Merge branch 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
[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 {
45         u64 offset = 0;
46         struct extent_inode_elem *e;
47
48         if (!btrfs_file_extent_compression(eb, fi) &&
49             !btrfs_file_extent_encryption(eb, fi) &&
50             !btrfs_file_extent_other_encoding(eb, fi)) {
51                 u64 data_offset;
52                 u64 data_len;
53
54                 data_offset = btrfs_file_extent_offset(eb, fi);
55                 data_len = btrfs_file_extent_num_bytes(eb, fi);
56
57                 if (extent_item_pos < data_offset ||
58                     extent_item_pos >= data_offset + data_len)
59                         return 1;
60                 offset = extent_item_pos - data_offset;
61         }
62
63         e = kmalloc(sizeof(*e), GFP_NOFS);
64         if (!e)
65                 return -ENOMEM;
66
67         e->next = *eie;
68         e->inum = key->objectid;
69         e->offset = key->offset + offset;
70         *eie = e;
71
72         return 0;
73 }
74
75 static void free_inode_elem_list(struct extent_inode_elem *eie)
76 {
77         struct extent_inode_elem *eie_next;
78
79         for (; eie; eie = eie_next) {
80                 eie_next = eie->next;
81                 kfree(eie);
82         }
83 }
84
85 static int find_extent_in_eb(const struct extent_buffer *eb,
86                              u64 wanted_disk_byte, u64 extent_item_pos,
87                              struct extent_inode_elem **eie)
88 {
89         u64 disk_byte;
90         struct btrfs_key key;
91         struct btrfs_file_extent_item *fi;
92         int slot;
93         int nritems;
94         int extent_type;
95         int ret;
96
97         /*
98          * from the shared data ref, we only have the leaf but we need
99          * the key. thus, we must look into all items and see that we
100          * find one (some) with a reference to our extent item.
101          */
102         nritems = btrfs_header_nritems(eb);
103         for (slot = 0; slot < nritems; ++slot) {
104                 btrfs_item_key_to_cpu(eb, &key, slot);
105                 if (key.type != BTRFS_EXTENT_DATA_KEY)
106                         continue;
107                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
108                 extent_type = btrfs_file_extent_type(eb, fi);
109                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
110                         continue;
111                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
112                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
113                 if (disk_byte != wanted_disk_byte)
114                         continue;
115
116                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
117                 if (ret < 0)
118                         return ret;
119         }
120
121         return 0;
122 }
123
124 struct preftree {
125         struct rb_root root;
126         unsigned int count;
127 };
128
129 #define PREFTREE_INIT   { .root = RB_ROOT, .count = 0 }
130
131 struct preftrees {
132         struct preftree direct;    /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
133         struct preftree indirect;  /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
134         struct preftree indirect_missing_keys;
135 };
136
137 /*
138  * Checks for a shared extent during backref search.
139  *
140  * The share_count tracks prelim_refs (direct and indirect) having a
141  * ref->count >0:
142  *  - incremented when a ref->count transitions to >0
143  *  - decremented when a ref->count transitions to <1
144  */
145 struct share_check {
146         u64 root_objectid;
147         u64 inum;
148         int share_count;
149 };
150
151 static inline int extent_is_shared(struct share_check *sc)
152 {
153         return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
154 }
155
156 static struct kmem_cache *btrfs_prelim_ref_cache;
157
158 int __init btrfs_prelim_ref_init(void)
159 {
160         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
161                                         sizeof(struct prelim_ref),
162                                         0,
163                                         SLAB_MEM_SPREAD,
164                                         NULL);
165         if (!btrfs_prelim_ref_cache)
166                 return -ENOMEM;
167         return 0;
168 }
169
170 void btrfs_prelim_ref_exit(void)
171 {
172         kmem_cache_destroy(btrfs_prelim_ref_cache);
173 }
174
175 static void free_pref(struct prelim_ref *ref)
176 {
177         kmem_cache_free(btrfs_prelim_ref_cache, ref);
178 }
179
180 /*
181  * Return 0 when both refs are for the same block (and can be merged).
182  * A -1 return indicates ref1 is a 'lower' block than ref2, while 1
183  * indicates a 'higher' block.
184  */
185 static int prelim_ref_compare(struct prelim_ref *ref1,
186                               struct prelim_ref *ref2)
187 {
188         if (ref1->level < ref2->level)
189                 return -1;
190         if (ref1->level > ref2->level)
191                 return 1;
192         if (ref1->root_id < ref2->root_id)
193                 return -1;
194         if (ref1->root_id > ref2->root_id)
195                 return 1;
196         if (ref1->key_for_search.type < ref2->key_for_search.type)
197                 return -1;
198         if (ref1->key_for_search.type > ref2->key_for_search.type)
199                 return 1;
200         if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
201                 return -1;
202         if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
203                 return 1;
204         if (ref1->key_for_search.offset < ref2->key_for_search.offset)
205                 return -1;
206         if (ref1->key_for_search.offset > ref2->key_for_search.offset)
207                 return 1;
208         if (ref1->parent < ref2->parent)
209                 return -1;
210         if (ref1->parent > ref2->parent)
211                 return 1;
212
213         return 0;
214 }
215
216 void update_share_count(struct share_check *sc, int oldcount, int newcount)
217 {
218         if ((!sc) || (oldcount == 0 && newcount < 1))
219                 return;
220
221         if (oldcount > 0 && newcount < 1)
222                 sc->share_count--;
223         else if (oldcount < 1 && newcount > 0)
224                 sc->share_count++;
225 }
226
227 /*
228  * Add @newref to the @root rbtree, merging identical refs.
229  *
230  * Callers should assume that newref has been freed after calling.
231  */
232 static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
233                               struct preftree *preftree,
234                               struct prelim_ref *newref,
235                               struct share_check *sc)
236 {
237         struct rb_root *root;
238         struct rb_node **p;
239         struct rb_node *parent = NULL;
240         struct prelim_ref *ref;
241         int result;
242
243         root = &preftree->root;
244         p = &root->rb_node;
245
246         while (*p) {
247                 parent = *p;
248                 ref = rb_entry(parent, struct prelim_ref, rbnode);
249                 result = prelim_ref_compare(ref, newref);
250                 if (result < 0) {
251                         p = &(*p)->rb_left;
252                 } else if (result > 0) {
253                         p = &(*p)->rb_right;
254                 } else {
255                         /* Identical refs, merge them and free @newref */
256                         struct extent_inode_elem *eie = ref->inode_list;
257
258                         while (eie && eie->next)
259                                 eie = eie->next;
260
261                         if (!eie)
262                                 ref->inode_list = newref->inode_list;
263                         else
264                                 eie->next = newref->inode_list;
265                         trace_btrfs_prelim_ref_merge(fs_info, ref, newref,
266                                                      preftree->count);
267                         /*
268                          * A delayed ref can have newref->count < 0.
269                          * The ref->count is updated to follow any
270                          * BTRFS_[ADD|DROP]_DELAYED_REF actions.
271                          */
272                         update_share_count(sc, ref->count,
273                                            ref->count + newref->count);
274                         ref->count += newref->count;
275                         free_pref(newref);
276                         return;
277                 }
278         }
279
280         update_share_count(sc, 0, newref->count);
281         preftree->count++;
282         trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
283         rb_link_node(&newref->rbnode, parent, p);
284         rb_insert_color(&newref->rbnode, root);
285 }
286
287 /*
288  * Release the entire tree.  We don't care about internal consistency so
289  * just free everything and then reset the tree root.
290  */
291 static void prelim_release(struct preftree *preftree)
292 {
293         struct prelim_ref *ref, *next_ref;
294
295         rbtree_postorder_for_each_entry_safe(ref, next_ref, &preftree->root,
296                                              rbnode)
297                 free_pref(ref);
298
299         preftree->root = RB_ROOT;
300         preftree->count = 0;
301 }
302
303 /*
304  * the rules for all callers of this function are:
305  * - obtaining the parent is the goal
306  * - if you add a key, you must know that it is a correct key
307  * - if you cannot add the parent or a correct key, then we will look into the
308  *   block later to set a correct key
309  *
310  * delayed refs
311  * ============
312  *        backref type | shared | indirect | shared | indirect
313  * information         |   tree |     tree |   data |     data
314  * --------------------+--------+----------+--------+----------
315  *      parent logical |    y   |     -    |    -   |     -
316  *      key to resolve |    -   |     y    |    y   |     y
317  *  tree block logical |    -   |     -    |    -   |     -
318  *  root for resolving |    y   |     y    |    y   |     y
319  *
320  * - column 1:       we've the parent -> done
321  * - column 2, 3, 4: we use the key to find the parent
322  *
323  * on disk refs (inline or keyed)
324  * ==============================
325  *        backref type | shared | indirect | shared | indirect
326  * information         |   tree |     tree |   data |     data
327  * --------------------+--------+----------+--------+----------
328  *      parent logical |    y   |     -    |    y   |     -
329  *      key to resolve |    -   |     -    |    -   |     y
330  *  tree block logical |    y   |     y    |    y   |     y
331  *  root for resolving |    -   |     y    |    y   |     y
332  *
333  * - column 1, 3: we've the parent -> done
334  * - column 2:    we take the first key from the block to find the parent
335  *                (see add_missing_keys)
336  * - column 4:    we use the key to find the parent
337  *
338  * additional information that's available but not required to find the parent
339  * block might help in merging entries to gain some speed.
340  */
341 static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
342                           struct preftree *preftree, u64 root_id,
343                           const struct btrfs_key *key, int level, u64 parent,
344                           u64 wanted_disk_byte, int count,
345                           struct share_check *sc, gfp_t gfp_mask)
346 {
347         struct prelim_ref *ref;
348
349         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
350                 return 0;
351
352         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
353         if (!ref)
354                 return -ENOMEM;
355
356         ref->root_id = root_id;
357         if (key) {
358                 ref->key_for_search = *key;
359                 /*
360                  * We can often find data backrefs with an offset that is too
361                  * large (>= LLONG_MAX, maximum allowed file offset) due to
362                  * underflows when subtracting a file's offset with the data
363                  * offset of its corresponding extent data item. This can
364                  * happen for example in the clone ioctl.
365                  * So if we detect such case we set the search key's offset to
366                  * zero to make sure we will find the matching file extent item
367                  * at add_all_parents(), otherwise we will miss it because the
368                  * offset taken form the backref is much larger then the offset
369                  * of the file extent item. This can make us scan a very large
370                  * number of file extent items, but at least it will not make
371                  * us miss any.
372                  * This is an ugly workaround for a behaviour that should have
373                  * never existed, but it does and a fix for the clone ioctl
374                  * would touch a lot of places, cause backwards incompatibility
375                  * and would not fix the problem for extents cloned with older
376                  * kernels.
377                  */
378                 if (ref->key_for_search.type == BTRFS_EXTENT_DATA_KEY &&
379                     ref->key_for_search.offset >= LLONG_MAX)
380                         ref->key_for_search.offset = 0;
381         } else {
382                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
383         }
384
385         ref->inode_list = NULL;
386         ref->level = level;
387         ref->count = count;
388         ref->parent = parent;
389         ref->wanted_disk_byte = wanted_disk_byte;
390         prelim_ref_insert(fs_info, preftree, ref, sc);
391         return extent_is_shared(sc);
392 }
393
394 /* direct refs use root == 0, key == NULL */
395 static int add_direct_ref(const struct btrfs_fs_info *fs_info,
396                           struct preftrees *preftrees, int level, u64 parent,
397                           u64 wanted_disk_byte, int count,
398                           struct share_check *sc, gfp_t gfp_mask)
399 {
400         return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level,
401                               parent, wanted_disk_byte, count, sc, gfp_mask);
402 }
403
404 /* indirect refs use parent == 0 */
405 static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
406                             struct preftrees *preftrees, u64 root_id,
407                             const struct btrfs_key *key, int level,
408                             u64 wanted_disk_byte, int count,
409                             struct share_check *sc, gfp_t gfp_mask)
410 {
411         struct preftree *tree = &preftrees->indirect;
412
413         if (!key)
414                 tree = &preftrees->indirect_missing_keys;
415         return add_prelim_ref(fs_info, tree, root_id, key, level, 0,
416                               wanted_disk_byte, count, sc, gfp_mask);
417 }
418
419 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
420                            struct ulist *parents, struct prelim_ref *ref,
421                            int level, u64 time_seq, const u64 *extent_item_pos,
422                            u64 total_refs)
423 {
424         int ret = 0;
425         int slot;
426         struct extent_buffer *eb;
427         struct btrfs_key key;
428         struct btrfs_key *key_for_search = &ref->key_for_search;
429         struct btrfs_file_extent_item *fi;
430         struct extent_inode_elem *eie = NULL, *old = NULL;
431         u64 disk_byte;
432         u64 wanted_disk_byte = ref->wanted_disk_byte;
433         u64 count = 0;
434
435         if (level != 0) {
436                 eb = path->nodes[level];
437                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
438                 if (ret < 0)
439                         return ret;
440                 return 0;
441         }
442
443         /*
444          * We normally enter this function with the path already pointing to
445          * the first item to check. But sometimes, we may enter it with
446          * slot==nritems. In that case, go to the next leaf before we continue.
447          */
448         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
449                 if (time_seq == SEQ_LAST)
450                         ret = btrfs_next_leaf(root, path);
451                 else
452                         ret = btrfs_next_old_leaf(root, path, time_seq);
453         }
454
455         while (!ret && count < total_refs) {
456                 eb = path->nodes[0];
457                 slot = path->slots[0];
458
459                 btrfs_item_key_to_cpu(eb, &key, slot);
460
461                 if (key.objectid != key_for_search->objectid ||
462                     key.type != BTRFS_EXTENT_DATA_KEY)
463                         break;
464
465                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
466                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
467
468                 if (disk_byte == wanted_disk_byte) {
469                         eie = NULL;
470                         old = NULL;
471                         count++;
472                         if (extent_item_pos) {
473                                 ret = check_extent_in_eb(&key, eb, fi,
474                                                 *extent_item_pos,
475                                                 &eie);
476                                 if (ret < 0)
477                                         break;
478                         }
479                         if (ret > 0)
480                                 goto next;
481                         ret = ulist_add_merge_ptr(parents, eb->start,
482                                                   eie, (void **)&old, GFP_NOFS);
483                         if (ret < 0)
484                                 break;
485                         if (!ret && extent_item_pos) {
486                                 while (old->next)
487                                         old = old->next;
488                                 old->next = eie;
489                         }
490                         eie = NULL;
491                 }
492 next:
493                 if (time_seq == SEQ_LAST)
494                         ret = btrfs_next_item(root, path);
495                 else
496                         ret = btrfs_next_old_item(root, path, time_seq);
497         }
498
499         if (ret > 0)
500                 ret = 0;
501         else if (ret < 0)
502                 free_inode_elem_list(eie);
503         return ret;
504 }
505
506 /*
507  * resolve an indirect backref in the form (root_id, key, level)
508  * to a logical address
509  */
510 static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
511                                 struct btrfs_path *path, u64 time_seq,
512                                 struct prelim_ref *ref, struct ulist *parents,
513                                 const u64 *extent_item_pos, u64 total_refs)
514 {
515         struct btrfs_root *root;
516         struct btrfs_key root_key;
517         struct extent_buffer *eb;
518         int ret = 0;
519         int root_level;
520         int level = ref->level;
521         int index;
522
523         root_key.objectid = ref->root_id;
524         root_key.type = BTRFS_ROOT_ITEM_KEY;
525         root_key.offset = (u64)-1;
526
527         index = srcu_read_lock(&fs_info->subvol_srcu);
528
529         root = btrfs_get_fs_root(fs_info, &root_key, false);
530         if (IS_ERR(root)) {
531                 srcu_read_unlock(&fs_info->subvol_srcu, index);
532                 ret = PTR_ERR(root);
533                 goto out;
534         }
535
536         if (btrfs_is_testing(fs_info)) {
537                 srcu_read_unlock(&fs_info->subvol_srcu, index);
538                 ret = -ENOENT;
539                 goto out;
540         }
541
542         if (path->search_commit_root)
543                 root_level = btrfs_header_level(root->commit_root);
544         else if (time_seq == SEQ_LAST)
545                 root_level = btrfs_header_level(root->node);
546         else
547                 root_level = btrfs_old_root_level(root, time_seq);
548
549         if (root_level + 1 == level) {
550                 srcu_read_unlock(&fs_info->subvol_srcu, index);
551                 goto out;
552         }
553
554         path->lowest_level = level;
555         if (time_seq == SEQ_LAST)
556                 ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
557                                         0, 0);
558         else
559                 ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
560                                             time_seq);
561
562         /* root node has been locked, we can release @subvol_srcu safely here */
563         srcu_read_unlock(&fs_info->subvol_srcu, index);
564
565         btrfs_debug(fs_info,
566                 "search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
567                  ref->root_id, level, ref->count, ret,
568                  ref->key_for_search.objectid, ref->key_for_search.type,
569                  ref->key_for_search.offset);
570         if (ret < 0)
571                 goto out;
572
573         eb = path->nodes[level];
574         while (!eb) {
575                 if (WARN_ON(!level)) {
576                         ret = 1;
577                         goto out;
578                 }
579                 level--;
580                 eb = path->nodes[level];
581         }
582
583         ret = add_all_parents(root, path, parents, ref, level, time_seq,
584                               extent_item_pos, total_refs);
585 out:
586         path->lowest_level = 0;
587         btrfs_release_path(path);
588         return ret;
589 }
590
591 static struct extent_inode_elem *
592 unode_aux_to_inode_list(struct ulist_node *node)
593 {
594         if (!node)
595                 return NULL;
596         return (struct extent_inode_elem *)(uintptr_t)node->aux;
597 }
598
599 /*
600  * We maintain three seperate rbtrees: one for direct refs, one for
601  * indirect refs which have a key, and one for indirect refs which do not
602  * have a key. Each tree does merge on insertion.
603  *
604  * Once all of the references are located, we iterate over the tree of
605  * indirect refs with missing keys. An appropriate key is located and
606  * the ref is moved onto the tree for indirect refs. After all missing
607  * keys are thus located, we iterate over the indirect ref tree, resolve
608  * each reference, and then insert the resolved reference onto the
609  * direct tree (merging there too).
610  *
611  * New backrefs (i.e., for parent nodes) are added to the appropriate
612  * rbtree as they are encountered. The new backrefs are subsequently
613  * resolved as above.
614  */
615 static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
616                                  struct btrfs_path *path, u64 time_seq,
617                                  struct preftrees *preftrees,
618                                  const u64 *extent_item_pos, u64 total_refs,
619                                  struct share_check *sc)
620 {
621         int err;
622         int ret = 0;
623         struct ulist *parents;
624         struct ulist_node *node;
625         struct ulist_iterator uiter;
626         struct rb_node *rnode;
627
628         parents = ulist_alloc(GFP_NOFS);
629         if (!parents)
630                 return -ENOMEM;
631
632         /*
633          * We could trade memory usage for performance here by iterating
634          * the tree, allocating new refs for each insertion, and then
635          * freeing the entire indirect tree when we're done.  In some test
636          * cases, the tree can grow quite large (~200k objects).
637          */
638         while ((rnode = rb_first(&preftrees->indirect.root))) {
639                 struct prelim_ref *ref;
640
641                 ref = rb_entry(rnode, struct prelim_ref, rbnode);
642                 if (WARN(ref->parent,
643                          "BUG: direct ref found in indirect tree")) {
644                         ret = -EINVAL;
645                         goto out;
646                 }
647
648                 rb_erase(&ref->rbnode, &preftrees->indirect.root);
649                 preftrees->indirect.count--;
650
651                 if (ref->count == 0) {
652                         free_pref(ref);
653                         continue;
654                 }
655
656                 if (sc && sc->root_objectid &&
657                     ref->root_id != sc->root_objectid) {
658                         free_pref(ref);
659                         ret = BACKREF_FOUND_SHARED;
660                         goto out;
661                 }
662                 err = resolve_indirect_ref(fs_info, path, time_seq, ref,
663                                            parents, extent_item_pos,
664                                            total_refs);
665                 /*
666                  * we can only tolerate ENOENT,otherwise,we should catch error
667                  * and return directly.
668                  */
669                 if (err == -ENOENT) {
670                         prelim_ref_insert(fs_info, &preftrees->direct, ref,
671                                           NULL);
672                         continue;
673                 } else if (err) {
674                         free_pref(ref);
675                         ret = err;
676                         goto out;
677                 }
678
679                 /* we put the first parent into the ref at hand */
680                 ULIST_ITER_INIT(&uiter);
681                 node = ulist_next(parents, &uiter);
682                 ref->parent = node ? node->val : 0;
683                 ref->inode_list = unode_aux_to_inode_list(node);
684
685                 /* Add a prelim_ref(s) for any other parent(s). */
686                 while ((node = ulist_next(parents, &uiter))) {
687                         struct prelim_ref *new_ref;
688
689                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
690                                                    GFP_NOFS);
691                         if (!new_ref) {
692                                 free_pref(ref);
693                                 ret = -ENOMEM;
694                                 goto out;
695                         }
696                         memcpy(new_ref, ref, sizeof(*ref));
697                         new_ref->parent = node->val;
698                         new_ref->inode_list = unode_aux_to_inode_list(node);
699                         prelim_ref_insert(fs_info, &preftrees->direct,
700                                           new_ref, NULL);
701                 }
702
703                 /*
704                  * Now it's a direct ref, put it in the the direct tree. We must
705                  * do this last because the ref could be merged/freed here.
706                  */
707                 prelim_ref_insert(fs_info, &preftrees->direct, ref, NULL);
708
709                 ulist_reinit(parents);
710                 cond_resched();
711         }
712 out:
713         ulist_free(parents);
714         return ret;
715 }
716
717 /*
718  * read tree blocks and add keys where required.
719  */
720 static int add_missing_keys(struct btrfs_fs_info *fs_info,
721                             struct preftrees *preftrees)
722 {
723         struct prelim_ref *ref;
724         struct extent_buffer *eb;
725         struct preftree *tree = &preftrees->indirect_missing_keys;
726         struct rb_node *node;
727
728         while ((node = rb_first(&tree->root))) {
729                 ref = rb_entry(node, struct prelim_ref, rbnode);
730                 rb_erase(node, &tree->root);
731
732                 BUG_ON(ref->parent);    /* should not be a direct ref */
733                 BUG_ON(ref->key_for_search.type);
734                 BUG_ON(!ref->wanted_disk_byte);
735
736                 eb = read_tree_block(fs_info, ref->wanted_disk_byte, 0);
737                 if (IS_ERR(eb)) {
738                         free_pref(ref);
739                         return PTR_ERR(eb);
740                 } else if (!extent_buffer_uptodate(eb)) {
741                         free_pref(ref);
742                         free_extent_buffer(eb);
743                         return -EIO;
744                 }
745                 btrfs_tree_read_lock(eb);
746                 if (btrfs_header_level(eb) == 0)
747                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
748                 else
749                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
750                 btrfs_tree_read_unlock(eb);
751                 free_extent_buffer(eb);
752                 prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
753                 cond_resched();
754         }
755         return 0;
756 }
757
758 /*
759  * add all currently queued delayed refs from this head whose seq nr is
760  * smaller or equal that seq to the list
761  */
762 static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
763                             struct btrfs_delayed_ref_head *head, u64 seq,
764                             struct preftrees *preftrees, u64 *total_refs,
765                             struct share_check *sc)
766 {
767         struct btrfs_delayed_ref_node *node;
768         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
769         struct btrfs_key key;
770         struct btrfs_key tmp_op_key;
771         struct btrfs_key *op_key = NULL;
772         int count;
773         int ret = 0;
774
775         if (extent_op && extent_op->update_key) {
776                 btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
777                 op_key = &tmp_op_key;
778         }
779
780         spin_lock(&head->lock);
781         list_for_each_entry(node, &head->ref_list, list) {
782                 if (node->seq > seq)
783                         continue;
784
785                 switch (node->action) {
786                 case BTRFS_ADD_DELAYED_EXTENT:
787                 case BTRFS_UPDATE_DELAYED_HEAD:
788                         WARN_ON(1);
789                         continue;
790                 case BTRFS_ADD_DELAYED_REF:
791                         count = node->ref_mod;
792                         break;
793                 case BTRFS_DROP_DELAYED_REF:
794                         count = node->ref_mod * -1;
795                         break;
796                 default:
797                         BUG_ON(1);
798                 }
799                 *total_refs += count;
800                 switch (node->type) {
801                 case BTRFS_TREE_BLOCK_REF_KEY: {
802                         /* NORMAL INDIRECT METADATA backref */
803                         struct btrfs_delayed_tree_ref *ref;
804
805                         ref = btrfs_delayed_node_to_tree_ref(node);
806                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
807                                                &tmp_op_key, ref->level + 1,
808                                                node->bytenr, count, sc,
809                                                GFP_ATOMIC);
810                         break;
811                 }
812                 case BTRFS_SHARED_BLOCK_REF_KEY: {
813                         /* SHARED DIRECT METADATA backref */
814                         struct btrfs_delayed_tree_ref *ref;
815
816                         ref = btrfs_delayed_node_to_tree_ref(node);
817
818                         ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
819                                              ref->parent, node->bytenr, count,
820                                              sc, GFP_ATOMIC);
821                         break;
822                 }
823                 case BTRFS_EXTENT_DATA_REF_KEY: {
824                         /* NORMAL INDIRECT DATA backref */
825                         struct btrfs_delayed_data_ref *ref;
826                         ref = btrfs_delayed_node_to_data_ref(node);
827
828                         key.objectid = ref->objectid;
829                         key.type = BTRFS_EXTENT_DATA_KEY;
830                         key.offset = ref->offset;
831
832                         /*
833                          * Found a inum that doesn't match our known inum, we
834                          * know it's shared.
835                          */
836                         if (sc && sc->inum && ref->objectid != sc->inum) {
837                                 ret = BACKREF_FOUND_SHARED;
838                                 goto out;
839                         }
840
841                         ret = add_indirect_ref(fs_info, preftrees, ref->root,
842                                                &key, 0, node->bytenr, count, sc,
843                                                GFP_ATOMIC);
844                         break;
845                 }
846                 case BTRFS_SHARED_DATA_REF_KEY: {
847                         /* SHARED DIRECT FULL backref */
848                         struct btrfs_delayed_data_ref *ref;
849
850                         ref = btrfs_delayed_node_to_data_ref(node);
851
852                         ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
853                                              node->bytenr, count, sc,
854                                              GFP_ATOMIC);
855                         break;
856                 }
857                 default:
858                         WARN_ON(1);
859                 }
860                 /*
861                  * We must ignore BACKREF_FOUND_SHARED until all delayed
862                  * refs have been checked.
863                  */
864                 if (ret && (ret != BACKREF_FOUND_SHARED))
865                         break;
866         }
867         if (!ret)
868                 ret = extent_is_shared(sc);
869 out:
870         spin_unlock(&head->lock);
871         return ret;
872 }
873
874 /*
875  * add all inline backrefs for bytenr to the list
876  *
877  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
878  */
879 static int add_inline_refs(const struct btrfs_fs_info *fs_info,
880                            struct btrfs_path *path, u64 bytenr,
881                            int *info_level, struct preftrees *preftrees,
882                            u64 *total_refs, struct share_check *sc)
883 {
884         int ret = 0;
885         int slot;
886         struct extent_buffer *leaf;
887         struct btrfs_key key;
888         struct btrfs_key found_key;
889         unsigned long ptr;
890         unsigned long end;
891         struct btrfs_extent_item *ei;
892         u64 flags;
893         u64 item_size;
894
895         /*
896          * enumerate all inline refs
897          */
898         leaf = path->nodes[0];
899         slot = path->slots[0];
900
901         item_size = btrfs_item_size_nr(leaf, slot);
902         BUG_ON(item_size < sizeof(*ei));
903
904         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
905         flags = btrfs_extent_flags(leaf, ei);
906         *total_refs += btrfs_extent_refs(leaf, ei);
907         btrfs_item_key_to_cpu(leaf, &found_key, slot);
908
909         ptr = (unsigned long)(ei + 1);
910         end = (unsigned long)ei + item_size;
911
912         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
913             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
914                 struct btrfs_tree_block_info *info;
915
916                 info = (struct btrfs_tree_block_info *)ptr;
917                 *info_level = btrfs_tree_block_level(leaf, info);
918                 ptr += sizeof(struct btrfs_tree_block_info);
919                 BUG_ON(ptr > end);
920         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
921                 *info_level = found_key.offset;
922         } else {
923                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
924         }
925
926         while (ptr < end) {
927                 struct btrfs_extent_inline_ref *iref;
928                 u64 offset;
929                 int type;
930
931                 iref = (struct btrfs_extent_inline_ref *)ptr;
932                 type = btrfs_get_extent_inline_ref_type(leaf, iref,
933                                                         BTRFS_REF_TYPE_ANY);
934                 if (type == BTRFS_REF_TYPE_INVALID)
935                         return -EINVAL;
936
937                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
938
939                 switch (type) {
940                 case BTRFS_SHARED_BLOCK_REF_KEY:
941                         ret = add_direct_ref(fs_info, preftrees,
942                                              *info_level + 1, offset,
943                                              bytenr, 1, NULL, GFP_NOFS);
944                         break;
945                 case BTRFS_SHARED_DATA_REF_KEY: {
946                         struct btrfs_shared_data_ref *sdref;
947                         int count;
948
949                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
950                         count = btrfs_shared_data_ref_count(leaf, sdref);
951
952                         ret = add_direct_ref(fs_info, preftrees, 0, offset,
953                                              bytenr, count, sc, GFP_NOFS);
954                         break;
955                 }
956                 case BTRFS_TREE_BLOCK_REF_KEY:
957                         ret = add_indirect_ref(fs_info, preftrees, offset,
958                                                NULL, *info_level + 1,
959                                                bytenr, 1, NULL, GFP_NOFS);
960                         break;
961                 case BTRFS_EXTENT_DATA_REF_KEY: {
962                         struct btrfs_extent_data_ref *dref;
963                         int count;
964                         u64 root;
965
966                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
967                         count = btrfs_extent_data_ref_count(leaf, dref);
968                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
969                                                                       dref);
970                         key.type = BTRFS_EXTENT_DATA_KEY;
971                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
972
973                         if (sc && sc->inum && key.objectid != sc->inum) {
974                                 ret = BACKREF_FOUND_SHARED;
975                                 break;
976                         }
977
978                         root = btrfs_extent_data_ref_root(leaf, dref);
979
980                         ret = add_indirect_ref(fs_info, preftrees, root,
981                                                &key, 0, bytenr, count,
982                                                sc, GFP_NOFS);
983                         break;
984                 }
985                 default:
986                         WARN_ON(1);
987                 }
988                 if (ret)
989                         return ret;
990                 ptr += btrfs_extent_inline_ref_size(type);
991         }
992
993         return 0;
994 }
995
996 /*
997  * add all non-inline backrefs for bytenr to the list
998  *
999  * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
1000  */
1001 static int add_keyed_refs(struct btrfs_fs_info *fs_info,
1002                           struct btrfs_path *path, u64 bytenr,
1003                           int info_level, struct preftrees *preftrees,
1004                           struct share_check *sc)
1005 {
1006         struct btrfs_root *extent_root = fs_info->extent_root;
1007         int ret;
1008         int slot;
1009         struct extent_buffer *leaf;
1010         struct btrfs_key key;
1011
1012         while (1) {
1013                 ret = btrfs_next_item(extent_root, path);
1014                 if (ret < 0)
1015                         break;
1016                 if (ret) {
1017                         ret = 0;
1018                         break;
1019                 }
1020
1021                 slot = path->slots[0];
1022                 leaf = path->nodes[0];
1023                 btrfs_item_key_to_cpu(leaf, &key, slot);
1024
1025                 if (key.objectid != bytenr)
1026                         break;
1027                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
1028                         continue;
1029                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
1030                         break;
1031
1032                 switch (key.type) {
1033                 case BTRFS_SHARED_BLOCK_REF_KEY:
1034                         /* SHARED DIRECT METADATA backref */
1035                         ret = add_direct_ref(fs_info, preftrees,
1036                                              info_level + 1, key.offset,
1037                                              bytenr, 1, NULL, GFP_NOFS);
1038                         break;
1039                 case BTRFS_SHARED_DATA_REF_KEY: {
1040                         /* SHARED DIRECT FULL backref */
1041                         struct btrfs_shared_data_ref *sdref;
1042                         int count;
1043
1044                         sdref = btrfs_item_ptr(leaf, slot,
1045                                               struct btrfs_shared_data_ref);
1046                         count = btrfs_shared_data_ref_count(leaf, sdref);
1047                         ret = add_direct_ref(fs_info, preftrees, 0,
1048                                              key.offset, bytenr, count,
1049                                              sc, GFP_NOFS);
1050                         break;
1051                 }
1052                 case BTRFS_TREE_BLOCK_REF_KEY:
1053                         /* NORMAL INDIRECT METADATA backref */
1054                         ret = add_indirect_ref(fs_info, preftrees, key.offset,
1055                                                NULL, info_level + 1, bytenr,
1056                                                1, NULL, GFP_NOFS);
1057                         break;
1058                 case BTRFS_EXTENT_DATA_REF_KEY: {
1059                         /* NORMAL INDIRECT DATA backref */
1060                         struct btrfs_extent_data_ref *dref;
1061                         int count;
1062                         u64 root;
1063
1064                         dref = btrfs_item_ptr(leaf, slot,
1065                                               struct btrfs_extent_data_ref);
1066                         count = btrfs_extent_data_ref_count(leaf, dref);
1067                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
1068                                                                       dref);
1069                         key.type = BTRFS_EXTENT_DATA_KEY;
1070                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
1071
1072                         if (sc && sc->inum && key.objectid != sc->inum) {
1073                                 ret = BACKREF_FOUND_SHARED;
1074                                 break;
1075                         }
1076
1077                         root = btrfs_extent_data_ref_root(leaf, dref);
1078                         ret = add_indirect_ref(fs_info, preftrees, root,
1079                                                &key, 0, bytenr, count,
1080                                                sc, GFP_NOFS);
1081                         break;
1082                 }
1083                 default:
1084                         WARN_ON(1);
1085                 }
1086                 if (ret)
1087                         return ret;
1088
1089         }
1090
1091         return ret;
1092 }
1093
1094 /*
1095  * this adds all existing backrefs (inline backrefs, backrefs and delayed
1096  * refs) for the given bytenr to the refs list, merges duplicates and resolves
1097  * indirect refs to their parent bytenr.
1098  * When roots are found, they're added to the roots list
1099  *
1100  * If time_seq is set to SEQ_LAST, it will not search delayed_refs, and behave
1101  * much like trans == NULL case, the difference only lies in it will not
1102  * commit root.
1103  * The special case is for qgroup to search roots in commit_transaction().
1104  *
1105  * @sc - if !NULL, then immediately return BACKREF_FOUND_SHARED when a
1106  * shared extent is detected.
1107  *
1108  * Otherwise this returns 0 for success and <0 for an error.
1109  *
1110  * FIXME some caching might speed things up
1111  */
1112 static int find_parent_nodes(struct btrfs_trans_handle *trans,
1113                              struct btrfs_fs_info *fs_info, u64 bytenr,
1114                              u64 time_seq, struct ulist *refs,
1115                              struct ulist *roots, const u64 *extent_item_pos,
1116                              struct share_check *sc)
1117 {
1118         struct btrfs_key key;
1119         struct btrfs_path *path;
1120         struct btrfs_delayed_ref_root *delayed_refs = NULL;
1121         struct btrfs_delayed_ref_head *head;
1122         int info_level = 0;
1123         int ret;
1124         struct prelim_ref *ref;
1125         struct rb_node *node;
1126         struct extent_inode_elem *eie = NULL;
1127         /* total of both direct AND indirect refs! */
1128         u64 total_refs = 0;
1129         struct preftrees preftrees = {
1130                 .direct = PREFTREE_INIT,
1131                 .indirect = PREFTREE_INIT,
1132                 .indirect_missing_keys = PREFTREE_INIT
1133         };
1134
1135         key.objectid = bytenr;
1136         key.offset = (u64)-1;
1137         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1138                 key.type = BTRFS_METADATA_ITEM_KEY;
1139         else
1140                 key.type = BTRFS_EXTENT_ITEM_KEY;
1141
1142         path = btrfs_alloc_path();
1143         if (!path)
1144                 return -ENOMEM;
1145         if (!trans) {
1146                 path->search_commit_root = 1;
1147                 path->skip_locking = 1;
1148         }
1149
1150         if (time_seq == SEQ_LAST)
1151                 path->skip_locking = 1;
1152
1153         /*
1154          * grab both a lock on the path and a lock on the delayed ref head.
1155          * We need both to get a consistent picture of how the refs look
1156          * at a specified point in time
1157          */
1158 again:
1159         head = NULL;
1160
1161         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
1162         if (ret < 0)
1163                 goto out;
1164         BUG_ON(ret == 0);
1165
1166 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
1167         if (trans && likely(trans->type != __TRANS_DUMMY) &&
1168             time_seq != SEQ_LAST) {
1169 #else
1170         if (trans && time_seq != SEQ_LAST) {
1171 #endif
1172                 /*
1173                  * look if there are updates for this ref queued and lock the
1174                  * head
1175                  */
1176                 delayed_refs = &trans->transaction->delayed_refs;
1177                 spin_lock(&delayed_refs->lock);
1178                 head = btrfs_find_delayed_ref_head(delayed_refs, bytenr);
1179                 if (head) {
1180                         if (!mutex_trylock(&head->mutex)) {
1181                                 refcount_inc(&head->node.refs);
1182                                 spin_unlock(&delayed_refs->lock);
1183
1184                                 btrfs_release_path(path);
1185
1186                                 /*
1187                                  * Mutex was contended, block until it's
1188                                  * released and try again
1189                                  */
1190                                 mutex_lock(&head->mutex);
1191                                 mutex_unlock(&head->mutex);
1192                                 btrfs_put_delayed_ref(&head->node);
1193                                 goto again;
1194                         }
1195                         spin_unlock(&delayed_refs->lock);
1196                         ret = add_delayed_refs(fs_info, head, time_seq,
1197                                                &preftrees, &total_refs, sc);
1198                         mutex_unlock(&head->mutex);
1199                         if (ret)
1200                                 goto out;
1201                 } else {
1202                         spin_unlock(&delayed_refs->lock);
1203                 }
1204         }
1205
1206         if (path->slots[0]) {
1207                 struct extent_buffer *leaf;
1208                 int slot;
1209
1210                 path->slots[0]--;
1211                 leaf = path->nodes[0];
1212                 slot = path->slots[0];
1213                 btrfs_item_key_to_cpu(leaf, &key, slot);
1214                 if (key.objectid == bytenr &&
1215                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
1216                      key.type == BTRFS_METADATA_ITEM_KEY)) {
1217                         ret = add_inline_refs(fs_info, path, bytenr,
1218                                               &info_level, &preftrees,
1219                                               &total_refs, sc);
1220                         if (ret)
1221                                 goto out;
1222                         ret = add_keyed_refs(fs_info, path, bytenr, info_level,
1223                                              &preftrees, sc);
1224                         if (ret)
1225                                 goto out;
1226                 }
1227         }
1228
1229         btrfs_release_path(path);
1230
1231         ret = add_missing_keys(fs_info, &preftrees);
1232         if (ret)
1233                 goto out;
1234
1235         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root));
1236
1237         ret = resolve_indirect_refs(fs_info, path, time_seq, &preftrees,
1238                                     extent_item_pos, total_refs, sc);
1239         if (ret)
1240                 goto out;
1241
1242         WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root));
1243
1244         /*
1245          * This walks the tree of merged and resolved refs. Tree blocks are
1246          * read in as needed. Unique entries are added to the ulist, and
1247          * the list of found roots is updated.
1248          *
1249          * We release the entire tree in one go before returning.
1250          */
1251         node = rb_first(&preftrees.direct.root);
1252         while (node) {
1253                 ref = rb_entry(node, struct prelim_ref, rbnode);
1254                 node = rb_next(&ref->rbnode);
1255                 WARN_ON(ref->count < 0);
1256                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1257                         if (sc && sc->root_objectid &&
1258                             ref->root_id != sc->root_objectid) {
1259                                 ret = BACKREF_FOUND_SHARED;
1260                                 goto out;
1261                         }
1262
1263                         /* no parent == root of tree */
1264                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1265                         if (ret < 0)
1266                                 goto out;
1267                 }
1268                 if (ref->count && ref->parent) {
1269                         if (extent_item_pos && !ref->inode_list &&
1270                             ref->level == 0) {
1271                                 struct extent_buffer *eb;
1272
1273                                 eb = read_tree_block(fs_info, ref->parent, 0);
1274                                 if (IS_ERR(eb)) {
1275                                         ret = PTR_ERR(eb);
1276                                         goto out;
1277                                 } else if (!extent_buffer_uptodate(eb)) {
1278                                         free_extent_buffer(eb);
1279                                         ret = -EIO;
1280                                         goto out;
1281                                 }
1282                                 btrfs_tree_read_lock(eb);
1283                                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1284                                 ret = find_extent_in_eb(eb, bytenr,
1285                                                         *extent_item_pos, &eie);
1286                                 btrfs_tree_read_unlock_blocking(eb);
1287                                 free_extent_buffer(eb);
1288                                 if (ret < 0)
1289                                         goto out;
1290                                 ref->inode_list = eie;
1291                         }
1292                         ret = ulist_add_merge_ptr(refs, ref->parent,
1293                                                   ref->inode_list,
1294                                                   (void **)&eie, GFP_NOFS);
1295                         if (ret < 0)
1296                                 goto out;
1297                         if (!ret && extent_item_pos) {
1298                                 /*
1299                                  * we've recorded that parent, so we must extend
1300                                  * its inode list here
1301                                  */
1302                                 BUG_ON(!eie);
1303                                 while (eie->next)
1304                                         eie = eie->next;
1305                                 eie->next = ref->inode_list;
1306                         }
1307                         eie = NULL;
1308                 }
1309                 cond_resched();
1310         }
1311
1312 out:
1313         btrfs_free_path(path);
1314
1315         prelim_release(&preftrees.direct);
1316         prelim_release(&preftrees.indirect);
1317         prelim_release(&preftrees.indirect_missing_keys);
1318
1319         if (ret < 0)
1320                 free_inode_elem_list(eie);
1321         return ret;
1322 }
1323
1324 static void free_leaf_list(struct ulist *blocks)
1325 {
1326         struct ulist_node *node = NULL;
1327         struct extent_inode_elem *eie;
1328         struct ulist_iterator uiter;
1329
1330         ULIST_ITER_INIT(&uiter);
1331         while ((node = ulist_next(blocks, &uiter))) {
1332                 if (!node->aux)
1333                         continue;
1334                 eie = unode_aux_to_inode_list(node);
1335                 free_inode_elem_list(eie);
1336                 node->aux = 0;
1337         }
1338
1339         ulist_free(blocks);
1340 }
1341
1342 /*
1343  * Finds all leafs with a reference to the specified combination of bytenr and
1344  * offset. key_list_head will point to a list of corresponding keys (caller must
1345  * free each list element). The leafs will be stored in the leafs ulist, which
1346  * must be freed with ulist_free.
1347  *
1348  * returns 0 on success, <0 on error
1349  */
1350 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1351                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1352                                 u64 time_seq, struct ulist **leafs,
1353                                 const u64 *extent_item_pos)
1354 {
1355         int ret;
1356
1357         *leafs = ulist_alloc(GFP_NOFS);
1358         if (!*leafs)
1359                 return -ENOMEM;
1360
1361         ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1362                                 *leafs, NULL, extent_item_pos, NULL);
1363         if (ret < 0 && ret != -ENOENT) {
1364                 free_leaf_list(*leafs);
1365                 return ret;
1366         }
1367
1368         return 0;
1369 }
1370
1371 /*
1372  * walk all backrefs for a given extent to find all roots that reference this
1373  * extent. Walking a backref means finding all extents that reference this
1374  * extent and in turn walk the backrefs of those, too. Naturally this is a
1375  * recursive process, but here it is implemented in an iterative fashion: We
1376  * find all referencing extents for the extent in question and put them on a
1377  * list. In turn, we find all referencing extents for those, further appending
1378  * to the list. The way we iterate the list allows adding more elements after
1379  * the current while iterating. The process stops when we reach the end of the
1380  * list. Found roots are added to the roots list.
1381  *
1382  * returns 0 on success, < 0 on error.
1383  */
1384 static int btrfs_find_all_roots_safe(struct btrfs_trans_handle *trans,
1385                                      struct btrfs_fs_info *fs_info, u64 bytenr,
1386                                      u64 time_seq, struct ulist **roots)
1387 {
1388         struct ulist *tmp;
1389         struct ulist_node *node = NULL;
1390         struct ulist_iterator uiter;
1391         int ret;
1392
1393         tmp = ulist_alloc(GFP_NOFS);
1394         if (!tmp)
1395                 return -ENOMEM;
1396         *roots = ulist_alloc(GFP_NOFS);
1397         if (!*roots) {
1398                 ulist_free(tmp);
1399                 return -ENOMEM;
1400         }
1401
1402         ULIST_ITER_INIT(&uiter);
1403         while (1) {
1404                 ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
1405                                         tmp, *roots, NULL, NULL);
1406                 if (ret < 0 && ret != -ENOENT) {
1407                         ulist_free(tmp);
1408                         ulist_free(*roots);
1409                         return ret;
1410                 }
1411                 node = ulist_next(tmp, &uiter);
1412                 if (!node)
1413                         break;
1414                 bytenr = node->val;
1415                 cond_resched();
1416         }
1417
1418         ulist_free(tmp);
1419         return 0;
1420 }
1421
1422 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1423                          struct btrfs_fs_info *fs_info, u64 bytenr,
1424                          u64 time_seq, struct ulist **roots)
1425 {
1426         int ret;
1427
1428         if (!trans)
1429                 down_read(&fs_info->commit_root_sem);
1430         ret = btrfs_find_all_roots_safe(trans, fs_info, bytenr,
1431                                         time_seq, roots);
1432         if (!trans)
1433                 up_read(&fs_info->commit_root_sem);
1434         return ret;
1435 }
1436
1437 /**
1438  * btrfs_check_shared - tell us whether an extent is shared
1439  *
1440  * btrfs_check_shared uses the backref walking code but will short
1441  * circuit as soon as it finds a root or inode that doesn't match the
1442  * one passed in. This provides a significant performance benefit for
1443  * callers (such as fiemap) which want to know whether the extent is
1444  * shared but do not need a ref count.
1445  *
1446  * This attempts to allocate a transaction in order to account for
1447  * delayed refs, but continues on even when the alloc fails.
1448  *
1449  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1450  */
1451 int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr)
1452 {
1453         struct btrfs_fs_info *fs_info = root->fs_info;
1454         struct btrfs_trans_handle *trans;
1455         struct ulist *tmp = NULL;
1456         struct ulist *roots = NULL;
1457         struct ulist_iterator uiter;
1458         struct ulist_node *node;
1459         struct seq_list elem = SEQ_LIST_INIT(elem);
1460         int ret = 0;
1461         struct share_check shared = {
1462                 .root_objectid = root->objectid,
1463                 .inum = inum,
1464                 .share_count = 0,
1465         };
1466
1467         tmp = ulist_alloc(GFP_NOFS);
1468         roots = ulist_alloc(GFP_NOFS);
1469         if (!tmp || !roots) {
1470                 ulist_free(tmp);
1471                 ulist_free(roots);
1472                 return -ENOMEM;
1473         }
1474
1475         trans = btrfs_join_transaction(root);
1476         if (IS_ERR(trans)) {
1477                 trans = NULL;
1478                 down_read(&fs_info->commit_root_sem);
1479         } else {
1480                 btrfs_get_tree_mod_seq(fs_info, &elem);
1481         }
1482
1483         ULIST_ITER_INIT(&uiter);
1484         while (1) {
1485                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1486                                         roots, NULL, &shared);
1487                 if (ret == BACKREF_FOUND_SHARED) {
1488                         /* this is the only condition under which we return 1 */
1489                         ret = 1;
1490                         break;
1491                 }
1492                 if (ret < 0 && ret != -ENOENT)
1493                         break;
1494                 ret = 0;
1495                 node = ulist_next(tmp, &uiter);
1496                 if (!node)
1497                         break;
1498                 bytenr = node->val;
1499                 cond_resched();
1500         }
1501
1502         if (trans) {
1503                 btrfs_put_tree_mod_seq(fs_info, &elem);
1504                 btrfs_end_transaction(trans);
1505         } else {
1506                 up_read(&fs_info->commit_root_sem);
1507         }
1508         ulist_free(tmp);
1509         ulist_free(roots);
1510         return ret;
1511 }
1512
1513 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1514                           u64 start_off, struct btrfs_path *path,
1515                           struct btrfs_inode_extref **ret_extref,
1516                           u64 *found_off)
1517 {
1518         int ret, slot;
1519         struct btrfs_key key;
1520         struct btrfs_key found_key;
1521         struct btrfs_inode_extref *extref;
1522         const struct extent_buffer *leaf;
1523         unsigned long ptr;
1524
1525         key.objectid = inode_objectid;
1526         key.type = BTRFS_INODE_EXTREF_KEY;
1527         key.offset = start_off;
1528
1529         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1530         if (ret < 0)
1531                 return ret;
1532
1533         while (1) {
1534                 leaf = path->nodes[0];
1535                 slot = path->slots[0];
1536                 if (slot >= btrfs_header_nritems(leaf)) {
1537                         /*
1538                          * If the item at offset is not found,
1539                          * btrfs_search_slot will point us to the slot
1540                          * where it should be inserted. In our case
1541                          * that will be the slot directly before the
1542                          * next INODE_REF_KEY_V2 item. In the case
1543                          * that we're pointing to the last slot in a
1544                          * leaf, we must move one leaf over.
1545                          */
1546                         ret = btrfs_next_leaf(root, path);
1547                         if (ret) {
1548                                 if (ret >= 1)
1549                                         ret = -ENOENT;
1550                                 break;
1551                         }
1552                         continue;
1553                 }
1554
1555                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1556
1557                 /*
1558                  * Check that we're still looking at an extended ref key for
1559                  * this particular objectid. If we have different
1560                  * objectid or type then there are no more to be found
1561                  * in the tree and we can exit.
1562                  */
1563                 ret = -ENOENT;
1564                 if (found_key.objectid != inode_objectid)
1565                         break;
1566                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1567                         break;
1568
1569                 ret = 0;
1570                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1571                 extref = (struct btrfs_inode_extref *)ptr;
1572                 *ret_extref = extref;
1573                 if (found_off)
1574                         *found_off = found_key.offset;
1575                 break;
1576         }
1577
1578         return ret;
1579 }
1580
1581 /*
1582  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1583  * Elements of the path are separated by '/' and the path is guaranteed to be
1584  * 0-terminated. the path is only given within the current file system.
1585  * Therefore, it never starts with a '/'. the caller is responsible to provide
1586  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1587  * the start point of the resulting string is returned. this pointer is within
1588  * dest, normally.
1589  * in case the path buffer would overflow, the pointer is decremented further
1590  * as if output was written to the buffer, though no more output is actually
1591  * generated. that way, the caller can determine how much space would be
1592  * required for the path to fit into the buffer. in that case, the returned
1593  * value will be smaller than dest. callers must check this!
1594  */
1595 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1596                         u32 name_len, unsigned long name_off,
1597                         struct extent_buffer *eb_in, u64 parent,
1598                         char *dest, u32 size)
1599 {
1600         int slot;
1601         u64 next_inum;
1602         int ret;
1603         s64 bytes_left = ((s64)size) - 1;
1604         struct extent_buffer *eb = eb_in;
1605         struct btrfs_key found_key;
1606         int leave_spinning = path->leave_spinning;
1607         struct btrfs_inode_ref *iref;
1608
1609         if (bytes_left >= 0)
1610                 dest[bytes_left] = '\0';
1611
1612         path->leave_spinning = 1;
1613         while (1) {
1614                 bytes_left -= name_len;
1615                 if (bytes_left >= 0)
1616                         read_extent_buffer(eb, dest + bytes_left,
1617                                            name_off, name_len);
1618                 if (eb != eb_in) {
1619                         if (!path->skip_locking)
1620                                 btrfs_tree_read_unlock_blocking(eb);
1621                         free_extent_buffer(eb);
1622                 }
1623                 ret = btrfs_find_item(fs_root, path, parent, 0,
1624                                 BTRFS_INODE_REF_KEY, &found_key);
1625                 if (ret > 0)
1626                         ret = -ENOENT;
1627                 if (ret)
1628                         break;
1629
1630                 next_inum = found_key.offset;
1631
1632                 /* regular exit ahead */
1633                 if (parent == next_inum)
1634                         break;
1635
1636                 slot = path->slots[0];
1637                 eb = path->nodes[0];
1638                 /* make sure we can use eb after releasing the path */
1639                 if (eb != eb_in) {
1640                         if (!path->skip_locking)
1641                                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1642                         path->nodes[0] = NULL;
1643                         path->locks[0] = 0;
1644                 }
1645                 btrfs_release_path(path);
1646                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1647
1648                 name_len = btrfs_inode_ref_name_len(eb, iref);
1649                 name_off = (unsigned long)(iref + 1);
1650
1651                 parent = next_inum;
1652                 --bytes_left;
1653                 if (bytes_left >= 0)
1654                         dest[bytes_left] = '/';
1655         }
1656
1657         btrfs_release_path(path);
1658         path->leave_spinning = leave_spinning;
1659
1660         if (ret)
1661                 return ERR_PTR(ret);
1662
1663         return dest + bytes_left;
1664 }
1665
1666 /*
1667  * this makes the path point to (logical EXTENT_ITEM *)
1668  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1669  * tree blocks and <0 on error.
1670  */
1671 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1672                         struct btrfs_path *path, struct btrfs_key *found_key,
1673                         u64 *flags_ret)
1674 {
1675         int ret;
1676         u64 flags;
1677         u64 size = 0;
1678         u32 item_size;
1679         const struct extent_buffer *eb;
1680         struct btrfs_extent_item *ei;
1681         struct btrfs_key key;
1682
1683         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1684                 key.type = BTRFS_METADATA_ITEM_KEY;
1685         else
1686                 key.type = BTRFS_EXTENT_ITEM_KEY;
1687         key.objectid = logical;
1688         key.offset = (u64)-1;
1689
1690         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1691         if (ret < 0)
1692                 return ret;
1693
1694         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1695         if (ret) {
1696                 if (ret > 0)
1697                         ret = -ENOENT;
1698                 return ret;
1699         }
1700         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1701         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1702                 size = fs_info->nodesize;
1703         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1704                 size = found_key->offset;
1705
1706         if (found_key->objectid > logical ||
1707             found_key->objectid + size <= logical) {
1708                 btrfs_debug(fs_info,
1709                         "logical %llu is not within any extent", logical);
1710                 return -ENOENT;
1711         }
1712
1713         eb = path->nodes[0];
1714         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1715         BUG_ON(item_size < sizeof(*ei));
1716
1717         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1718         flags = btrfs_extent_flags(eb, ei);
1719
1720         btrfs_debug(fs_info,
1721                 "logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
1722                  logical, logical - found_key->objectid, found_key->objectid,
1723                  found_key->offset, flags, item_size);
1724
1725         WARN_ON(!flags_ret);
1726         if (flags_ret) {
1727                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1728                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1729                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1730                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1731                 else
1732                         BUG_ON(1);
1733                 return 0;
1734         }
1735
1736         return -EIO;
1737 }
1738
1739 /*
1740  * helper function to iterate extent inline refs. ptr must point to a 0 value
1741  * for the first call and may be modified. it is used to track state.
1742  * if more refs exist, 0 is returned and the next call to
1743  * get_extent_inline_ref must pass the modified ptr parameter to get the
1744  * next ref. after the last ref was processed, 1 is returned.
1745  * returns <0 on error
1746  */
1747 static int get_extent_inline_ref(unsigned long *ptr,
1748                                  const struct extent_buffer *eb,
1749                                  const struct btrfs_key *key,
1750                                  const struct btrfs_extent_item *ei,
1751                                  u32 item_size,
1752                                  struct btrfs_extent_inline_ref **out_eiref,
1753                                  int *out_type)
1754 {
1755         unsigned long end;
1756         u64 flags;
1757         struct btrfs_tree_block_info *info;
1758
1759         if (!*ptr) {
1760                 /* first call */
1761                 flags = btrfs_extent_flags(eb, ei);
1762                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1763                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1764                                 /* a skinny metadata extent */
1765                                 *out_eiref =
1766                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1767                         } else {
1768                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1769                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1770                                 *out_eiref =
1771                                    (struct btrfs_extent_inline_ref *)(info + 1);
1772                         }
1773                 } else {
1774                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1775                 }
1776                 *ptr = (unsigned long)*out_eiref;
1777                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1778                         return -ENOENT;
1779         }
1780
1781         end = (unsigned long)ei + item_size;
1782         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1783         *out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
1784                                                      BTRFS_REF_TYPE_ANY);
1785         if (*out_type == BTRFS_REF_TYPE_INVALID)
1786                 return -EINVAL;
1787
1788         *ptr += btrfs_extent_inline_ref_size(*out_type);
1789         WARN_ON(*ptr > end);
1790         if (*ptr == end)
1791                 return 1; /* last */
1792
1793         return 0;
1794 }
1795
1796 /*
1797  * reads the tree block backref for an extent. tree level and root are returned
1798  * through out_level and out_root. ptr must point to a 0 value for the first
1799  * call and may be modified (see get_extent_inline_ref comment).
1800  * returns 0 if data was provided, 1 if there was no more data to provide or
1801  * <0 on error.
1802  */
1803 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1804                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1805                             u32 item_size, u64 *out_root, u8 *out_level)
1806 {
1807         int ret;
1808         int type;
1809         struct btrfs_extent_inline_ref *eiref;
1810
1811         if (*ptr == (unsigned long)-1)
1812                 return 1;
1813
1814         while (1) {
1815                 ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
1816                                               &eiref, &type);
1817                 if (ret < 0)
1818                         return ret;
1819
1820                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1821                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1822                         break;
1823
1824                 if (ret == 1)
1825                         return 1;
1826         }
1827
1828         /* we can treat both ref types equally here */
1829         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1830
1831         if (key->type == BTRFS_EXTENT_ITEM_KEY) {
1832                 struct btrfs_tree_block_info *info;
1833
1834                 info = (struct btrfs_tree_block_info *)(ei + 1);
1835                 *out_level = btrfs_tree_block_level(eb, info);
1836         } else {
1837                 ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
1838                 *out_level = (u8)key->offset;
1839         }
1840
1841         if (ret == 1)
1842                 *ptr = (unsigned long)-1;
1843
1844         return 0;
1845 }
1846
1847 static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
1848                              struct extent_inode_elem *inode_list,
1849                              u64 root, u64 extent_item_objectid,
1850                              iterate_extent_inodes_t *iterate, void *ctx)
1851 {
1852         struct extent_inode_elem *eie;
1853         int ret = 0;
1854
1855         for (eie = inode_list; eie; eie = eie->next) {
1856                 btrfs_debug(fs_info,
1857                             "ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
1858                             extent_item_objectid, eie->inum,
1859                             eie->offset, root);
1860                 ret = iterate(eie->inum, eie->offset, root, ctx);
1861                 if (ret) {
1862                         btrfs_debug(fs_info,
1863                                     "stopping iteration for %llu due to ret=%d",
1864                                     extent_item_objectid, ret);
1865                         break;
1866                 }
1867         }
1868
1869         return ret;
1870 }
1871
1872 /*
1873  * calls iterate() for every inode that references the extent identified by
1874  * the given parameters.
1875  * when the iterator function returns a non-zero value, iteration stops.
1876  */
1877 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1878                                 u64 extent_item_objectid, u64 extent_item_pos,
1879                                 int search_commit_root,
1880                                 iterate_extent_inodes_t *iterate, void *ctx)
1881 {
1882         int ret;
1883         struct btrfs_trans_handle *trans = NULL;
1884         struct ulist *refs = NULL;
1885         struct ulist *roots = NULL;
1886         struct ulist_node *ref_node = NULL;
1887         struct ulist_node *root_node = NULL;
1888         struct seq_list tree_mod_seq_elem = SEQ_LIST_INIT(tree_mod_seq_elem);
1889         struct ulist_iterator ref_uiter;
1890         struct ulist_iterator root_uiter;
1891
1892         btrfs_debug(fs_info, "resolving all inodes for extent %llu",
1893                         extent_item_objectid);
1894
1895         if (!search_commit_root) {
1896                 trans = btrfs_join_transaction(fs_info->extent_root);
1897                 if (IS_ERR(trans))
1898                         return PTR_ERR(trans);
1899                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1900         } else {
1901                 down_read(&fs_info->commit_root_sem);
1902         }
1903
1904         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1905                                    tree_mod_seq_elem.seq, &refs,
1906                                    &extent_item_pos);
1907         if (ret)
1908                 goto out;
1909
1910         ULIST_ITER_INIT(&ref_uiter);
1911         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1912                 ret = btrfs_find_all_roots_safe(trans, fs_info, ref_node->val,
1913                                                 tree_mod_seq_elem.seq, &roots);
1914                 if (ret)
1915                         break;
1916                 ULIST_ITER_INIT(&root_uiter);
1917                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1918                         btrfs_debug(fs_info,
1919                                     "root %llu references leaf %llu, data list %#llx",
1920                                     root_node->val, ref_node->val,
1921                                     ref_node->aux);
1922                         ret = iterate_leaf_refs(fs_info,
1923                                                 (struct extent_inode_elem *)
1924                                                 (uintptr_t)ref_node->aux,
1925                                                 root_node->val,
1926                                                 extent_item_objectid,
1927                                                 iterate, ctx);
1928                 }
1929                 ulist_free(roots);
1930         }
1931
1932         free_leaf_list(refs);
1933 out:
1934         if (!search_commit_root) {
1935                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1936                 btrfs_end_transaction(trans);
1937         } else {
1938                 up_read(&fs_info->commit_root_sem);
1939         }
1940
1941         return ret;
1942 }
1943
1944 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1945                                 struct btrfs_path *path,
1946                                 iterate_extent_inodes_t *iterate, void *ctx)
1947 {
1948         int ret;
1949         u64 extent_item_pos;
1950         u64 flags = 0;
1951         struct btrfs_key found_key;
1952         int search_commit_root = path->search_commit_root;
1953
1954         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1955         btrfs_release_path(path);
1956         if (ret < 0)
1957                 return ret;
1958         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1959                 return -EINVAL;
1960
1961         extent_item_pos = logical - found_key.objectid;
1962         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1963                                         extent_item_pos, search_commit_root,
1964                                         iterate, ctx);
1965
1966         return ret;
1967 }
1968
1969 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1970                               struct extent_buffer *eb, void *ctx);
1971
1972 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1973                               struct btrfs_path *path,
1974                               iterate_irefs_t *iterate, void *ctx)
1975 {
1976         int ret = 0;
1977         int slot;
1978         u32 cur;
1979         u32 len;
1980         u32 name_len;
1981         u64 parent = 0;
1982         int found = 0;
1983         struct extent_buffer *eb;
1984         struct btrfs_item *item;
1985         struct btrfs_inode_ref *iref;
1986         struct btrfs_key found_key;
1987
1988         while (!ret) {
1989                 ret = btrfs_find_item(fs_root, path, inum,
1990                                 parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
1991                                 &found_key);
1992
1993                 if (ret < 0)
1994                         break;
1995                 if (ret) {
1996                         ret = found ? 0 : -ENOENT;
1997                         break;
1998                 }
1999                 ++found;
2000
2001                 parent = found_key.offset;
2002                 slot = path->slots[0];
2003                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2004                 if (!eb) {
2005                         ret = -ENOMEM;
2006                         break;
2007                 }
2008                 extent_buffer_get(eb);
2009                 btrfs_tree_read_lock(eb);
2010                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
2011                 btrfs_release_path(path);
2012
2013                 item = btrfs_item_nr(slot);
2014                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2015
2016                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
2017                         name_len = btrfs_inode_ref_name_len(eb, iref);
2018                         /* path must be released before calling iterate()! */
2019                         btrfs_debug(fs_root->fs_info,
2020                                 "following ref at offset %u for inode %llu in tree %llu",
2021                                 cur, found_key.objectid, fs_root->objectid);
2022                         ret = iterate(parent, name_len,
2023                                       (unsigned long)(iref + 1), eb, ctx);
2024                         if (ret)
2025                                 break;
2026                         len = sizeof(*iref) + name_len;
2027                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
2028                 }
2029                 btrfs_tree_read_unlock_blocking(eb);
2030                 free_extent_buffer(eb);
2031         }
2032
2033         btrfs_release_path(path);
2034
2035         return ret;
2036 }
2037
2038 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
2039                                  struct btrfs_path *path,
2040                                  iterate_irefs_t *iterate, void *ctx)
2041 {
2042         int ret;
2043         int slot;
2044         u64 offset = 0;
2045         u64 parent;
2046         int found = 0;
2047         struct extent_buffer *eb;
2048         struct btrfs_inode_extref *extref;
2049         u32 item_size;
2050         u32 cur_offset;
2051         unsigned long ptr;
2052
2053         while (1) {
2054                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
2055                                             &offset);
2056                 if (ret < 0)
2057                         break;
2058                 if (ret) {
2059                         ret = found ? 0 : -ENOENT;
2060                         break;
2061                 }
2062                 ++found;
2063
2064                 slot = path->slots[0];
2065                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
2066                 if (!eb) {
2067                         ret = -ENOMEM;
2068                         break;
2069                 }
2070                 extent_buffer_get(eb);
2071
2072                 btrfs_tree_read_lock(eb);
2073                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
2074                 btrfs_release_path(path);
2075
2076                 item_size = btrfs_item_size_nr(eb, slot);
2077                 ptr = btrfs_item_ptr_offset(eb, slot);
2078                 cur_offset = 0;
2079
2080                 while (cur_offset < item_size) {
2081                         u32 name_len;
2082
2083                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
2084                         parent = btrfs_inode_extref_parent(eb, extref);
2085                         name_len = btrfs_inode_extref_name_len(eb, extref);
2086                         ret = iterate(parent, name_len,
2087                                       (unsigned long)&extref->name, eb, ctx);
2088                         if (ret)
2089                                 break;
2090
2091                         cur_offset += btrfs_inode_extref_name_len(eb, extref);
2092                         cur_offset += sizeof(*extref);
2093                 }
2094                 btrfs_tree_read_unlock_blocking(eb);
2095                 free_extent_buffer(eb);
2096
2097                 offset++;
2098         }
2099
2100         btrfs_release_path(path);
2101
2102         return ret;
2103 }
2104
2105 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
2106                          struct btrfs_path *path, iterate_irefs_t *iterate,
2107                          void *ctx)
2108 {
2109         int ret;
2110         int found_refs = 0;
2111
2112         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
2113         if (!ret)
2114                 ++found_refs;
2115         else if (ret != -ENOENT)
2116                 return ret;
2117
2118         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
2119         if (ret == -ENOENT && found_refs)
2120                 return 0;
2121
2122         return ret;
2123 }
2124
2125 /*
2126  * returns 0 if the path could be dumped (probably truncated)
2127  * returns <0 in case of an error
2128  */
2129 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2130                          struct extent_buffer *eb, void *ctx)
2131 {
2132         struct inode_fs_paths *ipath = ctx;
2133         char *fspath;
2134         char *fspath_min;
2135         int i = ipath->fspath->elem_cnt;
2136         const int s_ptr = sizeof(char *);
2137         u32 bytes_left;
2138
2139         bytes_left = ipath->fspath->bytes_left > s_ptr ?
2140                                         ipath->fspath->bytes_left - s_ptr : 0;
2141
2142         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
2143         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
2144                                    name_off, eb, inum, fspath_min, bytes_left);
2145         if (IS_ERR(fspath))
2146                 return PTR_ERR(fspath);
2147
2148         if (fspath > fspath_min) {
2149                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
2150                 ++ipath->fspath->elem_cnt;
2151                 ipath->fspath->bytes_left = fspath - fspath_min;
2152         } else {
2153                 ++ipath->fspath->elem_missed;
2154                 ipath->fspath->bytes_missing += fspath_min - fspath;
2155                 ipath->fspath->bytes_left = 0;
2156         }
2157
2158         return 0;
2159 }
2160
2161 /*
2162  * this dumps all file system paths to the inode into the ipath struct, provided
2163  * is has been created large enough. each path is zero-terminated and accessed
2164  * from ipath->fspath->val[i].
2165  * when it returns, there are ipath->fspath->elem_cnt number of paths available
2166  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
2167  * number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
2168  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
2169  * have been needed to return all paths.
2170  */
2171 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
2172 {
2173         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
2174                              inode_to_path, ipath);
2175 }
2176
2177 struct btrfs_data_container *init_data_container(u32 total_bytes)
2178 {
2179         struct btrfs_data_container *data;
2180         size_t alloc_bytes;
2181
2182         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
2183         data = kvmalloc(alloc_bytes, GFP_KERNEL);
2184         if (!data)
2185                 return ERR_PTR(-ENOMEM);
2186
2187         if (total_bytes >= sizeof(*data)) {
2188                 data->bytes_left = total_bytes - sizeof(*data);
2189                 data->bytes_missing = 0;
2190         } else {
2191                 data->bytes_missing = sizeof(*data) - total_bytes;
2192                 data->bytes_left = 0;
2193         }
2194
2195         data->elem_cnt = 0;
2196         data->elem_missed = 0;
2197
2198         return data;
2199 }
2200
2201 /*
2202  * allocates space to return multiple file system paths for an inode.
2203  * total_bytes to allocate are passed, note that space usable for actual path
2204  * information will be total_bytes - sizeof(struct inode_fs_paths).
2205  * the returned pointer must be freed with free_ipath() in the end.
2206  */
2207 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
2208                                         struct btrfs_path *path)
2209 {
2210         struct inode_fs_paths *ifp;
2211         struct btrfs_data_container *fspath;
2212
2213         fspath = init_data_container(total_bytes);
2214         if (IS_ERR(fspath))
2215                 return (void *)fspath;
2216
2217         ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
2218         if (!ifp) {
2219                 kvfree(fspath);
2220                 return ERR_PTR(-ENOMEM);
2221         }
2222
2223         ifp->btrfs_path = path;
2224         ifp->fspath = fspath;
2225         ifp->fs_root = fs_root;
2226
2227         return ifp;
2228 }
2229
2230 void free_ipath(struct inode_fs_paths *ipath)
2231 {
2232         if (!ipath)
2233                 return;
2234         kvfree(ipath->fspath);
2235         kfree(ipath);
2236 }