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                 } else if (!extent_buffer_uptodate(eb)) {
 793                         free_pref(ref);
 794                         free_extent_buffer(eb);
 795                         return -EIO;
 796                 }
 797                 if (lock)
 798                         btrfs_tree_read_lock(eb);
 799                 if (btrfs_header_level(eb) == 0)
 800                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 801                 else
 802                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 803                 if (lock)
 804                         btrfs_tree_read_unlock(eb);
 805                 free_extent_buffer(eb);
 806                 prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
 807                 cond_resched();
 808         }
 809         return 0;
 810 }
 811
 812 /*
 813  * add all currently queued delayed refs from this head whose seq nr is
 814  * smaller or equal that seq to the list
 815  */
 816 static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
 817                             struct btrfs_delayed_ref_head *head, u64 seq,
 818                             struct preftrees *preftrees, struct share_check *sc)
 819 {
 820         struct btrfs_delayed_ref_node *node;
 821         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 822         struct btrfs_key key;
 823         struct btrfs_key tmp_op_key;
 824         struct rb_node *n;
 825         int count;
 826         int ret = 0;
 827
 828         if (extent_op && extent_op->update_key)
 829                 btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
 830
 831         spin_lock(&head->lock);
 832         for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
 833                 node = rb_entry(n, struct btrfs_delayed_ref_node,
 834                                 ref_node);
 835                 if (node->seq > seq)
 836                         continue;
 837
 838                 switch (node->action) {
 839                 case BTRFS_ADD_DELAYED_EXTENT:
 840                 case BTRFS_UPDATE_DELAYED_HEAD:
 841                         WARN_ON(1);
 842                         continue;
 843                 case BTRFS_ADD_DELAYED_REF:
 844                         count = node->ref_mod;
 845                         break;
 846                 case BTRFS_DROP_DELAYED_REF:
 847                         count = node->ref_mod * -1;
 848                         break;
 849                 default:
 850                         BUG();
 851                 }
 852                 switch (node->type) {
 853                 case BTRFS_TREE_BLOCK_REF_KEY: {
 854                         /* NORMAL INDIRECT METADATA backref */
 855                         struct btrfs_delayed_tree_ref *ref;
 856
 857                         ref = btrfs_delayed_node_to_tree_ref(node);
 858                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
 859                                                &tmp_op_key, ref->level + 1,
 860                                                node->bytenr, count, sc,
 861                                                GFP_ATOMIC);
 862                         break;
 863                 }
 864                 case BTRFS_SHARED_BLOCK_REF_KEY: {
 865                         /* SHARED DIRECT METADATA backref */
 866                         struct btrfs_delayed_tree_ref *ref;
 867
 868                         ref = btrfs_delayed_node_to_tree_ref(node);
 869
 870                         ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
 871                                              ref->parent, node->bytenr, count,
 872                                              sc, GFP_ATOMIC);
 873                         break;
 874                 }
 875                 case BTRFS_EXTENT_DATA_REF_KEY: {
 876                         /* NORMAL INDIRECT DATA backref */
 877                         struct btrfs_delayed_data_ref *ref;
 878                         ref = btrfs_delayed_node_to_data_ref(node);
 879
 880                         key.objectid = ref->objectid;
 881                         key.type = BTRFS_EXTENT_DATA_KEY;
 882                         key.offset = ref->offset;
 883
 884                         /*
 885                          * Found a inum that doesn't match our known inum, we
 886                          * know it's shared.
 887                          */
 888                         if (sc && sc->inum && ref->objectid != sc->inum) {
 889                                 ret = BACKREF_FOUND_SHARED;
 890                                 goto out;
 891                         }
 892
 893                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
 894                                                &key, 0, node->bytenr, count, sc,
 895                                                GFP_ATOMIC);
 896                         break;
 897                 }
 898                 case BTRFS_SHARED_DATA_REF_KEY: {
 899                         /* SHARED DIRECT FULL backref */
 900                         struct btrfs_delayed_data_ref *ref;
 901
 902                         ref = btrfs_delayed_node_to_data_ref(node);
 903
 904                         ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
 905                                              node->bytenr, count, sc,
 906                                              GFP_ATOMIC);
 907                         break;
 908                 }
 909                 default:
 910                         WARN_ON(1);
 911                 }
 912                 /*
 913                  * We must ignore BACKREF_FOUND_SHARED until all delayed
 914                  * refs have been checked.
 915                  */
 916                 if (ret && (ret != BACKREF_FOUND_SHARED))
 917                         break;
 918         }
 919         if (!ret)
 920                 ret = extent_is_shared(sc);
 921 out:
 922         spin_unlock(&head->lock);
 923         return ret;
 924 }
 925
 926 /*
 927  * add all inline backrefs for bytenr to the list
 928  *
 929  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
 930  */
 931 static int add_inline_refs(const struct btrfs_fs_info *fs_info,
 932                            struct btrfs_path *path, u64 bytenr,
 933                            int *info_level, struct preftrees *preftrees,
 934                            struct share_check *sc)
 935 {
 936         int ret = 0;
 937         int slot;
 938         struct extent_buffer *leaf;
 939         struct btrfs_key key;
 940         struct btrfs_key found_key;
 941         unsigned long ptr;
 942         unsigned long end;
 943         struct btrfs_extent_item *ei;
 944         u64 flags;
 945         u64 item_size;
 946
 947         /*
 948          * enumerate all inline refs
 949          */
 950         leaf = path->nodes[0];
 951         slot = path->slots[0];
 952
 953         item_size = btrfs_item_size_nr(leaf, slot);
 954         BUG_ON(item_size < sizeof(*ei));
 955
 956         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 957         flags = btrfs_extent_flags(leaf, ei);
 958         btrfs_item_key_to_cpu(leaf, &found_key, slot);
 959
 960         ptr = (unsigned long)(ei + 1);
 961         end = (unsigned long)ei + item_size;
 962
 963         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
 964             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 965                 struct btrfs_tree_block_info *info;
 966
 967                 info = (struct btrfs_tree_block_info *)ptr;
 968                 *info_level = btrfs_tree_block_level(leaf, info);
 969                 ptr += sizeof(struct btrfs_tree_block_info);
 970                 BUG_ON(ptr > end);
 971         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
 972                 *info_level = found_key.offset;
 973         } else {
 974                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 975         }
 976
 977         while (ptr < end) {
 978                 struct btrfs_extent_inline_ref *iref;
 979                 u64 offset;
 980                 int type;
 981
 982                 iref = (struct btrfs_extent_inline_ref *)ptr;
 983                 type = btrfs_get_extent_inline_ref_type(leaf, iref,
 984                                                         BTRFS_REF_TYPE_ANY);
 985                 if (type == BTRFS_REF_TYPE_INVALID)
 986                         return -EUCLEAN;
 987
 988                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
 989
 990                 switch (type) {
 991                 case BTRFS_SHARED_BLOCK_REF_KEY:
 992                         ret = add_direct_ref(fs_info, preftrees,
 993                                              *info_level + 1, offset,
 994                                              bytenr, 1, NULL, GFP_NOFS);
 995                         break;
 996                 case BTRFS_SHARED_DATA_REF_KEY: {
 997                         struct btrfs_shared_data_ref *sdref;
 998                         int count;
 999
1000                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
1001                         count = btrfs_shared_data_ref_count(leaf, sdref);
1002
1003                         ret = add_direct_ref(fs_info, preftrees, 0, offset,
1004                                              bytenr, count, sc, GFP_NOFS);
1005                         break;
1006                 }
1007                 case BTRFS_TREE_BLOCK_REF_KEY:
1008                         ret = add_indirect_ref(fs_info, preftrees, offset,
1009                                                NULL, *info_level + 1,
1010                                                bytenr, 1, NULL, GFP_NOFS);
1011                         break;
1012                 case BTRFS_EXTENT_DATA_REF_KEY: {
1013                         struct btrfs_extent_data_ref *dref;
1014                         int count;
1015                         u64 root;
1016
1017                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
1018                         count = btrfs_extent_data_ref_count(leaf, dref);
1019                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1020                                                                       dref);
1021                         key.type = BTRFS_EXTENT_DATA_KEY;
1022                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1023
1024                         if (sc && sc->inum && key.objectid != sc->inum) {
1025                                 ret = BACKREF_FOUND_SHARED;
1026                                 break;
1027                         }
1028
1029                         root = btrfs_extent_data_ref_root(leaf, dref);
1030
1031                         ret = add_indirect_ref(fs_info, preftrees, root,
1032                                                &key, 0, bytenr, count,
1033                                                sc, GFP_NOFS);
1034                         break;
1035                 }
1036                 default:
1037                         WARN_ON(1);
1038                 }
1039                 if (ret)
1040                         return ret;
1041                 ptr += btrfs_extent_inline_ref_size(type);
1042         }
1043
1044         return 0;
1045 }
1046
1047 /*
1048  * add all non-inline backrefs for bytenr to the list
1049  *
1050  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
1051  */
1052 static int add_keyed_refs(struct btrfs_fs_info *fs_info,
1053                           struct btrfs_path *path, u64 bytenr,
1054                           int info_level, struct preftrees *preftrees,
1055                           struct share_check *sc)
1056 {
1057         struct btrfs_root *extent_root = fs_info->extent_root;
1058         int ret;
1059         int slot;
1060         struct extent_buffer *leaf;
1061         struct btrfs_key key;
1062
1063         while (1) {
1064                 ret = btrfs_next_item(extent_root, path);
1065                 if (ret < 0)
1066                         break;
1067                 if (ret) {
1068                         ret = 0;
1069                         break;
1070                 }
1071
1072                 slot = path->slots[0];
1073                 leaf = path->nodes[0];
1074                 btrfs_item_key_to_cpu(leaf, &key, slot);
1075
1076                 if (key.objectid != bytenr)
1077                         break;
1078                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
1079                         continue;
1080                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
1081                         break;
1082
1083                 switch (key.type) {
1084                 case BTRFS_SHARED_BLOCK_REF_KEY:
1085                         /* SHARED DIRECT METADATA backref */
1086                         ret = add_direct_ref(fs_info, preftrees,
1087                                              info_level + 1, key.offset,
1088                                              bytenr, 1, NULL, GFP_NOFS);
1089                         break;
1090                 case BTRFS_SHARED_DATA_REF_KEY: {
1091                         /* SHARED DIRECT FULL backref */
1092                         struct btrfs_shared_data_ref *sdref;
1093                         int count;
1094
1095                         sdref = btrfs_item_ptr(leaf, slot,
1096                                               struct btrfs_shared_data_ref);
1097                         count = btrfs_shared_data_ref_count(leaf, sdref);
1098                         ret = add_direct_ref(fs_info, preftrees, 0,
1099                                              key.offset, bytenr, count,
1100                                              sc, GFP_NOFS);
1101                         break;
1102                 }
1103                 case BTRFS_TREE_BLOCK_REF_KEY:
1104                         /* NORMAL INDIRECT METADATA backref */
1105                         ret = add_indirect_ref(fs_info, preftrees, key.offset,
1106                                                NULL, info_level + 1, bytenr,
1107                                                1, NULL, GFP_NOFS);
1108                         break;
1109                 case BTRFS_EXTENT_DATA_REF_KEY: {
1110                         /* NORMAL INDIRECT DATA backref */
1111                         struct btrfs_extent_data_ref *dref;
1112                         int count;
1113                         u64 root;
1114
1115                         dref = btrfs_item_ptr(leaf, slot,
1116                                               struct btrfs_extent_data_ref);
1117                         count = btrfs_extent_data_ref_count(leaf, dref);
1118                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1119                                                                       dref);
1120                         key.type = BTRFS_EXTENT_DATA_KEY;
1121                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1122
1123                         if (sc && sc->inum && key.objectid != sc->inum) {
1124                                 ret = BACKREF_FOUND_SHARED;
1125                                 break;
1126                         }
1127
1128                         root = btrfs_extent_data_ref_root(leaf, dref);
1129                         ret = add_indirect_ref(fs_info, preftrees, root,
1130                                                &key, 0, bytenr, count,
1131                                                sc, GFP_NOFS);
1132                         break;
1133                 }
1134                 default:
1135                         WARN_ON(1);
1136                 }
1137                 if (ret)
1138                         return ret;
1139
1140         }
1141
1142         return ret;
1143 }
1144
1145 /*
1146  * this adds all existing backrefs (inline backrefs, backrefs and delayed
1147  * refs) for the given bytenr to the refs list, merges duplicates and resolves
1148  * indirect refs to their parent bytenr.
1149  * When roots are found, they're added to the roots list
1150  *
1151  * If time_seq is set to BTRFS_SEQ_LAST, it will not search delayed_refs, and
1152  * behave much like trans == NULL case, the difference only lies in it will not
1153  * commit root.
1154  * The special case is for qgroup to search roots in commit_transaction().
1155  *
1156  * @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a
1157  * shared extent is detected.
1158  *
1159  * Otherwise this returns 0 for success and <0 for an error.
1160  *
1161  * If ignore_offset is set to false, only extent refs whose offsets match
1162  * extent_item_pos are returned.  If true, every extent ref is returned
1163  * and extent_item_pos is ignored.
1164  *
1165  * FIXME some caching might speed things up
1166  */
1167 static int find_parent_nodes(struct btrfs_trans_handle *trans,
1168                              struct btrfs_fs_info *fs_info, u64 bytenr,
1169                              u64 time_seq, struct ulist *refs,
1170                              struct ulist *roots, const u64 *extent_item_pos,
1171                              struct share_check *sc, bool ignore_offset)
1172 {
1173         struct btrfs_key key;
1174         struct btrfs_path *path;
1175         struct btrfs_delayed_ref_root *delayed_refs = NULL;
1176         struct btrfs_delayed_ref_head *head;
1177         int info_level = 0;
1178         int ret;
1179         struct prelim_ref *ref;
1180         struct rb_node *node;
1181         struct extent_inode_elem *eie = NULL;
1182         struct preftrees preftrees = {
1183                 .direct = PREFTREE_INIT,
1184                 .indirect = PREFTREE_INIT,
1185                 .indirect_missing_keys = PREFTREE_INIT
1186         };
1187
1188         key.objectid = bytenr;
1189         key.offset = (u64)-1;
1190         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1191                 key.type = BTRFS_METADATA_ITEM_KEY;
1192         else
1193                 key.type = BTRFS_EXTENT_ITEM_KEY;
1194
1195         path = btrfs_alloc_path();
1196         if (!path)
1197                 return -ENOMEM;
1198         if (!trans) {
1199                 path->search_commit_root = 1;
1200                 path->skip_locking = 1;
1201         }
1202
1203         if (time_seq == BTRFS_SEQ_LAST)
1204                 path->skip_locking = 1;
1205
1206         /*
1207          * grab both a lock on the path and a lock on the delayed ref head.
1208          * We need both to get a consistent picture of how the refs look
1209          * at a specified point in time
1210          */
1211 again:
1212         head = NULL;
1213
1214         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
1215         if (ret < 0)
1216                 goto out;
1217         BUG_ON(ret == 0);
1218
1219 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
1220         if (trans && likely(trans->type != __TRANS_DUMMY) &&
1221             time_seq != BTRFS_SEQ_LAST) {
1222 #else
1223         if (trans && time_seq != BTRFS_SEQ_LAST) {
1224 #endif
1225                 /*
1226                  * look if there are updates for this ref queued and lock the
1227                  * head
1228                  */
1229                 delayed_refs = &trans->transaction->delayed_refs;
1230                 spin_lock(&delayed_refs->lock);
1231                 head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
1232                 if (head) {
1233                         if (!mutex_trylock(&head->mutex)) {
1234                                 refcount_inc(&head->refs);
1235                                 spin_unlock(&delayed_refs->lock);
1236
1237                                 btrfs_release_path(path);
1238
1239                                 /*
1240                                  * Mutex was contended, block until it's
1241                                  * released and try again
1242                                  */
1243                                 mutex_lock(&head->mutex);
1244                                 mutex_unlock(&head->mutex);
1245                                 btrfs_put_delayed_ref_head(head);
1246                                 goto again;
1247                         }
1248                         spin_unlock(&delayed_refs->lock);
1249                         ret = add_delayed_refs(fs_info, head, time_seq,
1250                                                &preftrees, sc);
1251                         mutex_unlock(&head->mutex);
1252                         if (ret)
1253                                 goto out;
1254                 } else {
1255                         spin_unlock(&delayed_refs->lock);
1256                 }
1257         }
1258
1259         if (path->slots[0]) {
1260                 struct extent_buffer *leaf;
1261                 int slot;
1262
1263                 path->slots[0]--;
1264                 leaf = path->nodes[0];
1265                 slot = path->slots[0];
1266                 btrfs_item_key_to_cpu(leaf, &key, slot);
1267                 if (key.objectid == bytenr &&
1268                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
1269                      key.type == BTRFS_METADATA_ITEM_KEY)) {
1270                         ret = add_inline_refs(fs_info, path, bytenr,
1271                                               &info_level, &preftrees, sc);
1272                         if (ret)
1273                                 goto out;
1274                         ret = add_keyed_refs(fs_info, path, bytenr, info_level,
1275                                              &preftrees, sc);
1276                         if (ret)
1277                                 goto out;
1278                 }
1279         }
1280
1281         btrfs_release_path(path);
1282
1283         ret = add_missing_keys(fs_info, &preftrees, path->skip_locking == 0);
1284         if (ret)
1285                 goto out;
1286
1287         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
1288
1289         ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
1290                                     extent_item_pos, sc, ignore_offset);
1291         if (ret)
1292                 goto out;
1293
1294         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
1295
1296         /*
1297          * This walks the tree of merged and resolved refs. Tree blocks are
1298          * read in as needed. Unique entries are added to the ulist, and
1299          * the list of found roots is updated.
1300          *
1301          * We release the entire tree in one go before returning.
1302          */
1303         node = rb_first_cached(&preftrees.direct.root);
1304         while (node) {
1305                 ref = rb_entry(node, struct prelim_ref, rbnode);
1306                 node = rb_next(&ref->rbnode);
1307                 /*
1308                  * ref->count < 0 can happen here if there are delayed
1309                  * refs with a node->action of BTRFS_DROP_DELAYED_REF.
1310                  * prelim_ref_insert() relies on this when merging
1311                  * identical refs to keep the overall count correct.
1312                  * prelim_ref_insert() will merge only those refs
1313                  * which compare identically.  Any refs having
1314                  * e.g. different offsets would not be merged,
1315                  * and would retain their original ref->count < 0.
1316                  */
1317                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1318                         if (sc && sc->root_objectid &&
1319                             ref->root_id != sc->root_objectid) {
1320                                 ret = BACKREF_FOUND_SHARED;
1321                                 goto out;
1322                         }
1323
1324                         /* no parent == root of tree */
1325                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1326                         if (ret < 0)
1327                                 goto out;
1328                 }
1329                 if (ref->count && ref->parent) {
1330                         if (extent_item_pos && !ref->inode_list &&
1331                             ref->level == 0) {
1332                                 struct extent_buffer *eb;
1333
1334                                 eb = read_tree_block(fs_info, ref->parent, 0,
1335                                                      0, ref->level, NULL);
1336                                 if (IS_ERR(eb)) {
1337                                         ret = PTR_ERR(eb);
1338                                         goto out;
1339                                 } else if (!extent_buffer_uptodate(eb)) {
1340                                         free_extent_buffer(eb);
1341                                         ret = -EIO;
1342                                         goto out;
1343                                 }
1344
1345                                 if (!path->skip_locking)
1346                                         btrfs_tree_read_lock(eb);
1347                                 ret = find_extent_in_eb(eb, bytenr,
1348                                                         *extent_item_pos, &eie, ignore_offset);
1349                                 if (!path->skip_locking)
1350                                         btrfs_tree_read_unlock(eb);
1351                                 free_extent_buffer(eb);
1352                                 if (ret < 0)
1353                                         goto out;
1354                                 ref->inode_list = eie;
1355                         }
1356                         ret = ulist_add_merge_ptr(refs, ref->parent,
1357                                                   ref->inode_list,
1358                                                   (void **)&eie, GFP_NOFS);
1359                         if (ret < 0)
1360                                 goto out;
1361                         if (!ret && extent_item_pos) {
1362                                 /*
1363                                  * we've recorded that parent, so we must extend
1364                                  * its inode list here
1365                                  */
1366                                 BUG_ON(!eie);
1367                                 while (eie->next)
1368                                         eie = eie->next;
1369                                 eie->next = ref->inode_list;
1370                         }
1371                         eie = NULL;
1372                 }
1373                 cond_resched();
1374         }
1375
1376 out:
1377         btrfs_free_path(path);
1378
1379         prelim_release(&preftrees.direct);
1380         prelim_release(&preftrees.indirect);
1381         prelim_release(&preftrees.indirect_missing_keys);
1382
1383         if (ret < 0)
1384                 free_inode_elem_list(eie);
1385         return ret;
1386 }
1387
1388 static void free_leaf_list(struct ulist *blocks)
1389 {
1390         struct ulist_node *node = NULL;
1391         struct extent_inode_elem *eie;
1392         struct ulist_iterator uiter;
1393
1394         ULIST_ITER_INIT(&uiter);
1395         while ((node = ulist_next(blocks, &uiter))) {
1396                 if (!node->aux)
1397                         continue;
1398                 eie = unode_aux_to_inode_list(node);
1399                 free_inode_elem_list(eie);
1400                 node->aux = 0;
1401         }
1402
1403         ulist_free(blocks);
1404 }
1405
1406 /*
1407  * Finds all leafs with a reference to the specified combination of bytenr and
1408  * offset. key_list_head will point to a list of corresponding keys (caller must
1409  * free each list element). The leafs will be stored in the leafs ulist, which
1410  * must be freed with ulist_free.
1411  *
1412  * returns 0 on success, <0 on error
1413  */
1414 int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1415                          struct btrfs_fs_info *fs_info, u64 bytenr,
1416                          u64 time_seq, struct ulist **leafs,
1417                          const u64 *extent_item_pos, bool ignore_offset)
1418 {
1419         int ret;
1420
1421         *leafs = ulist_alloc(GFP_NOFS);
1422         if (!*leafs)
1423                 return -ENOMEM;
1424
1425         ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1426                                 *leafs, NULL, extent_item_pos, NULL, ignore_offset);
1427         if (ret < 0 && ret != -ENOENT) {
1428                 free_leaf_list(*leafs);
1429                 return ret;
1430         }
1431
1432         return 0;
1433 }
1434
1435 /*
1436  * walk all backrefs for a given extent to find all roots that reference this
1437  * extent. Walking a backref means finding all extents that reference this
1438  * extent and in turn walk the backrefs of those, too. Naturally this is a
1439  * recursive process, but here it is implemented in an iterative fashion: We
1440  * find all referencing extents for the extent in question and put them on a
1441  * list. In turn, we find all referencing extents for those, further appending
1442  * to the list. The way we iterate the list allows adding more elements after
1443  * the current while iterating. The process stops when we reach the end of the
1444  * list. Found roots are added to the roots list.
1445  *
1446  * returns 0 on success, < 0 on error.
1447  */
1448 static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
1449                                      struct btrfs_fs_info *fs_info, u64 bytenr,
1450                                      u64 time_seq, struct ulist **roots,
1451                                      bool ignore_offset)
1452 {
1453         struct ulist *tmp;
1454         struct ulist_node *node = NULL;
1455         struct ulist_iterator uiter;
1456         int ret;
1457
1458         tmp = ulist_alloc(GFP_NOFS);
1459         if (!tmp)
1460                 return -ENOMEM;
1461         *roots = ulist_alloc(GFP_NOFS);
1462         if (!*roots) {
1463                 ulist_free(tmp);
1464                 return -ENOMEM;
1465         }
1466
1467         ULIST_ITER_INIT(&uiter);
1468         while (1) {
1469                 ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1470                                         tmp, *roots, NULL, NULL, ignore_offset);
1471                 if (ret < 0 && ret != -ENOENT) {
1472                         ulist_free(tmp);
1473                         ulist_free(*roots);
1474                         *roots = NULL;
1475                         return ret;
1476                 }
1477                 node = ulist_next(tmp, &uiter);
1478                 if (!node)
1479                         break;
1480                 bytenr = node->val;
1481                 cond_resched();
1482         }
1483
1484         ulist_free(tmp);
1485         return 0;
1486 }
1487
1488 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1489                          struct btrfs_fs_info *fs_info, u64 bytenr,
1490                          u64 time_seq, struct ulist **roots,
1491                          bool ignore_offset, bool skip_commit_root_sem)
1492 {
1493         int ret;
1494
1495         if (!trans && !skip_commit_root_sem)
1496                 down_read(&fs_info->commit_root_sem);
1497         ret = btrfs_find_all_roots_safe(trans, fs_info, bytenr,
1498                                         time_seq, roots, ignore_offset);
1499         if (!trans && !skip_commit_root_sem)
1500                 up_read(&fs_info->commit_root_sem);
1501         return ret;
1502 }
1503
1504 /**
1505  * Check if an extent is shared or not
1506  *
1507  * @root:   root inode belongs to
1508  * @inum:   inode number of the inode whose extent we are checking
1509  * @bytenr: logical bytenr of the extent we are checking
1510  * @roots:  list of roots this extent is shared among
1511  * @tmp:    temporary list used for iteration
1512  *
1513  * btrfs_check_shared uses the backref walking code but will short
1514  * circuit as soon as it finds a root or inode that doesn't match the
1515  * one passed in. This provides a significant performance benefit for
1516  * callers (such as fiemap) which want to know whether the extent is
1517  * shared but do not need a ref count.
1518  *
1519  * This attempts to attach to the running transaction in order to account for
1520  * delayed refs, but continues on even when no running transaction exists.
1521  *
1522  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1523  */
1524 int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr,
1525                 struct ulist *roots, struct ulist *tmp)
1526 {
1527         struct btrfs_fs_info *fs_info = root->fs_info;
1528         struct btrfs_trans_handle *trans;
1529         struct ulist_iterator uiter;
1530         struct ulist_node *node;
1531         struct btrfs_seq_list elem = BTRFS_SEQ_LIST_INIT(elem);
1532         int ret = 0;
1533         struct share_check shared = {
1534                 .root_objectid = root->root_key.objectid,
1535                 .inum = inum,
1536                 .share_count = 0,
1537         };
1538
1539         ulist_init(roots);
1540         ulist_init(tmp);
1541
1542         trans = btrfs_join_transaction_nostart(root);
1543         if (IS_ERR(trans)) {
1544                 if (PTR_ERR(trans) != -ENOENT && PTR_ERR(trans) != -EROFS) {
1545                         ret = PTR_ERR(trans);
1546                         goto out;
1547                 }
1548                 trans = NULL;
1549                 down_read(&fs_info->commit_root_sem);
1550         } else {
1551                 btrfs_get_tree_mod_seq(fs_info, &elem);
1552         }
1553
1554         ULIST_ITER_INIT(&uiter);
1555         while (1) {
1556                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1557                                         roots, NULL, &shared, false);
1558                 if (ret == BACKREF_FOUND_SHARED) {
1559                         /* this is the only condition under which we return 1 */
1560                         ret = 1;
1561                         break;
1562                 }
1563                 if (ret < 0 && ret != -ENOENT)
1564                         break;
1565                 ret = 0;
1566                 node = ulist_next(tmp, &uiter);
1567                 if (!node)
1568                         break;
1569                 bytenr = node->val;
1570                 shared.share_count = 0;
1571                 cond_resched();
1572         }
1573
1574         if (trans) {
1575                 btrfs_put_tree_mod_seq(fs_info, &elem);
1576                 btrfs_end_transaction(trans);
1577         } else {
1578                 up_read(&fs_info->commit_root_sem);
1579         }
1580 out:
1581         ulist_release(roots);
1582         ulist_release(tmp);
1583         return ret;
1584 }
1585
1586 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1587                           u64 start_off, struct btrfs_path *path,
1588                           struct btrfs_inode_extref **ret_extref,
1589                           u64 *found_off)
1590 {
1591         int ret, slot;
1592         struct btrfs_key key;
1593         struct btrfs_key found_key;
1594         struct btrfs_inode_extref *extref;
1595         const struct extent_buffer *leaf;
1596         unsigned long ptr;
1597
1598         key.objectid = inode_objectid;
1599         key.type = BTRFS_INODE_EXTREF_KEY;
1600         key.offset = start_off;
1601
1602         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1603         if (ret < 0)
1604                 return ret;
1605
1606         while (1) {
1607                 leaf = path->nodes[0];
1608                 slot = path->slots[0];
1609                 if (slot >= btrfs_header_nritems(leaf)) {
1610                         /*
1611                          * If the item at offset is not found,
1612                          * btrfs_search_slot will point us to the slot
1613                          * where it should be inserted. In our case
1614                          * that will be the slot directly before the
1615                          * next INODE_REF_KEY_V2 item. In the case
1616                          * that we're pointing to the last slot in a
1617                          * leaf, we must move one leaf over.
1618                          */
1619                         ret = btrfs_next_leaf(root, path);
1620                         if (ret) {
1621                                 if (ret >= 1)
1622                                         ret = -ENOENT;
1623                                 break;
1624                         }
1625                         continue;
1626                 }
1627
1628                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1629
1630                 /*
1631                  * Check that we're still looking at an extended ref key for
1632                  * this particular objectid. If we have different
1633                  * objectid or type then there are no more to be found
1634                  * in the tree and we can exit.
1635                  */
1636                 ret = -ENOENT;
1637                 if (found_key.objectid != inode_objectid)
1638                         break;
1639                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1640                         break;
1641
1642                 ret = 0;
1643                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1644                 extref = (struct btrfs_inode_extref *)ptr;
1645                 *ret_extref = extref;
1646                 if (found_off)
1647                         *found_off = found_key.offset;
1648                 break;
1649         }
1650
1651         return ret;
1652 }
1653
1654 /*
1655  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1656  * Elements of the path are separated by '/' and the path is guaranteed to be
1657  * 0-terminated. the path is only given within the current file system.
1658  * Therefore, it never starts with a '/'. the caller is responsible to provide
1659  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1660  * the start point of the resulting string is returned. this pointer is within
1661  * dest, normally.
1662  * in case the path buffer would overflow, the pointer is decremented further
1663  * as if output was written to the buffer, though no more output is actually
1664  * generated. that way, the caller can determine how much space would be
1665  * required for the path to fit into the buffer. in that case, the returned
1666  * value will be smaller than dest. callers must check this!
1667  */
1668 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1669                         u32 name_len, unsigned long name_off,
1670                         struct extent_buffer *eb_in, u64 parent,
1671                         char *dest, u32 size)
1672 {
1673         int slot;
1674         u64 next_inum;
1675         int ret;
1676         s64 bytes_left = ((s64)size) - 1;
1677         struct extent_buffer *eb = eb_in;
1678         struct btrfs_key found_key;
1679         struct btrfs_inode_ref *iref;
1680
1681         if (bytes_left >= 0)
1682                 dest[bytes_left] = '\0';
1683
1684         while (1) {
1685                 bytes_left -= name_len;
1686                 if (bytes_left >= 0)
1687                         read_extent_buffer(eb, dest + bytes_left,
1688                                            name_off, name_len);
1689                 if (eb != eb_in) {
1690                         if (!path->skip_locking)
1691                                 btrfs_tree_read_unlock(eb);
1692                         free_extent_buffer(eb);
1693                 }
1694                 ret = btrfs_find_item(fs_root, path, parent, 0,
1695                                 BTRFS_INODE_REF_KEY, &found_key);
1696                 if (ret > 0)
1697                         ret = -ENOENT;
1698                 if (ret)
1699                         break;
1700
1701                 next_inum = found_key.offset;
1702
1703                 /* regular exit ahead */
1704                 if (parent == next_inum)
1705                         break;
1706
1707                 slot = path->slots[0];
1708                 eb = path->nodes[0];
1709                 /* make sure we can use eb after releasing the path */
1710                 if (eb != eb_in) {
1711                         path->nodes[0] = NULL;
1712                         path->locks[0] = 0;
1713                 }
1714                 btrfs_release_path(path);
1715                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1716
1717                 name_len = btrfs_inode_ref_name_len(eb, iref);
1718                 name_off = (unsigned long)(iref + 1);
1719
1720                 parent = next_inum;
1721                 --bytes_left;
1722                 if (bytes_left >= 0)
1723                         dest[bytes_left] = '/';
1724         }
1725
1726         btrfs_release_path(path);
1727
1728         if (ret)
1729                 return ERR_PTR(ret);
1730
1731         return dest + bytes_left;
1732 }
1733
1734 /*
1735  * this makes the path point to (logical EXTENT_ITEM *)
1736  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1737  * tree blocks and <0 on error.
1738  */
1739 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1740                         struct btrfs_path *path, struct btrfs_key *found_key,
1741                         u64 *flags_ret)
1742 {
1743         int ret;
1744         u64 flags;
1745         u64 size = 0;
1746         u32 item_size;
1747         const struct extent_buffer *eb;
1748         struct btrfs_extent_item *ei;
1749         struct btrfs_key key;
1750
1751         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1752                 key.type = BTRFS_METADATA_ITEM_KEY;
1753         else
1754                 key.type = BTRFS_EXTENT_ITEM_KEY;
1755         key.objectid = logical;
1756         key.offset = (u64)-1;
1757
1758         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1759         if (ret < 0)
1760                 return ret;
1761
1762         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1763         if (ret) {
1764                 if (ret > 0)
1765                         ret = -ENOENT;
1766                 return ret;
1767         }
1768         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1769         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1770                 size = fs_info->nodesize;
1771         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1772                 size = found_key->offset;
1773
1774         if (found_key->objectid > logical ||
1775             found_key->objectid + size <= logical) {
1776                 btrfs_debug(fs_info,
1777                         "logical %llu is not within any extent", logical);
1778                 return -ENOENT;
1779         }
1780
1781         eb = path->nodes[0];
1782         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1783         BUG_ON(item_size < sizeof(*ei));
1784
1785         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1786         flags = btrfs_extent_flags(eb, ei);
1787
1788         btrfs_debug(fs_info,
1789                 "logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
1790                  logical, logical - found_key->objectid, found_key->objectid,
1791                  found_key->offset, flags, item_size);
1792
1793         WARN_ON(!flags_ret);
1794         if (flags_ret) {
1795                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1796                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1797                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1798                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1799                 else
1800                         BUG();
1801                 return 0;
1802         }
1803
1804         return -EIO;
1805 }
1806
1807 /*
1808  * helper function to iterate extent inline refs. ptr must point to a 0 value
1809  * for the first call and may be modified. it is used to track state.
1810  * if more refs exist, 0 is returned and the next call to
1811  * get_extent_inline_ref must pass the modified ptr parameter to get the
1812  * next ref. after the last ref was processed, 1 is returned.
1813  * returns <0 on error
1814  */
1815 static int get_extent_inline_ref(unsigned long *ptr,
1816                                  const struct extent_buffer *eb,
1817                                  const struct btrfs_key *key,
1818                                  const struct btrfs_extent_item *ei,
1819                                  u32 item_size,
1820                                  struct btrfs_extent_inline_ref **out_eiref,
1821                                  int *out_type)
1822 {
1823         unsigned long end;
1824         u64 flags;
1825         struct btrfs_tree_block_info *info;
1826
1827         if (!*ptr) {
1828                 /* first call */
1829                 flags = btrfs_extent_flags(eb, ei);
1830                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1831                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1832                                 /* a skinny metadata extent */
1833                                 *out_eiref =
1834                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1835                         } else {
1836                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1837                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1838                                 *out_eiref =
1839                                    (struct btrfs_extent_inline_ref *)(info + 1);
1840                         }
1841                 } else {
1842                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1843                 }
1844                 *ptr = (unsigned long)*out_eiref;
1845                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1846                         return -ENOENT;
1847         }
1848
1849         end = (unsigned long)ei + item_size;
1850         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1851         *out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
1852                                                      BTRFS_REF_TYPE_ANY);
1853         if (*out_type == BTRFS_REF_TYPE_INVALID)
1854                 return -EUCLEAN;
1855
1856         *ptr += btrfs_extent_inline_ref_size(*out_type);
1857         WARN_ON(*ptr > end);
1858         if (*ptr == end)
1859                 return 1; /* last */
1860
1861         return 0;
1862 }
1863
1864 /*
1865  * reads the tree block backref for an extent. tree level and root are returned
1866  * through out_level and out_root. ptr must point to a 0 value for the first
1867  * call and may be modified (see get_extent_inline_ref comment).
1868  * returns 0 if data was provided, 1 if there was no more data to provide or
1869  * <0 on error.
1870  */
1871 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1872                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1873                             u32 item_size, u64 *out_root, u8 *out_level)
1874 {
1875         int ret;
1876         int type;
1877         struct btrfs_extent_inline_ref *eiref;
1878
1879         if (*ptr == (unsigned long)-1)
1880                 return 1;
1881
1882         while (1) {
1883                 ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
1884                                               &eiref, &type);
1885                 if (ret < 0)
1886                         return ret;
1887
1888                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1889                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1890                         break;
1891
1892                 if (ret == 1)
1893                         return 1;
1894         }
1895
1896         /* we can treat both ref types equally here */
1897         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1898
1899         if (key->type == BTRFS_EXTENT_ITEM_KEY) {
1900                 struct btrfs_tree_block_info *info;
1901
1902                 info = (struct btrfs_tree_block_info *)(ei + 1);
1903                 *out_level = btrfs_tree_block_level(eb, info);
1904         } else {
1905                 ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
1906                 *out_level = (u8)key->offset;
1907         }
1908
1909         if (ret == 1)
1910                 *ptr = (unsigned long)-1;
1911
1912         return 0;
1913 }
1914
1915 static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
1916                              struct extent_inode_elem *inode_list,
1917                              u64 root, u64 extent_item_objectid,
1918                              iterate_extent_inodes_t *iterate, void *ctx)
1919 {
1920         struct extent_inode_elem *eie;
1921         int ret = 0;
1922
1923         for (eie = inode_list; eie; eie = eie->next) {
1924                 btrfs_debug(fs_info,
1925                             "ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
1926                             extent_item_objectid, eie->inum,
1927                             eie->offset, root);
1928                 ret = iterate(eie->inum, eie->offset, root, ctx);
1929                 if (ret) {
1930                         btrfs_debug(fs_info,
1931                                     "stopping iteration for %llu due to ret=%d",
1932                                     extent_item_objectid, ret);
1933                         break;
1934                 }
1935         }
1936
1937         return ret;
1938 }
1939
1940 /*
1941  * calls iterate() for every inode that references the extent identified by
1942  * the given parameters.
1943  * when the iterator function returns a non-zero value, iteration stops.
1944  */
1945 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1946                                 u64 extent_item_objectid, u64 extent_item_pos,
1947                                 int search_commit_root,
1948                                 iterate_extent_inodes_t *iterate, void *ctx,
1949                                 bool ignore_offset)
1950 {
1951         int ret;
1952         struct btrfs_trans_handle *trans = NULL;
1953         struct ulist *refs = NULL;
1954         struct ulist *roots = NULL;
1955         struct ulist_node *ref_node = NULL;
1956         struct ulist_node *root_node = NULL;
1957         struct btrfs_seq_list seq_elem = BTRFS_SEQ_LIST_INIT(seq_elem);
1958         struct ulist_iterator ref_uiter;
1959         struct ulist_iterator root_uiter;
1960
1961         btrfs_debug(fs_info, "resolving all inodes for extent %llu",
1962                         extent_item_objectid);
1963
1964         if (!search_commit_root) {
1965                 trans = btrfs_attach_transaction(fs_info->extent_root);
1966                 if (IS_ERR(trans)) {
1967                         if (PTR_ERR(trans) != -ENOENT &&
1968                             PTR_ERR(trans) != -EROFS)
1969                                 return PTR_ERR(trans);
1970                         trans = NULL;
1971                 }
1972         }
1973
1974         if (trans)
1975                 btrfs_get_tree_mod_seq(fs_info, &seq_elem);
1976         else
1977                 down_read(&fs_info->commit_root_sem);
1978
1979         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1980                                    seq_elem.seq, &refs,
1981                                    &extent_item_pos, ignore_offset);
1982         if (ret)
1983                 goto out;
1984
1985         ULIST_ITER_INIT(&ref_uiter);
1986         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1987                 ret = btrfs_find_all_roots_safe(trans, fs_info, ref_node->val,
1988                                                 seq_elem.seq, &roots,
1989                                                 ignore_offset);
1990                 if (ret)
1991                         break;
1992                 ULIST_ITER_INIT(&root_uiter);
1993                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1994                         btrfs_debug(fs_info,
1995                                     "root %llu references leaf %llu, data list %#llx",
1996                                     root_node->val, ref_node->val,
1997                                     ref_node->aux);
1998                         ret = iterate_leaf_refs(fs_info,
1999                                                 (struct extent_inode_elem *)
2000                                                 (uintptr_t)ref_node->aux,
2001                                                 root_node->val,
2002                                                 extent_item_objectid,
2003                                                 iterate, ctx);
2004                 }
2005                 ulist_free(roots);
2006         }
2007
2008         free_leaf_list(refs);
2009 out:
2010         if (trans) {
2011                 btrfs_put_tree_mod_seq(fs_info, &seq_elem);
2012                 btrfs_end_transaction(trans);
2013         } else {
2014                 up_read(&fs_info->commit_root_sem);
2015         }
2016
2017         return ret;
2018 }
2019
2020 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
2021                                 struct btrfs_path *path,
2022                                 iterate_extent_inodes_t *iterate, void *ctx,
2023                                 bool ignore_offset)
2024 {
2025         int ret;
2026         u64 extent_item_pos;
2027         u64 flags = 0;
2028         struct btrfs_key found_key;
2029         int search_commit_root = path->search_commit_root;
2030
2031         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
2032         btrfs_release_path(path);
2033         if (ret < 0)
2034                 return ret;
2035         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
2036                 return -EINVAL;
2037
2038         extent_item_pos = logical - found_key.objectid;
2039         ret = iterate_extent_inodes(fs_info, found_key.objectid,
2040                                         extent_item_pos, search_commit_root,
2041                                         iterate, ctx, ignore_offset);
2042
2043         return ret;
2044 }
2045
2046 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
2047                               struct extent_buffer *eb, void *ctx);
2048
2049 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
2050                               struct btrfs_path *path,
2051                               iterate_irefs_t *iterate, void *ctx)
2052 {
2053         int ret = 0;
2054         int slot;
2055         u32 cur;
2056         u32 len;
2057         u32 name_len;
2058         u64 parent = 0;
2059         int found = 0;
2060         struct extent_buffer *eb;
2061         struct btrfs_item *item;
2062         struct btrfs_inode_ref *iref;
2063         struct btrfs_key found_key;
2064
2065         while (!ret) {
2066                 ret = btrfs_find_item(fs_root, path, inum,
2067                                 parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
2068                                 &found_key);
2069
2070                 if (ret < 0)
2071                         break;
2072                 if (ret) {
2073                         ret = found ? 0 : -ENOENT;
2074                         break;
2075                 }
2076                 ++found;
2077
2078                 parent = found_key.offset;
2079                 slot = path->slots[0];
2080                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2081                 if (!eb) {
2082                         ret = -ENOMEM;
2083                         break;
2084                 }
2085                 btrfs_release_path(path);
2086
2087                 item = btrfs_item_nr(slot);
2088                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2089
2090                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
2091                         name_len = btrfs_inode_ref_name_len(eb, iref);
2092                         /* path must be released before calling iterate()! */
2093                         btrfs_debug(fs_root->fs_info,
2094                                 "following ref at offset %u for inode %llu in tree %llu",
2095                                 cur, found_key.objectid,
2096                                 fs_root->root_key.objectid);
2097                         ret = iterate(parent, name_len,
2098                                       (unsigned long)(iref + 1), eb, ctx);
2099                         if (ret)
2100                                 break;
2101                         len = sizeof(*iref) + name_len;
2102                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
2103                 }
2104                 free_extent_buffer(eb);
2105         }
2106
2107         btrfs_release_path(path);
2108
2109         return ret;
2110 }
2111
2112 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
2113                                  struct btrfs_path *path,
2114                                  iterate_irefs_t *iterate, void *ctx)
2115 {
2116         int ret;
2117         int slot;
2118         u64 offset = 0;
2119         u64 parent;
2120         int found = 0;
2121         struct extent_buffer *eb;
2122         struct btrfs_inode_extref *extref;
2123         u32 item_size;
2124         u32 cur_offset;
2125         unsigned long ptr;
2126
2127         while (1) {
2128                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
2129                                             &offset);
2130                 if (ret < 0)
2131                         break;
2132                 if (ret) {
2133                         ret = found ? 0 : -ENOENT;
2134                         break;
2135                 }
2136                 ++found;
2137
2138                 slot = path->slots[0];
2139                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2140                 if (!eb) {
2141                         ret = -ENOMEM;
2142                         break;
2143                 }
2144                 btrfs_release_path(path);
2145
2146                 item_size = btrfs_item_size_nr(eb, slot);
2147                 ptr = btrfs_item_ptr_offset(eb, slot);
2148                 cur_offset = 0;
2149
2150                 while (cur_offset < item_size) {
2151                         u32 name_len;
2152
2153                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
2154                         parent = btrfs_inode_extref_parent(eb, extref);
2155                         name_len = btrfs_inode_extref_name_len(eb, extref);
2156                         ret = iterate(parent, name_len,
2157                                       (unsigned long)&extref->name, eb, ctx);
2158                         if (ret)
2159                                 break;
2160
2161                         cur_offset += btrfs_inode_extref_name_len(eb, extref);
2162                         cur_offset += sizeof(*extref);
2163                 }
2164                 free_extent_buffer(eb);
2165
2166                 offset++;
2167         }
2168
2169         btrfs_release_path(path);
2170
2171         return ret;
2172 }
2173
2174 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
2175                          struct btrfs_path *path, iterate_irefs_t *iterate,
2176                          void *ctx)
2177 {
2178         int ret;
2179         int found_refs = 0;
2180
2181         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
2182         if (!ret)
2183                 ++found_refs;
2184         else if (ret != -ENOENT)
2185                 return ret;
2186
2187         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
2188         if (ret == -ENOENT && found_refs)
2189                 return 0;
2190
2191         return ret;
2192 }
2193
2194 /*
2195  * returns 0 if the path could be dumped (probably truncated)
2196  * returns <0 in case of an error
2197  */
2198 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2199                          struct extent_buffer *eb, void *ctx)
2200 {
2201         struct inode_fs_paths *ipath = ctx;
2202         char *fspath;
2203         char *fspath_min;
2204         int i = ipath->fspath->elem_cnt;
2205         const int s_ptr = sizeof(char *);
2206         u32 bytes_left;
2207
2208         bytes_left = ipath->fspath->bytes_left > s_ptr ?
2209                                         ipath->fspath->bytes_left - s_ptr : 0;
2210
2211         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
2212         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
2213                                    name_off, eb, inum, fspath_min, bytes_left);
2214         if (IS_ERR(fspath))
2215                 return PTR_ERR(fspath);
2216
2217         if (fspath > fspath_min) {
2218                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
2219                 ++ipath->fspath->elem_cnt;
2220                 ipath->fspath->bytes_left = fspath - fspath_min;
2221         } else {
2222                 ++ipath->fspath->elem_missed;
2223                 ipath->fspath->bytes_missing += fspath_min - fspath;
2224                 ipath->fspath->bytes_left = 0;
2225         }
2226
2227         return 0;
2228 }
2229
2230 /*
2231  * this dumps all file system paths to the inode into the ipath struct, provided
2232  * is has been created large enough. each path is zero-terminated and accessed
2233  * from ipath->fspath->val[i].
2234  * when it returns, there are ipath->fspath->elem_cnt number of paths available
2235  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
2236  * number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
2237  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
2238  * have been needed to return all paths.
2239  */
2240 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
2241 {
2242         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
2243                              inode_to_path, ipath);
2244 }
2245
2246 struct btrfs_data_container *init_data_container(u32 total_bytes)
2247 {
2248         struct btrfs_data_container *data;
2249         size_t alloc_bytes;
2250
2251         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
2252         data = kvmalloc(alloc_bytes, GFP_KERNEL);
2253         if (!data)
2254                 return ERR_PTR(-ENOMEM);
2255
2256         if (total_bytes >= sizeof(*data)) {
2257                 data->bytes_left = total_bytes - sizeof(*data);
2258                 data->bytes_missing = 0;
2259         } else {
2260                 data->bytes_missing = sizeof(*data) - total_bytes;
2261                 data->bytes_left = 0;
2262         }
2263
2264         data->elem_cnt = 0;
2265         data->elem_missed = 0;
2266
2267         return data;
2268 }
2269
2270 /*
2271  * allocates space to return multiple file system paths for an inode.
2272  * total_bytes to allocate are passed, note that space usable for actual path
2273  * information will be total_bytes - sizeof(struct inode_fs_paths).
2274  * the returned pointer must be freed with free_ipath() in the end.
2275  */
2276 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
2277                                         struct btrfs_path *path)
2278 {
2279         struct inode_fs_paths *ifp;
2280         struct btrfs_data_container *fspath;
2281
2282         fspath = init_data_container(total_bytes);
2283         if (IS_ERR(fspath))
2284                 return ERR_CAST(fspath);
2285
2286         ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
2287         if (!ifp) {
2288                 kvfree(fspath);
2289                 return ERR_PTR(-ENOMEM);
2290         }
2291
2292         ifp->btrfs_path = path;
2293         ifp->fspath = fspath;
2294         ifp->fs_root = fs_root;
2295
2296         return ifp;
2297 }
2298
2299 void free_ipath(struct inode_fs_paths *ipath)
2300 {
2301         if (!ipath)
2302                 return;
2303         kvfree(ipath->fspath);
2304         kfree(ipath);
2305 }
2306
2307 struct btrfs_backref_iter *btrfs_backref_iter_alloc(
2308                 struct btrfs_fs_info *fs_info, gfp_t gfp_flag)
2309 {
2310         struct btrfs_backref_iter *ret;
2311
2312         ret = kzalloc(sizeof(*ret), gfp_flag);
2313         if (!ret)
2314                 return NULL;
2315
2316         ret->path = btrfs_alloc_path();
2317         if (!ret->path) {
2318                 kfree(ret);
2319                 return NULL;
2320         }
2321
2322         /* Current backref iterator only supports iteration in commit root */
2323         ret->path->search_commit_root = 1;
2324         ret->path->skip_locking = 1;
2325         ret->fs_info = fs_info;
2326
2327         return ret;
2328 }
2329
2330 int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr)
2331 {
2332         struct btrfs_fs_info *fs_info = iter->fs_info;
2333         struct btrfs_path *path = iter->path;
2334         struct btrfs_extent_item *ei;
2335         struct btrfs_key key;
2336         int ret;
2337
2338         key.objectid = bytenr;
2339         key.type = BTRFS_METADATA_ITEM_KEY;
2340         key.offset = (u64)-1;
2341         iter->bytenr = bytenr;
2342
2343         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
2344         if (ret < 0)
2345                 return ret;
2346         if (ret == 0) {
2347                 ret = -EUCLEAN;
2348                 goto release;
2349         }
2350         if (path->slots[0] == 0) {
2351                 WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
2352                 ret = -EUCLEAN;
2353                 goto release;
2354         }
2355         path->slots[0]--;
2356
2357         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
2358         if ((key.type != BTRFS_EXTENT_ITEM_KEY &&
2359              key.type != BTRFS_METADATA_ITEM_KEY) || key.objectid != bytenr) {
2360                 ret = -ENOENT;
2361                 goto release;
2362         }
2363         memcpy(&iter->cur_key, &key, sizeof(key));
2364         iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2365                                                     path->slots[0]);
2366         iter->end_ptr = (u32)(iter->item_ptr +
2367                         btrfs_item_size_nr(path->nodes[0], path->slots[0]));
2368         ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
2369                             struct btrfs_extent_item);
2370
2371         /*
2372          * Only support iteration on tree backref yet.
2373          *
2374          * This is an extra precaution for non skinny-metadata, where
2375          * EXTENT_ITEM is also used for tree blocks, that we can only use
2376          * extent flags to determine if it's a tree block.
2377          */
2378         if (btrfs_extent_flags(path->nodes[0], ei) & BTRFS_EXTENT_FLAG_DATA) {
2379                 ret = -ENOTSUPP;
2380                 goto release;
2381         }
2382         iter->cur_ptr = (u32)(iter->item_ptr + sizeof(*ei));
2383
2384         /* If there is no inline backref, go search for keyed backref */
2385         if (iter->cur_ptr >= iter->end_ptr) {
2386                 ret = btrfs_next_item(fs_info->extent_root, path);
2387
2388                 /* No inline nor keyed ref */
2389                 if (ret > 0) {
2390                         ret = -ENOENT;
2391                         goto release;
2392                 }
2393                 if (ret < 0)
2394                         goto release;
2395
2396                 btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key,
2397                                 path->slots[0]);
2398                 if (iter->cur_key.objectid != bytenr ||
2399                     (iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
2400                      iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY)) {
2401                         ret = -ENOENT;
2402                         goto release;
2403                 }
2404                 iter->cur_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2405                                                            path->slots[0]);
2406                 iter->item_ptr = iter->cur_ptr;
2407                 iter->end_ptr = (u32)(iter->item_ptr + btrfs_item_size_nr(
2408                                       path->nodes[0], path->slots[0]));
2409         }
2410
2411         return 0;
2412 release:
2413         btrfs_backref_iter_release(iter);
2414         return ret;
2415 }
2416
2417 /*
2418  * Go to the next backref item of current bytenr, can be either inlined or
2419  * keyed.
2420  *
2421  * Caller needs to check whether it's inline ref or not by iter->cur_key.
2422  *
2423  * Return 0 if we get next backref without problem.
2424  * Return >0 if there is no extra backref for this bytenr.
2425  * Return <0 if there is something wrong happened.
2426  */
2427 int btrfs_backref_iter_next(struct btrfs_backref_iter *iter)
2428 {
2429         struct extent_buffer *eb = btrfs_backref_get_eb(iter);
2430         struct btrfs_path *path = iter->path;
2431         struct btrfs_extent_inline_ref *iref;
2432         int ret;
2433         u32 size;
2434
2435         if (btrfs_backref_iter_is_inline_ref(iter)) {
2436                 /* We're still inside the inline refs */
2437                 ASSERT(iter->cur_ptr < iter->end_ptr);
2438
2439                 if (btrfs_backref_has_tree_block_info(iter)) {
2440                         /* First tree block info */
2441                         size = sizeof(struct btrfs_tree_block_info);
2442                 } else {
2443                         /* Use inline ref type to determine the size */
2444                         int type;
2445
2446                         iref = (struct btrfs_extent_inline_ref *)
2447                                 ((unsigned long)iter->cur_ptr);
2448                         type = btrfs_extent_inline_ref_type(eb, iref);
2449
2450                         size = btrfs_extent_inline_ref_size(type);
2451                 }
2452                 iter->cur_ptr += size;
2453                 if (iter->cur_ptr < iter->end_ptr)
2454                         return 0;
2455
2456                 /* All inline items iterated, fall through */
2457         }
2458
2459         /* We're at keyed items, there is no inline item, go to the next one */
2460         ret = btrfs_next_item(iter->fs_info->extent_root, iter->path);
2461         if (ret)
2462                 return ret;
2463
2464         btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key, path->slots[0]);
2465         if (iter->cur_key.objectid != iter->bytenr ||
2466             (iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
2467              iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY))
2468                 return 1;
2469         iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2470                                         path->slots[0]);
2471         iter->cur_ptr = iter->item_ptr;
2472         iter->end_ptr = iter->item_ptr + (u32)btrfs_item_size_nr(path->nodes[0],
2473                                                 path->slots[0]);
2474         return 0;
2475 }
2476
2477 void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
2478                               struct btrfs_backref_cache *cache, int is_reloc)
2479 {
2480         int i;
2481
2482         cache->rb_root = RB_ROOT;
2483         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
2484                 INIT_LIST_HEAD(&cache->pending[i]);
2485         INIT_LIST_HEAD(&cache->changed);
2486         INIT_LIST_HEAD(&cache->detached);
2487         INIT_LIST_HEAD(&cache->leaves);
2488         INIT_LIST_HEAD(&cache->pending_edge);
2489         INIT_LIST_HEAD(&cache->useless_node);
2490         cache->fs_info = fs_info;
2491         cache->is_reloc = is_reloc;
2492 }
2493
2494 struct btrfs_backref_node *btrfs_backref_alloc_node(
2495                 struct btrfs_backref_cache *cache, u64 bytenr, int level)
2496 {
2497         struct btrfs_backref_node *node;
2498
2499         ASSERT(level >= 0 && level < BTRFS_MAX_LEVEL);
2500         node = kzalloc(sizeof(*node), GFP_NOFS);
2501         if (!node)
2502                 return node;
2503
2504         INIT_LIST_HEAD(&node->list);
2505         INIT_LIST_HEAD(&node->upper);
2506         INIT_LIST_HEAD(&node->lower);
2507         RB_CLEAR_NODE(&node->rb_node);
2508         cache->nr_nodes++;
2509         node->level = level;
2510         node->bytenr = bytenr;
2511
2512         return node;
2513 }
2514
2515 struct btrfs_backref_edge *btrfs_backref_alloc_edge(
2516                 struct btrfs_backref_cache *cache)
2517 {
2518         struct btrfs_backref_edge *edge;
2519
2520         edge = kzalloc(sizeof(*edge), GFP_NOFS);
2521         if (edge)
2522                 cache->nr_edges++;
2523         return edge;
2524 }
2525
2526 /*
2527  * Drop the backref node from cache, also cleaning up all its
2528  * upper edges and any uncached nodes in the path.
2529  *
2530  * This cleanup happens bottom up, thus the node should either
2531  * be the lowest node in the cache or a detached node.
2532  */
2533 void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
2534                                 struct btrfs_backref_node *node)
2535 {
2536         struct btrfs_backref_node *upper;
2537         struct btrfs_backref_edge *edge;
2538
2539         if (!node)
2540                 return;
2541
2542         BUG_ON(!node->lowest && !node->detached);
2543         while (!list_empty(&node->upper)) {
2544                 edge = list_entry(node->upper.next, struct btrfs_backref_edge,
2545                                   list[LOWER]);
2546                 upper = edge->node[UPPER];
2547                 list_del(&edge->list[LOWER]);
2548                 list_del(&edge->list[UPPER]);
2549                 btrfs_backref_free_edge(cache, edge);
2550
2551                 /*
2552                  * Add the node to leaf node list if no other child block
2553                  * cached.
2554                  */
2555                 if (list_empty(&upper->lower)) {
2556                         list_add_tail(&upper->lower, &cache->leaves);
2557                         upper->lowest = 1;
2558                 }
2559         }
2560
2561         btrfs_backref_drop_node(cache, node);
2562 }
2563
2564 /*
2565  * Release all nodes/edges from current cache
2566  */
2567 void btrfs_backref_release_cache(struct btrfs_backref_cache *cache)
2568 {
2569         struct btrfs_backref_node *node;
2570         int i;
2571
2572         while (!list_empty(&cache->detached)) {
2573                 node = list_entry(cache->detached.next,
2574                                   struct btrfs_backref_node, list);
2575                 btrfs_backref_cleanup_node(cache, node);
2576         }
2577
2578         while (!list_empty(&cache->leaves)) {
2579                 node = list_entry(cache->leaves.next,
2580                                   struct btrfs_backref_node, lower);
2581                 btrfs_backref_cleanup_node(cache, node);
2582         }
2583
2584         cache->last_trans = 0;
2585
2586         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
2587                 ASSERT(list_empty(&cache->pending[i]));
2588         ASSERT(list_empty(&cache->pending_edge));
2589         ASSERT(list_empty(&cache->useless_node));
2590         ASSERT(list_empty(&cache->changed));
2591         ASSERT(list_empty(&cache->detached));
2592         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
2593         ASSERT(!cache->nr_nodes);
2594         ASSERT(!cache->nr_edges);
2595 }
2596
2597 /*
2598  * Handle direct tree backref
2599  *
2600  * Direct tree backref means, the backref item shows its parent bytenr
2601  * directly. This is for SHARED_BLOCK_REF backref (keyed or inlined).
2602  *
2603  * @ref_key:    The converted backref key.
2604  *              For keyed backref, it's the item key.
2605  *              For inlined backref, objectid is the bytenr,
2606  *              type is btrfs_inline_ref_type, offset is
2607  *              btrfs_inline_ref_offset.
2608  */
2609 static int handle_direct_tree_backref(struct btrfs_backref_cache *cache,
2610                                       struct btrfs_key *ref_key,
2611                                       struct btrfs_backref_node *cur)
2612 {
2613         struct btrfs_backref_edge *edge;
2614         struct btrfs_backref_node *upper;
2615         struct rb_node *rb_node;
2616
2617         ASSERT(ref_key->type == BTRFS_SHARED_BLOCK_REF_KEY);
2618
2619         /* Only reloc root uses backref pointing to itself */
2620         if (ref_key->objectid == ref_key->offset) {
2621                 struct btrfs_root *root;
2622
2623                 cur->is_reloc_root = 1;
2624                 /* Only reloc backref cache cares about a specific root */
2625                 if (cache->is_reloc) {
2626                         root = find_reloc_root(cache->fs_info, cur->bytenr);
2627                         if (!root)
2628                                 return -ENOENT;
2629                         cur->root = root;
2630                 } else {
2631                         /*
2632                          * For generic purpose backref cache, reloc root node
2633                          * is useless.
2634                          */
2635                         list_add(&cur->list, &cache->useless_node);
2636                 }
2637                 return 0;
2638         }
2639
2640         edge = btrfs_backref_alloc_edge(cache);
2641         if (!edge)
2642                 return -ENOMEM;
2643
2644         rb_node = rb_simple_search(&cache->rb_root, ref_key->offset);
2645         if (!rb_node) {
2646                 /* Parent node not yet cached */
2647                 upper = btrfs_backref_alloc_node(cache, ref_key->offset,
2648                                            cur->level + 1);
2649                 if (!upper) {
2650                         btrfs_backref_free_edge(cache, edge);
2651                         return -ENOMEM;
2652                 }
2653
2654                 /*
2655                  *  Backrefs for the upper level block isn't cached, add the
2656                  *  block to pending list
2657                  */
2658                 list_add_tail(&edge->list[UPPER], &cache->pending_edge);
2659         } else {
2660                 /* Parent node already cached */
2661                 upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
2662                 ASSERT(upper->checked);
2663                 INIT_LIST_HEAD(&edge->list[UPPER]);
2664         }
2665         btrfs_backref_link_edge(edge, cur, upper, LINK_LOWER);
2666         return 0;
2667 }
2668
2669 /*
2670  * Handle indirect tree backref
2671  *
2672  * Indirect tree backref means, we only know which tree the node belongs to.
2673  * We still need to do a tree search to find out the parents. This is for
2674  * TREE_BLOCK_REF backref (keyed or inlined).
2675  *
2676  * @ref_key:    The same as @ref_key in  handle_direct_tree_backref()
2677  * @tree_key:   The first key of this tree block.
2678  * @path:       A clean (released) path, to avoid allocating path every time
2679  *              the function get called.
2680  */
2681 static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache,
2682                                         struct btrfs_path *path,
2683                                         struct btrfs_key *ref_key,
2684                                         struct btrfs_key *tree_key,
2685                                         struct btrfs_backref_node *cur)
2686 {
2687         struct btrfs_fs_info *fs_info = cache->fs_info;
2688         struct btrfs_backref_node *upper;
2689         struct btrfs_backref_node *lower;
2690         struct btrfs_backref_edge *edge;
2691         struct extent_buffer *eb;
2692         struct btrfs_root *root;
2693         struct rb_node *rb_node;
2694         int level;
2695         bool need_check = true;
2696         int ret;
2697
2698         root = btrfs_get_fs_root(fs_info, ref_key->offset, false);
2699         if (IS_ERR(root))
2700                 return PTR_ERR(root);
2701         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
2702                 cur->cowonly = 1;
2703
2704         if (btrfs_root_level(&root->root_item) == cur->level) {
2705                 /* Tree root */
2706                 ASSERT(btrfs_root_bytenr(&root->root_item) == cur->bytenr);
2707                 /*
2708                  * For reloc backref cache, we may ignore reloc root.  But for
2709                  * general purpose backref cache, we can't rely on
2710                  * btrfs_should_ignore_reloc_root() as it may conflict with
2711                  * current running relocation and lead to missing root.
2712                  *
2713                  * For general purpose backref cache, reloc root detection is
2714                  * completely relying on direct backref (key->offset is parent
2715                  * bytenr), thus only do such check for reloc cache.
2716                  */
2717                 if (btrfs_should_ignore_reloc_root(root) && cache->is_reloc) {
2718                         btrfs_put_root(root);
2719                         list_add(&cur->list, &cache->useless_node);
2720                 } else {
2721                         cur->root = root;
2722                 }
2723                 return 0;
2724         }
2725
2726         level = cur->level + 1;
2727
2728         /* Search the tree to find parent blocks referring to the block */
2729         path->search_commit_root = 1;
2730         path->skip_locking = 1;
2731         path->lowest_level = level;
2732         ret = btrfs_search_slot(NULL, root, tree_key, path, 0, 0);
2733         path->lowest_level = 0;
2734         if (ret < 0) {
2735                 btrfs_put_root(root);
2736                 return ret;
2737         }
2738         if (ret > 0 && path->slots[level] > 0)
2739                 path->slots[level]--;
2740
2741         eb = path->nodes[level];
2742         if (btrfs_node_blockptr(eb, path->slots[level]) != cur->bytenr) {
2743                 btrfs_err(fs_info,
2744 "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
2745                           cur->bytenr, level - 1, root->root_key.objectid,
2746                           tree_key->objectid, tree_key->type, tree_key->offset);
2747                 btrfs_put_root(root);
2748                 ret = -ENOENT;
2749                 goto out;
2750         }
2751         lower = cur;
2752
2753         /* Add all nodes and edges in the path */
2754         for (; level < BTRFS_MAX_LEVEL; level++) {
2755                 if (!path->nodes[level]) {
2756                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
2757                                lower->bytenr);
2758                         /* Same as previous should_ignore_reloc_root() call */
2759                         if (btrfs_should_ignore_reloc_root(root) &&
2760                             cache->is_reloc) {
2761                                 btrfs_put_root(root);
2762                                 list_add(&lower->list, &cache->useless_node);
2763                         } else {
2764                                 lower->root = root;
2765                         }
2766                         break;
2767                 }
2768
2769                 edge = btrfs_backref_alloc_edge(cache);
2770                 if (!edge) {
2771                         btrfs_put_root(root);
2772                         ret = -ENOMEM;
2773                         goto out;
2774                 }
2775
2776                 eb = path->nodes[level];
2777                 rb_node = rb_simple_search(&cache->rb_root, eb->start);
2778                 if (!rb_node) {
2779                         upper = btrfs_backref_alloc_node(cache, eb->start,
2780                                                          lower->level + 1);
2781                         if (!upper) {
2782                                 btrfs_put_root(root);
2783                                 btrfs_backref_free_edge(cache, edge);
2784                                 ret = -ENOMEM;
2785                                 goto out;
2786                         }
2787                         upper->owner = btrfs_header_owner(eb);
2788                         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
2789                                 upper->cowonly = 1;
2790
2791                         /*
2792                          * If we know the block isn't shared we can avoid
2793                          * checking its backrefs.
2794                          */
2795                         if (btrfs_block_can_be_shared(root, eb))
2796                                 upper->checked = 0;
2797                         else
2798                                 upper->checked = 1;
2799
2800                         /*
2801                          * Add the block to pending list if we need to check its
2802                          * backrefs, we only do this once while walking up a
2803                          * tree as we will catch anything else later on.
2804                          */
2805                         if (!upper->checked && need_check) {
2806                                 need_check = false;
2807                                 list_add_tail(&edge->list[UPPER],
2808                                               &cache->pending_edge);
2809                         } else {
2810                                 if (upper->checked)
2811                                         need_check = true;
2812                                 INIT_LIST_HEAD(&edge->list[UPPER]);
2813                         }
2814                 } else {
2815                         upper = rb_entry(rb_node, struct btrfs_backref_node,
2816                                          rb_node);
2817                         ASSERT(upper->checked);
2818                         INIT_LIST_HEAD(&edge->list[UPPER]);
2819                         if (!upper->owner)
2820                                 upper->owner = btrfs_header_owner(eb);
2821                 }
2822                 btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
2823
2824                 if (rb_node) {
2825                         btrfs_put_root(root);
2826                         break;
2827                 }
2828                 lower = upper;
2829                 upper = NULL;
2830         }
2831 out:
2832         btrfs_release_path(path);
2833         return ret;
2834 }
2835
2836 /*
2837  * Add backref node @cur into @cache.
2838  *
2839  * NOTE: Even if the function returned 0, @cur is not yet cached as its upper
2840  *       links aren't yet bi-directional. Needs to finish such links.
2841  *       Use btrfs_backref_finish_upper_links() to finish such linkage.
2842  *
2843  * @path:       Released path for indirect tree backref lookup
2844  * @iter:       Released backref iter for extent tree search
2845  * @node_key:   The first key of the tree block
2846  */
2847 int btrfs_backref_add_tree_node(struct btrfs_backref_cache *cache,
2848                                 struct btrfs_path *path,
2849                                 struct btrfs_backref_iter *iter,
2850                                 struct btrfs_key *node_key,
2851                                 struct btrfs_backref_node *cur)
2852 {
2853         struct btrfs_fs_info *fs_info = cache->fs_info;
2854         struct btrfs_backref_edge *edge;
2855         struct btrfs_backref_node *exist;
2856         int ret;
2857
2858         ret = btrfs_backref_iter_start(iter, cur->bytenr);
2859         if (ret < 0)
2860                 return ret;
2861         /*
2862          * We skip the first btrfs_tree_block_info, as we don't use the key
2863          * stored in it, but fetch it from the tree block
2864          */
2865         if (btrfs_backref_has_tree_block_info(iter)) {
2866                 ret = btrfs_backref_iter_next(iter);
2867                 if (ret < 0)
2868                         goto out;
2869                 /* No extra backref? This means the tree block is corrupted */
2870                 if (ret > 0) {
2871                         ret = -EUCLEAN;
2872                         goto out;
2873                 }
2874         }
2875         WARN_ON(cur->checked);
2876         if (!list_empty(&cur->upper)) {
2877                 /*
2878                  * The backref was added previously when processing backref of
2879                  * type BTRFS_TREE_BLOCK_REF_KEY
2880                  */
2881                 ASSERT(list_is_singular(&cur->upper));
2882                 edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
2883                                   list[LOWER]);
2884                 ASSERT(list_empty(&edge->list[UPPER]));
2885                 exist = edge->node[UPPER];
2886                 /*
2887                  * Add the upper level block to pending list if we need check
2888                  * its backrefs
2889                  */
2890                 if (!exist->checked)
2891                         list_add_tail(&edge->list[UPPER], &cache->pending_edge);
2892         } else {
2893                 exist = NULL;
2894         }
2895
2896         for (; ret == 0; ret = btrfs_backref_iter_next(iter)) {
2897                 struct extent_buffer *eb;
2898                 struct btrfs_key key;
2899                 int type;
2900
2901                 cond_resched();
2902                 eb = btrfs_backref_get_eb(iter);
2903
2904                 key.objectid = iter->bytenr;
2905                 if (btrfs_backref_iter_is_inline_ref(iter)) {
2906                         struct btrfs_extent_inline_ref *iref;
2907
2908                         /* Update key for inline backref */
2909                         iref = (struct btrfs_extent_inline_ref *)
2910                                 ((unsigned long)iter->cur_ptr);
2911                         type = btrfs_get_extent_inline_ref_type(eb, iref,
2912                                                         BTRFS_REF_TYPE_BLOCK);
2913                         if (type == BTRFS_REF_TYPE_INVALID) {
2914                                 ret = -EUCLEAN;
2915                                 goto out;
2916                         }
2917                         key.type = type;
2918                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
2919                 } else {
2920                         key.type = iter->cur_key.type;
2921                         key.offset = iter->cur_key.offset;
2922                 }
2923
2924                 /*
2925                  * Parent node found and matches current inline ref, no need to
2926                  * rebuild this node for this inline ref
2927                  */
2928                 if (exist &&
2929                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
2930                       exist->owner == key.offset) ||
2931                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
2932                       exist->bytenr == key.offset))) {
2933                         exist = NULL;
2934                         continue;
2935                 }
2936
2937                 /* SHARED_BLOCK_REF means key.offset is the parent bytenr */
2938                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
2939                         ret = handle_direct_tree_backref(cache, &key, cur);
2940                         if (ret < 0)
2941                                 goto out;
2942                         continue;
2943                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
2944                         ret = -EINVAL;
2945                         btrfs_print_v0_err(fs_info);
2946                         btrfs_handle_fs_error(fs_info, ret, NULL);
2947                         goto out;
2948                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
2949                         continue;
2950                 }
2951
2952                 /*
2953                  * key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref offset
2954                  * means the root objectid. We need to search the tree to get
2955                  * its parent bytenr.
2956                  */
2957                 ret = handle_indirect_tree_backref(cache, path, &key, node_key,
2958                                                    cur);
2959                 if (ret < 0)
2960                         goto out;
2961         }
2962         ret = 0;
2963         cur->checked = 1;
2964         WARN_ON(exist);
2965 out:
2966         btrfs_backref_iter_release(iter);
2967         return ret;
2968 }
2969
2970 /*
2971  * Finish the upwards linkage created by btrfs_backref_add_tree_node()
2972  */
2973 int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
2974                                      struct btrfs_backref_node *start)
2975 {
2976         struct list_head *useless_node = &cache->useless_node;
2977         struct btrfs_backref_edge *edge;
2978         struct rb_node *rb_node;
2979         LIST_HEAD(pending_edge);
2980
2981         ASSERT(start->checked);
2982
2983         /* Insert this node to cache if it's not COW-only */
2984         if (!start->cowonly) {
2985                 rb_node = rb_simple_insert(&cache->rb_root, start->bytenr,
2986                                            &start->rb_node);
2987                 if (rb_node)
2988                         btrfs_backref_panic(cache->fs_info, start->bytenr,
2989                                             -EEXIST);
2990                 list_add_tail(&start->lower, &cache->leaves);
2991         }
2992
2993         /*
2994          * Use breadth first search to iterate all related edges.
2995          *
2996          * The starting points are all the edges of this node
2997          */
2998         list_for_each_entry(edge, &start->upper, list[LOWER])
2999                 list_add_tail(&edge->list[UPPER], &pending_edge);
3000
3001         while (!list_empty(&pending_edge)) {
3002                 struct btrfs_backref_node *upper;
3003                 struct btrfs_backref_node *lower;
3004
3005                 edge = list_first_entry(&pending_edge,
3006                                 struct btrfs_backref_edge, list[UPPER]);
3007                 list_del_init(&edge->list[UPPER]);
3008                 upper = edge->node[UPPER];
3009                 lower = edge->node[LOWER];
3010
3011                 /* Parent is detached, no need to keep any edges */
3012                 if (upper->detached) {
3013                         list_del(&edge->list[LOWER]);
3014                         btrfs_backref_free_edge(cache, edge);
3015
3016                         /* Lower node is orphan, queue for cleanup */
3017                         if (list_empty(&lower->upper))
3018                                 list_add(&lower->list, useless_node);
3019                         continue;
3020                 }
3021
3022                 /*
3023                  * All new nodes added in current build_backref_tree() haven't
3024                  * been linked to the cache rb tree.
3025                  * So if we have upper->rb_node populated, this means a cache
3026                  * hit. We only need to link the edge, as @upper and all its
3027                  * parents have already been linked.
3028                  */
3029                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
3030                         if (upper->lowest) {
3031                                 list_del_init(&upper->lower);
3032                                 upper->lowest = 0;
3033                         }
3034
3035                         list_add_tail(&edge->list[UPPER], &upper->lower);
3036                         continue;
3037                 }
3038
3039                 /* Sanity check, we shouldn't have any unchecked nodes */
3040                 if (!upper->checked) {
3041                         ASSERT(0);
3042                         return -EUCLEAN;
3043                 }
3044
3045                 /* Sanity check, COW-only node has non-COW-only parent */
3046                 if (start->cowonly != upper->cowonly) {
3047                         ASSERT(0);
3048                         return -EUCLEAN;
3049                 }
3050
3051                 /* Only cache non-COW-only (subvolume trees) tree blocks */
3052                 if (!upper->cowonly) {
3053                         rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
3054                                                    &upper->rb_node);
3055                         if (rb_node) {
3056                                 btrfs_backref_panic(cache->fs_info,
3057                                                 upper->bytenr, -EEXIST);
3058                                 return -EUCLEAN;
3059                         }
3060                 }
3061
3062                 list_add_tail(&edge->list[UPPER], &upper->lower);
3063
3064                 /*
3065                  * Also queue all the parent edges of this uncached node
3066                  * to finish the upper linkage
3067                  */
3068                 list_for_each_entry(edge, &upper->upper, list[LOWER])
3069                         list_add_tail(&edge->list[UPPER], &pending_edge);
3070         }
3071         return 0;
3072 }
3073
3074 void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
3075                                  struct btrfs_backref_node *node)
3076 {
3077         struct btrfs_backref_node *lower;
3078         struct btrfs_backref_node *upper;
3079         struct btrfs_backref_edge *edge;
3080
3081         while (!list_empty(&cache->useless_node)) {
3082                 lower = list_first_entry(&cache->useless_node,
3083                                    struct btrfs_backref_node, list);
3084                 list_del_init(&lower->list);
3085         }
3086         while (!list_empty(&cache->pending_edge)) {
3087                 edge = list_first_entry(&cache->pending_edge,
3088                                 struct btrfs_backref_edge, list[UPPER]);
3089                 list_del(&edge->list[UPPER]);
3090                 list_del(&edge->list[LOWER]);
3091                 lower = edge->node[LOWER];
3092                 upper = edge->node[UPPER];
3093                 btrfs_backref_free_edge(cache, edge);
3094
3095                 /*
3096                  * Lower is no longer linked to any upper backref nodes and
3097                  * isn't in the cache, we can free it ourselves.
3098                  */
3099                 if (list_empty(&lower->upper) &&
3100                     RB_EMPTY_NODE(&lower->rb_node))
3101                         list_add(&lower->list, &cache->useless_node);
3102
3103                 if (!RB_EMPTY_NODE(&upper->rb_node))
3104                         continue;
3105
3106                 /* Add this guy's upper edges to the list to process */
3107                 list_for_each_entry(edge, &upper->upper, list[LOWER])
3108                         list_add_tail(&edge->list[UPPER],
3109                                       &cache->pending_edge);
3110                 if (list_empty(&upper->upper))
3111                         list_add(&upper->list, &cache->useless_node);
3112         }
3113
3114         while (!list_empty(&cache->useless_node)) {
3115                 lower = list_first_entry(&cache->useless_node,
3116                                    struct btrfs_backref_node, list);
3117                 list_del_init(&lower->list);
3118                 if (lower == node)
3119                         node = NULL;
3120                 btrfs_backref_drop_node(cache, lower);
3121         }
3122
3123         btrfs_backref_cleanup_node(cache, node);
3124         ASSERT(list_empty(&cache->useless_node) &&
3125                list_empty(&cache->pending_edge));
3126 }