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 /* Just an arbitrary number so we can be sure this happened */
  29 #define BACKREF_FOUND_SHARED 6
  30
  31 struct extent_inode_elem {
  32         u64 inum;
  33         u64 offset;
  34         struct extent_inode_elem *next;
  35 };
  36
  37 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
  38                                 struct btrfs_file_extent_item *fi,
  39                                 u64 extent_item_pos,
  40                                 struct extent_inode_elem **eie)
  41 {
  42         u64 offset = 0;
  43         struct extent_inode_elem *e;
  44
  45         if (!btrfs_file_extent_compression(eb, fi) &&
  46             !btrfs_file_extent_encryption(eb, fi) &&
  47             !btrfs_file_extent_other_encoding(eb, fi)) {
  48                 u64 data_offset;
  49                 u64 data_len;
  50
  51                 data_offset = btrfs_file_extent_offset(eb, fi);
  52                 data_len = btrfs_file_extent_num_bytes(eb, fi);
  53
  54                 if (extent_item_pos < data_offset ||
  55                     extent_item_pos >= data_offset + data_len)
  56                         return 1;
  57                 offset = extent_item_pos - data_offset;
  58         }
  59
  60         e = kmalloc(sizeof(*e), GFP_NOFS);
  61         if (!e)
  62                 return -ENOMEM;
  63
  64         e->next = *eie;
  65         e->inum = key->objectid;
  66         e->offset = key->offset + offset;
  67         *eie = e;
  68
  69         return 0;
  70 }
  71
  72 static void free_inode_elem_list(struct extent_inode_elem *eie)
  73 {
  74         struct extent_inode_elem *eie_next;
  75
  76         for (; eie; eie = eie_next) {
  77                 eie_next = eie->next;
  78                 kfree(eie);
  79         }
  80 }
  81
  82 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
  83                                 u64 extent_item_pos,
  84                                 struct extent_inode_elem **eie)
  85 {
  86         u64 disk_byte;
  87         struct btrfs_key key;
  88         struct btrfs_file_extent_item *fi;
  89         int slot;
  90         int nritems;
  91         int extent_type;
  92         int ret;
  93
  94         /*
  95          * from the shared data ref, we only have the leaf but we need
  96          * the key. thus, we must look into all items and see that we
  97          * find one (some) with a reference to our extent item.
  98          */
  99         nritems = btrfs_header_nritems(eb);
 100         for (slot = 0; slot < nritems; ++slot) {
 101                 btrfs_item_key_to_cpu(eb, &key, slot);
 102                 if (key.type != BTRFS_EXTENT_DATA_KEY)
 103                         continue;
 104                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 105                 extent_type = btrfs_file_extent_type(eb, fi);
 106                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
 107                         continue;
 108                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
 109                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 110                 if (disk_byte != wanted_disk_byte)
 111                         continue;
 112
 113                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
 114                 if (ret < 0)
 115                         return ret;
 116         }
 117
 118         return 0;
 119 }
 120
 121 /*
 122  * this structure records all encountered refs on the way up to the root
 123  */
 124 struct __prelim_ref {
 125         struct list_head list;
 126         u64 root_id;
 127         struct btrfs_key key_for_search;
 128         int level;
 129         int count;
 130         struct extent_inode_elem *inode_list;
 131         u64 parent;
 132         u64 wanted_disk_byte;
 133 };
 134
 135 static struct kmem_cache *btrfs_prelim_ref_cache;
 136
 137 int __init btrfs_prelim_ref_init(void)
 138 {
 139         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
 140                                         sizeof(struct __prelim_ref),
 141                                         0,
 142                                         SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 143                                         NULL);
 144         if (!btrfs_prelim_ref_cache)
 145                 return -ENOMEM;
 146         return 0;
 147 }
 148
 149 void btrfs_prelim_ref_exit(void)
 150 {
 151         if (btrfs_prelim_ref_cache)
 152                 kmem_cache_destroy(btrfs_prelim_ref_cache);
 153 }
 154
 155 /*
 156  * the rules for all callers of this function are:
 157  * - obtaining the parent is the goal
 158  * - if you add a key, you must know that it is a correct key
 159  * - if you cannot add the parent or a correct key, then we will look into the
 160  *   block later to set a correct key
 161  *
 162  * delayed refs
 163  * ============
 164  *        backref type | shared | indirect | shared | indirect
 165  * information         |   tree |     tree |   data |     data
 166  * --------------------+--------+----------+--------+----------
 167  *      parent logical |    y   |     -    |    -   |     -
 168  *      key to resolve |    -   |     y    |    y   |     y
 169  *  tree block logical |    -   |     -    |    -   |     -
 170  *  root for resolving |    y   |     y    |    y   |     y
 171  *
 172  * - column 1:       we've the parent -> done
 173  * - column 2, 3, 4: we use the key to find the parent
 174  *
 175  * on disk refs (inline or keyed)
 176  * ==============================
 177  *        backref type | shared | indirect | shared | indirect
 178  * information         |   tree |     tree |   data |     data
 179  * --------------------+--------+----------+--------+----------
 180  *      parent logical |    y   |     -    |    y   |     -
 181  *      key to resolve |    -   |     -    |    -   |     y
 182  *  tree block logical |    y   |     y    |    y   |     y
 183  *  root for resolving |    -   |     y    |    y   |     y
 184  *
 185  * - column 1, 3: we've the parent -> done
 186  * - column 2:    we take the first key from the block to find the parent
 187  *                (see __add_missing_keys)
 188  * - column 4:    we use the key to find the parent
 189  *
 190  * additional information that's available but not required to find the parent
 191  * block might help in merging entries to gain some speed.
 192  */
 193
 194 static int __add_prelim_ref(struct list_head *head, u64 root_id,
 195                             struct btrfs_key *key, int level,
 196                             u64 parent, u64 wanted_disk_byte, int count,
 197                             gfp_t gfp_mask)
 198 {
 199         struct __prelim_ref *ref;
 200
 201         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
 202                 return 0;
 203
 204         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
 205         if (!ref)
 206                 return -ENOMEM;
 207
 208         ref->root_id = root_id;
 209         if (key)
 210                 ref->key_for_search = *key;
 211         else
 212                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
 213
 214         ref->inode_list = NULL;
 215         ref->level = level;
 216         ref->count = count;
 217         ref->parent = parent;
 218         ref->wanted_disk_byte = wanted_disk_byte;
 219         list_add_tail(&ref->list, head);
 220
 221         return 0;
 222 }
 223
 224 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
 225                            struct ulist *parents, struct __prelim_ref *ref,
 226                            int level, u64 time_seq, const u64 *extent_item_pos,
 227                            u64 total_refs)
 228 {
 229         int ret = 0;
 230         int slot;
 231         struct extent_buffer *eb;
 232         struct btrfs_key key;
 233         struct btrfs_key *key_for_search = &ref->key_for_search;
 234         struct btrfs_file_extent_item *fi;
 235         struct extent_inode_elem *eie = NULL, *old = NULL;
 236         u64 disk_byte;
 237         u64 wanted_disk_byte = ref->wanted_disk_byte;
 238         u64 count = 0;
 239
 240         if (level != 0) {
 241                 eb = path->nodes[level];
 242                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
 243                 if (ret < 0)
 244                         return ret;
 245                 return 0;
 246         }
 247
 248         /*
 249          * We normally enter this function with the path already pointing to
 250          * the first item to check. But sometimes, we may enter it with
 251          * slot==nritems. In that case, go to the next leaf before we continue.
 252          */
 253         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
 254                 ret = btrfs_next_old_leaf(root, path, time_seq);
 255
 256         while (!ret && count < total_refs) {
 257                 eb = path->nodes[0];
 258                 slot = path->slots[0];
 259
 260                 btrfs_item_key_to_cpu(eb, &key, slot);
 261
 262                 if (key.objectid != key_for_search->objectid ||
 263                     key.type != BTRFS_EXTENT_DATA_KEY)
 264                         break;
 265
 266                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 267                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 268
 269                 if (disk_byte == wanted_disk_byte) {
 270                         eie = NULL;
 271                         old = NULL;
 272                         count++;
 273                         if (extent_item_pos) {
 274                                 ret = check_extent_in_eb(&key, eb, fi,
 275                                                 *extent_item_pos,
 276                                                 &eie);
 277                                 if (ret < 0)
 278                                         break;
 279                         }
 280                         if (ret > 0)
 281                                 goto next;
 282                         ret = ulist_add_merge_ptr(parents, eb->start,
 283                                                   eie, (void **)&old, GFP_NOFS);
 284                         if (ret < 0)
 285                                 break;
 286                         if (!ret && extent_item_pos) {
 287                                 while (old->next)
 288                                         old = old->next;
 289                                 old->next = eie;
 290                         }
 291                         eie = NULL;
 292                 }
 293 next:
 294                 ret = btrfs_next_old_item(root, path, time_seq);
 295         }
 296
 297         if (ret > 0)
 298                 ret = 0;
 299         else if (ret < 0)
 300                 free_inode_elem_list(eie);
 301         return ret;
 302 }
 303
 304 /*
 305  * resolve an indirect backref in the form (root_id, key, level)
 306  * to a logical address
 307  */
 308 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 309                                   struct btrfs_path *path, u64 time_seq,
 310                                   struct __prelim_ref *ref,
 311                                   struct ulist *parents,
 312                                   const u64 *extent_item_pos, u64 total_refs)
 313 {
 314         struct btrfs_root *root;
 315         struct btrfs_key root_key;
 316         struct extent_buffer *eb;
 317         int ret = 0;
 318         int root_level;
 319         int level = ref->level;
 320         int index;
 321
 322         root_key.objectid = ref->root_id;
 323         root_key.type = BTRFS_ROOT_ITEM_KEY;
 324         root_key.offset = (u64)-1;
 325
 326         index = srcu_read_lock(&fs_info->subvol_srcu);
 327
 328         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
 329         if (IS_ERR(root)) {
 330                 srcu_read_unlock(&fs_info->subvol_srcu, index);
 331                 ret = PTR_ERR(root);
 332                 goto out;
 333         }
 334
 335         if (path->search_commit_root)
 336                 root_level = btrfs_header_level(root->commit_root);
 337         else
 338                 root_level = btrfs_old_root_level(root, time_seq);
 339
 340         if (root_level + 1 == level) {
 341                 srcu_read_unlock(&fs_info->subvol_srcu, index);
 342                 goto out;
 343         }
 344
 345         path->lowest_level = level;
 346         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
 347
 348         /* root node has been locked, we can release @subvol_srcu safely here */
 349         srcu_read_unlock(&fs_info->subvol_srcu, index);
 350
 351         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
 352                  "%d for key (%llu %u %llu)\n",
 353                  ref->root_id, level, ref->count, ret,
 354                  ref->key_for_search.objectid, ref->key_for_search.type,
 355                  ref->key_for_search.offset);
 356         if (ret < 0)
 357                 goto out;
 358
 359         eb = path->nodes[level];
 360         while (!eb) {
 361                 if (WARN_ON(!level)) {
 362                         ret = 1;
 363                         goto out;
 364                 }
 365                 level--;
 366                 eb = path->nodes[level];
 367         }
 368
 369         ret = add_all_parents(root, path, parents, ref, level, time_seq,
 370                               extent_item_pos, total_refs);
 371 out:
 372         path->lowest_level = 0;
 373         btrfs_release_path(path);
 374         return ret;
 375 }
 376
 377 /*
 378  * resolve all indirect backrefs from the list
 379  */
 380 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 381                                    struct btrfs_path *path, u64 time_seq,
 382                                    struct list_head *head,
 383                                    const u64 *extent_item_pos, u64 total_refs,
 384                                    u64 root_objectid)
 385 {
 386         int err;
 387         int ret = 0;
 388         struct __prelim_ref *ref;
 389         struct __prelim_ref *ref_safe;
 390         struct __prelim_ref *new_ref;
 391         struct ulist *parents;
 392         struct ulist_node *node;
 393         struct ulist_iterator uiter;
 394
 395         parents = ulist_alloc(GFP_NOFS);
 396         if (!parents)
 397                 return -ENOMEM;
 398
 399         /*
 400          * _safe allows us to insert directly after the current item without
 401          * iterating over the newly inserted items.
 402          * we're also allowed to re-assign ref during iteration.
 403          */
 404         list_for_each_entry_safe(ref, ref_safe, head, list) {
 405                 if (ref->parent)        /* already direct */
 406                         continue;
 407                 if (ref->count == 0)
 408                         continue;
 409                 if (root_objectid && ref->root_id != root_objectid) {
 410                         ret = BACKREF_FOUND_SHARED;
 411                         goto out;
 412                 }
 413                 err = __resolve_indirect_ref(fs_info, path, time_seq, ref,
 414                                              parents, extent_item_pos,
 415                                              total_refs);
 416                 /*
 417                  * we can only tolerate ENOENT,otherwise,we should catch error
 418                  * and return directly.
 419                  */
 420                 if (err == -ENOENT) {
 421                         continue;
 422                 } else if (err) {
 423                         ret = err;
 424                         goto out;
 425                 }
 426
 427                 /* we put the first parent into the ref at hand */
 428                 ULIST_ITER_INIT(&uiter);
 429                 node = ulist_next(parents, &uiter);
 430                 ref->parent = node ? node->val : 0;
 431                 ref->inode_list = node ?
 432                         (struct extent_inode_elem *)(uintptr_t)node->aux : NULL;
 433
 434                 /* additional parents require new refs being added here */
 435                 while ((node = ulist_next(parents, &uiter))) {
 436                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
 437                                                    GFP_NOFS);
 438                         if (!new_ref) {
 439                                 ret = -ENOMEM;
 440                                 goto out;
 441                         }
 442                         memcpy(new_ref, ref, sizeof(*ref));
 443                         new_ref->parent = node->val;
 444                         new_ref->inode_list = (struct extent_inode_elem *)
 445                                                         (uintptr_t)node->aux;
 446                         list_add(&new_ref->list, &ref->list);
 447                 }
 448                 ulist_reinit(parents);
 449         }
 450 out:
 451         ulist_free(parents);
 452         return ret;
 453 }
 454
 455 static inline int ref_for_same_block(struct __prelim_ref *ref1,
 456                                      struct __prelim_ref *ref2)
 457 {
 458         if (ref1->level != ref2->level)
 459                 return 0;
 460         if (ref1->root_id != ref2->root_id)
 461                 return 0;
 462         if (ref1->key_for_search.type != ref2->key_for_search.type)
 463                 return 0;
 464         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
 465                 return 0;
 466         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
 467                 return 0;
 468         if (ref1->parent != ref2->parent)
 469                 return 0;
 470
 471         return 1;
 472 }
 473
 474 /*
 475  * read tree blocks and add keys where required.
 476  */
 477 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
 478                               struct list_head *head)
 479 {
 480         struct list_head *pos;
 481         struct extent_buffer *eb;
 482
 483         list_for_each(pos, head) {
 484                 struct __prelim_ref *ref;
 485                 ref = list_entry(pos, struct __prelim_ref, list);
 486
 487                 if (ref->parent)
 488                         continue;
 489                 if (ref->key_for_search.type)
 490                         continue;
 491                 BUG_ON(!ref->wanted_disk_byte);
 492                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
 493                                      0);
 494                 if (!eb || !extent_buffer_uptodate(eb)) {
 495                         free_extent_buffer(eb);
 496                         return -EIO;
 497                 }
 498                 btrfs_tree_read_lock(eb);
 499                 if (btrfs_header_level(eb) == 0)
 500                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 501                 else
 502                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 503                 btrfs_tree_read_unlock(eb);
 504                 free_extent_buffer(eb);
 505         }
 506         return 0;
 507 }
 508
 509 /*
 510  * merge two lists of backrefs and adjust counts accordingly
 511  *
 512  * mode = 1: merge identical keys, if key is set
 513  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
 514  *           additionally, we could even add a key range for the blocks we
 515  *           looked into to merge even more (-> replace unresolved refs by those
 516  *           having a parent).
 517  * mode = 2: merge identical parents
 518  */
 519 static void __merge_refs(struct list_head *head, int mode)
 520 {
 521         struct list_head *pos1;
 522
 523         list_for_each(pos1, head) {
 524                 struct list_head *n2;
 525                 struct list_head *pos2;
 526                 struct __prelim_ref *ref1;
 527
 528                 ref1 = list_entry(pos1, struct __prelim_ref, list);
 529
 530                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
 531                      pos2 = n2, n2 = pos2->next) {
 532                         struct __prelim_ref *ref2;
 533                         struct __prelim_ref *xchg;
 534                         struct extent_inode_elem *eie;
 535
 536                         ref2 = list_entry(pos2, struct __prelim_ref, list);
 537
 538                         if (mode == 1) {
 539                                 if (!ref_for_same_block(ref1, ref2))
 540                                         continue;
 541                                 if (!ref1->parent && ref2->parent) {
 542                                         xchg = ref1;
 543                                         ref1 = ref2;
 544                                         ref2 = xchg;
 545                                 }
 546                         } else {
 547                                 if (ref1->parent != ref2->parent)
 548                                         continue;
 549                         }
 550
 551                         eie = ref1->inode_list;
 552                         while (eie && eie->next)
 553                                 eie = eie->next;
 554                         if (eie)
 555                                 eie->next = ref2->inode_list;
 556                         else
 557                                 ref1->inode_list = ref2->inode_list;
 558                         ref1->count += ref2->count;
 559
 560                         list_del(&ref2->list);
 561                         kmem_cache_free(btrfs_prelim_ref_cache, ref2);
 562                 }
 563
 564         }
 565 }
 566
 567 /*
 568  * add all currently queued delayed refs from this head whose seq nr is
 569  * smaller or equal that seq to the list
 570  */
 571 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 572                               struct list_head *prefs, u64 *total_refs,
 573                               u64 inum)
 574 {
 575         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 576         struct rb_node *n = &head->node.rb_node;
 577         struct btrfs_key key;
 578         struct btrfs_key op_key = {0};
 579         int sgn;
 580         int ret = 0;
 581
 582         if (extent_op && extent_op->update_key)
 583                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
 584
 585         spin_lock(&head->lock);
 586         n = rb_first(&head->ref_root);
 587         while (n) {
 588                 struct btrfs_delayed_ref_node *node;
 589                 node = rb_entry(n, struct btrfs_delayed_ref_node,
 590                                 rb_node);
 591                 n = rb_next(n);
 592                 if (node->seq > seq)
 593                         continue;
 594
 595                 switch (node->action) {
 596                 case BTRFS_ADD_DELAYED_EXTENT:
 597                 case BTRFS_UPDATE_DELAYED_HEAD:
 598                         WARN_ON(1);
 599                         continue;
 600                 case BTRFS_ADD_DELAYED_REF:
 601                         sgn = 1;
 602                         break;
 603                 case BTRFS_DROP_DELAYED_REF:
 604                         sgn = -1;
 605                         break;
 606                 default:
 607                         BUG_ON(1);
 608                 }
 609                 *total_refs += (node->ref_mod * sgn);
 610                 switch (node->type) {
 611                 case BTRFS_TREE_BLOCK_REF_KEY: {
 612                         struct btrfs_delayed_tree_ref *ref;
 613
 614                         ref = btrfs_delayed_node_to_tree_ref(node);
 615                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
 616                                                ref->level + 1, 0, node->bytenr,
 617                                                node->ref_mod * sgn, GFP_ATOMIC);
 618                         break;
 619                 }
 620                 case BTRFS_SHARED_BLOCK_REF_KEY: {
 621                         struct btrfs_delayed_tree_ref *ref;
 622
 623                         ref = btrfs_delayed_node_to_tree_ref(node);
 624                         ret = __add_prelim_ref(prefs, ref->root, NULL,
 625                                                ref->level + 1, ref->parent,
 626                                                node->bytenr,
 627                                                node->ref_mod * sgn, GFP_ATOMIC);
 628                         break;
 629                 }
 630                 case BTRFS_EXTENT_DATA_REF_KEY: {
 631                         struct btrfs_delayed_data_ref *ref;
 632                         ref = btrfs_delayed_node_to_data_ref(node);
 633
 634                         key.objectid = ref->objectid;
 635                         key.type = BTRFS_EXTENT_DATA_KEY;
 636                         key.offset = ref->offset;
 637
 638                         /*
 639                          * Found a inum that doesn't match our known inum, we
 640                          * know it's shared.
 641                          */
 642                         if (inum && ref->objectid != inum) {
 643                                 ret = BACKREF_FOUND_SHARED;
 644                                 break;
 645                         }
 646
 647                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
 648                                                node->bytenr,
 649                                                node->ref_mod * sgn, GFP_ATOMIC);
 650                         break;
 651                 }
 652                 case BTRFS_SHARED_DATA_REF_KEY: {
 653                         struct btrfs_delayed_data_ref *ref;
 654
 655                         ref = btrfs_delayed_node_to_data_ref(node);
 656
 657                         key.objectid = ref->objectid;
 658                         key.type = BTRFS_EXTENT_DATA_KEY;
 659                         key.offset = ref->offset;
 660                         ret = __add_prelim_ref(prefs, ref->root, &key, 0,
 661                                                ref->parent, node->bytenr,
 662                                                node->ref_mod * sgn, GFP_ATOMIC);
 663                         break;
 664                 }
 665                 default:
 666                         WARN_ON(1);
 667                 }
 668                 if (ret)
 669                         break;
 670         }
 671         spin_unlock(&head->lock);
 672         return ret;
 673 }
 674
 675 /*
 676  * add all inline backrefs for bytenr to the list
 677  */
 678 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
 679                              struct btrfs_path *path, u64 bytenr,
 680                              int *info_level, struct list_head *prefs,
 681                              u64 *total_refs, u64 inum)
 682 {
 683         int ret = 0;
 684         int slot;
 685         struct extent_buffer *leaf;
 686         struct btrfs_key key;
 687         struct btrfs_key found_key;
 688         unsigned long ptr;
 689         unsigned long end;
 690         struct btrfs_extent_item *ei;
 691         u64 flags;
 692         u64 item_size;
 693
 694         /*
 695          * enumerate all inline refs
 696          */
 697         leaf = path->nodes[0];
 698         slot = path->slots[0];
 699
 700         item_size = btrfs_item_size_nr(leaf, slot);
 701         BUG_ON(item_size < sizeof(*ei));
 702
 703         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 704         flags = btrfs_extent_flags(leaf, ei);
 705         *total_refs += btrfs_extent_refs(leaf, ei);
 706         btrfs_item_key_to_cpu(leaf, &found_key, slot);
 707
 708         ptr = (unsigned long)(ei + 1);
 709         end = (unsigned long)ei + item_size;
 710
 711         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
 712             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 713                 struct btrfs_tree_block_info *info;
 714
 715                 info = (struct btrfs_tree_block_info *)ptr;
 716                 *info_level = btrfs_tree_block_level(leaf, info);
 717                 ptr += sizeof(struct btrfs_tree_block_info);
 718                 BUG_ON(ptr > end);
 719         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
 720                 *info_level = found_key.offset;
 721         } else {
 722                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 723         }
 724
 725         while (ptr < end) {
 726                 struct btrfs_extent_inline_ref *iref;
 727                 u64 offset;
 728                 int type;
 729
 730                 iref = (struct btrfs_extent_inline_ref *)ptr;
 731                 type = btrfs_extent_inline_ref_type(leaf, iref);
 732                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
 733
 734                 switch (type) {
 735                 case BTRFS_SHARED_BLOCK_REF_KEY:
 736                         ret = __add_prelim_ref(prefs, 0, NULL,
 737                                                 *info_level + 1, offset,
 738                                                 bytenr, 1, GFP_NOFS);
 739                         break;
 740                 case BTRFS_SHARED_DATA_REF_KEY: {
 741                         struct btrfs_shared_data_ref *sdref;
 742                         int count;
 743
 744                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
 745                         count = btrfs_shared_data_ref_count(leaf, sdref);
 746                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
 747                                                bytenr, count, GFP_NOFS);
 748                         break;
 749                 }
 750                 case BTRFS_TREE_BLOCK_REF_KEY:
 751                         ret = __add_prelim_ref(prefs, offset, NULL,
 752                                                *info_level + 1, 0,
 753                                                bytenr, 1, GFP_NOFS);
 754                         break;
 755                 case BTRFS_EXTENT_DATA_REF_KEY: {
 756                         struct btrfs_extent_data_ref *dref;
 757                         int count;
 758                         u64 root;
 759
 760                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
 761                         count = btrfs_extent_data_ref_count(leaf, dref);
 762                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 763                                                                       dref);
 764                         key.type = BTRFS_EXTENT_DATA_KEY;
 765                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 766
 767                         if (inum && key.objectid != inum) {
 768                                 ret = BACKREF_FOUND_SHARED;
 769                                 break;
 770                         }
 771
 772                         root = btrfs_extent_data_ref_root(leaf, dref);
 773                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 774                                                bytenr, count, GFP_NOFS);
 775                         break;
 776                 }
 777                 default:
 778                         WARN_ON(1);
 779                 }
 780                 if (ret)
 781                         return ret;
 782                 ptr += btrfs_extent_inline_ref_size(type);
 783         }
 784
 785         return 0;
 786 }
 787
 788 /*
 789  * add all non-inline backrefs for bytenr to the list
 790  */
 791 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
 792                             struct btrfs_path *path, u64 bytenr,
 793                             int info_level, struct list_head *prefs, u64 inum)
 794 {
 795         struct btrfs_root *extent_root = fs_info->extent_root;
 796         int ret;
 797         int slot;
 798         struct extent_buffer *leaf;
 799         struct btrfs_key key;
 800
 801         while (1) {
 802                 ret = btrfs_next_item(extent_root, path);
 803                 if (ret < 0)
 804                         break;
 805                 if (ret) {
 806                         ret = 0;
 807                         break;
 808                 }
 809
 810                 slot = path->slots[0];
 811                 leaf = path->nodes[0];
 812                 btrfs_item_key_to_cpu(leaf, &key, slot);
 813
 814                 if (key.objectid != bytenr)
 815                         break;
 816                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
 817                         continue;
 818                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
 819                         break;
 820
 821                 switch (key.type) {
 822                 case BTRFS_SHARED_BLOCK_REF_KEY:
 823                         ret = __add_prelim_ref(prefs, 0, NULL,
 824                                                 info_level + 1, key.offset,
 825                                                 bytenr, 1, GFP_NOFS);
 826                         break;
 827                 case BTRFS_SHARED_DATA_REF_KEY: {
 828                         struct btrfs_shared_data_ref *sdref;
 829                         int count;
 830
 831                         sdref = btrfs_item_ptr(leaf, slot,
 832                                               struct btrfs_shared_data_ref);
 833                         count = btrfs_shared_data_ref_count(leaf, sdref);
 834                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
 835                                                 bytenr, count, GFP_NOFS);
 836                         break;
 837                 }
 838                 case BTRFS_TREE_BLOCK_REF_KEY:
 839                         ret = __add_prelim_ref(prefs, key.offset, NULL,
 840                                                info_level + 1, 0,
 841                                                bytenr, 1, GFP_NOFS);
 842                         break;
 843                 case BTRFS_EXTENT_DATA_REF_KEY: {
 844                         struct btrfs_extent_data_ref *dref;
 845                         int count;
 846                         u64 root;
 847
 848                         dref = btrfs_item_ptr(leaf, slot,
 849                                               struct btrfs_extent_data_ref);
 850                         count = btrfs_extent_data_ref_count(leaf, dref);
 851                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 852                                                                       dref);
 853                         key.type = BTRFS_EXTENT_DATA_KEY;
 854                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 855
 856                         if (inum && key.objectid != inum) {
 857                                 ret = BACKREF_FOUND_SHARED;
 858                                 break;
 859                         }
 860
 861                         root = btrfs_extent_data_ref_root(leaf, dref);
 862                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 863                                                bytenr, count, GFP_NOFS);
 864                         break;
 865                 }
 866                 default:
 867                         WARN_ON(1);
 868                 }
 869                 if (ret)
 870                         return ret;
 871
 872         }
 873
 874         return ret;
 875 }
 876
 877 /*
 878  * this adds all existing backrefs (inline backrefs, backrefs and delayed
 879  * refs) for the given bytenr to the refs list, merges duplicates and resolves
 880  * indirect refs to their parent bytenr.
 881  * When roots are found, they're added to the roots list
 882  *
 883  * FIXME some caching might speed things up
 884  */
 885 static int find_parent_nodes(struct btrfs_trans_handle *trans,
 886                              struct btrfs_fs_info *fs_info, u64 bytenr,
 887                              u64 time_seq, struct ulist *refs,
 888                              struct ulist *roots, const u64 *extent_item_pos,
 889                              u64 root_objectid, u64 inum)
 890 {
 891         struct btrfs_key key;
 892         struct btrfs_path *path;
 893         struct btrfs_delayed_ref_root *delayed_refs = NULL;
 894         struct btrfs_delayed_ref_head *head;
 895         int info_level = 0;
 896         int ret;
 897         struct list_head prefs_delayed;
 898         struct list_head prefs;
 899         struct __prelim_ref *ref;
 900         struct extent_inode_elem *eie = NULL;
 901         u64 total_refs = 0;
 902
 903         INIT_LIST_HEAD(&prefs);
 904         INIT_LIST_HEAD(&prefs_delayed);
 905
 906         key.objectid = bytenr;
 907         key.offset = (u64)-1;
 908         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
 909                 key.type = BTRFS_METADATA_ITEM_KEY;
 910         else
 911                 key.type = BTRFS_EXTENT_ITEM_KEY;
 912
 913         path = btrfs_alloc_path();
 914         if (!path)
 915                 return -ENOMEM;
 916         if (!trans) {
 917                 path->search_commit_root = 1;
 918                 path->skip_locking = 1;
 919         }
 920
 921         /*
 922          * grab both a lock on the path and a lock on the delayed ref head.
 923          * We need both to get a consistent picture of how the refs look
 924          * at a specified point in time
 925          */
 926 again:
 927         head = NULL;
 928
 929         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
 930         if (ret < 0)
 931                 goto out;
 932         BUG_ON(ret == 0);
 933
 934 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 935         if (trans && likely(trans->type != __TRANS_DUMMY)) {
 936 #else
 937         if (trans) {
 938 #endif
 939                 /*
 940                  * look if there are updates for this ref queued and lock the
 941                  * head
 942                  */
 943                 delayed_refs = &trans->transaction->delayed_refs;
 944                 spin_lock(&delayed_refs->lock);
 945                 head = btrfs_find_delayed_ref_head(trans, bytenr);
 946                 if (head) {
 947                         if (!mutex_trylock(&head->mutex)) {
 948                                 atomic_inc(&head->node.refs);
 949                                 spin_unlock(&delayed_refs->lock);
 950
 951                                 btrfs_release_path(path);
 952
 953                                 /*
 954                                  * Mutex was contended, block until it's
 955                                  * released and try again
 956                                  */
 957                                 mutex_lock(&head->mutex);
 958                                 mutex_unlock(&head->mutex);
 959                                 btrfs_put_delayed_ref(&head->node);
 960                                 goto again;
 961                         }
 962                         spin_unlock(&delayed_refs->lock);
 963                         ret = __add_delayed_refs(head, time_seq,
 964                                                  &prefs_delayed, &total_refs,
 965                                                  inum);
 966                         mutex_unlock(&head->mutex);
 967                         if (ret)
 968                                 goto out;
 969                 } else {
 970                         spin_unlock(&delayed_refs->lock);
 971                 }
 972         }
 973
 974         if (path->slots[0]) {
 975                 struct extent_buffer *leaf;
 976                 int slot;
 977
 978                 path->slots[0]--;
 979                 leaf = path->nodes[0];
 980                 slot = path->slots[0];
 981                 btrfs_item_key_to_cpu(leaf, &key, slot);
 982                 if (key.objectid == bytenr &&
 983                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
 984                      key.type == BTRFS_METADATA_ITEM_KEY)) {
 985                         ret = __add_inline_refs(fs_info, path, bytenr,
 986                                                 &info_level, &prefs,
 987                                                 &total_refs, inum);
 988                         if (ret)
 989                                 goto out;
 990                         ret = __add_keyed_refs(fs_info, path, bytenr,
 991                                                info_level, &prefs, inum);
 992                         if (ret)
 993                                 goto out;
 994                 }
 995         }
 996         btrfs_release_path(path);
 997
 998         list_splice_init(&prefs_delayed, &prefs);
 999
1000         ret = __add_missing_keys(fs_info, &prefs);
1001         if (ret)
1002                 goto out;
1003
1004         __merge_refs(&prefs, 1);
1005
1006         ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs,
1007                                       extent_item_pos, total_refs,
1008                                       root_objectid);
1009         if (ret)
1010                 goto out;
1011
1012         __merge_refs(&prefs, 2);
1013
1014         while (!list_empty(&prefs)) {
1015                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
1016                 WARN_ON(ref->count < 0);
1017                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1018                         if (root_objectid && ref->root_id != root_objectid) {
1019                                 ret = BACKREF_FOUND_SHARED;
1020                                 goto out;
1021                         }
1022
1023                         /* no parent == root of tree */
1024                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1025                         if (ret < 0)
1026                                 goto out;
1027                 }
1028                 if (ref->count && ref->parent) {
1029                         if (extent_item_pos && !ref->inode_list &&
1030                             ref->level == 0) {
1031                                 struct extent_buffer *eb;
1032
1033                                 eb = read_tree_block(fs_info->extent_root,
1034                                                            ref->parent, 0);
1035                                 if (!eb || !extent_buffer_uptodate(eb)) {
1036                                         free_extent_buffer(eb);
1037                                         ret = -EIO;
1038                                         goto out;
1039                                 }
1040                                 btrfs_tree_read_lock(eb);
1041                                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1042                                 ret = find_extent_in_eb(eb, bytenr,
1043                                                         *extent_item_pos, &eie);
1044                                 btrfs_tree_read_unlock_blocking(eb);
1045                                 free_extent_buffer(eb);
1046                                 if (ret < 0)
1047                                         goto out;
1048                                 ref->inode_list = eie;
1049                         }
1050                         ret = ulist_add_merge_ptr(refs, ref->parent,
1051                                                   ref->inode_list,
1052                                                   (void **)&eie, GFP_NOFS);
1053                         if (ret < 0)
1054                                 goto out;
1055                         if (!ret && extent_item_pos) {
1056                                 /*
1057                                  * we've recorded that parent, so we must extend
1058                                  * its inode list here
1059                                  */
1060                                 BUG_ON(!eie);
1061                                 while (eie->next)
1062                                         eie = eie->next;
1063                                 eie->next = ref->inode_list;
1064                         }
1065                         eie = NULL;
1066                 }
1067                 list_del(&ref->list);
1068                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1069         }
1070
1071 out:
1072         btrfs_free_path(path);
1073         while (!list_empty(&prefs)) {
1074                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
1075                 list_del(&ref->list);
1076                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1077         }
1078         while (!list_empty(&prefs_delayed)) {
1079                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
1080                                        list);
1081                 list_del(&ref->list);
1082                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1083         }
1084         if (ret < 0)
1085                 free_inode_elem_list(eie);
1086         return ret;
1087 }
1088
1089 static void free_leaf_list(struct ulist *blocks)
1090 {
1091         struct ulist_node *node = NULL;
1092         struct extent_inode_elem *eie;
1093         struct ulist_iterator uiter;
1094
1095         ULIST_ITER_INIT(&uiter);
1096         while ((node = ulist_next(blocks, &uiter))) {
1097                 if (!node->aux)
1098                         continue;
1099                 eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
1100                 free_inode_elem_list(eie);
1101                 node->aux = 0;
1102         }
1103
1104         ulist_free(blocks);
1105 }
1106
1107 /*
1108  * Finds all leafs with a reference to the specified combination of bytenr and
1109  * offset. key_list_head will point to a list of corresponding keys (caller must
1110  * free each list element). The leafs will be stored in the leafs ulist, which
1111  * must be freed with ulist_free.
1112  *
1113  * returns 0 on success, <0 on error
1114  */
1115 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1116                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1117                                 u64 time_seq, struct ulist **leafs,
1118                                 const u64 *extent_item_pos)
1119 {
1120         int ret;
1121
1122         *leafs = ulist_alloc(GFP_NOFS);
1123         if (!*leafs)
1124                 return -ENOMEM;
1125
1126         ret = find_parent_nodes(trans, fs_info, bytenr,
1127                                 time_seq, *leafs, NULL, extent_item_pos, 0, 0);
1128         if (ret < 0 && ret != -ENOENT) {
1129                 free_leaf_list(*leafs);
1130                 return ret;
1131         }
1132
1133         return 0;
1134 }
1135
1136 /*
1137  * walk all backrefs for a given extent to find all roots that reference this
1138  * extent. Walking a backref means finding all extents that reference this
1139  * extent and in turn walk the backrefs of those, too. Naturally this is a
1140  * recursive process, but here it is implemented in an iterative fashion: We
1141  * find all referencing extents for the extent in question and put them on a
1142  * list. In turn, we find all referencing extents for those, further appending
1143  * to the list. The way we iterate the list allows adding more elements after
1144  * the current while iterating. The process stops when we reach the end of the
1145  * list. Found roots are added to the roots list.
1146  *
1147  * returns 0 on success, < 0 on error.
1148  */
1149 static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1150                                   struct btrfs_fs_info *fs_info, u64 bytenr,
1151                                   u64 time_seq, struct ulist **roots)
1152 {
1153         struct ulist *tmp;
1154         struct ulist_node *node = NULL;
1155         struct ulist_iterator uiter;
1156         int ret;
1157
1158         tmp = ulist_alloc(GFP_NOFS);
1159         if (!tmp)
1160                 return -ENOMEM;
1161         *roots = ulist_alloc(GFP_NOFS);
1162         if (!*roots) {
1163                 ulist_free(tmp);
1164                 return -ENOMEM;
1165         }
1166
1167         ULIST_ITER_INIT(&uiter);
1168         while (1) {
1169                 ret = find_parent_nodes(trans, fs_info, bytenr,
1170                                         time_seq, tmp, *roots, NULL, 0, 0);
1171                 if (ret < 0 && ret != -ENOENT) {
1172                         ulist_free(tmp);
1173                         ulist_free(*roots);
1174                         return ret;
1175                 }
1176                 node = ulist_next(tmp, &uiter);
1177                 if (!node)
1178                         break;
1179                 bytenr = node->val;
1180                 cond_resched();
1181         }
1182
1183         ulist_free(tmp);
1184         return 0;
1185 }
1186
1187 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1188                          struct btrfs_fs_info *fs_info, u64 bytenr,
1189                          u64 time_seq, struct ulist **roots)
1190 {
1191         int ret;
1192
1193         if (!trans)
1194                 down_read(&fs_info->commit_root_sem);
1195         ret = __btrfs_find_all_roots(trans, fs_info, bytenr, time_seq, roots);
1196         if (!trans)
1197                 up_read(&fs_info->commit_root_sem);
1198         return ret;
1199 }
1200
1201 int btrfs_check_shared(struct btrfs_trans_handle *trans,
1202                        struct btrfs_fs_info *fs_info, u64 root_objectid,
1203                        u64 inum, u64 bytenr)
1204 {
1205         struct ulist *tmp = NULL;
1206         struct ulist *roots = NULL;
1207         struct ulist_iterator uiter;
1208         struct ulist_node *node;
1209         struct seq_list elem = {};
1210         int ret = 0;
1211
1212         tmp = ulist_alloc(GFP_NOFS);
1213         roots = ulist_alloc(GFP_NOFS);
1214         if (!tmp || !roots) {
1215                 ulist_free(tmp);
1216                 ulist_free(roots);
1217                 return -ENOMEM;
1218         }
1219
1220         if (trans)
1221                 btrfs_get_tree_mod_seq(fs_info, &elem);
1222         else
1223                 down_read(&fs_info->commit_root_sem);
1224         ULIST_ITER_INIT(&uiter);
1225         while (1) {
1226                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1227                                         roots, NULL, root_objectid, inum);
1228                 if (ret == BACKREF_FOUND_SHARED) {
1229                         ret = 1;
1230                         break;
1231                 }
1232                 if (ret < 0 && ret != -ENOENT)
1233                         break;
1234                 node = ulist_next(tmp, &uiter);
1235                 if (!node)
1236                         break;
1237                 bytenr = node->val;
1238                 cond_resched();
1239         }
1240         if (trans)
1241                 btrfs_put_tree_mod_seq(fs_info, &elem);
1242         else
1243                 up_read(&fs_info->commit_root_sem);
1244         ulist_free(tmp);
1245         ulist_free(roots);
1246         return ret;
1247 }
1248
1249 /*
1250  * this makes the path point to (inum INODE_ITEM ioff)
1251  */
1252 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1253                         struct btrfs_path *path)
1254 {
1255         struct btrfs_key key;
1256         return btrfs_find_item(fs_root, path, inum, ioff,
1257                         BTRFS_INODE_ITEM_KEY, &key);
1258 }
1259
1260 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1261                                 struct btrfs_path *path,
1262                                 struct btrfs_key *found_key)
1263 {
1264         return btrfs_find_item(fs_root, path, inum, ioff,
1265                         BTRFS_INODE_REF_KEY, found_key);
1266 }
1267
1268 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1269                           u64 start_off, struct btrfs_path *path,
1270                           struct btrfs_inode_extref **ret_extref,
1271                           u64 *found_off)
1272 {
1273         int ret, slot;
1274         struct btrfs_key key;
1275         struct btrfs_key found_key;
1276         struct btrfs_inode_extref *extref;
1277         struct extent_buffer *leaf;
1278         unsigned long ptr;
1279
1280         key.objectid = inode_objectid;
1281         key.type = BTRFS_INODE_EXTREF_KEY;
1282         key.offset = start_off;
1283
1284         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1285         if (ret < 0)
1286                 return ret;
1287
1288         while (1) {
1289                 leaf = path->nodes[0];
1290                 slot = path->slots[0];
1291                 if (slot >= btrfs_header_nritems(leaf)) {
1292                         /*
1293                          * If the item at offset is not found,
1294                          * btrfs_search_slot will point us to the slot
1295                          * where it should be inserted. In our case
1296                          * that will be the slot directly before the
1297                          * next INODE_REF_KEY_V2 item. In the case
1298                          * that we're pointing to the last slot in a
1299                          * leaf, we must move one leaf over.
1300                          */
1301                         ret = btrfs_next_leaf(root, path);
1302                         if (ret) {
1303                                 if (ret >= 1)
1304                                         ret = -ENOENT;
1305                                 break;
1306                         }
1307                         continue;
1308                 }
1309
1310                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1311
1312                 /*
1313                  * Check that we're still looking at an extended ref key for
1314                  * this particular objectid. If we have different
1315                  * objectid or type then there are no more to be found
1316                  * in the tree and we can exit.
1317                  */
1318                 ret = -ENOENT;
1319                 if (found_key.objectid != inode_objectid)
1320                         break;
1321                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1322                         break;
1323
1324                 ret = 0;
1325                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1326                 extref = (struct btrfs_inode_extref *)ptr;
1327                 *ret_extref = extref;
1328                 if (found_off)
1329                         *found_off = found_key.offset;
1330                 break;
1331         }
1332
1333         return ret;
1334 }
1335
1336 /*
1337  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1338  * Elements of the path are separated by '/' and the path is guaranteed to be
1339  * 0-terminated. the path is only given within the current file system.
1340  * Therefore, it never starts with a '/'. the caller is responsible to provide
1341  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1342  * the start point of the resulting string is returned. this pointer is within
1343  * dest, normally.
1344  * in case the path buffer would overflow, the pointer is decremented further
1345  * as if output was written to the buffer, though no more output is actually
1346  * generated. that way, the caller can determine how much space would be
1347  * required for the path to fit into the buffer. in that case, the returned
1348  * value will be smaller than dest. callers must check this!
1349  */
1350 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1351                         u32 name_len, unsigned long name_off,
1352                         struct extent_buffer *eb_in, u64 parent,
1353                         char *dest, u32 size)
1354 {
1355         int slot;
1356         u64 next_inum;
1357         int ret;
1358         s64 bytes_left = ((s64)size) - 1;
1359         struct extent_buffer *eb = eb_in;
1360         struct btrfs_key found_key;
1361         int leave_spinning = path->leave_spinning;
1362         struct btrfs_inode_ref *iref;
1363
1364         if (bytes_left >= 0)
1365                 dest[bytes_left] = '\0';
1366
1367         path->leave_spinning = 1;
1368         while (1) {
1369                 bytes_left -= name_len;
1370                 if (bytes_left >= 0)
1371                         read_extent_buffer(eb, dest + bytes_left,
1372                                            name_off, name_len);
1373                 if (eb != eb_in) {
1374                         btrfs_tree_read_unlock_blocking(eb);
1375                         free_extent_buffer(eb);
1376                 }
1377                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1378                 if (ret > 0)
1379                         ret = -ENOENT;
1380                 if (ret)
1381                         break;
1382
1383                 next_inum = found_key.offset;
1384
1385                 /* regular exit ahead */
1386                 if (parent == next_inum)
1387                         break;
1388
1389                 slot = path->slots[0];
1390                 eb = path->nodes[0];
1391                 /* make sure we can use eb after releasing the path */
1392                 if (eb != eb_in) {
1393                         atomic_inc(&eb->refs);
1394                         btrfs_tree_read_lock(eb);
1395                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1396                 }
1397                 btrfs_release_path(path);
1398                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1399
1400                 name_len = btrfs_inode_ref_name_len(eb, iref);
1401                 name_off = (unsigned long)(iref + 1);
1402
1403                 parent = next_inum;
1404                 --bytes_left;
1405                 if (bytes_left >= 0)
1406                         dest[bytes_left] = '/';
1407         }
1408
1409         btrfs_release_path(path);
1410         path->leave_spinning = leave_spinning;
1411
1412         if (ret)
1413                 return ERR_PTR(ret);
1414
1415         return dest + bytes_left;
1416 }
1417
1418 /*
1419  * this makes the path point to (logical EXTENT_ITEM *)
1420  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1421  * tree blocks and <0 on error.
1422  */
1423 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1424                         struct btrfs_path *path, struct btrfs_key *found_key,
1425                         u64 *flags_ret)
1426 {
1427         int ret;
1428         u64 flags;
1429         u64 size = 0;
1430         u32 item_size;
1431         struct extent_buffer *eb;
1432         struct btrfs_extent_item *ei;
1433         struct btrfs_key key;
1434
1435         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1436                 key.type = BTRFS_METADATA_ITEM_KEY;
1437         else
1438                 key.type = BTRFS_EXTENT_ITEM_KEY;
1439         key.objectid = logical;
1440         key.offset = (u64)-1;
1441
1442         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1443         if (ret < 0)
1444                 return ret;
1445
1446         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1447         if (ret) {
1448                 if (ret > 0)
1449                         ret = -ENOENT;
1450                 return ret;
1451         }
1452         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1453         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1454                 size = fs_info->extent_root->nodesize;
1455         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1456                 size = found_key->offset;
1457
1458         if (found_key->objectid > logical ||
1459             found_key->objectid + size <= logical) {
1460                 pr_debug("logical %llu is not within any extent\n", logical);
1461                 return -ENOENT;
1462         }
1463
1464         eb = path->nodes[0];
1465         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1466         BUG_ON(item_size < sizeof(*ei));
1467
1468         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1469         flags = btrfs_extent_flags(eb, ei);
1470
1471         pr_debug("logical %llu is at position %llu within the extent (%llu "
1472                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1473                  logical, logical - found_key->objectid, found_key->objectid,
1474                  found_key->offset, flags, item_size);
1475
1476         WARN_ON(!flags_ret);
1477         if (flags_ret) {
1478                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1479                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1480                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1481                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1482                 else
1483                         BUG_ON(1);
1484                 return 0;
1485         }
1486
1487         return -EIO;
1488 }
1489
1490 /*
1491  * helper function to iterate extent inline refs. ptr must point to a 0 value
1492  * for the first call and may be modified. it is used to track state.
1493  * if more refs exist, 0 is returned and the next call to
1494  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1495  * next ref. after the last ref was processed, 1 is returned.
1496  * returns <0 on error
1497  */
1498 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1499                                    struct btrfs_key *key,
1500                                    struct btrfs_extent_item *ei, u32 item_size,
1501                                    struct btrfs_extent_inline_ref **out_eiref,
1502                                    int *out_type)
1503 {
1504         unsigned long end;
1505         u64 flags;
1506         struct btrfs_tree_block_info *info;
1507
1508         if (!*ptr) {
1509                 /* first call */
1510                 flags = btrfs_extent_flags(eb, ei);
1511                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1512                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1513                                 /* a skinny metadata extent */
1514                                 *out_eiref =
1515                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1516                         } else {
1517                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1518                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1519                                 *out_eiref =
1520                                    (struct btrfs_extent_inline_ref *)(info + 1);
1521                         }
1522                 } else {
1523                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1524                 }
1525                 *ptr = (unsigned long)*out_eiref;
1526                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1527                         return -ENOENT;
1528         }
1529
1530         end = (unsigned long)ei + item_size;
1531         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1532         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1533
1534         *ptr += btrfs_extent_inline_ref_size(*out_type);
1535         WARN_ON(*ptr > end);
1536         if (*ptr == end)
1537                 return 1; /* last */
1538
1539         return 0;
1540 }
1541
1542 /*
1543  * reads the tree block backref for an extent. tree level and root are returned
1544  * through out_level and out_root. ptr must point to a 0 value for the first
1545  * call and may be modified (see __get_extent_inline_ref comment).
1546  * returns 0 if data was provided, 1 if there was no more data to provide or
1547  * <0 on error.
1548  */
1549 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1550                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1551                             u32 item_size, u64 *out_root, u8 *out_level)
1552 {
1553         int ret;
1554         int type;
1555         struct btrfs_tree_block_info *info;
1556         struct btrfs_extent_inline_ref *eiref;
1557
1558         if (*ptr == (unsigned long)-1)
1559                 return 1;
1560
1561         while (1) {
1562                 ret = __get_extent_inline_ref(ptr, eb, key, ei, item_size,
1563                                               &eiref, &type);
1564                 if (ret < 0)
1565                         return ret;
1566
1567                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1568                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1569                         break;
1570
1571                 if (ret == 1)
1572                         return 1;
1573         }
1574
1575         /* we can treat both ref types equally here */
1576         info = (struct btrfs_tree_block_info *)(ei + 1);
1577         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1578         *out_level = btrfs_tree_block_level(eb, info);
1579
1580         if (ret == 1)
1581                 *ptr = (unsigned long)-1;
1582
1583         return 0;
1584 }
1585
1586 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1587                                 u64 root, u64 extent_item_objectid,
1588                                 iterate_extent_inodes_t *iterate, void *ctx)
1589 {
1590         struct extent_inode_elem *eie;
1591         int ret = 0;
1592
1593         for (eie = inode_list; eie; eie = eie->next) {
1594                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1595                          "root %llu\n", extent_item_objectid,
1596                          eie->inum, eie->offset, root);
1597                 ret = iterate(eie->inum, eie->offset, root, ctx);
1598                 if (ret) {
1599                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1600                                  extent_item_objectid, ret);
1601                         break;
1602                 }
1603         }
1604
1605         return ret;
1606 }
1607
1608 /*
1609  * calls iterate() for every inode that references the extent identified by
1610  * the given parameters.
1611  * when the iterator function returns a non-zero value, iteration stops.
1612  */
1613 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1614                                 u64 extent_item_objectid, u64 extent_item_pos,
1615                                 int search_commit_root,
1616                                 iterate_extent_inodes_t *iterate, void *ctx)
1617 {
1618         int ret;
1619         struct btrfs_trans_handle *trans = NULL;
1620         struct ulist *refs = NULL;
1621         struct ulist *roots = NULL;
1622         struct ulist_node *ref_node = NULL;
1623         struct ulist_node *root_node = NULL;
1624         struct seq_list tree_mod_seq_elem = {};
1625         struct ulist_iterator ref_uiter;
1626         struct ulist_iterator root_uiter;
1627
1628         pr_debug("resolving all inodes for extent %llu\n",
1629                         extent_item_objectid);
1630
1631         if (!search_commit_root) {
1632                 trans = btrfs_join_transaction(fs_info->extent_root);
1633                 if (IS_ERR(trans))
1634                         return PTR_ERR(trans);
1635                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1636         } else {
1637                 down_read(&fs_info->commit_root_sem);
1638         }
1639
1640         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1641                                    tree_mod_seq_elem.seq, &refs,
1642                                    &extent_item_pos);
1643         if (ret)
1644                 goto out;
1645
1646         ULIST_ITER_INIT(&ref_uiter);
1647         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1648                 ret = __btrfs_find_all_roots(trans, fs_info, ref_node->val,
1649                                              tree_mod_seq_elem.seq, &roots);
1650                 if (ret)
1651                         break;
1652                 ULIST_ITER_INIT(&root_uiter);
1653                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1654                         pr_debug("root %llu references leaf %llu, data list "
1655                                  "%#llx\n", root_node->val, ref_node->val,
1656                                  ref_node->aux);
1657                         ret = iterate_leaf_refs((struct extent_inode_elem *)
1658                                                 (uintptr_t)ref_node->aux,
1659                                                 root_node->val,
1660                                                 extent_item_objectid,
1661                                                 iterate, ctx);
1662                 }
1663                 ulist_free(roots);
1664         }
1665
1666         free_leaf_list(refs);
1667 out:
1668         if (!search_commit_root) {
1669                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1670                 btrfs_end_transaction(trans, fs_info->extent_root);
1671         } else {
1672                 up_read(&fs_info->commit_root_sem);
1673         }
1674
1675         return ret;
1676 }
1677
1678 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1679                                 struct btrfs_path *path,
1680                                 iterate_extent_inodes_t *iterate, void *ctx)
1681 {
1682         int ret;
1683         u64 extent_item_pos;
1684         u64 flags = 0;
1685         struct btrfs_key found_key;
1686         int search_commit_root = path->search_commit_root;
1687
1688         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1689         btrfs_release_path(path);
1690         if (ret < 0)
1691                 return ret;
1692         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1693                 return -EINVAL;
1694
1695         extent_item_pos = logical - found_key.objectid;
1696         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1697                                         extent_item_pos, search_commit_root,
1698                                         iterate, ctx);
1699
1700         return ret;
1701 }
1702
1703 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1704                               struct extent_buffer *eb, void *ctx);
1705
1706 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1707                               struct btrfs_path *path,
1708                               iterate_irefs_t *iterate, void *ctx)
1709 {
1710         int ret = 0;
1711         int slot;
1712         u32 cur;
1713         u32 len;
1714         u32 name_len;
1715         u64 parent = 0;
1716         int found = 0;
1717         struct extent_buffer *eb;
1718         struct btrfs_item *item;
1719         struct btrfs_inode_ref *iref;
1720         struct btrfs_key found_key;
1721
1722         while (!ret) {
1723                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1724                                      &found_key);
1725                 if (ret < 0)
1726                         break;
1727                 if (ret) {
1728                         ret = found ? 0 : -ENOENT;
1729                         break;
1730                 }
1731                 ++found;
1732
1733                 parent = found_key.offset;
1734                 slot = path->slots[0];
1735                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1736                 if (!eb) {
1737                         ret = -ENOMEM;
1738                         break;
1739                 }
1740                 extent_buffer_get(eb);
1741                 btrfs_tree_read_lock(eb);
1742                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1743                 btrfs_release_path(path);
1744
1745                 item = btrfs_item_nr(slot);
1746                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1747
1748                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1749                         name_len = btrfs_inode_ref_name_len(eb, iref);
1750                         /* path must be released before calling iterate()! */
1751                         pr_debug("following ref at offset %u for inode %llu in "
1752                                  "tree %llu\n", cur, found_key.objectid,
1753                                  fs_root->objectid);
1754                         ret = iterate(parent, name_len,
1755                                       (unsigned long)(iref + 1), eb, ctx);
1756                         if (ret)
1757                                 break;
1758                         len = sizeof(*iref) + name_len;
1759                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1760                 }
1761                 btrfs_tree_read_unlock_blocking(eb);
1762                 free_extent_buffer(eb);
1763         }
1764
1765         btrfs_release_path(path);
1766
1767         return ret;
1768 }
1769
1770 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1771                                  struct btrfs_path *path,
1772                                  iterate_irefs_t *iterate, void *ctx)
1773 {
1774         int ret;
1775         int slot;
1776         u64 offset = 0;
1777         u64 parent;
1778         int found = 0;
1779         struct extent_buffer *eb;
1780         struct btrfs_inode_extref *extref;
1781         struct extent_buffer *leaf;
1782         u32 item_size;
1783         u32 cur_offset;
1784         unsigned long ptr;
1785
1786         while (1) {
1787                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1788                                             &offset);
1789                 if (ret < 0)
1790                         break;
1791                 if (ret) {
1792                         ret = found ? 0 : -ENOENT;
1793                         break;
1794                 }
1795                 ++found;
1796
1797                 slot = path->slots[0];
1798                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1799                 if (!eb) {
1800                         ret = -ENOMEM;
1801                         break;
1802                 }
1803                 extent_buffer_get(eb);
1804
1805                 btrfs_tree_read_lock(eb);
1806                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1807                 btrfs_release_path(path);
1808
1809                 leaf = path->nodes[0];
1810                 item_size = btrfs_item_size_nr(leaf, slot);
1811                 ptr = btrfs_item_ptr_offset(leaf, slot);
1812                 cur_offset = 0;
1813
1814                 while (cur_offset < item_size) {
1815                         u32 name_len;
1816
1817                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1818                         parent = btrfs_inode_extref_parent(eb, extref);
1819                         name_len = btrfs_inode_extref_name_len(eb, extref);
1820                         ret = iterate(parent, name_len,
1821                                       (unsigned long)&extref->name, eb, ctx);
1822                         if (ret)
1823                                 break;
1824
1825                         cur_offset += btrfs_inode_extref_name_len(leaf, extref);
1826                         cur_offset += sizeof(*extref);
1827                 }
1828                 btrfs_tree_read_unlock_blocking(eb);
1829                 free_extent_buffer(eb);
1830
1831                 offset++;
1832         }
1833
1834         btrfs_release_path(path);
1835
1836         return ret;
1837 }
1838
1839 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1840                          struct btrfs_path *path, iterate_irefs_t *iterate,
1841                          void *ctx)
1842 {
1843         int ret;
1844         int found_refs = 0;
1845
1846         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1847         if (!ret)
1848                 ++found_refs;
1849         else if (ret != -ENOENT)
1850                 return ret;
1851
1852         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1853         if (ret == -ENOENT && found_refs)
1854                 return 0;
1855
1856         return ret;
1857 }
1858
1859 /*
1860  * returns 0 if the path could be dumped (probably truncated)
1861  * returns <0 in case of an error
1862  */
1863 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1864                          struct extent_buffer *eb, void *ctx)
1865 {
1866         struct inode_fs_paths *ipath = ctx;
1867         char *fspath;
1868         char *fspath_min;
1869         int i = ipath->fspath->elem_cnt;
1870         const int s_ptr = sizeof(char *);
1871         u32 bytes_left;
1872
1873         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1874                                         ipath->fspath->bytes_left - s_ptr : 0;
1875
1876         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1877         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1878                                    name_off, eb, inum, fspath_min, bytes_left);
1879         if (IS_ERR(fspath))
1880                 return PTR_ERR(fspath);
1881
1882         if (fspath > fspath_min) {
1883                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1884                 ++ipath->fspath->elem_cnt;
1885                 ipath->fspath->bytes_left = fspath - fspath_min;
1886         } else {
1887                 ++ipath->fspath->elem_missed;
1888                 ipath->fspath->bytes_missing += fspath_min - fspath;
1889                 ipath->fspath->bytes_left = 0;
1890         }
1891
1892         return 0;
1893 }
1894
1895 /*
1896  * this dumps all file system paths to the inode into the ipath struct, provided
1897  * is has been created large enough. each path is zero-terminated and accessed
1898  * from ipath->fspath->val[i].
1899  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1900  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1901  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1902  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1903  * have been needed to return all paths.
1904  */
1905 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1906 {
1907         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1908                              inode_to_path, ipath);
1909 }
1910
1911 struct btrfs_data_container *init_data_container(u32 total_bytes)
1912 {
1913         struct btrfs_data_container *data;
1914         size_t alloc_bytes;
1915
1916         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1917         data = vmalloc(alloc_bytes);
1918         if (!data)
1919                 return ERR_PTR(-ENOMEM);
1920
1921         if (total_bytes >= sizeof(*data)) {
1922                 data->bytes_left = total_bytes - sizeof(*data);
1923                 data->bytes_missing = 0;
1924         } else {
1925                 data->bytes_missing = sizeof(*data) - total_bytes;
1926                 data->bytes_left = 0;
1927         }
1928
1929         data->elem_cnt = 0;
1930         data->elem_missed = 0;
1931
1932         return data;
1933 }
1934
1935 /*
1936  * allocates space to return multiple file system paths for an inode.
1937  * total_bytes to allocate are passed, note that space usable for actual path
1938  * information will be total_bytes - sizeof(struct inode_fs_paths).
1939  * the returned pointer must be freed with free_ipath() in the end.
1940  */
1941 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1942                                         struct btrfs_path *path)
1943 {
1944         struct inode_fs_paths *ifp;
1945         struct btrfs_data_container *fspath;
1946
1947         fspath = init_data_container(total_bytes);
1948         if (IS_ERR(fspath))
1949                 return (void *)fspath;
1950
1951         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1952         if (!ifp) {
1953                 kfree(fspath);
1954                 return ERR_PTR(-ENOMEM);
1955         }
1956
1957         ifp->btrfs_path = path;
1958         ifp->fspath = fspath;
1959         ifp->fs_root = fs_root;
1960
1961         return ifp;
1962 }
1963
1964 void free_ipath(struct inode_fs_paths *ipath)
1965 {
1966         if (!ipath)
1967                 return;
1968         vfree(ipath->fspath);
1969         kfree(ipath);
1970 }