f94b2d8c744a1bfee2dee175ee8f8453aa1e0e8f
[sfrench/cifs-2.6.git] / fs / btrfs / backref.c
1 /*
2  * Copyright (C) 2011 STRATO.  All rights reserved.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public
6  * License v2 as published by the Free Software Foundation.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
11  * General Public License for more details.
12  *
13  * You should have received a copy of the GNU General Public
14  * License along with this program; if not, write to the
15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16  * Boston, MA 021110-1307, USA.
17  */
18
19 #include <linux/mm.h>
20 #include <linux/rbtree.h>
21 #include <trace/events/btrfs.h>
22 #include "ctree.h"
23 #include "disk-io.h"
24 #include "backref.h"
25 #include "ulist.h"
26 #include "transaction.h"
27 #include "delayed-ref.h"
28 #include "locking.h"
29
30 /* Just an arbitrary number so we can be sure this happened */
31 #define BACKREF_FOUND_SHARED 6
32
33 struct extent_inode_elem {
34         u64 inum;
35         u64 offset;
36         struct extent_inode_elem *next;
37 };
38
39 static int check_extent_in_eb(const struct btrfs_key *key,
40                               const struct extent_buffer *eb,
41                               const struct btrfs_file_extent_item *fi,
42                               u64 extent_item_pos,
43                               struct extent_inode_elem **eie,
44                               bool ignore_offset)
45 {
46         u64 offset = 0;
47         struct extent_inode_elem *e;
48
49         if (!ignore_offset &&
50             !btrfs_file_extent_compression(eb, fi) &&
51             !btrfs_file_extent_encryption(eb, fi) &&
52             !btrfs_file_extent_other_encoding(eb, fi)) {
53                 u64 data_offset;
54                 u64 data_len;
55
56                 data_offset = btrfs_file_extent_offset(eb, fi);
57                 data_len = btrfs_file_extent_num_bytes(eb, fi);
58
59                 if (extent_item_pos < data_offset ||
60                     extent_item_pos >= data_offset + data_len)
61                         return 1;
62                 offset = extent_item_pos - data_offset;
63         }
64
65         e = kmalloc(sizeof(*e), GFP_NOFS);
66         if (!e)
67                 return -ENOMEM;
68
69         e->next = *eie;
70         e->inum = key->objectid;
71         e->offset = key->offset + offset;
72         *eie = e;
73
74         return 0;
75 }
76
77 static void free_inode_elem_list(struct extent_inode_elem *eie)
78 {
79         struct extent_inode_elem *eie_next;
80
81         for (; eie; eie = eie_next) {
82                 eie_next = eie->next;
83                 kfree(eie);
84         }
85 }
86
87 static int find_extent_in_eb(const struct extent_buffer *eb,
88                              u64 wanted_disk_byte, u64 extent_item_pos,
89                              struct extent_inode_elem **eie,
90                              bool ignore_offset)
91 {
92         u64 disk_byte;
93         struct btrfs_key key;
94         struct btrfs_file_extent_item *fi;
95         int slot;
96         int nritems;
97         int extent_type;
98         int ret;
99
100         /*
101          * from the shared data ref, we only have the leaf but we need
102          * the key. thus, we must look into all items and see that we
103          * find one (some) with a reference to our extent item.
104          */
105         nritems = btrfs_header_nritems(eb);
106         for (slot = 0; slot < nritems; ++slot) {
107                 btrfs_item_key_to_cpu(eb, &key, slot);
108                 if (key.type != BTRFS_EXTENT_DATA_KEY)
109                         continue;
110                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
111                 extent_type = btrfs_file_extent_type(eb, fi);
112                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
113                         continue;
114                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
115                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
116                 if (disk_byte != wanted_disk_byte)
117                         continue;
118
119                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie, ignore_offset);
120                 if (ret < 0)
121                         return ret;
122         }
123
124         return 0;
125 }
126
127 struct preftree {
128         struct rb_root root;
129         unsigned int count;
130 };
131
132 #define PREFTREE_INIT   { .root = RB_ROOT, .count = 0 }
133
134 struct preftrees {
135         struct preftree direct;    /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
136         struct preftree indirect;  /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
137         struct preftree indirect_missing_keys;
138 };
139
140 /*
141  * Checks for a shared extent during backref search.
142  *
143  * The share_count tracks prelim_refs (direct and indirect) having a
144  * ref->count >0:
145  *  - incremented when a ref->count transitions to >0
146  *  - decremented when a ref->count transitions to <1
147  */
148 struct share_check {
149         u64 root_objectid;
150         u64 inum;
151         int share_count;
152 };
153
154 static inline int extent_is_shared(struct share_check *sc)
155 {
156         return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
157 }
158
159 static struct kmem_cache *btrfs_prelim_ref_cache;
160
161 int __init btrfs_prelim_ref_init(void)
162 {
163         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
164                                         sizeof(struct prelim_ref),
165                                         0,
166                                         SLAB_MEM_SPREAD,
167                                         NULL);
168         if (!btrfs_prelim_ref_cache)
169                 return -ENOMEM;
170         return 0;
171 }
172
173 void btrfs_prelim_ref_exit(void)
174 {
175         kmem_cache_destroy(btrfs_prelim_ref_cache);
176 }
177
178 static void free_pref(struct prelim_ref *ref)
179 {
180         kmem_cache_free(btrfs_prelim_ref_cache, ref);
181 }
182
183 /*
184  * Return 0 when both refs are for the same block (and can be merged).
185  * A -1 return indicates ref1 is a 'lower' block than ref2, while 1
186  * indicates a 'higher' block.
187  */
188 static int prelim_ref_compare(struct prelim_ref *ref1,
189                               struct prelim_ref *ref2)
190 {
191         if (ref1->level < ref2->level)
192                 return -1;
193         if (ref1->level > ref2->level)
194                 return 1;
195         if (ref1->root_id < ref2->root_id)
196                 return -1;
197         if (ref1->root_id > ref2->root_id)
198                 return 1;
199         if (ref1->key_for_search.type < ref2->key_for_search.type)
200                 return -1;
201         if (ref1->key_for_search.type > ref2->key_for_search.type)
202                 return 1;
203         if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
204                 return -1;
205         if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
206                 return 1;
207         if (ref1->key_for_search.offset < ref2->key_for_search.offset)
208                 return -1;
209         if (ref1->key_for_search.offset > ref2->key_for_search.offset)
210                 return 1;
211         if (ref1->parent < ref2->parent)
212                 return -1;
213         if (ref1->parent > ref2->parent)
214                 return 1;
215
216         return 0;
217 }
218
219 static void update_share_count(struct share_check *sc, int oldcount,
220                                int newcount)
221 {
222         if ((!sc) || (oldcount == 0 && newcount < 1))
223                 return;
224
225         if (oldcount > 0 && newcount < 1)
226                 sc->share_count--;
227         else if (oldcount < 1 && newcount > 0)
228                 sc->share_count++;
229 }
230
231 /*
232  * Add @newref to the @root rbtree, merging identical refs.
233  *
234  * Callers should assume that newref has been freed after calling.
235  */
236 static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
237                               struct preftree *preftree,
238                               struct prelim_ref *newref,
239                               struct share_check *sc)
240 {
241         struct rb_root *root;
242         struct rb_node **p;
243         struct rb_node *parent = NULL;
244         struct prelim_ref *ref;
245         int result;
246
247         root = &preftree->root;
248         p = &root->rb_node;
249
250         while (*p) {
251                 parent = *p;
252                 ref = rb_entry(parent, struct prelim_ref, rbnode);
253                 result = prelim_ref_compare(ref, newref);
254                 if (result < 0) {
255                         p = &(*p)->rb_left;
256                 } else if (result > 0) {
257                         p = &(*p)->rb_right;
258                 } else {
259                         /* Identical refs, merge them and free @newref */
260                         struct extent_inode_elem *eie = ref->inode_list;
261
262                         while (eie && eie->next)
263                                 eie = eie->next;
264
265                         if (!eie)
266                                 ref->inode_list = newref->inode_list;
267                         else
268                                 eie->next = newref->inode_list;
269                         trace_btrfs_prelim_ref_merge(fs_info, ref, newref,
270                                                      preftree->count);
271                         /*
272                          * A delayed ref can have newref->count < 0.
273                          * The ref->count is updated to follow any
274                          * BTRFS_[ADD|DROP]_DELAYED_REF actions.
275                          */
276                         update_share_count(sc, ref->count,
277                                            ref->count + newref->count);
278                         ref->count += newref->count;
279                         free_pref(newref);
280                         return;
281                 }
282         }
283
284         update_share_count(sc, 0, newref->count);
285         preftree->count++;
286         trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
287         rb_link_node(&newref->rbnode, parent, p);
288         rb_insert_color(&newref->rbnode, root);
289 }
290
291 /*
292  * Release the entire tree.  We don't care about internal consistency so
293  * just free everything and then reset the tree root.
294  */
295 static void prelim_release(struct preftree *preftree)
296 {
297         struct prelim_ref *ref, *next_ref;
298
299         rbtree_postorder_for_each_entry_safe(ref, next_ref, &preftree->root,
300                                              rbnode)
301                 free_pref(ref);
302
303         preftree->root = RB_ROOT;
304         preftree->count = 0;
305 }
306
307 /*
308  * the rules for all callers of this function are:
309  * - obtaining the parent is the goal
310  * - if you add a key, you must know that it is a correct key
311  * - if you cannot add the parent or a correct key, then we will look into the
312  *   block later to set a correct key
313  *
314  * delayed refs
315  * ============
316  *        backref type | shared | indirect | shared | indirect
317  * information         |   tree |     tree |   data |     data
318  * --------------------+--------+----------+--------+----------
319  *      parent logical |    y   |     -    |    -   |     -
320  *      key to resolve |    -   |     y    |    y   |     y
321  *  tree block logical |    -   |     -    |    -   |     -
322  *  root for resolving |    y   |     y    |    y   |     y
323  *
324  * - column 1:       we've the parent -> done
325  * - column 2, 3, 4: we use the key to find the parent
326  *
327  * on disk refs (inline or keyed)
328  * ==============================
329  *        backref type | shared | indirect | shared | indirect
330  * information         |   tree |     tree |   data |     data
331  * --------------------+--------+----------+--------+----------
332  *      parent logical |    y   |     -    |    y   |     -
333  *      key to resolve |    -   |     -    |    -   |     y
334  *  tree block logical |    y   |     y    |    y   |     y
335  *  root for resolving |    -   |     y    |    y   |     y
336  *
337  * - column 1, 3: we've the parent -> done
338  * - column 2:    we take the first key from the block to find the parent
339  *                (see add_missing_keys)
340  * - column 4:    we use the key to find the parent
341  *
342  * additional information that's available but not required to find the parent
343  * block might help in merging entries to gain some speed.
344  */
345 static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
346                           struct preftree *preftree, u64 root_id,
347                           const struct btrfs_key *key, int level, u64 parent,
348                           u64 wanted_disk_byte, int count,
349                           struct share_check *sc, gfp_t gfp_mask)
350 {
351         struct prelim_ref *ref;
352
353         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
354                 return 0;
355
356         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
357         if (!ref)
358                 return -ENOMEM;
359
360         ref->root_id = root_id;
361         if (key) {
362                 ref->key_for_search = *key;
363                 /*
364                  * We can often find data backrefs with an offset that is too
365                  * large (>= LLONG_MAX, maximum allowed file offset) due to
366                  * underflows when subtracting a file's offset with the data
367                  * offset of its corresponding extent data item. This can
368                  * happen for example in the clone ioctl.
369                  * So if we detect such case we set the search key's offset to
370                  * zero to make sure we will find the matching file extent item
371                  * at add_all_parents(), otherwise we will miss it because the
372                  * offset taken form the backref is much larger then the offset
373                  * of the file extent item. This can make us scan a very large
374                  * number of file extent items, but at least it will not make
375                  * us miss any.
376                  * This is an ugly workaround for a behaviour that should have
377                  * never existed, but it does and a fix for the clone ioctl
378                  * would touch a lot of places, cause backwards incompatibility
379                  * and would not fix the problem for extents cloned with older
380                  * kernels.
381                  */
382                 if (ref->key_for_search.type == BTRFS_EXTENT_DATA_KEY &&
383                     ref->key_for_search.offset >= LLONG_MAX)
384                         ref->key_for_search.offset = 0;
385         } else {
386                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
387         }
388
389         ref->inode_list = NULL;
390         ref->level = level;
391         ref->count = count;
392         ref->parent = parent;
393         ref->wanted_disk_byte = wanted_disk_byte;
394         prelim_ref_insert(fs_info, preftree, ref, sc);
395         return extent_is_shared(sc);
396 }
397
398 /* direct refs use root == 0, key == NULL */
399 static int add_direct_ref(const struct btrfs_fs_info *fs_info,
400                           struct preftrees *preftrees, int level, u64 parent,
401                           u64 wanted_disk_byte, int count,
402                           struct share_check *sc, gfp_t gfp_mask)
403 {
404         return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level,
405                               parent, wanted_disk_byte, count, sc, gfp_mask);
406 }
407
408 /* indirect refs use parent == 0 */
409 static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
410                             struct preftrees *preftrees, u64 root_id,
411                             const struct btrfs_key *key, int level,
412                             u64 wanted_disk_byte, int count,
413                             struct share_check *sc, gfp_t gfp_mask)
414 {
415         struct preftree *tree = &preftrees->indirect;
416
417         if (!key)
418                 tree = &preftrees->indirect_missing_keys;
419         return add_prelim_ref(fs_info, tree, root_id, key, level, 0,
420                               wanted_disk_byte, count, sc, gfp_mask);
421 }
422
423 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
424                            struct ulist *parents, struct prelim_ref *ref,
425                            int level, u64 time_seq, const u64 *extent_item_pos,
426                            u64 total_refs, bool ignore_offset)
427 {
428         int ret = 0;
429         int slot;
430         struct extent_buffer *eb;
431         struct btrfs_key key;
432         struct btrfs_key *key_for_search = &ref->key_for_search;
433         struct btrfs_file_extent_item *fi;
434         struct extent_inode_elem *eie = NULL, *old = NULL;
435         u64 disk_byte;
436         u64 wanted_disk_byte = ref->wanted_disk_byte;
437         u64 count = 0;
438
439         if (level != 0) {
440                 eb = path->nodes[level];
441                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
442                 if (ret < 0)
443                         return ret;
444                 return 0;
445         }
446
447         /*
448          * We normally enter this function with the path already pointing to
449          * the first item to check. But sometimes, we may enter it with
450          * slot==nritems. In that case, go to the next leaf before we continue.
451          */
452         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
453                 if (time_seq == SEQ_LAST)
454                         ret = btrfs_next_leaf(root, path);
455                 else
456                         ret = btrfs_next_old_leaf(root, path, time_seq);
457         }
458
459         while (!ret && count < total_refs) {
460                 eb = path->nodes[0];
461                 slot = path->slots[0];
462
463                 btrfs_item_key_to_cpu(eb, &key, slot);
464
465                 if (key.objectid != key_for_search->objectid ||
466                     key.type != BTRFS_EXTENT_DATA_KEY)
467                         break;
468
469                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
470                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
471
472                 if (disk_byte == wanted_disk_byte) {
473                         eie = NULL;
474                         old = NULL;
475                         count++;
476                         if (extent_item_pos) {
477                                 ret = check_extent_in_eb(&key, eb, fi,
478                                                 *extent_item_pos,
479                                                 &eie, ignore_offset);
480                                 if (ret < 0)
481                                         break;
482                         }
483                         if (ret > 0)
484                                 goto next;
485                         ret = ulist_add_merge_ptr(parents, eb->start,
486                                                   eie, (void **)&old, GFP_NOFS);
487                         if (ret < 0)
488                                 break;
489                         if (!ret && extent_item_pos) {
490                                 while (old->next)
491                                         old = old->next;
492                                 old->next = eie;
493                         }
494                         eie = NULL;
495                 }
496 next:
497                 if (time_seq == SEQ_LAST)
498                         ret = btrfs_next_item(root, path);
499                 else
500                         ret = btrfs_next_old_item(root, path, time_seq);
501         }
502
503         if (ret > 0)
504                 ret = 0;
505         else if (ret < 0)
506                 free_inode_elem_list(eie);
507         return ret;
508 }
509
510 /*
511  * resolve an indirect backref in the form (root_id, key, level)
512  * to a logical address
513  */
514 static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
515                                 struct btrfs_path *path, u64 time_seq,
516                                 struct prelim_ref *ref, struct ulist *parents,
517                                 const u64 *extent_item_pos, u64 total_refs,
518                                 bool ignore_offset)
519 {
520         struct btrfs_root *root;
521         struct btrfs_key root_key;
522         struct extent_buffer *eb;
523         int ret = 0;
524         int root_level;
525         int level = ref->level;
526         int index;
527
528         root_key.objectid = ref->root_id;
529         root_key.type = BTRFS_ROOT_ITEM_KEY;
530         root_key.offset = (u64)-1;
531
532         index = srcu_read_lock(&fs_info->subvol_srcu);
533
534         root = btrfs_get_fs_root(fs_info, &root_key, false);
535         if (IS_ERR(root)) {
536                 srcu_read_unlock(&fs_info->subvol_srcu, index);
537                 ret = PTR_ERR(root);
538                 goto out;
539         }
540
541         if (btrfs_is_testing(fs_info)) {
542                 srcu_read_unlock(&fs_info->subvol_srcu, index);
543                 ret = -ENOENT;
544                 goto out;
545         }
546
547         if (path->search_commit_root)
548                 root_level = btrfs_header_level(root->commit_root);
549         else if (time_seq == SEQ_LAST)
550                 root_level = btrfs_header_level(root->node);
551         else
552                 root_level = btrfs_old_root_level(root, time_seq);
553
554         if (root_level + 1 == level) {
555                 srcu_read_unlock(&fs_info->subvol_srcu, index);
556                 goto out;
557         }
558
559         path->lowest_level = level;
560         if (time_seq == SEQ_LAST)
561                 ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
562                                         0, 0);
563         else
564                 ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
565                                             time_seq);
566
567         /* root node has been locked, we can release @subvol_srcu safely here */
568         srcu_read_unlock(&fs_info->subvol_srcu, index);
569
570         btrfs_debug(fs_info,
571                 "search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
572                  ref->root_id, level, ref->count, ret,
573                  ref->key_for_search.objectid, ref->key_for_search.type,
574                  ref->key_for_search.offset);
575         if (ret < 0)
576                 goto out;
577
578         eb = path->nodes[level];
579         while (!eb) {
580                 if (WARN_ON(!level)) {
581                         ret = 1;
582                         goto out;
583                 }
584                 level--;
585                 eb = path->nodes[level];
586         }
587
588         ret = add_all_parents(root, path, parents, ref, level, time_seq,
589                               extent_item_pos, total_refs, ignore_offset);
590 out:
591         path->lowest_level = 0;
592         btrfs_release_path(path);
593         return ret;
594 }
595
596 static struct extent_inode_elem *
597 unode_aux_to_inode_list(struct ulist_node *node)
598 {
599         if (!node)
600                 return NULL;
601         return (struct extent_inode_elem *)(uintptr_t)node->aux;
602 }
603
604 /*
605  * We maintain three seperate rbtrees: one for direct refs, one for
606  * indirect refs which have a key, and one for indirect refs which do not
607  * have a key. Each tree does merge on insertion.
608  *
609  * Once all of the references are located, we iterate over the tree of
610  * indirect refs with missing keys. An appropriate key is located and
611  * the ref is moved onto the tree for indirect refs. After all missing
612  * keys are thus located, we iterate over the indirect ref tree, resolve
613  * each reference, and then insert the resolved reference onto the
614  * direct tree (merging there too).
615  *
616  * New backrefs (i.e., for parent nodes) are added to the appropriate
617  * rbtree as they are encountered. The new backrefs are subsequently
618  * resolved as above.
619  */
620 static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
621                                  struct btrfs_path *path, u64 time_seq,
622                                  struct preftrees *preftrees,
623                                  const u64 *extent_item_pos, u64 total_refs,
624                                  struct share_check *sc, bool ignore_offset)
625 {
626         int err;
627         int ret = 0;
628         struct ulist *parents;
629         struct ulist_node *node;
630         struct ulist_iterator uiter;
631         struct rb_node *rnode;
632
633         parents = ulist_alloc(GFP_NOFS);
634         if (!parents)
635                 return -ENOMEM;
636
637         /*
638          * We could trade memory usage for performance here by iterating
639          * the tree, allocating new refs for each insertion, and then
640          * freeing the entire indirect tree when we're done.  In some test
641          * cases, the tree can grow quite large (~200k objects).
642          */
643         while ((rnode = rb_first(&preftrees->indirect.root))) {
644                 struct prelim_ref *ref;
645
646                 ref = rb_entry(rnode, struct prelim_ref, rbnode);
647                 if (WARN(ref->parent,
648                          "BUG: direct ref found in indirect tree")) {
649                         ret = -EINVAL;
650                         goto out;
651                 }
652
653                 rb_erase(&ref->rbnode, &preftrees->indirect.root);
654                 preftrees->indirect.count--;
655
656                 if (ref->count == 0) {
657                         free_pref(ref);
658                         continue;
659                 }
660
661                 if (sc && sc->root_objectid &&
662                     ref->root_id != sc->root_objectid) {
663                         free_pref(ref);
664                         ret = BACKREF_FOUND_SHARED;
665                         goto out;
666                 }
667                 err = resolve_indirect_ref(fs_info, path, time_seq, ref,
668                                            parents, extent_item_pos,
669                                            total_refs, ignore_offset);
670                 /*
671                  * we can only tolerate ENOENT,otherwise,we should catch error
672                  * and return directly.
673                  */
674                 if (err == -ENOENT) {
675                         prelim_ref_insert(fs_info, &preftrees->direct, ref,
676                                           NULL);
677                         continue;
678                 } else if (err) {
679                         free_pref(ref);
680                         ret = err;
681                         goto out;
682                 }
683
684                 /* we put the first parent into the ref at hand */
685                 ULIST_ITER_INIT(&uiter);
686                 node = ulist_next(parents, &uiter);
687                 ref->parent = node ? node->val : 0;
688                 ref->inode_list = unode_aux_to_inode_list(node);
689
690                 /* Add a prelim_ref(s) for any other parent(s). */
691                 while ((node = ulist_next(parents, &uiter))) {
692                         struct prelim_ref *new_ref;
693
694                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
695                                                    GFP_NOFS);
696                         if (!new_ref) {
697                                 free_pref(ref);
698                                 ret = -ENOMEM;
699                                 goto out;
700                         }
701                         memcpy(new_ref, ref, sizeof(*ref));
702                         new_ref->parent = node->val;
703                         new_ref->inode_list = unode_aux_to_inode_list(node);
704                         prelim_ref_insert(fs_info, &preftrees->direct,
705                                           new_ref, NULL);
706                 }
707
708                 /*
709                  * Now it's a direct ref, put it in the the direct tree. We must
710                  * do this last because the ref could be merged/freed here.
711                  */
712                 prelim_ref_insert(fs_info, &preftrees->direct, ref, NULL);
713
714                 ulist_reinit(parents);
715                 cond_resched();
716         }
717 out:
718         ulist_free(parents);
719         return ret;
720 }
721
722 /*
723  * read tree blocks and add keys where required.
724  */
725 static int add_missing_keys(struct btrfs_fs_info *fs_info,
726                             struct preftrees *preftrees)
727 {
728         struct prelim_ref *ref;
729         struct extent_buffer *eb;
730         struct preftree *tree = &preftrees->indirect_missing_keys;
731         struct rb_node *node;
732
733         while ((node = rb_first(&tree->root))) {
734                 ref = rb_entry(node, struct prelim_ref, rbnode);
735                 rb_erase(node, &tree->root);
736
737                 BUG_ON(ref->parent);    /* should not be a direct ref */
738                 BUG_ON(ref->key_for_search.type);
739                 BUG_ON(!ref->wanted_disk_byte);
740
741                 eb = read_tree_block(fs_info, ref->wanted_disk_byte, 0);
742                 if (IS_ERR(eb)) {
743                         free_pref(ref);
744                         return PTR_ERR(eb);
745                 } else if (!extent_buffer_uptodate(eb)) {
746                         free_pref(ref);
747                         free_extent_buffer(eb);
748                         return -EIO;
749                 }
750                 btrfs_tree_read_lock(eb);
751                 if (btrfs_header_level(eb) == 0)
752                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
753                 else
754                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
755                 btrfs_tree_read_unlock(eb);
756                 free_extent_buffer(eb);
757                 prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
758                 cond_resched();
759         }
760         return 0;
761 }
762
763 /*
764  * add all currently queued delayed refs from this head whose seq nr is
765  * smaller or equal that seq to the list
766  */
767 static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
768                             struct btrfs_delayed_ref_head *head, u64 seq,
769                             struct preftrees *preftrees, u64 *total_refs,
770                             struct share_check *sc)
771 {
772         struct btrfs_delayed_ref_node *node;
773         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
774         struct btrfs_key key;
775         struct btrfs_key tmp_op_key;
776         struct btrfs_key *op_key = NULL;
777         struct rb_node *n;
778         int count;
779         int ret = 0;
780
781         if (extent_op && extent_op->update_key) {
782                 btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
783                 op_key = &tmp_op_key;
784         }
785
786         spin_lock(&head->lock);
787         for (n = rb_first(&head->ref_tree); n; n = rb_next(n)) {
788                 node = rb_entry(n, struct btrfs_delayed_ref_node,
789                                 ref_node);
790                 if (node->seq > seq)
791                         continue;
792
793                 switch (node->action) {
794                 case BTRFS_ADD_DELAYED_EXTENT:
795                 case BTRFS_UPDATE_DELAYED_HEAD:
796                         WARN_ON(1);
797                         continue;
798                 case BTRFS_ADD_DELAYED_REF:
799                         count = node->ref_mod;
800                         break;
801                 case BTRFS_DROP_DELAYED_REF:
802                         count = node->ref_mod * -1;
803                         break;
804                 default:
805                         BUG_ON(1);
806                 }
807                 *total_refs += count;
808                 switch (node->type) {
809                 case BTRFS_TREE_BLOCK_REF_KEY: {
810                         /* NORMAL INDIRECT METADATA backref */
811                         struct btrfs_delayed_tree_ref *ref;
812
813                         ref = btrfs_delayed_node_to_tree_ref(node);
814                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
815                                                &tmp_op_key, ref->level + 1,
816                                                node->bytenr, count, sc,
817                                                GFP_ATOMIC);
818                         break;
819                 }
820                 case BTRFS_SHARED_BLOCK_REF_KEY: {
821                         /* SHARED DIRECT METADATA backref */
822                         struct btrfs_delayed_tree_ref *ref;
823
824                         ref = btrfs_delayed_node_to_tree_ref(node);
825
826                         ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
827                                              ref->parent, node->bytenr, count,
828                                              sc, GFP_ATOMIC);
829                         break;
830                 }
831                 case BTRFS_EXTENT_DATA_REF_KEY: {
832                         /* NORMAL INDIRECT DATA backref */
833                         struct btrfs_delayed_data_ref *ref;
834                         ref = btrfs_delayed_node_to_data_ref(node);
835
836                         key.objectid = ref->objectid;
837                         key.type = BTRFS_EXTENT_DATA_KEY;
838                         key.offset = ref->offset;
839
840                         /*
841                          * Found a inum that doesn't match our known inum, we
842                          * know it's shared.
843                          */
844                         if (sc && sc->inum && ref->objectid != sc->inum) {
845                                 ret = BACKREF_FOUND_SHARED;
846                                 goto out;
847                         }
848
849                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
850                                                &key, 0, node->bytenr, count, sc,
851                                                GFP_ATOMIC);
852                         break;
853                 }
854                 case BTRFS_SHARED_DATA_REF_KEY: {
855                         /* SHARED DIRECT FULL backref */
856                         struct btrfs_delayed_data_ref *ref;
857
858                         ref = btrfs_delayed_node_to_data_ref(node);
859
860                         ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
861                                              node->bytenr, count, sc,
862                                              GFP_ATOMIC);
863                         break;
864                 }
865                 default:
866                         WARN_ON(1);
867                 }
868                 /*
869                  * We must ignore BACKREF_FOUND_SHARED until all delayed
870                  * refs have been checked.
871                  */
872                 if (ret && (ret != BACKREF_FOUND_SHARED))
873                         break;
874         }
875         if (!ret)
876                 ret = extent_is_shared(sc);
877 out:
878         spin_unlock(&head->lock);
879         return ret;
880 }
881
882 /*
883  * add all inline backrefs for bytenr to the list
884  *
885  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
886  */
887 static int add_inline_refs(const struct btrfs_fs_info *fs_info,
888                            struct btrfs_path *path, u64 bytenr,
889                            int *info_level, struct preftrees *preftrees,
890                            u64 *total_refs, struct share_check *sc)
891 {
892         int ret = 0;
893         int slot;
894         struct extent_buffer *leaf;
895         struct btrfs_key key;
896         struct btrfs_key found_key;
897         unsigned long ptr;
898         unsigned long end;
899         struct btrfs_extent_item *ei;
900         u64 flags;
901         u64 item_size;
902
903         /*
904          * enumerate all inline refs
905          */
906         leaf = path->nodes[0];
907         slot = path->slots[0];
908
909         item_size = btrfs_item_size_nr(leaf, slot);
910         BUG_ON(item_size < sizeof(*ei));
911
912         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
913         flags = btrfs_extent_flags(leaf, ei);
914         *total_refs += btrfs_extent_refs(leaf, ei);
915         btrfs_item_key_to_cpu(leaf, &found_key, slot);
916
917         ptr = (unsigned long)(ei + 1);
918         end = (unsigned long)ei + item_size;
919
920         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
921             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
922                 struct btrfs_tree_block_info *info;
923
924                 info = (struct btrfs_tree_block_info *)ptr;
925                 *info_level = btrfs_tree_block_level(leaf, info);
926                 ptr += sizeof(struct btrfs_tree_block_info);
927                 BUG_ON(ptr > end);
928         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
929                 *info_level = found_key.offset;
930         } else {
931                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
932         }
933
934         while (ptr < end) {
935                 struct btrfs_extent_inline_ref *iref;
936                 u64 offset;
937                 int type;
938
939                 iref = (struct btrfs_extent_inline_ref *)ptr;
940                 type = btrfs_get_extent_inline_ref_type(leaf, iref,
941                                                         BTRFS_REF_TYPE_ANY);
942                 if (type == BTRFS_REF_TYPE_INVALID)
943                         return -EINVAL;
944
945                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
946
947                 switch (type) {
948                 case BTRFS_SHARED_BLOCK_REF_KEY:
949                         ret = add_direct_ref(fs_info, preftrees,
950                                              *info_level + 1, offset,
951                                              bytenr, 1, NULL, GFP_NOFS);
952                         break;
953                 case BTRFS_SHARED_DATA_REF_KEY: {
954                         struct btrfs_shared_data_ref *sdref;
955                         int count;
956
957                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
958                         count = btrfs_shared_data_ref_count(leaf, sdref);
959
960                         ret = add_direct_ref(fs_info, preftrees, 0, offset,
961                                              bytenr, count, sc, GFP_NOFS);
962                         break;
963                 }
964                 case BTRFS_TREE_BLOCK_REF_KEY:
965                         ret = add_indirect_ref(fs_info, preftrees, offset,
966                                                NULL, *info_level + 1,
967                                                bytenr, 1, NULL, GFP_NOFS);
968                         break;
969                 case BTRFS_EXTENT_DATA_REF_KEY: {
970                         struct btrfs_extent_data_ref *dref;
971                         int count;
972                         u64 root;
973
974                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
975                         count = btrfs_extent_data_ref_count(leaf, dref);
976                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
977                                                                       dref);
978                         key.type = BTRFS_EXTENT_DATA_KEY;
979                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
980
981                         if (sc && sc->inum && key.objectid != sc->inum) {
982                                 ret = BACKREF_FOUND_SHARED;
983                                 break;
984                         }
985
986                         root = btrfs_extent_data_ref_root(leaf, dref);
987
988                         ret = add_indirect_ref(fs_info, preftrees, root,
989                                                &key, 0, bytenr, count,
990                                                sc, GFP_NOFS);
991                         break;
992                 }
993                 default:
994                         WARN_ON(1);
995                 }
996                 if (ret)
997                         return ret;
998                 ptr += btrfs_extent_inline_ref_size(type);
999         }
1000
1001         return 0;
1002 }
1003
1004 /*
1005  * add all non-inline backrefs for bytenr to the list
1006  *
1007  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
1008  */
1009 static int add_keyed_refs(struct btrfs_fs_info *fs_info,
1010                           struct btrfs_path *path, u64 bytenr,
1011                           int info_level, struct preftrees *preftrees,
1012                           struct share_check *sc)
1013 {
1014         struct btrfs_root *extent_root = fs_info->extent_root;
1015         int ret;
1016         int slot;
1017         struct extent_buffer *leaf;
1018         struct btrfs_key key;
1019
1020         while (1) {
1021                 ret = btrfs_next_item(extent_root, path);
1022                 if (ret < 0)
1023                         break;
1024                 if (ret) {
1025                         ret = 0;
1026                         break;
1027                 }
1028
1029                 slot = path->slots[0];
1030                 leaf = path->nodes[0];
1031                 btrfs_item_key_to_cpu(leaf, &key, slot);
1032
1033                 if (key.objectid != bytenr)
1034                         break;
1035                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
1036                         continue;
1037                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
1038                         break;
1039
1040                 switch (key.type) {
1041                 case BTRFS_SHARED_BLOCK_REF_KEY:
1042                         /* SHARED DIRECT METADATA backref */
1043                         ret = add_direct_ref(fs_info, preftrees,
1044                                              info_level + 1, key.offset,
1045                                              bytenr, 1, NULL, GFP_NOFS);
1046                         break;
1047                 case BTRFS_SHARED_DATA_REF_KEY: {
1048                         /* SHARED DIRECT FULL backref */
1049                         struct btrfs_shared_data_ref *sdref;
1050                         int count;
1051
1052                         sdref = btrfs_item_ptr(leaf, slot,
1053                                               struct btrfs_shared_data_ref);
1054                         count = btrfs_shared_data_ref_count(leaf, sdref);
1055                         ret = add_direct_ref(fs_info, preftrees, 0,
1056                                              key.offset, bytenr, count,
1057                                              sc, GFP_NOFS);
1058                         break;
1059                 }
1060                 case BTRFS_TREE_BLOCK_REF_KEY:
1061                         /* NORMAL INDIRECT METADATA backref */
1062                         ret = add_indirect_ref(fs_info, preftrees, key.offset,
1063                                                NULL, info_level + 1, bytenr,
1064                                                1, NULL, GFP_NOFS);
1065                         break;
1066                 case BTRFS_EXTENT_DATA_REF_KEY: {
1067                         /* NORMAL INDIRECT DATA backref */
1068                         struct btrfs_extent_data_ref *dref;
1069                         int count;
1070                         u64 root;
1071
1072                         dref = btrfs_item_ptr(leaf, slot,
1073                                               struct btrfs_extent_data_ref);
1074                         count = btrfs_extent_data_ref_count(leaf, dref);
1075                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1076                                                                       dref);
1077                         key.type = BTRFS_EXTENT_DATA_KEY;
1078                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1079
1080                         if (sc && sc->inum && key.objectid != sc->inum) {
1081                                 ret = BACKREF_FOUND_SHARED;
1082                                 break;
1083                         }
1084
1085                         root = btrfs_extent_data_ref_root(leaf, dref);
1086                         ret = add_indirect_ref(fs_info, preftrees, root,
1087                                                &key, 0, bytenr, count,
1088                                                sc, GFP_NOFS);
1089                         break;
1090                 }
1091                 default:
1092                         WARN_ON(1);
1093                 }
1094                 if (ret)
1095                         return ret;
1096
1097         }
1098
1099         return ret;
1100 }
1101
1102 /*
1103  * this adds all existing backrefs (inline backrefs, backrefs and delayed
1104  * refs) for the given bytenr to the refs list, merges duplicates and resolves
1105  * indirect refs to their parent bytenr.
1106  * When roots are found, they're added to the roots list
1107  *
1108  * If time_seq is set to SEQ_LAST, it will not search delayed_refs, and behave
1109  * much like trans == NULL case, the difference only lies in it will not
1110  * commit root.
1111  * The special case is for qgroup to search roots in commit_transaction().
1112  *
1113  * @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a
1114  * shared extent is detected.
1115  *
1116  * Otherwise this returns 0 for success and <0 for an error.
1117  *
1118  * If ignore_offset is set to false, only extent refs whose offsets match
1119  * extent_item_pos are returned.  If true, every extent ref is returned
1120  * and extent_item_pos is ignored.
1121  *
1122  * FIXME some caching might speed things up
1123  */
1124 static int find_parent_nodes(struct btrfs_trans_handle *trans,
1125                              struct btrfs_fs_info *fs_info, u64 bytenr,
1126                              u64 time_seq, struct ulist *refs,
1127                              struct ulist *roots, const u64 *extent_item_pos,
1128                              struct share_check *sc, bool ignore_offset)
1129 {
1130         struct btrfs_key key;
1131         struct btrfs_path *path;
1132         struct btrfs_delayed_ref_root *delayed_refs = NULL;
1133         struct btrfs_delayed_ref_head *head;
1134         int info_level = 0;
1135         int ret;
1136         struct prelim_ref *ref;
1137         struct rb_node *node;
1138         struct extent_inode_elem *eie = NULL;
1139         /* total of both direct AND indirect refs! */
1140         u64 total_refs = 0;
1141         struct preftrees preftrees = {
1142                 .direct = PREFTREE_INIT,
1143                 .indirect = PREFTREE_INIT,
1144                 .indirect_missing_keys = PREFTREE_INIT
1145         };
1146
1147         key.objectid = bytenr;
1148         key.offset = (u64)-1;
1149         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1150                 key.type = BTRFS_METADATA_ITEM_KEY;
1151         else
1152                 key.type = BTRFS_EXTENT_ITEM_KEY;
1153
1154         path = btrfs_alloc_path();
1155         if (!path)
1156                 return -ENOMEM;
1157         if (!trans) {
1158                 path->search_commit_root = 1;
1159                 path->skip_locking = 1;
1160         }
1161
1162         if (time_seq == SEQ_LAST)
1163                 path->skip_locking = 1;
1164
1165         /*
1166          * grab both a lock on the path and a lock on the delayed ref head.
1167          * We need both to get a consistent picture of how the refs look
1168          * at a specified point in time
1169          */
1170 again:
1171         head = NULL;
1172
1173         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
1174         if (ret < 0)
1175                 goto out;
1176         BUG_ON(ret == 0);
1177
1178 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
1179         if (trans && likely(trans->type != __TRANS_DUMMY) &&
1180             time_seq != SEQ_LAST) {
1181 #else
1182         if (trans && time_seq != SEQ_LAST) {
1183 #endif
1184                 /*
1185                  * look if there are updates for this ref queued and lock the
1186                  * head
1187                  */
1188                 delayed_refs = &trans->transaction->delayed_refs;
1189                 spin_lock(&delayed_refs->lock);
1190                 head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
1191                 if (head) {
1192                         if (!mutex_trylock(&head->mutex)) {
1193                                 refcount_inc(&head->refs);
1194                                 spin_unlock(&delayed_refs->lock);
1195
1196                                 btrfs_release_path(path);
1197
1198                                 /*
1199                                  * Mutex was contended, block until it's
1200                                  * released and try again
1201                                  */
1202                                 mutex_lock(&head->mutex);
1203                                 mutex_unlock(&head->mutex);
1204                                 btrfs_put_delayed_ref_head(head);
1205                                 goto again;
1206                         }
1207                         spin_unlock(&delayed_refs->lock);
1208                         ret = add_delayed_refs(fs_info, head, time_seq,
1209                                                &preftrees, &total_refs, sc);
1210                         mutex_unlock(&head->mutex);
1211                         if (ret)
1212                                 goto out;
1213                 } else {
1214                         spin_unlock(&delayed_refs->lock);
1215                 }
1216         }
1217
1218         if (path->slots[0]) {
1219                 struct extent_buffer *leaf;
1220                 int slot;
1221
1222                 path->slots[0]--;
1223                 leaf = path->nodes[0];
1224                 slot = path->slots[0];
1225                 btrfs_item_key_to_cpu(leaf, &key, slot);
1226                 if (key.objectid == bytenr &&
1227                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
1228                      key.type == BTRFS_METADATA_ITEM_KEY)) {
1229                         ret = add_inline_refs(fs_info, path, bytenr,
1230                                               &info_level, &preftrees,
1231                                               &total_refs, sc);
1232                         if (ret)
1233                                 goto out;
1234                         ret = add_keyed_refs(fs_info, path, bytenr, info_level,
1235                                              &preftrees, sc);
1236                         if (ret)
1237                                 goto out;
1238                 }
1239         }
1240
1241         btrfs_release_path(path);
1242
1243         ret = add_missing_keys(fs_info, &preftrees);
1244         if (ret)
1245                 goto out;
1246
1247         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root));
1248
1249         ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
1250                                     extent_item_pos, total_refs, sc, ignore_offset);
1251         if (ret)
1252                 goto out;
1253
1254         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root));
1255
1256         /*
1257          * This walks the tree of merged and resolved refs. Tree blocks are
1258          * read in as needed. Unique entries are added to the ulist, and
1259          * the list of found roots is updated.
1260          *
1261          * We release the entire tree in one go before returning.
1262          */
1263         node = rb_first(&preftrees.direct.root);
1264         while (node) {
1265                 ref = rb_entry(node, struct prelim_ref, rbnode);
1266                 node = rb_next(&ref->rbnode);
1267                 /*
1268                  * ref->count < 0 can happen here if there are delayed
1269                  * refs with a node->action of BTRFS_DROP_DELAYED_REF.
1270                  * prelim_ref_insert() relies on this when merging
1271                  * identical refs to keep the overall count correct.
1272                  * prelim_ref_insert() will merge only those refs
1273                  * which compare identically.  Any refs having
1274                  * e.g. different offsets would not be merged,
1275                  * and would retain their original ref->count < 0.
1276                  */
1277                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1278                         if (sc && sc->root_objectid &&
1279                             ref->root_id != sc->root_objectid) {
1280                                 ret = BACKREF_FOUND_SHARED;
1281                                 goto out;
1282                         }
1283
1284                         /* no parent == root of tree */
1285                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1286                         if (ret < 0)
1287                                 goto out;
1288                 }
1289                 if (ref->count && ref->parent) {
1290                         if (extent_item_pos && !ref->inode_list &&
1291                             ref->level == 0) {
1292                                 struct extent_buffer *eb;
1293
1294                                 eb = read_tree_block(fs_info, ref->parent, 0);
1295                                 if (IS_ERR(eb)) {
1296                                         ret = PTR_ERR(eb);
1297                                         goto out;
1298                                 } else if (!extent_buffer_uptodate(eb)) {
1299                                         free_extent_buffer(eb);
1300                                         ret = -EIO;
1301                                         goto out;
1302                                 }
1303                                 btrfs_tree_read_lock(eb);
1304                                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1305                                 ret = find_extent_in_eb(eb, bytenr,
1306                                                         *extent_item_pos, &eie, ignore_offset);
1307                                 btrfs_tree_read_unlock_blocking(eb);
1308                                 free_extent_buffer(eb);
1309                                 if (ret < 0)
1310                                         goto out;
1311                                 ref->inode_list = eie;
1312                         }
1313                         ret = ulist_add_merge_ptr(refs, ref->parent,
1314                                                   ref->inode_list,
1315                                                   (void **)&eie, GFP_NOFS);
1316                         if (ret < 0)
1317                                 goto out;
1318                         if (!ret && extent_item_pos) {
1319                                 /*
1320                                  * we've recorded that parent, so we must extend
1321                                  * its inode list here
1322                                  */
1323                                 BUG_ON(!eie);
1324                                 while (eie->next)
1325                                         eie = eie->next;
1326                                 eie->next = ref->inode_list;
1327                         }
1328                         eie = NULL;
1329                 }
1330                 cond_resched();
1331         }
1332
1333 out:
1334         btrfs_free_path(path);
1335
1336         prelim_release(&preftrees.direct);
1337         prelim_release(&preftrees.indirect);
1338         prelim_release(&preftrees.indirect_missing_keys);
1339
1340         if (ret < 0)
1341                 free_inode_elem_list(eie);
1342         return ret;
1343 }
1344
1345 static void free_leaf_list(struct ulist *blocks)
1346 {
1347         struct ulist_node *node = NULL;
1348         struct extent_inode_elem *eie;
1349         struct ulist_iterator uiter;
1350
1351         ULIST_ITER_INIT(&uiter);
1352         while ((node = ulist_next(blocks, &uiter))) {
1353                 if (!node->aux)
1354                         continue;
1355                 eie = unode_aux_to_inode_list(node);
1356                 free_inode_elem_list(eie);
1357                 node->aux = 0;
1358         }
1359
1360         ulist_free(blocks);
1361 }
1362
1363 /*
1364  * Finds all leafs with a reference to the specified combination of bytenr and
1365  * offset. key_list_head will point to a list of corresponding keys (caller must
1366  * free each list element). The leafs will be stored in the leafs ulist, which
1367  * must be freed with ulist_free.
1368  *
1369  * returns 0 on success, <0 on error
1370  */
1371 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1372                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1373                                 u64 time_seq, struct ulist **leafs,
1374                                 const u64 *extent_item_pos, bool ignore_offset)
1375 {
1376         int ret;
1377
1378         *leafs = ulist_alloc(GFP_NOFS);
1379         if (!*leafs)
1380                 return -ENOMEM;
1381
1382         ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1383                                 *leafs, NULL, extent_item_pos, NULL, ignore_offset);
1384         if (ret < 0 && ret != -ENOENT) {
1385                 free_leaf_list(*leafs);
1386                 return ret;
1387         }
1388
1389         return 0;
1390 }
1391
1392 /*
1393  * walk all backrefs for a given extent to find all roots that reference this
1394  * extent. Walking a backref means finding all extents that reference this
1395  * extent and in turn walk the backrefs of those, too. Naturally this is a
1396  * recursive process, but here it is implemented in an iterative fashion: We
1397  * find all referencing extents for the extent in question and put them on a
1398  * list. In turn, we find all referencing extents for those, further appending
1399  * to the list. The way we iterate the list allows adding more elements after
1400  * the current while iterating. The process stops when we reach the end of the
1401  * list. Found roots are added to the roots list.
1402  *
1403  * returns 0 on success, < 0 on error.
1404  */
1405 static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
1406                                      struct btrfs_fs_info *fs_info, u64 bytenr,
1407                                      u64 time_seq, struct ulist **roots,
1408                                      bool ignore_offset)
1409 {
1410         struct ulist *tmp;
1411         struct ulist_node *node = NULL;
1412         struct ulist_iterator uiter;
1413         int ret;
1414
1415         tmp = ulist_alloc(GFP_NOFS);
1416         if (!tmp)
1417                 return -ENOMEM;
1418         *roots = ulist_alloc(GFP_NOFS);
1419         if (!*roots) {
1420                 ulist_free(tmp);
1421                 return -ENOMEM;
1422         }
1423
1424         ULIST_ITER_INIT(&uiter);
1425         while (1) {
1426                 ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1427                                         tmp, *roots, NULL, NULL, ignore_offset);
1428                 if (ret < 0 && ret != -ENOENT) {
1429                         ulist_free(tmp);
1430                         ulist_free(*roots);
1431                         return ret;
1432                 }
1433                 node = ulist_next(tmp, &uiter);
1434                 if (!node)
1435                         break;
1436                 bytenr = node->val;
1437                 cond_resched();
1438         }
1439
1440         ulist_free(tmp);
1441         return 0;
1442 }
1443
1444 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1445                          struct btrfs_fs_info *fs_info, u64 bytenr,
1446                          u64 time_seq, struct ulist **roots,
1447                          bool ignore_offset)
1448 {
1449         int ret;
1450
1451         if (!trans)
1452                 down_read(&fs_info->commit_root_sem);
1453         ret = btrfs_find_all_roots_safe(trans, fs_info, bytenr,
1454                                         time_seq, roots, ignore_offset);
1455         if (!trans)
1456                 up_read(&fs_info->commit_root_sem);
1457         return ret;
1458 }
1459
1460 /**
1461  * btrfs_check_shared - tell us whether an extent is shared
1462  *
1463  * btrfs_check_shared uses the backref walking code but will short
1464  * circuit as soon as it finds a root or inode that doesn't match the
1465  * one passed in. This provides a significant performance benefit for
1466  * callers (such as fiemap) which want to know whether the extent is
1467  * shared but do not need a ref count.
1468  *
1469  * This attempts to allocate a transaction in order to account for
1470  * delayed refs, but continues on even when the alloc fails.
1471  *
1472  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1473  */
1474 int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
1475 {
1476         struct btrfs_fs_info *fs_info = root->fs_info;
1477         struct btrfs_trans_handle *trans;
1478         struct ulist *tmp = NULL;
1479         struct ulist *roots = NULL;
1480         struct ulist_iterator uiter;
1481         struct ulist_node *node;
1482         struct seq_list elem = SEQ_LIST_INIT(elem);
1483         int ret = 0;
1484         struct share_check shared = {
1485                 .root_objectid = root->objectid,
1486                 .inum = inum,
1487                 .share_count = 0,
1488         };
1489
1490         tmp = ulist_alloc(GFP_NOFS);
1491         roots = ulist_alloc(GFP_NOFS);
1492         if (!tmp || !roots) {
1493                 ulist_free(tmp);
1494                 ulist_free(roots);
1495                 return -ENOMEM;
1496         }
1497
1498         trans = btrfs_join_transaction(root);
1499         if (IS_ERR(trans)) {
1500                 trans = NULL;
1501                 down_read(&fs_info->commit_root_sem);
1502         } else {
1503                 btrfs_get_tree_mod_seq(fs_info, &elem);
1504         }
1505
1506         ULIST_ITER_INIT(&uiter);
1507         while (1) {
1508                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1509                                         roots, NULL, &shared, false);
1510                 if (ret == BACKREF_FOUND_SHARED) {
1511                         /* this is the only condition under which we return 1 */
1512                         ret = 1;
1513                         break;
1514                 }
1515                 if (ret < 0 && ret != -ENOENT)
1516                         break;
1517                 ret = 0;
1518                 node = ulist_next(tmp, &uiter);
1519                 if (!node)
1520                         break;
1521                 bytenr = node->val;
1522                 cond_resched();
1523         }
1524
1525         if (trans) {
1526                 btrfs_put_tree_mod_seq(fs_info, &elem);
1527                 btrfs_end_transaction(trans);
1528         } else {
1529                 up_read(&fs_info->commit_root_sem);
1530         }
1531         ulist_free(tmp);
1532         ulist_free(roots);
1533         return ret;
1534 }
1535
1536 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1537                           u64 start_off, struct btrfs_path *path,
1538                           struct btrfs_inode_extref **ret_extref,
1539                           u64 *found_off)
1540 {
1541         int ret, slot;
1542         struct btrfs_key key;
1543         struct btrfs_key found_key;
1544         struct btrfs_inode_extref *extref;
1545         const struct extent_buffer *leaf;
1546         unsigned long ptr;
1547
1548         key.objectid = inode_objectid;
1549         key.type = BTRFS_INODE_EXTREF_KEY;
1550         key.offset = start_off;
1551
1552         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1553         if (ret < 0)
1554                 return ret;
1555
1556         while (1) {
1557                 leaf = path->nodes[0];
1558                 slot = path->slots[0];
1559                 if (slot >= btrfs_header_nritems(leaf)) {
1560                         /*
1561                          * If the item at offset is not found,
1562                          * btrfs_search_slot will point us to the slot
1563                          * where it should be inserted. In our case
1564                          * that will be the slot directly before the
1565                          * next INODE_REF_KEY_V2 item. In the case
1566                          * that we're pointing to the last slot in a
1567                          * leaf, we must move one leaf over.
1568                          */
1569                         ret = btrfs_next_leaf(root, path);
1570                         if (ret) {
1571                                 if (ret >= 1)
1572                                         ret = -ENOENT;
1573                                 break;
1574                         }
1575                         continue;
1576                 }
1577
1578                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1579
1580                 /*
1581                  * Check that we're still looking at an extended ref key for
1582                  * this particular objectid. If we have different
1583                  * objectid or type then there are no more to be found
1584                  * in the tree and we can exit.
1585                  */
1586                 ret = -ENOENT;
1587                 if (found_key.objectid != inode_objectid)
1588                         break;
1589                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1590                         break;
1591
1592                 ret = 0;
1593                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1594                 extref = (struct btrfs_inode_extref *)ptr;
1595                 *ret_extref = extref;
1596                 if (found_off)
1597                         *found_off = found_key.offset;
1598                 break;
1599         }
1600
1601         return ret;
1602 }
1603
1604 /*
1605  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1606  * Elements of the path are separated by '/' and the path is guaranteed to be
1607  * 0-terminated. the path is only given within the current file system.
1608  * Therefore, it never starts with a '/'. the caller is responsible to provide
1609  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1610  * the start point of the resulting string is returned. this pointer is within
1611  * dest, normally.
1612  * in case the path buffer would overflow, the pointer is decremented further
1613  * as if output was written to the buffer, though no more output is actually
1614  * generated. that way, the caller can determine how much space would be
1615  * required for the path to fit into the buffer. in that case, the returned
1616  * value will be smaller than dest. callers must check this!
1617  */
1618 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1619                         u32 name_len, unsigned long name_off,
1620                         struct extent_buffer *eb_in, u64 parent,
1621                         char *dest, u32 size)
1622 {
1623         int slot;
1624         u64 next_inum;
1625         int ret;
1626         s64 bytes_left = ((s64)size) - 1;
1627         struct extent_buffer *eb = eb_in;
1628         struct btrfs_key found_key;
1629         int leave_spinning = path->leave_spinning;
1630         struct btrfs_inode_ref *iref;
1631
1632         if (bytes_left >= 0)
1633                 dest[bytes_left] = '\0';
1634
1635         path->leave_spinning = 1;
1636         while (1) {
1637                 bytes_left -= name_len;
1638                 if (bytes_left >= 0)
1639                         read_extent_buffer(eb, dest + bytes_left,
1640                                            name_off, name_len);
1641                 if (eb != eb_in) {
1642                         if (!path->skip_locking)
1643                                 btrfs_tree_read_unlock_blocking(eb);
1644                         free_extent_buffer(eb);
1645                 }
1646                 ret = btrfs_find_item(fs_root, path, parent, 0,
1647                                 BTRFS_INODE_REF_KEY, &found_key);
1648                 if (ret > 0)
1649                         ret = -ENOENT;
1650                 if (ret)
1651                         break;
1652
1653                 next_inum = found_key.offset;
1654
1655                 /* regular exit ahead */
1656                 if (parent == next_inum)
1657                         break;
1658
1659                 slot = path->slots[0];
1660                 eb = path->nodes[0];
1661                 /* make sure we can use eb after releasing the path */
1662                 if (eb != eb_in) {
1663                         if (!path->skip_locking)
1664                                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1665                         path->nodes[0] = NULL;
1666                         path->locks[0] = 0;
1667                 }
1668                 btrfs_release_path(path);
1669                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1670
1671                 name_len = btrfs_inode_ref_name_len(eb, iref);
1672                 name_off = (unsigned long)(iref + 1);
1673
1674                 parent = next_inum;
1675                 --bytes_left;
1676                 if (bytes_left >= 0)
1677                         dest[bytes_left] = '/';
1678         }
1679
1680         btrfs_release_path(path);
1681         path->leave_spinning = leave_spinning;
1682
1683         if (ret)
1684                 return ERR_PTR(ret);
1685
1686         return dest + bytes_left;
1687 }
1688
1689 /*
1690  * this makes the path point to (logical EXTENT_ITEM *)
1691  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1692  * tree blocks and <0 on error.
1693  */
1694 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1695                         struct btrfs_path *path, struct btrfs_key *found_key,
1696                         u64 *flags_ret)
1697 {
1698         int ret;
1699         u64 flags;
1700         u64 size = 0;
1701         u32 item_size;
1702         const struct extent_buffer *eb;
1703         struct btrfs_extent_item *ei;
1704         struct btrfs_key key;
1705
1706         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1707                 key.type = BTRFS_METADATA_ITEM_KEY;
1708         else
1709                 key.type = BTRFS_EXTENT_ITEM_KEY;
1710         key.objectid = logical;
1711         key.offset = (u64)-1;
1712
1713         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1714         if (ret < 0)
1715                 return ret;
1716
1717         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1718         if (ret) {
1719                 if (ret > 0)
1720                         ret = -ENOENT;
1721                 return ret;
1722         }
1723         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1724         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1725                 size = fs_info->nodesize;
1726         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1727                 size = found_key->offset;
1728
1729         if (found_key->objectid > logical ||
1730             found_key->objectid + size <= logical) {
1731                 btrfs_debug(fs_info,
1732                         "logical %llu is not within any extent", logical);
1733                 return -ENOENT;
1734         }
1735
1736         eb = path->nodes[0];
1737         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1738         BUG_ON(item_size < sizeof(*ei));
1739
1740         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1741         flags = btrfs_extent_flags(eb, ei);
1742
1743         btrfs_debug(fs_info,
1744                 "logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
1745                  logical, logical - found_key->objectid, found_key->objectid,
1746                  found_key->offset, flags, item_size);
1747
1748         WARN_ON(!flags_ret);
1749         if (flags_ret) {
1750                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1751                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1752                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1753                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1754                 else
1755                         BUG_ON(1);
1756                 return 0;
1757         }
1758
1759         return -EIO;
1760 }
1761
1762 /*
1763  * helper function to iterate extent inline refs. ptr must point to a 0 value
1764  * for the first call and may be modified. it is used to track state.
1765  * if more refs exist, 0 is returned and the next call to
1766  * get_extent_inline_ref must pass the modified ptr parameter to get the
1767  * next ref. after the last ref was processed, 1 is returned.
1768  * returns <0 on error
1769  */
1770 static int get_extent_inline_ref(unsigned long *ptr,
1771                                  const struct extent_buffer *eb,
1772                                  const struct btrfs_key *key,
1773                                  const struct btrfs_extent_item *ei,
1774                                  u32 item_size,
1775                                  struct btrfs_extent_inline_ref **out_eiref,
1776                                  int *out_type)
1777 {
1778         unsigned long end;
1779         u64 flags;
1780         struct btrfs_tree_block_info *info;
1781
1782         if (!*ptr) {
1783                 /* first call */
1784                 flags = btrfs_extent_flags(eb, ei);
1785                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1786                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1787                                 /* a skinny metadata extent */
1788                                 *out_eiref =
1789                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1790                         } else {
1791                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1792                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1793                                 *out_eiref =
1794                                    (struct btrfs_extent_inline_ref *)(info + 1);
1795                         }
1796                 } else {
1797                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1798                 }
1799                 *ptr = (unsigned long)*out_eiref;
1800                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1801                         return -ENOENT;
1802         }
1803
1804         end = (unsigned long)ei + item_size;
1805         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1806         *out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
1807                                                      BTRFS_REF_TYPE_ANY);
1808         if (*out_type == BTRFS_REF_TYPE_INVALID)
1809                 return -EINVAL;
1810
1811         *ptr += btrfs_extent_inline_ref_size(*out_type);
1812         WARN_ON(*ptr > end);
1813         if (*ptr == end)
1814                 return 1; /* last */
1815
1816         return 0;
1817 }
1818
1819 /*
1820  * reads the tree block backref for an extent. tree level and root are returned
1821  * through out_level and out_root. ptr must point to a 0 value for the first
1822  * call and may be modified (see get_extent_inline_ref comment).
1823  * returns 0 if data was provided, 1 if there was no more data to provide or
1824  * <0 on error.
1825  */
1826 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1827                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1828                             u32 item_size, u64 *out_root, u8 *out_level)
1829 {
1830         int ret;
1831         int type;
1832         struct btrfs_extent_inline_ref *eiref;
1833
1834         if (*ptr == (unsigned long)-1)
1835                 return 1;
1836
1837         while (1) {
1838                 ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
1839                                               &eiref, &type);
1840                 if (ret < 0)
1841                         return ret;
1842
1843                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1844                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1845                         break;
1846
1847                 if (ret == 1)
1848                         return 1;
1849         }
1850
1851         /* we can treat both ref types equally here */
1852         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1853
1854         if (key->type == BTRFS_EXTENT_ITEM_KEY) {
1855                 struct btrfs_tree_block_info *info;
1856
1857                 info = (struct btrfs_tree_block_info *)(ei + 1);
1858                 *out_level = btrfs_tree_block_level(eb, info);
1859         } else {
1860                 ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
1861                 *out_level = (u8)key->offset;
1862         }
1863
1864         if (ret == 1)
1865                 *ptr = (unsigned long)-1;
1866
1867         return 0;
1868 }
1869
1870 static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
1871                              struct extent_inode_elem *inode_list,
1872                              u64 root, u64 extent_item_objectid,
1873                              iterate_extent_inodes_t *iterate, void *ctx)
1874 {
1875         struct extent_inode_elem *eie;
1876         int ret = 0;
1877
1878         for (eie = inode_list; eie; eie = eie->next) {
1879                 btrfs_debug(fs_info,
1880                             "ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
1881                             extent_item_objectid, eie->inum,
1882                             eie->offset, root);
1883                 ret = iterate(eie->inum, eie->offset, root, ctx);
1884                 if (ret) {
1885                         btrfs_debug(fs_info,
1886                                     "stopping iteration for %llu due to ret=%d",
1887                                     extent_item_objectid, ret);
1888                         break;
1889                 }
1890         }
1891
1892         return ret;
1893 }
1894
1895 /*
1896  * calls iterate() for every inode that references the extent identified by
1897  * the given parameters.
1898  * when the iterator function returns a non-zero value, iteration stops.
1899  */
1900 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1901                                 u64 extent_item_objectid, u64 extent_item_pos,
1902                                 int search_commit_root,
1903                                 iterate_extent_inodes_t *iterate, void *ctx,
1904                                 bool ignore_offset)
1905 {
1906         int ret;
1907         struct btrfs_trans_handle *trans = NULL;
1908         struct ulist *refs = NULL;
1909         struct ulist *roots = NULL;
1910         struct ulist_node *ref_node = NULL;
1911         struct ulist_node *root_node = NULL;
1912         struct seq_list tree_mod_seq_elem = SEQ_LIST_INIT(tree_mod_seq_elem);
1913         struct ulist_iterator ref_uiter;
1914         struct ulist_iterator root_uiter;
1915
1916         btrfs_debug(fs_info, "resolving all inodes for extent %llu",
1917                         extent_item_objectid);
1918
1919         if (!search_commit_root) {
1920                 trans = btrfs_join_transaction(fs_info->extent_root);
1921                 if (IS_ERR(trans))
1922                         return PTR_ERR(trans);
1923                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1924         } else {
1925                 down_read(&fs_info->commit_root_sem);
1926         }
1927
1928         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1929                                    tree_mod_seq_elem.seq, &refs,
1930                                    &extent_item_pos, ignore_offset);
1931         if (ret)
1932                 goto out;
1933
1934         ULIST_ITER_INIT(&ref_uiter);
1935         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1936                 ret = btrfs_find_all_roots_safe(trans, fs_info, ref_node->val,
1937                                                 tree_mod_seq_elem.seq, &roots,
1938                                                 ignore_offset);
1939                 if (ret)
1940                         break;
1941                 ULIST_ITER_INIT(&root_uiter);
1942                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1943                         btrfs_debug(fs_info,
1944                                     "root %llu references leaf %llu, data list %#llx",
1945                                     root_node->val, ref_node->val,
1946                                     ref_node->aux);
1947                         ret = iterate_leaf_refs(fs_info,
1948                                                 (struct extent_inode_elem *)
1949                                                 (uintptr_t)ref_node->aux,
1950                                                 root_node->val,
1951                                                 extent_item_objectid,
1952                                                 iterate, ctx);
1953                 }
1954                 ulist_free(roots);
1955         }
1956
1957         free_leaf_list(refs);
1958 out:
1959         if (!search_commit_root) {
1960                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1961                 btrfs_end_transaction(trans);
1962         } else {
1963                 up_read(&fs_info->commit_root_sem);
1964         }
1965
1966         return ret;
1967 }
1968
1969 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1970                                 struct btrfs_path *path,
1971                                 iterate_extent_inodes_t *iterate, void *ctx,
1972                                 bool ignore_offset)
1973 {
1974         int ret;
1975         u64 extent_item_pos;
1976         u64 flags = 0;
1977         struct btrfs_key found_key;
1978         int search_commit_root = path->search_commit_root;
1979
1980         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1981         btrfs_release_path(path);
1982         if (ret < 0)
1983                 return ret;
1984         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1985                 return -EINVAL;
1986
1987         extent_item_pos = logical - found_key.objectid;
1988         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1989                                         extent_item_pos, search_commit_root,
1990                                         iterate, ctx, ignore_offset);
1991
1992         return ret;
1993 }
1994
1995 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1996                               struct extent_buffer *eb, void *ctx);
1997
1998 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1999                               struct btrfs_path *path,
2000                               iterate_irefs_t *iterate, void *ctx)
2001 {
2002         int ret = 0;
2003         int slot;
2004         u32 cur;
2005         u32 len;
2006         u32 name_len;
2007         u64 parent = 0;
2008         int found = 0;
2009         struct extent_buffer *eb;
2010         struct btrfs_item *item;
2011         struct btrfs_inode_ref *iref;
2012         struct btrfs_key found_key;
2013
2014         while (!ret) {
2015                 ret = btrfs_find_item(fs_root, path, inum,
2016                                 parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
2017                                 &found_key);
2018
2019                 if (ret < 0)
2020                         break;
2021                 if (ret) {
2022                         ret = found ? 0 : -ENOENT;
2023                         break;
2024                 }
2025                 ++found;
2026
2027                 parent = found_key.offset;
2028                 slot = path->slots[0];
2029                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2030                 if (!eb) {
2031                         ret = -ENOMEM;
2032                         break;
2033                 }
2034                 extent_buffer_get(eb);
2035                 btrfs_tree_read_lock(eb);
2036                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
2037                 btrfs_release_path(path);
2038
2039                 item = btrfs_item_nr(slot);
2040                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2041
2042                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
2043                         name_len = btrfs_inode_ref_name_len(eb, iref);
2044                         /* path must be released before calling iterate()! */
2045                         btrfs_debug(fs_root->fs_info,
2046                                 "following ref at offset %u for inode %llu in tree %llu",
2047                                 cur, found_key.objectid, fs_root->objectid);
2048                         ret = iterate(parent, name_len,
2049                                       (unsigned long)(iref + 1), eb, ctx);
2050                         if (ret)
2051                                 break;
2052                         len = sizeof(*iref) + name_len;
2053                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
2054                 }
2055                 btrfs_tree_read_unlock_blocking(eb);
2056                 free_extent_buffer(eb);
2057         }
2058
2059         btrfs_release_path(path);
2060
2061         return ret;
2062 }
2063
2064 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
2065                                  struct btrfs_path *path,
2066                                  iterate_irefs_t *iterate, void *ctx)
2067 {
2068         int ret;
2069         int slot;
2070         u64 offset = 0;
2071         u64 parent;
2072         int found = 0;
2073         struct extent_buffer *eb;
2074         struct btrfs_inode_extref *extref;
2075         u32 item_size;
2076         u32 cur_offset;
2077         unsigned long ptr;
2078
2079         while (1) {
2080                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
2081                                             &offset);
2082                 if (ret < 0)
2083                         break;
2084                 if (ret) {
2085                         ret = found ? 0 : -ENOENT;
2086                         break;
2087                 }
2088                 ++found;
2089
2090                 slot = path->slots[0];
2091                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2092                 if (!eb) {
2093                         ret = -ENOMEM;
2094                         break;
2095                 }
2096                 extent_buffer_get(eb);
2097
2098                 btrfs_tree_read_lock(eb);
2099                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
2100                 btrfs_release_path(path);
2101
2102                 item_size = btrfs_item_size_nr(eb, slot);
2103                 ptr = btrfs_item_ptr_offset(eb, slot);
2104                 cur_offset = 0;
2105
2106                 while (cur_offset < item_size) {
2107                         u32 name_len;
2108
2109                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
2110                         parent = btrfs_inode_extref_parent(eb, extref);
2111                         name_len = btrfs_inode_extref_name_len(eb, extref);
2112                         ret = iterate(parent, name_len,
2113                                       (unsigned long)&extref->name, eb, ctx);
2114                         if (ret)
2115                                 break;
2116
2117                         cur_offset += btrfs_inode_extref_name_len(eb, extref);
2118                         cur_offset += sizeof(*extref);
2119                 }
2120                 btrfs_tree_read_unlock_blocking(eb);
2121                 free_extent_buffer(eb);
2122
2123                 offset++;
2124         }
2125
2126         btrfs_release_path(path);
2127
2128         return ret;
2129 }
2130
2131 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
2132                          struct btrfs_path *path, iterate_irefs_t *iterate,
2133                          void *ctx)
2134 {
2135         int ret;
2136         int found_refs = 0;
2137
2138         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
2139         if (!ret)
2140                 ++found_refs;
2141         else if (ret != -ENOENT)
2142                 return ret;
2143
2144         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
2145         if (ret == -ENOENT && found_refs)
2146                 return 0;
2147
2148         return ret;
2149 }
2150
2151 /*
2152  * returns 0 if the path could be dumped (probably truncated)
2153  * returns <0 in case of an error
2154  */
2155 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2156                          struct extent_buffer *eb, void *ctx)
2157 {
2158         struct inode_fs_paths *ipath = ctx;
2159         char *fspath;
2160         char *fspath_min;
2161         int i = ipath->fspath->elem_cnt;
2162         const int s_ptr = sizeof(char *);
2163         u32 bytes_left;
2164
2165         bytes_left = ipath->fspath->bytes_left > s_ptr ?
2166                                         ipath->fspath->bytes_left - s_ptr : 0;
2167
2168         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
2169         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
2170                                    name_off, eb, inum, fspath_min, bytes_left);
2171         if (IS_ERR(fspath))
2172                 return PTR_ERR(fspath);
2173
2174         if (fspath > fspath_min) {
2175                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
2176                 ++ipath->fspath->elem_cnt;
2177                 ipath->fspath->bytes_left = fspath - fspath_min;
2178         } else {
2179                 ++ipath->fspath->elem_missed;
2180                 ipath->fspath->bytes_missing += fspath_min - fspath;
2181                 ipath->fspath->bytes_left = 0;
2182         }
2183
2184         return 0;
2185 }
2186
2187 /*
2188  * this dumps all file system paths to the inode into the ipath struct, provided
2189  * is has been created large enough. each path is zero-terminated and accessed
2190  * from ipath->fspath->val[i].
2191  * when it returns, there are ipath->fspath->elem_cnt number of paths available
2192  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
2193  * number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
2194  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
2195  * have been needed to return all paths.
2196  */
2197 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
2198 {
2199         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
2200                              inode_to_path, ipath);
2201 }
2202
2203 struct btrfs_data_container *init_data_container(u32 total_bytes)
2204 {
2205         struct btrfs_data_container *data;
2206         size_t alloc_bytes;
2207
2208         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
2209         data = kvmalloc(alloc_bytes, GFP_KERNEL);
2210         if (!data)
2211                 return ERR_PTR(-ENOMEM);
2212
2213         if (total_bytes >= sizeof(*data)) {
2214                 data->bytes_left = total_bytes - sizeof(*data);
2215                 data->bytes_missing = 0;
2216         } else {
2217                 data->bytes_missing = sizeof(*data) - total_bytes;
2218                 data->bytes_left = 0;
2219         }
2220
2221         data->elem_cnt = 0;
2222         data->elem_missed = 0;
2223
2224         return data;
2225 }
2226
2227 /*
2228  * allocates space to return multiple file system paths for an inode.
2229  * total_bytes to allocate are passed, note that space usable for actual path
2230  * information will be total_bytes - sizeof(struct inode_fs_paths).
2231  * the returned pointer must be freed with free_ipath() in the end.
2232  */
2233 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
2234                                         struct btrfs_path *path)
2235 {
2236         struct inode_fs_paths *ifp;
2237         struct btrfs_data_container *fspath;
2238
2239         fspath = init_data_container(total_bytes);
2240         if (IS_ERR(fspath))
2241                 return (void *)fspath;
2242
2243         ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
2244         if (!ifp) {
2245                 kvfree(fspath);
2246                 return ERR_PTR(-ENOMEM);
2247         }
2248
2249         ifp->btrfs_path = path;
2250         ifp->fspath = fspath;
2251         ifp->fs_root = fs_root;
2252
2253         return ifp;
2254 }
2255
2256 void free_ipath(struct inode_fs_paths *ipath)
2257 {
2258         if (!ipath)
2259                 return;
2260         kvfree(ipath->fspath);
2261         kfree(ipath);
2262 }