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                         BUG_ON(ret); /* -ENOMEM */
1036
1037                         if (root->root_key.objectid ==
1038                             BTRFS_TREE_RELOC_OBJECTID) {
1039                                 ret = btrfs_dec_ref(trans, root, buf, 0);
1040                                 BUG_ON(ret); /* -ENOMEM */
1041                                 ret = btrfs_inc_ref(trans, root, cow, 1);
1042                                 BUG_ON(ret); /* -ENOMEM */
1043                         }
1044                         new_flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
1045                 } else {
1046
1047                         if (root->root_key.objectid ==
1048                             BTRFS_TREE_RELOC_OBJECTID)
1049                                 ret = btrfs_inc_ref(trans, root, cow, 1);
1050                         else
1051                                 ret = btrfs_inc_ref(trans, root, cow, 0);
1052                         BUG_ON(ret); /* -ENOMEM */
1053                 }
1054                 if (new_flags != 0) {
1055                         int level = btrfs_header_level(buf);
1056
1057                         ret = btrfs_set_disk_extent_flags(trans, fs_info,
1058                                                           buf->start,
1059                                                           buf->len,
1060                                                           new_flags, level, 0);
1061                         if (ret)
1062                                 return ret;
1063                 }
1064         } else {
1065                 if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
1066                         if (root->root_key.objectid ==
1067                             BTRFS_TREE_RELOC_OBJECTID)
1068                                 ret = btrfs_inc_ref(trans, root, cow, 1);
1069                         else
1070                                 ret = btrfs_inc_ref(trans, root, cow, 0);
1071                         BUG_ON(ret); /* -ENOMEM */
1072                         ret = btrfs_dec_ref(trans, root, buf, 1);
1073                         BUG_ON(ret); /* -ENOMEM */
1074                 }
1075                 clean_tree_block(fs_info, buf);
1076                 *last_ref = 1;
1077         }
1078         return 0;
1079 }
1080
1081 /*
1082  * does the dirty work in cow of a single block.  The parent block (if
1083  * supplied) is updated to point to the new cow copy.  The new buffer is marked
1084  * dirty and returned locked.  If you modify the block it needs to be marked
1085  * dirty again.
1086  *
1087  * search_start -- an allocation hint for the new block
1088  *
1089  * empty_size -- a hint that you plan on doing more cow.  This is the size in
1090  * bytes the allocator should try to find free next to the block it returns.
1091  * This is just a hint and may be ignored by the allocator.
1092  */
1093 static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
1094                              struct btrfs_root *root,
1095                              struct extent_buffer *buf,
1096                              struct extent_buffer *parent, int parent_slot,
1097                              struct extent_buffer **cow_ret,
1098                              u64 search_start, u64 empty_size)
1099 {
1100         struct btrfs_fs_info *fs_info = root->fs_info;
1101         struct btrfs_disk_key disk_key;
1102         struct extent_buffer *cow;
1103         int level, ret;
1104         int last_ref = 0;
1105         int unlock_orig = 0;
1106         u64 parent_start = 0;
1107
1108         if (*cow_ret == buf)
1109                 unlock_orig = 1;
1110
1111         btrfs_assert_tree_locked(buf);
1112
1113         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1114                 trans->transid != fs_info->running_transaction->transid);
1115         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1116                 trans->transid != root->last_trans);
1117
1118         level = btrfs_header_level(buf);
1119
1120         if (level == 0)
1121                 btrfs_item_key(buf, &disk_key, 0);
1122         else
1123                 btrfs_node_key(buf, &disk_key, 0);
1124
1125         if ((root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) && parent)
1126                 parent_start = parent->start;
1127
1128         cow = btrfs_alloc_tree_block(trans, root, parent_start,
1129                         root->root_key.objectid, &disk_key, level,
1130                         search_start, empty_size);
1131         if (IS_ERR(cow))
1132                 return PTR_ERR(cow);
1133
1134         /* cow is set to blocking by btrfs_init_new_buffer */
1135
1136         copy_extent_buffer_full(cow, buf);
1137         btrfs_set_header_bytenr(cow, cow->start);
1138         btrfs_set_header_generation(cow, trans->transid);
1139         btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
1140         btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
1141                                      BTRFS_HEADER_FLAG_RELOC);
1142         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1143                 btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
1144         else
1145                 btrfs_set_header_owner(cow, root->root_key.objectid);
1146
1147         write_extent_buffer_fsid(cow, fs_info->fsid);
1148
1149         ret = update_ref_for_cow(trans, root, buf, cow, &last_ref);
1150         if (ret) {
1151                 btrfs_abort_transaction(trans, ret);
1152                 return ret;
1153         }
1154
1155         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
1156                 ret = btrfs_reloc_cow_block(trans, root, buf, cow);
1157                 if (ret) {
1158                         btrfs_abort_transaction(trans, ret);
1159                         return ret;
1160                 }
1161         }
1162
1163         if (buf == root->node) {
1164                 WARN_ON(parent && parent != buf);
1165                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
1166                     btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
1167                         parent_start = buf->start;
1168
1169                 extent_buffer_get(cow);
1170                 tree_mod_log_set_root_pointer(root, cow, 1);
1171                 rcu_assign_pointer(root->node, cow);
1172
1173                 btrfs_free_tree_block(trans, root, buf, parent_start,
1174                                       last_ref);
1175                 free_extent_buffer(buf);
1176                 add_root_to_dirty_list(root);
1177         } else {
1178                 WARN_ON(trans->transid != btrfs_header_generation(parent));
1179                 tree_mod_log_insert_key(fs_info, parent, parent_slot,
1180                                         MOD_LOG_KEY_REPLACE, GFP_NOFS);
1181                 btrfs_set_node_blockptr(parent, parent_slot,
1182                                         cow->start);
1183                 btrfs_set_node_ptr_generation(parent, parent_slot,
1184                                               trans->transid);
1185                 btrfs_mark_buffer_dirty(parent);
1186                 if (last_ref) {
1187                         ret = tree_mod_log_free_eb(fs_info, buf);
1188                         if (ret) {
1189                                 btrfs_abort_transaction(trans, ret);
1190                                 return ret;
1191                         }
1192                 }
1193                 btrfs_free_tree_block(trans, root, buf, parent_start,
1194                                       last_ref);
1195         }
1196         if (unlock_orig)
1197                 btrfs_tree_unlock(buf);
1198         free_extent_buffer_stale(buf);
1199         btrfs_mark_buffer_dirty(cow);
1200         *cow_ret = cow;
1201         return 0;
1202 }
1203
1204 /*
1205  * returns the logical address of the oldest predecessor of the given root.
1206  * entries older than time_seq are ignored.
1207  */
1208 static struct tree_mod_elem *
1209 __tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
1210                            struct extent_buffer *eb_root, u64 time_seq)
1211 {
1212         struct tree_mod_elem *tm;
1213         struct tree_mod_elem *found = NULL;
1214         u64 root_logical = eb_root->start;
1215         int looped = 0;
1216
1217         if (!time_seq)
1218                 return NULL;
1219
1220         /*
1221          * the very last operation that's logged for a root is the
1222          * replacement operation (if it is replaced at all). this has
1223          * the logical address of the *new* root, making it the very
1224          * first operation that's logged for this root.
1225          */
1226         while (1) {
1227                 tm = tree_mod_log_search_oldest(fs_info, root_logical,
1228                                                 time_seq);
1229                 if (!looped && !tm)
1230                         return NULL;
1231                 /*
1232                  * if there are no tree operation for the oldest root, we simply
1233                  * return it. this should only happen if that (old) root is at
1234                  * level 0.
1235                  */
1236                 if (!tm)
1237                         break;
1238
1239                 /*
1240                  * if there's an operation that's not a root replacement, we
1241                  * found the oldest version of our root. normally, we'll find a
1242                  * MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
1243                  */
1244                 if (tm->op != MOD_LOG_ROOT_REPLACE)
1245                         break;
1246
1247                 found = tm;
1248                 root_logical = tm->old_root.logical;
1249                 looped = 1;
1250         }
1251
1252         /* if there's no old root to return, return what we found instead */
1253         if (!found)
1254                 found = tm;
1255
1256         return found;
1257 }
1258
1259 /*
1260  * tm is a pointer to the first operation to rewind within eb. then, all
1261  * previous operations will be rewound (until we reach something older than
1262  * time_seq).
1263  */
1264 static void
1265 __tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
1266                       u64 time_seq, struct tree_mod_elem *first_tm)
1267 {
1268         u32 n;
1269         struct rb_node *next;
1270         struct tree_mod_elem *tm = first_tm;
1271         unsigned long o_dst;
1272         unsigned long o_src;
1273         unsigned long p_size = sizeof(struct btrfs_key_ptr);
1274
1275         n = btrfs_header_nritems(eb);
1276         tree_mod_log_read_lock(fs_info);
1277         while (tm && tm->seq >= time_seq) {
1278                 /*
1279                  * all the operations are recorded with the operator used for
1280                  * the modification. as we're going backwards, we do the
1281                  * opposite of each operation here.
1282                  */
1283                 switch (tm->op) {
1284                 case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
1285                         BUG_ON(tm->slot < n);
1286                         /* Fallthrough */
1287                 case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
1288                 case MOD_LOG_KEY_REMOVE:
1289                         btrfs_set_node_key(eb, &tm->key, tm->slot);
1290                         btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1291                         btrfs_set_node_ptr_generation(eb, tm->slot,
1292                                                       tm->generation);
1293                         n++;
1294                         break;
1295                 case MOD_LOG_KEY_REPLACE:
1296                         BUG_ON(tm->slot >= n);
1297                         btrfs_set_node_key(eb, &tm->key, tm->slot);
1298                         btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1299                         btrfs_set_node_ptr_generation(eb, tm->slot,
1300                                                       tm->generation);
1301                         break;
1302                 case MOD_LOG_KEY_ADD:
1303                         /* if a move operation is needed it's in the log */
1304                         n--;
1305                         break;
1306                 case MOD_LOG_MOVE_KEYS:
1307                         o_dst = btrfs_node_key_ptr_offset(tm->slot);
1308                         o_src = btrfs_node_key_ptr_offset(tm->move.dst_slot);
1309                         memmove_extent_buffer(eb, o_dst, o_src,
1310                                               tm->move.nr_items * p_size);
1311                         break;
1312                 case MOD_LOG_ROOT_REPLACE:
1313                         /*
1314                          * this operation is special. for roots, this must be
1315                          * handled explicitly before rewinding.
1316                          * for non-roots, this operation may exist if the node
1317                          * was a root: root A -> child B; then A gets empty and
1318                          * B is promoted to the new root. in the mod log, we'll
1319                          * have a root-replace operation for B, a tree block
1320                          * that is no root. we simply ignore that operation.
1321                          */
1322                         break;
1323                 }
1324                 next = rb_next(&tm->node);
1325                 if (!next)
1326                         break;
1327                 tm = rb_entry(next, struct tree_mod_elem, node);
1328                 if (tm->logical != first_tm->logical)
1329                         break;
1330         }
1331         tree_mod_log_read_unlock(fs_info);
1332         btrfs_set_header_nritems(eb, n);
1333 }
1334
1335 /*
1336  * Called with eb read locked. If the buffer cannot be rewound, the same buffer
1337  * is returned. If rewind operations happen, a fresh buffer is returned. The
1338  * returned buffer is always read-locked. If the returned buffer is not the
1339  * input buffer, the lock on the input buffer is released and the input buffer
1340  * is freed (its refcount is decremented).
1341  */
1342 static struct extent_buffer *
1343 tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
1344                     struct extent_buffer *eb, u64 time_seq)
1345 {
1346         struct extent_buffer *eb_rewin;
1347         struct tree_mod_elem *tm;
1348
1349         if (!time_seq)
1350                 return eb;
1351
1352         if (btrfs_header_level(eb) == 0)
1353                 return eb;
1354
1355         tm = tree_mod_log_search(fs_info, eb->start, time_seq);
1356         if (!tm)
1357                 return eb;
1358
1359         btrfs_set_path_blocking(path);
1360         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1361
1362         if (tm->op == MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1363                 BUG_ON(tm->slot != 0);
1364                 eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
1365                 if (!eb_rewin) {
1366                         btrfs_tree_read_unlock_blocking(eb);
1367                         free_extent_buffer(eb);
1368                         return NULL;
1369                 }
1370                 btrfs_set_header_bytenr(eb_rewin, eb->start);
1371                 btrfs_set_header_backref_rev(eb_rewin,
1372                                              btrfs_header_backref_rev(eb));
1373                 btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
1374                 btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
1375         } else {
1376                 eb_rewin = btrfs_clone_extent_buffer(eb);
1377                 if (!eb_rewin) {
1378                         btrfs_tree_read_unlock_blocking(eb);
1379                         free_extent_buffer(eb);
1380                         return NULL;
1381                 }
1382         }
1383
1384         btrfs_clear_path_blocking(path, NULL, BTRFS_READ_LOCK);
1385         btrfs_tree_read_unlock_blocking(eb);
1386         free_extent_buffer(eb);
1387
1388         extent_buffer_get(eb_rewin);
1389         btrfs_tree_read_lock(eb_rewin);
1390         __tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
1391         WARN_ON(btrfs_header_nritems(eb_rewin) >
1392                 BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1393
1394         return eb_rewin;
1395 }
1396
1397 /*
1398  * get_old_root() rewinds the state of @root's root node to the given @time_seq
1399  * value. If there are no changes, the current root->root_node is returned. If
1400  * anything changed in between, there's a fresh buffer allocated on which the
1401  * rewind operations are done. In any case, the returned buffer is read locked.
1402  * Returns NULL on error (with no locks held).
1403  */
1404 static inline struct extent_buffer *
1405 get_old_root(struct btrfs_root *root, u64 time_seq)
1406 {
1407         struct btrfs_fs_info *fs_info = root->fs_info;
1408         struct tree_mod_elem *tm;
1409         struct extent_buffer *eb = NULL;
1410         struct extent_buffer *eb_root;
1411         struct extent_buffer *old;
1412         struct tree_mod_root *old_root = NULL;
1413         u64 old_generation = 0;
1414         u64 logical;
1415
1416         eb_root = btrfs_read_lock_root_node(root);
1417         tm = __tree_mod_log_oldest_root(fs_info, eb_root, time_seq);
1418         if (!tm)
1419                 return eb_root;
1420
1421         if (tm->op == MOD_LOG_ROOT_REPLACE) {
1422                 old_root = &tm->old_root;
1423                 old_generation = tm->generation;
1424                 logical = old_root->logical;
1425         } else {
1426                 logical = eb_root->start;
1427         }
1428
1429         tm = tree_mod_log_search(fs_info, logical, time_seq);
1430         if (old_root && tm && tm->op != MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1431                 btrfs_tree_read_unlock(eb_root);
1432                 free_extent_buffer(eb_root);
1433                 old = read_tree_block(fs_info, logical, 0);
1434                 if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) {
1435                         if (!IS_ERR(old))
1436                                 free_extent_buffer(old);
1437                         btrfs_warn(fs_info,
1438                                    "failed to read tree block %llu from get_old_root",
1439                                    logical);
1440                 } else {
1441                         eb = btrfs_clone_extent_buffer(old);
1442                         free_extent_buffer(old);
1443                 }
1444         } else if (old_root) {
1445                 btrfs_tree_read_unlock(eb_root);
1446                 free_extent_buffer(eb_root);
1447                 eb = alloc_dummy_extent_buffer(fs_info, logical);
1448         } else {
1449                 btrfs_set_lock_blocking_rw(eb_root, BTRFS_READ_LOCK);
1450                 eb = btrfs_clone_extent_buffer(eb_root);
1451                 btrfs_tree_read_unlock_blocking(eb_root);
1452                 free_extent_buffer(eb_root);
1453         }
1454
1455         if (!eb)
1456                 return NULL;
1457         extent_buffer_get(eb);
1458         btrfs_tree_read_lock(eb);
1459         if (old_root) {
1460                 btrfs_set_header_bytenr(eb, eb->start);
1461                 btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
1462                 btrfs_set_header_owner(eb, btrfs_header_owner(eb_root));
1463                 btrfs_set_header_level(eb, old_root->level);
1464                 btrfs_set_header_generation(eb, old_generation);
1465         }
1466         if (tm)
1467                 __tree_mod_log_rewind(fs_info, eb, time_seq, tm);
1468         else
1469                 WARN_ON(btrfs_header_level(eb) != 0);
1470         WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1471
1472         return eb;
1473 }
1474
1475 int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
1476 {
1477         struct tree_mod_elem *tm;
1478         int level;
1479         struct extent_buffer *eb_root = btrfs_root_node(root);
1480
1481         tm = __tree_mod_log_oldest_root(root->fs_info, eb_root, time_seq);
1482         if (tm && tm->op == MOD_LOG_ROOT_REPLACE) {
1483                 level = tm->old_root.level;
1484         } else {
1485                 level = btrfs_header_level(eb_root);
1486         }
1487         free_extent_buffer(eb_root);
1488
1489         return level;
1490 }
1491
1492 static inline int should_cow_block(struct btrfs_trans_handle *trans,
1493                                    struct btrfs_root *root,
1494                                    struct extent_buffer *buf)
1495 {
1496         if (btrfs_is_testing(root->fs_info))
1497                 return 0;
1498
1499         /* ensure we can see the force_cow */
1500         smp_rmb();
1501
1502         /*
1503          * We do not need to cow a block if
1504          * 1) this block is not created or changed in this transaction;
1505          * 2) this block does not belong to TREE_RELOC tree;
1506          * 3) the root is not forced COW.
1507          *
1508          * What is forced COW:
1509          *    when we create snapshot during committing the transaction,
1510          *    after we've finished coping src root, we must COW the shared
1511          *    block to ensure the metadata consistency.
1512          */
1513         if (btrfs_header_generation(buf) == trans->transid &&
1514             !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) &&
1515             !(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
1516               btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)) &&
1517             !test_bit(BTRFS_ROOT_FORCE_COW, &root->state))
1518                 return 0;
1519         return 1;
1520 }
1521
1522 /*
1523  * cows a single block, see __btrfs_cow_block for the real work.
1524  * This version of it has extra checks so that a block isn't COWed more than
1525  * once per transaction, as long as it hasn't been written yet
1526  */
1527 noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
1528                     struct btrfs_root *root, struct extent_buffer *buf,
1529                     struct extent_buffer *parent, int parent_slot,
1530                     struct extent_buffer **cow_ret)
1531 {
1532         struct btrfs_fs_info *fs_info = root->fs_info;
1533         u64 search_start;
1534         int ret;
1535
1536         if (trans->transaction != fs_info->running_transaction)
1537                 WARN(1, KERN_CRIT "trans %llu running %llu\n",
1538                        trans->transid,
1539                        fs_info->running_transaction->transid);
1540
1541         if (trans->transid != fs_info->generation)
1542                 WARN(1, KERN_CRIT "trans %llu running %llu\n",
1543                        trans->transid, fs_info->generation);
1544
1545         if (!should_cow_block(trans, root, buf)) {
1546                 trans->dirty = true;
1547                 *cow_ret = buf;
1548                 return 0;
1549         }
1550
1551         search_start = buf->start & ~((u64)SZ_1G - 1);
1552
1553         if (parent)
1554                 btrfs_set_lock_blocking(parent);
1555         btrfs_set_lock_blocking(buf);
1556
1557         ret = __btrfs_cow_block(trans, root, buf, parent,
1558                                  parent_slot, cow_ret, search_start, 0);
1559
1560         trace_btrfs_cow_block(root, buf, *cow_ret);
1561
1562         return ret;
1563 }
1564
1565 /*
1566  * helper function for defrag to decide if two blocks pointed to by a
1567  * node are actually close by
1568  */
1569 static int close_blocks(u64 blocknr, u64 other, u32 blocksize)
1570 {
1571         if (blocknr < other && other - (blocknr + blocksize) < 32768)
1572                 return 1;
1573         if (blocknr > other && blocknr - (other + blocksize) < 32768)
1574                 return 1;
1575         return 0;
1576 }
1577
1578 /*
1579  * compare two keys in a memcmp fashion
1580  */
1581 static int comp_keys(const struct btrfs_disk_key *disk,
1582                      const struct btrfs_key *k2)
1583 {
1584         struct btrfs_key k1;
1585
1586         btrfs_disk_key_to_cpu(&k1, disk);
1587
1588         return btrfs_comp_cpu_keys(&k1, k2);
1589 }
1590
1591 /*
1592  * same as comp_keys only with two btrfs_key's
1593  */
1594 int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2)
1595 {
1596         if (k1->objectid > k2->objectid)
1597                 return 1;
1598         if (k1->objectid < k2->objectid)
1599                 return -1;
1600         if (k1->type > k2->type)
1601                 return 1;
1602         if (k1->type < k2->type)
1603                 return -1;
1604         if (k1->offset > k2->offset)
1605                 return 1;
1606         if (k1->offset < k2->offset)
1607                 return -1;
1608         return 0;
1609 }
1610
1611 /*
1612  * this is used by the defrag code to go through all the
1613  * leaves pointed to by a node and reallocate them so that
1614  * disk order is close to key order
1615  */
1616 int btrfs_realloc_node(struct btrfs_trans_handle *trans,
1617                        struct btrfs_root *root, struct extent_buffer *parent,
1618                        int start_slot, u64 *last_ret,
1619                        struct btrfs_key *progress)
1620 {
1621         struct btrfs_fs_info *fs_info = root->fs_info;
1622         struct extent_buffer *cur;
1623         u64 blocknr;
1624         u64 gen;
1625         u64 search_start = *last_ret;
1626         u64 last_block = 0;
1627         u64 other;
1628         u32 parent_nritems;
1629         int end_slot;
1630         int i;
1631         int err = 0;
1632         int parent_level;
1633         int uptodate;
1634         u32 blocksize;
1635         int progress_passed = 0;
1636         struct btrfs_disk_key disk_key;
1637
1638         parent_level = btrfs_header_level(parent);
1639
1640         WARN_ON(trans->transaction != fs_info->running_transaction);
1641         WARN_ON(trans->transid != fs_info->generation);
1642
1643         parent_nritems = btrfs_header_nritems(parent);
1644         blocksize = fs_info->nodesize;
1645         end_slot = parent_nritems - 1;
1646
1647         if (parent_nritems <= 1)
1648                 return 0;
1649
1650         btrfs_set_lock_blocking(parent);
1651
1652         for (i = start_slot; i <= end_slot; i++) {
1653                 int close = 1;
1654
1655                 btrfs_node_key(parent, &disk_key, i);
1656                 if (!progress_passed && comp_keys(&disk_key, progress) < 0)
1657                         continue;
1658
1659                 progress_passed = 1;
1660                 blocknr = btrfs_node_blockptr(parent, i);
1661                 gen = btrfs_node_ptr_generation(parent, i);
1662                 if (last_block == 0)
1663                         last_block = blocknr;
1664
1665                 if (i > 0) {
1666                         other = btrfs_node_blockptr(parent, i - 1);
1667                         close = close_blocks(blocknr, other, blocksize);
1668                 }
1669                 if (!close && i < end_slot) {
1670                         other = btrfs_node_blockptr(parent, i + 1);
1671                         close = close_blocks(blocknr, other, blocksize);
1672                 }
1673                 if (close) {
1674                         last_block = blocknr;
1675                         continue;
1676                 }
1677
1678                 cur = find_extent_buffer(fs_info, blocknr);
1679                 if (cur)
1680                         uptodate = btrfs_buffer_uptodate(cur, gen, 0);
1681                 else
1682                         uptodate = 0;
1683                 if (!cur || !uptodate) {
1684                         if (!cur) {
1685                                 cur = read_tree_block(fs_info, blocknr, gen);
1686                                 if (IS_ERR(cur)) {
1687                                         return PTR_ERR(cur);
1688                                 } else if (!extent_buffer_uptodate(cur)) {
1689                                         free_extent_buffer(cur);
1690                                         return -EIO;
1691                                 }
1692                         } else if (!uptodate) {
1693                                 err = btrfs_read_buffer(cur, gen);
1694                                 if (err) {
1695                                         free_extent_buffer(cur);
1696                                         return err;
1697                                 }
1698                         }
1699                 }
1700                 if (search_start == 0)
1701                         search_start = last_block;
1702
1703                 btrfs_tree_lock(cur);
1704                 btrfs_set_lock_blocking(cur);
1705                 err = __btrfs_cow_block(trans, root, cur, parent, i,
1706                                         &cur, search_start,
1707                                         min(16 * blocksize,
1708                                             (end_slot - i) * blocksize));
1709                 if (err) {
1710                         btrfs_tree_unlock(cur);
1711                         free_extent_buffer(cur);
1712                         break;
1713                 }
1714                 search_start = cur->start;
1715                 last_block = cur->start;
1716                 *last_ret = search_start;
1717                 btrfs_tree_unlock(cur);
1718                 free_extent_buffer(cur);
1719         }
1720         return err;
1721 }
1722
1723 /*
1724  * search for key in the extent_buffer.  The items start at offset p,
1725  * and they are item_size apart.  There are 'max' items in p.
1726  *
1727  * the slot in the array is returned via slot, and it points to
1728  * the place where you would insert key if it is not found in
1729  * the array.
1730  *
1731  * slot may point to max if the key is bigger than all of the keys
1732  */
1733 static noinline int generic_bin_search(struct extent_buffer *eb,
1734                                        unsigned long p, int item_size,
1735                                        const struct btrfs_key *key,
1736                                        int max, int *slot)
1737 {
1738         int low = 0;
1739         int high = max;
1740         int mid;
1741         int ret;
1742         struct btrfs_disk_key *tmp = NULL;
1743         struct btrfs_disk_key unaligned;
1744         unsigned long offset;
1745         char *kaddr = NULL;
1746         unsigned long map_start = 0;
1747         unsigned long map_len = 0;
1748         int err;
1749
1750         if (low > high) {
1751                 btrfs_err(eb->fs_info,
1752                  "%s: low (%d) > high (%d) eb %llu owner %llu level %d",
1753                           __func__, low, high, eb->start,
1754                           btrfs_header_owner(eb), btrfs_header_level(eb));
1755                 return -EINVAL;
1756         }
1757
1758         while (low < high) {
1759                 mid = (low + high) / 2;
1760                 offset = p + mid * item_size;
1761
1762                 if (!kaddr || offset < map_start ||
1763                     (offset + sizeof(struct btrfs_disk_key)) >
1764                     map_start + map_len) {
1765
1766                         err = map_private_extent_buffer(eb, offset,
1767                                                 sizeof(struct btrfs_disk_key),
1768                                                 &kaddr, &map_start, &map_len);
1769
1770                         if (!err) {
1771                                 tmp = (struct btrfs_disk_key *)(kaddr + offset -
1772                                                         map_start);
1773                         } else if (err == 1) {
1774                                 read_extent_buffer(eb, &unaligned,
1775                                                    offset, sizeof(unaligned));
1776                                 tmp = &unaligned;
1777                         } else {
1778                                 return err;
1779                         }
1780
1781                 } else {
1782                         tmp = (struct btrfs_disk_key *)(kaddr + offset -
1783                                                         map_start);
1784                 }
1785                 ret = comp_keys(tmp, key);
1786
1787                 if (ret < 0)
1788                         low = mid + 1;
1789                 else if (ret > 0)
1790                         high = mid;
1791                 else {
1792                         *slot = mid;
1793                         return 0;
1794                 }
1795         }
1796         *slot = low;
1797         return 1;
1798 }
1799
1800 /*
1801  * simple bin_search frontend that does the right thing for
1802  * leaves vs nodes
1803  */
1804 static int bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
1805                       int level, int *slot)
1806 {
1807         if (level == 0)
1808                 return generic_bin_search(eb,
1809                                           offsetof(struct btrfs_leaf, items),
1810                                           sizeof(struct btrfs_item),
1811                                           key, btrfs_header_nritems(eb),
1812                                           slot);
1813         else
1814                 return generic_bin_search(eb,
1815                                           offsetof(struct btrfs_node, ptrs),
1816                                           sizeof(struct btrfs_key_ptr),
1817                                           key, btrfs_header_nritems(eb),
1818                                           slot);
1819 }
1820
1821 int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
1822                      int level, int *slot)
1823 {
1824         return bin_search(eb, key, level, 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 = 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  * look for key in the tree.  path is filled in with nodes along the way
2658  * if key is found, we return zero and you can find the item in the leaf
2659  * level of the path (level 0)
2660  *
2661  * If the key isn't found, the path points to the slot where it should
2662  * be inserted, and 1 is returned.  If there are other errors during the
2663  * search a negative error number is returned.
2664  *
2665  * if ins_len > 0, nodes and leaves will be split as we walk down the
2666  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
2667  * possible)
2668  */
2669 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
2670                       const struct btrfs_key *key, struct btrfs_path *p,
2671                       int ins_len, int cow)
2672 {
2673         struct btrfs_fs_info *fs_info = root->fs_info;
2674         struct extent_buffer *b;
2675         int slot;
2676         int ret;
2677         int err;
2678         int level;
2679         int lowest_unlock = 1;
2680         int root_lock;
2681         /* everything at write_lock_level or lower must be write locked */
2682         int write_lock_level = 0;
2683         u8 lowest_level = 0;
2684         int min_write_lock_level;
2685         int prev_cmp;
2686
2687         lowest_level = p->lowest_level;
2688         WARN_ON(lowest_level && ins_len > 0);
2689         WARN_ON(p->nodes[0] != NULL);
2690         BUG_ON(!cow && ins_len);
2691
2692         if (ins_len < 0) {
2693                 lowest_unlock = 2;
2694
2695                 /* when we are removing items, we might have to go up to level
2696                  * two as we update tree pointers  Make sure we keep write
2697                  * for those levels as well
2698                  */
2699                 write_lock_level = 2;
2700         } else if (ins_len > 0) {
2701                 /*
2702                  * for inserting items, make sure we have a write lock on
2703                  * level 1 so we can update keys
2704                  */
2705                 write_lock_level = 1;
2706         }
2707
2708         if (!cow)
2709                 write_lock_level = -1;
2710
2711         if (cow && (p->keep_locks || p->lowest_level))
2712                 write_lock_level = BTRFS_MAX_LEVEL;
2713
2714         min_write_lock_level = write_lock_level;
2715
2716 again:
2717         prev_cmp = -1;
2718         /*
2719          * we try very hard to do read locks on the root
2720          */
2721         root_lock = BTRFS_READ_LOCK;
2722         level = 0;
2723         if (p->search_commit_root) {
2724                 /*
2725                  * the commit roots are read only
2726                  * so we always do read locks
2727                  */
2728                 if (p->need_commit_sem)
2729                         down_read(&fs_info->commit_root_sem);
2730                 b = root->commit_root;
2731                 extent_buffer_get(b);
2732                 level = btrfs_header_level(b);
2733                 if (p->need_commit_sem)
2734                         up_read(&fs_info->commit_root_sem);
2735                 if (!p->skip_locking)
2736                         btrfs_tree_read_lock(b);
2737         } else {
2738                 if (p->skip_locking) {
2739                         b = btrfs_root_node(root);
2740                         level = btrfs_header_level(b);
2741                 } else {
2742                         /* we don't know the level of the root node
2743                          * until we actually have it read locked
2744                          */
2745                         b = btrfs_read_lock_root_node(root);
2746                         level = btrfs_header_level(b);
2747                         if (level <= write_lock_level) {
2748                                 /* whoops, must trade for write lock */
2749                                 btrfs_tree_read_unlock(b);
2750                                 free_extent_buffer(b);
2751                                 b = btrfs_lock_root_node(root);
2752                                 root_lock = BTRFS_WRITE_LOCK;
2753
2754                                 /* the level might have changed, check again */
2755                                 level = btrfs_header_level(b);
2756                         }
2757                 }
2758         }
2759         p->nodes[level] = b;
2760         if (!p->skip_locking)
2761                 p->locks[level] = root_lock;
2762
2763         while (b) {
2764                 level = btrfs_header_level(b);
2765
2766                 /*
2767                  * setup the path here so we can release it under lock
2768                  * contention with the cow code
2769                  */
2770                 if (cow) {
2771                         /*
2772                          * if we don't really need to cow this block
2773                          * then we don't want to set the path blocking,
2774                          * so we test it here
2775                          */
2776                         if (!should_cow_block(trans, root, b)) {
2777                                 trans->dirty = true;
2778                                 goto cow_done;
2779                         }
2780
2781                         /*
2782                          * must have write locks on this node and the
2783                          * parent
2784                          */
2785                         if (level > write_lock_level ||
2786                             (level + 1 > write_lock_level &&
2787                             level + 1 < BTRFS_MAX_LEVEL &&
2788                             p->nodes[level + 1])) {
2789                                 write_lock_level = level + 1;
2790                                 btrfs_release_path(p);
2791                                 goto again;
2792                         }
2793
2794                         btrfs_set_path_blocking(p);
2795                         err = btrfs_cow_block(trans, root, b,
2796                                               p->nodes[level + 1],
2797                                               p->slots[level + 1], &b);
2798                         if (err) {
2799                                 ret = err;
2800                                 goto done;
2801                         }
2802                 }
2803 cow_done:
2804                 p->nodes[level] = b;
2805                 btrfs_clear_path_blocking(p, NULL, 0);
2806
2807                 /*
2808                  * we have a lock on b and as long as we aren't changing
2809                  * the tree, there is no way to for the items in b to change.
2810                  * It is safe to drop the lock on our parent before we
2811                  * go through the expensive btree search on b.
2812                  *
2813                  * If we're inserting or deleting (ins_len != 0), then we might
2814                  * be changing slot zero, which may require changing the parent.
2815                  * So, we can't drop the lock until after we know which slot
2816                  * we're operating on.
2817                  */
2818                 if (!ins_len && !p->keep_locks) {
2819                         int u = level + 1;
2820
2821                         if (u < BTRFS_MAX_LEVEL && p->locks[u]) {
2822                                 btrfs_tree_unlock_rw(p->nodes[u], p->locks[u]);
2823                                 p->locks[u] = 0;
2824                         }
2825                 }
2826
2827                 ret = key_search(b, key, level, &prev_cmp, &slot);
2828                 if (ret < 0)
2829                         goto done;
2830
2831                 if (level != 0) {
2832                         int dec = 0;
2833                         if (ret && slot > 0) {
2834                                 dec = 1;
2835                                 slot -= 1;
2836                         }
2837                         p->slots[level] = slot;
2838                         err = setup_nodes_for_search(trans, root, p, b, level,
2839                                              ins_len, &write_lock_level);
2840                         if (err == -EAGAIN)
2841                                 goto again;
2842                         if (err) {
2843                                 ret = err;
2844                                 goto done;
2845                         }
2846                         b = p->nodes[level];
2847                         slot = p->slots[level];
2848
2849                         /*
2850                          * slot 0 is special, if we change the key
2851                          * we have to update the parent pointer
2852                          * which means we must have a write lock
2853                          * on the parent
2854                          */
2855                         if (slot == 0 && ins_len &&
2856                             write_lock_level < level + 1) {
2857                                 write_lock_level = level + 1;
2858                                 btrfs_release_path(p);
2859                                 goto again;
2860                         }
2861
2862                         unlock_up(p, level, lowest_unlock,
2863                                   min_write_lock_level, &write_lock_level);
2864
2865                         if (level == lowest_level) {
2866                                 if (dec)
2867                                         p->slots[level]++;
2868                                 goto done;
2869                         }
2870
2871                         err = read_block_for_search(root, p, &b, level,
2872                                                     slot, key);
2873                         if (err == -EAGAIN)
2874                                 goto again;
2875                         if (err) {
2876                                 ret = err;
2877                                 goto done;
2878                         }
2879
2880                         if (!p->skip_locking) {
2881                                 level = btrfs_header_level(b);
2882                                 if (level <= write_lock_level) {
2883                                         err = btrfs_try_tree_write_lock(b);
2884                                         if (!err) {
2885                                                 btrfs_set_path_blocking(p);
2886                                                 btrfs_tree_lock(b);
2887                                                 btrfs_clear_path_blocking(p, b,
2888                                                                   BTRFS_WRITE_LOCK);
2889                                         }
2890                                         p->locks[level] = BTRFS_WRITE_LOCK;
2891                                 } else {
2892                                         err = btrfs_tree_read_lock_atomic(b);
2893                                         if (!err) {
2894                                                 btrfs_set_path_blocking(p);
2895                                                 btrfs_tree_read_lock(b);
2896                                                 btrfs_clear_path_blocking(p, b,
2897                                                                   BTRFS_READ_LOCK);
2898                                         }
2899                                         p->locks[level] = BTRFS_READ_LOCK;
2900                                 }
2901                                 p->nodes[level] = b;
2902                         }
2903                 } else {
2904                         p->slots[level] = slot;
2905                         if (ins_len > 0 &&
2906                             btrfs_leaf_free_space(fs_info, b) < ins_len) {
2907                                 if (write_lock_level < 1) {
2908                                         write_lock_level = 1;
2909                                         btrfs_release_path(p);
2910                                         goto again;
2911                                 }
2912
2913                                 btrfs_set_path_blocking(p);
2914                                 err = split_leaf(trans, root, key,
2915                                                  p, ins_len, ret == 0);
2916                                 btrfs_clear_path_blocking(p, NULL, 0);
2917
2918                                 BUG_ON(err > 0);
2919                                 if (err) {
2920                                         ret = err;
2921                                         goto done;
2922                                 }
2923                         }
2924                         if (!p->search_for_split)
2925                                 unlock_up(p, level, lowest_unlock,
2926                                           min_write_lock_level, &write_lock_level);
2927                         goto done;
2928                 }
2929         }
2930         ret = 1;
2931 done:
2932         /*
2933          * we don't really know what they plan on doing with the path
2934          * from here on, so for now just mark it as blocking
2935          */
2936         if (!p->leave_spinning)
2937                 btrfs_set_path_blocking(p);
2938         if (ret < 0 && !p->skip_release_on_error)
2939                 btrfs_release_path(p);
2940         return ret;
2941 }
2942
2943 /*
2944  * Like btrfs_search_slot, this looks for a key in the given tree. It uses the
2945  * current state of the tree together with the operations recorded in the tree
2946  * modification log to search for the key in a previous version of this tree, as
2947  * denoted by the time_seq parameter.
2948  *
2949  * Naturally, there is no support for insert, delete or cow operations.
2950  *
2951  * The resulting path and return value will be set up as if we called
2952  * btrfs_search_slot at that point in time with ins_len and cow both set to 0.
2953  */
2954 int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key,
2955                           struct btrfs_path *p, u64 time_seq)
2956 {
2957         struct btrfs_fs_info *fs_info = root->fs_info;
2958         struct extent_buffer *b;
2959         int slot;
2960         int ret;
2961         int err;
2962         int level;
2963         int lowest_unlock = 1;
2964         u8 lowest_level = 0;
2965         int prev_cmp = -1;
2966
2967         lowest_level = p->lowest_level;
2968         WARN_ON(p->nodes[0] != NULL);
2969
2970         if (p->search_commit_root) {
2971                 BUG_ON(time_seq);
2972                 return btrfs_search_slot(NULL, root, key, p, 0, 0);
2973         }
2974
2975 again:
2976         b = get_old_root(root, time_seq);
2977         level = btrfs_header_level(b);
2978         p->locks[level] = BTRFS_READ_LOCK;
2979
2980         while (b) {
2981                 level = btrfs_header_level(b);
2982                 p->nodes[level] = b;
2983                 btrfs_clear_path_blocking(p, NULL, 0);
2984
2985                 /*
2986                  * we have a lock on b and as long as we aren't changing
2987                  * the tree, there is no way to for the items in b to change.
2988                  * It is safe to drop the lock on our parent before we
2989                  * go through the expensive btree search on b.
2990                  */
2991                 btrfs_unlock_up_safe(p, level + 1);
2992
2993                 /*
2994                  * Since we can unwind ebs we want to do a real search every
2995                  * time.
2996                  */
2997                 prev_cmp = -1;
2998                 ret = key_search(b, key, level, &prev_cmp, &slot);
2999
3000                 if (level != 0) {
3001                         int dec = 0;
3002                         if (ret && slot > 0) {
3003                                 dec = 1;
3004                                 slot -= 1;
3005                         }
3006                         p->slots[level] = slot;
3007                         unlock_up(p, level, lowest_unlock, 0, NULL);
3008
3009                         if (level == lowest_level) {
3010                                 if (dec)
3011                                         p->slots[level]++;
3012                                 goto done;
3013                         }
3014
3015                         err = read_block_for_search(root, p, &b, level,
3016                                                     slot, key);
3017                         if (err == -EAGAIN)
3018                                 goto again;
3019                         if (err) {
3020                                 ret = err;
3021                                 goto done;
3022                         }
3023
3024                         level = btrfs_header_level(b);
3025                         err = btrfs_tree_read_lock_atomic(b);
3026                         if (!err) {
3027                                 btrfs_set_path_blocking(p);
3028                                 btrfs_tree_read_lock(b);
3029                                 btrfs_clear_path_blocking(p, b,
3030                                                           BTRFS_READ_LOCK);
3031                         }
3032                         b = tree_mod_log_rewind(fs_info, p, b, time_seq);
3033                         if (!b) {
3034                                 ret = -ENOMEM;
3035                                 goto done;
3036                         }
3037                         p->locks[level] = BTRFS_READ_LOCK;
3038                         p->nodes[level] = b;
3039                 } else {
3040                         p->slots[level] = slot;
3041                         unlock_up(p, level, lowest_unlock, 0, NULL);
3042                         goto done;
3043                 }
3044         }
3045         ret = 1;
3046 done:
3047         if (!p->leave_spinning)
3048                 btrfs_set_path_blocking(p);
3049         if (ret < 0)
3050                 btrfs_release_path(p);
3051
3052         return ret;
3053 }
3054
3055 /*
3056  * helper to use instead of search slot if no exact match is needed but
3057  * instead the next or previous item should be returned.
3058  * When find_higher is true, the next higher item is returned, the next lower
3059  * otherwise.
3060  * When return_any and find_higher are both true, and no higher item is found,
3061  * return the next lower instead.
3062  * When return_any is true and find_higher is false, and no lower item is found,
3063  * return the next higher instead.
3064  * It returns 0 if any item is found, 1 if none is found (tree empty), and
3065  * < 0 on error
3066  */
3067 int btrfs_search_slot_for_read(struct btrfs_root *root,
3068                                const struct btrfs_key *key,
3069                                struct btrfs_path *p, int find_higher,
3070                                int return_any)
3071 {
3072         int ret;
3073         struct extent_buffer *leaf;
3074
3075 again:
3076         ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
3077         if (ret <= 0)
3078                 return ret;
3079         /*
3080          * a return value of 1 means the path is at the position where the
3081          * item should be inserted. Normally this is the next bigger item,
3082          * but in case the previous item is the last in a leaf, path points
3083          * to the first free slot in the previous leaf, i.e. at an invalid
3084          * item.
3085          */
3086         leaf = p->nodes[0];
3087
3088         if (find_higher) {
3089                 if (p->slots[0] >= btrfs_header_nritems(leaf)) {
3090                         ret = btrfs_next_leaf(root, p);
3091                         if (ret <= 0)
3092                                 return ret;
3093                         if (!return_any)
3094                                 return 1;
3095                         /*
3096                          * no higher item found, return the next
3097                          * lower instead
3098                          */
3099                         return_any = 0;
3100                         find_higher = 0;
3101                         btrfs_release_path(p);
3102                         goto again;
3103                 }
3104         } else {
3105                 if (p->slots[0] == 0) {
3106                         ret = btrfs_prev_leaf(root, p);
3107                         if (ret < 0)
3108                                 return ret;
3109                         if (!ret) {
3110                                 leaf = p->nodes[0];
3111                                 if (p->slots[0] == btrfs_header_nritems(leaf))
3112                                         p->slots[0]--;
3113                                 return 0;
3114                         }
3115                         if (!return_any)
3116                                 return 1;
3117                         /*
3118                          * no lower item found, return the next
3119                          * higher instead
3120                          */
3121                         return_any = 0;
3122                         find_higher = 1;
3123                         btrfs_release_path(p);
3124                         goto again;
3125                 } else {
3126                         --p->slots[0];
3127                 }
3128         }
3129         return 0;
3130 }
3131
3132 /*
3133  * adjust the pointers going up the tree, starting at level
3134  * making sure the right key of each node is points to 'key'.
3135  * This is used after shifting pointers to the left, so it stops
3136  * fixing up pointers when a given leaf/node is not in slot 0 of the
3137  * higher levels
3138  *
3139  */
3140 static void fixup_low_keys(struct btrfs_fs_info *fs_info,
3141                            struct btrfs_path *path,
3142                            struct btrfs_disk_key *key, int level)
3143 {
3144         int i;
3145         struct extent_buffer *t;
3146
3147         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
3148                 int tslot = path->slots[i];
3149                 if (!path->nodes[i])
3150                         break;
3151                 t = path->nodes[i];
3152                 tree_mod_log_set_node_key(fs_info, t, tslot, 1);
3153                 btrfs_set_node_key(t, key, tslot);
3154                 btrfs_mark_buffer_dirty(path->nodes[i]);
3155                 if (tslot != 0)
3156                         break;
3157         }
3158 }
3159
3160 /*
3161  * update item key.
3162  *
3163  * This function isn't completely safe. It's the caller's responsibility
3164  * that the new key won't break the order
3165  */
3166 void btrfs_set_item_key_safe(struct btrfs_fs_info *fs_info,
3167                              struct btrfs_path *path,
3168                              const struct btrfs_key *new_key)
3169 {
3170         struct btrfs_disk_key disk_key;
3171         struct extent_buffer *eb;
3172         int slot;
3173
3174         eb = path->nodes[0];
3175         slot = path->slots[0];
3176         if (slot > 0) {
3177                 btrfs_item_key(eb, &disk_key, slot - 1);
3178                 BUG_ON(comp_keys(&disk_key, new_key) >= 0);
3179         }
3180         if (slot < btrfs_header_nritems(eb) - 1) {
3181                 btrfs_item_key(eb, &disk_key, slot + 1);
3182                 BUG_ON(comp_keys(&disk_key, new_key) <= 0);
3183         }
3184
3185         btrfs_cpu_key_to_disk(&disk_key, new_key);
3186         btrfs_set_item_key(eb, &disk_key, slot);
3187         btrfs_mark_buffer_dirty(eb);
3188         if (slot == 0)
3189                 fixup_low_keys(fs_info, path, &disk_key, 1);
3190 }
3191
3192 /*
3193  * try to push data from one node into the next node left in the
3194  * tree.
3195  *
3196  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
3197  * error, and > 0 if there was no room in the left hand block.
3198  */
3199 static int push_node_left(struct btrfs_trans_handle *trans,
3200                           struct btrfs_fs_info *fs_info,
3201                           struct extent_buffer *dst,
3202                           struct extent_buffer *src, int empty)
3203 {
3204         int push_items = 0;
3205         int src_nritems;
3206         int dst_nritems;
3207         int ret = 0;
3208
3209         src_nritems = btrfs_header_nritems(src);
3210         dst_nritems = btrfs_header_nritems(dst);
3211         push_items = BTRFS_NODEPTRS_PER_BLOCK(fs_info) - dst_nritems;
3212         WARN_ON(btrfs_header_generation(src) != trans->transid);
3213         WARN_ON(btrfs_header_generation(dst) != trans->transid);
3214
3215         if (!empty && src_nritems <= 8)
3216                 return 1;
3217
3218         if (push_items <= 0)
3219                 return 1;
3220
3221         if (empty) {
3222                 push_items = min(src_nritems, push_items);
3223                 if (push_items < src_nritems) {
3224                         /* leave at least 8 pointers in the node if
3225                          * we aren't going to empty it
3226                          */
3227                         if (src_nritems - push_items < 8) {
3228                                 if (push_items <= 8)
3229                                         return 1;
3230                                 push_items -= 8;
3231                         }
3232                 }
3233         } else
3234                 push_items = min(src_nritems - 8, push_items);
3235
3236         ret = tree_mod_log_eb_copy(fs_info, dst, src, dst_nritems, 0,
3237                                    push_items);
3238         if (ret) {
3239                 btrfs_abort_transaction(trans, ret);
3240                 return ret;
3241         }
3242         copy_extent_buffer(dst, src,
3243                            btrfs_node_key_ptr_offset(dst_nritems),
3244                            btrfs_node_key_ptr_offset(0),
3245                            push_items * sizeof(struct btrfs_key_ptr));
3246
3247         if (push_items < src_nritems) {
3248                 /*
3249                  * don't call tree_mod_log_eb_move here, key removal was already
3250                  * fully logged by tree_mod_log_eb_copy above.
3251                  */
3252                 memmove_extent_buffer(src, btrfs_node_key_ptr_offset(0),
3253                                       btrfs_node_key_ptr_offset(push_items),
3254                                       (src_nritems - push_items) *
3255                                       sizeof(struct btrfs_key_ptr));
3256         }
3257         btrfs_set_header_nritems(src, src_nritems - push_items);
3258         btrfs_set_header_nritems(dst, dst_nritems + push_items);
3259         btrfs_mark_buffer_dirty(src);
3260         btrfs_mark_buffer_dirty(dst);
3261
3262         return ret;
3263 }
3264
3265 /*
3266  * try to push data from one node into the next node right in the
3267  * tree.
3268  *
3269  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
3270  * error, and > 0 if there was no room in the right hand block.
3271  *
3272  * this will  only push up to 1/2 the contents of the left node over
3273  */
3274 static int balance_node_right(struct btrfs_trans_handle *trans,
3275                               struct btrfs_fs_info *fs_info,
3276                               struct extent_buffer *dst,
3277                               struct extent_buffer *src)
3278 {
3279         int push_items = 0;
3280         int max_push;
3281         int src_nritems;
3282         int dst_nritems;
3283         int ret = 0;
3284
3285         WARN_ON(btrfs_header_generation(src) != trans->transid);
3286         WARN_ON(btrfs_header_generation(dst) != trans->transid);
3287
3288         src_nritems = btrfs_header_nritems(src);
3289         dst_nritems = btrfs_header_nritems(dst);
3290         push_items = BTRFS_NODEPTRS_PER_BLOCK(fs_info) - dst_nritems;
3291         if (push_items <= 0)
3292                 return 1;
3293
3294         if (src_nritems < 4)
3295                 return 1;
3296
3297         max_push = src_nritems / 2 + 1;
3298         /* don't try to empty the node */
3299         if (max_push >= src_nritems)
3300                 return 1;
3301
3302         if (max_push < push_items)
3303                 push_items = max_push;
3304
3305         tree_mod_log_eb_move(fs_info, dst, push_items, 0, dst_nritems);
3306         memmove_extent_buffer(dst, btrfs_node_key_ptr_offset(push_items),
3307                                       btrfs_node_key_ptr_offset(0),
3308                                       (dst_nritems) *
3309                                       sizeof(struct btrfs_key_ptr));
3310
3311         ret = tree_mod_log_eb_copy(fs_info, dst, src, 0,
3312                                    src_nritems - push_items, push_items);
3313         if (ret) {
3314                 btrfs_abort_transaction(trans, ret);
3315                 return ret;
3316         }
3317         copy_extent_buffer(dst, src,
3318                            btrfs_node_key_ptr_offset(0),
3319                            btrfs_node_key_ptr_offset(src_nritems - push_items),
3320                            push_items * sizeof(struct btrfs_key_ptr));
3321
3322         btrfs_set_header_nritems(src, src_nritems - push_items);
3323         btrfs_set_header_nritems(dst, dst_nritems + push_items);
3324
3325         btrfs_mark_buffer_dirty(src);
3326         btrfs_mark_buffer_dirty(dst);
3327
3328         return ret;
3329 }
3330
3331 /*
3332  * helper function to insert a new root level in the tree.
3333  * A new node is allocated, and a single item is inserted to
3334  * point to the existing root
3335  *
3336  * returns zero on success or < 0 on failure.
3337  */
3338 static noinline int insert_new_root(struct btrfs_trans_handle *trans,
3339                            struct btrfs_root *root,
3340                            struct btrfs_path *path, int level)
3341 {
3342         struct btrfs_fs_info *fs_info = root->fs_info;
3343         u64 lower_gen;
3344         struct extent_buffer *lower;
3345         struct extent_buffer *c;
3346         struct extent_buffer *old;
3347         struct btrfs_disk_key lower_key;
3348
3349         BUG_ON(path->nodes[level]);
3350         BUG_ON(path->nodes[level-1] != root->node);
3351
3352         lower = path->nodes[level-1];
3353         if (level == 1)
3354                 btrfs_item_key(lower, &lower_key, 0);
3355         else
3356                 btrfs_node_key(lower, &lower_key, 0);
3357
3358         c = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
3359                                    &lower_key, level, root->node->start, 0);
3360         if (IS_ERR(c))
3361                 return PTR_ERR(c);
3362
3363         root_add_used(root, fs_info->nodesize);
3364
3365         memzero_extent_buffer(c, 0, sizeof(struct btrfs_header));
3366         btrfs_set_header_nritems(c, 1);
3367         btrfs_set_header_level(c, level);
3368         btrfs_set_header_bytenr(c, c->start);
3369         btrfs_set_header_generation(c, trans->transid);
3370         btrfs_set_header_backref_rev(c, BTRFS_MIXED_BACKREF_REV);
3371         btrfs_set_header_owner(c, root->root_key.objectid);
3372
3373         write_extent_buffer_fsid(c, fs_info->fsid);
3374         write_extent_buffer_chunk_tree_uuid(c, fs_info->chunk_tree_uuid);
3375
3376         btrfs_set_node_key(c, &lower_key, 0);
3377         btrfs_set_node_blockptr(c, 0, lower->start);
3378         lower_gen = btrfs_header_generation(lower);
3379         WARN_ON(lower_gen != trans->transid);
3380
3381         btrfs_set_node_ptr_generation(c, 0, lower_gen);
3382
3383         btrfs_mark_buffer_dirty(c);
3384
3385         old = root->node;
3386         tree_mod_log_set_root_pointer(root, c, 0);
3387         rcu_assign_pointer(root->node, c);
3388
3389         /* the super has an extra ref to root->node */
3390         free_extent_buffer(old);
3391
3392         add_root_to_dirty_list(root);
3393         extent_buffer_get(c);
3394         path->nodes[level] = c;
3395         path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
3396         path->slots[level] = 0;
3397         return 0;
3398 }
3399
3400 /*
3401  * worker function to insert a single pointer in a node.
3402  * the node should have enough room for the pointer already
3403  *
3404  * slot and level indicate where you want the key to go, and
3405  * blocknr is the block the key points to.
3406  */
3407 static void insert_ptr(struct btrfs_trans_handle *trans,
3408                        struct btrfs_fs_info *fs_info, struct btrfs_path *path,
3409                        struct btrfs_disk_key *key, u64 bytenr,
3410                        int slot, int level)
3411 {
3412         struct extent_buffer *lower;
3413         int nritems;
3414         int ret;
3415
3416         BUG_ON(!path->nodes[level]);
3417         btrfs_assert_tree_locked(path->nodes[level]);
3418         lower = path->nodes[level];
3419         nritems = btrfs_header_nritems(lower);
3420         BUG_ON(slot > nritems);
3421         BUG_ON(nritems == BTRFS_NODEPTRS_PER_BLOCK(fs_info));
3422         if (slot != nritems) {
3423                 if (level)
3424                         tree_mod_log_eb_move(fs_info, lower, slot + 1,
3425                                              slot, nritems - slot);
3426                 memmove_extent_buffer(lower,
3427                               btrfs_node_key_ptr_offset(slot + 1),
3428                               btrfs_node_key_ptr_offset(slot),
3429                               (nritems - slot) * sizeof(struct btrfs_key_ptr));
3430         }
3431         if (level) {
3432                 ret = tree_mod_log_insert_key(fs_info, lower, slot,
3433                                               MOD_LOG_KEY_ADD, GFP_NOFS);
3434                 BUG_ON(ret < 0);
3435         }
3436         btrfs_set_node_key(lower, key, slot);
3437         btrfs_set_node_blockptr(lower, slot, bytenr);
3438         WARN_ON(trans->transid == 0);
3439         btrfs_set_node_ptr_generation(lower, slot, trans->transid);
3440         btrfs_set_header_nritems(lower, nritems + 1);
3441         btrfs_mark_buffer_dirty(lower);
3442 }
3443
3444 /*
3445  * split the node at the specified level in path in two.
3446  * The path is corrected to point to the appropriate node after the split
3447  *
3448  * Before splitting this tries to make some room in the node by pushing
3449  * left and right, if either one works, it returns right away.
3450  *
3451  * returns 0 on success and < 0 on failure
3452  */
3453 static noinline int split_node(struct btrfs_trans_handle *trans,
3454                                struct btrfs_root *root,
3455                                struct btrfs_path *path, int level)
3456 {
3457         struct btrfs_fs_info *fs_info = root->fs_info;
3458         struct extent_buffer *c;
3459         struct extent_buffer *split;
3460         struct btrfs_disk_key disk_key;
3461         int mid;
3462         int ret;
3463         u32 c_nritems;
3464
3465         c = path->nodes[level];
3466         WARN_ON(btrfs_header_generation(c) != trans->transid);
3467         if (c == root->node) {
3468                 /*
3469                  * trying to split the root, lets make a new one
3470                  *
3471                  * tree mod log: We don't log_removal old root in
3472                  * insert_new_root, because that root buffer will be kept as a
3473                  * normal node. We are going to log removal of half of the
3474                  * elements below with tree_mod_log_eb_copy. We're holding a
3475                  * tree lock on the buffer, which is why we cannot race with
3476                  * other tree_mod_log users.
3477                  */
3478                 ret = insert_new_root(trans, root, path, level + 1);
3479                 if (ret)
3480                         return ret;
3481         } else {
3482                 ret = push_nodes_for_insert(trans, root, path, level);
3483                 c = path->nodes[level];
3484                 if (!ret && btrfs_header_nritems(c) <
3485                     BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 3)
3486                         return 0;
3487                 if (ret < 0)
3488                         return ret;
3489         }
3490
3491         c_nritems = btrfs_header_nritems(c);
3492         mid = (c_nritems + 1) / 2;
3493         btrfs_node_key(c, &disk_key, mid);
3494
3495         split = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
3496                         &disk_key, level, c->start, 0);
3497         if (IS_ERR(split))
3498                 return PTR_ERR(split);
3499
3500         root_add_used(root, fs_info->nodesize);
3501
3502         memzero_extent_buffer(split, 0, sizeof(struct btrfs_header));
3503         btrfs_set_header_level(split, btrfs_header_level(c));
3504         btrfs_set_header_bytenr(split, split->start);
3505         btrfs_set_header_generation(split, trans->transid);
3506         btrfs_set_header_backref_rev(split, BTRFS_MIXED_BACKREF_REV);
3507         btrfs_set_header_owner(split, root->root_key.objectid);
3508         write_extent_buffer_fsid(split, fs_info->fsid);
3509         write_extent_buffer_chunk_tree_uuid(split, fs_info->chunk_tree_uuid);
3510
3511         ret = tree_mod_log_eb_copy(fs_info, split, c, 0, mid, c_nritems - mid);
3512         if (ret) {
3513                 btrfs_abort_transaction(trans, ret);
3514                 return ret;
3515         }
3516         copy_extent_buffer(split, c,
3517                            btrfs_node_key_ptr_offset(0),
3518                            btrfs_node_key_ptr_offset(mid),
3519                            (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
3520         btrfs_set_header_nritems(split, c_nritems - mid);
3521         btrfs_set_header_nritems(c, mid);
3522         ret = 0;
3523
3524         btrfs_mark_buffer_dirty(c);
3525         btrfs_mark_buffer_dirty(split);
3526
3527         insert_ptr(trans, fs_info, path, &disk_key, split->start,
3528                    path->slots[level + 1] + 1, level + 1);
3529
3530         if (path->slots[level] >= mid) {
3531                 path->slots[level] -= mid;
3532                 btrfs_tree_unlock(c);
3533                 free_extent_buffer(c);
3534                 path->nodes[level] = split;
3535                 path->slots[level + 1] += 1;
3536         } else {
3537                 btrfs_tree_unlock(split);
3538                 free_extent_buffer(split);
3539         }
3540         return ret;
3541 }
3542
3543 /*
3544  * how many bytes are required to store the items in a leaf.  start
3545  * and nr indicate which items in the leaf to check.  This totals up the
3546  * space used both by the item structs and the item data
3547  */
3548 static int leaf_space_used(struct extent_buffer *l, int start, int nr)
3549 {
3550         struct btrfs_item *start_item;
3551         struct btrfs_item *end_item;
3552         struct btrfs_map_token token;
3553         int data_len;
3554         int nritems = btrfs_header_nritems(l);
3555         int end = min(nritems, start + nr) - 1;
3556
3557         if (!nr)
3558                 return 0;
3559         btrfs_init_map_token(&token);
3560         start_item = btrfs_item_nr(start);
3561         end_item = btrfs_item_nr(end);
3562         data_len = btrfs_token_item_offset(l, start_item, &token) +
3563                 btrfs_token_item_size(l, start_item, &token);
3564         data_len = data_len - btrfs_token_item_offset(l, end_item, &token);
3565         data_len += sizeof(struct btrfs_item) * nr;
3566         WARN_ON(data_len < 0);
3567         return data_len;
3568 }
3569
3570 /*
3571  * The space between the end of the leaf items and
3572  * the start of the leaf data.  IOW, how much room
3573  * the leaf has left for both items and data
3574  */
3575 noinline int btrfs_leaf_free_space(struct btrfs_fs_info *fs_info,
3576                                    struct extent_buffer *leaf)
3577 {
3578         int nritems = btrfs_header_nritems(leaf);
3579         int ret;
3580
3581         ret = BTRFS_LEAF_DATA_SIZE(fs_info) - leaf_space_used(leaf, 0, nritems);
3582         if (ret < 0) {
3583                 btrfs_crit(fs_info,
3584                            "leaf free space ret %d, leaf data size %lu, used %d nritems %d",
3585                            ret,
3586                            (unsigned long) BTRFS_LEAF_DATA_SIZE(fs_info),
3587                            leaf_space_used(leaf, 0, nritems), nritems);
3588         }
3589         return ret;
3590 }
3591
3592 /*
3593  * min slot controls the lowest index we're willing to push to the
3594  * right.  We'll push up to and including min_slot, but no lower
3595  */
3596 static noinline int __push_leaf_right(struct btrfs_fs_info *fs_info,
3597                                       struct btrfs_path *path,
3598                                       int data_size, int empty,
3599                                       struct extent_buffer *right,
3600                                       int free_space, u32 left_nritems,
3601                                       u32 min_slot)
3602 {
3603         struct extent_buffer *left = path->nodes[0];
3604         struct extent_buffer *upper = path->nodes[1];
3605         struct btrfs_map_token token;
3606         struct btrfs_disk_key disk_key;
3607         int slot;
3608         u32 i;
3609         int push_space = 0;
3610         int push_items = 0;
3611         struct btrfs_item *item;
3612         u32 nr;
3613         u32 right_nritems;
3614         u32 data_end;
3615         u32 this_item_size;
3616
3617         btrfs_init_map_token(&token);
3618
3619         if (empty)
3620                 nr = 0;
3621         else
3622                 nr = max_t(u32, 1, min_slot);
3623
3624         if (path->slots[0] >= left_nritems)
3625                 push_space += data_size;
3626
3627         slot = path->slots[1];
3628         i = left_nritems - 1;
3629         while (i >= nr) {
3630                 item = btrfs_item_nr(i);
3631
3632                 if (!empty && push_items > 0) {
3633                         if (path->slots[0] > i)
3634                                 break;
3635                         if (path->slots[0] == i) {
3636                                 int space = btrfs_leaf_free_space(fs_info, left);
3637                                 if (space + push_space * 2 > free_space)
3638                                         break;
3639                         }
3640                 }
3641
3642                 if (path->slots[0] == i)
3643                         push_space += data_size;
3644
3645                 this_item_size = btrfs_item_size(left, item);
3646                 if (this_item_size + sizeof(*item) + push_space > free_space)
3647                         break;
3648
3649                 push_items++;
3650                 push_space += this_item_size + sizeof(*item);
3651                 if (i == 0)
3652                         break;
3653                 i--;
3654         }
3655
3656         if (push_items == 0)
3657                 goto out_unlock;
3658
3659         WARN_ON(!empty && push_items == left_nritems);
3660
3661         /* push left to right */
3662         right_nritems = btrfs_header_nritems(right);
3663
3664         push_space = btrfs_item_end_nr(left, left_nritems - push_items);
3665         push_space -= leaf_data_end(fs_info, left);
3666
3667         /* make room in the right data area */
3668         data_end = leaf_data_end(fs_info, right);
3669         memmove_extent_buffer(right,
3670                               BTRFS_LEAF_DATA_OFFSET + data_end - push_space,
3671                               BTRFS_LEAF_DATA_OFFSET + data_end,
3672                               BTRFS_LEAF_DATA_SIZE(fs_info) - data_end);
3673
3674         /* copy from the left data area */
3675         copy_extent_buffer(right, left, BTRFS_LEAF_DATA_OFFSET +
3676                      BTRFS_LEAF_DATA_SIZE(fs_info) - push_space,
3677                      BTRFS_LEAF_DATA_OFFSET + leaf_data_end(fs_info, left),
3678                      push_space);
3679
3680         memmove_extent_buffer(right, btrfs_item_nr_offset(push_items),
3681                               btrfs_item_nr_offset(0),
3682                               right_nritems * sizeof(struct btrfs_item));
3683
3684         /* copy the items from left to right */
3685         copy_extent_buffer(right, left, btrfs_item_nr_offset(0),
3686                    btrfs_item_nr_offset(left_nritems - push_items),
3687                    push_items * sizeof(struct btrfs_item));
3688
3689         /* update the item pointers */
3690         right_nritems += push_items;
3691         btrfs_set_header_nritems(right, right_nritems);
3692         push_space = BTRFS_LEAF_DATA_SIZE(fs_info);
3693         for (i = 0; i < right_nritems; i++) {
3694                 item = btrfs_item_nr(i);
3695                 push_space -= btrfs_token_item_size(right, item, &token);
3696                 btrfs_set_token_item_offset(right, item, push_space, &token);
3697         }
3698
3699         left_nritems -= push_items;
3700         btrfs_set_header_nritems(left, left_nritems);
3701
3702         if (left_nritems)
3703                 btrfs_mark_buffer_dirty(left);
3704         else
3705                 clean_tree_block(fs_info, left);
3706
3707         btrfs_mark_buffer_dirty(right);
3708
3709         btrfs_item_key(right, &disk_key, 0);
3710         btrfs_set_node_key(upper, &disk_key, slot + 1);
3711         btrfs_mark_buffer_dirty(upper);
3712
3713         /* then fixup the leaf pointer in the path */
3714         if (path->slots[0] >= left_nritems) {
3715                 path->slots[0] -= left_nritems;
3716                 if (btrfs_header_nritems(path->nodes[0]) == 0)
3717                         clean_tree_block(fs_info, path->nodes[0]);
3718                 btrfs_tree_unlock(path->nodes[0]);
3719                 free_extent_buffer(path->nodes[0]);
3720                 path->nodes[0] = right;
3721                 path->slots[1] += 1;
3722         } else {
3723                 btrfs_tree_unlock(right);
3724                 free_extent_buffer(right);
3725         }
3726         return 0;
3727
3728 out_unlock:
3729         btrfs_tree_unlock(right);
3730         free_extent_buffer(right);
3731         return 1;
3732 }
3733
3734 /*
3735  * push some data in the path leaf to the right, trying to free up at
3736  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3737  *
3738  * returns 1 if the push failed because the other node didn't have enough
3739  * room, 0 if everything worked out and < 0 if there were major errors.
3740  *
3741  * this will push starting from min_slot to the end of the leaf.  It won't
3742  * push any slot lower than min_slot
3743  */
3744 static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
3745                            *root, struct btrfs_path *path,
3746                            int min_data_size, int data_size,
3747                            int empty, u32 min_slot)
3748 {
3749         struct btrfs_fs_info *fs_info = root->fs_info;
3750         struct extent_buffer *left = path->nodes[0];
3751         struct extent_buffer *right;
3752         struct extent_buffer *upper;
3753         int slot;
3754         int free_space;
3755         u32 left_nritems;
3756         int ret;
3757
3758         if (!path->nodes[1])
3759                 return 1;
3760
3761         slot = path->slots[1];
3762         upper = path->nodes[1];
3763         if (slot >= btrfs_header_nritems(upper) - 1)
3764                 return 1;
3765
3766         btrfs_assert_tree_locked(path->nodes[1]);
3767
3768         right = read_node_slot(fs_info, upper, slot + 1);
3769         /*
3770          * slot + 1 is not valid or we fail to read the right node,
3771          * no big deal, just return.
3772          */
3773         if (IS_ERR(right))
3774                 return 1;
3775
3776         btrfs_tree_lock(right);
3777         btrfs_set_lock_blocking(right);
3778
3779         free_space = btrfs_leaf_free_space(fs_info, right);
3780         if (free_space < data_size)
3781                 goto out_unlock;
3782
3783         /* cow and double check */
3784         ret = btrfs_cow_block(trans, root, right, upper,
3785                               slot + 1, &right);
3786         if (ret)
3787                 goto out_unlock;
3788
3789         free_space = btrfs_leaf_free_space(fs_info, right);
3790         if (free_space < data_size)
3791                 goto out_unlock;
3792
3793         left_nritems = btrfs_header_nritems(left);
3794         if (left_nritems == 0)
3795                 goto out_unlock;
3796
3797         if (path->slots[0] == left_nritems && !empty) {
3798                 /* Key greater than all keys in the leaf, right neighbor has
3799                  * enough room for it and we're not emptying our leaf to delete
3800                  * it, therefore use right neighbor to insert the new item and
3801                  * no need to touch/dirty our left leaft. */
3802                 btrfs_tree_unlock(left);
3803                 free_extent_buffer(left);
3804                 path->nodes[0] = right;
3805                 path->slots[0] = 0;
3806                 path->slots[1]++;
3807                 return 0;
3808         }
3809
3810         return __push_leaf_right(fs_info, path, min_data_size, empty,
3811                                 right, free_space, left_nritems, min_slot);
3812 out_unlock:
3813         btrfs_tree_unlock(right);
3814         free_extent_buffer(right);
3815         return 1;
3816 }
3817
3818 /*
3819  * push some data in the path leaf to the left, trying to free up at
3820  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3821  *
3822  * max_slot can put a limit on how far into the leaf we'll push items.  The
3823  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us do all the
3824  * items
3825  */
3826 static noinline int __push_leaf_left(struct btrfs_fs_info *fs_info,
3827                                      struct btrfs_path *path, int data_size,
3828                                      int empty, struct extent_buffer *left,
3829                                      int free_space, u32 right_nritems,
3830                                      u32 max_slot)
3831 {
3832         struct btrfs_disk_key disk_key;
3833         struct extent_buffer *right = path->nodes[0];
3834         int i;
3835         int push_space = 0;
3836         int push_items = 0;
3837         struct btrfs_item *item;
3838         u32 old_left_nritems;
3839         u32 nr;
3840         int ret = 0;
3841         u32 this_item_size;
3842         u32 old_left_item_size;
3843         struct btrfs_map_token token;
3844
3845         btrfs_init_map_token(&token);
3846
3847         if (empty)
3848                 nr = min(right_nritems, max_slot);
3849         else
3850                 nr = min(right_nritems - 1, max_slot);
3851
3852         for (i = 0; i < nr; i++) {
3853                 item = btrfs_item_nr(i);
3854
3855                 if (!empty && push_items > 0) {
3856                         if (path->slots[0] < i)
3857                                 break;
3858                         if (path->slots[0] == i) {
3859                                 int space = btrfs_leaf_free_space(fs_info, right);
3860                                 if (space + push_space * 2 > free_space)
3861                                         break;
3862                         }
3863                 }
3864
3865                 if (path->slots[0] == i)
3866                         push_space += data_size;
3867
3868                 this_item_size = btrfs_item_size(right, item);
3869                 if (this_item_size + sizeof(*item) + push_space > free_space)
3870                         break;
3871
3872                 push_items++;
3873                 push_space += this_item_size + sizeof(*item);
3874         }
3875
3876         if (push_items == 0) {
3877                 ret = 1;
3878                 goto out;
3879         }
3880         WARN_ON(!empty && push_items == btrfs_header_nritems(right));
3881
3882         /* push data from right to left */
3883         copy_extent_buffer(left, right,
3884                            btrfs_item_nr_offset(btrfs_header_nritems(left)),
3885                            btrfs_item_nr_offset(0),
3886                            push_items * sizeof(struct btrfs_item));
3887
3888         push_space = BTRFS_LEAF_DATA_SIZE(fs_info) -
3889                      btrfs_item_offset_nr(right, push_items - 1);
3890
3891         copy_extent_buffer(left, right, BTRFS_LEAF_DATA_OFFSET +
3892                      leaf_data_end(fs_info, left) - push_space,
3893                      BTRFS_LEAF_DATA_OFFSET +
3894                      btrfs_item_offset_nr(right, push_items - 1),
3895                      push_space);
3896         old_left_nritems = btrfs_header_nritems(left);
3897         BUG_ON(old_left_nritems <= 0);
3898
3899         old_left_item_size = btrfs_item_offset_nr(left, old_left_nritems - 1);
3900         for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
3901                 u32 ioff;
3902
3903                 item = btrfs_item_nr(i);
3904
3905                 ioff = btrfs_token_item_offset(left, item, &token);
3906                 btrfs_set_token_item_offset(left, item,
3907                       ioff - (BTRFS_LEAF_DATA_SIZE(fs_info) - old_left_item_size),
3908                       &token);
3909         }
3910         btrfs_set_header_nritems(left, old_left_nritems + push_items);
3911
3912         /* fixup right node */
3913         if (push_items > right_nritems)
3914                 WARN(1, KERN_CRIT "push items %d nr %u\n", push_items,
3915                        right_nritems);
3916
3917         if (push_items < right_nritems) {
3918                 push_space = btrfs_item_offset_nr(right, push_items - 1) -
3919                                                   leaf_data_end(fs_info, right);
3920                 memmove_extent_buffer(right, BTRFS_LEAF_DATA_OFFSET +
3921                                       BTRFS_LEAF_DATA_SIZE(fs_info) - push_space,
3922                                       BTRFS_LEAF_DATA_OFFSET +
3923                                       leaf_data_end(fs_info, right), push_space);
3924
3925                 memmove_extent_buffer(right, btrfs_item_nr_offset(0),
3926                               btrfs_item_nr_offset(push_items),
3927                              (btrfs_header_nritems(right) - push_items) *
3928                              sizeof(struct btrfs_item));
3929         }
3930         right_nritems -= push_items;
3931         btrfs_set_header_nritems(right, right_nritems);
3932         push_space = BTRFS_LEAF_DATA_SIZE(fs_info);
3933         for (i = 0; i < right_nritems; i++) {
3934                 item = btrfs_item_nr(i);
3935
3936                 push_space = push_space - btrfs_token_item_size(right,
3937                                                                 item, &token);
3938                 btrfs_set_token_item_offset(right, item, push_space, &token);
3939         }
3940
3941         btrfs_mark_buffer_dirty(left);
3942         if (right_nritems)
3943                 btrfs_mark_buffer_dirty(right);
3944         else
3945                 clean_tree_block(fs_info, right);
3946
3947         btrfs_item_key(right, &disk_key, 0);
3948         fixup_low_keys(fs_info, path, &disk_key, 1);
3949
3950         /* then fixup the leaf pointer in the path */
3951         if (path->slots[0] < push_items) {
3952                 path->slots[0] += old_left_nritems;
3953                 btrfs_tree_unlock(path->nodes[0]);
3954                 free_extent_buffer(path->nodes[0]);
3955                 path->nodes[0] = left;
3956                 path->slots[1] -= 1;
3957         } else {
3958                 btrfs_tree_unlock(left);
3959                 free_extent_buffer(left);
3960                 path->slots[0] -= push_items;
3961         }
3962         BUG_ON(path->slots[0] < 0);
3963         return ret;
3964 out:
3965         btrfs_tree_unlock(left);
3966         free_extent_buffer(left);
3967         return ret;
3968 }
3969
3970 /*
3971  * push some data in the path leaf to the left, trying to free up at
3972  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3973  *
3974  * max_slot can put a limit on how far into the leaf we'll push items.  The
3975  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us push all the
3976  * items
3977  */
3978 static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
3979                           *root, struct btrfs_path *path, int min_data_size,
3980                           int data_size, int empty, u32 max_slot)
3981 {
3982         struct btrfs_fs_info *fs_info = root->fs_info;
3983         struct extent_buffer *right = path->nodes[0];
3984         struct extent_buffer *left;
3985         int slot;
3986         int free_space;
3987         u32 right_nritems;
3988         int ret = 0;
3989
3990         slot = path->slots[1];
3991         if (slot == 0)
3992                 return 1;
3993         if (!path->nodes[1])
3994                 return 1;
3995
3996         right_nritems = btrfs_header_nritems(right);
3997         if (right_nritems == 0)
3998                 return 1;
3999
4000         btrfs_assert_tree_locked(path->nodes[1]);
4001
4002         left = read_node_slot(fs_info, path->nodes[1], slot - 1);
4003         /*
4004          * slot - 1 is not valid or we fail to read the left node,
4005          * no big deal, just return.
4006          */
4007         if (IS_ERR(left))
4008                 return 1;
4009
4010         btrfs_tree_lock(left);
4011         btrfs_set_lock_blocking(left);
4012
4013         free_space = btrfs_leaf_free_space(fs_info, left);
4014         if (free_space < data_size) {
4015                 ret = 1;
4016                 goto out;
4017         }
4018
4019         /* cow and double check */
4020         ret = btrfs_cow_block(trans, root, left,
4021                               path->nodes[1], slot - 1, &left);
4022         if (ret) {
4023                 /* we hit -ENOSPC, but it isn't fatal here */
4024                 if (ret == -ENOSPC)
4025                         ret = 1;
4026                 goto out;
4027         }
4028
4029         free_space = btrfs_leaf_free_space(fs_info, left);
4030         if (free_space < data_size) {
4031                 ret = 1;
4032                 goto out;
4033         }
4034
4035         return __push_leaf_left(fs_info, path, min_data_size,
4036                                empty, left, free_space, right_nritems,
4037                                max_slot);
4038 out:
4039         btrfs_tree_unlock(left);
4040         free_extent_buffer(left);
4041         return ret;
4042 }
4043
4044 /*
4045  * split the path's leaf in two, making sure there is at least data_size
4046  * available for the resulting leaf level of the path.
4047  */
4048 static noinline void copy_for_split(struct btrfs_trans_handle *trans,
4049                                     struct btrfs_fs_info *fs_info,
4050                                     struct btrfs_path *path,
4051                                     struct extent_buffer *l,
4052                                     struct extent_buffer *right,
4053                                     int slot, int mid, int nritems)
4054 {
4055         int data_copy_size;
4056         int rt_data_off;
4057         int i;
4058         struct btrfs_disk_key disk_key;
4059         struct btrfs_map_token token;
4060
4061         btrfs_init_map_token(&token);
4062
4063         nritems = nritems - mid;
4064         btrfs_set_header_nritems(right, nritems);
4065         data_copy_size = btrfs_item_end_nr(l, mid) - leaf_data_end(fs_info, l);
4066
4067         copy_extent_buffer(right, l, btrfs_item_nr_offset(0),
4068                            btrfs_item_nr_offset(mid),
4069                            nritems * sizeof(struct btrfs_item));
4070
4071         copy_extent_buffer(right, l,
4072                      BTRFS_LEAF_DATA_OFFSET + BTRFS_LEAF_DATA_SIZE(fs_info) -
4073                      data_copy_size, BTRFS_LEAF_DATA_OFFSET +
4074                      leaf_data_end(fs_info, l), data_copy_size);
4075
4076         rt_data_off = BTRFS_LEAF_DATA_SIZE(fs_info) - btrfs_item_end_nr(l, mid);
4077
4078         for (i = 0; i < nritems; i++) {
4079                 struct btrfs_item *item = btrfs_item_nr(i);
4080                 u32 ioff;
4081
4082                 ioff = btrfs_token_item_offset(right, item, &token);
4083                 btrfs_set_token_item_offset(right, item,
4084                                             ioff + rt_data_off, &token);
4085         }
4086
4087         btrfs_set_header_nritems(l, mid);
4088         btrfs_item_key(right, &disk_key, 0);
4089         insert_ptr(trans, fs_info, path, &disk_key, right->start,
4090                    path->slots[1] + 1, 1);
4091
4092         btrfs_mark_buffer_dirty(right);
4093         btrfs_mark_buffer_dirty(l);
4094         BUG_ON(path->slots[0] != slot);
4095
4096         if (mid <= slot) {
4097                 btrfs_tree_unlock(path->nodes[0]);
4098                 free_extent_buffer(path->nodes[0]);
4099                 path->nodes[0] = right;
4100                 path->slots[0] -= mid;
4101                 path->slots[1] += 1;
4102         } else {
4103                 btrfs_tree_unlock(right);
4104                 free_extent_buffer(right);
4105         }
4106
4107         BUG_ON(path->slots[0] < 0);
4108 }
4109
4110 /*
4111  * double splits happen when we need to insert a big item in the middle
4112  * of a leaf.  A double split can leave us with 3 mostly empty leaves:
4113  * leaf: [ slots 0 - N] [ our target ] [ N + 1 - total in leaf ]
4114  *          A                 B                 C
4115  *
4116  * We avoid this by trying to push the items on either side of our target
4117  * into the adjacent leaves.  If all goes well we can avoid the double split
4118  * completely.
4119  */
4120 static noinline int push_for_double_split(struct btrfs_trans_handle *trans,
4121                                           struct btrfs_root *root,
4122                                           struct btrfs_path *path,
4123                                           int data_size)
4124 {
4125         struct btrfs_fs_info *fs_info = root->fs_info;
4126         int ret;
4127         int progress = 0;
4128         int slot;
4129         u32 nritems;
4130         int space_needed = data_size;
4131
4132         slot = path->slots[0];
4133         if (slot < btrfs_header_nritems(path->nodes[0]))
4134                 space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
4135
4136         /*
4137          * try to push all the items after our slot into the
4138          * right leaf
4139          */
4140         ret = push_leaf_right(trans, root, path, 1, space_needed, 0, slot);
4141         if (ret < 0)
4142                 return ret;
4143
4144         if (ret == 0)
4145                 progress++;
4146
4147         nritems = btrfs_header_nritems(path->nodes[0]);
4148         /*
4149          * our goal is to get our slot at the start or end of a leaf.  If
4150          * we've done so we're done
4151          */
4152         if (path->slots[0] == 0 || path->slots[0] == nritems)
4153                 return 0;
4154
4155         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= data_size)
4156                 return 0;
4157
4158         /* try to push all the items before our slot into the next leaf */
4159         slot = path->slots[0];
4160         space_needed = data_size;
4161         if (slot > 0)
4162                 space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
4163         ret = push_leaf_left(trans, root, path, 1, space_needed, 0, slot);
4164         if (ret < 0)
4165                 return ret;
4166
4167         if (ret == 0)
4168                 progress++;
4169
4170         if (progress)
4171                 return 0;
4172         return 1;
4173 }
4174
4175 /*
4176  * split the path's leaf in two, making sure there is at least data_size
4177  * available for the resulting leaf level of the path.
4178  *
4179  * returns 0 if all went well and < 0 on failure.
4180  */
4181 static noinline int split_leaf(struct btrfs_trans_handle *trans,
4182                                struct btrfs_root *root,
4183                                const struct btrfs_key *ins_key,
4184                                struct btrfs_path *path, int data_size,
4185                                int extend)
4186 {
4187         struct btrfs_disk_key disk_key;
4188         struct extent_buffer *l;
4189         u32 nritems;
4190         int mid;
4191         int slot;
4192         struct extent_buffer *right;
4193         struct btrfs_fs_info *fs_info = root->fs_info;
4194         int ret = 0;
4195         int wret;
4196         int split;
4197         int num_doubles = 0;
4198         int tried_avoid_double = 0;
4199
4200         l = path->nodes[0];
4201         slot = path->slots[0];
4202         if (extend && data_size + btrfs_item_size_nr(l, slot) +
4203             sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(fs_info))
4204                 return -EOVERFLOW;
4205
4206         /* first try to make some room by pushing left and right */
4207         if (data_size && path->nodes[1]) {
4208                 int space_needed = data_size;
4209
4210                 if (slot < btrfs_header_nritems(l))
4211                         space_needed -= btrfs_leaf_free_space(fs_info, l);
4212
4213                 wret = push_leaf_right(trans, root, path, space_needed,
4214                                        space_needed, 0, 0);
4215                 if (wret < 0)
4216                         return wret;
4217                 if (wret) {
4218                         space_needed = data_size;
4219                         if (slot > 0)
4220                                 space_needed -= btrfs_leaf_free_space(fs_info,
4221                                                                       l);
4222                         wret = push_leaf_left(trans, root, path, space_needed,
4223                                               space_needed, 0, (u32)-1);
4224                         if (wret < 0)
4225                                 return wret;
4226                 }
4227                 l = path->nodes[0];
4228
4229                 /* did the pushes work? */
4230                 if (btrfs_leaf_free_space(fs_info, l) >= data_size)
4231                         return 0;
4232         }
4233
4234         if (!path->nodes[1]) {
4235                 ret = insert_new_root(trans, root, path, 1);
4236                 if (ret)
4237                         return ret;
4238         }
4239 again:
4240         split = 1;
4241         l = path->nodes[0];
4242         slot = path->slots[0];
4243         nritems = btrfs_header_nritems(l);
4244         mid = (nritems + 1) / 2;
4245
4246         if (mid <= slot) {
4247                 if (nritems == 1 ||
4248                     leaf_space_used(l, mid, nritems - mid) + data_size >
4249                         BTRFS_LEAF_DATA_SIZE(fs_info)) {
4250                         if (slot >= nritems) {
4251                                 split = 0;
4252                         } else {
4253                                 mid = slot;
4254                                 if (mid != nritems &&
4255                                     leaf_space_used(l, mid, nritems - mid) +
4256                                     data_size > BTRFS_LEAF_DATA_SIZE(fs_info)) {
4257                                         if (data_size && !tried_avoid_double)
4258                                                 goto push_for_double;
4259                                         split = 2;
4260                                 }
4261                         }
4262                 }
4263         } else {
4264                 if (leaf_space_used(l, 0, mid) + data_size >
4265                         BTRFS_LEAF_DATA_SIZE(fs_info)) {
4266                         if (!extend && data_size && slot == 0) {
4267                                 split = 0;
4268                         } else if ((extend || !data_size) && slot == 0) {
4269                                 mid = 1;
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         }
4282
4283         if (split == 0)
4284                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
4285         else
4286                 btrfs_item_key(l, &disk_key, mid);
4287
4288         right = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
4289                         &disk_key, 0, l->start, 0);
4290         if (IS_ERR(right))
4291                 return PTR_ERR(right);
4292
4293         root_add_used(root, fs_info->nodesize);
4294
4295         memzero_extent_buffer(right, 0, sizeof(struct btrfs_header));
4296         btrfs_set_header_bytenr(right, right->start);
4297         btrfs_set_header_generation(right, trans->transid);
4298         btrfs_set_header_backref_rev(right, BTRFS_MIXED_BACKREF_REV);
4299         btrfs_set_header_owner(right, root->root_key.objectid);
4300         btrfs_set_header_level(right, 0);
4301         write_extent_buffer_fsid(right, fs_info->fsid);
4302         write_extent_buffer_chunk_tree_uuid(right, fs_info->chunk_tree_uuid);
4303
4304         if (split == 0) {
4305                 if (mid <= slot) {
4306                         btrfs_set_header_nritems(right, 0);
4307                         insert_ptr(trans, fs_info, path, &disk_key,
4308                                    right->start, path->slots[1] + 1, 1);
4309                         btrfs_tree_unlock(path->nodes[0]);
4310                         free_extent_buffer(path->nodes[0]);
4311                         path->nodes[0] = right;
4312                         path->slots[0] = 0;
4313                         path->slots[1] += 1;
4314                 } else {
4315                         btrfs_set_header_nritems(right, 0);
4316                         insert_ptr(trans, fs_info, path, &disk_key,
4317                                    right->start, path->slots[1], 1);
4318                         btrfs_tree_unlock(path->nodes[0]);
4319                         free_extent_buffer(path->nodes[0]);
4320                         path->nodes[0] = right;
4321                         path->slots[0] = 0;
4322                         if (path->slots[1] == 0)
4323                                 fixup_low_keys(fs_info, path, &disk_key, 1);
4324                 }
4325                 /*
4326                  * We create a new leaf 'right' for the required ins_len and
4327                  * we'll do btrfs_mark_buffer_dirty() on this leaf after copying
4328                  * the content of ins_len to 'right'.
4329                  */
4330                 return ret;
4331         }
4332
4333         copy_for_split(trans, fs_info, path, l, right, slot, mid, nritems);
4334
4335         if (split == 2) {
4336                 BUG_ON(num_doubles != 0);
4337                 num_doubles++;
4338                 goto again;
4339         }
4340
4341         return 0;
4342
4343 push_for_double:
4344         push_for_double_split(trans, root, path, data_size);
4345         tried_avoid_double = 1;
4346         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= data_size)
4347                 return 0;
4348         goto again;
4349 }
4350
4351 static noinline int setup_leaf_for_split(struct btrfs_trans_handle *trans,
4352                                          struct btrfs_root *root,
4353                                          struct btrfs_path *path, int ins_len)
4354 {
4355         struct btrfs_fs_info *fs_info = root->fs_info;
4356         struct btrfs_key key;
4357         struct extent_buffer *leaf;
4358         struct btrfs_file_extent_item *fi;
4359         u64 extent_len = 0;
4360         u32 item_size;
4361         int ret;
4362
4363         leaf = path->nodes[0];
4364         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4365
4366         BUG_ON(key.type != BTRFS_EXTENT_DATA_KEY &&
4367                key.type != BTRFS_EXTENT_CSUM_KEY);
4368
4369         if (btrfs_leaf_free_space(fs_info, leaf) >= ins_len)
4370                 return 0;
4371
4372         item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4373         if (key.type == BTRFS_EXTENT_DATA_KEY) {
4374                 fi = btrfs_item_ptr(leaf, path->slots[0],
4375                                     struct btrfs_file_extent_item);
4376                 extent_len = btrfs_file_extent_num_bytes(leaf, fi);
4377         }
4378         btrfs_release_path(path);
4379
4380         path->keep_locks = 1;
4381         path->search_for_split = 1;
4382         ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
4383         path->search_for_split = 0;
4384         if (ret > 0)
4385                 ret = -EAGAIN;
4386         if (ret < 0)
4387                 goto err;
4388
4389         ret = -EAGAIN;
4390         leaf = path->nodes[0];
4391         /* if our item isn't there, return now */
4392         if (item_size != btrfs_item_size_nr(leaf, path->slots[0]))
4393                 goto err;
4394
4395         /* the leaf has  changed, it now has room.  return now */
4396         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= ins_len)
4397                 goto err;
4398
4399         if (key.type == BTRFS_EXTENT_DATA_KEY) {
4400                 fi = btrfs_item_ptr(leaf, path->slots[0],
4401                                     struct btrfs_file_extent_item);
4402                 if (extent_len != btrfs_file_extent_num_bytes(leaf, fi))
4403                         goto err;
4404         }
4405
4406         btrfs_set_path_blocking(path);
4407         ret = split_leaf(trans, root, &key, path, ins_len, 1);
4408         if (ret)
4409                 goto err;
4410
4411         path->keep_locks = 0;
4412         btrfs_unlock_up_safe(path, 1);
4413         return 0;
4414 err:
4415         path->keep_locks = 0;
4416         return ret;
4417 }
4418
4419 static noinline int split_item(struct btrfs_fs_info *fs_info,
4420                                struct btrfs_path *path,
4421                                const struct btrfs_key *new_key,
4422                                unsigned long split_offset)
4423 {
4424         struct extent_buffer *leaf;
4425         struct btrfs_item *item;
4426         struct btrfs_item *new_item;
4427         int slot;
4428         char *buf;
4429         u32 nritems;
4430         u32 item_size;
4431         u32 orig_offset;
4432         struct btrfs_disk_key disk_key;
4433
4434         leaf = path->nodes[0];
4435         BUG_ON(btrfs_leaf_free_space(fs_info, leaf) < sizeof(struct btrfs_item));
4436
4437         btrfs_set_path_blocking(path);
4438
4439         item = btrfs_item_nr(path->slots[0]);
4440         orig_offset = btrfs_item_offset(leaf, item);
4441         item_size = btrfs_item_size(leaf, item);
4442
4443         buf = kmalloc(item_size, GFP_NOFS);
4444         if (!buf)
4445                 return -ENOMEM;
4446
4447         read_extent_buffer(leaf, buf, btrfs_item_ptr_offset(leaf,
4448                             path->slots[0]), item_size);
4449
4450         slot = path->slots[0] + 1;
4451         nritems = btrfs_header_nritems(leaf);
4452         if (slot != nritems) {
4453                 /* shift the items */
4454                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + 1),
4455                                 btrfs_item_nr_offset(slot),
4456                                 (nritems - slot) * sizeof(struct btrfs_item));
4457         }
4458
4459         btrfs_cpu_key_to_disk(&disk_key, new_key);
4460         btrfs_set_item_key(leaf, &disk_key, slot);
4461
4462         new_item = btrfs_item_nr(slot);
4463
4464         btrfs_set_item_offset(leaf, new_item, orig_offset);
4465         btrfs_set_item_size(leaf, new_item, item_size - split_offset);
4466
4467         btrfs_set_item_offset(leaf, item,
4468                               orig_offset + item_size - split_offset);
4469         btrfs_set_item_size(leaf, item, split_offset);
4470
4471         btrfs_set_header_nritems(leaf, nritems + 1);
4472
4473         /* write the data for the start of the original item */
4474         write_extent_buffer(leaf, buf,
4475                             btrfs_item_ptr_offset(leaf, path->slots[0]),
4476                             split_offset);
4477
4478         /* write the data for the new item */
4479         write_extent_buffer(leaf, buf + split_offset,
4480                             btrfs_item_ptr_offset(leaf, slot),
4481                             item_size - split_offset);
4482         btrfs_mark_buffer_dirty(leaf);
4483
4484         BUG_ON(btrfs_leaf_free_space(fs_info, leaf) < 0);
4485         kfree(buf);
4486         return 0;
4487 }
4488
4489 /*
4490  * This function splits a single item into two items,
4491  * giving 'new_key' to the new item and splitting the
4492  * old one at split_offset (from the start of the item).
4493  *
4494  * The path may be released by this operation.  After
4495  * the split, the path is pointing to the old item.  The
4496  * new item is going to be in the same node as the old one.
4497  *
4498  * Note, the item being split must be smaller enough to live alone on
4499  * a tree block with room for one extra struct btrfs_item
4500  *
4501  * This allows us to split the item in place, keeping a lock on the
4502  * leaf the entire time.
4503  */
4504 int btrfs_split_item(struct btrfs_trans_handle *trans,
4505                      struct btrfs_root *root,
4506                      struct btrfs_path *path,
4507                      const struct btrfs_key *new_key,
4508                      unsigned long split_offset)
4509 {
4510         int ret;
4511         ret = setup_leaf_for_split(trans, root, path,
4512                                    sizeof(struct btrfs_item));
4513         if (ret)
4514                 return ret;
4515
4516         ret = split_item(root->fs_info, path, new_key, split_offset);
4517         return ret;
4518 }
4519
4520 /*
4521  * This function duplicate a item, giving 'new_key' to the new item.
4522  * It guarantees both items live in the same tree leaf and the new item
4523  * is contiguous with the original item.
4524  *
4525  * This allows us to split file extent in place, keeping a lock on the
4526  * leaf the entire time.
4527  */
4528 int btrfs_duplicate_item(struct btrfs_trans_handle *trans,
4529                          struct btrfs_root *root,
4530                          struct btrfs_path *path,
4531                          const struct btrfs_key *new_key)
4532 {
4533         struct extent_buffer *leaf;
4534         int ret;
4535         u32 item_size;
4536
4537         leaf = path->nodes[0];
4538         item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4539         ret = setup_leaf_for_split(trans, root, path,
4540                                    item_size + sizeof(struct btrfs_item));
4541         if (ret)
4542                 return ret;
4543
4544         path->slots[0]++;
4545         setup_items_for_insert(root, path, new_key, &item_size,
4546                                item_size, item_size +
4547                                sizeof(struct btrfs_item), 1);
4548         leaf = path->nodes[0];
4549         memcpy_extent_buffer(leaf,
4550                              btrfs_item_ptr_offset(leaf, path->slots[0]),
4551                              btrfs_item_ptr_offset(leaf, path->slots[0] - 1),
4552                              item_size);
4553         return 0;
4554 }
4555
4556 /*
4557  * make the item pointed to by the path smaller.  new_size indicates
4558  * how small to make it, and from_end tells us if we just chop bytes
4559  * off the end of the item or if we shift the item to chop bytes off
4560  * the front.
4561  */
4562 void btrfs_truncate_item(struct btrfs_fs_info *fs_info,
4563                          struct btrfs_path *path, u32 new_size, int from_end)
4564 {
4565         int slot;
4566         struct extent_buffer *leaf;
4567         struct btrfs_item *item;
4568         u32 nritems;
4569         unsigned int data_end;
4570         unsigned int old_data_start;
4571         unsigned int old_size;
4572         unsigned int size_diff;
4573         int i;
4574         struct btrfs_map_token token;
4575
4576         btrfs_init_map_token(&token);
4577
4578         leaf = path->nodes[0];
4579         slot = path->slots[0];
4580
4581         old_size = btrfs_item_size_nr(leaf, slot);
4582         if (old_size == new_size)
4583                 return;
4584
4585         nritems = btrfs_header_nritems(leaf);
4586         data_end = leaf_data_end(fs_info, leaf);
4587
4588         old_data_start = btrfs_item_offset_nr(leaf, slot);
4589
4590         size_diff = old_size - new_size;
4591
4592         BUG_ON(slot < 0);
4593         BUG_ON(slot >= nritems);
4594
4595         /*
4596          * item0..itemN ... dataN.offset..dataN.size .. data0.size
4597          */
4598         /* first correct the data pointers */
4599         for (i = slot; i < nritems; i++) {
4600                 u32 ioff;
4601                 item = btrfs_item_nr(i);
4602
4603                 ioff = btrfs_token_item_offset(leaf, item, &token);
4604                 btrfs_set_token_item_offset(leaf, item,
4605                                             ioff + size_diff, &token);
4606         }
4607
4608         /* shift the data */
4609         if (from_end) {
4610                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4611                               data_end + size_diff, BTRFS_LEAF_DATA_OFFSET +
4612                               data_end, old_data_start + new_size - data_end);
4613         } else {
4614                 struct btrfs_disk_key disk_key;
4615                 u64 offset;
4616
4617                 btrfs_item_key(leaf, &disk_key, slot);
4618
4619                 if (btrfs_disk_key_type(&disk_key) == BTRFS_EXTENT_DATA_KEY) {
4620                         unsigned long ptr;
4621                         struct btrfs_file_extent_item *fi;
4622
4623                         fi = btrfs_item_ptr(leaf, slot,
4624                                             struct btrfs_file_extent_item);
4625                         fi = (struct btrfs_file_extent_item *)(
4626                              (unsigned long)fi - size_diff);
4627
4628                         if (btrfs_file_extent_type(leaf, fi) ==
4629                             BTRFS_FILE_EXTENT_INLINE) {
4630                                 ptr = btrfs_item_ptr_offset(leaf, slot);
4631                                 memmove_extent_buffer(leaf, ptr,
4632                                       (unsigned long)fi,
4633                                       BTRFS_FILE_EXTENT_INLINE_DATA_START);
4634                         }
4635                 }
4636
4637                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4638                               data_end + size_diff, BTRFS_LEAF_DATA_OFFSET +
4639                               data_end, old_data_start - data_end);
4640
4641                 offset = btrfs_disk_key_offset(&disk_key);
4642                 btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
4643                 btrfs_set_item_key(leaf, &disk_key, slot);
4644                 if (slot == 0)
4645                         fixup_low_keys(fs_info, path, &disk_key, 1);
4646         }
4647
4648         item = btrfs_item_nr(slot);
4649         btrfs_set_item_size(leaf, item, new_size);
4650         btrfs_mark_buffer_dirty(leaf);
4651
4652         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4653                 btrfs_print_leaf(leaf);
4654                 BUG();
4655         }
4656 }
4657
4658 /*
4659  * make the item pointed to by the path bigger, data_size is the added size.
4660  */
4661 void btrfs_extend_item(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
4662                        u32 data_size)
4663 {
4664         int slot;
4665         struct extent_buffer *leaf;
4666         struct btrfs_item *item;
4667         u32 nritems;
4668         unsigned int data_end;
4669         unsigned int old_data;
4670         unsigned int old_size;
4671         int i;
4672         struct btrfs_map_token token;
4673
4674         btrfs_init_map_token(&token);
4675
4676         leaf = path->nodes[0];
4677
4678         nritems = btrfs_header_nritems(leaf);
4679         data_end = leaf_data_end(fs_info, leaf);
4680
4681         if (btrfs_leaf_free_space(fs_info, leaf) < data_size) {
4682                 btrfs_print_leaf(leaf);
4683                 BUG();
4684         }
4685         slot = path->slots[0];
4686         old_data = btrfs_item_end_nr(leaf, slot);
4687
4688         BUG_ON(slot < 0);
4689         if (slot >= nritems) {
4690                 btrfs_print_leaf(leaf);
4691                 btrfs_crit(fs_info, "slot %d too large, nritems %d",
4692                            slot, nritems);
4693                 BUG_ON(1);
4694         }
4695
4696         /*
4697          * item0..itemN ... dataN.offset..dataN.size .. data0.size
4698          */
4699         /* first correct the data pointers */
4700         for (i = slot; i < nritems; i++) {
4701                 u32 ioff;
4702                 item = btrfs_item_nr(i);
4703
4704                 ioff = btrfs_token_item_offset(leaf, item, &token);
4705                 btrfs_set_token_item_offset(leaf, item,
4706                                             ioff - data_size, &token);
4707         }
4708
4709         /* shift the data */
4710         memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4711                       data_end - data_size, BTRFS_LEAF_DATA_OFFSET +
4712                       data_end, old_data - data_end);
4713
4714         data_end = old_data;
4715         old_size = btrfs_item_size_nr(leaf, slot);
4716         item = btrfs_item_nr(slot);
4717         btrfs_set_item_size(leaf, item, old_size + data_size);
4718         btrfs_mark_buffer_dirty(leaf);
4719
4720         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4721                 btrfs_print_leaf(leaf);
4722                 BUG();
4723         }
4724 }
4725
4726 /*
4727  * this is a helper for btrfs_insert_empty_items, the main goal here is
4728  * to save stack depth by doing the bulk of the work in a function
4729  * that doesn't call btrfs_search_slot
4730  */
4731 void setup_items_for_insert(struct btrfs_root *root, struct btrfs_path *path,
4732                             const struct btrfs_key *cpu_key, u32 *data_size,
4733                             u32 total_data, u32 total_size, int nr)
4734 {
4735         struct btrfs_fs_info *fs_info = root->fs_info;
4736         struct btrfs_item *item;
4737         int i;
4738         u32 nritems;
4739         unsigned int data_end;
4740         struct btrfs_disk_key disk_key;
4741         struct extent_buffer *leaf;
4742         int slot;
4743         struct btrfs_map_token token;
4744
4745         if (path->slots[0] == 0) {
4746                 btrfs_cpu_key_to_disk(&disk_key, cpu_key);
4747                 fixup_low_keys(fs_info, path, &disk_key, 1);
4748         }
4749         btrfs_unlock_up_safe(path, 1);
4750
4751         btrfs_init_map_token(&token);
4752
4753         leaf = path->nodes[0];
4754         slot = path->slots[0];
4755
4756         nritems = btrfs_header_nritems(leaf);
4757         data_end = leaf_data_end(fs_info, leaf);
4758
4759         if (btrfs_leaf_free_space(fs_info, leaf) < total_size) {
4760                 btrfs_print_leaf(leaf);
4761                 btrfs_crit(fs_info, "not enough freespace need %u have %d",
4762                            total_size, btrfs_leaf_free_space(fs_info, leaf));
4763                 BUG();
4764         }
4765
4766         if (slot != nritems) {
4767                 unsigned int old_data = btrfs_item_end_nr(leaf, slot);
4768
4769                 if (old_data < data_end) {
4770                         btrfs_print_leaf(leaf);
4771                         btrfs_crit(fs_info, "slot %d old_data %d data_end %d",
4772                                    slot, old_data, data_end);
4773                         BUG_ON(1);
4774                 }
4775                 /*
4776                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
4777                  */
4778                 /* first correct the data pointers */
4779                 for (i = slot; i < nritems; i++) {
4780                         u32 ioff;
4781
4782                         item = btrfs_item_nr(i);
4783                         ioff = btrfs_token_item_offset(leaf, item, &token);
4784                         btrfs_set_token_item_offset(leaf, item,
4785                                                     ioff - total_data, &token);
4786                 }
4787                 /* shift the items */
4788                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + nr),
4789                               btrfs_item_nr_offset(slot),
4790                               (nritems - slot) * sizeof(struct btrfs_item));
4791
4792                 /* shift the data */
4793                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4794                               data_end - total_data, BTRFS_LEAF_DATA_OFFSET +
4795                               data_end, old_data - data_end);
4796                 data_end = old_data;
4797         }
4798
4799         /* setup the item for the new data */
4800         for (i = 0; i < nr; i++) {
4801                 btrfs_cpu_key_to_disk(&disk_key, cpu_key + i);
4802                 btrfs_set_item_key(leaf, &disk_key, slot + i);
4803                 item = btrfs_item_nr(slot + i);
4804                 btrfs_set_token_item_offset(leaf, item,
4805                                             data_end - data_size[i], &token);
4806                 data_end -= data_size[i];
4807                 btrfs_set_token_item_size(leaf, item, data_size[i], &token);
4808         }
4809
4810         btrfs_set_header_nritems(leaf, nritems + nr);
4811         btrfs_mark_buffer_dirty(leaf);
4812
4813         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4814                 btrfs_print_leaf(leaf);
4815                 BUG();
4816         }
4817 }
4818
4819 /*
4820  * Given a key and some data, insert items into the tree.
4821  * This does all the path init required, making room in the tree if needed.
4822  */
4823 int btrfs_insert_empty_items(struct btrfs_trans_handle *trans,
4824                             struct btrfs_root *root,
4825                             struct btrfs_path *path,
4826                             const struct btrfs_key *cpu_key, u32 *data_size,
4827                             int nr)
4828 {
4829         int ret = 0;
4830         int slot;
4831         int i;
4832         u32 total_size = 0;
4833         u32 total_data = 0;
4834
4835         for (i = 0; i < nr; i++)
4836                 total_data += data_size[i];
4837
4838         total_size = total_data + (nr * sizeof(struct btrfs_item));
4839         ret = btrfs_search_slot(trans, root, cpu_key, path, total_size, 1);
4840         if (ret == 0)
4841                 return -EEXIST;
4842         if (ret < 0)
4843                 return ret;
4844
4845         slot = path->slots[0];
4846         BUG_ON(slot < 0);
4847
4848         setup_items_for_insert(root, path, cpu_key, data_size,
4849                                total_data, total_size, nr);
4850         return 0;
4851 }
4852
4853 /*
4854  * Given a key and some data, insert an item into the tree.
4855  * This does all the path init required, making room in the tree if needed.
4856  */
4857 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4858                       const struct btrfs_key *cpu_key, void *data,
4859                       u32 data_size)
4860 {
4861         int ret = 0;
4862         struct btrfs_path *path;
4863         struct extent_buffer *leaf;
4864         unsigned long ptr;
4865
4866         path = btrfs_alloc_path();
4867         if (!path)
4868                 return -ENOMEM;
4869         ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
4870         if (!ret) {
4871                 leaf = path->nodes[0];
4872                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
4873                 write_extent_buffer(leaf, data, ptr, data_size);
4874                 btrfs_mark_buffer_dirty(leaf);
4875         }
4876         btrfs_free_path(path);
4877         return ret;
4878 }
4879
4880 /*
4881  * delete the pointer from a given node.
4882  *
4883  * the tree should have been previously balanced so the deletion does not
4884  * empty a node.
4885  */
4886 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
4887                     int level, int slot)
4888 {
4889         struct btrfs_fs_info *fs_info = root->fs_info;
4890         struct extent_buffer *parent = path->nodes[level];
4891         u32 nritems;
4892         int ret;
4893
4894         nritems = btrfs_header_nritems(parent);
4895         if (slot != nritems - 1) {
4896                 if (level)
4897                         tree_mod_log_eb_move(fs_info, parent, slot,
4898                                              slot + 1, nritems - slot - 1);
4899                 memmove_extent_buffer(parent,
4900                               btrfs_node_key_ptr_offset(slot),
4901                               btrfs_node_key_ptr_offset(slot + 1),
4902                               sizeof(struct btrfs_key_ptr) *
4903                               (nritems - slot - 1));
4904         } else if (level) {
4905                 ret = tree_mod_log_insert_key(fs_info, parent, slot,
4906                                               MOD_LOG_KEY_REMOVE, GFP_NOFS);
4907                 BUG_ON(ret < 0);
4908         }
4909
4910         nritems--;
4911         btrfs_set_header_nritems(parent, nritems);
4912         if (nritems == 0 && parent == root->node) {
4913                 BUG_ON(btrfs_header_level(root->node) != 1);
4914                 /* just turn the root into a leaf and break */
4915                 btrfs_set_header_level(root->node, 0);
4916         } else if (slot == 0) {
4917                 struct btrfs_disk_key disk_key;
4918
4919                 btrfs_node_key(parent, &disk_key, 0);
4920                 fixup_low_keys(fs_info, path, &disk_key, level + 1);
4921         }
4922         btrfs_mark_buffer_dirty(parent);
4923 }
4924
4925 /*
4926  * a helper function to delete the leaf pointed to by path->slots[1] and
4927  * path->nodes[1].
4928  *
4929  * This deletes the pointer in path->nodes[1] and frees the leaf
4930  * block extent.  zero is returned if it all worked out, < 0 otherwise.
4931  *
4932  * The path must have already been setup for deleting the leaf, including
4933  * all the proper balancing.  path->nodes[1] must be locked.
4934  */
4935 static noinline void btrfs_del_leaf(struct btrfs_trans_handle *trans,
4936                                     struct btrfs_root *root,
4937                                     struct btrfs_path *path,
4938                                     struct extent_buffer *leaf)
4939 {
4940         WARN_ON(btrfs_header_generation(leaf) != trans->transid);
4941         del_ptr(root, path, 1, path->slots[1]);
4942
4943         /*
4944          * btrfs_free_extent is expensive, we want to make sure we
4945          * aren't holding any locks when we call it
4946          */
4947         btrfs_unlock_up_safe(path, 0);
4948
4949         root_sub_used(root, leaf->len);
4950
4951         extent_buffer_get(leaf);
4952         btrfs_free_tree_block(trans, root, leaf, 0, 1);
4953         free_extent_buffer_stale(leaf);
4954 }
4955 /*
4956  * delete the item at the leaf level in path.  If that empties
4957  * the leaf, remove it from the tree
4958  */
4959 int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4960                     struct btrfs_path *path, int slot, int nr)
4961 {
4962         struct btrfs_fs_info *fs_info = root->fs_info;
4963         struct extent_buffer *leaf;
4964         struct btrfs_item *item;
4965         u32 last_off;
4966         u32 dsize = 0;
4967         int ret = 0;
4968         int wret;
4969         int i;
4970         u32 nritems;
4971         struct btrfs_map_token token;
4972
4973         btrfs_init_map_token(&token);
4974
4975         leaf = path->nodes[0];
4976         last_off = btrfs_item_offset_nr(leaf, slot + nr - 1);
4977
4978         for (i = 0; i < nr; i++)
4979                 dsize += btrfs_item_size_nr(leaf, slot + i);
4980
4981         nritems = btrfs_header_nritems(leaf);
4982
4983         if (slot + nr != nritems) {
4984                 int data_end = leaf_data_end(fs_info, leaf);
4985
4986                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4987                               data_end + dsize,
4988                               BTRFS_LEAF_DATA_OFFSET + data_end,
4989                               last_off - data_end);
4990
4991                 for (i = slot + nr; i < nritems; i++) {
4992                         u32 ioff;
4993
4994                         item = btrfs_item_nr(i);
4995                         ioff = btrfs_token_item_offset(leaf, item, &token);
4996                         btrfs_set_token_item_offset(leaf, item,
4997                                                     ioff + dsize, &token);
4998                 }
4999
5000                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot),
5001                               btrfs_item_nr_offset(slot + nr),
5002                               sizeof(struct btrfs_item) *
5003                               (nritems - slot - nr));
5004         }
5005         btrfs_set_header_nritems(leaf, nritems - nr);
5006         nritems -= nr;
5007
5008         /* delete the leaf if we've emptied it */
5009         if (nritems == 0) {
5010                 if (leaf == root->node) {
5011                         btrfs_set_header_level(leaf, 0);
5012                 } else {
5013                         btrfs_set_path_blocking(path);
5014                         clean_tree_block(fs_info, leaf);
5015                         btrfs_del_leaf(trans, root, path, leaf);
5016                 }
5017         } else {
5018                 int used = leaf_space_used(leaf, 0, nritems);
5019                 if (slot == 0) {
5020                         struct btrfs_disk_key disk_key;
5021
5022                         btrfs_item_key(leaf, &disk_key, 0);
5023                         fixup_low_keys(fs_info, path, &disk_key, 1);
5024                 }
5025
5026                 /* delete the leaf if it is mostly empty */
5027                 if (used < BTRFS_LEAF_DATA_SIZE(fs_info) / 3) {
5028                         /* push_leaf_left fixes the path.
5029                          * make sure the path still points to our leaf
5030                          * for possible call to del_ptr below
5031                          */
5032                         slot = path->slots[1];
5033                         extent_buffer_get(leaf);
5034
5035                         btrfs_set_path_blocking(path);
5036                         wret = push_leaf_left(trans, root, path, 1, 1,
5037                                               1, (u32)-1);
5038                         if (wret < 0 && wret != -ENOSPC)
5039                                 ret = wret;
5040
5041                         if (path->nodes[0] == leaf &&
5042                             btrfs_header_nritems(leaf)) {
5043                                 wret = push_leaf_right(trans, root, path, 1,
5044                                                        1, 1, 0);
5045                                 if (wret < 0 && wret != -ENOSPC)
5046                                         ret = wret;
5047                         }
5048
5049                         if (btrfs_header_nritems(leaf) == 0) {
5050                                 path->slots[1] = slot;
5051                                 btrfs_del_leaf(trans, root, path, leaf);
5052                                 free_extent_buffer(leaf);
5053                                 ret = 0;
5054                         } else {
5055                                 /* if we're still in the path, make sure
5056                                  * we're dirty.  Otherwise, one of the
5057                                  * push_leaf functions must have already
5058                                  * dirtied this buffer
5059                                  */
5060                                 if (path->nodes[0] == leaf)
5061                                         btrfs_mark_buffer_dirty(leaf);
5062                                 free_extent_buffer(leaf);
5063                         }
5064                 } else {
5065                         btrfs_mark_buffer_dirty(leaf);
5066                 }
5067         }
5068         return ret;
5069 }
5070
5071 /*
5072  * search the tree again to find a leaf with lesser keys
5073  * returns 0 if it found something or 1 if there are no lesser leaves.
5074  * returns < 0 on io errors.
5075  *
5076  * This may release the path, and so you may lose any locks held at the
5077  * time you call it.
5078  */
5079 int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
5080 {
5081         struct btrfs_key key;
5082         struct btrfs_disk_key found_key;
5083         int ret;
5084
5085         btrfs_item_key_to_cpu(path->nodes[0], &key, 0);
5086
5087         if (key.offset > 0) {
5088                 key.offset--;
5089         } else if (key.type > 0) {
5090                 key.type--;
5091                 key.offset = (u64)-1;
5092         } else if (key.objectid > 0) {
5093                 key.objectid--;
5094                 key.type = (u8)-1;
5095                 key.offset = (u64)-1;
5096         } else {
5097                 return 1;
5098         }
5099
5100         btrfs_release_path(path);
5101         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5102         if (ret < 0)
5103                 return ret;
5104         btrfs_item_key(path->nodes[0], &found_key, 0);
5105         ret = comp_keys(&found_key, &key);
5106         /*
5107          * We might have had an item with the previous key in the tree right
5108          * before we released our path. And after we released our path, that
5109          * item might have been pushed to the first slot (0) of the leaf we
5110          * were holding due to a tree balance. Alternatively, an item with the
5111          * previous key can exist as the only element of a leaf (big fat item).
5112          * Therefore account for these 2 cases, so that our callers (like
5113          * btrfs_previous_item) don't miss an existing item with a key matching
5114          * the previous key we computed above.
5115          */
5116         if (ret <= 0)
5117                 return 0;
5118         return 1;
5119 }
5120
5121 /*
5122  * A helper function to walk down the tree starting at min_key, and looking
5123  * for nodes or leaves that are have a minimum transaction id.
5124  * This is used by the btree defrag code, and tree logging
5125  *
5126  * This does not cow, but it does stuff the starting key it finds back
5127  * into min_key, so you can call btrfs_search_slot with cow=1 on the
5128  * key and get a writable path.
5129  *
5130  * This does lock as it descends, and path->keep_locks should be set
5131  * to 1 by the caller.
5132  *
5133  * This honors path->lowest_level to prevent descent past a given level
5134  * of the tree.
5135  *
5136  * min_trans indicates the oldest transaction that you are interested
5137  * in walking through.  Any nodes or leaves older than min_trans are
5138  * skipped over (without reading them).
5139  *
5140  * returns zero if something useful was found, < 0 on error and 1 if there
5141  * was nothing in the tree that matched the search criteria.
5142  */
5143 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
5144                          struct btrfs_path *path,
5145                          u64 min_trans)
5146 {
5147         struct btrfs_fs_info *fs_info = root->fs_info;
5148         struct extent_buffer *cur;
5149         struct btrfs_key found_key;
5150         int slot;
5151         int sret;
5152         u32 nritems;
5153         int level;
5154         int ret = 1;
5155         int keep_locks = path->keep_locks;
5156
5157         path->keep_locks = 1;
5158 again:
5159         cur = btrfs_read_lock_root_node(root);
5160         level = btrfs_header_level(cur);
5161         WARN_ON(path->nodes[level]);
5162         path->nodes[level] = cur;
5163         path->locks[level] = BTRFS_READ_LOCK;
5164
5165         if (btrfs_header_generation(cur) < min_trans) {
5166                 ret = 1;
5167                 goto out;
5168         }
5169         while (1) {
5170                 nritems = btrfs_header_nritems(cur);
5171                 level = btrfs_header_level(cur);
5172                 sret = bin_search(cur, min_key, level, &slot);
5173
5174                 /* at the lowest level, we're done, setup the path and exit */
5175                 if (level == path->lowest_level) {
5176                         if (slot >= nritems)
5177                                 goto find_next_key;
5178                         ret = 0;
5179                         path->slots[level] = slot;
5180                         btrfs_item_key_to_cpu(cur, &found_key, slot);
5181                         goto out;
5182                 }
5183                 if (sret && slot > 0)
5184                         slot--;
5185                 /*
5186                  * check this node pointer against the min_trans parameters.
5187                  * If it is too old, old, skip to the next one.
5188                  */
5189                 while (slot < nritems) {
5190                         u64 gen;
5191
5192                         gen = btrfs_node_ptr_generation(cur, slot);
5193                         if (gen < min_trans) {
5194                                 slot++;
5195                                 continue;
5196                         }
5197                         break;
5198                 }
5199 find_next_key:
5200                 /*
5201                  * we didn't find a candidate key in this node, walk forward
5202                  * and find another one
5203                  */
5204                 if (slot >= nritems) {
5205                         path->slots[level] = slot;
5206                         btrfs_set_path_blocking(path);
5207                         sret = btrfs_find_next_key(root, path, min_key, level,
5208                                                   min_trans);
5209                         if (sret == 0) {
5210                                 btrfs_release_path(path);
5211                                 goto again;
5212                         } else {
5213                                 goto out;
5214                         }
5215                 }
5216                 /* save our key for returning back */
5217                 btrfs_node_key_to_cpu(cur, &found_key, slot);
5218                 path->slots[level] = slot;
5219                 if (level == path->lowest_level) {
5220                         ret = 0;
5221                         goto out;
5222                 }
5223                 btrfs_set_path_blocking(path);
5224                 cur = read_node_slot(fs_info, cur, slot);
5225                 if (IS_ERR(cur)) {
5226                         ret = PTR_ERR(cur);
5227                         goto out;
5228                 }
5229
5230                 btrfs_tree_read_lock(cur);
5231
5232                 path->locks[level - 1] = BTRFS_READ_LOCK;
5233                 path->nodes[level - 1] = cur;
5234                 unlock_up(path, level, 1, 0, NULL);
5235                 btrfs_clear_path_blocking(path, NULL, 0);
5236         }
5237 out:
5238         path->keep_locks = keep_locks;
5239         if (ret == 0) {
5240                 btrfs_unlock_up_safe(path, path->lowest_level + 1);
5241                 btrfs_set_path_blocking(path);
5242                 memcpy(min_key, &found_key, sizeof(found_key));
5243         }
5244         return ret;
5245 }
5246
5247 static int tree_move_down(struct btrfs_fs_info *fs_info,
5248                            struct btrfs_path *path,
5249                            int *level)
5250 {
5251         struct extent_buffer *eb;
5252
5253         BUG_ON(*level == 0);
5254         eb = read_node_slot(fs_info, path->nodes[*level], path->slots[*level]);
5255         if (IS_ERR(eb))
5256                 return PTR_ERR(eb);
5257
5258         path->nodes[*level - 1] = eb;
5259         path->slots[*level - 1] = 0;
5260         (*level)--;
5261         return 0;
5262 }
5263
5264 static int tree_move_next_or_upnext(struct btrfs_path *path,
5265                                     int *level, int root_level)
5266 {
5267         int ret = 0;
5268         int nritems;
5269         nritems = btrfs_header_nritems(path->nodes[*level]);
5270
5271         path->slots[*level]++;
5272
5273         while (path->slots[*level] >= nritems) {
5274                 if (*level == root_level)
5275                         return -1;
5276
5277                 /* move upnext */
5278                 path->slots[*level] = 0;
5279                 free_extent_buffer(path->nodes[*level]);
5280                 path->nodes[*level] = NULL;
5281                 (*level)++;
5282                 path->slots[*level]++;
5283
5284                 nritems = btrfs_header_nritems(path->nodes[*level]);
5285                 ret = 1;
5286         }
5287         return ret;
5288 }
5289
5290 /*
5291  * Returns 1 if it had to move up and next. 0 is returned if it moved only next
5292  * or down.
5293  */
5294 static int tree_advance(struct btrfs_fs_info *fs_info,
5295                         struct btrfs_path *path,
5296                         int *level, int root_level,
5297                         int allow_down,
5298                         struct btrfs_key *key)
5299 {
5300         int ret;
5301
5302         if (*level == 0 || !allow_down) {
5303                 ret = tree_move_next_or_upnext(path, level, root_level);
5304         } else {
5305                 ret = tree_move_down(fs_info, path, level);
5306         }
5307         if (ret >= 0) {
5308                 if (*level == 0)
5309                         btrfs_item_key_to_cpu(path->nodes[*level], key,
5310                                         path->slots[*level]);
5311                 else
5312                         btrfs_node_key_to_cpu(path->nodes[*level], key,
5313                                         path->slots[*level]);
5314         }
5315         return ret;
5316 }
5317
5318 static int tree_compare_item(struct btrfs_path *left_path,
5319                              struct btrfs_path *right_path,
5320                              char *tmp_buf)
5321 {
5322         int cmp;
5323         int len1, len2;
5324         unsigned long off1, off2;
5325
5326         len1 = btrfs_item_size_nr(left_path->nodes[0], left_path->slots[0]);
5327         len2 = btrfs_item_size_nr(right_path->nodes[0], right_path->slots[0]);
5328         if (len1 != len2)
5329                 return 1;
5330
5331         off1 = btrfs_item_ptr_offset(left_path->nodes[0], left_path->slots[0]);
5332         off2 = btrfs_item_ptr_offset(right_path->nodes[0],
5333                                 right_path->slots[0]);
5334
5335         read_extent_buffer(left_path->nodes[0], tmp_buf, off1, len1);
5336
5337         cmp = memcmp_extent_buffer(right_path->nodes[0], tmp_buf, off2, len1);
5338         if (cmp)
5339                 return 1;
5340         return 0;
5341 }
5342
5343 #define ADVANCE 1
5344 #define ADVANCE_ONLY_NEXT -1
5345
5346 /*
5347  * This function compares two trees and calls the provided callback for
5348  * every changed/new/deleted item it finds.
5349  * If shared tree blocks are encountered, whole subtrees are skipped, making
5350  * the compare pretty fast on snapshotted subvolumes.
5351  *
5352  * This currently works on commit roots only. As commit roots are read only,
5353  * we don't do any locking. The commit roots are protected with transactions.
5354  * Transactions are ended and rejoined when a commit is tried in between.
5355  *
5356  * This function checks for modifications done to the trees while comparing.
5357  * If it detects a change, it aborts immediately.
5358  */
5359 int btrfs_compare_trees(struct btrfs_root *left_root,
5360                         struct btrfs_root *right_root,
5361                         btrfs_changed_cb_t changed_cb, void *ctx)
5362 {
5363         struct btrfs_fs_info *fs_info = left_root->fs_info;
5364         int ret;
5365         int cmp;
5366         struct btrfs_path *left_path = NULL;
5367         struct btrfs_path *right_path = NULL;
5368         struct btrfs_key left_key;
5369         struct btrfs_key right_key;
5370         char *tmp_buf = NULL;
5371         int left_root_level;
5372         int right_root_level;
5373         int left_level;
5374         int right_level;
5375         int left_end_reached;
5376         int right_end_reached;
5377         int advance_left;
5378         int advance_right;
5379         u64 left_blockptr;
5380         u64 right_blockptr;
5381         u64 left_gen;
5382         u64 right_gen;
5383
5384         left_path = btrfs_alloc_path();
5385         if (!left_path) {
5386                 ret = -ENOMEM;
5387                 goto out;
5388         }
5389         right_path = btrfs_alloc_path();
5390         if (!right_path) {
5391                 ret = -ENOMEM;
5392                 goto out;
5393         }
5394
5395         tmp_buf = kvmalloc(fs_info->nodesize, GFP_KERNEL);
5396         if (!tmp_buf) {
5397                 ret = -ENOMEM;
5398                 goto out;
5399         }
5400
5401         left_path->search_commit_root = 1;
5402         left_path->skip_locking = 1;
5403         right_path->search_commit_root = 1;
5404         right_path->skip_locking = 1;
5405
5406         /*
5407          * Strategy: Go to the first items of both trees. Then do
5408          *
5409          * If both trees are at level 0
5410          *   Compare keys of current items
5411          *     If left < right treat left item as new, advance left tree
5412          *       and repeat
5413          *     If left > right treat right item as deleted, advance right tree
5414          *       and repeat
5415          *     If left == right do deep compare of items, treat as changed if
5416          *       needed, advance both trees and repeat
5417          * If both trees are at the same level but not at level 0
5418          *   Compare keys of current nodes/leafs
5419          *     If left < right advance left tree and repeat
5420          *     If left > right advance right tree and repeat
5421          *     If left == right compare blockptrs of the next nodes/leafs
5422          *       If they match advance both trees but stay at the same level
5423          *         and repeat
5424          *       If they don't match advance both trees while allowing to go
5425          *         deeper and repeat
5426          * If tree levels are different
5427          *   Advance the tree that needs it and repeat
5428          *
5429          * Advancing a tree means:
5430          *   If we are at level 0, try to go to the next slot. If that's not
5431          *   possible, go one level up and repeat. Stop when we found a level
5432          *   where we could go to the next slot. We may at this point be on a
5433          *   node or a leaf.
5434          *
5435          *   If we are not at level 0 and not on shared tree blocks, go one
5436          *   level deeper.
5437          *
5438          *   If we are not at level 0 and on shared tree blocks, go one slot to
5439          *   the right if possible or go up and right.
5440          */
5441
5442         down_read(&fs_info->commit_root_sem);
5443         left_level = btrfs_header_level(left_root->commit_root);
5444         left_root_level = left_level;
5445         left_path->nodes[left_level] = left_root->commit_root;
5446         extent_buffer_get(left_path->nodes[left_level]);
5447
5448         right_level = btrfs_header_level(right_root->commit_root);
5449         right_root_level = right_level;
5450         right_path->nodes[right_level] = right_root->commit_root;
5451         extent_buffer_get(right_path->nodes[right_level]);
5452         up_read(&fs_info->commit_root_sem);
5453
5454         if (left_level == 0)
5455                 btrfs_item_key_to_cpu(left_path->nodes[left_level],
5456                                 &left_key, left_path->slots[left_level]);
5457         else
5458                 btrfs_node_key_to_cpu(left_path->nodes[left_level],
5459                                 &left_key, left_path->slots[left_level]);
5460         if (right_level == 0)
5461                 btrfs_item_key_to_cpu(right_path->nodes[right_level],
5462                                 &right_key, right_path->slots[right_level]);
5463         else
5464                 btrfs_node_key_to_cpu(right_path->nodes[right_level],
5465                                 &right_key, right_path->slots[right_level]);
5466
5467         left_end_reached = right_end_reached = 0;
5468         advance_left = advance_right = 0;
5469
5470         while (1) {
5471                 if (advance_left && !left_end_reached) {
5472                         ret = tree_advance(fs_info, left_path, &left_level,
5473                                         left_root_level,
5474                                         advance_left != ADVANCE_ONLY_NEXT,
5475                                         &left_key);
5476                         if (ret == -1)
5477                                 left_end_reached = ADVANCE;
5478                         else if (ret < 0)
5479                                 goto out;
5480                         advance_left = 0;
5481                 }
5482                 if (advance_right && !right_end_reached) {
5483                         ret = tree_advance(fs_info, right_path, &right_level,
5484                                         right_root_level,
5485                                         advance_right != ADVANCE_ONLY_NEXT,
5486                                         &right_key);
5487                         if (ret == -1)
5488                                 right_end_reached = ADVANCE;
5489                         else if (ret < 0)
5490                                 goto out;
5491                         advance_right = 0;
5492                 }
5493
5494                 if (left_end_reached && right_end_reached) {
5495                         ret = 0;
5496                         goto out;
5497                 } else if (left_end_reached) {
5498                         if (right_level == 0) {
5499                                 ret = changed_cb(left_path, right_path,
5500                                                 &right_key,
5501                                                 BTRFS_COMPARE_TREE_DELETED,
5502                                                 ctx);
5503                                 if (ret < 0)
5504                                         goto out;
5505                         }
5506                         advance_right = ADVANCE;
5507                         continue;
5508                 } else if (right_end_reached) {
5509                         if (left_level == 0) {
5510                                 ret = changed_cb(left_path, right_path,
5511                                                 &left_key,
5512                                                 BTRFS_COMPARE_TREE_NEW,
5513                                                 ctx);
5514                                 if (ret < 0)
5515                                         goto out;
5516                         }
5517                         advance_left = ADVANCE;
5518                         continue;
5519                 }
5520
5521                 if (left_level == 0 && right_level == 0) {
5522                         cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5523                         if (cmp < 0) {
5524                                 ret = changed_cb(left_path, right_path,
5525                                                 &left_key,
5526                                                 BTRFS_COMPARE_TREE_NEW,
5527                                                 ctx);
5528                                 if (ret < 0)
5529                                         goto out;
5530                                 advance_left = ADVANCE;
5531                         } else if (cmp > 0) {
5532                                 ret = changed_cb(left_path, right_path,
5533                                                 &right_key,
5534                                                 BTRFS_COMPARE_TREE_DELETED,
5535                                                 ctx);
5536                                 if (ret < 0)
5537                                         goto out;
5538                                 advance_right = ADVANCE;
5539                         } else {
5540                                 enum btrfs_compare_tree_result result;
5541
5542                                 WARN_ON(!extent_buffer_uptodate(left_path->nodes[0]));
5543                                 ret = tree_compare_item(left_path, right_path,
5544                                                         tmp_buf);
5545                                 if (ret)
5546                                         result = BTRFS_COMPARE_TREE_CHANGED;
5547                                 else
5548                                         result = BTRFS_COMPARE_TREE_SAME;
5549                                 ret = changed_cb(left_path, right_path,
5550                                                  &left_key, result, ctx);
5551                                 if (ret < 0)
5552                                         goto out;
5553                                 advance_left = ADVANCE;
5554                                 advance_right = ADVANCE;
5555                         }
5556                 } else if (left_level == right_level) {
5557                         cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5558                         if (cmp < 0) {
5559                                 advance_left = ADVANCE;
5560                         } else if (cmp > 0) {
5561                                 advance_right = ADVANCE;
5562                         } else {
5563                                 left_blockptr = btrfs_node_blockptr(
5564                                                 left_path->nodes[left_level],
5565                                                 left_path->slots[left_level]);
5566                                 right_blockptr = btrfs_node_blockptr(
5567                                                 right_path->nodes[right_level],
5568                                                 right_path->slots[right_level]);
5569                                 left_gen = btrfs_node_ptr_generation(
5570                                                 left_path->nodes[left_level],
5571                                                 left_path->slots[left_level]);
5572                                 right_gen = btrfs_node_ptr_generation(
5573                                                 right_path->nodes[right_level],
5574                                                 right_path->slots[right_level]);
5575                                 if (left_blockptr == right_blockptr &&
5576                                     left_gen == right_gen) {
5577                                         /*
5578                                          * As we're on a shared block, don't
5579                                          * allow to go deeper.
5580                                          */
5581                                         advance_left = ADVANCE_ONLY_NEXT;
5582                                         advance_right = ADVANCE_ONLY_NEXT;
5583                                 } else {
5584                                         advance_left = ADVANCE;
5585                                         advance_right = ADVANCE;
5586                                 }
5587                         }
5588                 } else if (left_level < right_level) {
5589                         advance_right = ADVANCE;
5590                 } else {
5591                         advance_left = ADVANCE;
5592                 }
5593         }
5594
5595 out:
5596         btrfs_free_path(left_path);
5597         btrfs_free_path(right_path);
5598         kvfree(tmp_buf);
5599         return ret;
5600 }
5601
5602 /*
5603  * this is similar to btrfs_next_leaf, but does not try to preserve
5604  * and fixup the path.  It looks for and returns the next key in the
5605  * tree based on the current path and the min_trans parameters.
5606  *
5607  * 0 is returned if another key is found, < 0 if there are any errors
5608  * and 1 is returned if there are no higher keys in the tree
5609  *
5610  * path->keep_locks should be set to 1 on the search made before
5611  * calling this function.
5612  */
5613 int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
5614                         struct btrfs_key *key, int level, u64 min_trans)
5615 {
5616         int slot;
5617         struct extent_buffer *c;
5618
5619         WARN_ON(!path->keep_locks);
5620         while (level < BTRFS_MAX_LEVEL) {
5621                 if (!path->nodes[level])
5622                         return 1;
5623
5624                 slot = path->slots[level] + 1;
5625                 c = path->nodes[level];
5626 next:
5627                 if (slot >= btrfs_header_nritems(c)) {
5628                         int ret;
5629                         int orig_lowest;
5630                         struct btrfs_key cur_key;
5631                         if (level + 1 >= BTRFS_MAX_LEVEL ||
5632                             !path->nodes[level + 1])
5633                                 return 1;
5634
5635                         if (path->locks[level + 1]) {
5636                                 level++;
5637                                 continue;
5638                         }
5639
5640                         slot = btrfs_header_nritems(c) - 1;
5641                         if (level == 0)
5642                                 btrfs_item_key_to_cpu(c, &cur_key, slot);
5643                         else
5644                                 btrfs_node_key_to_cpu(c, &cur_key, slot);
5645
5646                         orig_lowest = path->lowest_level;
5647                         btrfs_release_path(path);
5648                         path->lowest_level = level;
5649                         ret = btrfs_search_slot(NULL, root, &cur_key, path,
5650                                                 0, 0);
5651                         path->lowest_level = orig_lowest;
5652                         if (ret < 0)
5653                                 return ret;
5654
5655                         c = path->nodes[level];
5656                         slot = path->slots[level];
5657                         if (ret == 0)
5658                                 slot++;
5659                         goto next;
5660                 }
5661
5662                 if (level == 0)
5663                         btrfs_item_key_to_cpu(c, key, slot);
5664                 else {
5665                         u64 gen = btrfs_node_ptr_generation(c, slot);
5666
5667                         if (gen < min_trans) {
5668                                 slot++;
5669                                 goto next;
5670                         }
5671                         btrfs_node_key_to_cpu(c, key, slot);
5672                 }
5673                 return 0;
5674         }
5675         return 1;
5676 }
5677
5678 /*
5679  * search the tree again to find a leaf with greater keys
5680  * returns 0 if it found something or 1 if there are no greater leaves.
5681  * returns < 0 on io errors.
5682  */
5683 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
5684 {
5685         return btrfs_next_old_leaf(root, path, 0);
5686 }
5687
5688 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
5689                         u64 time_seq)
5690 {
5691         int slot;
5692         int level;
5693         struct extent_buffer *c;
5694         struct extent_buffer *next;
5695         struct btrfs_key key;
5696         u32 nritems;
5697         int ret;
5698         int old_spinning = path->leave_spinning;
5699         int next_rw_lock = 0;
5700
5701         nritems = btrfs_header_nritems(path->nodes[0]);
5702         if (nritems == 0)
5703                 return 1;
5704
5705         btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
5706 again:
5707         level = 1;
5708         next = NULL;
5709         next_rw_lock = 0;
5710         btrfs_release_path(path);
5711
5712         path->keep_locks = 1;
5713         path->leave_spinning = 1;
5714
5715         if (time_seq)
5716                 ret = btrfs_search_old_slot(root, &key, path, time_seq);
5717         else
5718                 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5719         path->keep_locks = 0;
5720
5721         if (ret < 0)
5722                 return ret;
5723
5724         nritems = btrfs_header_nritems(path->nodes[0]);
5725         /*
5726          * by releasing the path above we dropped all our locks.  A balance
5727          * could have added more items next to the key that used to be
5728          * at the very end of the block.  So, check again here and
5729          * advance the path if there are now more items available.
5730          */
5731         if (nritems > 0 && path->slots[0] < nritems - 1) {
5732                 if (ret == 0)
5733                         path->slots[0]++;
5734                 ret = 0;
5735                 goto done;
5736         }
5737         /*
5738          * So the above check misses one case:
5739          * - after releasing the path above, someone has removed the item that
5740          *   used to be at the very end of the block, and balance between leafs
5741          *   gets another one with bigger key.offset to replace it.
5742          *
5743          * This one should be returned as well, or we can get leaf corruption
5744          * later(esp. in __btrfs_drop_extents()).
5745          *
5746          * And a bit more explanation about this check,
5747          * with ret > 0, the key isn't found, the path points to the slot
5748          * where it should be inserted, so the path->slots[0] item must be the
5749          * bigger one.
5750          */
5751         if (nritems > 0 && ret > 0 && path->slots[0] == nritems - 1) {
5752                 ret = 0;
5753                 goto done;
5754         }
5755
5756         while (level < BTRFS_MAX_LEVEL) {
5757                 if (!path->nodes[level]) {
5758                         ret = 1;
5759                         goto done;
5760                 }
5761
5762                 slot = path->slots[level] + 1;
5763                 c = path->nodes[level];
5764                 if (slot >= btrfs_header_nritems(c)) {
5765                         level++;
5766                         if (level == BTRFS_MAX_LEVEL) {
5767                                 ret = 1;
5768                                 goto done;
5769                         }
5770                         continue;
5771                 }
5772
5773                 if (next) {
5774                         btrfs_tree_unlock_rw(next, next_rw_lock);
5775                         free_extent_buffer(next);
5776                 }
5777
5778                 next = c;
5779                 next_rw_lock = path->locks[level];
5780                 ret = read_block_for_search(root, path, &next, level,
5781                                             slot, &key);
5782                 if (ret == -EAGAIN)
5783                         goto again;
5784
5785                 if (ret < 0) {
5786                         btrfs_release_path(path);
5787                         goto done;
5788                 }
5789
5790                 if (!path->skip_locking) {
5791                         ret = btrfs_try_tree_read_lock(next);
5792                         if (!ret && time_seq) {
5793                                 /*
5794                                  * If we don't get the lock, we may be racing
5795                                  * with push_leaf_left, holding that lock while
5796                                  * itself waiting for the leaf we've currently
5797                                  * locked. To solve this situation, we give up
5798                                  * on our lock and cycle.
5799                                  */
5800                                 free_extent_buffer(next);
5801                                 btrfs_release_path(path);
5802                                 cond_resched();
5803                                 goto again;
5804                         }
5805                         if (!ret) {
5806                                 btrfs_set_path_blocking(path);
5807                                 btrfs_tree_read_lock(next);
5808                                 btrfs_clear_path_blocking(path, next,
5809                                                           BTRFS_READ_LOCK);
5810                         }
5811                         next_rw_lock = BTRFS_READ_LOCK;
5812                 }
5813                 break;
5814         }
5815         path->slots[level] = slot;
5816         while (1) {
5817                 level--;
5818                 c = path->nodes[level];
5819                 if (path->locks[level])
5820                         btrfs_tree_unlock_rw(c, path->locks[level]);
5821
5822                 free_extent_buffer(c);
5823                 path->nodes[level] = next;
5824                 path->slots[level] = 0;
5825                 if (!path->skip_locking)
5826                         path->locks[level] = next_rw_lock;
5827                 if (!level)
5828                         break;
5829
5830                 ret = read_block_for_search(root, path, &next, level,
5831                                             0, &key);
5832                 if (ret == -EAGAIN)
5833                         goto again;
5834
5835                 if (ret < 0) {
5836                         btrfs_release_path(path);
5837                         goto done;
5838                 }
5839
5840                 if (!path->skip_locking) {
5841                         ret = btrfs_try_tree_read_lock(next);
5842                         if (!ret) {
5843                                 btrfs_set_path_blocking(path);
5844                                 btrfs_tree_read_lock(next);
5845                                 btrfs_clear_path_blocking(path, next,
5846                                                           BTRFS_READ_LOCK);
5847                         }
5848                         next_rw_lock = BTRFS_READ_LOCK;
5849                 }
5850         }
5851         ret = 0;
5852 done:
5853         unlock_up(path, 0, 1, 0, NULL);
5854         path->leave_spinning = old_spinning;
5855         if (!old_spinning)
5856                 btrfs_set_path_blocking(path);
5857
5858         return ret;
5859 }
5860
5861 /*
5862  * this uses btrfs_prev_leaf to walk backwards in the tree, and keeps
5863  * searching until it gets past min_objectid or finds an item of 'type'
5864  *
5865  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5866  */
5867 int btrfs_previous_item(struct btrfs_root *root,
5868                         struct btrfs_path *path, u64 min_objectid,
5869                         int type)
5870 {
5871         struct btrfs_key found_key;
5872         struct extent_buffer *leaf;
5873         u32 nritems;
5874         int ret;
5875
5876         while (1) {
5877                 if (path->slots[0] == 0) {
5878                         btrfs_set_path_blocking(path);
5879                         ret = btrfs_prev_leaf(root, path);
5880                         if (ret != 0)
5881                                 return ret;
5882                 } else {
5883                         path->slots[0]--;
5884                 }
5885                 leaf = path->nodes[0];
5886                 nritems = btrfs_header_nritems(leaf);
5887                 if (nritems == 0)
5888                         return 1;
5889                 if (path->slots[0] == nritems)
5890                         path->slots[0]--;
5891
5892                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5893                 if (found_key.objectid < min_objectid)
5894                         break;
5895                 if (found_key.type == type)
5896                         return 0;
5897                 if (found_key.objectid == min_objectid &&
5898                     found_key.type < type)
5899                         break;
5900         }
5901         return 1;
5902 }
5903
5904 /*
5905  * search in extent tree to find a previous Metadata/Data extent item with
5906  * min objecitd.
5907  *
5908  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5909  */
5910 int btrfs_previous_extent_item(struct btrfs_root *root,
5911                         struct btrfs_path *path, u64 min_objectid)
5912 {
5913         struct btrfs_key found_key;
5914         struct extent_buffer *leaf;
5915         u32 nritems;
5916         int ret;
5917
5918         while (1) {
5919                 if (path->slots[0] == 0) {
5920                         btrfs_set_path_blocking(path);
5921                         ret = btrfs_prev_leaf(root, path);
5922                         if (ret != 0)
5923                                 return ret;
5924                 } else {
5925                         path->slots[0]--;
5926                 }
5927                 leaf = path->nodes[0];
5928                 nritems = btrfs_header_nritems(leaf);
5929                 if (nritems == 0)
5930                         return 1;
5931                 if (path->slots[0] == nritems)
5932                         path->slots[0]--;
5933
5934                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5935                 if (found_key.objectid < min_objectid)
5936                         break;
5937                 if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
5938                     found_key.type == BTRFS_METADATA_ITEM_KEY)
5939                         return 0;
5940                 if (found_key.objectid == min_objectid &&
5941                     found_key.type < BTRFS_EXTENT_ITEM_KEY)
5942                         break;
5943         }
5944         return 1;
5945 }