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