11459fe84a2965f795cfe6be3f91b9805fb72354
[sfrench/cifs-2.6.git] / 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
17 /* Just an arbitrary number so we can be sure this happened */
18 #define BACKREF_FOUND_SHARED 6
19
20 struct extent_inode_elem {
21         u64 inum;
22         u64 offset;
23         struct extent_inode_elem *next;
24 };
25
26 static int check_extent_in_eb(const struct btrfs_key *key,
27                               const struct extent_buffer *eb,
28                               const struct btrfs_file_extent_item *fi,
29                               u64 extent_item_pos,
30                               struct extent_inode_elem **eie,
31                               bool ignore_offset)
32 {
33         u64 offset = 0;
34         struct extent_inode_elem *e;
35
36         if (!ignore_offset &&
37             !btrfs_file_extent_compression(eb, fi) &&
38             !btrfs_file_extent_encryption(eb, fi) &&
39             !btrfs_file_extent_other_encoding(eb, fi)) {
40                 u64 data_offset;
41                 u64 data_len;
42
43                 data_offset = btrfs_file_extent_offset(eb, fi);
44                 data_len = btrfs_file_extent_num_bytes(eb, fi);
45
46                 if (extent_item_pos < data_offset ||
47                     extent_item_pos >= data_offset + data_len)
48                         return 1;
49                 offset = extent_item_pos - data_offset;
50         }
51
52         e = kmalloc(sizeof(*e), GFP_NOFS);
53         if (!e)
54                 return -ENOMEM;
55
56         e->next = *eie;
57         e->inum = key->objectid;
58         e->offset = key->offset + offset;
59         *eie = e;
60
61         return 0;
62 }
63
64 static void free_inode_elem_list(struct extent_inode_elem *eie)
65 {
66         struct extent_inode_elem *eie_next;
67
68         for (; eie; eie = eie_next) {
69                 eie_next = eie->next;
70                 kfree(eie);
71         }
72 }
73
74 static int find_extent_in_eb(const struct extent_buffer *eb,
75                              u64 wanted_disk_byte, u64 extent_item_pos,
76                              struct extent_inode_elem **eie,
77                              bool ignore_offset)
78 {
79         u64 disk_byte;
80         struct btrfs_key key;
81         struct btrfs_file_extent_item *fi;
82         int slot;
83         int nritems;
84         int extent_type;
85         int ret;
86
87         /*
88          * from the shared data ref, we only have the leaf but we need
89          * the key. thus, we must look into all items and see that we
90          * find one (some) with a reference to our extent item.
91          */
92         nritems = btrfs_header_nritems(eb);
93         for (slot = 0; slot < nritems; ++slot) {
94                 btrfs_item_key_to_cpu(eb, &key, slot);
95                 if (key.type != BTRFS_EXTENT_DATA_KEY)
96                         continue;
97                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
98                 extent_type = btrfs_file_extent_type(eb, fi);
99                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
100                         continue;
101                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
102                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
103                 if (disk_byte != wanted_disk_byte)
104                         continue;
105
106                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie, ignore_offset);
107                 if (ret < 0)
108                         return ret;
109         }
110
111         return 0;
112 }
113
114 struct preftree {
115         struct rb_root_cached root;
116         unsigned int count;
117 };
118
119 #define PREFTREE_INIT   { .root = RB_ROOT_CACHED, .count = 0 }
120
121 struct preftrees {
122         struct preftree direct;    /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
123         struct preftree indirect;  /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
124         struct preftree indirect_missing_keys;
125 };
126
127 /*
128  * Checks for a shared extent during backref search.
129  *
130  * The share_count tracks prelim_refs (direct and indirect) having a
131  * ref->count >0:
132  *  - incremented when a ref->count transitions to >0
133  *  - decremented when a ref->count transitions to <1
134  */
135 struct share_check {
136         u64 root_objectid;
137         u64 inum;
138         int share_count;
139 };
140
141 static inline int extent_is_shared(struct share_check *sc)
142 {
143         return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
144 }
145
146 static struct kmem_cache *btrfs_prelim_ref_cache;
147
148 int __init btrfs_prelim_ref_init(void)
149 {
150         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
151                                         sizeof(struct prelim_ref),
152                                         0,
153                                         SLAB_MEM_SPREAD,
154                                         NULL);
155         if (!btrfs_prelim_ref_cache)
156                 return -ENOMEM;
157         return 0;
158 }
159
160 void __cold btrfs_prelim_ref_exit(void)
161 {
162         kmem_cache_destroy(btrfs_prelim_ref_cache);
163 }
164
165 static void free_pref(struct prelim_ref *ref)
166 {
167         kmem_cache_free(btrfs_prelim_ref_cache, ref);
168 }
169
170 /*
171  * Return 0 when both refs are for the same block (and can be merged).
172  * A -1 return indicates ref1 is a 'lower' block than ref2, while 1
173  * indicates a 'higher' block.
174  */
175 static int prelim_ref_compare(struct prelim_ref *ref1,
176                               struct prelim_ref *ref2)
177 {
178         if (ref1->level < ref2->level)
179                 return -1;
180         if (ref1->level > ref2->level)
181                 return 1;
182         if (ref1->root_id < ref2->root_id)
183                 return -1;
184         if (ref1->root_id > ref2->root_id)
185                 return 1;
186         if (ref1->key_for_search.type < ref2->key_for_search.type)
187                 return -1;
188         if (ref1->key_for_search.type > ref2->key_for_search.type)
189                 return 1;
190         if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
191                 return -1;
192         if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
193                 return 1;
194         if (ref1->key_for_search.offset < ref2->key_for_search.offset)
195                 return -1;
196         if (ref1->key_for_search.offset > ref2->key_for_search.offset)
197                 return 1;
198         if (ref1->parent < ref2->parent)
199                 return -1;
200         if (ref1->parent > ref2->parent)
201                 return 1;
202
203         return 0;
204 }
205
206 static void update_share_count(struct share_check *sc, int oldcount,
207                                int newcount)
208 {
209         if ((!sc) || (oldcount == 0 && newcount < 1))
210                 return;
211
212         if (oldcount > 0 && newcount < 1)
213                 sc->share_count--;
214         else if (oldcount < 1 && newcount > 0)
215                 sc->share_count++;
216 }
217
218 /*
219  * Add @newref to the @root rbtree, merging identical refs.
220  *
221  * Callers should assume that newref has been freed after calling.
222  */
223 static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
224                               struct preftree *preftree,
225                               struct prelim_ref *newref,
226                               struct share_check *sc)
227 {
228         struct rb_root_cached *root;
229         struct rb_node **p;
230         struct rb_node *parent = NULL;
231         struct prelim_ref *ref;
232         int result;
233         bool leftmost = true;
234
235         root = &preftree->root;
236         p = &root->rb_root.rb_node;
237
238         while (*p) {
239                 parent = *p;
240                 ref = rb_entry(parent, struct prelim_ref, rbnode);
241                 result = prelim_ref_compare(ref, newref);
242                 if (result < 0) {
243                         p = &(*p)->rb_left;
244                 } else if (result > 0) {
245                         p = &(*p)->rb_right;
246                         leftmost = false;
247                 } else {
248                         /* Identical refs, merge them and free @newref */
249                         struct extent_inode_elem *eie = ref->inode_list;
250
251                         while (eie && eie->next)
252                                 eie = eie->next;
253
254                         if (!eie)
255                                 ref->inode_list = newref->inode_list;
256                         else
257                                 eie->next = newref->inode_list;
258                         trace_btrfs_prelim_ref_merge(fs_info, ref, newref,
259                                                      preftree->count);
260                         /*
261                          * A delayed ref can have newref->count < 0.
262                          * The ref->count is updated to follow any
263                          * BTRFS_[ADD|DROP]_DELAYED_REF actions.
264                          */
265                         update_share_count(sc, ref->count,
266                                            ref->count + newref->count);
267                         ref->count += newref->count;
268                         free_pref(newref);
269                         return;
270                 }
271         }
272
273         update_share_count(sc, 0, newref->count);
274         preftree->count++;
275         trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
276         rb_link_node(&newref->rbnode, parent, p);
277         rb_insert_color_cached(&newref->rbnode, root, leftmost);
278 }
279
280 /*
281  * Release the entire tree.  We don't care about internal consistency so
282  * just free everything and then reset the tree root.
283  */
284 static void prelim_release(struct preftree *preftree)
285 {
286         struct prelim_ref *ref, *next_ref;
287
288         rbtree_postorder_for_each_entry_safe(ref, next_ref,
289                                              &preftree->root.rb_root, rbnode)
290                 free_pref(ref);
291
292         preftree->root = RB_ROOT_CACHED;
293         preftree->count = 0;
294 }
295
296 /*
297  * the rules for all callers of this function are:
298  * - obtaining the parent is the goal
299  * - if you add a key, you must know that it is a correct key
300  * - if you cannot add the parent or a correct key, then we will look into the
301  *   block later to set a correct key
302  *
303  * delayed refs
304  * ============
305  *        backref type | shared | indirect | shared | indirect
306  * information         |   tree |     tree |   data |     data
307  * --------------------+--------+----------+--------+----------
308  *      parent logical |    y   |     -    |    -   |     -
309  *      key to resolve |    -   |     y    |    y   |     y
310  *  tree block logical |    -   |     -    |    -   |     -
311  *  root for resolving |    y   |     y    |    y   |     y
312  *
313  * - column 1:       we've the parent -> done
314  * - column 2, 3, 4: we use the key to find the parent
315  *
316  * on disk refs (inline or keyed)
317  * ==============================
318  *        backref type | shared | indirect | shared | indirect
319  * information         |   tree |     tree |   data |     data
320  * --------------------+--------+----------+--------+----------
321  *      parent logical |    y   |     -    |    y   |     -
322  *      key to resolve |    -   |     -    |    -   |     y
323  *  tree block logical |    y   |     y    |    y   |     y
324  *  root for resolving |    -   |     y    |    y   |     y
325  *
326  * - column 1, 3: we've the parent -> done
327  * - column 2:    we take the first key from the block to find the parent
328  *                (see add_missing_keys)
329  * - column 4:    we use the key to find the parent
330  *
331  * additional information that's available but not required to find the parent
332  * block might help in merging entries to gain some speed.
333  */
334 static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
335                           struct preftree *preftree, u64 root_id,
336                           const struct btrfs_key *key, int level, u64 parent,
337                           u64 wanted_disk_byte, int count,
338                           struct share_check *sc, gfp_t gfp_mask)
339 {
340         struct prelim_ref *ref;
341
342         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
343                 return 0;
344
345         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
346         if (!ref)
347                 return -ENOMEM;
348
349         ref->root_id = root_id;
350         if (key) {
351                 ref->key_for_search = *key;
352                 /*
353                  * We can often find data backrefs with an offset that is too
354                  * large (>= LLONG_MAX, maximum allowed file offset) due to
355                  * underflows when subtracting a file's offset with the data
356                  * offset of its corresponding extent data item. This can
357                  * happen for example in the clone ioctl.
358                  * So if we detect such case we set the search key's offset to
359                  * zero to make sure we will find the matching file extent item
360                  * at add_all_parents(), otherwise we will miss it because the
361                  * offset taken form the backref is much larger then the offset
362                  * of the file extent item. This can make us scan a very large
363                  * number of file extent items, but at least it will not make
364                  * us miss any.
365                  * This is an ugly workaround for a behaviour that should have
366                  * never existed, but it does and a fix for the clone ioctl
367                  * would touch a lot of places, cause backwards incompatibility
368                  * and would not fix the problem for extents cloned with older
369                  * kernels.
370                  */
371                 if (ref->key_for_search.type == BTRFS_EXTENT_DATA_KEY &&
372                     ref->key_for_search.offset >= LLONG_MAX)
373                         ref->key_for_search.offset = 0;
374         } else {
375                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
376         }
377
378         ref->inode_list = NULL;
379         ref->level = level;
380         ref->count = count;
381         ref->parent = parent;
382         ref->wanted_disk_byte = wanted_disk_byte;
383         prelim_ref_insert(fs_info, preftree, ref, sc);
384         return extent_is_shared(sc);
385 }
386
387 /* direct refs use root == 0, key == NULL */
388 static int add_direct_ref(const struct btrfs_fs_info *fs_info,
389                           struct preftrees *preftrees, int level, u64 parent,
390                           u64 wanted_disk_byte, int count,
391                           struct share_check *sc, gfp_t gfp_mask)
392 {
393         return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level,
394                               parent, wanted_disk_byte, count, sc, gfp_mask);
395 }
396
397 /* indirect refs use parent == 0 */
398 static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
399                             struct preftrees *preftrees, u64 root_id,
400                             const struct btrfs_key *key, int level,
401                             u64 wanted_disk_byte, int count,
402                             struct share_check *sc, gfp_t gfp_mask)
403 {
404         struct preftree *tree = &preftrees->indirect;
405
406         if (!key)
407                 tree = &preftrees->indirect_missing_keys;
408         return add_prelim_ref(fs_info, tree, root_id, key, level, 0,
409                               wanted_disk_byte, count, sc, gfp_mask);
410 }
411
412 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
413                            struct ulist *parents, struct prelim_ref *ref,
414                            int level, u64 time_seq, const u64 *extent_item_pos,
415                            u64 total_refs, bool ignore_offset)
416 {
417         int ret = 0;
418         int slot;
419         struct extent_buffer *eb;
420         struct btrfs_key key;
421         struct btrfs_key *key_for_search = &ref->key_for_search;
422         struct btrfs_file_extent_item *fi;
423         struct extent_inode_elem *eie = NULL, *old = NULL;
424         u64 disk_byte;
425         u64 wanted_disk_byte = ref->wanted_disk_byte;
426         u64 count = 0;
427
428         if (level != 0) {
429                 eb = path->nodes[level];
430                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
431                 if (ret < 0)
432                         return ret;
433                 return 0;
434         }
435
436         /*
437          * We normally enter this function with the path already pointing to
438          * the first item to check. But sometimes, we may enter it with
439          * slot==nritems. In that case, go to the next leaf before we continue.
440          */
441         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
442                 if (time_seq == SEQ_LAST)
443                         ret = btrfs_next_leaf(root, path);
444                 else
445                         ret = btrfs_next_old_leaf(root, path, time_seq);
446         }
447
448         while (!ret && count < total_refs) {
449                 eb = path->nodes[0];
450                 slot = path->slots[0];
451
452                 btrfs_item_key_to_cpu(eb, &key, slot);
453
454                 if (key.objectid != key_for_search->objectid ||
455                     key.type != BTRFS_EXTENT_DATA_KEY)
456                         break;
457
458                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
459                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
460
461                 if (disk_byte == wanted_disk_byte) {
462                         eie = NULL;
463                         old = NULL;
464                         count++;
465                         if (extent_item_pos) {
466                                 ret = check_extent_in_eb(&key, eb, fi,
467                                                 *extent_item_pos,
468                                                 &eie, ignore_offset);
469                                 if (ret < 0)
470                                         break;
471                         }
472                         if (ret > 0)
473                                 goto next;
474                         ret = ulist_add_merge_ptr(parents, eb->start,
475                                                   eie, (void **)&old, GFP_NOFS);
476                         if (ret < 0)
477                                 break;
478                         if (!ret && extent_item_pos) {
479                                 while (old->next)
480                                         old = old->next;
481                                 old->next = eie;
482                         }
483                         eie = NULL;
484                 }
485 next:
486                 if (time_seq == SEQ_LAST)
487                         ret = btrfs_next_item(root, path);
488                 else
489                         ret = btrfs_next_old_item(root, path, time_seq);
490         }
491
492         if (ret > 0)
493                 ret = 0;
494         else if (ret < 0)
495                 free_inode_elem_list(eie);
496         return ret;
497 }
498
499 /*
500  * resolve an indirect backref in the form (root_id, key, level)
501  * to a logical address
502  */
503 static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
504                                 struct btrfs_path *path, u64 time_seq,
505                                 struct prelim_ref *ref, struct ulist *parents,
506                                 const u64 *extent_item_pos, u64 total_refs,
507                                 bool ignore_offset)
508 {
509         struct btrfs_root *root;
510         struct btrfs_key root_key;
511         struct extent_buffer *eb;
512         int ret = 0;
513         int root_level;
514         int level = ref->level;
515         int index;
516
517         root_key.objectid = ref->root_id;
518         root_key.type = BTRFS_ROOT_ITEM_KEY;
519         root_key.offset = (u64)-1;
520
521         index = srcu_read_lock(&fs_info->subvol_srcu);
522
523         root = btrfs_get_fs_root(fs_info, &root_key, false);
524         if (IS_ERR(root)) {
525                 srcu_read_unlock(&fs_info->subvol_srcu, index);
526                 ret = PTR_ERR(root);
527                 goto out;
528         }
529
530         if (btrfs_is_testing(fs_info)) {
531                 srcu_read_unlock(&fs_info->subvol_srcu, index);
532                 ret = -ENOENT;
533                 goto out;
534         }
535
536         if (path->search_commit_root)
537                 root_level = btrfs_header_level(root->commit_root);
538         else if (time_seq == SEQ_LAST)
539                 root_level = btrfs_header_level(root->node);
540         else
541                 root_level = btrfs_old_root_level(root, time_seq);
542
543         if (root_level + 1 == level) {
544                 srcu_read_unlock(&fs_info->subvol_srcu, index);
545                 goto out;
546         }
547
548         path->lowest_level = level;
549         if (time_seq == SEQ_LAST)
550                 ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
551                                         0, 0);
552         else
553                 ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
554                                             time_seq);
555
556         /* root node has been locked, we can release @subvol_srcu safely here */
557         srcu_read_unlock(&fs_info->subvol_srcu, index);
558
559         btrfs_debug(fs_info,
560                 "search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
561                  ref->root_id, level, ref->count, ret,
562                  ref->key_for_search.objectid, ref->key_for_search.type,
563                  ref->key_for_search.offset);
564         if (ret < 0)
565                 goto out;
566
567         eb = path->nodes[level];
568         while (!eb) {
569                 if (WARN_ON(!level)) {
570                         ret = 1;
571                         goto out;
572                 }
573                 level--;
574                 eb = path->nodes[level];
575         }
576
577         ret = add_all_parents(root, path, parents, ref, level, time_seq,
578                               extent_item_pos, total_refs, ignore_offset);
579 out:
580         path->lowest_level = 0;
581         btrfs_release_path(path);
582         return ret;
583 }
584
585 static struct extent_inode_elem *
586 unode_aux_to_inode_list(struct ulist_node *node)
587 {
588         if (!node)
589                 return NULL;
590         return (struct extent_inode_elem *)(uintptr_t)node->aux;
591 }
592
593 /*
594  * We maintain three separate rbtrees: one for direct refs, one for
595  * indirect refs which have a key, and one for indirect refs which do not
596  * have a key. Each tree does merge on insertion.
597  *
598  * Once all of the references are located, we iterate over the tree of
599  * indirect refs with missing keys. An appropriate key is located and
600  * the ref is moved onto the tree for indirect refs. After all missing
601  * keys are thus located, we iterate over the indirect ref tree, resolve
602  * each reference, and then insert the resolved reference onto the
603  * direct tree (merging there too).
604  *
605  * New backrefs (i.e., for parent nodes) are added to the appropriate
606  * rbtree as they are encountered. The new backrefs are subsequently
607  * resolved as above.
608  */
609 static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
610                                  struct btrfs_path *path, u64 time_seq,
611                                  struct preftrees *preftrees,
612                                  const u64 *extent_item_pos, u64 total_refs,
613                                  struct share_check *sc, bool ignore_offset)
614 {
615         int err;
616         int ret = 0;
617         struct ulist *parents;
618         struct ulist_node *node;
619         struct ulist_iterator uiter;
620         struct rb_node *rnode;
621
622         parents = ulist_alloc(GFP_NOFS);
623         if (!parents)
624                 return -ENOMEM;
625
626         /*
627          * We could trade memory usage for performance here by iterating
628          * the tree, allocating new refs for each insertion, and then
629          * freeing the entire indirect tree when we're done.  In some test
630          * cases, the tree can grow quite large (~200k objects).
631          */
632         while ((rnode = rb_first_cached(&preftrees->indirect.root))) {
633                 struct prelim_ref *ref;
634
635                 ref = rb_entry(rnode, struct prelim_ref, rbnode);
636                 if (WARN(ref->parent,
637                          "BUG: direct ref found in indirect tree")) {
638                         ret = -EINVAL;
639                         goto out;
640                 }
641
642                 rb_erase_cached(&ref->rbnode, &preftrees->indirect.root);
643                 preftrees->indirect.count--;
644
645                 if (ref->count == 0) {
646                         free_pref(ref);
647                         continue;
648                 }
649
650                 if (sc && sc->root_objectid &&
651                     ref->root_id != sc->root_objectid) {
652                         free_pref(ref);
653                         ret = BACKREF_FOUND_SHARED;
654                         goto out;
655                 }
656                 err = resolve_indirect_ref(fs_info, path, time_seq, ref,
657                                            parents, extent_item_pos,
658                                            total_refs, ignore_offset);
659                 /*
660                  * we can only tolerate ENOENT,otherwise,we should catch error
661                  * and return directly.
662                  */
663                 if (err == -ENOENT) {
664                         prelim_ref_insert(fs_info, &preftrees->direct, ref,
665                                           NULL);
666                         continue;
667                 } else if (err) {
668                         free_pref(ref);
669                         ret = err;
670                         goto out;
671                 }
672
673                 /* we put the first parent into the ref at hand */
674                 ULIST_ITER_INIT(&uiter);
675                 node = ulist_next(parents, &uiter);
676                 ref->parent = node ? node->val : 0;
677                 ref->inode_list = unode_aux_to_inode_list(node);
678
679                 /* Add a prelim_ref(s) for any other parent(s). */
680                 while ((node = ulist_next(parents, &uiter))) {
681                         struct prelim_ref *new_ref;
682
683                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
684                                                    GFP_NOFS);
685                         if (!new_ref) {
686                                 free_pref(ref);
687                                 ret = -ENOMEM;
688                                 goto out;
689                         }
690                         memcpy(new_ref, ref, sizeof(*ref));
691                         new_ref->parent = node->val;
692                         new_ref->inode_list = unode_aux_to_inode_list(node);
693                         prelim_ref_insert(fs_info, &preftrees->direct,
694                                           new_ref, NULL);
695                 }
696
697                 /*
698                  * Now it's a direct ref, put it in the direct tree. We must
699                  * do this last because the ref could be merged/freed here.
700                  */
701                 prelim_ref_insert(fs_info, &preftrees->direct, ref, NULL);
702
703                 ulist_reinit(parents);
704                 cond_resched();
705         }
706 out:
707         ulist_free(parents);
708         return ret;
709 }
710
711 /*
712  * read tree blocks and add keys where required.
713  */
714 static int add_missing_keys(struct btrfs_fs_info *fs_info,
715                             struct preftrees *preftrees, bool lock)
716 {
717         struct prelim_ref *ref;
718         struct extent_buffer *eb;
719         struct preftree *tree = &preftrees->indirect_missing_keys;
720         struct rb_node *node;
721
722         while ((node = rb_first_cached(&tree->root))) {
723                 ref = rb_entry(node, struct prelim_ref, rbnode);
724                 rb_erase_cached(node, &tree->root);
725
726                 BUG_ON(ref->parent);    /* should not be a direct ref */
727                 BUG_ON(ref->key_for_search.type);
728                 BUG_ON(!ref->wanted_disk_byte);
729
730                 eb = read_tree_block(fs_info, ref->wanted_disk_byte, 0,
731                                      ref->level - 1, NULL);
732                 if (IS_ERR(eb)) {
733                         free_pref(ref);
734                         return PTR_ERR(eb);
735                 } else if (!extent_buffer_uptodate(eb)) {
736                         free_pref(ref);
737                         free_extent_buffer(eb);
738                         return -EIO;
739                 }
740                 if (lock)
741                         btrfs_tree_read_lock(eb);
742                 if (btrfs_header_level(eb) == 0)
743                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
744                 else
745                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
746                 if (lock)
747                         btrfs_tree_read_unlock(eb);
748                 free_extent_buffer(eb);
749                 prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
750                 cond_resched();
751         }
752         return 0;
753 }
754
755 /*
756  * add all currently queued delayed refs from this head whose seq nr is
757  * smaller or equal that seq to the list
758  */
759 static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
760                             struct btrfs_delayed_ref_head *head, u64 seq,
761                             struct preftrees *preftrees, u64 *total_refs,
762                             struct share_check *sc)
763 {
764         struct btrfs_delayed_ref_node *node;
765         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
766         struct btrfs_key key;
767         struct btrfs_key tmp_op_key;
768         struct rb_node *n;
769         int count;
770         int ret = 0;
771
772         if (extent_op && extent_op->update_key)
773                 btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
774
775         spin_lock(&head->lock);
776         for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
777                 node = rb_entry(n, struct btrfs_delayed_ref_node,
778                                 ref_node);
779                 if (node->seq > seq)
780                         continue;
781
782                 switch (node->action) {
783                 case BTRFS_ADD_DELAYED_EXTENT:
784                 case BTRFS_UPDATE_DELAYED_HEAD:
785                         WARN_ON(1);
786                         continue;
787                 case BTRFS_ADD_DELAYED_REF:
788                         count = node->ref_mod;
789                         break;
790                 case BTRFS_DROP_DELAYED_REF:
791                         count = node->ref_mod * -1;
792                         break;
793                 default:
794                         BUG_ON(1);
795                 }
796                 *total_refs += count;
797                 switch (node->type) {
798                 case BTRFS_TREE_BLOCK_REF_KEY: {
799                         /* NORMAL INDIRECT METADATA backref */
800                         struct btrfs_delayed_tree_ref *ref;
801
802                         ref = btrfs_delayed_node_to_tree_ref(node);
803                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
804                                                &tmp_op_key, ref->level + 1,
805                                                node->bytenr, count, sc,
806                                                GFP_ATOMIC);
807                         break;
808                 }
809                 case BTRFS_SHARED_BLOCK_REF_KEY: {
810                         /* SHARED DIRECT METADATA backref */
811                         struct btrfs_delayed_tree_ref *ref;
812
813                         ref = btrfs_delayed_node_to_tree_ref(node);
814
815                         ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
816                                              ref->parent, node->bytenr, count,
817                                              sc, GFP_ATOMIC);
818                         break;
819                 }
820                 case BTRFS_EXTENT_DATA_REF_KEY: {
821                         /* NORMAL INDIRECT DATA backref */
822                         struct btrfs_delayed_data_ref *ref;
823                         ref = btrfs_delayed_node_to_data_ref(node);
824
825                         key.objectid = ref->objectid;
826                         key.type = BTRFS_EXTENT_DATA_KEY;
827                         key.offset = ref->offset;
828
829                         /*
830                          * Found a inum that doesn't match our known inum, we
831                          * know it's shared.
832                          */
833                         if (sc && sc->inum && ref->objectid != sc->inum) {
834                                 ret = BACKREF_FOUND_SHARED;
835                                 goto out;
836                         }
837
838                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
839                                                &key, 0, node->bytenr, count, sc,
840                                                GFP_ATOMIC);
841                         break;
842                 }
843                 case BTRFS_SHARED_DATA_REF_KEY: {
844                         /* SHARED DIRECT FULL backref */
845                         struct btrfs_delayed_data_ref *ref;
846
847                         ref = btrfs_delayed_node_to_data_ref(node);
848
849                         ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
850                                              node->bytenr, count, sc,
851                                              GFP_ATOMIC);
852                         break;
853                 }
854                 default:
855                         WARN_ON(1);
856                 }
857                 /*
858                  * We must ignore BACKREF_FOUND_SHARED until all delayed
859                  * refs have been checked.
860                  */
861                 if (ret && (ret != BACKREF_FOUND_SHARED))
862                         break;
863         }
864         if (!ret)
865                 ret = extent_is_shared(sc);
866 out:
867         spin_unlock(&head->lock);
868         return ret;
869 }
870
871 /*
872  * add all inline backrefs for bytenr to the list
873  *
874  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
875  */
876 static int add_inline_refs(const struct btrfs_fs_info *fs_info,
877                            struct btrfs_path *path, u64 bytenr,
878                            int *info_level, struct preftrees *preftrees,
879                            u64 *total_refs, struct share_check *sc)
880 {
881         int ret = 0;
882         int slot;
883         struct extent_buffer *leaf;
884         struct btrfs_key key;
885         struct btrfs_key found_key;
886         unsigned long ptr;
887         unsigned long end;
888         struct btrfs_extent_item *ei;
889         u64 flags;
890         u64 item_size;
891
892         /*
893          * enumerate all inline refs
894          */
895         leaf = path->nodes[0];
896         slot = path->slots[0];
897
898         item_size = btrfs_item_size_nr(leaf, slot);
899         BUG_ON(item_size < sizeof(*ei));
900
901         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
902         flags = btrfs_extent_flags(leaf, ei);
903         *total_refs += btrfs_extent_refs(leaf, ei);
904         btrfs_item_key_to_cpu(leaf, &found_key, slot);
905
906         ptr = (unsigned long)(ei + 1);
907         end = (unsigned long)ei + item_size;
908
909         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
910             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
911                 struct btrfs_tree_block_info *info;
912
913                 info = (struct btrfs_tree_block_info *)ptr;
914                 *info_level = btrfs_tree_block_level(leaf, info);
915                 ptr += sizeof(struct btrfs_tree_block_info);
916                 BUG_ON(ptr > end);
917         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
918                 *info_level = found_key.offset;
919         } else {
920                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
921         }
922
923         while (ptr < end) {
924                 struct btrfs_extent_inline_ref *iref;
925                 u64 offset;
926                 int type;
927
928                 iref = (struct btrfs_extent_inline_ref *)ptr;
929                 type = btrfs_get_extent_inline_ref_type(leaf, iref,
930                                                         BTRFS_REF_TYPE_ANY);
931                 if (type == BTRFS_REF_TYPE_INVALID)
932                         return -EUCLEAN;
933
934                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
935
936                 switch (type) {
937                 case BTRFS_SHARED_BLOCK_REF_KEY:
938                         ret = add_direct_ref(fs_info, preftrees,
939                                              *info_level + 1, offset,
940                                              bytenr, 1, NULL, GFP_NOFS);
941                         break;
942                 case BTRFS_SHARED_DATA_REF_KEY: {
943                         struct btrfs_shared_data_ref *sdref;
944                         int count;
945
946                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
947                         count = btrfs_shared_data_ref_count(leaf, sdref);
948
949                         ret = add_direct_ref(fs_info, preftrees, 0, offset,
950                                              bytenr, count, sc, GFP_NOFS);
951                         break;
952                 }
953                 case BTRFS_TREE_BLOCK_REF_KEY:
954                         ret = add_indirect_ref(fs_info, preftrees, offset,
955                                                NULL, *info_level + 1,
956                                                bytenr, 1, NULL, GFP_NOFS);
957                         break;
958                 case BTRFS_EXTENT_DATA_REF_KEY: {
959                         struct btrfs_extent_data_ref *dref;
960                         int count;
961                         u64 root;
962
963                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
964                         count = btrfs_extent_data_ref_count(leaf, dref);
965                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
966                                                                       dref);
967                         key.type = BTRFS_EXTENT_DATA_KEY;
968                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
969
970                         if (sc && sc->inum && key.objectid != sc->inum) {
971                                 ret = BACKREF_FOUND_SHARED;
972                                 break;
973                         }
974
975                         root = btrfs_extent_data_ref_root(leaf, dref);
976
977                         ret = add_indirect_ref(fs_info, preftrees, root,
978                                                &key, 0, bytenr, count,
979                                                sc, GFP_NOFS);
980                         break;
981                 }
982                 default:
983                         WARN_ON(1);
984                 }
985                 if (ret)
986                         return ret;
987                 ptr += btrfs_extent_inline_ref_size(type);
988         }
989
990         return 0;
991 }
992
993 /*
994  * add all non-inline backrefs for bytenr to the list
995  *
996  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
997  */
998 static int add_keyed_refs(struct btrfs_fs_info *fs_info,
999                           struct btrfs_path *path, u64 bytenr,
1000                           int info_level, struct preftrees *preftrees,
1001                           struct share_check *sc)
1002 {
1003         struct btrfs_root *extent_root = fs_info->extent_root;
1004         int ret;
1005         int slot;
1006         struct extent_buffer *leaf;
1007         struct btrfs_key key;
1008
1009         while (1) {
1010                 ret = btrfs_next_item(extent_root, path);
1011                 if (ret < 0)
1012                         break;
1013                 if (ret) {
1014                         ret = 0;
1015                         break;
1016                 }
1017
1018                 slot = path->slots[0];
1019                 leaf = path->nodes[0];
1020                 btrfs_item_key_to_cpu(leaf, &key, slot);
1021
1022                 if (key.objectid != bytenr)
1023                         break;
1024                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
1025                         continue;
1026                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
1027                         break;
1028
1029                 switch (key.type) {
1030                 case BTRFS_SHARED_BLOCK_REF_KEY:
1031                         /* SHARED DIRECT METADATA backref */
1032                         ret = add_direct_ref(fs_info, preftrees,
1033                                              info_level + 1, key.offset,
1034                                              bytenr, 1, NULL, GFP_NOFS);
1035                         break;
1036                 case BTRFS_SHARED_DATA_REF_KEY: {
1037                         /* SHARED DIRECT FULL backref */
1038                         struct btrfs_shared_data_ref *sdref;
1039                         int count;
1040
1041                         sdref = btrfs_item_ptr(leaf, slot,
1042                                               struct btrfs_shared_data_ref);
1043                         count = btrfs_shared_data_ref_count(leaf, sdref);
1044                         ret = add_direct_ref(fs_info, preftrees, 0,
1045                                              key.offset, bytenr, count,
1046                                              sc, GFP_NOFS);
1047                         break;
1048                 }
1049                 case BTRFS_TREE_BLOCK_REF_KEY:
1050                         /* NORMAL INDIRECT METADATA backref */
1051                         ret = add_indirect_ref(fs_info, preftrees, key.offset,
1052                                                NULL, info_level + 1, bytenr,
1053                                                1, NULL, GFP_NOFS);
1054                         break;
1055                 case BTRFS_EXTENT_DATA_REF_KEY: {
1056                         /* NORMAL INDIRECT DATA backref */
1057                         struct btrfs_extent_data_ref *dref;
1058                         int count;
1059                         u64 root;
1060
1061                         dref = btrfs_item_ptr(leaf, slot,
1062                                               struct btrfs_extent_data_ref);
1063                         count = btrfs_extent_data_ref_count(leaf, dref);
1064                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1065                                                                       dref);
1066                         key.type = BTRFS_EXTENT_DATA_KEY;
1067                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1068
1069                         if (sc && sc->inum && key.objectid != sc->inum) {
1070                                 ret = BACKREF_FOUND_SHARED;
1071                                 break;
1072                         }
1073
1074                         root = btrfs_extent_data_ref_root(leaf, dref);
1075                         ret = add_indirect_ref(fs_info, preftrees, root,
1076                                                &key, 0, bytenr, count,
1077                                                sc, GFP_NOFS);
1078                         break;
1079                 }
1080                 default:
1081                         WARN_ON(1);
1082                 }
1083                 if (ret)
1084                         return ret;
1085
1086         }
1087
1088         return ret;
1089 }
1090
1091 /*
1092  * this adds all existing backrefs (inline backrefs, backrefs and delayed
1093  * refs) for the given bytenr to the refs list, merges duplicates and resolves
1094  * indirect refs to their parent bytenr.
1095  * When roots are found, they're added to the roots list
1096  *
1097  * If time_seq is set to SEQ_LAST, it will not search delayed_refs, and behave
1098  * much like trans == NULL case, the difference only lies in it will not
1099  * commit root.
1100  * The special case is for qgroup to search roots in commit_transaction().
1101  *
1102  * @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a
1103  * shared extent is detected.
1104  *
1105  * Otherwise this returns 0 for success and <0 for an error.
1106  *
1107  * If ignore_offset is set to false, only extent refs whose offsets match
1108  * extent_item_pos are returned.  If true, every extent ref is returned
1109  * and extent_item_pos is ignored.
1110  *
1111  * FIXME some caching might speed things up
1112  */
1113 static int find_parent_nodes(struct btrfs_trans_handle *trans,
1114                              struct btrfs_fs_info *fs_info, u64 bytenr,
1115                              u64 time_seq, struct ulist *refs,
1116                              struct ulist *roots, const u64 *extent_item_pos,
1117                              struct share_check *sc, bool ignore_offset)
1118 {
1119         struct btrfs_key key;
1120         struct btrfs_path *path;
1121         struct btrfs_delayed_ref_root *delayed_refs = NULL;
1122         struct btrfs_delayed_ref_head *head;
1123         int info_level = 0;
1124         int ret;
1125         struct prelim_ref *ref;
1126         struct rb_node *node;
1127         struct extent_inode_elem *eie = NULL;
1128         /* total of both direct AND indirect refs! */
1129         u64 total_refs = 0;
1130         struct preftrees preftrees = {
1131                 .direct = PREFTREE_INIT,
1132                 .indirect = PREFTREE_INIT,
1133                 .indirect_missing_keys = PREFTREE_INIT
1134         };
1135
1136         key.objectid = bytenr;
1137         key.offset = (u64)-1;
1138         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1139                 key.type = BTRFS_METADATA_ITEM_KEY;
1140         else
1141                 key.type = BTRFS_EXTENT_ITEM_KEY;
1142
1143         path = btrfs_alloc_path();
1144         if (!path)
1145                 return -ENOMEM;
1146         if (!trans) {
1147                 path->search_commit_root = 1;
1148                 path->skip_locking = 1;
1149         }
1150
1151         if (time_seq == SEQ_LAST)
1152                 path->skip_locking = 1;
1153
1154         /*
1155          * grab both a lock on the path and a lock on the delayed ref head.
1156          * We need both to get a consistent picture of how the refs look
1157          * at a specified point in time
1158          */
1159 again:
1160         head = NULL;
1161
1162         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
1163         if (ret < 0)
1164                 goto out;
1165         BUG_ON(ret == 0);
1166
1167 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
1168         if (trans && likely(trans->type != __TRANS_DUMMY) &&
1169             time_seq != SEQ_LAST) {
1170 #else
1171         if (trans && time_seq != SEQ_LAST) {
1172 #endif
1173                 /*
1174                  * look if there are updates for this ref queued and lock the
1175                  * head
1176                  */
1177                 delayed_refs = &trans->transaction->delayed_refs;
1178                 spin_lock(&delayed_refs->lock);
1179                 head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
1180                 if (head) {
1181                         if (!mutex_trylock(&head->mutex)) {
1182                                 refcount_inc(&head->refs);
1183                                 spin_unlock(&delayed_refs->lock);
1184
1185                                 btrfs_release_path(path);
1186
1187                                 /*
1188                                  * Mutex was contended, block until it's
1189                                  * released and try again
1190                                  */
1191                                 mutex_lock(&head->mutex);
1192                                 mutex_unlock(&head->mutex);
1193                                 btrfs_put_delayed_ref_head(head);
1194                                 goto again;
1195                         }
1196                         spin_unlock(&delayed_refs->lock);
1197                         ret = add_delayed_refs(fs_info, head, time_seq,
1198                                                &preftrees, &total_refs, sc);
1199                         mutex_unlock(&head->mutex);
1200                         if (ret)
1201                                 goto out;
1202                 } else {
1203                         spin_unlock(&delayed_refs->lock);
1204                 }
1205         }
1206
1207         if (path->slots[0]) {
1208                 struct extent_buffer *leaf;
1209                 int slot;
1210
1211                 path->slots[0]--;
1212                 leaf = path->nodes[0];
1213                 slot = path->slots[0];
1214                 btrfs_item_key_to_cpu(leaf, &key, slot);
1215                 if (key.objectid == bytenr &&
1216                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
1217                      key.type == BTRFS_METADATA_ITEM_KEY)) {
1218                         ret = add_inline_refs(fs_info, path, bytenr,
1219                                               &info_level, &preftrees,
1220                                               &total_refs, sc);
1221                         if (ret)
1222                                 goto out;
1223                         ret = add_keyed_refs(fs_info, path, bytenr, info_level,
1224                                              &preftrees, sc);
1225                         if (ret)
1226                                 goto out;
1227                 }
1228         }
1229
1230         btrfs_release_path(path);
1231
1232         ret = add_missing_keys(fs_info, &preftrees, path->skip_locking == 0);
1233         if (ret)
1234                 goto out;
1235
1236         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
1237
1238         ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
1239                                     extent_item_pos, total_refs, sc, ignore_offset);
1240         if (ret)
1241                 goto out;
1242
1243         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
1244
1245         /*
1246          * This walks the tree of merged and resolved refs. Tree blocks are
1247          * read in as needed. Unique entries are added to the ulist, and
1248          * the list of found roots is updated.
1249          *
1250          * We release the entire tree in one go before returning.
1251          */
1252         node = rb_first_cached(&preftrees.direct.root);
1253         while (node) {
1254                 ref = rb_entry(node, struct prelim_ref, rbnode);
1255                 node = rb_next(&ref->rbnode);
1256                 /*
1257                  * ref->count < 0 can happen here if there are delayed
1258                  * refs with a node->action of BTRFS_DROP_DELAYED_REF.
1259                  * prelim_ref_insert() relies on this when merging
1260                  * identical refs to keep the overall count correct.
1261                  * prelim_ref_insert() will merge only those refs
1262                  * which compare identically.  Any refs having
1263                  * e.g. different offsets would not be merged,
1264                  * and would retain their original ref->count < 0.
1265                  */
1266                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1267                         if (sc && sc->root_objectid &&
1268                             ref->root_id != sc->root_objectid) {
1269                                 ret = BACKREF_FOUND_SHARED;
1270                                 goto out;
1271                         }
1272
1273                         /* no parent == root of tree */
1274                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1275                         if (ret < 0)
1276                                 goto out;
1277                 }
1278                 if (ref->count && ref->parent) {
1279                         if (extent_item_pos && !ref->inode_list &&
1280                             ref->level == 0) {
1281                                 struct extent_buffer *eb;
1282
1283                                 eb = read_tree_block(fs_info, ref->parent, 0,
1284                                                      ref->level, NULL);
1285                                 if (IS_ERR(eb)) {
1286                                         ret = PTR_ERR(eb);
1287                                         goto out;
1288                                 } else if (!extent_buffer_uptodate(eb)) {
1289                                         free_extent_buffer(eb);
1290                                         ret = -EIO;
1291                                         goto out;
1292                                 }
1293
1294                                 if (!path->skip_locking) {
1295                                         btrfs_tree_read_lock(eb);
1296                                         btrfs_set_lock_blocking_read(eb);
1297                                 }
1298                                 ret = find_extent_in_eb(eb, bytenr,
1299                                                         *extent_item_pos, &eie, ignore_offset);
1300                                 if (!path->skip_locking)
1301                                         btrfs_tree_read_unlock_blocking(eb);
1302                                 free_extent_buffer(eb);
1303                                 if (ret < 0)
1304                                         goto out;
1305                                 ref->inode_list = eie;
1306                         }
1307                         ret = ulist_add_merge_ptr(refs, ref->parent,
1308                                                   ref->inode_list,
1309                                                   (void **)&eie, GFP_NOFS);
1310                         if (ret < 0)
1311                                 goto out;
1312                         if (!ret && extent_item_pos) {
1313                                 /*
1314                                  * we've recorded that parent, so we must extend
1315                                  * its inode list here
1316                                  */
1317                                 BUG_ON(!eie);
1318                                 while (eie->next)
1319                                         eie = eie->next;
1320                                 eie->next = ref->inode_list;
1321                         }
1322                         eie = NULL;
1323                 }
1324                 cond_resched();
1325         }
1326
1327 out:
1328         btrfs_free_path(path);
1329
1330         prelim_release(&preftrees.direct);
1331         prelim_release(&preftrees.indirect);
1332         prelim_release(&preftrees.indirect_missing_keys);
1333
1334         if (ret < 0)
1335                 free_inode_elem_list(eie);
1336         return ret;
1337 }
1338
1339 static void free_leaf_list(struct ulist *blocks)
1340 {
1341         struct ulist_node *node = NULL;
1342         struct extent_inode_elem *eie;
1343         struct ulist_iterator uiter;
1344
1345         ULIST_ITER_INIT(&uiter);
1346         while ((node = ulist_next(blocks, &uiter))) {
1347                 if (!node->aux)
1348                         continue;
1349                 eie = unode_aux_to_inode_list(node);
1350                 free_inode_elem_list(eie);
1351                 node->aux = 0;
1352         }
1353
1354         ulist_free(blocks);
1355 }
1356
1357 /*
1358  * Finds all leafs with a reference to the specified combination of bytenr and
1359  * offset. key_list_head will point to a list of corresponding keys (caller must
1360  * free each list element). The leafs will be stored in the leafs ulist, which
1361  * must be freed with ulist_free.
1362  *
1363  * returns 0 on success, <0 on error
1364  */
1365 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1366                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1367                                 u64 time_seq, struct ulist **leafs,
1368                                 const u64 *extent_item_pos, bool ignore_offset)
1369 {
1370         int ret;
1371
1372         *leafs = ulist_alloc(GFP_NOFS);
1373         if (!*leafs)
1374                 return -ENOMEM;
1375
1376         ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1377                                 *leafs, NULL, extent_item_pos, NULL, ignore_offset);
1378         if (ret < 0 && ret != -ENOENT) {
1379                 free_leaf_list(*leafs);
1380                 return ret;
1381         }
1382
1383         return 0;
1384 }
1385
1386 /*
1387  * walk all backrefs for a given extent to find all roots that reference this
1388  * extent. Walking a backref means finding all extents that reference this
1389  * extent and in turn walk the backrefs of those, too. Naturally this is a
1390  * recursive process, but here it is implemented in an iterative fashion: We
1391  * find all referencing extents for the extent in question and put them on a
1392  * list. In turn, we find all referencing extents for those, further appending
1393  * to the list. The way we iterate the list allows adding more elements after
1394  * the current while iterating. The process stops when we reach the end of the
1395  * list. Found roots are added to the roots list.
1396  *
1397  * returns 0 on success, < 0 on error.
1398  */
1399 static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
1400                                      struct btrfs_fs_info *fs_info, u64 bytenr,
1401                                      u64 time_seq, struct ulist **roots,
1402                                      bool ignore_offset)
1403 {
1404         struct ulist *tmp;
1405         struct ulist_node *node = NULL;
1406         struct ulist_iterator uiter;
1407         int ret;
1408
1409         tmp = ulist_alloc(GFP_NOFS);
1410         if (!tmp)
1411                 return -ENOMEM;
1412         *roots = ulist_alloc(GFP_NOFS);
1413         if (!*roots) {
1414                 ulist_free(tmp);
1415                 return -ENOMEM;
1416         }
1417
1418         ULIST_ITER_INIT(&uiter);
1419         while (1) {
1420                 ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1421                                         tmp, *roots, NULL, NULL, ignore_offset);
1422                 if (ret < 0 && ret != -ENOENT) {
1423                         ulist_free(tmp);
1424                         ulist_free(*roots);
1425                         return ret;
1426                 }
1427                 node = ulist_next(tmp, &uiter);
1428                 if (!node)
1429                         break;
1430                 bytenr = node->val;
1431                 cond_resched();
1432         }
1433
1434         ulist_free(tmp);
1435         return 0;
1436 }
1437
1438 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1439                          struct btrfs_fs_info *fs_info, u64 bytenr,
1440                          u64 time_seq, struct ulist **roots,
1441                          bool ignore_offset)
1442 {
1443         int ret;
1444
1445         if (!trans)
1446                 down_read(&fs_info->commit_root_sem);
1447         ret = btrfs_find_all_roots_safe(trans, fs_info, bytenr,
1448                                         time_seq, roots, ignore_offset);
1449         if (!trans)
1450                 up_read(&fs_info->commit_root_sem);
1451         return ret;
1452 }
1453
1454 /**
1455  * btrfs_check_shared - tell us whether an extent is shared
1456  *
1457  * btrfs_check_shared uses the backref walking code but will short
1458  * circuit as soon as it finds a root or inode that doesn't match the
1459  * one passed in. This provides a significant performance benefit for
1460  * callers (such as fiemap) which want to know whether the extent is
1461  * shared but do not need a ref count.
1462  *
1463  * This attempts to allocate a transaction in order to account for
1464  * delayed refs, but continues on even when the alloc fails.
1465  *
1466  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1467  */
1468 int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
1469 {
1470         struct btrfs_fs_info *fs_info = root->fs_info;
1471         struct btrfs_trans_handle *trans;
1472         struct ulist *tmp = NULL;
1473         struct ulist *roots = NULL;
1474         struct ulist_iterator uiter;
1475         struct ulist_node *node;
1476         struct seq_list elem = SEQ_LIST_INIT(elem);
1477         int ret = 0;
1478         struct share_check shared = {
1479                 .root_objectid = root->root_key.objectid,
1480                 .inum = inum,
1481                 .share_count = 0,
1482         };
1483
1484         tmp = ulist_alloc(GFP_NOFS);
1485         roots = ulist_alloc(GFP_NOFS);
1486         if (!tmp || !roots) {
1487                 ulist_free(tmp);
1488                 ulist_free(roots);
1489                 return -ENOMEM;
1490         }
1491
1492         trans = btrfs_join_transaction(root);
1493         if (IS_ERR(trans)) {
1494                 trans = NULL;
1495                 down_read(&fs_info->commit_root_sem);
1496         } else {
1497                 btrfs_get_tree_mod_seq(fs_info, &elem);
1498         }
1499
1500         ULIST_ITER_INIT(&uiter);
1501         while (1) {
1502                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1503                                         roots, NULL, &shared, false);
1504                 if (ret == BACKREF_FOUND_SHARED) {
1505                         /* this is the only condition under which we return 1 */
1506                         ret = 1;
1507                         break;
1508                 }
1509                 if (ret < 0 && ret != -ENOENT)
1510                         break;
1511                 ret = 0;
1512                 node = ulist_next(tmp, &uiter);
1513                 if (!node)
1514                         break;
1515                 bytenr = node->val;
1516                 shared.share_count = 0;
1517                 cond_resched();
1518         }
1519
1520         if (trans) {
1521                 btrfs_put_tree_mod_seq(fs_info, &elem);
1522                 btrfs_end_transaction(trans);
1523         } else {
1524                 up_read(&fs_info->commit_root_sem);
1525         }
1526         ulist_free(tmp);
1527         ulist_free(roots);
1528         return ret;
1529 }
1530
1531 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1532                           u64 start_off, struct btrfs_path *path,
1533                           struct btrfs_inode_extref **ret_extref,
1534                           u64 *found_off)
1535 {
1536         int ret, slot;
1537         struct btrfs_key key;
1538         struct btrfs_key found_key;
1539         struct btrfs_inode_extref *extref;
1540         const struct extent_buffer *leaf;
1541         unsigned long ptr;
1542
1543         key.objectid = inode_objectid;
1544         key.type = BTRFS_INODE_EXTREF_KEY;
1545         key.offset = start_off;
1546
1547         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1548         if (ret < 0)
1549                 return ret;
1550
1551         while (1) {
1552                 leaf = path->nodes[0];
1553                 slot = path->slots[0];
1554                 if (slot >= btrfs_header_nritems(leaf)) {
1555                         /*
1556                          * If the item at offset is not found,
1557                          * btrfs_search_slot will point us to the slot
1558                          * where it should be inserted. In our case
1559                          * that will be the slot directly before the
1560                          * next INODE_REF_KEY_V2 item. In the case
1561                          * that we're pointing to the last slot in a
1562                          * leaf, we must move one leaf over.
1563                          */
1564                         ret = btrfs_next_leaf(root, path);
1565                         if (ret) {
1566                                 if (ret >= 1)
1567                                         ret = -ENOENT;
1568                                 break;
1569                         }
1570                         continue;
1571                 }
1572
1573                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1574
1575                 /*
1576                  * Check that we're still looking at an extended ref key for
1577                  * this particular objectid. If we have different
1578                  * objectid or type then there are no more to be found
1579                  * in the tree and we can exit.
1580                  */
1581                 ret = -ENOENT;
1582                 if (found_key.objectid != inode_objectid)
1583                         break;
1584                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1585                         break;
1586
1587                 ret = 0;
1588                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1589                 extref = (struct btrfs_inode_extref *)ptr;
1590                 *ret_extref = extref;
1591                 if (found_off)
1592                         *found_off = found_key.offset;
1593                 break;
1594         }
1595
1596         return ret;
1597 }
1598
1599 /*
1600  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1601  * Elements of the path are separated by '/' and the path is guaranteed to be
1602  * 0-terminated. the path is only given within the current file system.
1603  * Therefore, it never starts with a '/'. the caller is responsible to provide
1604  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1605  * the start point of the resulting string is returned. this pointer is within
1606  * dest, normally.
1607  * in case the path buffer would overflow, the pointer is decremented further
1608  * as if output was written to the buffer, though no more output is actually
1609  * generated. that way, the caller can determine how much space would be
1610  * required for the path to fit into the buffer. in that case, the returned
1611  * value will be smaller than dest. callers must check this!
1612  */
1613 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1614                         u32 name_len, unsigned long name_off,
1615                         struct extent_buffer *eb_in, u64 parent,
1616                         char *dest, u32 size)
1617 {
1618         int slot;
1619         u64 next_inum;
1620         int ret;
1621         s64 bytes_left = ((s64)size) - 1;
1622         struct extent_buffer *eb = eb_in;
1623         struct btrfs_key found_key;
1624         int leave_spinning = path->leave_spinning;
1625         struct btrfs_inode_ref *iref;
1626
1627         if (bytes_left >= 0)
1628                 dest[bytes_left] = '\0';
1629
1630         path->leave_spinning = 1;
1631         while (1) {
1632                 bytes_left -= name_len;
1633                 if (bytes_left >= 0)
1634                         read_extent_buffer(eb, dest + bytes_left,
1635                                            name_off, name_len);
1636                 if (eb != eb_in) {
1637                         if (!path->skip_locking)
1638                                 btrfs_tree_read_unlock_blocking(eb);
1639                         free_extent_buffer(eb);
1640                 }
1641                 ret = btrfs_find_item(fs_root, path, parent, 0,
1642                                 BTRFS_INODE_REF_KEY, &found_key);
1643                 if (ret > 0)
1644                         ret = -ENOENT;
1645                 if (ret)
1646                         break;
1647
1648                 next_inum = found_key.offset;
1649
1650                 /* regular exit ahead */
1651                 if (parent == next_inum)
1652                         break;
1653
1654                 slot = path->slots[0];
1655                 eb = path->nodes[0];
1656                 /* make sure we can use eb after releasing the path */
1657                 if (eb != eb_in) {
1658                         if (!path->skip_locking)
1659                                 btrfs_set_lock_blocking_read(eb);
1660                         path->nodes[0] = NULL;
1661                         path->locks[0] = 0;
1662                 }
1663                 btrfs_release_path(path);
1664                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1665
1666                 name_len = btrfs_inode_ref_name_len(eb, iref);
1667                 name_off = (unsigned long)(iref + 1);
1668
1669                 parent = next_inum;
1670                 --bytes_left;
1671                 if (bytes_left >= 0)
1672                         dest[bytes_left] = '/';
1673         }
1674
1675         btrfs_release_path(path);
1676         path->leave_spinning = leave_spinning;
1677
1678         if (ret)
1679                 return ERR_PTR(ret);
1680
1681         return dest + bytes_left;
1682 }
1683
1684 /*
1685  * this makes the path point to (logical EXTENT_ITEM *)
1686  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1687  * tree blocks and <0 on error.
1688  */
1689 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1690                         struct btrfs_path *path, struct btrfs_key *found_key,
1691                         u64 *flags_ret)
1692 {
1693         int ret;
1694         u64 flags;
1695         u64 size = 0;
1696         u32 item_size;
1697         const struct extent_buffer *eb;
1698         struct btrfs_extent_item *ei;
1699         struct btrfs_key key;
1700
1701         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1702                 key.type = BTRFS_METADATA_ITEM_KEY;
1703         else
1704                 key.type = BTRFS_EXTENT_ITEM_KEY;
1705         key.objectid = logical;
1706         key.offset = (u64)-1;
1707
1708         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1709         if (ret < 0)
1710                 return ret;
1711
1712         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1713         if (ret) {
1714                 if (ret > 0)
1715                         ret = -ENOENT;
1716                 return ret;
1717         }
1718         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1719         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1720                 size = fs_info->nodesize;
1721         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1722                 size = found_key->offset;
1723
1724         if (found_key->objectid > logical ||
1725             found_key->objectid + size <= logical) {
1726                 btrfs_debug(fs_info,
1727                         "logical %llu is not within any extent", logical);
1728                 return -ENOENT;
1729         }
1730
1731         eb = path->nodes[0];
1732         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1733         BUG_ON(item_size < sizeof(*ei));
1734
1735         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1736         flags = btrfs_extent_flags(eb, ei);
1737
1738         btrfs_debug(fs_info,
1739                 "logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
1740                  logical, logical - found_key->objectid, found_key->objectid,
1741                  found_key->offset, flags, item_size);
1742
1743         WARN_ON(!flags_ret);
1744         if (flags_ret) {
1745                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1746                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1747                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1748                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1749                 else
1750                         BUG_ON(1);
1751                 return 0;
1752         }
1753
1754         return -EIO;
1755 }
1756
1757 /*
1758  * helper function to iterate extent inline refs. ptr must point to a 0 value
1759  * for the first call and may be modified. it is used to track state.
1760  * if more refs exist, 0 is returned and the next call to
1761  * get_extent_inline_ref must pass the modified ptr parameter to get the
1762  * next ref. after the last ref was processed, 1 is returned.
1763  * returns <0 on error
1764  */
1765 static int get_extent_inline_ref(unsigned long *ptr,
1766                                  const struct extent_buffer *eb,
1767                                  const struct btrfs_key *key,
1768                                  const struct btrfs_extent_item *ei,
1769                                  u32 item_size,
1770                                  struct btrfs_extent_inline_ref **out_eiref,
1771                                  int *out_type)
1772 {
1773         unsigned long end;
1774         u64 flags;
1775         struct btrfs_tree_block_info *info;
1776
1777         if (!*ptr) {
1778                 /* first call */
1779                 flags = btrfs_extent_flags(eb, ei);
1780                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1781                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1782                                 /* a skinny metadata extent */
1783                                 *out_eiref =
1784                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1785                         } else {
1786                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1787                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1788                                 *out_eiref =
1789                                    (struct btrfs_extent_inline_ref *)(info + 1);
1790                         }
1791                 } else {
1792                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1793                 }
1794                 *ptr = (unsigned long)*out_eiref;
1795                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1796                         return -ENOENT;
1797         }
1798
1799         end = (unsigned long)ei + item_size;
1800         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1801         *out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
1802                                                      BTRFS_REF_TYPE_ANY);
1803         if (*out_type == BTRFS_REF_TYPE_INVALID)
1804                 return -EUCLEAN;
1805
1806         *ptr += btrfs_extent_inline_ref_size(*out_type);
1807         WARN_ON(*ptr > end);
1808         if (*ptr == end)
1809                 return 1; /* last */
1810
1811         return 0;
1812 }
1813
1814 /*
1815  * reads the tree block backref for an extent. tree level and root are returned
1816  * through out_level and out_root. ptr must point to a 0 value for the first
1817  * call and may be modified (see get_extent_inline_ref comment).
1818  * returns 0 if data was provided, 1 if there was no more data to provide or
1819  * <0 on error.
1820  */
1821 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1822                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1823                             u32 item_size, u64 *out_root, u8 *out_level)
1824 {
1825         int ret;
1826         int type;
1827         struct btrfs_extent_inline_ref *eiref;
1828
1829         if (*ptr == (unsigned long)-1)
1830                 return 1;
1831
1832         while (1) {
1833                 ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
1834                                               &eiref, &type);
1835                 if (ret < 0)
1836                         return ret;
1837
1838                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1839                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1840                         break;
1841
1842                 if (ret == 1)
1843                         return 1;
1844         }
1845
1846         /* we can treat both ref types equally here */
1847         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1848
1849         if (key->type == BTRFS_EXTENT_ITEM_KEY) {
1850                 struct btrfs_tree_block_info *info;
1851
1852                 info = (struct btrfs_tree_block_info *)(ei + 1);
1853                 *out_level = btrfs_tree_block_level(eb, info);
1854         } else {
1855                 ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
1856                 *out_level = (u8)key->offset;
1857         }
1858
1859         if (ret == 1)
1860                 *ptr = (unsigned long)-1;
1861
1862         return 0;
1863 }
1864
1865 static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
1866                              struct extent_inode_elem *inode_list,
1867                              u64 root, u64 extent_item_objectid,
1868                              iterate_extent_inodes_t *iterate, void *ctx)
1869 {
1870         struct extent_inode_elem *eie;
1871         int ret = 0;
1872
1873         for (eie = inode_list; eie; eie = eie->next) {
1874                 btrfs_debug(fs_info,
1875                             "ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
1876                             extent_item_objectid, eie->inum,
1877                             eie->offset, root);
1878                 ret = iterate(eie->inum, eie->offset, root, ctx);
1879                 if (ret) {
1880                         btrfs_debug(fs_info,
1881                                     "stopping iteration for %llu due to ret=%d",
1882                                     extent_item_objectid, ret);
1883                         break;
1884                 }
1885         }
1886
1887         return ret;
1888 }
1889
1890 /*
1891  * calls iterate() for every inode that references the extent identified by
1892  * the given parameters.
1893  * when the iterator function returns a non-zero value, iteration stops.
1894  */
1895 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1896                                 u64 extent_item_objectid, u64 extent_item_pos,
1897                                 int search_commit_root,
1898                                 iterate_extent_inodes_t *iterate, void *ctx,
1899                                 bool ignore_offset)
1900 {
1901         int ret;
1902         struct btrfs_trans_handle *trans = NULL;
1903         struct ulist *refs = NULL;
1904         struct ulist *roots = NULL;
1905         struct ulist_node *ref_node = NULL;
1906         struct ulist_node *root_node = NULL;
1907         struct seq_list tree_mod_seq_elem = SEQ_LIST_INIT(tree_mod_seq_elem);
1908         struct ulist_iterator ref_uiter;
1909         struct ulist_iterator root_uiter;
1910
1911         btrfs_debug(fs_info, "resolving all inodes for extent %llu",
1912                         extent_item_objectid);
1913
1914         if (!search_commit_root) {
1915                 trans = btrfs_join_transaction(fs_info->extent_root);
1916                 if (IS_ERR(trans))
1917                         return PTR_ERR(trans);
1918                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1919         } else {
1920                 down_read(&fs_info->commit_root_sem);
1921         }
1922
1923         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1924                                    tree_mod_seq_elem.seq, &refs,
1925                                    &extent_item_pos, ignore_offset);
1926         if (ret)
1927                 goto out;
1928
1929         ULIST_ITER_INIT(&ref_uiter);
1930         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1931                 ret = btrfs_find_all_roots_safe(trans, fs_info, ref_node->val,
1932                                                 tree_mod_seq_elem.seq, &roots,
1933                                                 ignore_offset);
1934                 if (ret)
1935                         break;
1936                 ULIST_ITER_INIT(&root_uiter);
1937                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1938                         btrfs_debug(fs_info,
1939                                     "root %llu references leaf %llu, data list %#llx",
1940                                     root_node->val, ref_node->val,
1941                                     ref_node->aux);
1942                         ret = iterate_leaf_refs(fs_info,
1943                                                 (struct extent_inode_elem *)
1944                                                 (uintptr_t)ref_node->aux,
1945                                                 root_node->val,
1946                                                 extent_item_objectid,
1947                                                 iterate, ctx);
1948                 }
1949                 ulist_free(roots);
1950         }
1951
1952         free_leaf_list(refs);
1953 out:
1954         if (!search_commit_root) {
1955                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1956                 btrfs_end_transaction(trans);
1957         } else {
1958                 up_read(&fs_info->commit_root_sem);
1959         }
1960
1961         return ret;
1962 }
1963
1964 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1965                                 struct btrfs_path *path,
1966                                 iterate_extent_inodes_t *iterate, void *ctx,
1967                                 bool ignore_offset)
1968 {
1969         int ret;
1970         u64 extent_item_pos;
1971         u64 flags = 0;
1972         struct btrfs_key found_key;
1973         int search_commit_root = path->search_commit_root;
1974
1975         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1976         btrfs_release_path(path);
1977         if (ret < 0)
1978                 return ret;
1979         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1980                 return -EINVAL;
1981
1982         extent_item_pos = logical - found_key.objectid;
1983         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1984                                         extent_item_pos, search_commit_root,
1985                                         iterate, ctx, ignore_offset);
1986
1987         return ret;
1988 }
1989
1990 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1991                               struct extent_buffer *eb, void *ctx);
1992
1993 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1994                               struct btrfs_path *path,
1995                               iterate_irefs_t *iterate, void *ctx)
1996 {
1997         int ret = 0;
1998         int slot;
1999         u32 cur;
2000         u32 len;
2001         u32 name_len;
2002         u64 parent = 0;
2003         int found = 0;
2004         struct extent_buffer *eb;
2005         struct btrfs_item *item;
2006         struct btrfs_inode_ref *iref;
2007         struct btrfs_key found_key;
2008
2009         while (!ret) {
2010                 ret = btrfs_find_item(fs_root, path, inum,
2011                                 parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
2012                                 &found_key);
2013
2014                 if (ret < 0)
2015                         break;
2016                 if (ret) {
2017                         ret = found ? 0 : -ENOENT;
2018                         break;
2019                 }
2020                 ++found;
2021
2022                 parent = found_key.offset;
2023                 slot = path->slots[0];
2024                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2025                 if (!eb) {
2026                         ret = -ENOMEM;
2027                         break;
2028                 }
2029                 btrfs_release_path(path);
2030
2031                 item = btrfs_item_nr(slot);
2032                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2033
2034                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
2035                         name_len = btrfs_inode_ref_name_len(eb, iref);
2036                         /* path must be released before calling iterate()! */
2037                         btrfs_debug(fs_root->fs_info,
2038                                 "following ref at offset %u for inode %llu in tree %llu",
2039                                 cur, found_key.objectid,
2040                                 fs_root->root_key.objectid);
2041                         ret = iterate(parent, name_len,
2042                                       (unsigned long)(iref + 1), eb, ctx);
2043                         if (ret)
2044                                 break;
2045                         len = sizeof(*iref) + name_len;
2046                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
2047                 }
2048                 free_extent_buffer(eb);
2049         }
2050
2051         btrfs_release_path(path);
2052
2053         return ret;
2054 }
2055
2056 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
2057                                  struct btrfs_path *path,
2058                                  iterate_irefs_t *iterate, void *ctx)
2059 {
2060         int ret;
2061         int slot;
2062         u64 offset = 0;
2063         u64 parent;
2064         int found = 0;
2065         struct extent_buffer *eb;
2066         struct btrfs_inode_extref *extref;
2067         u32 item_size;
2068         u32 cur_offset;
2069         unsigned long ptr;
2070
2071         while (1) {
2072                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
2073                                             &offset);
2074                 if (ret < 0)
2075                         break;
2076                 if (ret) {
2077                         ret = found ? 0 : -ENOENT;
2078                         break;
2079                 }
2080                 ++found;
2081
2082                 slot = path->slots[0];
2083                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2084                 if (!eb) {
2085                         ret = -ENOMEM;
2086                         break;
2087                 }
2088                 btrfs_release_path(path);
2089
2090                 item_size = btrfs_item_size_nr(eb, slot);
2091                 ptr = btrfs_item_ptr_offset(eb, slot);
2092                 cur_offset = 0;
2093
2094                 while (cur_offset < item_size) {
2095                         u32 name_len;
2096
2097                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
2098                         parent = btrfs_inode_extref_parent(eb, extref);
2099                         name_len = btrfs_inode_extref_name_len(eb, extref);
2100                         ret = iterate(parent, name_len,
2101                                       (unsigned long)&extref->name, eb, ctx);
2102                         if (ret)
2103                                 break;
2104
2105                         cur_offset += btrfs_inode_extref_name_len(eb, extref);
2106                         cur_offset += sizeof(*extref);
2107                 }
2108                 free_extent_buffer(eb);
2109
2110                 offset++;
2111         }
2112
2113         btrfs_release_path(path);
2114
2115         return ret;
2116 }
2117
2118 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
2119                          struct btrfs_path *path, iterate_irefs_t *iterate,
2120                          void *ctx)
2121 {
2122         int ret;
2123         int found_refs = 0;
2124
2125         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
2126         if (!ret)
2127                 ++found_refs;
2128         else if (ret != -ENOENT)
2129                 return ret;
2130
2131         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
2132         if (ret == -ENOENT && found_refs)
2133                 return 0;
2134
2135         return ret;
2136 }
2137
2138 /*
2139  * returns 0 if the path could be dumped (probably truncated)
2140  * returns <0 in case of an error
2141  */
2142 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2143                          struct extent_buffer *eb, void *ctx)
2144 {
2145         struct inode_fs_paths *ipath = ctx;
2146         char *fspath;
2147         char *fspath_min;
2148         int i = ipath->fspath->elem_cnt;
2149         const int s_ptr = sizeof(char *);
2150         u32 bytes_left;
2151
2152         bytes_left = ipath->fspath->bytes_left > s_ptr ?
2153                                         ipath->fspath->bytes_left - s_ptr : 0;
2154
2155         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
2156         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
2157                                    name_off, eb, inum, fspath_min, bytes_left);
2158         if (IS_ERR(fspath))
2159                 return PTR_ERR(fspath);
2160
2161         if (fspath > fspath_min) {
2162                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
2163                 ++ipath->fspath->elem_cnt;
2164                 ipath->fspath->bytes_left = fspath - fspath_min;
2165         } else {
2166                 ++ipath->fspath->elem_missed;
2167                 ipath->fspath->bytes_missing += fspath_min - fspath;
2168                 ipath->fspath->bytes_left = 0;
2169         }
2170
2171         return 0;
2172 }
2173
2174 /*
2175  * this dumps all file system paths to the inode into the ipath struct, provided
2176  * is has been created large enough. each path is zero-terminated and accessed
2177  * from ipath->fspath->val[i].
2178  * when it returns, there are ipath->fspath->elem_cnt number of paths available
2179  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
2180  * number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
2181  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
2182  * have been needed to return all paths.
2183  */
2184 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
2185 {
2186         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
2187                              inode_to_path, ipath);
2188 }
2189
2190 struct btrfs_data_container *init_data_container(u32 total_bytes)
2191 {
2192         struct btrfs_data_container *data;
2193         size_t alloc_bytes;
2194
2195         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
2196         data = kvmalloc(alloc_bytes, GFP_KERNEL);
2197         if (!data)
2198                 return ERR_PTR(-ENOMEM);
2199
2200         if (total_bytes >= sizeof(*data)) {
2201                 data->bytes_left = total_bytes - sizeof(*data);
2202                 data->bytes_missing = 0;
2203         } else {
2204                 data->bytes_missing = sizeof(*data) - total_bytes;
2205                 data->bytes_left = 0;
2206         }
2207
2208         data->elem_cnt = 0;
2209         data->elem_missed = 0;
2210
2211         return data;
2212 }
2213
2214 /*
2215  * allocates space to return multiple file system paths for an inode.
2216  * total_bytes to allocate are passed, note that space usable for actual path
2217  * information will be total_bytes - sizeof(struct inode_fs_paths).
2218  * the returned pointer must be freed with free_ipath() in the end.
2219  */
2220 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
2221                                         struct btrfs_path *path)
2222 {
2223         struct inode_fs_paths *ifp;
2224         struct btrfs_data_container *fspath;
2225
2226         fspath = init_data_container(total_bytes);
2227         if (IS_ERR(fspath))
2228                 return ERR_CAST(fspath);
2229
2230         ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
2231         if (!ifp) {
2232                 kvfree(fspath);
2233                 return ERR_PTR(-ENOMEM);
2234         }
2235
2236         ifp->btrfs_path = path;
2237         ifp->fspath = fspath;
2238         ifp->fs_root = fs_root;
2239
2240         return ifp;
2241 }
2242
2243 void free_ipath(struct inode_fs_paths *ipath)
2244 {
2245         if (!ipath)
2246                 return;
2247         kvfree(ipath->fspath);
2248         kfree(ipath);
2249 }