         if (cmp < 0) {
5542                                 ret = changed_cb(left_path, right_path,
5543                                                 &left_key,
5544                                                 BTRFS_COMPARE_TREE_NEW,
5545                                                 ctx);
5546                                 if (ret < 0)
5547                                         goto out;
5548                                 advance_left = ADVANCE;
5549                         } else if (cmp > 0) {
5550                                 ret = changed_cb(left_path, right_path,
5551                                                 &right_key,
5552                                                 BTRFS_COMPARE_TREE_DELETED,
5553                                                 ctx);
5554                                 if (ret < 0)
5555                                         goto out;
5556                                 advance_right = ADVANCE;
5557                         } else {
5558                                 enum btrfs_compare_tree_result result;
5559
5560                                 WARN_ON(!extent_buffer_uptodate(left_path->nodes[0]));
5561                                 ret = tree_compare_item(left_path, right_path,
5562                                                         tmp_buf);
5563                                 if (ret)
5564                                         result = BTRFS_COMPARE_TREE_CHANGED;
5565                                 else
5566                                         result = BTRFS_COMPARE_TREE_SAME;
5567                                 ret = changed_cb(left_path, right_path,
5568                                                  &left_key, result, ctx);
5569                                 if (ret < 0)
5570                                         goto out;
5571                                 advance_left = ADVANCE;
5572                                 advance_right = ADVANCE;
5573                         }
5574                 } else if (left_level == right_level) {
5575                         cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5576                         if (cmp < 0) {
5577                                 advance_left = ADVANCE;
5578                         } else if (cmp > 0) {
5579                                 advance_right = ADVANCE;
5580                         } else {
5581                                 left_blockptr = btrfs_node_blockptr(
5582                                                 left_path->nodes[left_level],
5583                                                 left_path->slots[left_level]);
5584                                 right_blockptr = btrfs_node_blockptr(
5585                                                 right_path->nodes[right_level],
5586                                                 right_path->slots[right_level]);
5587                                 left_gen = btrfs_node_ptr_generation(
5588                                                 left_path->nodes[left_level],
5589                                                 left_path->slots[left_level]);
5590                                 right_gen = btrfs_node_ptr_generation(
5591                                                 right_path->nodes[right_level],
5592                                                 right_path->slots[right_level]);
5593                                 if (left_blockptr == right_blockptr &&
5594                                     left_gen == right_gen) {
5595                                         /*
5596                                          * As we're on a shared block, don't
5597                                          * allow to go deeper.
5598                                          */
5599                                         advance_left = ADVANCE_ONLY_NEXT;
5600                                         advance_right = ADVANCE_ONLY_NEXT;
5601                                 } else {
5602                                         advance_left = ADVANCE;
5603                                         advance_right = ADVANCE;
5604                                 }
5605                         }
5606                 } else if (left_level < right_level) {
5607                         advance_right = ADVANCE;
5608                 } else {
5609                         advance_left = ADVANCE;
5610                 }
5611         }
5612
5613 out:
5614         btrfs_free_path(left_path);
5615         btrfs_free_path(right_path);
5616         kvfree(tmp_buf);
5617         return ret;
5618 }
5619
5620 /*
5621  * this is similar to btrfs_next_leaf, but does not try to preserve
5622  * and fixup the path.  It looks for and returns the next key in the
5623  * tree based on the current path and the min_trans parameters.
5624  *
5625  * 0 is returned if another key is found, < 0 if there are any errors
5626  * and 1 is returned if there are no higher keys in the tree
5627  *
5628  * path->keep_locks should be set to 1 on the search made before
5629  * calling this function.
5630  */
5631 int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
5632                         struct btrfs_key *key, int level, u64 min_trans)
5633 {
5634         int slot;
5635         struct extent_buffer *c;
5636
5637         WARN_ON(!path->keep_locks);
5638         while (level < BTRFS_MAX_LEVEL) {
5639                 if (!path->nodes[level])
5640                         return 1;
5641
5642                 slot = path->slots[level] + 1;
5643                 c = path->nodes[level];
5644 next:
5645                 if (slot >= btrfs_header_nritems(c)) {
5646                         int ret;
5647                         int orig_lowest;
5648                         struct btrfs_key cur_key;
5649                         if (level + 1 >= BTRFS_MAX_LEVEL ||
5650                             !path->nodes[level + 1])
5651                                 return 1;
5652
5653                         if (path->locks[level + 1]) {
5654                                 level++;
5655                                 continue;
5656                         }
5657
5658                         slot = btrfs_header_nritems(c) - 1;
5659                         if (level == 0)
5660                                 btrfs_item_key_to_cpu(c, &cur_key, slot);
5661                         else
5662                                 btrfs_node_key_to_cpu(c, &cur_key, slot);
5663
5664                         orig_lowest = path->lowest_level;
5665                         btrfs_release_path(path);
5666                         path->lowest_level = level;
5667                         ret = btrfs_search_slot(NULL, root, &cur_key, path,
5668                                                 0, 0);
5669                         path->lowest_level = orig_lowest;
5670                         if (ret < 0)
5671                                 return ret;
5672
5673                         c = path->nodes[level];
5674                         slot = path->slots[level];
5675                         if (ret == 0)
5676                                 slot++;
5677                         goto next;
5678                 }
5679
5680                 if (level == 0)
5681                         btrfs_item_key_to_cpu(c, key, slot);
5682                 else {
5683                         u64 gen = btrfs_node_ptr_generation(c, slot);
5684
5685                         if (gen < min_trans) {
5686                                 slot++;
5687                                 goto next;
5688                         }
5689                         btrfs_node_key_to_cpu(c, key, slot);
5690                 }
5691                 return 0;
5692         }
5693         return 1;
5694 }
5695
5696 /*
5697  * search the tree again to find a leaf with greater keys
5698  * returns 0 if it found something or 1 if there are no greater leaves.
5699  * returns < 0 on io errors.
5700  */
5701 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
5702 {
5703         return btrfs_next_old_leaf(root, path, 0);
5704 }
5705
5706 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
5707                         u64 time_seq)
5708 {
5709         int slot;
5710         int level;
5711         struct extent_buffer *c;
5712         struct extent_buffer *next;
5713         struct btrfs_key key;
5714         u32 nritems;
5715         int ret;
5716         int old_spinning = path->leave_spinning;
5717         int next_rw_lock = 0;
5718
5719         nritems = btrfs_header_nritems(path->nodes[0]);
5720         if (nritems == 0)
5721                 return 1;
5722
5723         btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
5724 again:
5725         level = 1;
5726         next = NULL;
5727         next_rw_lock = 0;
5728         btrfs_release_path(path);
5729
5730         path->keep_locks = 1;
5731         path->leave_spinning = 1;
5732
5733         if (time_seq)
5734                 ret = btrfs_search_old_slot(root, &key, path, time_seq);
5735         else
5736                 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5737         path->keep_locks = 0;
5738
5739         if (ret < 0)
5740                 return ret;
5741
5742         nritems = btrfs_header_nritems(path->nodes[0]);
5743         /*
5744          * by releasing the path above we dropped all our locks.  A balance
5745          * could have added more items next to the key that used to be
5746          * at the very end of the block.  So, check again here and
5747          * advance the path if there are now more items available.
5748          */
5749         if (nritems > 0 && path->slots[0] < nritems - 1) {
5750                 if (ret == 0)
5751                         path->slots[0]++;
5752                 ret = 0;
5753                 goto done;
5754         }
5755         /*
5756          * So the above check misses one case:
5757          * - after releasing the path above, someone has removed the item that
5758          *   used to be at the very end of the block, and balance between leafs
5759          *   gets another one with bigger key.offset to replace it.
5760          *
5761          * This one should be returned as well, or we can get leaf corruption
5762          * later(esp. in __btrfs_drop_extents()).
5763          *
5764          * And a bit more explanation about this check,
5765          * with ret > 0, the key isn't found, the path points to the slot
5766          * where it should be inserted, so the path->slots[0] item must be the
5767          * bigger one.
5768          */
5769         if (nritems > 0 && ret > 0 && path->slots[0] == nritems - 1) {
5770                 ret = 0;
5771                 goto done;
5772         }
5773
5774         while (level < BTRFS_MAX_LEVEL) {
5775                 if (!path->nodes[level]) {
5776                         ret = 1;
5777                         goto done;
5778                 }
5779
5780                 slot = path->slots[level] + 1;
5781                 c = path->nodes[level];
5782                 if (slot >= btrfs_header_nritems(c)) {
5783                         level++;
5784                         if (level == BTRFS_MAX_LEVEL) {
5785                                 ret = 1;
5786                                 goto done;
5787                         }
5788                         continue;
5789                 }
5790
5791                 if (next) {
5792                         btrfs_tree_unlock_rw(next, next_rw_lock);
5793                         free_extent_buffer(next);
5794                 }
5795
5796                 next = c;
5797                 next_rw_lock = path->locks[level];
5798                 ret = read_block_for_search(root, path, &next, level,
5799                                             slot, &key);
5800                 if (ret == -EAGAIN)
5801                         goto again;
5802
5803                 if (ret < 0) {
5804                         btrfs_release_path(path);
5805                         goto done;
5806                 }
5807
5808                 if (!path->skip_locking) {
5809                         ret = btrfs_try_tree_read_lock(next);
5810                         if (!ret && time_seq) {
5811                                 /*
5812                                  * If we don't get the lock, we may be racing
5813                                  * with push_leaf_left, holding that lock while
5814                                  * itself waiting for the leaf we've currently
5815                                  * locked. To solve this situation, we give up
5816                                  * on our lock and cycle.
5817                                  */
5818                                 free_extent_buffer(next);
5819                                 btrfs_release_path(path);
5820                                 cond_resched();
5821                                 goto again;
5822                         }
5823                         if (!ret) {
5824                                 btrfs_set_path_blocking(path);
5825                                 btrfs_tree_read_lock(next);
5826                                 btrfs_clear_path_blocking(path, next,
5827                                                           BTRFS_READ_LOCK);
5828                         }
5829                         next_rw_lock = BTRFS_READ_LOCK;
5830                 }
5831                 break;
5832         }
5833         path->slots[level] = slot;
5834         while (1) {
5835                 level--;
5836                 c = path->nodes[level];
5837                 if (path->locks[level])
5838                         btrfs_tree_unlock_rw(c, path->locks[level]);
5839
5840                 free_extent_buffer(c);
5841                 path->nodes[level] = next;
5842                 path->slots[level] = 0;
5843                 if (!path->skip_locking)
5844                         path->locks[level] = next_rw_lock;
5845                 if (!level)
5846                         break;
5847
5848                 ret = read_block_for_search(root, path, &next, level,
5849                                             0, &key);
5850                 if (ret == -EAGAIN)
5851                         goto again;
5852
5853                 if (ret < 0) {
5854                         btrfs_release_path(path);
5855                         goto done;
5856                 }
5857
5858                 if (!path->skip_locking) {
5859                         ret = btrfs_try_tree_read_lock(next);
5860                         if (!ret) {
5861                                 btrfs_set_path_blocking(path);
5862                                 btrfs_tree_read_lock(next);
5863                                 btrfs_clear_path_blocking(path, next,
5864                                                           BTRFS_READ_LOCK);
5865                         }
5866                         next_rw_lock = BTRFS_READ_LOCK;
5867                 }
5868         }
5869         ret = 0;
5870 done:
5871         unlock_up(path, 0, 1, 0, NULL);
5872         path->leave_spinning = old_spinning;
5873         if (!old_spinning)
5874                 btrfs_set_path_blocking(path);
5875
5876         return ret;
5877 }
5878
5879 /*
5880  * this uses btrfs_prev_leaf to walk backwards in the tree, and keeps
5881  * searching until it gets past min_objectid or finds an item of 'type'
5882  *
5883  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5884  */
5885 int btrfs_previous_item(struct btrfs_root *root,
5886                         struct btrfs_path *path, u64 min_objectid,
5887                         int type)
5888 {
5889         struct btrfs_key found_key;
5890         struct extent_buffer *leaf;
5891         u32 nritems;
5892         int ret;
5893
5894         while (1) {
5895                 if (path->slots[0] == 0) {
5896                         btrfs_set_path_blocking(path);
5897                         ret = btrfs_prev_leaf(root, path);
5898                         if (ret != 0)
5899                                 return ret;
5900                 } else {
5901                         path->slots[0]--;
5902                 }
5903                 leaf = path->nodes[0];
5904                 nritems = btrfs_header_nritems(leaf);
5905                 if (nritems == 0)
5906                         return 1;
5907                 if (path->slots[0] == nritems)
5908                         path->slots[0]--;
5909
5910                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5911                 if (found_key.objectid < min_objectid)
5912                         break;
5913                 if (found_key.type == type)
5914                         return 0;
5915                 if (found_key.objectid == min_objectid &&
5916                     found_key.type < type)
5917                         break;
5918         }
5919         return 1;
5920 }
5921
5922 /*
5923  * search in extent tree to find a previous Metadata/Data extent item with
5924  * min objecitd.
5925  *
5926  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5927  */
5928 int btrfs_previous_extent_item(struct btrfs_root *root,
5929                         struct btrfs_path *path, u64 min_objectid)
5930 {
5931         struct btrfs_key found_key;
5932         struct extent_buffer *leaf;
5933         u32 nritems;
5934         int ret;
5935
5936         while (1) {
5937                 if (path->slots[0] == 0) {
5938                         btrfs_set_path_blocking(path);
5939                         ret = btrfs_prev_leaf(root, path);
5940                         if (ret != 0)
5941                                 return ret;
5942                 } else {
5943                         path->slots[0]--;
5944                 }
5945                 leaf = path->nodes[0];
5946                 nritems = btrfs_header_nritems(leaf);
5947                 if (nritems == 0)
5948                         return 1;
5949                 if (path->slots[0] == nritems)
5950                         path->slots[0]--;
5951
5952                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5953                 if (found_key.objectid < min_objectid)
5954                         break;
5955                 if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
5956                     found_key.type == BTRFS_METADATA_ITEM_KEY)
5957                         return 0;
5958                 if (found_key.objectid == min_objectid &&
5959                     found_key.type < BTRFS_EXTENT_ITEM_KEY)
5960                         break;
5961         }
5962         return 1;
5963 }