fs/btrfs/backref.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2011 STRATO.  All rights reserved.
   4  */
   5
   6 #include <linux/mm.h>
   7 #include <linux/rbtree.h>
   8 #include <trace/events/btrfs.h>
   9 #include "ctree.h"
  10 #include "disk-io.h"
  11 #include "backref.h"
  12 #include "ulist.h"
  13 #include "transaction.h"
  14 #include "delayed-ref.h"
  15 #include "locking.h"
  16 #include "misc.h"
  17 #include "tree-mod-log.h"
  18
  19 /* Just an arbitrary number so we can be sure this happened */
  20 #define BACKREF_FOUND_SHARED 6
  21
  22 struct extent_inode_elem {
  23         u64 inum;
  24         u64 offset;
  25         struct extent_inode_elem *next;
  26 };
  27
  28 static int check_extent_in_eb(const struct btrfs_key *key,
  29                               const struct extent_buffer *eb,
  30                               const struct btrfs_file_extent_item *fi,
  31                               u64 extent_item_pos,
  32                               struct extent_inode_elem **eie,
  33                               bool ignore_offset)
  34 {
  35         u64 offset = 0;
  36         struct extent_inode_elem *e;
  37
  38         if (!ignore_offset &&
  39             !btrfs_file_extent_compression(eb, fi) &&
  40             !btrfs_file_extent_encryption(eb, fi) &&
  41             !btrfs_file_extent_other_encoding(eb, fi)) {
  42                 u64 data_offset;
  43                 u64 data_len;
  44
  45                 data_offset = btrfs_file_extent_offset(eb, fi);
  46                 data_len = btrfs_file_extent_num_bytes(eb, fi);
  47
  48                 if (extent_item_pos < data_offset ||
  49                     extent_item_pos >= data_offset + data_len)
  50                         return 1;
  51                 offset = extent_item_pos - data_offset;
  52         }
  53
  54         e = kmalloc(sizeof(*e), GFP_NOFS);
  55         if (!e)
  56                 return -ENOMEM;
  57
  58         e->next = *eie;
  59         e->inum = key->objectid;
  60         e->offset = key->offset + offset;
  61         *eie = e;
  62
  63         return 0;
  64 }
  65
  66 static void free_inode_elem_list(struct extent_inode_elem *eie)
  67 {
  68         struct extent_inode_elem *eie_next;
  69
  70         for (; eie; eie = eie_next) {
  71                 eie_next = eie->next;
  72                 kfree(eie);
  73         }
  74 }
  75
  76 static int find_extent_in_eb(const struct extent_buffer *eb,
  77                              u64 wanted_disk_byte, u64 extent_item_pos,
  78                              struct extent_inode_elem **eie,
  79                              bool ignore_offset)
  80 {
  81         u64 disk_byte;
  82         struct btrfs_key key;
  83         struct btrfs_file_extent_item *fi;
  84         int slot;
  85         int nritems;
  86         int extent_type;
  87         int ret;
  88
  89         /*
  90          * from the shared data ref, we only have the leaf but we need
  91          * the key. thus, we must look into all items and see that we
  92          * find one (some) with a reference to our extent item.
  93          */
  94         nritems = btrfs_header_nritems(eb);
  95         for (slot = 0; slot < nritems; ++slot) {
  96                 btrfs_item_key_to_cpu(eb, &key, slot);
  97                 if (key.type != BTRFS_EXTENT_DATA_KEY)
  98                         continue;
  99                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 100                 extent_type = btrfs_file_extent_type(eb, fi);
 101                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
 102                         continue;
 103                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
 104                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 105                 if (disk_byte != wanted_disk_byte)
 106                         continue;
 107
 108                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie, ignore_offset);
 109                 if (ret < 0)
 110                         return ret;
 111         }
 112
 113         return 0;
 114 }
 115
 116 struct preftree {
 117         struct rb_root_cached root;
 118         unsigned int count;
 119 };
 120
 121 #define PREFTREE_INIT   { .root = RB_ROOT_CACHED, .count = 0 }
 122
 123 struct preftrees {
 124         struct preftree direct;    /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
 125         struct preftree indirect;  /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
 126         struct preftree indirect_missing_keys;
 127 };
 128
 129 /*
 130  * Checks for a shared extent during backref search.
 131  *
 132  * The share_count tracks prelim_refs (direct and indirect) having a
 133  * ref->count >0:
 134  *  - incremented when a ref->count transitions to >0
 135  *  - decremented when a ref->count transitions to <1
 136  */
 137 struct share_check {
 138         u64 root_objectid;
 139         u64 inum;
 140         int share_count;
 141 };
 142
 143 static inline int extent_is_shared(struct share_check *sc)
 144 {
 145         return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
 146 }
 147
 148 static struct kmem_cache *btrfs_prelim_ref_cache;
 149
 150 int __init btrfs_prelim_ref_init(void)
 151 {
 152         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
 153                                         sizeof(struct prelim_ref),
 154                                         0,
 155                                         SLAB_MEM_SPREAD,
 156                                         NULL);
 157         if (!btrfs_prelim_ref_cache)
 158                 return -ENOMEM;
 159         return 0;
 160 }
 161
 162 void __cold btrfs_prelim_ref_exit(void)
 163 {
 164         kmem_cache_destroy(btrfs_prelim_ref_cache);
 165 }
 166
 167 static void free_pref(struct prelim_ref *ref)
 168 {
 169         kmem_cache_free(btrfs_prelim_ref_cache, ref);
 170 }
 171
 172 /*
 173  * Return 0 when both refs are for the same block (and can be merged).
 174  * A -1 return indicates ref1 is a 'lower' block than ref2, while 1
 175  * indicates a 'higher' block.
 176  */
 177 static int prelim_ref_compare(struct prelim_ref *ref1,
 178                               struct prelim_ref *ref2)
 179 {
 180         if (ref1->level < ref2->level)
 181                 return -1;
 182         if (ref1->level > ref2->level)
 183                 return 1;
 184         if (ref1->root_id < ref2->root_id)
 185                 return -1;
 186         if (ref1->root_id > ref2->root_id)
 187                 return 1;
 188         if (ref1->key_for_search.type < ref2->key_for_search.type)
 189                 return -1;
 190         if (ref1->key_for_search.type > ref2->key_for_search.type)
 191                 return 1;
 192         if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
 193                 return -1;
 194         if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
 195                 return 1;
 196         if (ref1->key_for_search.offset < ref2->key_for_search.offset)
 197                 return -1;
 198         if (ref1->key_for_search.offset > ref2->key_for_search.offset)
 199                 return 1;
 200         if (ref1->parent < ref2->parent)
 201                 return -1;
 202         if (ref1->parent > ref2->parent)
 203                 return 1;
 204
 205         return 0;
 206 }
 207
 208 static void update_share_count(struct share_check *sc, int oldcount,
 209                                int newcount)
 210 {
 211         if ((!sc) || (oldcount == 0 && newcount < 1))
 212                 return;
 213
 214         if (oldcount > 0 && newcount < 1)
 215                 sc->share_count--;
 216         else if (oldcount < 1 && newcount > 0)
 217                 sc->share_count++;
 218 }
 219
 220 /*
 221  * Add @newref to the @root rbtree, merging identical refs.
 222  *
 223  * Callers should assume that newref has been freed after calling.
 224  */
 225 static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
 226                               struct preftree *preftree,
 227                               struct prelim_ref *newref,
 228                               struct share_check *sc)
 229 {
 230         struct rb_root_cached *root;
 231         struct rb_node **p;
 232         struct rb_node *parent = NULL;
 233         struct prelim_ref *ref;
 234         int result;
 235         bool leftmost = true;
 236
 237         root = &preftree->root;
 238         p = &root->rb_root.rb_node;
 239
 240         while (*p) {
 241                 parent = *p;
 242                 ref = rb_entry(parent, struct prelim_ref, rbnode);
 243                 result = prelim_ref_compare(ref, newref);
 244                 if (result < 0) {
 245                         p = &(*p)->rb_left;
 246                 } else if (result > 0) {
 247                         p = &(*p)->rb_right;
 248                         leftmost = false;
 249                 } else {
 250                         /* Identical refs, merge them and free @newref */
 251                         struct extent_inode_elem *eie = ref->inode_list;
 252
 253                         while (eie && eie->next)
 254                                 eie = eie->next;
 255
 256                         if (!eie)
 257                                 ref->inode_list = newref->inode_list;
 258                         else
 259                                 eie->next = newref->inode_list;
 260                         trace_btrfs_prelim_ref_merge(fs_info, ref, newref,
 261                                                      preftree->count);
 262                         /*
 263                          * A delayed ref can have newref->count < 0.
 264                          * The ref->count is updated to follow any
 265                          * BTRFS_[ADD|DROP]_DELAYED_REF actions.
 266                          */
 267                         update_share_count(sc, ref->count,
 268                                            ref->count + newref->count);
 269                         ref->count += newref->count;
 270                         free_pref(newref);
 271                         return;
 272                 }
 273         }
 274
 275         update_share_count(sc, 0, newref->count);
 276         preftree->count++;
 277         trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
 278         rb_link_node(&newref->rbnode, parent, p);
 279         rb_insert_color_cached(&newref->rbnode, root, leftmost);
 280 }
 281
 282 /*
 283  * Release the entire tree.  We don't care about internal consistency so
 284  * just free everything and then reset the tree root.
 285  */
 286 static void prelim_release(struct preftree *preftree)
 287 {
 288         struct prelim_ref *ref, *next_ref;
 289
 290         rbtree_postorder_for_each_entry_safe(ref, next_ref,
 291                                              &preftree->root.rb_root, rbnode)
 292                 free_pref(ref);
 293
 294         preftree->root = RB_ROOT_CACHED;
 295         preftree->count = 0;
 296 }
 297
 298 /*
 299  * the rules for all callers of this function are:
 300  * - obtaining the parent is the goal
 301  * - if you add a key, you must know that it is a correct key
 302  * - if you cannot add the parent or a correct key, then we will look into the
 303  *   block later to set a correct key
 304  *
 305  * delayed refs
 306  * ============
 307  *        backref type | shared | indirect | shared | indirect
 308  * information         |   tree |     tree |   data |     data
 309  * --------------------+--------+----------+--------+----------
 310  *      parent logical |    y   |     -    |    -   |     -
 311  *      key to resolve |    -   |     y    |    y   |     y
 312  *  tree block logical |    -   |     -    |    -   |     -
 313  *  root for resolving |    y   |     y    |    y   |     y
 314  *
 315  * - column 1:       we've the parent -> done
 316  * - column 2, 3, 4: we use the key to find the parent
 317  *
 318  * on disk refs (inline or keyed)
 319  * ==============================
 320  *        backref type | shared | indirect | shared | indirect
 321  * information         |   tree |     tree |   data |     data
 322  * --------------------+--------+----------+--------+----------
 323  *      parent logical |    y   |     -    |    y   |     -
 324  *      key to resolve |    -   |     -    |    -   |     y
 325  *  tree block logical |    y   |     y    |    y   |     y
 326  *  root for resolving |    -   |     y    |    y   |     y
 327  *
 328  * - column 1, 3: we've the parent -> done
 329  * - column 2:    we take the first key from the block to find the parent
 330  *                (see add_missing_keys)
 331  * - column 4:    we use the key to find the parent
 332  *
 333  * additional information that's available but not required to find the parent
 334  * block might help in merging entries to gain some speed.
 335  */
 336 static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
 337                           struct preftree *preftree, u64 root_id,
 338                           const struct btrfs_key *key, int level, u64 parent,
 339                           u64 wanted_disk_byte, int count,
 340                           struct share_check *sc, gfp_t gfp_mask)
 341 {
 342         struct prelim_ref *ref;
 343
 344         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
 345                 return 0;
 346
 347         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
 348         if (!ref)
 349                 return -ENOMEM;
 350
 351         ref->root_id = root_id;
 352         if (key)
 353                 ref->key_for_search = *key;
 354         else
 355                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
 356
 357         ref->inode_list = NULL;
 358         ref->level = level;
 359         ref->count = count;
 360         ref->parent = parent;
 361         ref->wanted_disk_byte = wanted_disk_byte;
 362         prelim_ref_insert(fs_info, preftree, ref, sc);
 363         return extent_is_shared(sc);
 364 }
 365
 366 /* direct refs use root == 0, key == NULL */
 367 static int add_direct_ref(const struct btrfs_fs_info *fs_info,
 368                           struct preftrees *preftrees, int level, u64 parent,
 369                           u64 wanted_disk_byte, int count,
 370                           struct share_check *sc, gfp_t gfp_mask)
 371 {
 372         return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level,
 373                               parent, wanted_disk_byte, count, sc, gfp_mask);
 374 }
 375
 376 /* indirect refs use parent == 0 */
 377 static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
 378                             struct preftrees *preftrees, u64 root_id,
 379                             const struct btrfs_key *key, int level,
 380                             u64 wanted_disk_byte, int count,
 381                             struct share_check *sc, gfp_t gfp_mask)
 382 {
 383         struct preftree *tree = &preftrees->indirect;
 384
 385         if (!key)
 386                 tree = &preftrees->indirect_missing_keys;
 387         return add_prelim_ref(fs_info, tree, root_id, key, level, 0,
 388                               wanted_disk_byte, count, sc, gfp_mask);
 389 }
 390
 391 static int is_shared_data_backref(struct preftrees *preftrees, u64 bytenr)
 392 {
 393         struct rb_node **p = &preftrees->direct.root.rb_root.rb_node;
 394         struct rb_node *parent = NULL;
 395         struct prelim_ref *ref = NULL;
 396         struct prelim_ref target = {};
 397         int result;
 398
 399         target.parent = bytenr;
 400
 401         while (*p) {
 402                 parent = *p;
 403                 ref = rb_entry(parent, struct prelim_ref, rbnode);
 404                 result = prelim_ref_compare(ref, &target);
 405
 406                 if (result < 0)
 407                         p = &(*p)->rb_left;
 408                 else if (result > 0)
 409                         p = &(*p)->rb_right;
 410                 else
 411                         return 1;
 412         }
 413         return 0;
 414 }
 415
 416 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
 417                            struct ulist *parents,
 418                            struct preftrees *preftrees, struct prelim_ref *ref,
 419                            int level, u64 time_seq, const u64 *extent_item_pos,
 420                            bool ignore_offset)
 421 {
 422         int ret = 0;
 423         int slot;
 424         struct extent_buffer *eb;
 425         struct btrfs_key key;
 426         struct btrfs_key *key_for_search = &ref->key_for_search;
 427         struct btrfs_file_extent_item *fi;
 428         struct extent_inode_elem *eie = NULL, *old = NULL;
 429         u64 disk_byte;
 430         u64 wanted_disk_byte = ref->wanted_disk_byte;
 431         u64 count = 0;
 432         u64 data_offset;
 433
 434         if (level != 0) {
 435                 eb = path->nodes[level];
 436                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
 437                 if (ret < 0)
 438                         return ret;
 439                 return 0;
 440         }
 441
 442         /*
 443          * 1. We normally enter this function with the path already pointing to
 444          *    the first item to check. But sometimes, we may enter it with
 445          *    slot == nritems.
 446          * 2. We are searching for normal backref but bytenr of this leaf
 447          *    matches shared data backref
 448          * 3. The leaf owner is not equal to the root we are searching
 449          *
 450          * For these cases, go to the next leaf before we continue.
 451          */
 452         eb = path->nodes[0];
 453         if (path->slots[0] >= btrfs_header_nritems(eb) ||
 454             is_shared_data_backref(preftrees, eb->start) ||
 455             ref->root_id != btrfs_header_owner(eb)) {
 456                 if (time_seq == BTRFS_SEQ_LAST)
 457                         ret = btrfs_next_leaf(root, path);
 458                 else
 459                         ret = btrfs_next_old_leaf(root, path, time_seq);
 460         }
 461
 462         while (!ret && count < ref->count) {
 463                 eb = path->nodes[0];
 464                 slot = path->slots[0];
 465
 466                 btrfs_item_key_to_cpu(eb, &key, slot);
 467
 468                 if (key.objectid != key_for_search->objectid ||
 469                     key.type != BTRFS_EXTENT_DATA_KEY)
 470                         break;
 471
 472                 /*
 473                  * We are searching for normal backref but bytenr of this leaf
 474                  * matches shared data backref, OR
 475                  * the leaf owner is not equal to the root we are searching for
 476                  */
 477                 if (slot == 0 &&
 478                     (is_shared_data_backref(preftrees, eb->start) ||
 479                      ref->root_id != btrfs_header_owner(eb))) {
 480                         if (time_seq == BTRFS_SEQ_LAST)
 481                                 ret = btrfs_next_leaf(root, path);
 482                         else
 483                                 ret = btrfs_next_old_leaf(root, path, time_seq);
 484                         continue;
 485                 }
 486                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 487                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 488                 data_offset = btrfs_file_extent_offset(eb, fi);
 489
 490                 if (disk_byte == wanted_disk_byte) {
 491                         eie = NULL;
 492                         old = NULL;
 493                         if (ref->key_for_search.offset == key.offset - data_offset)
 494                                 count++;
 495                         else
 496                                 goto next;
 497                         if (extent_item_pos) {
 498                                 ret = check_extent_in_eb(&key, eb, fi,
 499                                                 *extent_item_pos,
 500                                                 &eie, ignore_offset);
 501                                 if (ret < 0)
 502                                         break;
 503                         }
 504                         if (ret > 0)
 505                                 goto next;
 506                         ret = ulist_add_merge_ptr(parents, eb->start,
 507                                                   eie, (void **)&old, GFP_NOFS);
 508                         if (ret < 0)
 509                                 break;
 510                         if (!ret && extent_item_pos) {
 511                                 while (old->next)
 512                                         old = old->next;
 513                                 old->next = eie;
 514                         }
 515                         eie = NULL;
 516                 }
 517 next:
 518                 if (time_seq == BTRFS_SEQ_LAST)
 519                         ret = btrfs_next_item(root, path);
 520                 else
 521                         ret = btrfs_next_old_item(root, path, time_seq);
 522         }
 523
 524         if (ret > 0)
 525                 ret = 0;
 526         else if (ret < 0)
 527                 free_inode_elem_list(eie);
 528         return ret;
 529 }
 530
 531 /*
 532  * resolve an indirect backref in the form (root_id, key, level)
 533  * to a logical address
 534  */
 535 static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 536                                 struct btrfs_path *path, u64 time_seq,
 537                                 struct preftrees *preftrees,
 538                                 struct prelim_ref *ref, struct ulist *parents,
 539                                 const u64 *extent_item_pos, bool ignore_offset)
 540 {
 541         struct btrfs_root *root;
 542         struct extent_buffer *eb;
 543         int ret = 0;
 544         int root_level;
 545         int level = ref->level;
 546         struct btrfs_key search_key = ref->key_for_search;
 547
 548         /*
 549          * If we're search_commit_root we could possibly be holding locks on
 550          * other tree nodes.  This happens when qgroups does backref walks when
 551          * adding new delayed refs.  To deal with this we need to look in cache
 552          * for the root, and if we don't find it then we need to search the
 553          * tree_root's commit root, thus the btrfs_get_fs_root_commit_root usage
 554          * here.
 555          */
 556         if (path->search_commit_root)
 557                 root = btrfs_get_fs_root_commit_root(fs_info, path, ref->root_id);
 558         else
 559                 root = btrfs_get_fs_root(fs_info, ref->root_id, false);
 560         if (IS_ERR(root)) {
 561                 ret = PTR_ERR(root);
 562                 goto out_free;
 563         }
 564
 565         if (!path->search_commit_root &&
 566             test_bit(BTRFS_ROOT_DELETING, &root->state)) {
 567                 ret = -ENOENT;
 568                 goto out;
 569         }
 570
 571         if (btrfs_is_testing(fs_info)) {
 572                 ret = -ENOENT;
 573                 goto out;
 574         }
 575
 576         if (path->search_commit_root)
 577                 root_level = btrfs_header_level(root->commit_root);
 578         else if (time_seq == BTRFS_SEQ_LAST)
 579                 root_level = btrfs_header_level(root->node);
 580         else
 581                 root_level = btrfs_old_root_level(root, time_seq);
 582
 583         if (root_level + 1 == level)
 584                 goto out;
 585
 586         /*
 587          * We can often find data backrefs with an offset that is too large
 588          * (>= LLONG_MAX, maximum allowed file offset) due to underflows when
 589          * subtracting a file's offset with the data offset of its
 590          * corresponding extent data item. This can happen for example in the
 591          * clone ioctl.
 592          *
 593          * So if we detect such case we set the search key's offset to zero to
 594          * make sure we will find the matching file extent item at
 595          * add_all_parents(), otherwise we will miss it because the offset
 596          * taken form the backref is much larger then the offset of the file
 597          * extent item. This can make us scan a very large number of file
 598          * extent items, but at least it will not make us miss any.
 599          *
 600          * This is an ugly workaround for a behaviour that should have never
 601          * existed, but it does and a fix for the clone ioctl would touch a lot
 602          * of places, cause backwards incompatibility and would not fix the
 603          * problem for extents cloned with older kernels.
 604          */
 605         if (search_key.type == BTRFS_EXTENT_DATA_KEY &&
 606             search_key.offset >= LLONG_MAX)
 607                 search_key.offset = 0;
 608         path->lowest_level = level;
 609         if (time_seq == BTRFS_SEQ_LAST)
 610                 ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
 611         else
 612                 ret = btrfs_search_old_slot(root, &search_key, path, time_seq);
 613
 614         btrfs_debug(fs_info,
 615                 "search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
 616                  ref->root_id, level, ref->count, ret,
 617                  ref->key_for_search.objectid, ref->key_for_search.type,
 618                  ref->key_for_search.offset);
 619         if (ret < 0)
 620                 goto out;
 621
 622         eb = path->nodes[level];
 623         while (!eb) {
 624                 if (WARN_ON(!level)) {
 625                         ret = 1;
 626                         goto out;
 627                 }
 628                 level--;
 629                 eb = path->nodes[level];
 630         }
 631
 632         ret = add_all_parents(root, path, parents, preftrees, ref, level,
 633                               time_seq, extent_item_pos, ignore_offset);
 634 out:
 635         btrfs_put_root(root);
 636 out_free:
 637         path->lowest_level = 0;
 638         btrfs_release_path(path);
 639         return ret;
 640 }
 641
 642 static struct extent_inode_elem *
 643 unode_aux_to_inode_list(struct ulist_node *node)
 644 {
 645         if (!node)
 646                 return NULL;
 647         return (struct extent_inode_elem *)(uintptr_t)node->aux;
 648 }
 649
 650 /*
 651  * We maintain three separate rbtrees: one for direct refs, one for
 652  * indirect refs which have a key, and one for indirect refs which do not
 653  * have a key. Each tree does merge on insertion.
 654  *
 655  * Once all of the references are located, we iterate over the tree of
 656  * indirect refs with missing keys. An appropriate key is located and
 657  * the ref is moved onto the tree for indirect refs. After all missing
 658  * keys are thus located, we iterate over the indirect ref tree, resolve
 659  * each reference, and then insert the resolved reference onto the
 660  * direct tree (merging there too).
 661  *
 662  * New backrefs (i.e., for parent nodes) are added to the appropriate
 663  * rbtree as they are encountered. The new backrefs are subsequently
 664  * resolved as above.
 665  */
 666 static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 667                                  struct btrfs_path *path, u64 time_seq,
 668                                  struct preftrees *preftrees,
 669                                  const u64 *extent_item_pos,
 670                                  struct share_check *sc, bool ignore_offset)
 671 {
 672         int err;
 673         int ret = 0;
 674         struct ulist *parents;
 675         struct ulist_node *node;
 676         struct ulist_iterator uiter;
 677         struct rb_node *rnode;
 678
 679         parents = ulist_alloc(GFP_NOFS);
 680         if (!parents)
 681                 return -ENOMEM;
 682
 683         /*
 684          * We could trade memory usage for performance here by iterating
 685          * the tree, allocating new refs for each insertion, and then
 686          * freeing the entire indirect tree when we're done.  In some test
 687          * cases, the tree can grow quite large (~200k objects).
 688          */
 689         while ((rnode = rb_first_cached(&preftrees->indirect.root))) {
 690                 struct prelim_ref *ref;
 691
 692                 ref = rb_entry(rnode, struct prelim_ref, rbnode);
 693                 if (WARN(ref->parent,
 694                          "BUG: direct ref found in indirect tree")) {
 695                         ret = -EINVAL;
 696                         goto out;
 697                 }
 698
 699                 rb_erase_cached(&ref->rbnode, &preftrees->indirect.root);
 700                 preftrees->indirect.count--;
 701
 702                 if (ref->count == 0) {
 703                         free_pref(ref);
 704                         continue;
 705                 }
 706
 707                 if (sc && sc->root_objectid &&
 708                     ref->root_id != sc->root_objectid) {
 709                         free_pref(ref);
 710                         ret = BACKREF_FOUND_SHARED;
 711                         goto out;
 712                 }
 713                 err = resolve_indirect_ref(fs_info, path, time_seq, preftrees,
 714                                            ref, parents, extent_item_pos,
 715                                            ignore_offset);
 716                 /*
 717                  * we can only tolerate ENOENT,otherwise,we should catch error
 718                  * and return directly.
 719                  */
 720                 if (err == -ENOENT) {
 721                         prelim_ref_insert(fs_info, &preftrees->direct, ref,
 722                                           NULL);
 723                         continue;
 724                 } else if (err) {
 725                         free_pref(ref);
 726                         ret = err;
 727                         goto out;
 728                 }
 729
 730                 /* we put the first parent into the ref at hand */
 731                 ULIST_ITER_INIT(&uiter);
 732                 node = ulist_next(parents, &uiter);
 733                 ref->parent = node ? node->val : 0;
 734                 ref->inode_list = unode_aux_to_inode_list(node);
 735
 736                 /* Add a prelim_ref(s) for any other parent(s). */
 737                 while ((node = ulist_next(parents, &uiter))) {
 738                         struct prelim_ref *new_ref;
 739
 740                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
 741                                                    GFP_NOFS);
 742                         if (!new_ref) {
 743                                 free_pref(ref);
 744                                 ret = -ENOMEM;
 745                                 goto out;
 746                         }
 747                         memcpy(new_ref, ref, sizeof(*ref));
 748                         new_ref->parent = node->val;
 749                         new_ref->inode_list = unode_aux_to_inode_list(node);
 750                         prelim_ref_insert(fs_info, &preftrees->direct,
 751                                           new_ref, NULL);
 752                 }
 753
 754                 /*
 755                  * Now it's a direct ref, put it in the direct tree. We must
 756                  * do this last because the ref could be merged/freed here.
 757                  */
 758                 prelim_ref_insert(fs_info, &preftrees->direct, ref, NULL);
 759
 760                 ulist_reinit(parents);
 761                 cond_resched();
 762         }
 763 out:
 764         ulist_free(parents);
 765         return ret;
 766 }
 767
 768 /*
 769  * read tree blocks and add keys where required.
 770  */
 771 static int add_missing_keys(struct btrfs_fs_info *fs_info,
 772                             struct preftrees *preftrees, bool lock)
 773 {
 774         struct prelim_ref *ref;
 775         struct extent_buffer *eb;
 776         struct preftree *tree = &preftrees->indirect_missing_keys;
 777         struct rb_node *node;
 778
 779         while ((node = rb_first_cached(&tree->root))) {
 780                 ref = rb_entry(node, struct prelim_ref, rbnode);
 781                 rb_erase_cached(node, &tree->root);
 782
 783                 BUG_ON(ref->parent);    /* should not be a direct ref */
 784                 BUG_ON(ref->key_for_search.type);
 785                 BUG_ON(!ref->wanted_disk_byte);
 786
 787                 eb = read_tree_block(fs_info, ref->wanted_disk_byte,
 788                                      ref->root_id, 0, ref->level - 1, NULL);
 789                 if (IS_ERR(eb)) {
 790                         free_pref(ref);
 791                         return PTR_ERR(eb);
 792                 }
 793                 if (!extent_buffer_uptodate(eb)) {
 794                         free_pref(ref);
 795                         free_extent_buffer(eb);
 796                         return -EIO;
 797                 }
 798
 799                 if (lock)
 800                         btrfs_tree_read_lock(eb);
 801                 if (btrfs_header_level(eb) == 0)
 802                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 803                 else
 804                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 805                 if (lock)
 806                         btrfs_tree_read_unlock(eb);
 807                 free_extent_buffer(eb);
 808                 prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
 809                 cond_resched();
 810         }
 811         return 0;
 812 }
 813
 814 /*
 815  * add all currently queued delayed refs from this head whose seq nr is
 816  * smaller or equal that seq to the list
 817  */
 818 static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
 819                             struct btrfs_delayed_ref_head *head, u64 seq,
 820                             struct preftrees *preftrees, struct share_check *sc)
 821 {
 822         struct btrfs_delayed_ref_node *node;
 823         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 824         struct btrfs_key key;
 825         struct btrfs_key tmp_op_key;
 826         struct rb_node *n;
 827         int count;
 828         int ret = 0;
 829
 830         if (extent_op && extent_op->update_key)
 831                 btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
 832
 833         spin_lock(&head->lock);
 834         for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
 835                 node = rb_entry(n, struct btrfs_delayed_ref_node,
 836                                 ref_node);
 837                 if (node->seq > seq)
 838                         continue;
 839
 840                 switch (node->action) {
 841                 case BTRFS_ADD_DELAYED_EXTENT:
 842                 case BTRFS_UPDATE_DELAYED_HEAD:
 843                         WARN_ON(1);
 844                         continue;
 845                 case BTRFS_ADD_DELAYED_REF:
 846                         count = node->ref_mod;
 847                         break;
 848                 case BTRFS_DROP_DELAYED_REF:
 849                         count = node->ref_mod * -1;
 850                         break;
 851                 default:
 852                         BUG();
 853                 }
 854                 switch (node->type) {
 855                 case BTRFS_TREE_BLOCK_REF_KEY: {
 856                         /* NORMAL INDIRECT METADATA backref */
 857                         struct btrfs_delayed_tree_ref *ref;
 858
 859                         ref = btrfs_delayed_node_to_tree_ref(node);
 860                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
 861                                                &tmp_op_key, ref->level + 1,
 862                                                node->bytenr, count, sc,
 863                                                GFP_ATOMIC);
 864                         break;
 865                 }
 866                 case BTRFS_SHARED_BLOCK_REF_KEY: {
 867                         /* SHARED DIRECT METADATA backref */
 868                         struct btrfs_delayed_tree_ref *ref;
 869
 870                         ref = btrfs_delayed_node_to_tree_ref(node);
 871
 872                         ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
 873                                              ref->parent, node->bytenr, count,
 874                                              sc, GFP_ATOMIC);
 875                         break;
 876                 }
 877                 case BTRFS_EXTENT_DATA_REF_KEY: {
 878                         /* NORMAL INDIRECT DATA backref */
 879                         struct btrfs_delayed_data_ref *ref;
 880                         ref = btrfs_delayed_node_to_data_ref(node);
 881
 882                         key.objectid = ref->objectid;
 883                         key.type = BTRFS_EXTENT_DATA_KEY;
 884                         key.offset = ref->offset;
 885
 886                         /*
 887                          * Found a inum that doesn't match our known inum, we
 888                          * know it's shared.
 889                          */
 890                         if (sc && sc->inum && ref->objectid != sc->inum) {
 891                                 ret = BACKREF_FOUND_SHARED;
 892                                 goto out;
 893                         }
 894
 895                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
 896                                                &key, 0, node->bytenr, count, sc,
 897                                                GFP_ATOMIC);
 898                         break;
 899                 }
 900                 case BTRFS_SHARED_DATA_REF_KEY: {
 901                         /* SHARED DIRECT FULL backref */
 902                         struct btrfs_delayed_data_ref *ref;
 903
 904                         ref = btrfs_delayed_node_to_data_ref(node);
 905
 906                         ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
 907                                              node->bytenr, count, sc,
 908                                              GFP_ATOMIC);
 909                         break;
 910                 }
 911                 default:
 912                         WARN_ON(1);
 913                 }
 914                 /*
 915                  * We must ignore BACKREF_FOUND_SHARED until all delayed
 916                  * refs have been checked.
 917                  */
 918                 if (ret && (ret != BACKREF_FOUND_SHARED))
 919                         break;
 920         }
 921         if (!ret)
 922                 ret = extent_is_shared(sc);
 923 out:
 924         spin_unlock(&head->lock);
 925         return ret;
 926 }
 927
 928 /*
 929  * add all inline backrefs for bytenr to the list
 930  *
 931  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
 932  */
 933 static int add_inline_refs(const struct btrfs_fs_info *fs_info,
 934                            struct btrfs_path *path, u64 bytenr,
 935                            int *info_level, struct preftrees *preftrees,
 936                            struct share_check *sc)
 937 {
 938         int ret = 0;
 939         int slot;
 940         struct extent_buffer *leaf;
 941         struct btrfs_key key;
 942         struct btrfs_key found_key;
 943         unsigned long ptr;
 944         unsigned long end;
 945         struct btrfs_extent_item *ei;
 946         u64 flags;
 947         u64 item_size;
 948
 949         /*
 950          * enumerate all inline refs
 951          */
 952         leaf = path->nodes[0];
 953         slot = path->slots[0];
 954
 955         item_size = btrfs_item_size(leaf, slot);
 956         BUG_ON(item_size < sizeof(*ei));
 957
 958         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 959         flags = btrfs_extent_flags(leaf, ei);
 960         btrfs_item_key_to_cpu(leaf, &found_key, slot);
 961
 962         ptr = (unsigned long)(ei + 1);
 963         end = (unsigned long)ei + item_size;
 964
 965         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
 966             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 967                 struct btrfs_tree_block_info *info;
 968
 969                 info = (struct btrfs_tree_block_info *)ptr;
 970                 *info_level = btrfs_tree_block_level(leaf, info);
 971                 ptr += sizeof(struct btrfs_tree_block_info);
 972                 BUG_ON(ptr > end);
 973         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
 974                 *info_level = found_key.offset;
 975         } else {
 976                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 977         }
 978
 979         while (ptr < end) {
 980                 struct btrfs_extent_inline_ref *iref;
 981                 u64 offset;
 982                 int type;
 983
 984                 iref = (struct btrfs_extent_inline_ref *)ptr;
 985                 type = btrfs_get_extent_inline_ref_type(leaf, iref,
 986                                                         BTRFS_REF_TYPE_ANY);
 987                 if (type == BTRFS_REF_TYPE_INVALID)
 988                         return -EUCLEAN;
 989
 990                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
 991
 992                 switch (type) {
 993                 case BTRFS_SHARED_BLOCK_REF_KEY:
 994                         ret = add_direct_ref(fs_info, preftrees,
 995                                              *info_level + 1, offset,
 996                                              bytenr, 1, NULL, GFP_NOFS);
 997                         break;
 998                 case BTRFS_SHARED_DATA_REF_KEY: {
 999                         struct btrfs_shared_data_ref *sdref;
1000                         int count;
1001
1002                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
1003                         count = btrfs_shared_data_ref_count(leaf, sdref);
1004
1005                         ret = add_direct_ref(fs_info, preftrees, 0, offset,
1006                                              bytenr, count, sc, GFP_NOFS);
1007                         break;
1008                 }
1009                 case BTRFS_TREE_BLOCK_REF_KEY:
1010                         ret = add_indirect_ref(fs_info, preftrees, offset,
1011                                                NULL, *info_level + 1,
1012                                                bytenr, 1, NULL, GFP_NOFS);
1013                         break;
1014                 case BTRFS_EXTENT_DATA_REF_KEY: {
1015                         struct btrfs_extent_data_ref *dref;
1016                         int count;
1017                         u64 root;
1018
1019                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
1020                         count = btrfs_extent_data_ref_count(leaf, dref);
1021                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1022                                                                       dref);
1023                         key.type = BTRFS_EXTENT_DATA_KEY;
1024                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1025
1026                         if (sc && sc->inum && key.objectid != sc->inum) {
1027                                 ret = BACKREF_FOUND_SHARED;
1028                                 break;
1029                         }
1030
1031                         root = btrfs_extent_data_ref_root(leaf, dref);
1032
1033                         ret = add_indirect_ref(fs_info, preftrees, root,
1034                                                &key, 0, bytenr, count,
1035                                                sc, GFP_NOFS);
1036                         break;
1037                 }
1038                 default:
1039                         WARN_ON(1);
1040                 }
1041                 if (ret)
1042                         return ret;
1043                 ptr += btrfs_extent_inline_ref_size(type);
1044         }
1045
1046         return 0;
1047 }
1048
1049 /*
1050  * add all non-inline backrefs for bytenr to the list
1051  *
1052  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
1053  */
1054 static int add_keyed_refs(struct btrfs_root *extent_root,
1055                           struct btrfs_path *path, u64 bytenr,
1056                           int info_level, struct preftrees *preftrees,
1057                           struct share_check *sc)
1058 {
1059         struct btrfs_fs_info *fs_info = extent_root->fs_info;
1060         int ret;
1061         int slot;
1062         struct extent_buffer *leaf;
1063         struct btrfs_key key;
1064
1065         while (1) {
1066                 ret = btrfs_next_item(extent_root, path);
1067                 if (ret < 0)
1068                         break;
1069                 if (ret) {
1070                         ret = 0;
1071                         break;
1072                 }
1073
1074                 slot = path->slots[0];
1075                 leaf = path->nodes[0];
1076                 btrfs_item_key_to_cpu(leaf, &key, slot);
1077
1078                 if (key.objectid != bytenr)
1079                         break;
1080                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
1081                         continue;
1082                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
1083                         break;
1084
1085                 switch (key.type) {
1086                 case BTRFS_SHARED_BLOCK_REF_KEY:
1087                         /* SHARED DIRECT METADATA backref */
1088                         ret = add_direct_ref(fs_info, preftrees,
1089                                              info_level + 1, key.offset,
1090                                              bytenr, 1, NULL, GFP_NOFS);
1091                         break;
1092                 case BTRFS_SHARED_DATA_REF_KEY: {
1093                         /* SHARED DIRECT FULL backref */
1094                         struct btrfs_shared_data_ref *sdref;
1095                         int count;
1096
1097                         sdref = btrfs_item_ptr(leaf, slot,
1098                                               struct btrfs_shared_data_ref);
1099                         count = btrfs_shared_data_ref_count(leaf, sdref);
1100                         ret = add_direct_ref(fs_info, preftrees, 0,
1101                                              key.offset, bytenr, count,
1102                                              sc, GFP_NOFS);
1103                         break;
1104                 }
1105                 case BTRFS_TREE_BLOCK_REF_KEY:
1106                         /* NORMAL INDIRECT METADATA backref */
1107                         ret = add_indirect_ref(fs_info, preftrees, key.offset,
1108                                                NULL, info_level + 1, bytenr,
1109                                                1, NULL, GFP_NOFS);
1110                         break;
1111                 case BTRFS_EXTENT_DATA_REF_KEY: {
1112                         /* NORMAL INDIRECT DATA backref */
1113                         struct btrfs_extent_data_ref *dref;
1114                         int count;
1115                         u64 root;
1116
1117                         dref = btrfs_item_ptr(leaf, slot,
1118                                               struct btrfs_extent_data_ref);
1119                         count = btrfs_extent_data_ref_count(leaf, dref);
1120                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1121                                                                       dref);
1122                         key.type = BTRFS_EXTENT_DATA_KEY;
1123                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1124
1125                         if (sc && sc->inum && key.objectid != sc->inum) {
1126                                 ret = BACKREF_FOUND_SHARED;
1127                                 break;
1128                         }
1129
1130                         root = btrfs_extent_data_ref_root(leaf, dref);
1131                         ret = add_indirect_ref(fs_info, preftrees, root,
1132                                                &key, 0, bytenr, count,
1133                                                sc, GFP_NOFS);
1134                         break;
1135                 }
1136                 default:
1137                         WARN_ON(1);
1138                 }
1139                 if (ret)
1140                         return ret;
1141
1142         }
1143
1144         return ret;
1145 }
1146
1147 /*
1148  * this adds all existing backrefs (inline backrefs, backrefs and delayed
1149  * refs) for the given bytenr to the refs list, merges duplicates and resolves
1150  * indirect refs to their parent bytenr.
1151  * When roots are found, they're added to the roots list
1152  *
1153  * If time_seq is set to BTRFS_SEQ_LAST, it will not search delayed_refs, and
1154  * behave much like trans == NULL case, the difference only lies in it will not
1155  * commit root.
1156  * The special case is for qgroup to search roots in commit_transaction().
1157  *
1158  * @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a
1159  * shared extent is detected.
1160  *
1161  * Otherwise this returns 0 for success and <0 for an error.
1162  *
1163  * If ignore_offset is set to false, only extent refs whose offsets match
1164  * extent_item_pos are returned.  If true, every extent ref is returned
1165  * and extent_item_pos is ignored.
1166  *
1167  * FIXME some caching might speed things up
1168  */
1169 static int find_parent_nodes(struct btrfs_trans_handle *trans,
1170                              struct btrfs_fs_info *fs_info, u64 bytenr,
1171                              u64 time_seq, struct ulist *refs,
1172                              struct ulist *roots, const u64 *extent_item_pos,
1173                              struct share_check *sc, bool ignore_offset)
1174 {
1175         struct btrfs_root *root = btrfs_extent_root(fs_info, bytenr);
1176         struct btrfs_key key;
1177         struct btrfs_path *path;
1178         struct btrfs_delayed_ref_root *delayed_refs = NULL;
1179         struct btrfs_delayed_ref_head *head;
1180         int info_level = 0;
1181         int ret;
1182         struct prelim_ref *ref;
1183         struct rb_node *node;
1184         struct extent_inode_elem *eie = NULL;
1185         struct preftrees preftrees = {
1186                 .direct = PREFTREE_INIT,
1187                 .indirect = PREFTREE_INIT,
1188                 .indirect_missing_keys = PREFTREE_INIT
1189         };
1190
1191         key.objectid = bytenr;
1192         key.offset = (u64)-1;
1193         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1194                 key.type = BTRFS_METADATA_ITEM_KEY;
1195         else
1196                 key.type = BTRFS_EXTENT_ITEM_KEY;
1197
1198         path = btrfs_alloc_path();
1199         if (!path)
1200                 return -ENOMEM;
1201         if (!trans) {
1202                 path->search_commit_root = 1;
1203                 path->skip_locking = 1;
1204         }
1205
1206         if (time_seq == BTRFS_SEQ_LAST)
1207                 path->skip_locking = 1;
1208
1209 again:
1210         head = NULL;
1211
1212         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1213         if (ret < 0)
1214                 goto out;
1215         if (ret == 0) {
1216                 /* This shouldn't happen, indicates a bug or fs corruption. */
1217                 ASSERT(ret != 0);
1218                 ret = -EUCLEAN;
1219                 goto out;
1220         }
1221
1222         if (trans && likely(trans->type != __TRANS_DUMMY) &&
1223             time_seq != BTRFS_SEQ_LAST) {
1224                 /*
1225                  * We have a specific time_seq we care about and trans which
1226                  * means we have the path lock, we need to grab the ref head and
1227                  * lock it so we have a consistent view of the refs at the given
1228                  * time.
1229                  */
1230                 delayed_refs = &trans->transaction->delayed_refs;
1231                 spin_lock(&delayed_refs->lock);
1232                 head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
1233                 if (head) {
1234                         if (!mutex_trylock(&head->mutex)) {
1235                                 refcount_inc(&head->refs);
1236                                 spin_unlock(&delayed_refs->lock);
1237
1238                                 btrfs_release_path(path);
1239
1240                                 /*
1241                                  * Mutex was contended, block until it's
1242                                  * released and try again
1243                                  */
1244                                 mutex_lock(&head->mutex);
1245                                 mutex_unlock(&head->mutex);
1246                                 btrfs_put_delayed_ref_head(head);
1247                                 goto again;
1248                         }
1249                         spin_unlock(&delayed_refs->lock);
1250                         ret = add_delayed_refs(fs_info, head, time_seq,
1251                                                &preftrees, sc);
1252                         mutex_unlock(&head->mutex);
1253                         if (ret)
1254                                 goto out;
1255                 } else {
1256                         spin_unlock(&delayed_refs->lock);
1257                 }
1258         }
1259
1260         if (path->slots[0]) {
1261                 struct extent_buffer *leaf;
1262                 int slot;
1263
1264                 path->slots[0]--;
1265                 leaf = path->nodes[0];
1266                 slot = path->slots[0];
1267                 btrfs_item_key_to_cpu(leaf, &key, slot);
1268                 if (key.objectid == bytenr &&
1269                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
1270                      key.type == BTRFS_METADATA_ITEM_KEY)) {
1271                         ret = add_inline_refs(fs_info, path, bytenr,
1272                                               &info_level, &preftrees, sc);
1273                         if (ret)
1274                                 goto out;
1275                         ret = add_keyed_refs(root, path, bytenr, info_level,
1276                                              &preftrees, sc);
1277                         if (ret)
1278                                 goto out;
1279                 }
1280         }
1281
1282         btrfs_release_path(path);
1283
1284         ret = add_missing_keys(fs_info, &preftrees, path->skip_locking == 0);
1285         if (ret)
1286                 goto out;
1287
1288         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
1289
1290         ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
1291                                     extent_item_pos, sc, ignore_offset);
1292         if (ret)
1293                 goto out;
1294
1295         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
1296
1297         /*
1298          * This walks the tree of merged and resolved refs. Tree blocks are
1299          * read in as needed. Unique entries are added to the ulist, and
1300          * the list of found roots is updated.
1301          *
1302          * We release the entire tree in one go before returning.
1303          */
1304         node = rb_first_cached(&preftrees.direct.root);
1305         while (node) {
1306                 ref = rb_entry(node, struct prelim_ref, rbnode);
1307                 node = rb_next(&ref->rbnode);
1308                 /*
1309                  * ref->count < 0 can happen here if there are delayed
1310                  * refs with a node->action of BTRFS_DROP_DELAYED_REF.
1311                  * prelim_ref_insert() relies on this when merging
1312                  * identical refs to keep the overall count correct.
1313                  * prelim_ref_insert() will merge only those refs
1314                  * which compare identically.  Any refs having
1315                  * e.g. different offsets would not be merged,
1316                  * and would retain their original ref->count < 0.
1317                  */
1318                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1319                         if (sc && sc->root_objectid &&
1320                             ref->root_id != sc->root_objectid) {
1321                                 ret = BACKREF_FOUND_SHARED;
1322                                 goto out;
1323                         }
1324
1325                         /* no parent == root of tree */
1326                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1327                         if (ret < 0)
1328                                 goto out;
1329                 }
1330                 if (ref->count && ref->parent) {
1331                         if (extent_item_pos && !ref->inode_list &&
1332                             ref->level == 0) {
1333                                 struct extent_buffer *eb;
1334
1335                                 eb = read_tree_block(fs_info, ref->parent, 0,
1336                                                      0, ref->level, NULL);
1337                                 if (IS_ERR(eb)) {
1338                                         ret = PTR_ERR(eb);
1339                                         goto out;
1340                                 }
1341                                 if (!extent_buffer_uptodate(eb)) {
1342                                         free_extent_buffer(eb);
1343                                         ret = -EIO;
1344                                         goto out;
1345                                 }
1346
1347                                 if (!path->skip_locking)
1348                                         btrfs_tree_read_lock(eb);
1349                                 ret = find_extent_in_eb(eb, bytenr,
1350                                                         *extent_item_pos, &eie, ignore_offset);
1351                                 if (!path->skip_locking)
1352                                         btrfs_tree_read_unlock(eb);
1353                                 free_extent_buffer(eb);
1354                                 if (ret < 0)
1355                                         goto out;
1356                                 ref->inode_list = eie;
1357                         }
1358                         ret = ulist_add_merge_ptr(refs, ref->parent,
1359                                                   ref->inode_list,
1360                                                   (void **)&eie, GFP_NOFS);
1361                         if (ret < 0)
1362                                 goto out;
1363                         if (!ret && extent_item_pos) {
1364                                 /*
1365                                  * We've recorded that parent, so we must extend
1366                                  * its inode list here.
1367                                  *
1368                                  * However if there was corruption we may not
1369                                  * have found an eie, return an error in this
1370                                  * case.
1371                                  */
1372                                 ASSERT(eie);
1373                                 if (!eie) {
1374                                         ret = -EUCLEAN;
1375                                         goto out;
1376                                 }
1377                                 while (eie->next)
1378                                         eie = eie->next;
1379                                 eie->next = ref->inode_list;
1380                         }
1381                         eie = NULL;
1382                 }
1383                 cond_resched();
1384         }
1385
1386 out:
1387         btrfs_free_path(path);
1388
1389         prelim_release(&preftrees.direct);
1390         prelim_release(&preftrees.indirect);
1391         prelim_release(&preftrees.indirect_missing_keys);
1392
1393         if (ret < 0)
1394                 free_inode_elem_list(eie);
1395         return ret;
1396 }
1397
1398 static void free_leaf_list(struct ulist *blocks)
1399 {
1400         struct ulist_node *node = NULL;
1401         struct extent_inode_elem *eie;
1402         struct ulist_iterator uiter;
1403
1404         ULIST_ITER_INIT(&uiter);
1405         while ((node = ulist_next(blocks, &uiter))) {
1406                 if (!node->aux)
1407                         continue;
1408                 eie = unode_aux_to_inode_list(node);
1409                 free_inode_elem_list(eie);
1410                 node->aux = 0;
1411         }
1412
1413         ulist_free(blocks);
1414 }
1415
1416 /*
1417  * Finds all leafs with a reference to the specified combination of bytenr and
1418  * offset. key_list_head will point to a list of corresponding keys (caller must
1419  * free each list element). The leafs will be stored in the leafs ulist, which
1420  * must be freed with ulist_free.
1421  *
1422  * returns 0 on success, <0 on error
1423  */
1424 int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1425                          struct btrfs_fs_info *fs_info, u64 bytenr,
1426                          u64 time_seq, struct ulist **leafs,
1427                          const u64 *extent_item_pos, bool ignore_offset)
1428 {
1429         int ret;
1430
1431         *leafs = ulist_alloc(GFP_NOFS);
1432         if (!*leafs)
1433                 return -ENOMEM;
1434
1435         ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1436                                 *leafs, NULL, extent_item_pos, NULL, ignore_offset);
1437         if (ret < 0 && ret != -ENOENT) {
1438                 free_leaf_list(*leafs);
1439                 return ret;
1440         }
1441
1442         return 0;
1443 }
1444
1445 /*
1446  * walk all backrefs for a given extent to find all roots that reference this
1447  * extent. Walking a backref means finding all extents that reference this
1448  * extent and in turn walk the backrefs of those, too. Naturally this is a
1449  * recursive process, but here it is implemented in an iterative fashion: We
1450  * find all referencing extents for the extent in question and put them on a
1451  * list. In turn, we find all referencing extents for those, further appending
1452  * to the list. The way we iterate the list allows adding more elements after
1453  * the current while iterating. The process stops when we reach the end of the
1454  * list. Found roots are added to the roots list.
1455  *
1456  * returns 0 on success, < 0 on error.
1457  */
1458 static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
1459                                      struct btrfs_fs_info *fs_info, u64 bytenr,
1460                                      u64 time_seq, struct ulist **roots,
1461                                      bool ignore_offset)
1462 {
1463         struct ulist *tmp;
1464         struct ulist_node *node = NULL;
1465         struct ulist_iterator uiter;
1466         int ret;
1467
1468         tmp = ulist_alloc(GFP_NOFS);
1469         if (!tmp)
1470                 return -ENOMEM;
1471         *roots = ulist_alloc(GFP_NOFS);
1472         if (!*roots) {
1473                 ulist_free(tmp);
1474                 return -ENOMEM;
1475         }
1476
1477         ULIST_ITER_INIT(&uiter);
1478         while (1) {
1479                 ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1480                                         tmp, *roots, NULL, NULL, ignore_offset);
1481                 if (ret < 0 && ret != -ENOENT) {
1482                         ulist_free(tmp);
1483                         ulist_free(*roots);
1484                         *roots = NULL;
1485                         return ret;
1486                 }
1487                 node = ulist_next(tmp, &uiter);
1488                 if (!node)
1489                         break;
1490                 bytenr = node->val;
1491                 cond_resched();
1492         }
1493
1494         ulist_free(tmp);
1495         return 0;
1496 }
1497
1498 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1499                          struct btrfs_fs_info *fs_info, u64 bytenr,
1500                          u64 time_seq, struct ulist **roots,
1501                          bool skip_commit_root_sem)
1502 {
1503         int ret;
1504
1505         if (!trans && !skip_commit_root_sem)
1506                 down_read(&fs_info->commit_root_sem);
1507         ret = btrfs_find_all_roots_safe(trans, fs_info, bytenr,
1508                                         time_seq, roots, false);
1509         if (!trans && !skip_commit_root_sem)
1510                 up_read(&fs_info->commit_root_sem);
1511         return ret;
1512 }
1513
1514 /*
1515  * The caller has joined a transaction or is holding a read lock on the
1516  * fs_info->commit_root_sem semaphore, so no need to worry about the root's last
1517  * snapshot field changing while updating or checking the cache.
1518  */
1519 static bool lookup_backref_shared_cache(struct btrfs_backref_shared_cache *cache,
1520                                         struct btrfs_root *root,
1521                                         u64 bytenr, int level, bool *is_shared)
1522 {
1523         struct btrfs_backref_shared_cache_entry *entry;
1524
1525         if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
1526                 return false;
1527
1528         /*
1529          * Level -1 is used for the data extent, which is not reliable to cache
1530          * because its reference count can increase or decrease without us
1531          * realizing. We cache results only for extent buffers that lead from
1532          * the root node down to the leaf with the file extent item.
1533          */
1534         ASSERT(level >= 0);
1535
1536         entry = &cache->entries[level];
1537
1538         /* Unused cache entry or being used for some other extent buffer. */
1539         if (entry->bytenr != bytenr)
1540                 return false;
1541
1542         /*
1543          * We cached a false result, but the last snapshot generation of the
1544          * root changed, so we now have a snapshot. Don't trust the result.
1545          */
1546         if (!entry->is_shared &&
1547             entry->gen != btrfs_root_last_snapshot(&root->root_item))
1548                 return false;
1549
1550         /*
1551          * If we cached a true result and the last generation used for dropping
1552          * a root changed, we can not trust the result, because the dropped root
1553          * could be a snapshot sharing this extent buffer.
1554          */
1555         if (entry->is_shared &&
1556             entry->gen != btrfs_get_last_root_drop_gen(root->fs_info))
1557                 return false;
1558
1559         *is_shared = entry->is_shared;
1560
1561         return true;
1562 }
1563
1564 /*
1565  * The caller has joined a transaction or is holding a read lock on the
1566  * fs_info->commit_root_sem semaphore, so no need to worry about the root's last
1567  * snapshot field changing while updating or checking the cache.
1568  */
1569 static void store_backref_shared_cache(struct btrfs_backref_shared_cache *cache,
1570                                        struct btrfs_root *root,
1571                                        u64 bytenr, int level, bool is_shared)
1572 {
1573         struct btrfs_backref_shared_cache_entry *entry;
1574         u64 gen;
1575
1576         if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
1577                 return;
1578
1579         /*
1580          * Level -1 is used for the data extent, which is not reliable to cache
1581          * because its reference count can increase or decrease without us
1582          * realizing. We cache results only for extent buffers that lead from
1583          * the root node down to the leaf with the file extent item.
1584          */
1585         ASSERT(level >= 0);
1586
1587         if (is_shared)
1588                 gen = btrfs_get_last_root_drop_gen(root->fs_info);
1589         else
1590                 gen = btrfs_root_last_snapshot(&root->root_item);
1591
1592         entry = &cache->entries[level];
1593         entry->bytenr = bytenr;
1594         entry->is_shared = is_shared;
1595         entry->gen = gen;
1596
1597         /*
1598          * If we found an extent buffer is shared, set the cache result for all
1599          * extent buffers below it to true. As nodes in the path are COWed,
1600          * their sharedness is moved to their children, and if a leaf is COWed,
1601          * then the sharedness of a data extent becomes direct, the refcount of
1602          * data extent is increased in the extent item at the extent tree.
1603          */
1604         if (is_shared) {
1605                 for (int i = 0; i < level; i++) {
1606                         entry = &cache->entries[i];
1607                         entry->is_shared = is_shared;
1608                         entry->gen = gen;
1609                 }
1610         }
1611 }
1612
1613 /*
1614  * Check if a data extent is shared or not.
1615  *
1616  * @root:        The root the inode belongs to.
1617  * @inum:        Number of the inode whose extent we are checking.
1618  * @bytenr:      Logical bytenr of the extent we are checking.
1619  * @extent_gen:  Generation of the extent (file extent item) or 0 if it is
1620  *               not known.
1621  * @roots:       List of roots this extent is shared among.
1622  * @tmp:         Temporary list used for iteration.
1623  * @cache:       A backref lookup result cache.
1624  *
1625  * btrfs_is_data_extent_shared uses the backref walking code but will short
1626  * circuit as soon as it finds a root or inode that doesn't match the
1627  * one passed in. This provides a significant performance benefit for
1628  * callers (such as fiemap) which want to know whether the extent is
1629  * shared but do not need a ref count.
1630  *
1631  * This attempts to attach to the running transaction in order to account for
1632  * delayed refs, but continues on even when no running transaction exists.
1633  *
1634  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1635  */
1636 int btrfs_is_data_extent_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
1637                                 u64 extent_gen,
1638                                 struct ulist *roots, struct ulist *tmp,
1639                                 struct btrfs_backref_shared_cache *cache)
1640 {
1641         struct btrfs_fs_info *fs_info = root->fs_info;
1642         struct btrfs_trans_handle *trans;
1643         struct ulist_iterator uiter;
1644         struct ulist_node *node;
1645         struct btrfs_seq_list elem = BTRFS_SEQ_LIST_INIT(elem);
1646         int ret = 0;
1647         struct share_check shared = {
1648                 .root_objectid = root->root_key.objectid,
1649                 .inum = inum,
1650                 .share_count = 0,
1651         };
1652         int level;
1653
1654         ulist_init(roots);
1655         ulist_init(tmp);
1656
1657         trans = btrfs_join_transaction_nostart(root);
1658         if (IS_ERR(trans)) {
1659                 if (PTR_ERR(trans) != -ENOENT && PTR_ERR(trans) != -EROFS) {
1660                         ret = PTR_ERR(trans);
1661                         goto out;
1662                 }
1663                 trans = NULL;
1664                 down_read(&fs_info->commit_root_sem);
1665         } else {
1666                 btrfs_get_tree_mod_seq(fs_info, &elem);
1667         }
1668
1669         /* -1 means we are in the bytenr of the data extent. */
1670         level = -1;
1671         ULIST_ITER_INIT(&uiter);
1672         while (1) {
1673                 bool is_shared;
1674                 bool cached;
1675
1676                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1677                                         roots, NULL, &shared, false);
1678                 if (ret == BACKREF_FOUND_SHARED) {
1679                         /* this is the only condition under which we return 1 */
1680                         ret = 1;
1681                         if (level >= 0)
1682                                 store_backref_shared_cache(cache, root, bytenr,
1683                                                            level, true);
1684                         break;
1685                 }
1686                 if (ret < 0 && ret != -ENOENT)
1687                         break;
1688                 ret = 0;
1689                 /*
1690                  * If our data extent is not shared through reflinks and it was
1691                  * created in a generation after the last one used to create a
1692                  * snapshot of the inode's root, then it can not be shared
1693                  * indirectly through subtrees, as that can only happen with
1694                  * snapshots. In this case bail out, no need to check for the
1695                  * sharedness of extent buffers.
1696                  */
1697                 if (level == -1 &&
1698                     extent_gen > btrfs_root_last_snapshot(&root->root_item))
1699                         break;
1700
1701                 if (level >= 0)
1702                         store_backref_shared_cache(cache, root, bytenr,
1703                                                    level, false);
1704                 node = ulist_next(tmp, &uiter);
1705                 if (!node)
1706                         break;
1707                 bytenr = node->val;
1708                 level++;
1709                 cached = lookup_backref_shared_cache(cache, root, bytenr, level,
1710                                                      &is_shared);
1711                 if (cached) {
1712                         ret = (is_shared ? 1 : 0);
1713                         break;
1714                 }
1715                 shared.share_count = 0;
1716                 cond_resched();
1717         }
1718
1719         if (trans) {
1720                 btrfs_put_tree_mod_seq(fs_info, &elem);
1721                 btrfs_end_transaction(trans);
1722         } else {
1723                 up_read(&fs_info->commit_root_sem);
1724         }
1725 out:
1726         ulist_release(roots);
1727         ulist_release(tmp);
1728         return ret;
1729 }
1730
1731 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1732                           u64 start_off, struct btrfs_path *path,
1733                           struct btrfs_inode_extref **ret_extref,
1734                           u64 *found_off)
1735 {
1736         int ret, slot;
1737         struct btrfs_key key;
1738         struct btrfs_key found_key;
1739         struct btrfs_inode_extref *extref;
1740         const struct extent_buffer *leaf;
1741         unsigned long ptr;
1742
1743         key.objectid = inode_objectid;
1744         key.type = BTRFS_INODE_EXTREF_KEY;
1745         key.offset = start_off;
1746
1747         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1748         if (ret < 0)
1749                 return ret;
1750
1751         while (1) {
1752                 leaf = path->nodes[0];
1753                 slot = path->slots[0];
1754                 if (slot >= btrfs_header_nritems(leaf)) {
1755                         /*
1756                          * If the item at offset is not found,
1757                          * btrfs_search_slot will point us to the slot
1758                          * where it should be inserted. In our case
1759                          * that will be the slot directly before the
1760                          * next INODE_REF_KEY_V2 item. In the case
1761                          * that we're pointing to the last slot in a
1762                          * leaf, we must move one leaf over.
1763                          */
1764                         ret = btrfs_next_leaf(root, path);
1765                         if (ret) {
1766                                 if (ret >= 1)
1767                                         ret = -ENOENT;
1768                                 break;
1769                         }
1770                         continue;
1771                 }
1772
1773                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1774
1775                 /*
1776                  * Check that we're still looking at an extended ref key for
1777                  * this particular objectid. If we have different
1778                  * objectid or type then there are no more to be found
1779                  * in the tree and we can exit.
1780                  */
1781                 ret = -ENOENT;
1782                 if (found_key.objectid != inode_objectid)
1783                         break;
1784                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1785                         break;
1786
1787                 ret = 0;
1788                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1789                 extref = (struct btrfs_inode_extref *)ptr;
1790                 *ret_extref = extref;
1791                 if (found_off)
1792                         *found_off = found_key.offset;
1793                 break;
1794         }
1795
1796         return ret;
1797 }
1798
1799 /*
1800  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1801  * Elements of the path are separated by '/' and the path is guaranteed to be
1802  * 0-terminated. the path is only given within the current file system.
1803  * Therefore, it never starts with a '/'. the caller is responsible to provide
1804  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1805  * the start point of the resulting string is returned. this pointer is within
1806  * dest, normally.
1807  * in case the path buffer would overflow, the pointer is decremented further
1808  * as if output was written to the buffer, though no more output is actually
1809  * generated. that way, the caller can determine how much space would be
1810  * required for the path to fit into the buffer. in that case, the returned
1811  * value will be smaller than dest. callers must check this!
1812  */
1813 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1814                         u32 name_len, unsigned long name_off,
1815                         struct extent_buffer *eb_in, u64 parent,
1816                         char *dest, u32 size)
1817 {
1818         int slot;
1819         u64 next_inum;
1820         int ret;
1821         s64 bytes_left = ((s64)size) - 1;
1822         struct extent_buffer *eb = eb_in;
1823         struct btrfs_key found_key;
1824         struct btrfs_inode_ref *iref;
1825
1826         if (bytes_left >= 0)
1827                 dest[bytes_left] = '\0';
1828
1829         while (1) {
1830                 bytes_left -= name_len;
1831                 if (bytes_left >= 0)
1832                         read_extent_buffer(eb, dest + bytes_left,
1833                                            name_off, name_len);
1834                 if (eb != eb_in) {
1835                         if (!path->skip_locking)
1836                                 btrfs_tree_read_unlock(eb);
1837                         free_extent_buffer(eb);
1838                 }
1839                 ret = btrfs_find_item(fs_root, path, parent, 0,
1840                                 BTRFS_INODE_REF_KEY, &found_key);
1841                 if (ret > 0)
1842                         ret = -ENOENT;
1843                 if (ret)
1844                         break;
1845
1846                 next_inum = found_key.offset;
1847
1848                 /* regular exit ahead */
1849                 if (parent == next_inum)
1850                         break;
1851
1852                 slot = path->slots[0];
1853                 eb = path->nodes[0];
1854                 /* make sure we can use eb after releasing the path */
1855                 if (eb != eb_in) {
1856                         path->nodes[0] = NULL;
1857                         path->locks[0] = 0;
1858                 }
1859                 btrfs_release_path(path);
1860                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1861
1862                 name_len = btrfs_inode_ref_name_len(eb, iref);
1863                 name_off = (unsigned long)(iref + 1);
1864
1865                 parent = next_inum;
1866                 --bytes_left;
1867                 if (bytes_left >= 0)
1868                         dest[bytes_left] = '/';
1869         }
1870
1871         btrfs_release_path(path);
1872
1873         if (ret)
1874                 return ERR_PTR(ret);
1875
1876         return dest + bytes_left;
1877 }
1878
1879 /*
1880  * this makes the path point to (logical EXTENT_ITEM *)
1881  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1882  * tree blocks and <0 on error.
1883  */
1884 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1885                         struct btrfs_path *path, struct btrfs_key *found_key,
1886                         u64 *flags_ret)
1887 {
1888         struct btrfs_root *extent_root = btrfs_extent_root(fs_info, logical);
1889         int ret;
1890         u64 flags;
1891         u64 size = 0;
1892         u32 item_size;
1893         const struct extent_buffer *eb;
1894         struct btrfs_extent_item *ei;
1895         struct btrfs_key key;
1896
1897         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1898                 key.type = BTRFS_METADATA_ITEM_KEY;
1899         else
1900                 key.type = BTRFS_EXTENT_ITEM_KEY;
1901         key.objectid = logical;
1902         key.offset = (u64)-1;
1903
1904         ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
1905         if (ret < 0)
1906                 return ret;
1907
1908         ret = btrfs_previous_extent_item(extent_root, path, 0);
1909         if (ret) {
1910                 if (ret > 0)
1911                         ret = -ENOENT;
1912                 return ret;
1913         }
1914         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1915         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1916                 size = fs_info->nodesize;
1917         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1918                 size = found_key->offset;
1919
1920         if (found_key->objectid > logical ||
1921             found_key->objectid + size <= logical) {
1922                 btrfs_debug(fs_info,
1923                         "logical %llu is not within any extent", logical);
1924                 return -ENOENT;
1925         }
1926
1927         eb = path->nodes[0];
1928         item_size = btrfs_item_size(eb, path->slots[0]);
1929         BUG_ON(item_size < sizeof(*ei));
1930
1931         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1932         flags = btrfs_extent_flags(eb, ei);
1933
1934         btrfs_debug(fs_info,
1935                 "logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
1936                  logical, logical - found_key->objectid, found_key->objectid,
1937                  found_key->offset, flags, item_size);
1938
1939         WARN_ON(!flags_ret);
1940         if (flags_ret) {
1941                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1942                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1943                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1944                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1945                 else
1946                         BUG();
1947                 return 0;
1948         }
1949
1950         return -EIO;
1951 }
1952
1953 /*
1954  * helper function to iterate extent inline refs. ptr must point to a 0 value
1955  * for the first call and may be modified. it is used to track state.
1956  * if more refs exist, 0 is returned and the next call to
1957  * get_extent_inline_ref must pass the modified ptr parameter to get the
1958  * next ref. after the last ref was processed, 1 is returned.
1959  * returns <0 on error
1960  */
1961 static int get_extent_inline_ref(unsigned long *ptr,
1962                                  const struct extent_buffer *eb,
1963                                  const struct btrfs_key *key,
1964                                  const struct btrfs_extent_item *ei,
1965                                  u32 item_size,
1966                                  struct btrfs_extent_inline_ref **out_eiref,
1967                                  int *out_type)
1968 {
1969         unsigned long end;
1970         u64 flags;
1971         struct btrfs_tree_block_info *info;
1972
1973         if (!*ptr) {
1974                 /* first call */
1975                 flags = btrfs_extent_flags(eb, ei);
1976                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1977                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1978                                 /* a skinny metadata extent */
1979                                 *out_eiref =
1980                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1981                         } else {
1982                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1983                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1984                                 *out_eiref =
1985                                    (struct btrfs_extent_inline_ref *)(info + 1);
1986                         }
1987                 } else {
1988                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1989                 }
1990                 *ptr = (unsigned long)*out_eiref;
1991                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1992                         return -ENOENT;
1993         }
1994
1995         end = (unsigned long)ei + item_size;
1996         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1997         *out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
1998                                                      BTRFS_REF_TYPE_ANY);
1999         if (*out_type == BTRFS_REF_TYPE_INVALID)
2000                 return -EUCLEAN;
2001
2002         *ptr += btrfs_extent_inline_ref_size(*out_type);
2003         WARN_ON(*ptr > end);
2004         if (*ptr == end)
2005                 return 1; /* last */
2006
2007         return 0;
2008 }
2009
2010 /*
2011  * reads the tree block backref for an extent. tree level and root are returned
2012  * through out_level and out_root. ptr must point to a 0 value for the first
2013  * call and may be modified (see get_extent_inline_ref comment).
2014  * returns 0 if data was provided, 1 if there was no more data to provide or
2015  * <0 on error.
2016  */
2017 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
2018                             struct btrfs_key *key, struct btrfs_extent_item *ei,
2019                             u32 item_size, u64 *out_root, u8 *out_level)
2020 {
2021         int ret;
2022         int type;
2023         struct btrfs_extent_inline_ref *eiref;
2024
2025         if (*ptr == (unsigned long)-1)
2026                 return 1;
2027
2028         while (1) {
2029                 ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
2030                                               &eiref, &type);
2031                 if (ret < 0)
2032                         return ret;
2033
2034                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
2035                     type == BTRFS_SHARED_BLOCK_REF_KEY)
2036                         break;
2037
2038                 if (ret == 1)
2039                         return 1;
2040         }
2041
2042         /* we can treat both ref types equally here */
2043         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
2044
2045         if (key->type == BTRFS_EXTENT_ITEM_KEY) {
2046                 struct btrfs_tree_block_info *info;
2047
2048                 info = (struct btrfs_tree_block_info *)(ei + 1);
2049                 *out_level = btrfs_tree_block_level(eb, info);
2050         } else {
2051                 ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
2052                 *out_level = (u8)key->offset;
2053         }
2054
2055         if (ret == 1)
2056                 *ptr = (unsigned long)-1;
2057
2058         return 0;
2059 }
2060
2061 static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
2062                              struct extent_inode_elem *inode_list,
2063                              u64 root, u64 extent_item_objectid,
2064                              iterate_extent_inodes_t *iterate, void *ctx)
2065 {
2066         struct extent_inode_elem *eie;
2067         int ret = 0;
2068
2069         for (eie = inode_list; eie; eie = eie->next) {
2070                 btrfs_debug(fs_info,
2071                             "ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
2072                             extent_item_objectid, eie->inum,
2073                             eie->offset, root);
2074                 ret = iterate(eie->inum, eie->offset, root, ctx);
2075                 if (ret) {
2076                         btrfs_debug(fs_info,
2077                                     "stopping iteration for %llu due to ret=%d",
2078                                     extent_item_objectid, ret);
2079                         break;
2080                 }
2081         }
2082
2083         return ret;
2084 }
2085
2086 /*
2087  * calls iterate() for every inode that references the extent identified by
2088  * the given parameters.
2089  * when the iterator function returns a non-zero value, iteration stops.
2090  */
2091 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
2092                                 u64 extent_item_objectid, u64 extent_item_pos,
2093                                 int search_commit_root,
2094                                 iterate_extent_inodes_t *iterate, void *ctx,
2095                                 bool ignore_offset)
2096 {
2097         int ret;
2098         struct btrfs_trans_handle *trans = NULL;
2099         struct ulist *refs = NULL;
2100         struct ulist *roots = NULL;
2101         struct ulist_node *ref_node = NULL;
2102         struct ulist_node *root_node = NULL;
2103         struct btrfs_seq_list seq_elem = BTRFS_SEQ_LIST_INIT(seq_elem);
2104         struct ulist_iterator ref_uiter;
2105         struct ulist_iterator root_uiter;
2106
2107         btrfs_debug(fs_info, "resolving all inodes for extent %llu",
2108                         extent_item_objectid);
2109
2110         if (!search_commit_root) {
2111                 trans = btrfs_attach_transaction(fs_info->tree_root);
2112                 if (IS_ERR(trans)) {
2113                         if (PTR_ERR(trans) != -ENOENT &&
2114                             PTR_ERR(trans) != -EROFS)
2115                                 return PTR_ERR(trans);
2116                         trans = NULL;
2117                 }
2118         }
2119
2120         if (trans)
2121                 btrfs_get_tree_mod_seq(fs_info, &seq_elem);
2122         else
2123                 down_read(&fs_info->commit_root_sem);
2124
2125         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
2126                                    seq_elem.seq, &refs,
2127                                    &extent_item_pos, ignore_offset);
2128         if (ret)
2129                 goto out;
2130
2131         ULIST_ITER_INIT(&ref_uiter);
2132         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
2133                 ret = btrfs_find_all_roots_safe(trans, fs_info, ref_node->val,
2134                                                 seq_elem.seq, &roots,
2135                                                 ignore_offset);
2136                 if (ret)
2137                         break;
2138                 ULIST_ITER_INIT(&root_uiter);
2139                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
2140                         btrfs_debug(fs_info,
2141                                     "root %llu references leaf %llu, data list %#llx",
2142                                     root_node->val, ref_node->val,
2143                                     ref_node->aux);
2144                         ret = iterate_leaf_refs(fs_info,
2145                                                 (struct extent_inode_elem *)
2146                                                 (uintptr_t)ref_node->aux,
2147                                                 root_node->val,
2148                                                 extent_item_objectid,
2149                                                 iterate, ctx);
2150                 }
2151                 ulist_free(roots);
2152         }
2153
2154         free_leaf_list(refs);
2155 out:
2156         if (trans) {
2157                 btrfs_put_tree_mod_seq(fs_info, &seq_elem);
2158                 btrfs_end_transaction(trans);
2159         } else {
2160                 up_read(&fs_info->commit_root_sem);
2161         }
2162
2163         return ret;
2164 }
2165
2166 static int build_ino_list(u64 inum, u64 offset, u64 root, void *ctx)
2167 {
2168         struct btrfs_data_container *inodes = ctx;
2169         const size_t c = 3 * sizeof(u64);
2170
2171         if (inodes->bytes_left >= c) {
2172                 inodes->bytes_left -= c;
2173                 inodes->val[inodes->elem_cnt] = inum;
2174                 inodes->val[inodes->elem_cnt + 1] = offset;
2175                 inodes->val[inodes->elem_cnt + 2] = root;
2176                 inodes->elem_cnt += 3;
2177         } else {
2178                 inodes->bytes_missing += c - inodes->bytes_left;
2179                 inodes->bytes_left = 0;
2180                 inodes->elem_missed += 3;
2181         }
2182
2183         return 0;
2184 }
2185
2186 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
2187                                 struct btrfs_path *path,
2188                                 void *ctx, bool ignore_offset)
2189 {
2190         int ret;
2191         u64 extent_item_pos;
2192         u64 flags = 0;
2193         struct btrfs_key found_key;
2194         int search_commit_root = path->search_commit_root;
2195
2196         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
2197         btrfs_release_path(path);
2198         if (ret < 0)
2199                 return ret;
2200         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
2201                 return -EINVAL;
2202
2203         extent_item_pos = logical - found_key.objectid;
2204         ret = iterate_extent_inodes(fs_info, found_key.objectid,
2205                                         extent_item_pos, search_commit_root,
2206                                         build_ino_list, ctx, ignore_offset);
2207
2208         return ret;
2209 }
2210
2211 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2212                          struct extent_buffer *eb, struct inode_fs_paths *ipath);
2213
2214 static int iterate_inode_refs(u64 inum, struct inode_fs_paths *ipath)
2215 {
2216         int ret = 0;
2217         int slot;
2218         u32 cur;
2219         u32 len;
2220         u32 name_len;
2221         u64 parent = 0;
2222         int found = 0;
2223         struct btrfs_root *fs_root = ipath->fs_root;
2224         struct btrfs_path *path = ipath->btrfs_path;
2225         struct extent_buffer *eb;
2226         struct btrfs_inode_ref *iref;
2227         struct btrfs_key found_key;
2228
2229         while (!ret) {
2230                 ret = btrfs_find_item(fs_root, path, inum,
2231                                 parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
2232                                 &found_key);
2233
2234                 if (ret < 0)
2235                         break;
2236                 if (ret) {
2237                         ret = found ? 0 : -ENOENT;
2238                         break;
2239                 }
2240                 ++found;
2241
2242                 parent = found_key.offset;
2243                 slot = path->slots[0];
2244                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2245                 if (!eb) {
2246                         ret = -ENOMEM;
2247                         break;
2248                 }
2249                 btrfs_release_path(path);
2250
2251                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2252
2253                 for (cur = 0; cur < btrfs_item_size(eb, slot); cur += len) {
2254                         name_len = btrfs_inode_ref_name_len(eb, iref);
2255                         /* path must be released before calling iterate()! */
2256                         btrfs_debug(fs_root->fs_info,
2257                                 "following ref at offset %u for inode %llu in tree %llu",
2258                                 cur, found_key.objectid,
2259                                 fs_root->root_key.objectid);
2260                         ret = inode_to_path(parent, name_len,
2261                                       (unsigned long)(iref + 1), eb, ipath);
2262                         if (ret)
2263                                 break;
2264                         len = sizeof(*iref) + name_len;
2265                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
2266                 }
2267                 free_extent_buffer(eb);
2268         }
2269
2270         btrfs_release_path(path);
2271
2272         return ret;
2273 }
2274
2275 static int iterate_inode_extrefs(u64 inum, struct inode_fs_paths *ipath)
2276 {
2277         int ret;
2278         int slot;
2279         u64 offset = 0;
2280         u64 parent;
2281         int found = 0;
2282         struct btrfs_root *fs_root = ipath->fs_root;
2283         struct btrfs_path *path = ipath->btrfs_path;
2284         struct extent_buffer *eb;
2285         struct btrfs_inode_extref *extref;
2286         u32 item_size;
2287         u32 cur_offset;
2288         unsigned long ptr;
2289
2290         while (1) {
2291                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
2292                                             &offset);
2293                 if (ret < 0)
2294                         break;
2295                 if (ret) {
2296                         ret = found ? 0 : -ENOENT;
2297                         break;
2298                 }
2299                 ++found;
2300
2301                 slot = path->slots[0];
2302                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2303                 if (!eb) {
2304                         ret = -ENOMEM;
2305                         break;
2306                 }
2307                 btrfs_release_path(path);
2308
2309                 item_size = btrfs_item_size(eb, slot);
2310                 ptr = btrfs_item_ptr_offset(eb, slot);
2311                 cur_offset = 0;
2312
2313                 while (cur_offset < item_size) {
2314                         u32 name_len;
2315
2316                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
2317                         parent = btrfs_inode_extref_parent(eb, extref);
2318                         name_len = btrfs_inode_extref_name_len(eb, extref);
2319                         ret = inode_to_path(parent, name_len,
2320                                       (unsigned long)&extref->name, eb, ipath);
2321                         if (ret)
2322                                 break;
2323
2324                         cur_offset += btrfs_inode_extref_name_len(eb, extref);
2325                         cur_offset += sizeof(*extref);
2326                 }
2327                 free_extent_buffer(eb);
2328
2329                 offset++;
2330         }
2331
2332         btrfs_release_path(path);
2333
2334         return ret;
2335 }
2336
2337 /*
2338  * returns 0 if the path could be dumped (probably truncated)
2339  * returns <0 in case of an error
2340  */
2341 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2342                          struct extent_buffer *eb, struct inode_fs_paths *ipath)
2343 {
2344         char *fspath;
2345         char *fspath_min;
2346         int i = ipath->fspath->elem_cnt;
2347         const int s_ptr = sizeof(char *);
2348         u32 bytes_left;
2349
2350         bytes_left = ipath->fspath->bytes_left > s_ptr ?
2351                                         ipath->fspath->bytes_left - s_ptr : 0;
2352
2353         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
2354         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
2355                                    name_off, eb, inum, fspath_min, bytes_left);
2356         if (IS_ERR(fspath))
2357                 return PTR_ERR(fspath);
2358
2359         if (fspath > fspath_min) {
2360                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
2361                 ++ipath->fspath->elem_cnt;
2362                 ipath->fspath->bytes_left = fspath - fspath_min;
2363         } else {
2364                 ++ipath->fspath->elem_missed;
2365                 ipath->fspath->bytes_missing += fspath_min - fspath;
2366                 ipath->fspath->bytes_left = 0;
2367         }
2368
2369         return 0;
2370 }
2371
2372 /*
2373  * this dumps all file system paths to the inode into the ipath struct, provided
2374  * is has been created large enough. each path is zero-terminated and accessed
2375  * from ipath->fspath->val[i].
2376  * when it returns, there are ipath->fspath->elem_cnt number of paths available
2377  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
2378  * number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
2379  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
2380  * have been needed to return all paths.
2381  */
2382 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
2383 {
2384         int ret;
2385         int found_refs = 0;
2386
2387         ret = iterate_inode_refs(inum, ipath);
2388         if (!ret)
2389                 ++found_refs;
2390         else if (ret != -ENOENT)
2391                 return ret;
2392
2393         ret = iterate_inode_extrefs(inum, ipath);
2394         if (ret == -ENOENT && found_refs)
2395                 return 0;
2396
2397         return ret;
2398 }
2399
2400 struct btrfs_data_container *init_data_container(u32 total_bytes)
2401 {
2402         struct btrfs_data_container *data;
2403         size_t alloc_bytes;
2404
2405         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
2406         data = kvmalloc(alloc_bytes, GFP_KERNEL);
2407         if (!data)
2408                 return ERR_PTR(-ENOMEM);
2409
2410         if (total_bytes >= sizeof(*data)) {
2411                 data->bytes_left = total_bytes - sizeof(*data);
2412                 data->bytes_missing = 0;
2413         } else {
2414                 data->bytes_missing = sizeof(*data) - total_bytes;
2415                 data->bytes_left = 0;
2416         }
2417
2418         data->elem_cnt = 0;
2419         data->elem_missed = 0;
2420
2421         return data;
2422 }
2423
2424 /*
2425  * allocates space to return multiple file system paths for an inode.
2426  * total_bytes to allocate are passed, note that space usable for actual path
2427  * information will be total_bytes - sizeof(struct inode_fs_paths).
2428  * the returned pointer must be freed with free_ipath() in the end.
2429  */
2430 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
2431                                         struct btrfs_path *path)
2432 {
2433         struct inode_fs_paths *ifp;
2434         struct btrfs_data_container *fspath;
2435
2436         fspath = init_data_container(total_bytes);
2437         if (IS_ERR(fspath))
2438                 return ERR_CAST(fspath);
2439
2440         ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
2441         if (!ifp) {
2442                 kvfree(fspath);
2443                 return ERR_PTR(-ENOMEM);
2444         }
2445
2446         ifp->btrfs_path = path;
2447         ifp->fspath = fspath;
2448         ifp->fs_root = fs_root;
2449
2450         return ifp;
2451 }
2452
2453 void free_ipath(struct inode_fs_paths *ipath)
2454 {
2455         if (!ipath)
2456                 return;
2457         kvfree(ipath->fspath);
2458         kfree(ipath);
2459 }
2460
2461 struct btrfs_backref_iter *btrfs_backref_iter_alloc(
2462                 struct btrfs_fs_info *fs_info, gfp_t gfp_flag)
2463 {
2464         struct btrfs_backref_iter *ret;
2465
2466         ret = kzalloc(sizeof(*ret), gfp_flag);
2467         if (!ret)
2468                 return NULL;
2469
2470         ret->path = btrfs_alloc_path();
2471         if (!ret->path) {
2472                 kfree(ret);
2473                 return NULL;
2474         }
2475
2476         /* Current backref iterator only supports iteration in commit root */
2477         ret->path->search_commit_root = 1;
2478         ret->path->skip_locking = 1;
2479         ret->fs_info = fs_info;
2480
2481         return ret;
2482 }
2483
2484 int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr)
2485 {
2486         struct btrfs_fs_info *fs_info = iter->fs_info;
2487         struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bytenr);
2488         struct btrfs_path *path = iter->path;
2489         struct btrfs_extent_item *ei;
2490         struct btrfs_key key;
2491         int ret;
2492
2493         key.objectid = bytenr;
2494         key.type = BTRFS_METADATA_ITEM_KEY;
2495         key.offset = (u64)-1;
2496         iter->bytenr = bytenr;
2497
2498         ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
2499         if (ret < 0)
2500                 return ret;
2501         if (ret == 0) {
2502                 ret = -EUCLEAN;
2503                 goto release;
2504         }
2505         if (path->slots[0] == 0) {
2506                 WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
2507                 ret = -EUCLEAN;
2508                 goto release;
2509         }
2510         path->slots[0]--;
2511
2512         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
2513         if ((key.type != BTRFS_EXTENT_ITEM_KEY &&
2514              key.type != BTRFS_METADATA_ITEM_KEY) || key.objectid != bytenr) {
2515                 ret = -ENOENT;
2516                 goto release;
2517         }
2518         memcpy(&iter->cur_key, &key, sizeof(key));
2519         iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2520                                                     path->slots[0]);
2521         iter->end_ptr = (u32)(iter->item_ptr +
2522                         btrfs_item_size(path->nodes[0], path->slots[0]));
2523         ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
2524                             struct btrfs_extent_item);
2525
2526         /*
2527          * Only support iteration on tree backref yet.
2528          *
2529          * This is an extra precaution for non skinny-metadata, where
2530          * EXTENT_ITEM is also used for tree blocks, that we can only use
2531          * extent flags to determine if it's a tree block.
2532          */
2533         if (btrfs_extent_flags(path->nodes[0], ei) & BTRFS_EXTENT_FLAG_DATA) {
2534                 ret = -ENOTSUPP;
2535                 goto release;
2536         }
2537         iter->cur_ptr = (u32)(iter->item_ptr + sizeof(*ei));
2538
2539         /* If there is no inline backref, go search for keyed backref */
2540         if (iter->cur_ptr >= iter->end_ptr) {
2541                 ret = btrfs_next_item(extent_root, path);
2542
2543                 /* No inline nor keyed ref */
2544                 if (ret > 0) {
2545                         ret = -ENOENT;
2546                         goto release;
2547                 }
2548                 if (ret < 0)
2549                         goto release;
2550
2551                 btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key,
2552                                 path->slots[0]);
2553                 if (iter->cur_key.objectid != bytenr ||
2554                     (iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
2555                      iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY)) {
2556                         ret = -ENOENT;
2557                         goto release;
2558                 }
2559                 iter->cur_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2560                                                            path->slots[0]);
2561                 iter->item_ptr = iter->cur_ptr;
2562                 iter->end_ptr = (u32)(iter->item_ptr + btrfs_item_size(
2563                                       path->nodes[0], path->slots[0]));
2564         }
2565
2566         return 0;
2567 release:
2568         btrfs_backref_iter_release(iter);
2569         return ret;
2570 }
2571
2572 /*
2573  * Go to the next backref item of current bytenr, can be either inlined or
2574  * keyed.
2575  *
2576  * Caller needs to check whether it's inline ref or not by iter->cur_key.
2577  *
2578  * Return 0 if we get next backref without problem.
2579  * Return >0 if there is no extra backref for this bytenr.
2580  * Return <0 if there is something wrong happened.
2581  */
2582 int btrfs_backref_iter_next(struct btrfs_backref_iter *iter)
2583 {
2584         struct extent_buffer *eb = btrfs_backref_get_eb(iter);
2585         struct btrfs_root *extent_root;
2586         struct btrfs_path *path = iter->path;
2587         struct btrfs_extent_inline_ref *iref;
2588         int ret;
2589         u32 size;
2590
2591         if (btrfs_backref_iter_is_inline_ref(iter)) {
2592                 /* We're still inside the inline refs */
2593                 ASSERT(iter->cur_ptr < iter->end_ptr);
2594
2595                 if (btrfs_backref_has_tree_block_info(iter)) {
2596                         /* First tree block info */
2597                         size = sizeof(struct btrfs_tree_block_info);
2598                 } else {
2599                         /* Use inline ref type to determine the size */
2600                         int type;
2601
2602                         iref = (struct btrfs_extent_inline_ref *)
2603                                 ((unsigned long)iter->cur_ptr);
2604                         type = btrfs_extent_inline_ref_type(eb, iref);
2605
2606                         size = btrfs_extent_inline_ref_size(type);
2607                 }
2608                 iter->cur_ptr += size;
2609                 if (iter->cur_ptr < iter->end_ptr)
2610                         return 0;
2611
2612                 /* All inline items iterated, fall through */
2613         }
2614
2615         /* We're at keyed items, there is no inline item, go to the next one */
2616         extent_root = btrfs_extent_root(iter->fs_info, iter->bytenr);
2617         ret = btrfs_next_item(extent_root, iter->path);
2618         if (ret)
2619                 return ret;
2620
2621         btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key, path->slots[0]);
2622         if (iter->cur_key.objectid != iter->bytenr ||
2623             (iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
2624              iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY))
2625                 return 1;
2626         iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2627                                         path->slots[0]);
2628         iter->cur_ptr = iter->item_ptr;
2629         iter->end_ptr = iter->item_ptr + (u32)btrfs_item_size(path->nodes[0],
2630                                                 path->slots[0]);
2631         return 0;
2632 }
2633
2634 void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
2635                               struct btrfs_backref_cache *cache, int is_reloc)
2636 {
2637         int i;
2638
2639         cache->rb_root = RB_ROOT;
2640         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
2641                 INIT_LIST_HEAD(&cache->pending[i]);
2642         INIT_LIST_HEAD(&cache->changed);
2643         INIT_LIST_HEAD(&cache->detached);
2644         INIT_LIST_HEAD(&cache->leaves);
2645         INIT_LIST_HEAD(&cache->pending_edge);
2646         INIT_LIST_HEAD(&cache->useless_node);
2647         cache->fs_info = fs_info;
2648         cache->is_reloc = is_reloc;
2649 }
2650
2651 struct btrfs_backref_node *btrfs_backref_alloc_node(
2652                 struct btrfs_backref_cache *cache, u64 bytenr, int level)
2653 {
2654         struct btrfs_backref_node *node;
2655
2656         ASSERT(level >= 0 && level < BTRFS_MAX_LEVEL);
2657         node = kzalloc(sizeof(*node), GFP_NOFS);
2658         if (!node)
2659                 return node;
2660
2661         INIT_LIST_HEAD(&node->list);
2662         INIT_LIST_HEAD(&node->upper);
2663         INIT_LIST_HEAD(&node->lower);
2664         RB_CLEAR_NODE(&node->rb_node);
2665         cache->nr_nodes++;
2666         node->level = level;
2667         node->bytenr = bytenr;
2668
2669         return node;
2670 }
2671
2672 struct btrfs_backref_edge *btrfs_backref_alloc_edge(
2673                 struct btrfs_backref_cache *cache)
2674 {
2675         struct btrfs_backref_edge *edge;
2676
2677         edge = kzalloc(sizeof(*edge), GFP_NOFS);
2678         if (edge)
2679                 cache->nr_edges++;
2680         return edge;
2681 }
2682
2683 /*
2684  * Drop the backref node from cache, also cleaning up all its
2685  * upper edges and any uncached nodes in the path.
2686  *
2687  * This cleanup happens bottom up, thus the node should either
2688  * be the lowest node in the cache or a detached node.
2689  */
2690 void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
2691                                 struct btrfs_backref_node *node)
2692 {
2693         struct btrfs_backref_node *upper;
2694         struct btrfs_backref_edge *edge;
2695
2696         if (!node)
2697                 return;
2698
2699         BUG_ON(!node->lowest && !node->detached);
2700         while (!list_empty(&node->upper)) {
2701                 edge = list_entry(node->upper.next, struct btrfs_backref_edge,
2702                                   list[LOWER]);
2703                 upper = edge->node[UPPER];
2704                 list_del(&edge->list[LOWER]);
2705                 list_del(&edge->list[UPPER]);
2706                 btrfs_backref_free_edge(cache, edge);
2707
2708                 /*
2709                  * Add the node to leaf node list if no other child block
2710                  * cached.
2711                  */
2712                 if (list_empty(&upper->lower)) {
2713                         list_add_tail(&upper->lower, &cache->leaves);
2714                         upper->lowest = 1;
2715                 }
2716         }
2717
2718         btrfs_backref_drop_node(cache, node);
2719 }
2720
2721 /*
2722  * Release all nodes/edges from current cache
2723  */
2724 void btrfs_backref_release_cache(struct btrfs_backref_cache *cache)
2725 {
2726         struct btrfs_backref_node *node;
2727         int i;
2728
2729         while (!list_empty(&cache->detached)) {
2730                 node = list_entry(cache->detached.next,
2731                                   struct btrfs_backref_node, list);
2732                 btrfs_backref_cleanup_node(cache, node);
2733         }
2734
2735         while (!list_empty(&cache->leaves)) {
2736                 node = list_entry(cache->leaves.next,
2737                                   struct btrfs_backref_node, lower);
2738                 btrfs_backref_cleanup_node(cache, node);
2739         }
2740
2741         cache->last_trans = 0;
2742
2743         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
2744                 ASSERT(list_empty(&cache->pending[i]));
2745         ASSERT(list_empty(&cache->pending_edge));
2746         ASSERT(list_empty(&cache->useless_node));
2747         ASSERT(list_empty(&cache->changed));
2748         ASSERT(list_empty(&cache->detached));
2749         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
2750         ASSERT(!cache->nr_nodes);
2751         ASSERT(!cache->nr_edges);
2752 }
2753
2754 /*
2755  * Handle direct tree backref
2756  *
2757  * Direct tree backref means, the backref item shows its parent bytenr
2758  * directly. This is for SHARED_BLOCK_REF backref (keyed or inlined).
2759  *
2760  * @ref_key:    The converted backref key.
2761  *              For keyed backref, it's the item key.
2762  *              For inlined backref, objectid is the bytenr,
2763  *              type is btrfs_inline_ref_type, offset is
2764  *              btrfs_inline_ref_offset.
2765  */
2766 static int handle_direct_tree_backref(struct btrfs_backref_cache *cache,
2767                                       struct btrfs_key *ref_key,
2768                                       struct btrfs_backref_node *cur)
2769 {
2770         struct btrfs_backref_edge *edge;
2771         struct btrfs_backref_node *upper;
2772         struct rb_node *rb_node;
2773
2774         ASSERT(ref_key->type == BTRFS_SHARED_BLOCK_REF_KEY);
2775
2776         /* Only reloc root uses backref pointing to itself */
2777         if (ref_key->objectid == ref_key->offset) {
2778                 struct btrfs_root *root;
2779
2780                 cur->is_reloc_root = 1;
2781                 /* Only reloc backref cache cares about a specific root */
2782                 if (cache->is_reloc) {
2783                         root = find_reloc_root(cache->fs_info, cur->bytenr);
2784                         if (!root)
2785                                 return -ENOENT;
2786                         cur->root = root;
2787                 } else {
2788                         /*
2789                          * For generic purpose backref cache, reloc root node
2790                          * is useless.
2791                          */
2792                         list_add(&cur->list, &cache->useless_node);
2793                 }
2794                 return 0;
2795         }
2796
2797         edge = btrfs_backref_alloc_edge(cache);
2798         if (!edge)
2799                 return -ENOMEM;
2800
2801         rb_node = rb_simple_search(&cache->rb_root, ref_key->offset);
2802         if (!rb_node) {
2803                 /* Parent node not yet cached */
2804                 upper = btrfs_backref_alloc_node(cache, ref_key->offset,
2805                                            cur->level + 1);
2806                 if (!upper) {
2807                         btrfs_backref_free_edge(cache, edge);
2808                         return -ENOMEM;
2809                 }
2810
2811                 /*
2812                  *  Backrefs for the upper level block isn't cached, add the
2813                  *  block to pending list
2814                  */
2815                 list_add_tail(&edge->list[UPPER], &cache->pending_edge);
2816         } else {
2817                 /* Parent node already cached */
2818                 upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
2819                 ASSERT(upper->checked);
2820                 INIT_LIST_HEAD(&edge->list[UPPER]);
2821         }
2822         btrfs_backref_link_edge(edge, cur, upper, LINK_LOWER);
2823         return 0;
2824 }
2825
2826 /*
2827  * Handle indirect tree backref
2828  *
2829  * Indirect tree backref means, we only know which tree the node belongs to.
2830  * We still need to do a tree search to find out the parents. This is for
2831  * TREE_BLOCK_REF backref (keyed or inlined).
2832  *
2833  * @ref_key:    The same as @ref_key in  handle_direct_tree_backref()
2834  * @tree_key:   The first key of this tree block.
2835  * @path:       A clean (released) path, to avoid allocating path every time
2836  *              the function get called.
2837  */
2838 static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache,
2839                                         struct btrfs_path *path,
2840                                         struct btrfs_key *ref_key,
2841                                         struct btrfs_key *tree_key,
2842                                         struct btrfs_backref_node *cur)
2843 {
2844         struct btrfs_fs_info *fs_info = cache->fs_info;
2845         struct btrfs_backref_node *upper;
2846         struct btrfs_backref_node *lower;
2847         struct btrfs_backref_edge *edge;
2848         struct extent_buffer *eb;
2849         struct btrfs_root *root;
2850         struct rb_node *rb_node;
2851         int level;
2852         bool need_check = true;
2853         int ret;
2854
2855         root = btrfs_get_fs_root(fs_info, ref_key->offset, false);
2856         if (IS_ERR(root))
2857                 return PTR_ERR(root);
2858         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
2859                 cur->cowonly = 1;
2860
2861         if (btrfs_root_level(&root->root_item) == cur->level) {
2862                 /* Tree root */
2863                 ASSERT(btrfs_root_bytenr(&root->root_item) == cur->bytenr);
2864                 /*
2865                  * For reloc backref cache, we may ignore reloc root.  But for
2866                  * general purpose backref cache, we can't rely on
2867                  * btrfs_should_ignore_reloc_root() as it may conflict with
2868                  * current running relocation and lead to missing root.
2869                  *
2870                  * For general purpose backref cache, reloc root detection is
2871                  * completely relying on direct backref (key->offset is parent
2872                  * bytenr), thus only do such check for reloc cache.
2873                  */
2874                 if (btrfs_should_ignore_reloc_root(root) && cache->is_reloc) {
2875                         btrfs_put_root(root);
2876                         list_add(&cur->list, &cache->useless_node);
2877                 } else {
2878                         cur->root = root;
2879                 }
2880                 return 0;
2881         }
2882
2883         level = cur->level + 1;
2884
2885         /* Search the tree to find parent blocks referring to the block */
2886         path->search_commit_root = 1;
2887         path->skip_locking = 1;
2888         path->lowest_level = level;
2889         ret = btrfs_search_slot(NULL, root, tree_key, path, 0, 0);
2890         path->lowest_level = 0;
2891         if (ret < 0) {
2892                 btrfs_put_root(root);
2893                 return ret;
2894         }
2895         if (ret > 0 && path->slots[level] > 0)
2896                 path->slots[level]--;
2897
2898         eb = path->nodes[level];
2899         if (btrfs_node_blockptr(eb, path->slots[level]) != cur->bytenr) {
2900                 btrfs_err(fs_info,
2901 "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
2902                           cur->bytenr, level - 1, root->root_key.objectid,
2903                           tree_key->objectid, tree_key->type, tree_key->offset);
2904                 btrfs_put_root(root);
2905                 ret = -ENOENT;
2906                 goto out;
2907         }
2908         lower = cur;
2909
2910         /* Add all nodes and edges in the path */
2911         for (; level < BTRFS_MAX_LEVEL; level++) {
2912                 if (!path->nodes[level]) {
2913                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
2914                                lower->bytenr);
2915                         /* Same as previous should_ignore_reloc_root() call */
2916                         if (btrfs_should_ignore_reloc_root(root) &&
2917                             cache->is_reloc) {
2918                                 btrfs_put_root(root);
2919                                 list_add(&lower->list, &cache->useless_node);
2920                         } else {
2921                                 lower->root = root;
2922                         }
2923                         break;
2924                 }
2925
2926                 edge = btrfs_backref_alloc_edge(cache);
2927                 if (!edge) {
2928                         btrfs_put_root(root);
2929                         ret = -ENOMEM;
2930                         goto out;
2931                 }
2932
2933                 eb = path->nodes[level];
2934                 rb_node = rb_simple_search(&cache->rb_root, eb->start);
2935                 if (!rb_node) {
2936                         upper = btrfs_backref_alloc_node(cache, eb->start,
2937                                                          lower->level + 1);
2938                         if (!upper) {
2939                                 btrfs_put_root(root);
2940                                 btrfs_backref_free_edge(cache, edge);
2941                                 ret = -ENOMEM;
2942                                 goto out;
2943                         }
2944                         upper->owner = btrfs_header_owner(eb);
2945                         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
2946                                 upper->cowonly = 1;
2947
2948                         /*
2949                          * If we know the block isn't shared we can avoid
2950                          * checking its backrefs.
2951                          */
2952                         if (btrfs_block_can_be_shared(root, eb))
2953                                 upper->checked = 0;
2954                         else
2955                                 upper->checked = 1;
2956
2957                         /*
2958                          * Add the block to pending list if we need to check its
2959                          * backrefs, we only do this once while walking up a
2960                          * tree as we will catch anything else later on.
2961                          */
2962                         if (!upper->checked && need_check) {
2963                                 need_check = false;
2964                                 list_add_tail(&edge->list[UPPER],
2965                                               &cache->pending_edge);
2966                         } else {
2967                                 if (upper->checked)
2968                                         need_check = true;
2969                                 INIT_LIST_HEAD(&edge->list[UPPER]);
2970                         }
2971                 } else {
2972                         upper = rb_entry(rb_node, struct btrfs_backref_node,
2973                                          rb_node);
2974                         ASSERT(upper->checked);
2975                         INIT_LIST_HEAD(&edge->list[UPPER]);
2976                         if (!upper->owner)
2977                                 upper->owner = btrfs_header_owner(eb);
2978                 }
2979                 btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
2980
2981                 if (rb_node) {
2982                         btrfs_put_root(root);
2983                         break;
2984                 }
2985                 lower = upper;
2986                 upper = NULL;
2987         }
2988 out:
2989         btrfs_release_path(path);
2990         return ret;
2991 }
2992
2993 /*
2994  * Add backref node @cur into @cache.
2995  *
2996  * NOTE: Even if the function returned 0, @cur is not yet cached as its upper
2997  *       links aren't yet bi-directional. Needs to finish such links.
2998  *       Use btrfs_backref_finish_upper_links() to finish such linkage.
2999  *
3000  * @path:       Released path for indirect tree backref lookup
3001  * @iter:       Released backref iter for extent tree search
3002  * @node_key:   The first key of the tree block
3003  */
3004 int btrfs_backref_add_tree_node(struct btrfs_backref_cache *cache,
3005                                 struct btrfs_path *path,
3006                                 struct btrfs_backref_iter *iter,
3007                                 struct btrfs_key *node_key,
3008                                 struct btrfs_backref_node *cur)
3009 {
3010         struct btrfs_fs_info *fs_info = cache->fs_info;
3011         struct btrfs_backref_edge *edge;
3012         struct btrfs_backref_node *exist;
3013         int ret;
3014
3015         ret = btrfs_backref_iter_start(iter, cur->bytenr);
3016         if (ret < 0)
3017                 return ret;
3018         /*
3019          * We skip the first btrfs_tree_block_info, as we don't use the key
3020          * stored in it, but fetch it from the tree block
3021          */
3022         if (btrfs_backref_has_tree_block_info(iter)) {
3023                 ret = btrfs_backref_iter_next(iter);
3024                 if (ret < 0)
3025                         goto out;
3026                 /* No extra backref? This means the tree block is corrupted */
3027                 if (ret > 0) {
3028                         ret = -EUCLEAN;
3029                         goto out;
3030                 }
3031         }
3032         WARN_ON(cur->checked);
3033         if (!list_empty(&cur->upper)) {
3034                 /*
3035                  * The backref was added previously when processing backref of
3036                  * type BTRFS_TREE_BLOCK_REF_KEY
3037                  */
3038                 ASSERT(list_is_singular(&cur->upper));
3039                 edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
3040                                   list[LOWER]);
3041                 ASSERT(list_empty(&edge->list[UPPER]));
3042                 exist = edge->node[UPPER];
3043                 /*
3044                  * Add the upper level block to pending list if we need check
3045                  * its backrefs
3046                  */
3047                 if (!exist->checked)
3048                         list_add_tail(&edge->list[UPPER], &cache->pending_edge);
3049         } else {
3050                 exist = NULL;
3051         }
3052
3053         for (; ret == 0; ret = btrfs_backref_iter_next(iter)) {
3054                 struct extent_buffer *eb;
3055                 struct btrfs_key key;
3056                 int type;
3057
3058                 cond_resched();
3059                 eb = btrfs_backref_get_eb(iter);
3060
3061                 key.objectid = iter->bytenr;
3062                 if (btrfs_backref_iter_is_inline_ref(iter)) {
3063                         struct btrfs_extent_inline_ref *iref;
3064
3065                         /* Update key for inline backref */
3066                         iref = (struct btrfs_extent_inline_ref *)
3067                                 ((unsigned long)iter->cur_ptr);
3068                         type = btrfs_get_extent_inline_ref_type(eb, iref,
3069                                                         BTRFS_REF_TYPE_BLOCK);
3070                         if (type == BTRFS_REF_TYPE_INVALID) {
3071                                 ret = -EUCLEAN;
3072                                 goto out;
3073                         }
3074                         key.type = type;
3075                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3076                 } else {
3077                         key.type = iter->cur_key.type;
3078                         key.offset = iter->cur_key.offset;
3079                 }
3080
3081                 /*
3082                  * Parent node found and matches current inline ref, no need to
3083                  * rebuild this node for this inline ref
3084                  */
3085                 if (exist &&
3086                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
3087                       exist->owner == key.offset) ||
3088                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
3089                       exist->bytenr == key.offset))) {
3090                         exist = NULL;
3091                         continue;
3092                 }
3093
3094                 /* SHARED_BLOCK_REF means key.offset is the parent bytenr */
3095                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
3096                         ret = handle_direct_tree_backref(cache, &key, cur);
3097                         if (ret < 0)
3098                                 goto out;
3099                         continue;
3100                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
3101                         ret = -EINVAL;
3102                         btrfs_print_v0_err(fs_info);
3103                         btrfs_handle_fs_error(fs_info, ret, NULL);
3104                         goto out;
3105                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
3106                         continue;
3107                 }
3108
3109                 /*
3110                  * key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref offset
3111                  * means the root objectid. We need to search the tree to get
3112                  * its parent bytenr.
3113                  */
3114                 ret = handle_indirect_tree_backref(cache, path, &key, node_key,
3115                                                    cur);
3116                 if (ret < 0)
3117                         goto out;
3118         }
3119         ret = 0;
3120         cur->checked = 1;
3121         WARN_ON(exist);
3122 out:
3123         btrfs_backref_iter_release(iter);
3124         return ret;
3125 }
3126
3127 /*
3128  * Finish the upwards linkage created by btrfs_backref_add_tree_node()
3129  */
3130 int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
3131                                      struct btrfs_backref_node *start)
3132 {
3133         struct list_head *useless_node = &cache->useless_node;
3134         struct btrfs_backref_edge *edge;
3135         struct rb_node *rb_node;
3136         LIST_HEAD(pending_edge);
3137
3138         ASSERT(start->checked);
3139
3140         /* Insert this node to cache if it's not COW-only */
3141         if (!start->cowonly) {
3142                 rb_node = rb_simple_insert(&cache->rb_root, start->bytenr,
3143                                            &start->rb_node);
3144                 if (rb_node)
3145                         btrfs_backref_panic(cache->fs_info, start->bytenr,
3146                                             -EEXIST);
3147                 list_add_tail(&start->lower, &cache->leaves);
3148         }
3149
3150         /*
3151          * Use breadth first search to iterate all related edges.
3152          *
3153          * The starting points are all the edges of this node
3154          */
3155         list_for_each_entry(edge, &start->upper, list[LOWER])
3156                 list_add_tail(&edge->list[UPPER], &pending_edge);
3157
3158         while (!list_empty(&pending_edge)) {
3159                 struct btrfs_backref_node *upper;
3160                 struct btrfs_backref_node *lower;
3161
3162                 edge = list_first_entry(&pending_edge,
3163                                 struct btrfs_backref_edge, list[UPPER]);
3164                 list_del_init(&edge->list[UPPER]);
3165                 upper = edge->node[UPPER];
3166                 lower = edge->node[LOWER];
3167
3168                 /* Parent is detached, no need to keep any edges */
3169                 if (upper->detached) {
3170                         list_del(&edge->list[LOWER]);
3171                         btrfs_backref_free_edge(cache, edge);
3172
3173                         /* Lower node is orphan, queue for cleanup */
3174                         if (list_empty(&lower->upper))
3175                                 list_add(&lower->list, useless_node);
3176                         continue;
3177                 }
3178
3179                 /*
3180                  * All new nodes added in current build_backref_tree() haven't
3181                  * been linked to the cache rb tree.
3182                  * So if we have upper->rb_node populated, this means a cache
3183                  * hit. We only need to link the edge, as @upper and all its
3184                  * parents have already been linked.
3185                  */
3186                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
3187                         if (upper->lowest) {
3188                                 list_del_init(&upper->lower);
3189                                 upper->lowest = 0;
3190                         }
3191
3192                         list_add_tail(&edge->list[UPPER], &upper->lower);
3193                         continue;
3194                 }
3195
3196                 /* Sanity check, we shouldn't have any unchecked nodes */
3197                 if (!upper->checked) {
3198                         ASSERT(0);
3199                         return -EUCLEAN;
3200                 }
3201
3202                 /* Sanity check, COW-only node has non-COW-only parent */
3203                 if (start->cowonly != upper->cowonly) {
3204                         ASSERT(0);
3205                         return -EUCLEAN;
3206                 }
3207
3208                 /* Only cache non-COW-only (subvolume trees) tree blocks */
3209                 if (!upper->cowonly) {
3210                         rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
3211                                                    &upper->rb_node);
3212                         if (rb_node) {
3213                                 btrfs_backref_panic(cache->fs_info,
3214                                                 upper->bytenr, -EEXIST);
3215                                 return -EUCLEAN;
3216                         }
3217                 }
3218
3219                 list_add_tail(&edge->list[UPPER], &upper->lower);
3220
3221                 /*
3222                  * Also queue all the parent edges of this uncached node
3223                  * to finish the upper linkage
3224                  */
3225                 list_for_each_entry(edge, &upper->upper, list[LOWER])
3226                         list_add_tail(&edge->list[UPPER], &pending_edge);
3227         }
3228         return 0;
3229 }
3230
3231 void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
3232                                  struct btrfs_backref_node *node)
3233 {
3234         struct btrfs_backref_node *lower;
3235         struct btrfs_backref_node *upper;
3236         struct btrfs_backref_edge *edge;
3237
3238         while (!list_empty(&cache->useless_node)) {
3239                 lower = list_first_entry(&cache->useless_node,
3240                                    struct btrfs_backref_node, list);
3241                 list_del_init(&lower->list);
3242         }
3243         while (!list_empty(&cache->pending_edge)) {
3244                 edge = list_first_entry(&cache->pending_edge,
3245                                 struct btrfs_backref_edge, list[UPPER]);
3246                 list_del(&edge->list[UPPER]);
3247                 list_del(&edge->list[LOWER]);
3248                 lower = edge->node[LOWER];
3249                 upper = edge->node[UPPER];
3250                 btrfs_backref_free_edge(cache, edge);
3251
3252                 /*
3253                  * Lower is no longer linked to any upper backref nodes and
3254                  * isn't in the cache, we can free it ourselves.
3255                  */
3256                 if (list_empty(&lower->upper) &&
3257                     RB_EMPTY_NODE(&lower->rb_node))
3258                         list_add(&lower->list, &cache->useless_node);
3259
3260                 if (!RB_EMPTY_NODE(&upper->rb_node))
3261                         continue;
3262
3263                 /* Add this guy's upper edges to the list to process */
3264                 list_for_each_entry(edge, &upper->upper, list[LOWER])
3265                         list_add_tail(&edge->list[UPPER],
3266                                       &cache->pending_edge);
3267                 if (list_empty(&upper->upper))
3268                         list_add(&upper->list, &cache->useless_node);
3269         }
3270
3271         while (!list_empty(&cache->useless_node)) {
3272                 lower = list_first_entry(&cache->useless_node,
3273                                    struct btrfs_backref_node, list);
3274                 list_del_init(&lower->list);
3275                 if (lower == node)
3276                         node = NULL;
3277                 btrfs_backref_drop_node(cache, lower);
3278         }
3279
3280         btrfs_backref_cleanup_node(cache, node);
3281         ASSERT(list_empty(&cache->useless_node) &&
3282                list_empty(&cache->pending_edge));
3283 }