fs/btrfs/backref.c

   1 /*
   2  * Copyright (C) 2011 STRATO.  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/vmalloc.h>
  20 #include "ctree.h"
  21 #include "disk-io.h"
  22 #include "backref.h"
  23 #include "ulist.h"
  24 #include "transaction.h"
  25 #include "delayed-ref.h"
  26 #include "locking.h"
  27
  28 struct extent_inode_elem {
  29         u64 inum;
  30         u64 offset;
  31         struct extent_inode_elem *next;
  32 };
  33
  34 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
  35                                 struct btrfs_file_extent_item *fi,
  36                                 u64 extent_item_pos,
  37                                 struct extent_inode_elem **eie)
  38 {
  39         u64 offset = 0;
  40         struct extent_inode_elem *e;
  41
  42         if (!btrfs_file_extent_compression(eb, fi) &&
  43             !btrfs_file_extent_encryption(eb, fi) &&
  44             !btrfs_file_extent_other_encoding(eb, fi)) {
  45                 u64 data_offset;
  46                 u64 data_len;
  47
  48                 data_offset = btrfs_file_extent_offset(eb, fi);
  49                 data_len = btrfs_file_extent_num_bytes(eb, fi);
  50
  51                 if (extent_item_pos < data_offset ||
  52                     extent_item_pos >= data_offset + data_len)
  53                         return 1;
  54                 offset = extent_item_pos - data_offset;
  55         }
  56
  57         e = kmalloc(sizeof(*e), GFP_NOFS);
  58         if (!e)
  59                 return -ENOMEM;
  60
  61         e->next = *eie;
  62         e->inum = key->objectid;
  63         e->offset = key->offset + offset;
  64         *eie = e;
  65
  66         return 0;
  67 }
  68
  69 static void free_inode_elem_list(struct extent_inode_elem *eie)
  70 {
  71         struct extent_inode_elem *eie_next;
  72
  73         for (; eie; eie = eie_next) {
  74                 eie_next = eie->next;
  75                 kfree(eie);
  76         }
  77 }
  78
  79 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
  80                                 u64 extent_item_pos,
  81                                 struct extent_inode_elem **eie)
  82 {
  83         u64 disk_byte;
  84         struct btrfs_key key;
  85         struct btrfs_file_extent_item *fi;
  86         int slot;
  87         int nritems;
  88         int extent_type;
  89         int ret;
  90
  91         /*
  92          * from the shared data ref, we only have the leaf but we need
  93          * the key. thus, we must look into all items and see that we
  94          * find one (some) with a reference to our extent item.
  95          */
  96         nritems = btrfs_header_nritems(eb);
  97         for (slot = 0; slot < nritems; ++slot) {
  98                 btrfs_item_key_to_cpu(eb, &key, slot);
  99                 if (key.type != BTRFS_EXTENT_DATA_KEY)
 100                         continue;
 101                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 102                 extent_type = btrfs_file_extent_type(eb, fi);
 103                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
 104                         continue;
 105                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
 106                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 107                 if (disk_byte != wanted_disk_byte)
 108                         continue;
 109
 110                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
 111                 if (ret < 0)
 112                         return ret;
 113         }
 114
 115         return 0;
 116 }
 117
 118 /*
 119  * this structure records all encountered refs on the way up to the root
 120  */
 121 struct __prelim_ref {
 122         struct list_head list;
 123         u64 root_id;
 124         struct btrfs_key key_for_search;
 125         int level;
 126         int count;
 127         struct extent_inode_elem *inode_list;
 128         u64 parent;
 129         u64 wanted_disk_byte;
 130 };
 131
 132 static struct kmem_cache *btrfs_prelim_ref_cache;
 133
 134 int __init btrfs_prelim_ref_init(void)
 135 {
 136         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
 137                                         sizeof(struct __prelim_ref),
 138                                         0,
 139                                         SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 140                                         NULL);
 141         if (!btrfs_prelim_ref_cache)
 142                 return -ENOMEM;
 143         return 0;
 144 }
 145
 146 void btrfs_prelim_ref_exit(void)
 147 {
 148         if (btrfs_prelim_ref_cache)
 149                 kmem_cache_destroy(btrfs_prelim_ref_cache);
 150 }
 151
 152 /*
 153  * the rules for all callers of this function are:
 154  * - obtaining the parent is the goal
 155  * - if you add a key, you must know that it is a correct key
 156  * - if you cannot add the parent or a correct key, then we will look into the
 157  *   block later to set a correct key
 158  *
 159  * delayed refs
 160  * ============
 161  *        backref type | shared | indirect | shared | indirect
 162  * information         |   tree |     tree |   data |     data
 163  * --------------------+--------+----------+--------+----------
 164  *      parent logical |    y   |     -    |    -   |     -
 165  *      key to resolve |    -   |     y    |    y   |     y
 166  *  tree block logical |    -   |     -    |    -   |     -
 167  *  root for resolving |    y   |     y    |    y   |     y
 168  *
 169  * - column 1:       we've the parent -> done
 170  * - column 2, 3, 4: we use the key to find the parent
 171  *
 172  * on disk refs (inline or keyed)
 173  * ==============================
 174  *        backref type | shared | indirect | shared | indirect
 175  * information         |   tree |     tree |   data |     data
 176  * --------------------+--------+----------+--------+----------
 177  *      parent logical |    y   |     -    |    y   |     -
 178  *      key to resolve |    -   |     -    |    -   |     y
 179  *  tree block logical |    y   |     y    |    y   |     y
 180  *  root for resolving |    -   |     y    |    y   |     y
 181  *
 182  * - column 1, 3: we've the parent -> done
 183  * - column 2:    we take the first key from the block to find the parent
 184  *                (see __add_missing_keys)
 185  * - column 4:    we use the key to find the parent
 186  *
 187  * additional information that's available but not required to find the parent
 188  * block might help in merging entries to gain some speed.
 189  */
 190
 191 static int __add_prelim_ref(struct list_head *head, u64 root_id,
 192                             struct btrfs_key *key, int level,
 193                             u64 parent, u64 wanted_disk_byte, int count,
 194                             gfp_t gfp_mask)
 195 {
 196         struct __prelim_ref *ref;
 197
 198         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
 199                 return 0;
 200
 201         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
 202         if (!ref)
 203                 return -ENOMEM;
 204
 205         ref->root_id = root_id;
 206         if (key)
 207                 ref->key_for_search = *key;
 208         else
 209                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
 210
 211         ref->inode_list = NULL;
 212         ref->level = level;
 213         ref->count = count;
 214         ref->parent = parent;
 215         ref->wanted_disk_byte = wanted_disk_byte;
 216         list_add_tail(&ref->list, head);
 217
 218         return 0;
 219 }
 220
 221 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
 222                            struct ulist *parents, struct __prelim_ref *ref,
 223                            int level, u64 time_seq, const u64 *extent_item_pos)
 224 {
 225         int ret = 0;
 226         int slot;
 227         struct extent_buffer *eb;
 228         struct btrfs_key key;
 229         struct btrfs_key *key_for_search = &ref->key_for_search;
 230         struct btrfs_file_extent_item *fi;
 231         struct extent_inode_elem *eie = NULL, *old = NULL;
 232         u64 disk_byte;
 233         u64 wanted_disk_byte = ref->wanted_disk_byte;
 234         u64 count = 0;
 235
 236         if (level != 0) {
 237                 eb = path->nodes[level];
 238                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
 239                 if (ret < 0)
 240                         return ret;
 241                 return 0;
 242         }
 243
 244         /*
 245          * We normally enter this function with the path already pointing to
 246          * the first item to check. But sometimes, we may enter it with
 247          * slot==nritems. In that case, go to the next leaf before we continue.
 248          */
 249         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
 250                 ret = btrfs_next_old_leaf(root, path, time_seq);
 251
 252         while (!ret && count < ref->count) {
 253                 eb = path->nodes[0];
 254                 slot = path->slots[0];
 255
 256                 btrfs_item_key_to_cpu(eb, &key, slot);
 257
 258                 if (key.objectid != key_for_search->objectid ||
 259                     key.type != BTRFS_EXTENT_DATA_KEY)
 260                         break;
 261
 262                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 263                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 264
 265                 if (disk_byte == wanted_disk_byte) {
 266                         eie = NULL;
 267                         old = NULL;
 268                         count++;
 269                         if (extent_item_pos) {
 270                                 ret = check_extent_in_eb(&key, eb, fi,
 271                                                 *extent_item_pos,
 272                                                 &eie);
 273                                 if (ret < 0)
 274                                         break;
 275                         }
 276                         if (ret > 0)
 277                                 goto next;
 278                         ret = ulist_add_merge(parents, eb->start,
 279                                               (uintptr_t)eie,
 280                                               (u64 *)&old, GFP_NOFS);
 281                         if (ret < 0)
 282                                 break;
 283                         if (!ret && extent_item_pos) {
 284                                 while (old->next)
 285                                         old = old->next;
 286                                 old->next = eie;
 287                         }
 288                         eie = NULL;
 289                 }
 290 next:
 291                 ret = btrfs_next_old_item(root, path, time_seq);
 292         }
 293
 294         if (ret > 0)
 295                 ret = 0;
 296         else if (ret < 0)
 297                 free_inode_elem_list(eie);
 298         return ret;
 299 }
 300
 301 /*
 302  * resolve an indirect backref in the form (root_id, key, level)
 303  * to a logical address
 304  */
 305 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 306                                   struct btrfs_path *path, u64 time_seq,
 307                                   struct __prelim_ref *ref,
 308                                   struct ulist *parents,
 309                                   const u64 *extent_item_pos)
 310 {
 311         struct btrfs_root *root;
 312         struct btrfs_key root_key;
 313         struct extent_buffer *eb;
 314         int ret = 0;
 315         int root_level;
 316         int level = ref->level;
 317         int index;
 318
 319         root_key.objectid = ref->root_id;
 320         root_key.type = BTRFS_ROOT_ITEM_KEY;
 321         root_key.offset = (u64)-1;
 322
 323         index = srcu_read_lock(&fs_info->subvol_srcu);
 324
 325         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
 326         if (IS_ERR(root)) {
 327                 srcu_read_unlock(&fs_info->subvol_srcu, index);
 328                 ret = PTR_ERR(root);
 329                 goto out;
 330         }
 331
 332         root_level = btrfs_old_root_level(root, time_seq);
 333
 334         if (root_level + 1 == level) {
 335                 srcu_read_unlock(&fs_info->subvol_srcu, index);
 336                 goto out;
 337         }
 338
 339         path->lowest_level = level;
 340         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
 341
 342         /* root node has been locked, we can release @subvol_srcu safely here */
 343         srcu_read_unlock(&fs_info->subvol_srcu, index);
 344
 345         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
 346                  "%d for key (%llu %u %llu)\n",
 347                  ref->root_id, level, ref->count, ret,
 348                  ref->key_for_search.objectid, ref->key_for_search.type,
 349                  ref->key_for_search.offset);
 350         if (ret < 0)
 351                 goto out;
 352
 353         eb = path->nodes[level];
 354         while (!eb) {
 355                 if (WARN_ON(!level)) {
 356                         ret = 1;
 357                         goto out;
 358                 }
 359                 level--;
 360                 eb = path->nodes[level];
 361         }
 362
 363         ret = add_all_parents(root, path, parents, ref, level, time_seq,
 364                               extent_item_pos);
 365 out:
 366         path->lowest_level = 0;
 367         btrfs_release_path(path);
 368         return ret;
 369 }
 370
 371 /*
 372  * resolve all indirect backrefs from the list
 373  */
 374 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 375                                    struct btrfs_path *path, u64 time_seq,
 376                                    struct list_head *head,
 377                                    const u64 *extent_item_pos)
 378 {
 379         int err;
 380         int ret = 0;
 381         struct __prelim_ref *ref;
 382         struct __prelim_ref *ref_safe;
 383         struct __prelim_ref *new_ref;
 384         struct ulist *parents;
 385         struct ulist_node *node;
 386         struct ulist_iterator uiter;
 387
 388         parents = ulist_alloc(GFP_NOFS);
 389         if (!parents)
 390                 return -ENOMEM;
 391
 392         /*
 393          * _safe allows us to insert directly after the current item without
 394          * iterating over the newly inserted items.
 395          * we're also allowed to re-assign ref during iteration.
 396          */
 397         list_for_each_entry_safe(ref, ref_safe, head, list) {
 398                 if (ref->parent)        /* already direct */
 399                         continue;
 400                 if (ref->count == 0)
 401                         continue;
 402                 err = __resolve_indirect_ref(fs_info, path, time_seq, ref,
 403                                              parents, extent_item_pos);
 404                 /*
 405                  * we can only tolerate ENOENT,otherwise,we should catch error
 406                  * and return directly.
 407                  */
 408                 if (err == -ENOENT) {
 409                         continue;
 410                 } else if (err) {
 411                         ret = err;
 412                         goto out;
 413                 }
 414
 415                 /* we put the first parent into the ref at hand */
 416                 ULIST_ITER_INIT(&uiter);
 417                 node = ulist_next(parents, &uiter);
 418                 ref->parent = node ? node->val : 0;
 419                 ref->inode_list = node ?
 420                         (struct extent_inode_elem *)(uintptr_t)node->aux : NULL;
 421
 422                 /* additional parents require new refs being added here */
 423                 while ((node = ulist_next(parents, &uiter))) {
 424                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
 425                                                    GFP_NOFS);
 426                         if (!new_ref) {
 427                                 ret = -ENOMEM;
 428                                 goto out;
 429                         }
 430                         memcpy(new_ref, ref, sizeof(*ref));
 431                         new_ref->parent = node->val;
 432                         new_ref->inode_list = (struct extent_inode_elem *)
 433                                                         (uintptr_t)node->aux;
 434                         list_add(&new_ref->list, &ref->list);
 435                 }
 436                 ulist_reinit(parents);
 437         }
 438 out:
 439         ulist_free(parents);
 440         return ret;
 441 }
 442
 443 static inline int ref_for_same_block(struct __prelim_ref *ref1,
 444                                      struct __prelim_ref *ref2)
 445 {
 446         if (ref1->level != ref2->level)
 447                 return 0;
 448         if (ref1->root_id != ref2->root_id)
 449                 return 0;
 450         if (ref1->key_for_search.type != ref2->key_for_search.type)
 451                 return 0;
 452         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
 453                 return 0;
 454         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
 455                 return 0;
 456         if (ref1->parent != ref2->parent)
 457                 return 0;
 458
 459         return 1;
 460 }
 461
 462 /*
 463  * read tree blocks and add keys where required.
 464  */
 465 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
 466                               struct list_head *head)
 467 {
 468         struct list_head *pos;
 469         struct extent_buffer *eb;
 470
 471         list_for_each(pos, head) {
 472                 struct __prelim_ref *ref;
 473                 ref = list_entry(pos, struct __prelim_ref, list);
 474
 475                 if (ref->parent)
 476                         continue;
 477                 if (ref->key_for_search.type)
 478                         continue;
 479                 BUG_ON(!ref->wanted_disk_byte);
 480                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
 481                                      fs_info->tree_root->leafsize, 0);
 482                 if (!eb || !extent_buffer_uptodate(eb)) {
 483                         free_extent_buffer(eb);
 484                         return -EIO;
 485                 }
 486                 btrfs_tree_read_lock(eb);
 487                 if (btrfs_header_level(eb) == 0)
 488                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 489                 else
 490                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 491                 btrfs_tree_read_unlock(eb);
 492                 free_extent_buffer(eb);
 493         }
 494         return 0;
 495 }
 496
 497 /*
 498  * merge two lists of backrefs and adjust counts accordingly
 499  *
 500  * mode = 1: merge identical keys, if key is set
 501  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
 502  *           additionally, we could even add a key range for the blocks we
 503  *           looked into to merge even more (-> replace unresolved refs by those
 504  *           having a parent).
 505  * mode = 2: merge identical parents
 506  */
 507 static void __merge_refs(struct list_head *head, int mode)
 508 {
 509         struct list_head *pos1;
 510
 511         list_for_each(pos1, head) {
 512                 struct list_head *n2;
 513                 struct list_head *pos2;
 514                 struct __prelim_ref *ref1;
 515
 516                 ref1 = list_entry(pos1, struct __prelim_ref, list);
 517
 518                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
 519                      pos2 = n2, n2 = pos2->next) {
 520                         struct __prelim_ref *ref2;
 521                         struct __prelim_ref *xchg;
 522                         struct extent_inode_elem *eie;
 523
 524                         ref2 = list_entry(pos2, struct __prelim_ref, list);
 525
 526                         if (mode == 1) {
 527                                 if (!ref_for_same_block(ref1, ref2))
 528                                         continue;
 529                                 if (!ref1->parent && ref2->parent) {
 530                                         xchg = ref1;
 531                                         ref1 = ref2;
 532                                         ref2 = xchg;
 533                                 }
 534                         } else {
 535                                 if (ref1->parent != ref2->parent)
 536                                         continue;
 537                         }
 538
 539                         eie = ref1->inode_list;
 540                         while (eie && eie->next)
 541                                 eie = eie->next;
 542                         if (eie)
 543                                 eie->next = ref2->inode_list;
 544                         else
 545                                 ref1->inode_list = ref2->inode_list;
 546                         ref1->count += ref2->count;
 547
 548                         list_del(&ref2->list);
 549                         kmem_cache_free(btrfs_prelim_ref_cache, ref2);
 550                 }
 551
 552         }
 553 }
 554
 555 /*
 556  * add all currently queued delayed refs from this head whose seq nr is
 557  * smaller or equal that seq to the list
 558  */
 559 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 560                               struct list_head *prefs)
 561 {
 562         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 563         struct rb_node *n = &head->node.rb_node;
 564         struct btrfs_key key;
 565         struct btrfs_key op_key = {0};
 566         int sgn;
 567         int ret = 0;
 568
 569         if (extent_op && extent_op->update_key)
 570                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
 571
 572         spin_lock(&head->lock);
 573         n = rb_first(&head->ref_root);
 574         while (n) {
 575                 struct btrfs_delayed_ref_node *node;
 576                 node = rb_entry(n, struct btrfs_delayed_ref_node,
 577                                 rb_node);
 578                 n = rb_next(n);
 579                 if (node->seq > seq)
 580                         continue;
 581
 582                 switch (node->action) {
 583                 case BTRFS_ADD_DELAYED_EXTENT:
 584                 case BTRFS_UPDATE_DELAYED_HEAD:
 585                         WARN_ON(1);
 586                         continue;
 587                 case BTRFS_ADD_DELAYED_REF:
 588                         sgn = 1;
 589                         break;
 590                 case BTRFS_DROP_DELAYED_REF:
 591                         sgn = -1;
 592                         break;
 593                 default:
 594                         BUG_ON(1);
 595                 }
 596                 switch (node->type) {
 597                 case BTRFS_TREE_BLOCK_REF_KEY: {
 598                         struct btrfs_delayed_tree_ref *ref;
 599
 600                         ref = btrfs_delayed_node_to_tree_ref(node);
 601                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
 602                                                ref->level + 1, 0, node->bytenr,
 603                                                node->ref_mod * sgn, GFP_ATOMIC);
 604                         break;
 605                 }
 606                 case BTRFS_SHARED_BLOCK_REF_KEY: {
 607                         struct btrfs_delayed_tree_ref *ref;
 608
 609                         ref = btrfs_delayed_node_to_tree_ref(node);
 610                         ret = __add_prelim_ref(prefs, ref->root, NULL,
 611                                                ref->level + 1, ref->parent,
 612                                                node->bytenr,
 613                                                node->ref_mod * sgn, GFP_ATOMIC);
 614                         break;
 615                 }
 616                 case BTRFS_EXTENT_DATA_REF_KEY: {
 617                         struct btrfs_delayed_data_ref *ref;
 618                         ref = btrfs_delayed_node_to_data_ref(node);
 619
 620                         key.objectid = ref->objectid;
 621                         key.type = BTRFS_EXTENT_DATA_KEY;
 622                         key.offset = ref->offset;
 623                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
 624                                                node->bytenr,
 625                                                node->ref_mod * sgn, GFP_ATOMIC);
 626                         break;
 627                 }
 628                 case BTRFS_SHARED_DATA_REF_KEY: {
 629                         struct btrfs_delayed_data_ref *ref;
 630
 631                         ref = btrfs_delayed_node_to_data_ref(node);
 632
 633                         key.objectid = ref->objectid;
 634                         key.type = BTRFS_EXTENT_DATA_KEY;
 635                         key.offset = ref->offset;
 636                         ret = __add_prelim_ref(prefs, ref->root, &key, 0,
 637                                                ref->parent, node->bytenr,
 638                                                node->ref_mod * sgn, GFP_ATOMIC);
 639                         break;
 640                 }
 641                 default:
 642                         WARN_ON(1);
 643                 }
 644                 if (ret)
 645                         break;
 646         }
 647         spin_unlock(&head->lock);
 648         return ret;
 649 }
 650
 651 /*
 652  * add all inline backrefs for bytenr to the list
 653  */
 654 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
 655                              struct btrfs_path *path, u64 bytenr,
 656                              int *info_level, struct list_head *prefs)
 657 {
 658         int ret = 0;
 659         int slot;
 660         struct extent_buffer *leaf;
 661         struct btrfs_key key;
 662         struct btrfs_key found_key;
 663         unsigned long ptr;
 664         unsigned long end;
 665         struct btrfs_extent_item *ei;
 666         u64 flags;
 667         u64 item_size;
 668
 669         /*
 670          * enumerate all inline refs
 671          */
 672         leaf = path->nodes[0];
 673         slot = path->slots[0];
 674
 675         item_size = btrfs_item_size_nr(leaf, slot);
 676         BUG_ON(item_size < sizeof(*ei));
 677
 678         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 679         flags = btrfs_extent_flags(leaf, ei);
 680         btrfs_item_key_to_cpu(leaf, &found_key, slot);
 681
 682         ptr = (unsigned long)(ei + 1);
 683         end = (unsigned long)ei + item_size;
 684
 685         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
 686             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 687                 struct btrfs_tree_block_info *info;
 688
 689                 info = (struct btrfs_tree_block_info *)ptr;
 690                 *info_level = btrfs_tree_block_level(leaf, info);
 691                 ptr += sizeof(struct btrfs_tree_block_info);
 692                 BUG_ON(ptr > end);
 693         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
 694                 *info_level = found_key.offset;
 695         } else {
 696                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 697         }
 698
 699         while (ptr < end) {
 700                 struct btrfs_extent_inline_ref *iref;
 701                 u64 offset;
 702                 int type;
 703
 704                 iref = (struct btrfs_extent_inline_ref *)ptr;
 705                 type = btrfs_extent_inline_ref_type(leaf, iref);
 706                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
 707
 708                 switch (type) {
 709                 case BTRFS_SHARED_BLOCK_REF_KEY:
 710                         ret = __add_prelim_ref(prefs, 0, NULL,
 711                                                 *info_level + 1, offset,
 712                                                 bytenr, 1, GFP_NOFS);
 713                         break;
 714                 case BTRFS_SHARED_DATA_REF_KEY: {
 715                         struct btrfs_shared_data_ref *sdref;
 716                         int count;
 717
 718                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
 719                         count = btrfs_shared_data_ref_count(leaf, sdref);
 720                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
 721                                                bytenr, count, GFP_NOFS);
 722                         break;
 723                 }
 724                 case BTRFS_TREE_BLOCK_REF_KEY:
 725                         ret = __add_prelim_ref(prefs, offset, NULL,
 726                                                *info_level + 1, 0,
 727                                                bytenr, 1, GFP_NOFS);
 728                         break;
 729                 case BTRFS_EXTENT_DATA_REF_KEY: {
 730                         struct btrfs_extent_data_ref *dref;
 731                         int count;
 732                         u64 root;
 733
 734                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
 735                         count = btrfs_extent_data_ref_count(leaf, dref);
 736                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 737                                                                       dref);
 738                         key.type = BTRFS_EXTENT_DATA_KEY;
 739                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 740                         root = btrfs_extent_data_ref_root(leaf, dref);
 741                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 742                                                bytenr, count, GFP_NOFS);
 743                         break;
 744                 }
 745                 default:
 746                         WARN_ON(1);
 747                 }
 748                 if (ret)
 749                         return ret;
 750                 ptr += btrfs_extent_inline_ref_size(type);
 751         }
 752
 753         return 0;
 754 }
 755
 756 /*
 757  * add all non-inline backrefs for bytenr to the list
 758  */
 759 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
 760                             struct btrfs_path *path, u64 bytenr,
 761                             int info_level, struct list_head *prefs)
 762 {
 763         struct btrfs_root *extent_root = fs_info->extent_root;
 764         int ret;
 765         int slot;
 766         struct extent_buffer *leaf;
 767         struct btrfs_key key;
 768
 769         while (1) {
 770                 ret = btrfs_next_item(extent_root, path);
 771                 if (ret < 0)
 772                         break;
 773                 if (ret) {
 774                         ret = 0;
 775                         break;
 776                 }
 777
 778                 slot = path->slots[0];
 779                 leaf = path->nodes[0];
 780                 btrfs_item_key_to_cpu(leaf, &key, slot);
 781
 782                 if (key.objectid != bytenr)
 783                         break;
 784                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
 785                         continue;
 786                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
 787                         break;
 788
 789                 switch (key.type) {
 790                 case BTRFS_SHARED_BLOCK_REF_KEY:
 791                         ret = __add_prelim_ref(prefs, 0, NULL,
 792                                                 info_level + 1, key.offset,
 793                                                 bytenr, 1, GFP_NOFS);
 794                         break;
 795                 case BTRFS_SHARED_DATA_REF_KEY: {
 796                         struct btrfs_shared_data_ref *sdref;
 797                         int count;
 798
 799                         sdref = btrfs_item_ptr(leaf, slot,
 800                                               struct btrfs_shared_data_ref);
 801                         count = btrfs_shared_data_ref_count(leaf, sdref);
 802                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
 803                                                 bytenr, count, GFP_NOFS);
 804                         break;
 805                 }
 806                 case BTRFS_TREE_BLOCK_REF_KEY:
 807                         ret = __add_prelim_ref(prefs, key.offset, NULL,
 808                                                info_level + 1, 0,
 809                                                bytenr, 1, GFP_NOFS);
 810                         break;
 811                 case BTRFS_EXTENT_DATA_REF_KEY: {
 812                         struct btrfs_extent_data_ref *dref;
 813                         int count;
 814                         u64 root;
 815
 816                         dref = btrfs_item_ptr(leaf, slot,
 817                                               struct btrfs_extent_data_ref);
 818                         count = btrfs_extent_data_ref_count(leaf, dref);
 819                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 820                                                                       dref);
 821                         key.type = BTRFS_EXTENT_DATA_KEY;
 822                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 823                         root = btrfs_extent_data_ref_root(leaf, dref);
 824                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 825                                                bytenr, count, GFP_NOFS);
 826                         break;
 827                 }
 828                 default:
 829                         WARN_ON(1);
 830                 }
 831                 if (ret)
 832                         return ret;
 833
 834         }
 835
 836         return ret;
 837 }
 838
 839 /*
 840  * this adds all existing backrefs (inline backrefs, backrefs and delayed
 841  * refs) for the given bytenr to the refs list, merges duplicates and resolves
 842  * indirect refs to their parent bytenr.
 843  * When roots are found, they're added to the roots list
 844  *
 845  * FIXME some caching might speed things up
 846  */
 847 static int find_parent_nodes(struct btrfs_trans_handle *trans,
 848                              struct btrfs_fs_info *fs_info, u64 bytenr,
 849                              u64 time_seq, struct ulist *refs,
 850                              struct ulist *roots, const u64 *extent_item_pos)
 851 {
 852         struct btrfs_key key;
 853         struct btrfs_path *path;
 854         struct btrfs_delayed_ref_root *delayed_refs = NULL;
 855         struct btrfs_delayed_ref_head *head;
 856         int info_level = 0;
 857         int ret;
 858         struct list_head prefs_delayed;
 859         struct list_head prefs;
 860         struct __prelim_ref *ref;
 861         struct extent_inode_elem *eie = NULL;
 862
 863         INIT_LIST_HEAD(&prefs);
 864         INIT_LIST_HEAD(&prefs_delayed);
 865
 866         key.objectid = bytenr;
 867         key.offset = (u64)-1;
 868         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
 869                 key.type = BTRFS_METADATA_ITEM_KEY;
 870         else
 871                 key.type = BTRFS_EXTENT_ITEM_KEY;
 872
 873         path = btrfs_alloc_path();
 874         if (!path)
 875                 return -ENOMEM;
 876         if (!trans) {
 877                 path->search_commit_root = 1;
 878                 path->skip_locking = 1;
 879         }
 880
 881         /*
 882          * grab both a lock on the path and a lock on the delayed ref head.
 883          * We need both to get a consistent picture of how the refs look
 884          * at a specified point in time
 885          */
 886 again:
 887         head = NULL;
 888
 889         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
 890         if (ret < 0)
 891                 goto out;
 892         BUG_ON(ret == 0);
 893
 894         if (trans) {
 895                 /*
 896                  * look if there are updates for this ref queued and lock the
 897                  * head
 898                  */
 899                 delayed_refs = &trans->transaction->delayed_refs;
 900                 spin_lock(&delayed_refs->lock);
 901                 head = btrfs_find_delayed_ref_head(trans, bytenr);
 902                 if (head) {
 903                         if (!mutex_trylock(&head->mutex)) {
 904                                 atomic_inc(&head->node.refs);
 905                                 spin_unlock(&delayed_refs->lock);
 906
 907                                 btrfs_release_path(path);
 908
 909                                 /*
 910                                  * Mutex was contended, block until it's
 911                                  * released and try again
 912                                  */
 913                                 mutex_lock(&head->mutex);
 914                                 mutex_unlock(&head->mutex);
 915                                 btrfs_put_delayed_ref(&head->node);
 916                                 goto again;
 917                         }
 918                         spin_unlock(&delayed_refs->lock);
 919                         ret = __add_delayed_refs(head, time_seq,
 920                                                  &prefs_delayed);
 921                         mutex_unlock(&head->mutex);
 922                         if (ret)
 923                                 goto out;
 924                 } else {
 925                         spin_unlock(&delayed_refs->lock);
 926                 }
 927         }
 928
 929         if (path->slots[0]) {
 930                 struct extent_buffer *leaf;
 931                 int slot;
 932
 933                 path->slots[0]--;
 934                 leaf = path->nodes[0];
 935                 slot = path->slots[0];
 936                 btrfs_item_key_to_cpu(leaf, &key, slot);
 937                 if (key.objectid == bytenr &&
 938                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
 939                      key.type == BTRFS_METADATA_ITEM_KEY)) {
 940                         ret = __add_inline_refs(fs_info, path, bytenr,
 941                                                 &info_level, &prefs);
 942                         if (ret)
 943                                 goto out;
 944                         ret = __add_keyed_refs(fs_info, path, bytenr,
 945                                                info_level, &prefs);
 946                         if (ret)
 947                                 goto out;
 948                 }
 949         }
 950         btrfs_release_path(path);
 951
 952         list_splice_init(&prefs_delayed, &prefs);
 953
 954         ret = __add_missing_keys(fs_info, &prefs);
 955         if (ret)
 956                 goto out;
 957
 958         __merge_refs(&prefs, 1);
 959
 960         ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs,
 961                                       extent_item_pos);
 962         if (ret)
 963                 goto out;
 964
 965         __merge_refs(&prefs, 2);
 966
 967         while (!list_empty(&prefs)) {
 968                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
 969                 WARN_ON(ref->count < 0);
 970                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
 971                         /* no parent == root of tree */
 972                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
 973                         if (ret < 0)
 974                                 goto out;
 975                 }
 976                 if (ref->count && ref->parent) {
 977                         if (extent_item_pos && !ref->inode_list) {
 978                                 u32 bsz;
 979                                 struct extent_buffer *eb;
 980                                 bsz = btrfs_level_size(fs_info->extent_root,
 981                                                         info_level);
 982                                 eb = read_tree_block(fs_info->extent_root,
 983                                                            ref->parent, bsz, 0);
 984                                 if (!eb || !extent_buffer_uptodate(eb)) {
 985                                         free_extent_buffer(eb);
 986                                         ret = -EIO;
 987                                         goto out;
 988                                 }
 989                                 ret = find_extent_in_eb(eb, bytenr,
 990                                                         *extent_item_pos, &eie);
 991                                 free_extent_buffer(eb);
 992                                 if (ret < 0)
 993                                         goto out;
 994                                 ref->inode_list = eie;
 995                         }
 996                         ret = ulist_add_merge(refs, ref->parent,
 997                                               (uintptr_t)ref->inode_list,
 998                                               (u64 *)&eie, GFP_NOFS);
 999                         if (ret < 0)
1000                                 goto out;
1001                         if (!ret && extent_item_pos) {
1002                                 /*
1003                                  * we've recorded that parent, so we must extend
1004                                  * its inode list here
1005                                  */
1006                                 BUG_ON(!eie);
1007                                 while (eie->next)
1008                                         eie = eie->next;
1009                                 eie->next = ref->inode_list;
1010                         }
1011                         eie = NULL;
1012                 }
1013                 list_del(&ref->list);
1014                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1015         }
1016
1017 out:
1018         btrfs_free_path(path);
1019         while (!list_empty(&prefs)) {
1020                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
1021                 list_del(&ref->list);
1022                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1023         }
1024         while (!list_empty(&prefs_delayed)) {
1025                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
1026                                        list);
1027                 list_del(&ref->list);
1028                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1029         }
1030         if (ret < 0)
1031                 free_inode_elem_list(eie);
1032         return ret;
1033 }
1034
1035 static void free_leaf_list(struct ulist *blocks)
1036 {
1037         struct ulist_node *node = NULL;
1038         struct extent_inode_elem *eie;
1039         struct ulist_iterator uiter;
1040
1041         ULIST_ITER_INIT(&uiter);
1042         while ((node = ulist_next(blocks, &uiter))) {
1043                 if (!node->aux)
1044                         continue;
1045                 eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
1046                 free_inode_elem_list(eie);
1047                 node->aux = 0;
1048         }
1049
1050         ulist_free(blocks);
1051 }
1052
1053 /*
1054  * Finds all leafs with a reference to the specified combination of bytenr and
1055  * offset. key_list_head will point to a list of corresponding keys (caller must
1056  * free each list element). The leafs will be stored in the leafs ulist, which
1057  * must be freed with ulist_free.
1058  *
1059  * returns 0 on success, <0 on error
1060  */
1061 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1062                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1063                                 u64 time_seq, struct ulist **leafs,
1064                                 const u64 *extent_item_pos)
1065 {
1066         int ret;
1067
1068         *leafs = ulist_alloc(GFP_NOFS);
1069         if (!*leafs)
1070                 return -ENOMEM;
1071
1072         ret = find_parent_nodes(trans, fs_info, bytenr,
1073                                 time_seq, *leafs, NULL, extent_item_pos);
1074         if (ret < 0 && ret != -ENOENT) {
1075                 free_leaf_list(*leafs);
1076                 return ret;
1077         }
1078
1079         return 0;
1080 }
1081
1082 /*
1083  * walk all backrefs for a given extent to find all roots that reference this
1084  * extent. Walking a backref means finding all extents that reference this
1085  * extent and in turn walk the backrefs of those, too. Naturally this is a
1086  * recursive process, but here it is implemented in an iterative fashion: We
1087  * find all referencing extents for the extent in question and put them on a
1088  * list. In turn, we find all referencing extents for those, further appending
1089  * to the list. The way we iterate the list allows adding more elements after
1090  * the current while iterating. The process stops when we reach the end of the
1091  * list. Found roots are added to the roots list.
1092  *
1093  * returns 0 on success, < 0 on error.
1094  */
1095 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1096                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1097                                 u64 time_seq, struct ulist **roots)
1098 {
1099         struct ulist *tmp;
1100         struct ulist_node *node = NULL;
1101         struct ulist_iterator uiter;
1102         int ret;
1103
1104         tmp = ulist_alloc(GFP_NOFS);
1105         if (!tmp)
1106                 return -ENOMEM;
1107         *roots = ulist_alloc(GFP_NOFS);
1108         if (!*roots) {
1109                 ulist_free(tmp);
1110                 return -ENOMEM;
1111         }
1112
1113         ULIST_ITER_INIT(&uiter);
1114         while (1) {
1115                 ret = find_parent_nodes(trans, fs_info, bytenr,
1116                                         time_seq, tmp, *roots, NULL);
1117                 if (ret < 0 && ret != -ENOENT) {
1118                         ulist_free(tmp);
1119                         ulist_free(*roots);
1120                         return ret;
1121                 }
1122                 node = ulist_next(tmp, &uiter);
1123                 if (!node)
1124                         break;
1125                 bytenr = node->val;
1126                 cond_resched();
1127         }
1128
1129         ulist_free(tmp);
1130         return 0;
1131 }
1132
1133 /*
1134  * this makes the path point to (inum INODE_ITEM ioff)
1135  */
1136 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1137                         struct btrfs_path *path)
1138 {
1139         struct btrfs_key key;
1140         return btrfs_find_item(fs_root, path, inum, ioff,
1141                         BTRFS_INODE_ITEM_KEY, &key);
1142 }
1143
1144 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1145                                 struct btrfs_path *path,
1146                                 struct btrfs_key *found_key)
1147 {
1148         return btrfs_find_item(fs_root, path, inum, ioff,
1149                         BTRFS_INODE_REF_KEY, found_key);
1150 }
1151
1152 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1153                           u64 start_off, struct btrfs_path *path,
1154                           struct btrfs_inode_extref **ret_extref,
1155                           u64 *found_off)
1156 {
1157         int ret, slot;
1158         struct btrfs_key key;
1159         struct btrfs_key found_key;
1160         struct btrfs_inode_extref *extref;
1161         struct extent_buffer *leaf;
1162         unsigned long ptr;
1163
1164         key.objectid = inode_objectid;
1165         btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
1166         key.offset = start_off;
1167
1168         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1169         if (ret < 0)
1170                 return ret;
1171
1172         while (1) {
1173                 leaf = path->nodes[0];
1174                 slot = path->slots[0];
1175                 if (slot >= btrfs_header_nritems(leaf)) {
1176                         /*
1177                          * If the item at offset is not found,
1178                          * btrfs_search_slot will point us to the slot
1179                          * where it should be inserted. In our case
1180                          * that will be the slot directly before the
1181                          * next INODE_REF_KEY_V2 item. In the case
1182                          * that we're pointing to the last slot in a
1183                          * leaf, we must move one leaf over.
1184                          */
1185                         ret = btrfs_next_leaf(root, path);
1186                         if (ret) {
1187                                 if (ret >= 1)
1188                                         ret = -ENOENT;
1189                                 break;
1190                         }
1191                         continue;
1192                 }
1193
1194                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1195
1196                 /*
1197                  * Check that we're still looking at an extended ref key for
1198                  * this particular objectid. If we have different
1199                  * objectid or type then there are no more to be found
1200                  * in the tree and we can exit.
1201                  */
1202                 ret = -ENOENT;
1203                 if (found_key.objectid != inode_objectid)
1204                         break;
1205                 if (btrfs_key_type(&found_key) != BTRFS_INODE_EXTREF_KEY)
1206                         break;
1207
1208                 ret = 0;
1209                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1210                 extref = (struct btrfs_inode_extref *)ptr;
1211                 *ret_extref = extref;
1212                 if (found_off)
1213                         *found_off = found_key.offset;
1214                 break;
1215         }
1216
1217         return ret;
1218 }
1219
1220 /*
1221  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1222  * Elements of the path are separated by '/' and the path is guaranteed to be
1223  * 0-terminated. the path is only given within the current file system.
1224  * Therefore, it never starts with a '/'. the caller is responsible to provide
1225  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1226  * the start point of the resulting string is returned. this pointer is within
1227  * dest, normally.
1228  * in case the path buffer would overflow, the pointer is decremented further
1229  * as if output was written to the buffer, though no more output is actually
1230  * generated. that way, the caller can determine how much space would be
1231  * required for the path to fit into the buffer. in that case, the returned
1232  * value will be smaller than dest. callers must check this!
1233  */
1234 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1235                         u32 name_len, unsigned long name_off,
1236                         struct extent_buffer *eb_in, u64 parent,
1237                         char *dest, u32 size)
1238 {
1239         int slot;
1240         u64 next_inum;
1241         int ret;
1242         s64 bytes_left = ((s64)size) - 1;
1243         struct extent_buffer *eb = eb_in;
1244         struct btrfs_key found_key;
1245         int leave_spinning = path->leave_spinning;
1246         struct btrfs_inode_ref *iref;
1247
1248         if (bytes_left >= 0)
1249                 dest[bytes_left] = '\0';
1250
1251         path->leave_spinning = 1;
1252         while (1) {
1253                 bytes_left -= name_len;
1254                 if (bytes_left >= 0)
1255                         read_extent_buffer(eb, dest + bytes_left,
1256                                            name_off, name_len);
1257                 if (eb != eb_in) {
1258                         btrfs_tree_read_unlock_blocking(eb);
1259                         free_extent_buffer(eb);
1260                 }
1261                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1262                 if (ret > 0)
1263                         ret = -ENOENT;
1264                 if (ret)
1265                         break;
1266
1267                 next_inum = found_key.offset;
1268
1269                 /* regular exit ahead */
1270                 if (parent == next_inum)
1271                         break;
1272
1273                 slot = path->slots[0];
1274                 eb = path->nodes[0];
1275                 /* make sure we can use eb after releasing the path */
1276                 if (eb != eb_in) {
1277                         atomic_inc(&eb->refs);
1278                         btrfs_tree_read_lock(eb);
1279                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1280                 }
1281                 btrfs_release_path(path);
1282                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1283
1284                 name_len = btrfs_inode_ref_name_len(eb, iref);
1285                 name_off = (unsigned long)(iref + 1);
1286
1287                 parent = next_inum;
1288                 --bytes_left;
1289                 if (bytes_left >= 0)
1290                         dest[bytes_left] = '/';
1291         }
1292
1293         btrfs_release_path(path);
1294         path->leave_spinning = leave_spinning;
1295
1296         if (ret)
1297                 return ERR_PTR(ret);
1298
1299         return dest + bytes_left;
1300 }
1301
1302 /*
1303  * this makes the path point to (logical EXTENT_ITEM *)
1304  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1305  * tree blocks and <0 on error.
1306  */
1307 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1308                         struct btrfs_path *path, struct btrfs_key *found_key,
1309                         u64 *flags_ret)
1310 {
1311         int ret;
1312         u64 flags;
1313         u64 size = 0;
1314         u32 item_size;
1315         struct extent_buffer *eb;
1316         struct btrfs_extent_item *ei;
1317         struct btrfs_key key;
1318
1319         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1320                 key.type = BTRFS_METADATA_ITEM_KEY;
1321         else
1322                 key.type = BTRFS_EXTENT_ITEM_KEY;
1323         key.objectid = logical;
1324         key.offset = (u64)-1;
1325
1326         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1327         if (ret < 0)
1328                 return ret;
1329
1330         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1331         if (ret) {
1332                 if (ret > 0)
1333                         ret = -ENOENT;
1334                 return ret;
1335         }
1336         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1337         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1338                 size = fs_info->extent_root->leafsize;
1339         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1340                 size = found_key->offset;
1341
1342         if (found_key->objectid > logical ||
1343             found_key->objectid + size <= logical) {
1344                 pr_debug("logical %llu is not within any extent\n", logical);
1345                 return -ENOENT;
1346         }
1347
1348         eb = path->nodes[0];
1349         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1350         BUG_ON(item_size < sizeof(*ei));
1351
1352         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1353         flags = btrfs_extent_flags(eb, ei);
1354
1355         pr_debug("logical %llu is at position %llu within the extent (%llu "
1356                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1357                  logical, logical - found_key->objectid, found_key->objectid,
1358                  found_key->offset, flags, item_size);
1359
1360         WARN_ON(!flags_ret);
1361         if (flags_ret) {
1362                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1363                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1364                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1365                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1366                 else
1367                         BUG_ON(1);
1368                 return 0;
1369         }
1370
1371         return -EIO;
1372 }
1373
1374 /*
1375  * helper function to iterate extent inline refs. ptr must point to a 0 value
1376  * for the first call and may be modified. it is used to track state.
1377  * if more refs exist, 0 is returned and the next call to
1378  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1379  * next ref. after the last ref was processed, 1 is returned.
1380  * returns <0 on error
1381  */
1382 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1383                                 struct btrfs_extent_item *ei, u32 item_size,
1384                                 struct btrfs_extent_inline_ref **out_eiref,
1385                                 int *out_type)
1386 {
1387         unsigned long end;
1388         u64 flags;
1389         struct btrfs_tree_block_info *info;
1390
1391         if (!*ptr) {
1392                 /* first call */
1393                 flags = btrfs_extent_flags(eb, ei);
1394                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1395                         info = (struct btrfs_tree_block_info *)(ei + 1);
1396                         *out_eiref =
1397                                 (struct btrfs_extent_inline_ref *)(info + 1);
1398                 } else {
1399                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1400                 }
1401                 *ptr = (unsigned long)*out_eiref;
1402                 if ((void *)*ptr >= (void *)ei + item_size)
1403                         return -ENOENT;
1404         }
1405
1406         end = (unsigned long)ei + item_size;
1407         *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
1408         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1409
1410         *ptr += btrfs_extent_inline_ref_size(*out_type);
1411         WARN_ON(*ptr > end);
1412         if (*ptr == end)
1413                 return 1; /* last */
1414
1415         return 0;
1416 }
1417
1418 /*
1419  * reads the tree block backref for an extent. tree level and root are returned
1420  * through out_level and out_root. ptr must point to a 0 value for the first
1421  * call and may be modified (see __get_extent_inline_ref comment).
1422  * returns 0 if data was provided, 1 if there was no more data to provide or
1423  * <0 on error.
1424  */
1425 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1426                                 struct btrfs_extent_item *ei, u32 item_size,
1427                                 u64 *out_root, u8 *out_level)
1428 {
1429         int ret;
1430         int type;
1431         struct btrfs_tree_block_info *info;
1432         struct btrfs_extent_inline_ref *eiref;
1433
1434         if (*ptr == (unsigned long)-1)
1435                 return 1;
1436
1437         while (1) {
1438                 ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
1439                                                 &eiref, &type);
1440                 if (ret < 0)
1441                         return ret;
1442
1443                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1444                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1445                         break;
1446
1447                 if (ret == 1)
1448                         return 1;
1449         }
1450
1451         /* we can treat both ref types equally here */
1452         info = (struct btrfs_tree_block_info *)(ei + 1);
1453         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1454         *out_level = btrfs_tree_block_level(eb, info);
1455
1456         if (ret == 1)
1457                 *ptr = (unsigned long)-1;
1458
1459         return 0;
1460 }
1461
1462 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1463                                 u64 root, u64 extent_item_objectid,
1464                                 iterate_extent_inodes_t *iterate, void *ctx)
1465 {
1466         struct extent_inode_elem *eie;
1467         int ret = 0;
1468
1469         for (eie = inode_list; eie; eie = eie->next) {
1470                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1471                          "root %llu\n", extent_item_objectid,
1472                          eie->inum, eie->offset, root);
1473                 ret = iterate(eie->inum, eie->offset, root, ctx);
1474                 if (ret) {
1475                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1476                                  extent_item_objectid, ret);
1477                         break;
1478                 }
1479         }
1480
1481         return ret;
1482 }
1483
1484 /*
1485  * calls iterate() for every inode that references the extent identified by
1486  * the given parameters.
1487  * when the iterator function returns a non-zero value, iteration stops.
1488  */
1489 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1490                                 u64 extent_item_objectid, u64 extent_item_pos,
1491                                 int search_commit_root,
1492                                 iterate_extent_inodes_t *iterate, void *ctx)
1493 {
1494         int ret;
1495         struct btrfs_trans_handle *trans = NULL;
1496         struct ulist *refs = NULL;
1497         struct ulist *roots = NULL;
1498         struct ulist_node *ref_node = NULL;
1499         struct ulist_node *root_node = NULL;
1500         struct seq_list tree_mod_seq_elem = {};
1501         struct ulist_iterator ref_uiter;
1502         struct ulist_iterator root_uiter;
1503
1504         pr_debug("resolving all inodes for extent %llu\n",
1505                         extent_item_objectid);
1506
1507         if (!search_commit_root) {
1508                 trans = btrfs_join_transaction(fs_info->extent_root);
1509                 if (IS_ERR(trans))
1510                         return PTR_ERR(trans);
1511                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1512         }
1513
1514         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1515                                    tree_mod_seq_elem.seq, &refs,
1516                                    &extent_item_pos);
1517         if (ret)
1518                 goto out;
1519
1520         ULIST_ITER_INIT(&ref_uiter);
1521         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1522                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1523                                            tree_mod_seq_elem.seq, &roots);
1524                 if (ret)
1525                         break;
1526                 ULIST_ITER_INIT(&root_uiter);
1527                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1528                         pr_debug("root %llu references leaf %llu, data list "
1529                                  "%#llx\n", root_node->val, ref_node->val,
1530                                  ref_node->aux);
1531                         ret = iterate_leaf_refs((struct extent_inode_elem *)
1532                                                 (uintptr_t)ref_node->aux,
1533                                                 root_node->val,
1534                                                 extent_item_objectid,
1535                                                 iterate, ctx);
1536                 }
1537                 ulist_free(roots);
1538         }
1539
1540         free_leaf_list(refs);
1541 out:
1542         if (!search_commit_root) {
1543                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1544                 btrfs_end_transaction(trans, fs_info->extent_root);
1545         }
1546
1547         return ret;
1548 }
1549
1550 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1551                                 struct btrfs_path *path,
1552                                 iterate_extent_inodes_t *iterate, void *ctx)
1553 {
1554         int ret;
1555         u64 extent_item_pos;
1556         u64 flags = 0;
1557         struct btrfs_key found_key;
1558         int search_commit_root = path->search_commit_root;
1559
1560         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1561         btrfs_release_path(path);
1562         if (ret < 0)
1563                 return ret;
1564         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1565                 return -EINVAL;
1566
1567         extent_item_pos = logical - found_key.objectid;
1568         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1569                                         extent_item_pos, search_commit_root,
1570                                         iterate, ctx);
1571
1572         return ret;
1573 }
1574
1575 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1576                               struct extent_buffer *eb, void *ctx);
1577
1578 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1579                               struct btrfs_path *path,
1580                               iterate_irefs_t *iterate, void *ctx)
1581 {
1582         int ret = 0;
1583         int slot;
1584         u32 cur;
1585         u32 len;
1586         u32 name_len;
1587         u64 parent = 0;
1588         int found = 0;
1589         struct extent_buffer *eb;
1590         struct btrfs_item *item;
1591         struct btrfs_inode_ref *iref;
1592         struct btrfs_key found_key;
1593
1594         while (!ret) {
1595                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1596                                      &found_key);
1597                 if (ret < 0)
1598                         break;
1599                 if (ret) {
1600                         ret = found ? 0 : -ENOENT;
1601                         break;
1602                 }
1603                 ++found;
1604
1605                 parent = found_key.offset;
1606                 slot = path->slots[0];
1607                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1608                 if (!eb) {
1609                         ret = -ENOMEM;
1610                         break;
1611                 }
1612                 extent_buffer_get(eb);
1613                 btrfs_tree_read_lock(eb);
1614                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1615                 btrfs_release_path(path);
1616
1617                 item = btrfs_item_nr(slot);
1618                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1619
1620                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1621                         name_len = btrfs_inode_ref_name_len(eb, iref);
1622                         /* path must be released before calling iterate()! */
1623                         pr_debug("following ref at offset %u for inode %llu in "
1624                                  "tree %llu\n", cur, found_key.objectid,
1625                                  fs_root->objectid);
1626                         ret = iterate(parent, name_len,
1627                                       (unsigned long)(iref + 1), eb, ctx);
1628                         if (ret)
1629                                 break;
1630                         len = sizeof(*iref) + name_len;
1631                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1632                 }
1633                 btrfs_tree_read_unlock_blocking(eb);
1634                 free_extent_buffer(eb);
1635         }
1636
1637         btrfs_release_path(path);
1638
1639         return ret;
1640 }
1641
1642 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1643                                  struct btrfs_path *path,
1644                                  iterate_irefs_t *iterate, void *ctx)
1645 {
1646         int ret;
1647         int slot;
1648         u64 offset = 0;
1649         u64 parent;
1650         int found = 0;
1651         struct extent_buffer *eb;
1652         struct btrfs_inode_extref *extref;
1653         struct extent_buffer *leaf;
1654         u32 item_size;
1655         u32 cur_offset;
1656         unsigned long ptr;
1657
1658         while (1) {
1659                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1660                                             &offset);
1661                 if (ret < 0)
1662                         break;
1663                 if (ret) {
1664                         ret = found ? 0 : -ENOENT;
1665                         break;
1666                 }
1667                 ++found;
1668
1669                 slot = path->slots[0];
1670                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1671                 if (!eb) {
1672                         ret = -ENOMEM;
1673                         break;
1674                 }
1675                 extent_buffer_get(eb);
1676
1677                 btrfs_tree_read_lock(eb);
1678                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1679                 btrfs_release_path(path);
1680
1681                 leaf = path->nodes[0];
1682                 item_size = btrfs_item_size_nr(leaf, slot);
1683                 ptr = btrfs_item_ptr_offset(leaf, slot);
1684                 cur_offset = 0;
1685
1686                 while (cur_offset < item_size) {
1687                         u32 name_len;
1688
1689                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1690                         parent = btrfs_inode_extref_parent(eb, extref);
1691                         name_len = btrfs_inode_extref_name_len(eb, extref);
1692                         ret = iterate(parent, name_len,
1693                                       (unsigned long)&extref->name, eb, ctx);
1694                         if (ret)
1695                                 break;
1696
1697                         cur_offset += btrfs_inode_extref_name_len(leaf, extref);
1698                         cur_offset += sizeof(*extref);
1699                 }
1700                 btrfs_tree_read_unlock_blocking(eb);
1701                 free_extent_buffer(eb);
1702
1703                 offset++;
1704         }
1705
1706         btrfs_release_path(path);
1707
1708         return ret;
1709 }
1710
1711 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1712                          struct btrfs_path *path, iterate_irefs_t *iterate,
1713                          void *ctx)
1714 {
1715         int ret;
1716         int found_refs = 0;
1717
1718         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1719         if (!ret)
1720                 ++found_refs;
1721         else if (ret != -ENOENT)
1722                 return ret;
1723
1724         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1725         if (ret == -ENOENT && found_refs)
1726                 return 0;
1727
1728         return ret;
1729 }
1730
1731 /*
1732  * returns 0 if the path could be dumped (probably truncated)
1733  * returns <0 in case of an error
1734  */
1735 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1736                          struct extent_buffer *eb, void *ctx)
1737 {
1738         struct inode_fs_paths *ipath = ctx;
1739         char *fspath;
1740         char *fspath_min;
1741         int i = ipath->fspath->elem_cnt;
1742         const int s_ptr = sizeof(char *);
1743         u32 bytes_left;
1744
1745         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1746                                         ipath->fspath->bytes_left - s_ptr : 0;
1747
1748         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1749         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1750                                    name_off, eb, inum, fspath_min, bytes_left);
1751         if (IS_ERR(fspath))
1752                 return PTR_ERR(fspath);
1753
1754         if (fspath > fspath_min) {
1755                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1756                 ++ipath->fspath->elem_cnt;
1757                 ipath->fspath->bytes_left = fspath - fspath_min;
1758         } else {
1759                 ++ipath->fspath->elem_missed;
1760                 ipath->fspath->bytes_missing += fspath_min - fspath;
1761                 ipath->fspath->bytes_left = 0;
1762         }
1763
1764         return 0;
1765 }
1766
1767 /*
1768  * this dumps all file system paths to the inode into the ipath struct, provided
1769  * is has been created large enough. each path is zero-terminated and accessed
1770  * from ipath->fspath->val[i].
1771  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1772  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1773  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1774  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1775  * have been needed to return all paths.
1776  */
1777 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1778 {
1779         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1780                              inode_to_path, ipath);
1781 }
1782
1783 struct btrfs_data_container *init_data_container(u32 total_bytes)
1784 {
1785         struct btrfs_data_container *data;
1786         size_t alloc_bytes;
1787
1788         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1789         data = vmalloc(alloc_bytes);
1790         if (!data)
1791                 return ERR_PTR(-ENOMEM);
1792
1793         if (total_bytes >= sizeof(*data)) {
1794                 data->bytes_left = total_bytes - sizeof(*data);
1795                 data->bytes_missing = 0;
1796         } else {
1797                 data->bytes_missing = sizeof(*data) - total_bytes;
1798                 data->bytes_left = 0;
1799         }
1800
1801         data->elem_cnt = 0;
1802         data->elem_missed = 0;
1803
1804         return data;
1805 }
1806
1807 /*
1808  * allocates space to return multiple file system paths for an inode.
1809  * total_bytes to allocate are passed, note that space usable for actual path
1810  * information will be total_bytes - sizeof(struct inode_fs_paths).
1811  * the returned pointer must be freed with free_ipath() in the end.
1812  */
1813 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1814                                         struct btrfs_path *path)
1815 {
1816         struct inode_fs_paths *ifp;
1817         struct btrfs_data_container *fspath;
1818
1819         fspath = init_data_container(total_bytes);
1820         if (IS_ERR(fspath))
1821                 return (void *)fspath;
1822
1823         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1824         if (!ifp) {
1825                 kfree(fspath);
1826                 return ERR_PTR(-ENOMEM);
1827         }
1828
1829         ifp->btrfs_path = path;
1830         ifp->fspath = fspath;
1831         ifp->fs_root = fs_root;
1832
1833         return ifp;
1834 }
1835
1836 void free_ipath(struct inode_fs_paths *ipath)
1837 {
1838         if (!ipath)
1839                 return;
1840         vfree(ipath->fspath);
1841         kfree(ipath);
1842 }