Btrfs: support root level changes in __resolve_indirect_ref
[linux-3.10.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 "ctree.h"
20 #include "disk-io.h"
21 #include "backref.h"
22 #include "ulist.h"
23 #include "transaction.h"
24 #include "delayed-ref.h"
25 #include "locking.h"
26
27 struct extent_inode_elem {
28         u64 inum;
29         u64 offset;
30         struct extent_inode_elem *next;
31 };
32
33 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
34                                 struct btrfs_file_extent_item *fi,
35                                 u64 extent_item_pos,
36                                 struct extent_inode_elem **eie)
37 {
38         u64 data_offset;
39         u64 data_len;
40         struct extent_inode_elem *e;
41
42         data_offset = btrfs_file_extent_offset(eb, fi);
43         data_len = btrfs_file_extent_num_bytes(eb, fi);
44
45         if (extent_item_pos < data_offset ||
46             extent_item_pos >= data_offset + data_len)
47                 return 1;
48
49         e = kmalloc(sizeof(*e), GFP_NOFS);
50         if (!e)
51                 return -ENOMEM;
52
53         e->next = *eie;
54         e->inum = key->objectid;
55         e->offset = key->offset + (extent_item_pos - data_offset);
56         *eie = e;
57
58         return 0;
59 }
60
61 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
62                                 u64 extent_item_pos,
63                                 struct extent_inode_elem **eie)
64 {
65         u64 disk_byte;
66         struct btrfs_key key;
67         struct btrfs_file_extent_item *fi;
68         int slot;
69         int nritems;
70         int extent_type;
71         int ret;
72
73         /*
74          * from the shared data ref, we only have the leaf but we need
75          * the key. thus, we must look into all items and see that we
76          * find one (some) with a reference to our extent item.
77          */
78         nritems = btrfs_header_nritems(eb);
79         for (slot = 0; slot < nritems; ++slot) {
80                 btrfs_item_key_to_cpu(eb, &key, slot);
81                 if (key.type != BTRFS_EXTENT_DATA_KEY)
82                         continue;
83                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
84                 extent_type = btrfs_file_extent_type(eb, fi);
85                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
86                         continue;
87                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
88                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
89                 if (disk_byte != wanted_disk_byte)
90                         continue;
91
92                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
93                 if (ret < 0)
94                         return ret;
95         }
96
97         return 0;
98 }
99
100 /*
101  * this structure records all encountered refs on the way up to the root
102  */
103 struct __prelim_ref {
104         struct list_head list;
105         u64 root_id;
106         struct btrfs_key key_for_search;
107         int level;
108         int count;
109         struct extent_inode_elem *inode_list;
110         u64 parent;
111         u64 wanted_disk_byte;
112 };
113
114 /*
115  * the rules for all callers of this function are:
116  * - obtaining the parent is the goal
117  * - if you add a key, you must know that it is a correct key
118  * - if you cannot add the parent or a correct key, then we will look into the
119  *   block later to set a correct key
120  *
121  * delayed refs
122  * ============
123  *        backref type | shared | indirect | shared | indirect
124  * information         |   tree |     tree |   data |     data
125  * --------------------+--------+----------+--------+----------
126  *      parent logical |    y   |     -    |    -   |     -
127  *      key to resolve |    -   |     y    |    y   |     y
128  *  tree block logical |    -   |     -    |    -   |     -
129  *  root for resolving |    y   |     y    |    y   |     y
130  *
131  * - column 1:       we've the parent -> done
132  * - column 2, 3, 4: we use the key to find the parent
133  *
134  * on disk refs (inline or keyed)
135  * ==============================
136  *        backref type | shared | indirect | shared | indirect
137  * information         |   tree |     tree |   data |     data
138  * --------------------+--------+----------+--------+----------
139  *      parent logical |    y   |     -    |    y   |     -
140  *      key to resolve |    -   |     -    |    -   |     y
141  *  tree block logical |    y   |     y    |    y   |     y
142  *  root for resolving |    -   |     y    |    y   |     y
143  *
144  * - column 1, 3: we've the parent -> done
145  * - column 2:    we take the first key from the block to find the parent
146  *                (see __add_missing_keys)
147  * - column 4:    we use the key to find the parent
148  *
149  * additional information that's available but not required to find the parent
150  * block might help in merging entries to gain some speed.
151  */
152
153 static int __add_prelim_ref(struct list_head *head, u64 root_id,
154                             struct btrfs_key *key, int level,
155                             u64 parent, u64 wanted_disk_byte, int count)
156 {
157         struct __prelim_ref *ref;
158
159         /* in case we're adding delayed refs, we're holding the refs spinlock */
160         ref = kmalloc(sizeof(*ref), GFP_ATOMIC);
161         if (!ref)
162                 return -ENOMEM;
163
164         ref->root_id = root_id;
165         if (key)
166                 ref->key_for_search = *key;
167         else
168                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
169
170         ref->inode_list = NULL;
171         ref->level = level;
172         ref->count = count;
173         ref->parent = parent;
174         ref->wanted_disk_byte = wanted_disk_byte;
175         list_add_tail(&ref->list, head);
176
177         return 0;
178 }
179
180 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
181                                 struct ulist *parents, int level,
182                                 struct btrfs_key *key_for_search, u64 time_seq,
183                                 u64 wanted_disk_byte,
184                                 const u64 *extent_item_pos)
185 {
186         int ret = 0;
187         int slot;
188         struct extent_buffer *eb;
189         struct btrfs_key key;
190         struct btrfs_file_extent_item *fi;
191         struct extent_inode_elem *eie = NULL;
192         u64 disk_byte;
193
194         if (level != 0) {
195                 eb = path->nodes[level];
196                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
197                 if (ret < 0)
198                         return ret;
199                 return 0;
200         }
201
202         /*
203          * We normally enter this function with the path already pointing to
204          * the first item to check. But sometimes, we may enter it with
205          * slot==nritems. In that case, go to the next leaf before we continue.
206          */
207         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
208                 ret = btrfs_next_old_leaf(root, path, time_seq);
209
210         while (!ret) {
211                 eb = path->nodes[0];
212                 slot = path->slots[0];
213
214                 btrfs_item_key_to_cpu(eb, &key, slot);
215
216                 if (key.objectid != key_for_search->objectid ||
217                     key.type != BTRFS_EXTENT_DATA_KEY)
218                         break;
219
220                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
221                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
222
223                 if (disk_byte == wanted_disk_byte) {
224                         eie = NULL;
225                         if (extent_item_pos) {
226                                 ret = check_extent_in_eb(&key, eb, fi,
227                                                 *extent_item_pos,
228                                                 &eie);
229                                 if (ret < 0)
230                                         break;
231                         }
232                         if (!ret) {
233                                 ret = ulist_add(parents, eb->start,
234                                                 (unsigned long)eie, GFP_NOFS);
235                                 if (ret < 0)
236                                         break;
237                                 if (!extent_item_pos) {
238                                         ret = btrfs_next_old_leaf(root, path,
239                                                         time_seq);
240                                         continue;
241                                 }
242                         }
243                 }
244                 ret = btrfs_next_old_item(root, path, time_seq);
245         }
246
247         if (ret > 0)
248                 ret = 0;
249         return ret;
250 }
251
252 /*
253  * resolve an indirect backref in the form (root_id, key, level)
254  * to a logical address
255  */
256 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
257                                         int search_commit_root,
258                                         u64 time_seq,
259                                         struct __prelim_ref *ref,
260                                         struct ulist *parents,
261                                         const u64 *extent_item_pos)
262 {
263         struct btrfs_path *path;
264         struct btrfs_root *root;
265         struct btrfs_key root_key;
266         struct extent_buffer *eb;
267         int ret = 0;
268         int root_level;
269         int level = ref->level;
270
271         path = btrfs_alloc_path();
272         if (!path)
273                 return -ENOMEM;
274         path->search_commit_root = !!search_commit_root;
275
276         root_key.objectid = ref->root_id;
277         root_key.type = BTRFS_ROOT_ITEM_KEY;
278         root_key.offset = (u64)-1;
279         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
280         if (IS_ERR(root)) {
281                 ret = PTR_ERR(root);
282                 goto out;
283         }
284
285         rcu_read_lock();
286         root_level = btrfs_header_level(root->node);
287         rcu_read_unlock();
288
289         if (root_level + 1 == level)
290                 goto out;
291
292         path->lowest_level = level;
293         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
294         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
295                  "%d for key (%llu %u %llu)\n",
296                  (unsigned long long)ref->root_id, level, ref->count, ret,
297                  (unsigned long long)ref->key_for_search.objectid,
298                  ref->key_for_search.type,
299                  (unsigned long long)ref->key_for_search.offset);
300         if (ret < 0)
301                 goto out;
302
303         eb = path->nodes[level];
304         while (!eb) {
305                 if (!level) {
306                         WARN_ON(1);
307                         ret = 1;
308                         goto out;
309                 }
310                 level--;
311                 eb = path->nodes[level];
312         }
313
314         ret = add_all_parents(root, path, parents, level, &ref->key_for_search,
315                                 time_seq, ref->wanted_disk_byte,
316                                 extent_item_pos);
317 out:
318         btrfs_free_path(path);
319         return ret;
320 }
321
322 /*
323  * resolve all indirect backrefs from the list
324  */
325 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
326                                    int search_commit_root, u64 time_seq,
327                                    struct list_head *head,
328                                    const u64 *extent_item_pos)
329 {
330         int err;
331         int ret = 0;
332         struct __prelim_ref *ref;
333         struct __prelim_ref *ref_safe;
334         struct __prelim_ref *new_ref;
335         struct ulist *parents;
336         struct ulist_node *node;
337         struct ulist_iterator uiter;
338
339         parents = ulist_alloc(GFP_NOFS);
340         if (!parents)
341                 return -ENOMEM;
342
343         /*
344          * _safe allows us to insert directly after the current item without
345          * iterating over the newly inserted items.
346          * we're also allowed to re-assign ref during iteration.
347          */
348         list_for_each_entry_safe(ref, ref_safe, head, list) {
349                 if (ref->parent)        /* already direct */
350                         continue;
351                 if (ref->count == 0)
352                         continue;
353                 err = __resolve_indirect_ref(fs_info, search_commit_root,
354                                              time_seq, ref, parents,
355                                              extent_item_pos);
356                 if (err) {
357                         if (ret == 0)
358                                 ret = err;
359                         continue;
360                 }
361
362                 /* we put the first parent into the ref at hand */
363                 ULIST_ITER_INIT(&uiter);
364                 node = ulist_next(parents, &uiter);
365                 ref->parent = node ? node->val : 0;
366                 ref->inode_list =
367                         node ? (struct extent_inode_elem *)node->aux : 0;
368
369                 /* additional parents require new refs being added here */
370                 while ((node = ulist_next(parents, &uiter))) {
371                         new_ref = kmalloc(sizeof(*new_ref), GFP_NOFS);
372                         if (!new_ref) {
373                                 ret = -ENOMEM;
374                                 break;
375                         }
376                         memcpy(new_ref, ref, sizeof(*ref));
377                         new_ref->parent = node->val;
378                         new_ref->inode_list =
379                                         (struct extent_inode_elem *)node->aux;
380                         list_add(&new_ref->list, &ref->list);
381                 }
382                 ulist_reinit(parents);
383         }
384
385         ulist_free(parents);
386         return ret;
387 }
388
389 static inline int ref_for_same_block(struct __prelim_ref *ref1,
390                                      struct __prelim_ref *ref2)
391 {
392         if (ref1->level != ref2->level)
393                 return 0;
394         if (ref1->root_id != ref2->root_id)
395                 return 0;
396         if (ref1->key_for_search.type != ref2->key_for_search.type)
397                 return 0;
398         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
399                 return 0;
400         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
401                 return 0;
402         if (ref1->parent != ref2->parent)
403                 return 0;
404
405         return 1;
406 }
407
408 /*
409  * read tree blocks and add keys where required.
410  */
411 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
412                               struct list_head *head)
413 {
414         struct list_head *pos;
415         struct extent_buffer *eb;
416
417         list_for_each(pos, head) {
418                 struct __prelim_ref *ref;
419                 ref = list_entry(pos, struct __prelim_ref, list);
420
421                 if (ref->parent)
422                         continue;
423                 if (ref->key_for_search.type)
424                         continue;
425                 BUG_ON(!ref->wanted_disk_byte);
426                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
427                                      fs_info->tree_root->leafsize, 0);
428                 BUG_ON(!eb);
429                 btrfs_tree_read_lock(eb);
430                 if (btrfs_header_level(eb) == 0)
431                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
432                 else
433                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
434                 btrfs_tree_read_unlock(eb);
435                 free_extent_buffer(eb);
436         }
437         return 0;
438 }
439
440 /*
441  * merge two lists of backrefs and adjust counts accordingly
442  *
443  * mode = 1: merge identical keys, if key is set
444  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
445  *           additionally, we could even add a key range for the blocks we
446  *           looked into to merge even more (-> replace unresolved refs by those
447  *           having a parent).
448  * mode = 2: merge identical parents
449  */
450 static int __merge_refs(struct list_head *head, int mode)
451 {
452         struct list_head *pos1;
453
454         list_for_each(pos1, head) {
455                 struct list_head *n2;
456                 struct list_head *pos2;
457                 struct __prelim_ref *ref1;
458
459                 ref1 = list_entry(pos1, struct __prelim_ref, list);
460
461                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
462                      pos2 = n2, n2 = pos2->next) {
463                         struct __prelim_ref *ref2;
464                         struct __prelim_ref *xchg;
465
466                         ref2 = list_entry(pos2, struct __prelim_ref, list);
467
468                         if (mode == 1) {
469                                 if (!ref_for_same_block(ref1, ref2))
470                                         continue;
471                                 if (!ref1->parent && ref2->parent) {
472                                         xchg = ref1;
473                                         ref1 = ref2;
474                                         ref2 = xchg;
475                                 }
476                                 ref1->count += ref2->count;
477                         } else {
478                                 if (ref1->parent != ref2->parent)
479                                         continue;
480                                 ref1->count += ref2->count;
481                         }
482                         list_del(&ref2->list);
483                         kfree(ref2);
484                 }
485
486         }
487         return 0;
488 }
489
490 /*
491  * add all currently queued delayed refs from this head whose seq nr is
492  * smaller or equal that seq to the list
493  */
494 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
495                               struct list_head *prefs)
496 {
497         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
498         struct rb_node *n = &head->node.rb_node;
499         struct btrfs_key key;
500         struct btrfs_key op_key = {0};
501         int sgn;
502         int ret = 0;
503
504         if (extent_op && extent_op->update_key)
505                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
506
507         while ((n = rb_prev(n))) {
508                 struct btrfs_delayed_ref_node *node;
509                 node = rb_entry(n, struct btrfs_delayed_ref_node,
510                                 rb_node);
511                 if (node->bytenr != head->node.bytenr)
512                         break;
513                 WARN_ON(node->is_head);
514
515                 if (node->seq > seq)
516                         continue;
517
518                 switch (node->action) {
519                 case BTRFS_ADD_DELAYED_EXTENT:
520                 case BTRFS_UPDATE_DELAYED_HEAD:
521                         WARN_ON(1);
522                         continue;
523                 case BTRFS_ADD_DELAYED_REF:
524                         sgn = 1;
525                         break;
526                 case BTRFS_DROP_DELAYED_REF:
527                         sgn = -1;
528                         break;
529                 default:
530                         BUG_ON(1);
531                 }
532                 switch (node->type) {
533                 case BTRFS_TREE_BLOCK_REF_KEY: {
534                         struct btrfs_delayed_tree_ref *ref;
535
536                         ref = btrfs_delayed_node_to_tree_ref(node);
537                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
538                                                ref->level + 1, 0, node->bytenr,
539                                                node->ref_mod * sgn);
540                         break;
541                 }
542                 case BTRFS_SHARED_BLOCK_REF_KEY: {
543                         struct btrfs_delayed_tree_ref *ref;
544
545                         ref = btrfs_delayed_node_to_tree_ref(node);
546                         ret = __add_prelim_ref(prefs, ref->root, NULL,
547                                                ref->level + 1, ref->parent,
548                                                node->bytenr,
549                                                node->ref_mod * sgn);
550                         break;
551                 }
552                 case BTRFS_EXTENT_DATA_REF_KEY: {
553                         struct btrfs_delayed_data_ref *ref;
554                         ref = btrfs_delayed_node_to_data_ref(node);
555
556                         key.objectid = ref->objectid;
557                         key.type = BTRFS_EXTENT_DATA_KEY;
558                         key.offset = ref->offset;
559                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
560                                                node->bytenr,
561                                                node->ref_mod * sgn);
562                         break;
563                 }
564                 case BTRFS_SHARED_DATA_REF_KEY: {
565                         struct btrfs_delayed_data_ref *ref;
566
567                         ref = btrfs_delayed_node_to_data_ref(node);
568
569                         key.objectid = ref->objectid;
570                         key.type = BTRFS_EXTENT_DATA_KEY;
571                         key.offset = ref->offset;
572                         ret = __add_prelim_ref(prefs, ref->root, &key, 0,
573                                                ref->parent, node->bytenr,
574                                                node->ref_mod * sgn);
575                         break;
576                 }
577                 default:
578                         WARN_ON(1);
579                 }
580                 BUG_ON(ret);
581         }
582
583         return 0;
584 }
585
586 /*
587  * add all inline backrefs for bytenr to the list
588  */
589 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
590                              struct btrfs_path *path, u64 bytenr,
591                              int *info_level, struct list_head *prefs)
592 {
593         int ret = 0;
594         int slot;
595         struct extent_buffer *leaf;
596         struct btrfs_key key;
597         unsigned long ptr;
598         unsigned long end;
599         struct btrfs_extent_item *ei;
600         u64 flags;
601         u64 item_size;
602
603         /*
604          * enumerate all inline refs
605          */
606         leaf = path->nodes[0];
607         slot = path->slots[0];
608
609         item_size = btrfs_item_size_nr(leaf, slot);
610         BUG_ON(item_size < sizeof(*ei));
611
612         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
613         flags = btrfs_extent_flags(leaf, ei);
614
615         ptr = (unsigned long)(ei + 1);
616         end = (unsigned long)ei + item_size;
617
618         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
619                 struct btrfs_tree_block_info *info;
620
621                 info = (struct btrfs_tree_block_info *)ptr;
622                 *info_level = btrfs_tree_block_level(leaf, info);
623                 ptr += sizeof(struct btrfs_tree_block_info);
624                 BUG_ON(ptr > end);
625         } else {
626                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
627         }
628
629         while (ptr < end) {
630                 struct btrfs_extent_inline_ref *iref;
631                 u64 offset;
632                 int type;
633
634                 iref = (struct btrfs_extent_inline_ref *)ptr;
635                 type = btrfs_extent_inline_ref_type(leaf, iref);
636                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
637
638                 switch (type) {
639                 case BTRFS_SHARED_BLOCK_REF_KEY:
640                         ret = __add_prelim_ref(prefs, 0, NULL,
641                                                 *info_level + 1, offset,
642                                                 bytenr, 1);
643                         break;
644                 case BTRFS_SHARED_DATA_REF_KEY: {
645                         struct btrfs_shared_data_ref *sdref;
646                         int count;
647
648                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
649                         count = btrfs_shared_data_ref_count(leaf, sdref);
650                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
651                                                bytenr, count);
652                         break;
653                 }
654                 case BTRFS_TREE_BLOCK_REF_KEY:
655                         ret = __add_prelim_ref(prefs, offset, NULL,
656                                                *info_level + 1, 0,
657                                                bytenr, 1);
658                         break;
659                 case BTRFS_EXTENT_DATA_REF_KEY: {
660                         struct btrfs_extent_data_ref *dref;
661                         int count;
662                         u64 root;
663
664                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
665                         count = btrfs_extent_data_ref_count(leaf, dref);
666                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
667                                                                       dref);
668                         key.type = BTRFS_EXTENT_DATA_KEY;
669                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
670                         root = btrfs_extent_data_ref_root(leaf, dref);
671                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
672                                                bytenr, count);
673                         break;
674                 }
675                 default:
676                         WARN_ON(1);
677                 }
678                 BUG_ON(ret);
679                 ptr += btrfs_extent_inline_ref_size(type);
680         }
681
682         return 0;
683 }
684
685 /*
686  * add all non-inline backrefs for bytenr to the list
687  */
688 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
689                             struct btrfs_path *path, u64 bytenr,
690                             int info_level, struct list_head *prefs)
691 {
692         struct btrfs_root *extent_root = fs_info->extent_root;
693         int ret;
694         int slot;
695         struct extent_buffer *leaf;
696         struct btrfs_key key;
697
698         while (1) {
699                 ret = btrfs_next_item(extent_root, path);
700                 if (ret < 0)
701                         break;
702                 if (ret) {
703                         ret = 0;
704                         break;
705                 }
706
707                 slot = path->slots[0];
708                 leaf = path->nodes[0];
709                 btrfs_item_key_to_cpu(leaf, &key, slot);
710
711                 if (key.objectid != bytenr)
712                         break;
713                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
714                         continue;
715                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
716                         break;
717
718                 switch (key.type) {
719                 case BTRFS_SHARED_BLOCK_REF_KEY:
720                         ret = __add_prelim_ref(prefs, 0, NULL,
721                                                 info_level + 1, key.offset,
722                                                 bytenr, 1);
723                         break;
724                 case BTRFS_SHARED_DATA_REF_KEY: {
725                         struct btrfs_shared_data_ref *sdref;
726                         int count;
727
728                         sdref = btrfs_item_ptr(leaf, slot,
729                                               struct btrfs_shared_data_ref);
730                         count = btrfs_shared_data_ref_count(leaf, sdref);
731                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
732                                                 bytenr, count);
733                         break;
734                 }
735                 case BTRFS_TREE_BLOCK_REF_KEY:
736                         ret = __add_prelim_ref(prefs, key.offset, NULL,
737                                                info_level + 1, 0,
738                                                bytenr, 1);
739                         break;
740                 case BTRFS_EXTENT_DATA_REF_KEY: {
741                         struct btrfs_extent_data_ref *dref;
742                         int count;
743                         u64 root;
744
745                         dref = btrfs_item_ptr(leaf, slot,
746                                               struct btrfs_extent_data_ref);
747                         count = btrfs_extent_data_ref_count(leaf, dref);
748                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
749                                                                       dref);
750                         key.type = BTRFS_EXTENT_DATA_KEY;
751                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
752                         root = btrfs_extent_data_ref_root(leaf, dref);
753                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
754                                                bytenr, count);
755                         break;
756                 }
757                 default:
758                         WARN_ON(1);
759                 }
760                 BUG_ON(ret);
761         }
762
763         return ret;
764 }
765
766 /*
767  * this adds all existing backrefs (inline backrefs, backrefs and delayed
768  * refs) for the given bytenr to the refs list, merges duplicates and resolves
769  * indirect refs to their parent bytenr.
770  * When roots are found, they're added to the roots list
771  *
772  * FIXME some caching might speed things up
773  */
774 static int find_parent_nodes(struct btrfs_trans_handle *trans,
775                              struct btrfs_fs_info *fs_info, u64 bytenr,
776                              u64 delayed_ref_seq, u64 time_seq,
777                              struct ulist *refs, struct ulist *roots,
778                              const u64 *extent_item_pos)
779 {
780         struct btrfs_key key;
781         struct btrfs_path *path;
782         struct btrfs_delayed_ref_root *delayed_refs = NULL;
783         struct btrfs_delayed_ref_head *head;
784         int info_level = 0;
785         int ret;
786         int search_commit_root = (trans == BTRFS_BACKREF_SEARCH_COMMIT_ROOT);
787         struct list_head prefs_delayed;
788         struct list_head prefs;
789         struct __prelim_ref *ref;
790
791         INIT_LIST_HEAD(&prefs);
792         INIT_LIST_HEAD(&prefs_delayed);
793
794         key.objectid = bytenr;
795         key.type = BTRFS_EXTENT_ITEM_KEY;
796         key.offset = (u64)-1;
797
798         path = btrfs_alloc_path();
799         if (!path)
800                 return -ENOMEM;
801         path->search_commit_root = !!search_commit_root;
802
803         /*
804          * grab both a lock on the path and a lock on the delayed ref head.
805          * We need both to get a consistent picture of how the refs look
806          * at a specified point in time
807          */
808 again:
809         head = NULL;
810
811         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
812         if (ret < 0)
813                 goto out;
814         BUG_ON(ret == 0);
815
816         if (trans != BTRFS_BACKREF_SEARCH_COMMIT_ROOT) {
817                 /*
818                  * look if there are updates for this ref queued and lock the
819                  * head
820                  */
821                 delayed_refs = &trans->transaction->delayed_refs;
822                 spin_lock(&delayed_refs->lock);
823                 head = btrfs_find_delayed_ref_head(trans, bytenr);
824                 if (head) {
825                         if (!mutex_trylock(&head->mutex)) {
826                                 atomic_inc(&head->node.refs);
827                                 spin_unlock(&delayed_refs->lock);
828
829                                 btrfs_release_path(path);
830
831                                 /*
832                                  * Mutex was contended, block until it's
833                                  * released and try again
834                                  */
835                                 mutex_lock(&head->mutex);
836                                 mutex_unlock(&head->mutex);
837                                 btrfs_put_delayed_ref(&head->node);
838                                 goto again;
839                         }
840                         ret = __add_delayed_refs(head, delayed_ref_seq,
841                                                  &prefs_delayed);
842                         if (ret) {
843                                 spin_unlock(&delayed_refs->lock);
844                                 goto out;
845                         }
846                 }
847                 spin_unlock(&delayed_refs->lock);
848         }
849
850         if (path->slots[0]) {
851                 struct extent_buffer *leaf;
852                 int slot;
853
854                 path->slots[0]--;
855                 leaf = path->nodes[0];
856                 slot = path->slots[0];
857                 btrfs_item_key_to_cpu(leaf, &key, slot);
858                 if (key.objectid == bytenr &&
859                     key.type == BTRFS_EXTENT_ITEM_KEY) {
860                         ret = __add_inline_refs(fs_info, path, bytenr,
861                                                 &info_level, &prefs);
862                         if (ret)
863                                 goto out;
864                         ret = __add_keyed_refs(fs_info, path, bytenr,
865                                                info_level, &prefs);
866                         if (ret)
867                                 goto out;
868                 }
869         }
870         btrfs_release_path(path);
871
872         list_splice_init(&prefs_delayed, &prefs);
873
874         ret = __add_missing_keys(fs_info, &prefs);
875         if (ret)
876                 goto out;
877
878         ret = __merge_refs(&prefs, 1);
879         if (ret)
880                 goto out;
881
882         ret = __resolve_indirect_refs(fs_info, search_commit_root, time_seq,
883                                       &prefs, extent_item_pos);
884         if (ret)
885                 goto out;
886
887         ret = __merge_refs(&prefs, 2);
888         if (ret)
889                 goto out;
890
891         while (!list_empty(&prefs)) {
892                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
893                 list_del(&ref->list);
894                 if (ref->count < 0)
895                         WARN_ON(1);
896                 if (ref->count && ref->root_id && ref->parent == 0) {
897                         /* no parent == root of tree */
898                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
899                         BUG_ON(ret < 0);
900                 }
901                 if (ref->count && ref->parent) {
902                         struct extent_inode_elem *eie = NULL;
903                         if (extent_item_pos && !ref->inode_list) {
904                                 u32 bsz;
905                                 struct extent_buffer *eb;
906                                 bsz = btrfs_level_size(fs_info->extent_root,
907                                                         info_level);
908                                 eb = read_tree_block(fs_info->extent_root,
909                                                            ref->parent, bsz, 0);
910                                 BUG_ON(!eb);
911                                 ret = find_extent_in_eb(eb, bytenr,
912                                                         *extent_item_pos, &eie);
913                                 ref->inode_list = eie;
914                                 free_extent_buffer(eb);
915                         }
916                         ret = ulist_add_merge(refs, ref->parent,
917                                               (unsigned long)ref->inode_list,
918                                               (unsigned long *)&eie, GFP_NOFS);
919                         if (!ret && extent_item_pos) {
920                                 /*
921                                  * we've recorded that parent, so we must extend
922                                  * its inode list here
923                                  */
924                                 BUG_ON(!eie);
925                                 while (eie->next)
926                                         eie = eie->next;
927                                 eie->next = ref->inode_list;
928                         }
929                         BUG_ON(ret < 0);
930                 }
931                 kfree(ref);
932         }
933
934 out:
935         if (head)
936                 mutex_unlock(&head->mutex);
937         btrfs_free_path(path);
938         while (!list_empty(&prefs)) {
939                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
940                 list_del(&ref->list);
941                 kfree(ref);
942         }
943         while (!list_empty(&prefs_delayed)) {
944                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
945                                        list);
946                 list_del(&ref->list);
947                 kfree(ref);
948         }
949
950         return ret;
951 }
952
953 static void free_leaf_list(struct ulist *blocks)
954 {
955         struct ulist_node *node = NULL;
956         struct extent_inode_elem *eie;
957         struct extent_inode_elem *eie_next;
958         struct ulist_iterator uiter;
959
960         ULIST_ITER_INIT(&uiter);
961         while ((node = ulist_next(blocks, &uiter))) {
962                 if (!node->aux)
963                         continue;
964                 eie = (struct extent_inode_elem *)node->aux;
965                 for (; eie; eie = eie_next) {
966                         eie_next = eie->next;
967                         kfree(eie);
968                 }
969                 node->aux = 0;
970         }
971
972         ulist_free(blocks);
973 }
974
975 /*
976  * Finds all leafs with a reference to the specified combination of bytenr and
977  * offset. key_list_head will point to a list of corresponding keys (caller must
978  * free each list element). The leafs will be stored in the leafs ulist, which
979  * must be freed with ulist_free.
980  *
981  * returns 0 on success, <0 on error
982  */
983 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
984                                 struct btrfs_fs_info *fs_info, u64 bytenr,
985                                 u64 delayed_ref_seq, u64 time_seq,
986                                 struct ulist **leafs,
987                                 const u64 *extent_item_pos)
988 {
989         struct ulist *tmp;
990         int ret;
991
992         tmp = ulist_alloc(GFP_NOFS);
993         if (!tmp)
994                 return -ENOMEM;
995         *leafs = ulist_alloc(GFP_NOFS);
996         if (!*leafs) {
997                 ulist_free(tmp);
998                 return -ENOMEM;
999         }
1000
1001         ret = find_parent_nodes(trans, fs_info, bytenr, delayed_ref_seq,
1002                                 time_seq, *leafs, tmp, extent_item_pos);
1003         ulist_free(tmp);
1004
1005         if (ret < 0 && ret != -ENOENT) {
1006                 free_leaf_list(*leafs);
1007                 return ret;
1008         }
1009
1010         return 0;
1011 }
1012
1013 /*
1014  * walk all backrefs for a given extent to find all roots that reference this
1015  * extent. Walking a backref means finding all extents that reference this
1016  * extent and in turn walk the backrefs of those, too. Naturally this is a
1017  * recursive process, but here it is implemented in an iterative fashion: We
1018  * find all referencing extents for the extent in question and put them on a
1019  * list. In turn, we find all referencing extents for those, further appending
1020  * to the list. The way we iterate the list allows adding more elements after
1021  * the current while iterating. The process stops when we reach the end of the
1022  * list. Found roots are added to the roots list.
1023  *
1024  * returns 0 on success, < 0 on error.
1025  */
1026 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1027                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1028                                 u64 delayed_ref_seq, u64 time_seq,
1029                                 struct ulist **roots)
1030 {
1031         struct ulist *tmp;
1032         struct ulist_node *node = NULL;
1033         struct ulist_iterator uiter;
1034         int ret;
1035
1036         tmp = ulist_alloc(GFP_NOFS);
1037         if (!tmp)
1038                 return -ENOMEM;
1039         *roots = ulist_alloc(GFP_NOFS);
1040         if (!*roots) {
1041                 ulist_free(tmp);
1042                 return -ENOMEM;
1043         }
1044
1045         ULIST_ITER_INIT(&uiter);
1046         while (1) {
1047                 ret = find_parent_nodes(trans, fs_info, bytenr, delayed_ref_seq,
1048                                         time_seq, tmp, *roots, NULL);
1049                 if (ret < 0 && ret != -ENOENT) {
1050                         ulist_free(tmp);
1051                         ulist_free(*roots);
1052                         return ret;
1053                 }
1054                 node = ulist_next(tmp, &uiter);
1055                 if (!node)
1056                         break;
1057                 bytenr = node->val;
1058         }
1059
1060         ulist_free(tmp);
1061         return 0;
1062 }
1063
1064
1065 static int __inode_info(u64 inum, u64 ioff, u8 key_type,
1066                         struct btrfs_root *fs_root, struct btrfs_path *path,
1067                         struct btrfs_key *found_key)
1068 {
1069         int ret;
1070         struct btrfs_key key;
1071         struct extent_buffer *eb;
1072
1073         key.type = key_type;
1074         key.objectid = inum;
1075         key.offset = ioff;
1076
1077         ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
1078         if (ret < 0)
1079                 return ret;
1080
1081         eb = path->nodes[0];
1082         if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
1083                 ret = btrfs_next_leaf(fs_root, path);
1084                 if (ret)
1085                         return ret;
1086                 eb = path->nodes[0];
1087         }
1088
1089         btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
1090         if (found_key->type != key.type || found_key->objectid != key.objectid)
1091                 return 1;
1092
1093         return 0;
1094 }
1095
1096 /*
1097  * this makes the path point to (inum INODE_ITEM ioff)
1098  */
1099 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1100                         struct btrfs_path *path)
1101 {
1102         struct btrfs_key key;
1103         return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
1104                                 &key);
1105 }
1106
1107 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1108                                 struct btrfs_path *path,
1109                                 struct btrfs_key *found_key)
1110 {
1111         return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
1112                                 found_key);
1113 }
1114
1115 /*
1116  * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements
1117  * of the path are separated by '/' and the path is guaranteed to be
1118  * 0-terminated. the path is only given within the current file system.
1119  * Therefore, it never starts with a '/'. the caller is responsible to provide
1120  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1121  * the start point of the resulting string is returned. this pointer is within
1122  * dest, normally.
1123  * in case the path buffer would overflow, the pointer is decremented further
1124  * as if output was written to the buffer, though no more output is actually
1125  * generated. that way, the caller can determine how much space would be
1126  * required for the path to fit into the buffer. in that case, the returned
1127  * value will be smaller than dest. callers must check this!
1128  */
1129 static char *iref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1130                                 struct btrfs_inode_ref *iref,
1131                                 struct extent_buffer *eb_in, u64 parent,
1132                                 char *dest, u32 size)
1133 {
1134         u32 len;
1135         int slot;
1136         u64 next_inum;
1137         int ret;
1138         s64 bytes_left = size - 1;
1139         struct extent_buffer *eb = eb_in;
1140         struct btrfs_key found_key;
1141         int leave_spinning = path->leave_spinning;
1142
1143         if (bytes_left >= 0)
1144                 dest[bytes_left] = '\0';
1145
1146         path->leave_spinning = 1;
1147         while (1) {
1148                 len = btrfs_inode_ref_name_len(eb, iref);
1149                 bytes_left -= len;
1150                 if (bytes_left >= 0)
1151                         read_extent_buffer(eb, dest + bytes_left,
1152                                                 (unsigned long)(iref + 1), len);
1153                 if (eb != eb_in) {
1154                         btrfs_tree_read_unlock_blocking(eb);
1155                         free_extent_buffer(eb);
1156                 }
1157                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1158                 if (ret > 0)
1159                         ret = -ENOENT;
1160                 if (ret)
1161                         break;
1162                 next_inum = found_key.offset;
1163
1164                 /* regular exit ahead */
1165                 if (parent == next_inum)
1166                         break;
1167
1168                 slot = path->slots[0];
1169                 eb = path->nodes[0];
1170                 /* make sure we can use eb after releasing the path */
1171                 if (eb != eb_in) {
1172                         atomic_inc(&eb->refs);
1173                         btrfs_tree_read_lock(eb);
1174                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1175                 }
1176                 btrfs_release_path(path);
1177
1178                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1179                 parent = next_inum;
1180                 --bytes_left;
1181                 if (bytes_left >= 0)
1182                         dest[bytes_left] = '/';
1183         }
1184
1185         btrfs_release_path(path);
1186         path->leave_spinning = leave_spinning;
1187
1188         if (ret)
1189                 return ERR_PTR(ret);
1190
1191         return dest + bytes_left;
1192 }
1193
1194 /*
1195  * this makes the path point to (logical EXTENT_ITEM *)
1196  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1197  * tree blocks and <0 on error.
1198  */
1199 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1200                         struct btrfs_path *path, struct btrfs_key *found_key)
1201 {
1202         int ret;
1203         u64 flags;
1204         u32 item_size;
1205         struct extent_buffer *eb;
1206         struct btrfs_extent_item *ei;
1207         struct btrfs_key key;
1208
1209         key.type = BTRFS_EXTENT_ITEM_KEY;
1210         key.objectid = logical;
1211         key.offset = (u64)-1;
1212
1213         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1214         if (ret < 0)
1215                 return ret;
1216         ret = btrfs_previous_item(fs_info->extent_root, path,
1217                                         0, BTRFS_EXTENT_ITEM_KEY);
1218         if (ret < 0)
1219                 return ret;
1220
1221         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1222         if (found_key->type != BTRFS_EXTENT_ITEM_KEY ||
1223             found_key->objectid > logical ||
1224             found_key->objectid + found_key->offset <= logical) {
1225                 pr_debug("logical %llu is not within any extent\n",
1226                          (unsigned long long)logical);
1227                 return -ENOENT;
1228         }
1229
1230         eb = path->nodes[0];
1231         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1232         BUG_ON(item_size < sizeof(*ei));
1233
1234         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1235         flags = btrfs_extent_flags(eb, ei);
1236
1237         pr_debug("logical %llu is at position %llu within the extent (%llu "
1238                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1239                  (unsigned long long)logical,
1240                  (unsigned long long)(logical - found_key->objectid),
1241                  (unsigned long long)found_key->objectid,
1242                  (unsigned long long)found_key->offset,
1243                  (unsigned long long)flags, item_size);
1244         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1245                 return BTRFS_EXTENT_FLAG_TREE_BLOCK;
1246         if (flags & BTRFS_EXTENT_FLAG_DATA)
1247                 return BTRFS_EXTENT_FLAG_DATA;
1248
1249         return -EIO;
1250 }
1251
1252 /*
1253  * helper function to iterate extent inline refs. ptr must point to a 0 value
1254  * for the first call and may be modified. it is used to track state.
1255  * if more refs exist, 0 is returned and the next call to
1256  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1257  * next ref. after the last ref was processed, 1 is returned.
1258  * returns <0 on error
1259  */
1260 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1261                                 struct btrfs_extent_item *ei, u32 item_size,
1262                                 struct btrfs_extent_inline_ref **out_eiref,
1263                                 int *out_type)
1264 {
1265         unsigned long end;
1266         u64 flags;
1267         struct btrfs_tree_block_info *info;
1268
1269         if (!*ptr) {
1270                 /* first call */
1271                 flags = btrfs_extent_flags(eb, ei);
1272                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1273                         info = (struct btrfs_tree_block_info *)(ei + 1);
1274                         *out_eiref =
1275                                 (struct btrfs_extent_inline_ref *)(info + 1);
1276                 } else {
1277                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1278                 }
1279                 *ptr = (unsigned long)*out_eiref;
1280                 if ((void *)*ptr >= (void *)ei + item_size)
1281                         return -ENOENT;
1282         }
1283
1284         end = (unsigned long)ei + item_size;
1285         *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
1286         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1287
1288         *ptr += btrfs_extent_inline_ref_size(*out_type);
1289         WARN_ON(*ptr > end);
1290         if (*ptr == end)
1291                 return 1; /* last */
1292
1293         return 0;
1294 }
1295
1296 /*
1297  * reads the tree block backref for an extent. tree level and root are returned
1298  * through out_level and out_root. ptr must point to a 0 value for the first
1299  * call and may be modified (see __get_extent_inline_ref comment).
1300  * returns 0 if data was provided, 1 if there was no more data to provide or
1301  * <0 on error.
1302  */
1303 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1304                                 struct btrfs_extent_item *ei, u32 item_size,
1305                                 u64 *out_root, u8 *out_level)
1306 {
1307         int ret;
1308         int type;
1309         struct btrfs_tree_block_info *info;
1310         struct btrfs_extent_inline_ref *eiref;
1311
1312         if (*ptr == (unsigned long)-1)
1313                 return 1;
1314
1315         while (1) {
1316                 ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
1317                                                 &eiref, &type);
1318                 if (ret < 0)
1319                         return ret;
1320
1321                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1322                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1323                         break;
1324
1325                 if (ret == 1)
1326                         return 1;
1327         }
1328
1329         /* we can treat both ref types equally here */
1330         info = (struct btrfs_tree_block_info *)(ei + 1);
1331         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1332         *out_level = btrfs_tree_block_level(eb, info);
1333
1334         if (ret == 1)
1335                 *ptr = (unsigned long)-1;
1336
1337         return 0;
1338 }
1339
1340 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1341                                 u64 root, u64 extent_item_objectid,
1342                                 iterate_extent_inodes_t *iterate, void *ctx)
1343 {
1344         struct extent_inode_elem *eie;
1345         int ret = 0;
1346
1347         for (eie = inode_list; eie; eie = eie->next) {
1348                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1349                          "root %llu\n", extent_item_objectid,
1350                          eie->inum, eie->offset, root);
1351                 ret = iterate(eie->inum, eie->offset, root, ctx);
1352                 if (ret) {
1353                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1354                                  extent_item_objectid, ret);
1355                         break;
1356                 }
1357         }
1358
1359         return ret;
1360 }
1361
1362 /*
1363  * calls iterate() for every inode that references the extent identified by
1364  * the given parameters.
1365  * when the iterator function returns a non-zero value, iteration stops.
1366  */
1367 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1368                                 u64 extent_item_objectid, u64 extent_item_pos,
1369                                 int search_commit_root,
1370                                 iterate_extent_inodes_t *iterate, void *ctx)
1371 {
1372         int ret;
1373         struct list_head data_refs = LIST_HEAD_INIT(data_refs);
1374         struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
1375         struct btrfs_trans_handle *trans;
1376         struct ulist *refs = NULL;
1377         struct ulist *roots = NULL;
1378         struct ulist_node *ref_node = NULL;
1379         struct ulist_node *root_node = NULL;
1380         struct seq_list seq_elem = {};
1381         struct seq_list tree_mod_seq_elem = {};
1382         struct ulist_iterator ref_uiter;
1383         struct ulist_iterator root_uiter;
1384         struct btrfs_delayed_ref_root *delayed_refs = NULL;
1385
1386         pr_debug("resolving all inodes for extent %llu\n",
1387                         extent_item_objectid);
1388
1389         if (search_commit_root) {
1390                 trans = BTRFS_BACKREF_SEARCH_COMMIT_ROOT;
1391         } else {
1392                 trans = btrfs_join_transaction(fs_info->extent_root);
1393                 if (IS_ERR(trans))
1394                         return PTR_ERR(trans);
1395
1396                 delayed_refs = &trans->transaction->delayed_refs;
1397                 spin_lock(&delayed_refs->lock);
1398                 btrfs_get_delayed_seq(delayed_refs, &seq_elem);
1399                 spin_unlock(&delayed_refs->lock);
1400                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1401         }
1402
1403         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1404                                    seq_elem.seq, tree_mod_seq_elem.seq, &refs,
1405                                    &extent_item_pos);
1406         if (ret)
1407                 goto out;
1408
1409         ULIST_ITER_INIT(&ref_uiter);
1410         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1411                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1412                                                 seq_elem.seq,
1413                                                 tree_mod_seq_elem.seq, &roots);
1414                 if (ret)
1415                         break;
1416                 ULIST_ITER_INIT(&root_uiter);
1417                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1418                         pr_debug("root %llu references leaf %llu, data list "
1419                                  "%#lx\n", root_node->val, ref_node->val,
1420                                  ref_node->aux);
1421                         ret = iterate_leaf_refs(
1422                                 (struct extent_inode_elem *)ref_node->aux,
1423                                 root_node->val, extent_item_objectid,
1424                                 iterate, ctx);
1425                 }
1426                 ulist_free(roots);
1427                 roots = NULL;
1428         }
1429
1430         free_leaf_list(refs);
1431         ulist_free(roots);
1432 out:
1433         if (!search_commit_root) {
1434                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1435                 btrfs_put_delayed_seq(delayed_refs, &seq_elem);
1436                 btrfs_end_transaction(trans, fs_info->extent_root);
1437         }
1438
1439         return ret;
1440 }
1441
1442 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1443                                 struct btrfs_path *path,
1444                                 iterate_extent_inodes_t *iterate, void *ctx)
1445 {
1446         int ret;
1447         u64 extent_item_pos;
1448         struct btrfs_key found_key;
1449         int search_commit_root = path->search_commit_root;
1450
1451         ret = extent_from_logical(fs_info, logical, path,
1452                                         &found_key);
1453         btrfs_release_path(path);
1454         if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1455                 ret = -EINVAL;
1456         if (ret < 0)
1457                 return ret;
1458
1459         extent_item_pos = logical - found_key.objectid;
1460         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1461                                         extent_item_pos, search_commit_root,
1462                                         iterate, ctx);
1463
1464         return ret;
1465 }
1466
1467 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1468                                 struct btrfs_path *path,
1469                                 iterate_irefs_t *iterate, void *ctx)
1470 {
1471         int ret = 0;
1472         int slot;
1473         u32 cur;
1474         u32 len;
1475         u32 name_len;
1476         u64 parent = 0;
1477         int found = 0;
1478         struct extent_buffer *eb;
1479         struct btrfs_item *item;
1480         struct btrfs_inode_ref *iref;
1481         struct btrfs_key found_key;
1482
1483         while (!ret) {
1484                 path->leave_spinning = 1;
1485                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1486                                         &found_key);
1487                 if (ret < 0)
1488                         break;
1489                 if (ret) {
1490                         ret = found ? 0 : -ENOENT;
1491                         break;
1492                 }
1493                 ++found;
1494
1495                 parent = found_key.offset;
1496                 slot = path->slots[0];
1497                 eb = path->nodes[0];
1498                 /* make sure we can use eb after releasing the path */
1499                 atomic_inc(&eb->refs);
1500                 btrfs_tree_read_lock(eb);
1501                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1502                 btrfs_release_path(path);
1503
1504                 item = btrfs_item_nr(eb, slot);
1505                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1506
1507                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1508                         name_len = btrfs_inode_ref_name_len(eb, iref);
1509                         /* path must be released before calling iterate()! */
1510                         pr_debug("following ref at offset %u for inode %llu in "
1511                                  "tree %llu\n", cur,
1512                                  (unsigned long long)found_key.objectid,
1513                                  (unsigned long long)fs_root->objectid);
1514                         ret = iterate(parent, iref, eb, ctx);
1515                         if (ret)
1516                                 break;
1517                         len = sizeof(*iref) + name_len;
1518                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1519                 }
1520                 btrfs_tree_read_unlock_blocking(eb);
1521                 free_extent_buffer(eb);
1522         }
1523
1524         btrfs_release_path(path);
1525
1526         return ret;
1527 }
1528
1529 /*
1530  * returns 0 if the path could be dumped (probably truncated)
1531  * returns <0 in case of an error
1532  */
1533 static int inode_to_path(u64 inum, struct btrfs_inode_ref *iref,
1534                                 struct extent_buffer *eb, void *ctx)
1535 {
1536         struct inode_fs_paths *ipath = ctx;
1537         char *fspath;
1538         char *fspath_min;
1539         int i = ipath->fspath->elem_cnt;
1540         const int s_ptr = sizeof(char *);
1541         u32 bytes_left;
1542
1543         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1544                                         ipath->fspath->bytes_left - s_ptr : 0;
1545
1546         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1547         fspath = iref_to_path(ipath->fs_root, ipath->btrfs_path, iref, eb,
1548                                 inum, fspath_min, bytes_left);
1549         if (IS_ERR(fspath))
1550                 return PTR_ERR(fspath);
1551
1552         if (fspath > fspath_min) {
1553                 pr_debug("path resolved: %s\n", fspath);
1554                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1555                 ++ipath->fspath->elem_cnt;
1556                 ipath->fspath->bytes_left = fspath - fspath_min;
1557         } else {
1558                 pr_debug("missed path, not enough space. missing bytes: %lu, "
1559                          "constructed so far: %s\n",
1560                          (unsigned long)(fspath_min - fspath), fspath_min);
1561                 ++ipath->fspath->elem_missed;
1562                 ipath->fspath->bytes_missing += fspath_min - fspath;
1563                 ipath->fspath->bytes_left = 0;
1564         }
1565
1566         return 0;
1567 }
1568
1569 /*
1570  * this dumps all file system paths to the inode into the ipath struct, provided
1571  * is has been created large enough. each path is zero-terminated and accessed
1572  * from ipath->fspath->val[i].
1573  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1574  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1575  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1576  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1577  * have been needed to return all paths.
1578  */
1579 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1580 {
1581         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1582                                 inode_to_path, ipath);
1583 }
1584
1585 struct btrfs_data_container *init_data_container(u32 total_bytes)
1586 {
1587         struct btrfs_data_container *data;
1588         size_t alloc_bytes;
1589
1590         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1591         data = kmalloc(alloc_bytes, GFP_NOFS);
1592         if (!data)
1593                 return ERR_PTR(-ENOMEM);
1594
1595         if (total_bytes >= sizeof(*data)) {
1596                 data->bytes_left = total_bytes - sizeof(*data);
1597                 data->bytes_missing = 0;
1598         } else {
1599                 data->bytes_missing = sizeof(*data) - total_bytes;
1600                 data->bytes_left = 0;
1601         }
1602
1603         data->elem_cnt = 0;
1604         data->elem_missed = 0;
1605
1606         return data;
1607 }
1608
1609 /*
1610  * allocates space to return multiple file system paths for an inode.
1611  * total_bytes to allocate are passed, note that space usable for actual path
1612  * information will be total_bytes - sizeof(struct inode_fs_paths).
1613  * the returned pointer must be freed with free_ipath() in the end.
1614  */
1615 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1616                                         struct btrfs_path *path)
1617 {
1618         struct inode_fs_paths *ifp;
1619         struct btrfs_data_container *fspath;
1620
1621         fspath = init_data_container(total_bytes);
1622         if (IS_ERR(fspath))
1623                 return (void *)fspath;
1624
1625         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1626         if (!ifp) {
1627                 kfree(fspath);
1628                 return ERR_PTR(-ENOMEM);
1629         }
1630
1631         ifp->btrfs_path = path;
1632         ifp->fspath = fspath;
1633         ifp->fs_root = fs_root;
1634
1635         return ifp;
1636 }
1637
1638 void free_ipath(struct inode_fs_paths *ipath)
1639 {
1640         if (!ipath)
1641                 return;
1642         kfree(ipath->fspath);
1643         kfree(ipath);
1644 }