fs/btrfs: drop if around WARN_ON
[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 <linux/vmalloc.h>
20 #include "ctree.h"
21 #include "disk-io.h"
22 #include "backref.h"
23 #include "ulist.h"
24 #include "transaction.h"
25 #include "delayed-ref.h"
26 #include "locking.h"
27
28 struct extent_inode_elem {
29         u64 inum;
30         u64 offset;
31         struct extent_inode_elem *next;
32 };
33
34 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
35                                 struct btrfs_file_extent_item *fi,
36                                 u64 extent_item_pos,
37                                 struct extent_inode_elem **eie)
38 {
39         u64 data_offset;
40         u64 data_len;
41         struct extent_inode_elem *e;
42
43         data_offset = btrfs_file_extent_offset(eb, fi);
44         data_len = btrfs_file_extent_num_bytes(eb, fi);
45
46         if (extent_item_pos < data_offset ||
47             extent_item_pos >= data_offset + data_len)
48                 return 1;
49
50         e = kmalloc(sizeof(*e), GFP_NOFS);
51         if (!e)
52                 return -ENOMEM;
53
54         e->next = *eie;
55         e->inum = key->objectid;
56         e->offset = key->offset + (extent_item_pos - data_offset);
57         *eie = e;
58
59         return 0;
60 }
61
62 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
63                                 u64 extent_item_pos,
64                                 struct extent_inode_elem **eie)
65 {
66         u64 disk_byte;
67         struct btrfs_key key;
68         struct btrfs_file_extent_item *fi;
69         int slot;
70         int nritems;
71         int extent_type;
72         int ret;
73
74         /*
75          * from the shared data ref, we only have the leaf but we need
76          * the key. thus, we must look into all items and see that we
77          * find one (some) with a reference to our extent item.
78          */
79         nritems = btrfs_header_nritems(eb);
80         for (slot = 0; slot < nritems; ++slot) {
81                 btrfs_item_key_to_cpu(eb, &key, slot);
82                 if (key.type != BTRFS_EXTENT_DATA_KEY)
83                         continue;
84                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
85                 extent_type = btrfs_file_extent_type(eb, fi);
86                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
87                         continue;
88                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
89                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
90                 if (disk_byte != wanted_disk_byte)
91                         continue;
92
93                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
94                 if (ret < 0)
95                         return ret;
96         }
97
98         return 0;
99 }
100
101 /*
102  * this structure records all encountered refs on the way up to the root
103  */
104 struct __prelim_ref {
105         struct list_head list;
106         u64 root_id;
107         struct btrfs_key key_for_search;
108         int level;
109         int count;
110         struct extent_inode_elem *inode_list;
111         u64 parent;
112         u64 wanted_disk_byte;
113 };
114
115 /*
116  * the rules for all callers of this function are:
117  * - obtaining the parent is the goal
118  * - if you add a key, you must know that it is a correct key
119  * - if you cannot add the parent or a correct key, then we will look into the
120  *   block later to set a correct key
121  *
122  * delayed refs
123  * ============
124  *        backref type | shared | indirect | shared | indirect
125  * information         |   tree |     tree |   data |     data
126  * --------------------+--------+----------+--------+----------
127  *      parent logical |    y   |     -    |    -   |     -
128  *      key to resolve |    -   |     y    |    y   |     y
129  *  tree block logical |    -   |     -    |    -   |     -
130  *  root for resolving |    y   |     y    |    y   |     y
131  *
132  * - column 1:       we've the parent -> done
133  * - column 2, 3, 4: we use the key to find the parent
134  *
135  * on disk refs (inline or keyed)
136  * ==============================
137  *        backref type | shared | indirect | shared | indirect
138  * information         |   tree |     tree |   data |     data
139  * --------------------+--------+----------+--------+----------
140  *      parent logical |    y   |     -    |    y   |     -
141  *      key to resolve |    -   |     -    |    -   |     y
142  *  tree block logical |    y   |     y    |    y   |     y
143  *  root for resolving |    -   |     y    |    y   |     y
144  *
145  * - column 1, 3: we've the parent -> done
146  * - column 2:    we take the first key from the block to find the parent
147  *                (see __add_missing_keys)
148  * - column 4:    we use the key to find the parent
149  *
150  * additional information that's available but not required to find the parent
151  * block might help in merging entries to gain some speed.
152  */
153
154 static int __add_prelim_ref(struct list_head *head, u64 root_id,
155                             struct btrfs_key *key, int level,
156                             u64 parent, u64 wanted_disk_byte, int count)
157 {
158         struct __prelim_ref *ref;
159
160         /* in case we're adding delayed refs, we're holding the refs spinlock */
161         ref = kmalloc(sizeof(*ref), GFP_ATOMIC);
162         if (!ref)
163                 return -ENOMEM;
164
165         ref->root_id = root_id;
166         if (key)
167                 ref->key_for_search = *key;
168         else
169                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
170
171         ref->inode_list = NULL;
172         ref->level = level;
173         ref->count = count;
174         ref->parent = parent;
175         ref->wanted_disk_byte = wanted_disk_byte;
176         list_add_tail(&ref->list, head);
177
178         return 0;
179 }
180
181 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
182                                 struct ulist *parents, int level,
183                                 struct btrfs_key *key_for_search, u64 time_seq,
184                                 u64 wanted_disk_byte,
185                                 const u64 *extent_item_pos)
186 {
187         int ret = 0;
188         int slot;
189         struct extent_buffer *eb;
190         struct btrfs_key key;
191         struct btrfs_file_extent_item *fi;
192         struct extent_inode_elem *eie = NULL;
193         u64 disk_byte;
194
195         if (level != 0) {
196                 eb = path->nodes[level];
197                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
198                 if (ret < 0)
199                         return ret;
200                 return 0;
201         }
202
203         /*
204          * We normally enter this function with the path already pointing to
205          * the first item to check. But sometimes, we may enter it with
206          * slot==nritems. In that case, go to the next leaf before we continue.
207          */
208         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
209                 ret = btrfs_next_old_leaf(root, path, time_seq);
210
211         while (!ret) {
212                 eb = path->nodes[0];
213                 slot = path->slots[0];
214
215                 btrfs_item_key_to_cpu(eb, &key, slot);
216
217                 if (key.objectid != key_for_search->objectid ||
218                     key.type != BTRFS_EXTENT_DATA_KEY)
219                         break;
220
221                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
222                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
223
224                 if (disk_byte == wanted_disk_byte) {
225                         eie = NULL;
226                         if (extent_item_pos) {
227                                 ret = check_extent_in_eb(&key, eb, fi,
228                                                 *extent_item_pos,
229                                                 &eie);
230                                 if (ret < 0)
231                                         break;
232                         }
233                         if (!ret) {
234                                 ret = ulist_add(parents, eb->start,
235                                                 (uintptr_t)eie, GFP_NOFS);
236                                 if (ret < 0)
237                                         break;
238                                 if (!extent_item_pos) {
239                                         ret = btrfs_next_old_leaf(root, path,
240                                                         time_seq);
241                                         continue;
242                                 }
243                         }
244                 }
245                 ret = btrfs_next_old_item(root, path, time_seq);
246         }
247
248         if (ret > 0)
249                 ret = 0;
250         return ret;
251 }
252
253 /*
254  * resolve an indirect backref in the form (root_id, key, level)
255  * to a logical address
256  */
257 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
258                                         int search_commit_root,
259                                         u64 time_seq,
260                                         struct __prelim_ref *ref,
261                                         struct ulist *parents,
262                                         const u64 *extent_item_pos)
263 {
264         struct btrfs_path *path;
265         struct btrfs_root *root;
266         struct btrfs_key root_key;
267         struct extent_buffer *eb;
268         int ret = 0;
269         int root_level;
270         int level = ref->level;
271
272         path = btrfs_alloc_path();
273         if (!path)
274                 return -ENOMEM;
275         path->search_commit_root = !!search_commit_root;
276
277         root_key.objectid = ref->root_id;
278         root_key.type = BTRFS_ROOT_ITEM_KEY;
279         root_key.offset = (u64)-1;
280         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
281         if (IS_ERR(root)) {
282                 ret = PTR_ERR(root);
283                 goto out;
284         }
285
286         root_level = btrfs_old_root_level(root, time_seq);
287
288         if (root_level + 1 == level)
289                 goto out;
290
291         path->lowest_level = level;
292         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
293         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
294                  "%d for key (%llu %u %llu)\n",
295                  (unsigned long long)ref->root_id, level, ref->count, ret,
296                  (unsigned long long)ref->key_for_search.objectid,
297                  ref->key_for_search.type,
298                  (unsigned long long)ref->key_for_search.offset);
299         if (ret < 0)
300                 goto out;
301
302         eb = path->nodes[level];
303         while (!eb) {
304                 if (!level) {
305                         WARN_ON(1);
306                         ret = 1;
307                         goto out;
308                 }
309                 level--;
310                 eb = path->nodes[level];
311         }
312
313         ret = add_all_parents(root, path, parents, level, &ref->key_for_search,
314                                 time_seq, ref->wanted_disk_byte,
315                                 extent_item_pos);
316 out:
317         btrfs_free_path(path);
318         return ret;
319 }
320
321 /*
322  * resolve all indirect backrefs from the list
323  */
324 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
325                                    int search_commit_root, u64 time_seq,
326                                    struct list_head *head,
327                                    const u64 *extent_item_pos)
328 {
329         int err;
330         int ret = 0;
331         struct __prelim_ref *ref;
332         struct __prelim_ref *ref_safe;
333         struct __prelim_ref *new_ref;
334         struct ulist *parents;
335         struct ulist_node *node;
336         struct ulist_iterator uiter;
337
338         parents = ulist_alloc(GFP_NOFS);
339         if (!parents)
340                 return -ENOMEM;
341
342         /*
343          * _safe allows us to insert directly after the current item without
344          * iterating over the newly inserted items.
345          * we're also allowed to re-assign ref during iteration.
346          */
347         list_for_each_entry_safe(ref, ref_safe, head, list) {
348                 if (ref->parent)        /* already direct */
349                         continue;
350                 if (ref->count == 0)
351                         continue;
352                 err = __resolve_indirect_ref(fs_info, search_commit_root,
353                                              time_seq, ref, parents,
354                                              extent_item_pos);
355                 if (err) {
356                         if (ret == 0)
357                                 ret = err;
358                         continue;
359                 }
360
361                 /* we put the first parent into the ref at hand */
362                 ULIST_ITER_INIT(&uiter);
363                 node = ulist_next(parents, &uiter);
364                 ref->parent = node ? node->val : 0;
365                 ref->inode_list = node ?
366                         (struct extent_inode_elem *)(uintptr_t)node->aux : 0;
367
368                 /* additional parents require new refs being added here */
369                 while ((node = ulist_next(parents, &uiter))) {
370                         new_ref = kmalloc(sizeof(*new_ref), GFP_NOFS);
371                         if (!new_ref) {
372                                 ret = -ENOMEM;
373                                 break;
374                         }
375                         memcpy(new_ref, ref, sizeof(*ref));
376                         new_ref->parent = node->val;
377                         new_ref->inode_list = (struct extent_inode_elem *)
378                                                         (uintptr_t)node->aux;
379                         list_add(&new_ref->list, &ref->list);
380                 }
381                 ulist_reinit(parents);
382         }
383
384         ulist_free(parents);
385         return ret;
386 }
387
388 static inline int ref_for_same_block(struct __prelim_ref *ref1,
389                                      struct __prelim_ref *ref2)
390 {
391         if (ref1->level != ref2->level)
392                 return 0;
393         if (ref1->root_id != ref2->root_id)
394                 return 0;
395         if (ref1->key_for_search.type != ref2->key_for_search.type)
396                 return 0;
397         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
398                 return 0;
399         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
400                 return 0;
401         if (ref1->parent != ref2->parent)
402                 return 0;
403
404         return 1;
405 }
406
407 /*
408  * read tree blocks and add keys where required.
409  */
410 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
411                               struct list_head *head)
412 {
413         struct list_head *pos;
414         struct extent_buffer *eb;
415
416         list_for_each(pos, head) {
417                 struct __prelim_ref *ref;
418                 ref = list_entry(pos, struct __prelim_ref, list);
419
420                 if (ref->parent)
421                         continue;
422                 if (ref->key_for_search.type)
423                         continue;
424                 BUG_ON(!ref->wanted_disk_byte);
425                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
426                                      fs_info->tree_root->leafsize, 0);
427                 BUG_ON(!eb);
428                 btrfs_tree_read_lock(eb);
429                 if (btrfs_header_level(eb) == 0)
430                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
431                 else
432                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
433                 btrfs_tree_read_unlock(eb);
434                 free_extent_buffer(eb);
435         }
436         return 0;
437 }
438
439 /*
440  * merge two lists of backrefs and adjust counts accordingly
441  *
442  * mode = 1: merge identical keys, if key is set
443  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
444  *           additionally, we could even add a key range for the blocks we
445  *           looked into to merge even more (-> replace unresolved refs by those
446  *           having a parent).
447  * mode = 2: merge identical parents
448  */
449 static int __merge_refs(struct list_head *head, int mode)
450 {
451         struct list_head *pos1;
452
453         list_for_each(pos1, head) {
454                 struct list_head *n2;
455                 struct list_head *pos2;
456                 struct __prelim_ref *ref1;
457
458                 ref1 = list_entry(pos1, struct __prelim_ref, list);
459
460                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
461                      pos2 = n2, n2 = pos2->next) {
462                         struct __prelim_ref *ref2;
463                         struct __prelim_ref *xchg;
464
465                         ref2 = list_entry(pos2, struct __prelim_ref, list);
466
467                         if (mode == 1) {
468                                 if (!ref_for_same_block(ref1, ref2))
469                                         continue;
470                                 if (!ref1->parent && ref2->parent) {
471                                         xchg = ref1;
472                                         ref1 = ref2;
473                                         ref2 = xchg;
474                                 }
475                                 ref1->count += ref2->count;
476                         } else {
477                                 if (ref1->parent != ref2->parent)
478                                         continue;
479                                 ref1->count += ref2->count;
480                         }
481                         list_del(&ref2->list);
482                         kfree(ref2);
483                 }
484
485         }
486         return 0;
487 }
488
489 /*
490  * add all currently queued delayed refs from this head whose seq nr is
491  * smaller or equal that seq to the list
492  */
493 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
494                               struct list_head *prefs)
495 {
496         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
497         struct rb_node *n = &head->node.rb_node;
498         struct btrfs_key key;
499         struct btrfs_key op_key = {0};
500         int sgn;
501         int ret = 0;
502
503         if (extent_op && extent_op->update_key)
504                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
505
506         while ((n = rb_prev(n))) {
507                 struct btrfs_delayed_ref_node *node;
508                 node = rb_entry(n, struct btrfs_delayed_ref_node,
509                                 rb_node);
510                 if (node->bytenr != head->node.bytenr)
511                         break;
512                 WARN_ON(node->is_head);
513
514                 if (node->seq > seq)
515                         continue;
516
517                 switch (node->action) {
518                 case BTRFS_ADD_DELAYED_EXTENT:
519                 case BTRFS_UPDATE_DELAYED_HEAD:
520                         WARN_ON(1);
521                         continue;
522                 case BTRFS_ADD_DELAYED_REF:
523                         sgn = 1;
524                         break;
525                 case BTRFS_DROP_DELAYED_REF:
526                         sgn = -1;
527                         break;
528                 default:
529                         BUG_ON(1);
530                 }
531                 switch (node->type) {
532                 case BTRFS_TREE_BLOCK_REF_KEY: {
533                         struct btrfs_delayed_tree_ref *ref;
534
535                         ref = btrfs_delayed_node_to_tree_ref(node);
536                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
537                                                ref->level + 1, 0, node->bytenr,
538                                                node->ref_mod * sgn);
539                         break;
540                 }
541                 case BTRFS_SHARED_BLOCK_REF_KEY: {
542                         struct btrfs_delayed_tree_ref *ref;
543
544                         ref = btrfs_delayed_node_to_tree_ref(node);
545                         ret = __add_prelim_ref(prefs, ref->root, NULL,
546                                                ref->level + 1, ref->parent,
547                                                node->bytenr,
548                                                node->ref_mod * sgn);
549                         break;
550                 }
551                 case BTRFS_EXTENT_DATA_REF_KEY: {
552                         struct btrfs_delayed_data_ref *ref;
553                         ref = btrfs_delayed_node_to_data_ref(node);
554
555                         key.objectid = ref->objectid;
556                         key.type = BTRFS_EXTENT_DATA_KEY;
557                         key.offset = ref->offset;
558                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
559                                                node->bytenr,
560                                                node->ref_mod * sgn);
561                         break;
562                 }
563                 case BTRFS_SHARED_DATA_REF_KEY: {
564                         struct btrfs_delayed_data_ref *ref;
565
566                         ref = btrfs_delayed_node_to_data_ref(node);
567
568                         key.objectid = ref->objectid;
569                         key.type = BTRFS_EXTENT_DATA_KEY;
570                         key.offset = ref->offset;
571                         ret = __add_prelim_ref(prefs, ref->root, &key, 0,
572                                                ref->parent, node->bytenr,
573                                                node->ref_mod * sgn);
574                         break;
575                 }
576                 default:
577                         WARN_ON(1);
578                 }
579                 BUG_ON(ret);
580         }
581
582         return 0;
583 }
584
585 /*
586  * add all inline backrefs for bytenr to the list
587  */
588 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
589                              struct btrfs_path *path, u64 bytenr,
590                              int *info_level, struct list_head *prefs)
591 {
592         int ret = 0;
593         int slot;
594         struct extent_buffer *leaf;
595         struct btrfs_key key;
596         unsigned long ptr;
597         unsigned long end;
598         struct btrfs_extent_item *ei;
599         u64 flags;
600         u64 item_size;
601
602         /*
603          * enumerate all inline refs
604          */
605         leaf = path->nodes[0];
606         slot = path->slots[0];
607
608         item_size = btrfs_item_size_nr(leaf, slot);
609         BUG_ON(item_size < sizeof(*ei));
610
611         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
612         flags = btrfs_extent_flags(leaf, ei);
613
614         ptr = (unsigned long)(ei + 1);
615         end = (unsigned long)ei + item_size;
616
617         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
618                 struct btrfs_tree_block_info *info;
619
620                 info = (struct btrfs_tree_block_info *)ptr;
621                 *info_level = btrfs_tree_block_level(leaf, info);
622                 ptr += sizeof(struct btrfs_tree_block_info);
623                 BUG_ON(ptr > end);
624         } else {
625                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
626         }
627
628         while (ptr < end) {
629                 struct btrfs_extent_inline_ref *iref;
630                 u64 offset;
631                 int type;
632
633                 iref = (struct btrfs_extent_inline_ref *)ptr;
634                 type = btrfs_extent_inline_ref_type(leaf, iref);
635                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
636
637                 switch (type) {
638                 case BTRFS_SHARED_BLOCK_REF_KEY:
639                         ret = __add_prelim_ref(prefs, 0, NULL,
640                                                 *info_level + 1, offset,
641                                                 bytenr, 1);
642                         break;
643                 case BTRFS_SHARED_DATA_REF_KEY: {
644                         struct btrfs_shared_data_ref *sdref;
645                         int count;
646
647                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
648                         count = btrfs_shared_data_ref_count(leaf, sdref);
649                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
650                                                bytenr, count);
651                         break;
652                 }
653                 case BTRFS_TREE_BLOCK_REF_KEY:
654                         ret = __add_prelim_ref(prefs, offset, NULL,
655                                                *info_level + 1, 0,
656                                                bytenr, 1);
657                         break;
658                 case BTRFS_EXTENT_DATA_REF_KEY: {
659                         struct btrfs_extent_data_ref *dref;
660                         int count;
661                         u64 root;
662
663                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
664                         count = btrfs_extent_data_ref_count(leaf, dref);
665                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
666                                                                       dref);
667                         key.type = BTRFS_EXTENT_DATA_KEY;
668                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
669                         root = btrfs_extent_data_ref_root(leaf, dref);
670                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
671                                                bytenr, count);
672                         break;
673                 }
674                 default:
675                         WARN_ON(1);
676                 }
677                 BUG_ON(ret);
678                 ptr += btrfs_extent_inline_ref_size(type);
679         }
680
681         return 0;
682 }
683
684 /*
685  * add all non-inline backrefs for bytenr to the list
686  */
687 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
688                             struct btrfs_path *path, u64 bytenr,
689                             int info_level, struct list_head *prefs)
690 {
691         struct btrfs_root *extent_root = fs_info->extent_root;
692         int ret;
693         int slot;
694         struct extent_buffer *leaf;
695         struct btrfs_key key;
696
697         while (1) {
698                 ret = btrfs_next_item(extent_root, path);
699                 if (ret < 0)
700                         break;
701                 if (ret) {
702                         ret = 0;
703                         break;
704                 }
705
706                 slot = path->slots[0];
707                 leaf = path->nodes[0];
708                 btrfs_item_key_to_cpu(leaf, &key, slot);
709
710                 if (key.objectid != bytenr)
711                         break;
712                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
713                         continue;
714                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
715                         break;
716
717                 switch (key.type) {
718                 case BTRFS_SHARED_BLOCK_REF_KEY:
719                         ret = __add_prelim_ref(prefs, 0, NULL,
720                                                 info_level + 1, key.offset,
721                                                 bytenr, 1);
722                         break;
723                 case BTRFS_SHARED_DATA_REF_KEY: {
724                         struct btrfs_shared_data_ref *sdref;
725                         int count;
726
727                         sdref = btrfs_item_ptr(leaf, slot,
728                                               struct btrfs_shared_data_ref);
729                         count = btrfs_shared_data_ref_count(leaf, sdref);
730                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
731                                                 bytenr, count);
732                         break;
733                 }
734                 case BTRFS_TREE_BLOCK_REF_KEY:
735                         ret = __add_prelim_ref(prefs, key.offset, NULL,
736                                                info_level + 1, 0,
737                                                bytenr, 1);
738                         break;
739                 case BTRFS_EXTENT_DATA_REF_KEY: {
740                         struct btrfs_extent_data_ref *dref;
741                         int count;
742                         u64 root;
743
744                         dref = btrfs_item_ptr(leaf, slot,
745                                               struct btrfs_extent_data_ref);
746                         count = btrfs_extent_data_ref_count(leaf, dref);
747                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
748                                                                       dref);
749                         key.type = BTRFS_EXTENT_DATA_KEY;
750                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
751                         root = btrfs_extent_data_ref_root(leaf, dref);
752                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
753                                                bytenr, count);
754                         break;
755                 }
756                 default:
757                         WARN_ON(1);
758                 }
759                 BUG_ON(ret);
760         }
761
762         return ret;
763 }
764
765 /*
766  * this adds all existing backrefs (inline backrefs, backrefs and delayed
767  * refs) for the given bytenr to the refs list, merges duplicates and resolves
768  * indirect refs to their parent bytenr.
769  * When roots are found, they're added to the roots list
770  *
771  * FIXME some caching might speed things up
772  */
773 static int find_parent_nodes(struct btrfs_trans_handle *trans,
774                              struct btrfs_fs_info *fs_info, u64 bytenr,
775                              u64 time_seq, struct ulist *refs,
776                              struct ulist *roots, const u64 *extent_item_pos)
777 {
778         struct btrfs_key key;
779         struct btrfs_path *path;
780         struct btrfs_delayed_ref_root *delayed_refs = NULL;
781         struct btrfs_delayed_ref_head *head;
782         int info_level = 0;
783         int ret;
784         int search_commit_root = (trans == BTRFS_BACKREF_SEARCH_COMMIT_ROOT);
785         struct list_head prefs_delayed;
786         struct list_head prefs;
787         struct __prelim_ref *ref;
788
789         INIT_LIST_HEAD(&prefs);
790         INIT_LIST_HEAD(&prefs_delayed);
791
792         key.objectid = bytenr;
793         key.type = BTRFS_EXTENT_ITEM_KEY;
794         key.offset = (u64)-1;
795
796         path = btrfs_alloc_path();
797         if (!path)
798                 return -ENOMEM;
799         path->search_commit_root = !!search_commit_root;
800
801         /*
802          * grab both a lock on the path and a lock on the delayed ref head.
803          * We need both to get a consistent picture of how the refs look
804          * at a specified point in time
805          */
806 again:
807         head = NULL;
808
809         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
810         if (ret < 0)
811                 goto out;
812         BUG_ON(ret == 0);
813
814         if (trans != BTRFS_BACKREF_SEARCH_COMMIT_ROOT) {
815                 /*
816                  * look if there are updates for this ref queued and lock the
817                  * head
818                  */
819                 delayed_refs = &trans->transaction->delayed_refs;
820                 spin_lock(&delayed_refs->lock);
821                 head = btrfs_find_delayed_ref_head(trans, bytenr);
822                 if (head) {
823                         if (!mutex_trylock(&head->mutex)) {
824                                 atomic_inc(&head->node.refs);
825                                 spin_unlock(&delayed_refs->lock);
826
827                                 btrfs_release_path(path);
828
829                                 /*
830                                  * Mutex was contended, block until it's
831                                  * released and try again
832                                  */
833                                 mutex_lock(&head->mutex);
834                                 mutex_unlock(&head->mutex);
835                                 btrfs_put_delayed_ref(&head->node);
836                                 goto again;
837                         }
838                         ret = __add_delayed_refs(head, time_seq,
839                                                  &prefs_delayed);
840                         mutex_unlock(&head->mutex);
841                         if (ret) {
842                                 spin_unlock(&delayed_refs->lock);
843                                 goto out;
844                         }
845                 }
846                 spin_unlock(&delayed_refs->lock);
847         }
848
849         if (path->slots[0]) {
850                 struct extent_buffer *leaf;
851                 int slot;
852
853                 path->slots[0]--;
854                 leaf = path->nodes[0];
855                 slot = path->slots[0];
856                 btrfs_item_key_to_cpu(leaf, &key, slot);
857                 if (key.objectid == bytenr &&
858                     key.type == BTRFS_EXTENT_ITEM_KEY) {
859                         ret = __add_inline_refs(fs_info, path, bytenr,
860                                                 &info_level, &prefs);
861                         if (ret)
862                                 goto out;
863                         ret = __add_keyed_refs(fs_info, path, bytenr,
864                                                info_level, &prefs);
865                         if (ret)
866                                 goto out;
867                 }
868         }
869         btrfs_release_path(path);
870
871         list_splice_init(&prefs_delayed, &prefs);
872
873         ret = __add_missing_keys(fs_info, &prefs);
874         if (ret)
875                 goto out;
876
877         ret = __merge_refs(&prefs, 1);
878         if (ret)
879                 goto out;
880
881         ret = __resolve_indirect_refs(fs_info, search_commit_root, time_seq,
882                                       &prefs, extent_item_pos);
883         if (ret)
884                 goto out;
885
886         ret = __merge_refs(&prefs, 2);
887         if (ret)
888                 goto out;
889
890         while (!list_empty(&prefs)) {
891                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
892                 list_del(&ref->list);
893                 WARN_ON(ref->count < 0);
894                 if (ref->count && ref->root_id && ref->parent == 0) {
895                         /* no parent == root of tree */
896                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
897                         BUG_ON(ret < 0);
898                 }
899                 if (ref->count && ref->parent) {
900                         struct extent_inode_elem *eie = NULL;
901                         if (extent_item_pos && !ref->inode_list) {
902                                 u32 bsz;
903                                 struct extent_buffer *eb;
904                                 bsz = btrfs_level_size(fs_info->extent_root,
905                                                         info_level);
906                                 eb = read_tree_block(fs_info->extent_root,
907                                                            ref->parent, bsz, 0);
908                                 BUG_ON(!eb);
909                                 ret = find_extent_in_eb(eb, bytenr,
910                                                         *extent_item_pos, &eie);
911                                 ref->inode_list = eie;
912                                 free_extent_buffer(eb);
913                         }
914                         ret = ulist_add_merge(refs, ref->parent,
915                                               (uintptr_t)ref->inode_list,
916                                               (u64 *)&eie, GFP_NOFS);
917                         if (!ret && extent_item_pos) {
918                                 /*
919                                  * we've recorded that parent, so we must extend
920                                  * its inode list here
921                                  */
922                                 BUG_ON(!eie);
923                                 while (eie->next)
924                                         eie = eie->next;
925                                 eie->next = ref->inode_list;
926                         }
927                         BUG_ON(ret < 0);
928                 }
929                 kfree(ref);
930         }
931
932 out:
933         btrfs_free_path(path);
934         while (!list_empty(&prefs)) {
935                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
936                 list_del(&ref->list);
937                 kfree(ref);
938         }
939         while (!list_empty(&prefs_delayed)) {
940                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
941                                        list);
942                 list_del(&ref->list);
943                 kfree(ref);
944         }
945
946         return ret;
947 }
948
949 static void free_leaf_list(struct ulist *blocks)
950 {
951         struct ulist_node *node = NULL;
952         struct extent_inode_elem *eie;
953         struct extent_inode_elem *eie_next;
954         struct ulist_iterator uiter;
955
956         ULIST_ITER_INIT(&uiter);
957         while ((node = ulist_next(blocks, &uiter))) {
958                 if (!node->aux)
959                         continue;
960                 eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
961                 for (; eie; eie = eie_next) {
962                         eie_next = eie->next;
963                         kfree(eie);
964                 }
965                 node->aux = 0;
966         }
967
968         ulist_free(blocks);
969 }
970
971 /*
972  * Finds all leafs with a reference to the specified combination of bytenr and
973  * offset. key_list_head will point to a list of corresponding keys (caller must
974  * free each list element). The leafs will be stored in the leafs ulist, which
975  * must be freed with ulist_free.
976  *
977  * returns 0 on success, <0 on error
978  */
979 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
980                                 struct btrfs_fs_info *fs_info, u64 bytenr,
981                                 u64 time_seq, struct ulist **leafs,
982                                 const u64 *extent_item_pos)
983 {
984         struct ulist *tmp;
985         int ret;
986
987         tmp = ulist_alloc(GFP_NOFS);
988         if (!tmp)
989                 return -ENOMEM;
990         *leafs = ulist_alloc(GFP_NOFS);
991         if (!*leafs) {
992                 ulist_free(tmp);
993                 return -ENOMEM;
994         }
995
996         ret = find_parent_nodes(trans, fs_info, bytenr,
997                                 time_seq, *leafs, tmp, extent_item_pos);
998         ulist_free(tmp);
999
1000         if (ret < 0 && ret != -ENOENT) {
1001                 free_leaf_list(*leafs);
1002                 return ret;
1003         }
1004
1005         return 0;
1006 }
1007
1008 /*
1009  * walk all backrefs for a given extent to find all roots that reference this
1010  * extent. Walking a backref means finding all extents that reference this
1011  * extent and in turn walk the backrefs of those, too. Naturally this is a
1012  * recursive process, but here it is implemented in an iterative fashion: We
1013  * find all referencing extents for the extent in question and put them on a
1014  * list. In turn, we find all referencing extents for those, further appending
1015  * to the list. The way we iterate the list allows adding more elements after
1016  * the current while iterating. The process stops when we reach the end of the
1017  * list. Found roots are added to the roots list.
1018  *
1019  * returns 0 on success, < 0 on error.
1020  */
1021 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1022                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1023                                 u64 time_seq, struct ulist **roots)
1024 {
1025         struct ulist *tmp;
1026         struct ulist_node *node = NULL;
1027         struct ulist_iterator uiter;
1028         int ret;
1029
1030         tmp = ulist_alloc(GFP_NOFS);
1031         if (!tmp)
1032                 return -ENOMEM;
1033         *roots = ulist_alloc(GFP_NOFS);
1034         if (!*roots) {
1035                 ulist_free(tmp);
1036                 return -ENOMEM;
1037         }
1038
1039         ULIST_ITER_INIT(&uiter);
1040         while (1) {
1041                 ret = find_parent_nodes(trans, fs_info, bytenr,
1042                                         time_seq, tmp, *roots, NULL);
1043                 if (ret < 0 && ret != -ENOENT) {
1044                         ulist_free(tmp);
1045                         ulist_free(*roots);
1046                         return ret;
1047                 }
1048                 node = ulist_next(tmp, &uiter);
1049                 if (!node)
1050                         break;
1051                 bytenr = node->val;
1052         }
1053
1054         ulist_free(tmp);
1055         return 0;
1056 }
1057
1058
1059 static int __inode_info(u64 inum, u64 ioff, u8 key_type,
1060                         struct btrfs_root *fs_root, struct btrfs_path *path,
1061                         struct btrfs_key *found_key)
1062 {
1063         int ret;
1064         struct btrfs_key key;
1065         struct extent_buffer *eb;
1066
1067         key.type = key_type;
1068         key.objectid = inum;
1069         key.offset = ioff;
1070
1071         ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
1072         if (ret < 0)
1073                 return ret;
1074
1075         eb = path->nodes[0];
1076         if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
1077                 ret = btrfs_next_leaf(fs_root, path);
1078                 if (ret)
1079                         return ret;
1080                 eb = path->nodes[0];
1081         }
1082
1083         btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
1084         if (found_key->type != key.type || found_key->objectid != key.objectid)
1085                 return 1;
1086
1087         return 0;
1088 }
1089
1090 /*
1091  * this makes the path point to (inum INODE_ITEM ioff)
1092  */
1093 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1094                         struct btrfs_path *path)
1095 {
1096         struct btrfs_key key;
1097         return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
1098                                 &key);
1099 }
1100
1101 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1102                                 struct btrfs_path *path,
1103                                 struct btrfs_key *found_key)
1104 {
1105         return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
1106                                 found_key);
1107 }
1108
1109 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1110                           u64 start_off, struct btrfs_path *path,
1111                           struct btrfs_inode_extref **ret_extref,
1112                           u64 *found_off)
1113 {
1114         int ret, slot;
1115         struct btrfs_key key;
1116         struct btrfs_key found_key;
1117         struct btrfs_inode_extref *extref;
1118         struct extent_buffer *leaf;
1119         unsigned long ptr;
1120
1121         key.objectid = inode_objectid;
1122         btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
1123         key.offset = start_off;
1124
1125         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1126         if (ret < 0)
1127                 return ret;
1128
1129         while (1) {
1130                 leaf = path->nodes[0];
1131                 slot = path->slots[0];
1132                 if (slot >= btrfs_header_nritems(leaf)) {
1133                         /*
1134                          * If the item at offset is not found,
1135                          * btrfs_search_slot will point us to the slot
1136                          * where it should be inserted. In our case
1137                          * that will be the slot directly before the
1138                          * next INODE_REF_KEY_V2 item. In the case
1139                          * that we're pointing to the last slot in a
1140                          * leaf, we must move one leaf over.
1141                          */
1142                         ret = btrfs_next_leaf(root, path);
1143                         if (ret) {
1144                                 if (ret >= 1)
1145                                         ret = -ENOENT;
1146                                 break;
1147                         }
1148                         continue;
1149                 }
1150
1151                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1152
1153                 /*
1154                  * Check that we're still looking at an extended ref key for
1155                  * this particular objectid. If we have different
1156                  * objectid or type then there are no more to be found
1157                  * in the tree and we can exit.
1158                  */
1159                 ret = -ENOENT;
1160                 if (found_key.objectid != inode_objectid)
1161                         break;
1162                 if (btrfs_key_type(&found_key) != BTRFS_INODE_EXTREF_KEY)
1163                         break;
1164
1165                 ret = 0;
1166                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1167                 extref = (struct btrfs_inode_extref *)ptr;
1168                 *ret_extref = extref;
1169                 if (found_off)
1170                         *found_off = found_key.offset;
1171                 break;
1172         }
1173
1174         return ret;
1175 }
1176
1177 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1178                         u32 name_len, unsigned long name_off,
1179                         struct extent_buffer *eb_in, u64 parent,
1180                         char *dest, u32 size)
1181 {
1182         int slot;
1183         u64 next_inum;
1184         int ret;
1185         s64 bytes_left = ((s64)size) - 1;
1186         struct extent_buffer *eb = eb_in;
1187         struct btrfs_key found_key;
1188         int leave_spinning = path->leave_spinning;
1189         struct btrfs_inode_ref *iref;
1190
1191         if (bytes_left >= 0)
1192                 dest[bytes_left] = '\0';
1193
1194         path->leave_spinning = 1;
1195         while (1) {
1196                 bytes_left -= name_len;
1197                 if (bytes_left >= 0)
1198                         read_extent_buffer(eb, dest + bytes_left,
1199                                            name_off, name_len);
1200                 if (eb != eb_in) {
1201                         btrfs_tree_read_unlock_blocking(eb);
1202                         free_extent_buffer(eb);
1203                 }
1204                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1205                 if (ret > 0)
1206                         ret = -ENOENT;
1207                 if (ret)
1208                         break;
1209
1210                 next_inum = found_key.offset;
1211
1212                 /* regular exit ahead */
1213                 if (parent == next_inum)
1214                         break;
1215
1216                 slot = path->slots[0];
1217                 eb = path->nodes[0];
1218                 /* make sure we can use eb after releasing the path */
1219                 if (eb != eb_in) {
1220                         atomic_inc(&eb->refs);
1221                         btrfs_tree_read_lock(eb);
1222                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1223                 }
1224                 btrfs_release_path(path);
1225                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1226
1227                 name_len = btrfs_inode_ref_name_len(eb, iref);
1228                 name_off = (unsigned long)(iref + 1);
1229
1230                 parent = next_inum;
1231                 --bytes_left;
1232                 if (bytes_left >= 0)
1233                         dest[bytes_left] = '/';
1234         }
1235
1236         btrfs_release_path(path);
1237         path->leave_spinning = leave_spinning;
1238
1239         if (ret)
1240                 return ERR_PTR(ret);
1241
1242         return dest + bytes_left;
1243 }
1244
1245 /*
1246  * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements
1247  * of the path are separated by '/' and the path is guaranteed to be
1248  * 0-terminated. the path is only given within the current file system.
1249  * Therefore, it never starts with a '/'. the caller is responsible to provide
1250  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1251  * the start point of the resulting string is returned. this pointer is within
1252  * dest, normally.
1253  * in case the path buffer would overflow, the pointer is decremented further
1254  * as if output was written to the buffer, though no more output is actually
1255  * generated. that way, the caller can determine how much space would be
1256  * required for the path to fit into the buffer. in that case, the returned
1257  * value will be smaller than dest. callers must check this!
1258  */
1259 char *btrfs_iref_to_path(struct btrfs_root *fs_root,
1260                          struct btrfs_path *path,
1261                          struct btrfs_inode_ref *iref,
1262                          struct extent_buffer *eb_in, u64 parent,
1263                          char *dest, u32 size)
1264 {
1265         return btrfs_ref_to_path(fs_root, path,
1266                                  btrfs_inode_ref_name_len(eb_in, iref),
1267                                  (unsigned long)(iref + 1),
1268                                  eb_in, parent, dest, size);
1269 }
1270
1271 /*
1272  * this makes the path point to (logical EXTENT_ITEM *)
1273  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1274  * tree blocks and <0 on error.
1275  */
1276 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1277                         struct btrfs_path *path, struct btrfs_key *found_key,
1278                         u64 *flags_ret)
1279 {
1280         int ret;
1281         u64 flags;
1282         u32 item_size;
1283         struct extent_buffer *eb;
1284         struct btrfs_extent_item *ei;
1285         struct btrfs_key key;
1286
1287         key.type = BTRFS_EXTENT_ITEM_KEY;
1288         key.objectid = logical;
1289         key.offset = (u64)-1;
1290
1291         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1292         if (ret < 0)
1293                 return ret;
1294         ret = btrfs_previous_item(fs_info->extent_root, path,
1295                                         0, BTRFS_EXTENT_ITEM_KEY);
1296         if (ret < 0)
1297                 return ret;
1298
1299         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1300         if (found_key->type != BTRFS_EXTENT_ITEM_KEY ||
1301             found_key->objectid > logical ||
1302             found_key->objectid + found_key->offset <= logical) {
1303                 pr_debug("logical %llu is not within any extent\n",
1304                          (unsigned long long)logical);
1305                 return -ENOENT;
1306         }
1307
1308         eb = path->nodes[0];
1309         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1310         BUG_ON(item_size < sizeof(*ei));
1311
1312         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1313         flags = btrfs_extent_flags(eb, ei);
1314
1315         pr_debug("logical %llu is at position %llu within the extent (%llu "
1316                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1317                  (unsigned long long)logical,
1318                  (unsigned long long)(logical - found_key->objectid),
1319                  (unsigned long long)found_key->objectid,
1320                  (unsigned long long)found_key->offset,
1321                  (unsigned long long)flags, item_size);
1322
1323         WARN_ON(!flags_ret);
1324         if (flags_ret) {
1325                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1326                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1327                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1328                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1329                 else
1330                         BUG_ON(1);
1331                 return 0;
1332         }
1333
1334         return -EIO;
1335 }
1336
1337 /*
1338  * helper function to iterate extent inline refs. ptr must point to a 0 value
1339  * for the first call and may be modified. it is used to track state.
1340  * if more refs exist, 0 is returned and the next call to
1341  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1342  * next ref. after the last ref was processed, 1 is returned.
1343  * returns <0 on error
1344  */
1345 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1346                                 struct btrfs_extent_item *ei, u32 item_size,
1347                                 struct btrfs_extent_inline_ref **out_eiref,
1348                                 int *out_type)
1349 {
1350         unsigned long end;
1351         u64 flags;
1352         struct btrfs_tree_block_info *info;
1353
1354         if (!*ptr) {
1355                 /* first call */
1356                 flags = btrfs_extent_flags(eb, ei);
1357                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1358                         info = (struct btrfs_tree_block_info *)(ei + 1);
1359                         *out_eiref =
1360                                 (struct btrfs_extent_inline_ref *)(info + 1);
1361                 } else {
1362                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1363                 }
1364                 *ptr = (unsigned long)*out_eiref;
1365                 if ((void *)*ptr >= (void *)ei + item_size)
1366                         return -ENOENT;
1367         }
1368
1369         end = (unsigned long)ei + item_size;
1370         *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
1371         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1372
1373         *ptr += btrfs_extent_inline_ref_size(*out_type);
1374         WARN_ON(*ptr > end);
1375         if (*ptr == end)
1376                 return 1; /* last */
1377
1378         return 0;
1379 }
1380
1381 /*
1382  * reads the tree block backref for an extent. tree level and root are returned
1383  * through out_level and out_root. ptr must point to a 0 value for the first
1384  * call and may be modified (see __get_extent_inline_ref comment).
1385  * returns 0 if data was provided, 1 if there was no more data to provide or
1386  * <0 on error.
1387  */
1388 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1389                                 struct btrfs_extent_item *ei, u32 item_size,
1390                                 u64 *out_root, u8 *out_level)
1391 {
1392         int ret;
1393         int type;
1394         struct btrfs_tree_block_info *info;
1395         struct btrfs_extent_inline_ref *eiref;
1396
1397         if (*ptr == (unsigned long)-1)
1398                 return 1;
1399
1400         while (1) {
1401                 ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
1402                                                 &eiref, &type);
1403                 if (ret < 0)
1404                         return ret;
1405
1406                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1407                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1408                         break;
1409
1410                 if (ret == 1)
1411                         return 1;
1412         }
1413
1414         /* we can treat both ref types equally here */
1415         info = (struct btrfs_tree_block_info *)(ei + 1);
1416         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1417         *out_level = btrfs_tree_block_level(eb, info);
1418
1419         if (ret == 1)
1420                 *ptr = (unsigned long)-1;
1421
1422         return 0;
1423 }
1424
1425 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1426                                 u64 root, u64 extent_item_objectid,
1427                                 iterate_extent_inodes_t *iterate, void *ctx)
1428 {
1429         struct extent_inode_elem *eie;
1430         int ret = 0;
1431
1432         for (eie = inode_list; eie; eie = eie->next) {
1433                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1434                          "root %llu\n", extent_item_objectid,
1435                          eie->inum, eie->offset, root);
1436                 ret = iterate(eie->inum, eie->offset, root, ctx);
1437                 if (ret) {
1438                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1439                                  extent_item_objectid, ret);
1440                         break;
1441                 }
1442         }
1443
1444         return ret;
1445 }
1446
1447 /*
1448  * calls iterate() for every inode that references the extent identified by
1449  * the given parameters.
1450  * when the iterator function returns a non-zero value, iteration stops.
1451  */
1452 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1453                                 u64 extent_item_objectid, u64 extent_item_pos,
1454                                 int search_commit_root,
1455                                 iterate_extent_inodes_t *iterate, void *ctx)
1456 {
1457         int ret;
1458         struct list_head data_refs = LIST_HEAD_INIT(data_refs);
1459         struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
1460         struct btrfs_trans_handle *trans;
1461         struct ulist *refs = NULL;
1462         struct ulist *roots = NULL;
1463         struct ulist_node *ref_node = NULL;
1464         struct ulist_node *root_node = NULL;
1465         struct seq_list tree_mod_seq_elem = {};
1466         struct ulist_iterator ref_uiter;
1467         struct ulist_iterator root_uiter;
1468
1469         pr_debug("resolving all inodes for extent %llu\n",
1470                         extent_item_objectid);
1471
1472         if (search_commit_root) {
1473                 trans = BTRFS_BACKREF_SEARCH_COMMIT_ROOT;
1474         } else {
1475                 trans = btrfs_join_transaction(fs_info->extent_root);
1476                 if (IS_ERR(trans))
1477                         return PTR_ERR(trans);
1478                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1479         }
1480
1481         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1482                                    tree_mod_seq_elem.seq, &refs,
1483                                    &extent_item_pos);
1484         if (ret)
1485                 goto out;
1486
1487         ULIST_ITER_INIT(&ref_uiter);
1488         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1489                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1490                                            tree_mod_seq_elem.seq, &roots);
1491                 if (ret)
1492                         break;
1493                 ULIST_ITER_INIT(&root_uiter);
1494                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1495                         pr_debug("root %llu references leaf %llu, data list "
1496                                  "%#llx\n", root_node->val, ref_node->val,
1497                                  (long long)ref_node->aux);
1498                         ret = iterate_leaf_refs((struct extent_inode_elem *)
1499                                                 (uintptr_t)ref_node->aux,
1500                                                 root_node->val,
1501                                                 extent_item_objectid,
1502                                                 iterate, ctx);
1503                 }
1504                 ulist_free(roots);
1505                 roots = NULL;
1506         }
1507
1508         free_leaf_list(refs);
1509         ulist_free(roots);
1510 out:
1511         if (!search_commit_root) {
1512                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1513                 btrfs_end_transaction(trans, fs_info->extent_root);
1514         }
1515
1516         return ret;
1517 }
1518
1519 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1520                                 struct btrfs_path *path,
1521                                 iterate_extent_inodes_t *iterate, void *ctx)
1522 {
1523         int ret;
1524         u64 extent_item_pos;
1525         u64 flags = 0;
1526         struct btrfs_key found_key;
1527         int search_commit_root = path->search_commit_root;
1528
1529         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1530         btrfs_release_path(path);
1531         if (ret < 0)
1532                 return ret;
1533         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1534                 return -EINVAL;
1535
1536         extent_item_pos = logical - found_key.objectid;
1537         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1538                                         extent_item_pos, search_commit_root,
1539                                         iterate, ctx);
1540
1541         return ret;
1542 }
1543
1544 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1545                               struct extent_buffer *eb, void *ctx);
1546
1547 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1548                               struct btrfs_path *path,
1549                               iterate_irefs_t *iterate, void *ctx)
1550 {
1551         int ret = 0;
1552         int slot;
1553         u32 cur;
1554         u32 len;
1555         u32 name_len;
1556         u64 parent = 0;
1557         int found = 0;
1558         struct extent_buffer *eb;
1559         struct btrfs_item *item;
1560         struct btrfs_inode_ref *iref;
1561         struct btrfs_key found_key;
1562
1563         while (!ret) {
1564                 path->leave_spinning = 1;
1565                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1566                                      &found_key);
1567                 if (ret < 0)
1568                         break;
1569                 if (ret) {
1570                         ret = found ? 0 : -ENOENT;
1571                         break;
1572                 }
1573                 ++found;
1574
1575                 parent = found_key.offset;
1576                 slot = path->slots[0];
1577                 eb = path->nodes[0];
1578                 /* make sure we can use eb after releasing the path */
1579                 atomic_inc(&eb->refs);
1580                 btrfs_tree_read_lock(eb);
1581                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1582                 btrfs_release_path(path);
1583
1584                 item = btrfs_item_nr(eb, slot);
1585                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1586
1587                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1588                         name_len = btrfs_inode_ref_name_len(eb, iref);
1589                         /* path must be released before calling iterate()! */
1590                         pr_debug("following ref at offset %u for inode %llu in "
1591                                  "tree %llu\n", cur,
1592                                  (unsigned long long)found_key.objectid,
1593                                  (unsigned long long)fs_root->objectid);
1594                         ret = iterate(parent, name_len,
1595                                       (unsigned long)(iref + 1), eb, ctx);
1596                         if (ret)
1597                                 break;
1598                         len = sizeof(*iref) + name_len;
1599                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1600                 }
1601                 btrfs_tree_read_unlock_blocking(eb);
1602                 free_extent_buffer(eb);
1603         }
1604
1605         btrfs_release_path(path);
1606
1607         return ret;
1608 }
1609
1610 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1611                                  struct btrfs_path *path,
1612                                  iterate_irefs_t *iterate, void *ctx)
1613 {
1614         int ret;
1615         int slot;
1616         u64 offset = 0;
1617         u64 parent;
1618         int found = 0;
1619         struct extent_buffer *eb;
1620         struct btrfs_inode_extref *extref;
1621         struct extent_buffer *leaf;
1622         u32 item_size;
1623         u32 cur_offset;
1624         unsigned long ptr;
1625
1626         while (1) {
1627                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1628                                             &offset);
1629                 if (ret < 0)
1630                         break;
1631                 if (ret) {
1632                         ret = found ? 0 : -ENOENT;
1633                         break;
1634                 }
1635                 ++found;
1636
1637                 slot = path->slots[0];
1638                 eb = path->nodes[0];
1639                 /* make sure we can use eb after releasing the path */
1640                 atomic_inc(&eb->refs);
1641
1642                 btrfs_tree_read_lock(eb);
1643                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1644                 btrfs_release_path(path);
1645
1646                 leaf = path->nodes[0];
1647                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
1648                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1649                 cur_offset = 0;
1650
1651                 while (cur_offset < item_size) {
1652                         u32 name_len;
1653
1654                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1655                         parent = btrfs_inode_extref_parent(eb, extref);
1656                         name_len = btrfs_inode_extref_name_len(eb, extref);
1657                         ret = iterate(parent, name_len,
1658                                       (unsigned long)&extref->name, eb, ctx);
1659                         if (ret)
1660                                 break;
1661
1662                         cur_offset += btrfs_inode_extref_name_len(leaf, extref);
1663                         cur_offset += sizeof(*extref);
1664                 }
1665                 btrfs_tree_read_unlock_blocking(eb);
1666                 free_extent_buffer(eb);
1667
1668                 offset++;
1669         }
1670
1671         btrfs_release_path(path);
1672
1673         return ret;
1674 }
1675
1676 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1677                          struct btrfs_path *path, iterate_irefs_t *iterate,
1678                          void *ctx)
1679 {
1680         int ret;
1681         int found_refs = 0;
1682
1683         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1684         if (!ret)
1685                 ++found_refs;
1686         else if (ret != -ENOENT)
1687                 return ret;
1688
1689         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1690         if (ret == -ENOENT && found_refs)
1691                 return 0;
1692
1693         return ret;
1694 }
1695
1696 /*
1697  * returns 0 if the path could be dumped (probably truncated)
1698  * returns <0 in case of an error
1699  */
1700 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1701                          struct extent_buffer *eb, void *ctx)
1702 {
1703         struct inode_fs_paths *ipath = ctx;
1704         char *fspath;
1705         char *fspath_min;
1706         int i = ipath->fspath->elem_cnt;
1707         const int s_ptr = sizeof(char *);
1708         u32 bytes_left;
1709
1710         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1711                                         ipath->fspath->bytes_left - s_ptr : 0;
1712
1713         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1714         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1715                                    name_off, eb, inum, fspath_min, bytes_left);
1716         if (IS_ERR(fspath))
1717                 return PTR_ERR(fspath);
1718
1719         if (fspath > fspath_min) {
1720                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1721                 ++ipath->fspath->elem_cnt;
1722                 ipath->fspath->bytes_left = fspath - fspath_min;
1723         } else {
1724                 ++ipath->fspath->elem_missed;
1725                 ipath->fspath->bytes_missing += fspath_min - fspath;
1726                 ipath->fspath->bytes_left = 0;
1727         }
1728
1729         return 0;
1730 }
1731
1732 /*
1733  * this dumps all file system paths to the inode into the ipath struct, provided
1734  * is has been created large enough. each path is zero-terminated and accessed
1735  * from ipath->fspath->val[i].
1736  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1737  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1738  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1739  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1740  * have been needed to return all paths.
1741  */
1742 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1743 {
1744         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1745                              inode_to_path, ipath);
1746 }
1747
1748 struct btrfs_data_container *init_data_container(u32 total_bytes)
1749 {
1750         struct btrfs_data_container *data;
1751         size_t alloc_bytes;
1752
1753         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1754         data = vmalloc(alloc_bytes);
1755         if (!data)
1756                 return ERR_PTR(-ENOMEM);
1757
1758         if (total_bytes >= sizeof(*data)) {
1759                 data->bytes_left = total_bytes - sizeof(*data);
1760                 data->bytes_missing = 0;
1761         } else {
1762                 data->bytes_missing = sizeof(*data) - total_bytes;
1763                 data->bytes_left = 0;
1764         }
1765
1766         data->elem_cnt = 0;
1767         data->elem_missed = 0;
1768
1769         return data;
1770 }
1771
1772 /*
1773  * allocates space to return multiple file system paths for an inode.
1774  * total_bytes to allocate are passed, note that space usable for actual path
1775  * information will be total_bytes - sizeof(struct inode_fs_paths).
1776  * the returned pointer must be freed with free_ipath() in the end.
1777  */
1778 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1779                                         struct btrfs_path *path)
1780 {
1781         struct inode_fs_paths *ifp;
1782         struct btrfs_data_container *fspath;
1783
1784         fspath = init_data_container(total_bytes);
1785         if (IS_ERR(fspath))
1786                 return (void *)fspath;
1787
1788         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1789         if (!ifp) {
1790                 kfree(fspath);
1791                 return ERR_PTR(-ENOMEM);
1792         }
1793
1794         ifp->btrfs_path = path;
1795         ifp->fspath = fspath;
1796         ifp->fs_root = fs_root;
1797
1798         return ifp;
1799 }
1800
1801 void free_ipath(struct inode_fs_paths *ipath)
1802 {
1803         if (!ipath)
1804                 return;
1805         vfree(ipath->fspath);
1806         kfree(ipath);
1807 }