Btrfs: determine level of old roots
[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                 if (ref->count < 0)
894                         WARN_ON(1);
895                 if (ref->count && ref->root_id && ref->parent == 0) {
896                         /* no parent == root of tree */
897                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
898                         BUG_ON(ret < 0);
899                 }
900                 if (ref->count && ref->parent) {
901                         struct extent_inode_elem *eie = NULL;
902                         if (extent_item_pos && !ref->inode_list) {
903                                 u32 bsz;
904                                 struct extent_buffer *eb;
905                                 bsz = btrfs_level_size(fs_info->extent_root,
906                                                         info_level);
907                                 eb = read_tree_block(fs_info->extent_root,
908                                                            ref->parent, bsz, 0);
909                                 BUG_ON(!eb);
910                                 ret = find_extent_in_eb(eb, bytenr,
911                                                         *extent_item_pos, &eie);
912                                 ref->inode_list = eie;
913                                 free_extent_buffer(eb);
914                         }
915                         ret = ulist_add_merge(refs, ref->parent,
916                                               (uintptr_t)ref->inode_list,
917                                               (u64 *)&eie, GFP_NOFS);
918                         if (!ret && extent_item_pos) {
919                                 /*
920                                  * we've recorded that parent, so we must extend
921                                  * its inode list here
922                                  */
923                                 BUG_ON(!eie);
924                                 while (eie->next)
925                                         eie = eie->next;
926                                 eie->next = ref->inode_list;
927                         }
928                         BUG_ON(ret < 0);
929                 }
930                 kfree(ref);
931         }
932
933 out:
934         btrfs_free_path(path);
935         while (!list_empty(&prefs)) {
936                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
937                 list_del(&ref->list);
938                 kfree(ref);
939         }
940         while (!list_empty(&prefs_delayed)) {
941                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
942                                        list);
943                 list_del(&ref->list);
944                 kfree(ref);
945         }
946
947         return ret;
948 }
949
950 static void free_leaf_list(struct ulist *blocks)
951 {
952         struct ulist_node *node = NULL;
953         struct extent_inode_elem *eie;
954         struct extent_inode_elem *eie_next;
955         struct ulist_iterator uiter;
956
957         ULIST_ITER_INIT(&uiter);
958         while ((node = ulist_next(blocks, &uiter))) {
959                 if (!node->aux)
960                         continue;
961                 eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
962                 for (; eie; eie = eie_next) {
963                         eie_next = eie->next;
964                         kfree(eie);
965                 }
966                 node->aux = 0;
967         }
968
969         ulist_free(blocks);
970 }
971
972 /*
973  * Finds all leafs with a reference to the specified combination of bytenr and
974  * offset. key_list_head will point to a list of corresponding keys (caller must
975  * free each list element). The leafs will be stored in the leafs ulist, which
976  * must be freed with ulist_free.
977  *
978  * returns 0 on success, <0 on error
979  */
980 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
981                                 struct btrfs_fs_info *fs_info, u64 bytenr,
982                                 u64 time_seq, struct ulist **leafs,
983                                 const u64 *extent_item_pos)
984 {
985         struct ulist *tmp;
986         int ret;
987
988         tmp = ulist_alloc(GFP_NOFS);
989         if (!tmp)
990                 return -ENOMEM;
991         *leafs = ulist_alloc(GFP_NOFS);
992         if (!*leafs) {
993                 ulist_free(tmp);
994                 return -ENOMEM;
995         }
996
997         ret = find_parent_nodes(trans, fs_info, bytenr,
998                                 time_seq, *leafs, tmp, extent_item_pos);
999         ulist_free(tmp);
1000
1001         if (ret < 0 && ret != -ENOENT) {
1002                 free_leaf_list(*leafs);
1003                 return ret;
1004         }
1005
1006         return 0;
1007 }
1008
1009 /*
1010  * walk all backrefs for a given extent to find all roots that reference this
1011  * extent. Walking a backref means finding all extents that reference this
1012  * extent and in turn walk the backrefs of those, too. Naturally this is a
1013  * recursive process, but here it is implemented in an iterative fashion: We
1014  * find all referencing extents for the extent in question and put them on a
1015  * list. In turn, we find all referencing extents for those, further appending
1016  * to the list. The way we iterate the list allows adding more elements after
1017  * the current while iterating. The process stops when we reach the end of the
1018  * list. Found roots are added to the roots list.
1019  *
1020  * returns 0 on success, < 0 on error.
1021  */
1022 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1023                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1024                                 u64 time_seq, struct ulist **roots)
1025 {
1026         struct ulist *tmp;
1027         struct ulist_node *node = NULL;
1028         struct ulist_iterator uiter;
1029         int ret;
1030
1031         tmp = ulist_alloc(GFP_NOFS);
1032         if (!tmp)
1033                 return -ENOMEM;
1034         *roots = ulist_alloc(GFP_NOFS);
1035         if (!*roots) {
1036                 ulist_free(tmp);
1037                 return -ENOMEM;
1038         }
1039
1040         ULIST_ITER_INIT(&uiter);
1041         while (1) {
1042                 ret = find_parent_nodes(trans, fs_info, bytenr,
1043                                         time_seq, tmp, *roots, NULL);
1044                 if (ret < 0 && ret != -ENOENT) {
1045                         ulist_free(tmp);
1046                         ulist_free(*roots);
1047                         return ret;
1048                 }
1049                 node = ulist_next(tmp, &uiter);
1050                 if (!node)
1051                         break;
1052                 bytenr = node->val;
1053         }
1054
1055         ulist_free(tmp);
1056         return 0;
1057 }
1058
1059
1060 static int __inode_info(u64 inum, u64 ioff, u8 key_type,
1061                         struct btrfs_root *fs_root, struct btrfs_path *path,
1062                         struct btrfs_key *found_key)
1063 {
1064         int ret;
1065         struct btrfs_key key;
1066         struct extent_buffer *eb;
1067
1068         key.type = key_type;
1069         key.objectid = inum;
1070         key.offset = ioff;
1071
1072         ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
1073         if (ret < 0)
1074                 return ret;
1075
1076         eb = path->nodes[0];
1077         if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
1078                 ret = btrfs_next_leaf(fs_root, path);
1079                 if (ret)
1080                         return ret;
1081                 eb = path->nodes[0];
1082         }
1083
1084         btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
1085         if (found_key->type != key.type || found_key->objectid != key.objectid)
1086                 return 1;
1087
1088         return 0;
1089 }
1090
1091 /*
1092  * this makes the path point to (inum INODE_ITEM ioff)
1093  */
1094 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1095                         struct btrfs_path *path)
1096 {
1097         struct btrfs_key key;
1098         return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
1099                                 &key);
1100 }
1101
1102 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1103                                 struct btrfs_path *path,
1104                                 struct btrfs_key *found_key)
1105 {
1106         return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
1107                                 found_key);
1108 }
1109
1110 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1111                           u64 start_off, struct btrfs_path *path,
1112                           struct btrfs_inode_extref **ret_extref,
1113                           u64 *found_off)
1114 {
1115         int ret, slot;
1116         struct btrfs_key key;
1117         struct btrfs_key found_key;
1118         struct btrfs_inode_extref *extref;
1119         struct extent_buffer *leaf;
1120         unsigned long ptr;
1121
1122         key.objectid = inode_objectid;
1123         btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
1124         key.offset = start_off;
1125
1126         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1127         if (ret < 0)
1128                 return ret;
1129
1130         while (1) {
1131                 leaf = path->nodes[0];
1132                 slot = path->slots[0];
1133                 if (slot >= btrfs_header_nritems(leaf)) {
1134                         /*
1135                          * If the item at offset is not found,
1136                          * btrfs_search_slot will point us to the slot
1137                          * where it should be inserted. In our case
1138                          * that will be the slot directly before the
1139                          * next INODE_REF_KEY_V2 item. In the case
1140                          * that we're pointing to the last slot in a
1141                          * leaf, we must move one leaf over.
1142                          */
1143                         ret = btrfs_next_leaf(root, path);
1144                         if (ret) {
1145                                 if (ret >= 1)
1146                                         ret = -ENOENT;
1147                                 break;
1148                         }
1149                         continue;
1150                 }
1151
1152                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1153
1154                 /*
1155                  * Check that we're still looking at an extended ref key for
1156                  * this particular objectid. If we have different
1157                  * objectid or type then there are no more to be found
1158                  * in the tree and we can exit.
1159                  */
1160                 ret = -ENOENT;
1161                 if (found_key.objectid != inode_objectid)
1162                         break;
1163                 if (btrfs_key_type(&found_key) != BTRFS_INODE_EXTREF_KEY)
1164                         break;
1165
1166                 ret = 0;
1167                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1168                 extref = (struct btrfs_inode_extref *)ptr;
1169                 *ret_extref = extref;
1170                 if (found_off)
1171                         *found_off = found_key.offset;
1172                 break;
1173         }
1174
1175         return ret;
1176 }
1177
1178 static char *ref_to_path(struct btrfs_root *fs_root,
1179                          struct btrfs_path *path,
1180                          u32 name_len, unsigned long name_off,
1181                          struct extent_buffer *eb_in, u64 parent,
1182                          char *dest, u32 size)
1183 {
1184         int slot;
1185         u64 next_inum;
1186         int ret;
1187         s64 bytes_left = size - 1;
1188         struct extent_buffer *eb = eb_in;
1189         struct btrfs_key found_key;
1190         int leave_spinning = path->leave_spinning;
1191         struct btrfs_inode_ref *iref;
1192
1193         if (bytes_left >= 0)
1194                 dest[bytes_left] = '\0';
1195
1196         path->leave_spinning = 1;
1197         while (1) {
1198                 bytes_left -= name_len;
1199                 if (bytes_left >= 0)
1200                         read_extent_buffer(eb, dest + bytes_left,
1201                                            name_off, name_len);
1202                 if (eb != eb_in) {
1203                         btrfs_tree_read_unlock_blocking(eb);
1204                         free_extent_buffer(eb);
1205                 }
1206                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1207                 if (ret > 0)
1208                         ret = -ENOENT;
1209                 if (ret)
1210                         break;
1211
1212                 next_inum = found_key.offset;
1213
1214                 /* regular exit ahead */
1215                 if (parent == next_inum)
1216                         break;
1217
1218                 slot = path->slots[0];
1219                 eb = path->nodes[0];
1220                 /* make sure we can use eb after releasing the path */
1221                 if (eb != eb_in) {
1222                         atomic_inc(&eb->refs);
1223                         btrfs_tree_read_lock(eb);
1224                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1225                 }
1226                 btrfs_release_path(path);
1227                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1228
1229                 name_len = btrfs_inode_ref_name_len(eb, iref);
1230                 name_off = (unsigned long)(iref + 1);
1231
1232                 parent = next_inum;
1233                 --bytes_left;
1234                 if (bytes_left >= 0)
1235                         dest[bytes_left] = '/';
1236         }
1237
1238         btrfs_release_path(path);
1239         path->leave_spinning = leave_spinning;
1240
1241         if (ret)
1242                 return ERR_PTR(ret);
1243
1244         return dest + bytes_left;
1245 }
1246
1247 /*
1248  * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements
1249  * of the path are separated by '/' and the path is guaranteed to be
1250  * 0-terminated. the path is only given within the current file system.
1251  * Therefore, it never starts with a '/'. the caller is responsible to provide
1252  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1253  * the start point of the resulting string is returned. this pointer is within
1254  * dest, normally.
1255  * in case the path buffer would overflow, the pointer is decremented further
1256  * as if output was written to the buffer, though no more output is actually
1257  * generated. that way, the caller can determine how much space would be
1258  * required for the path to fit into the buffer. in that case, the returned
1259  * value will be smaller than dest. callers must check this!
1260  */
1261 char *btrfs_iref_to_path(struct btrfs_root *fs_root,
1262                          struct btrfs_path *path,
1263                          struct btrfs_inode_ref *iref,
1264                          struct extent_buffer *eb_in, u64 parent,
1265                          char *dest, u32 size)
1266 {
1267         return ref_to_path(fs_root, path,
1268                            btrfs_inode_ref_name_len(eb_in, iref),
1269                            (unsigned long)(iref + 1),
1270                            eb_in, parent, dest, size);
1271 }
1272
1273 /*
1274  * this makes the path point to (logical EXTENT_ITEM *)
1275  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1276  * tree blocks and <0 on error.
1277  */
1278 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1279                         struct btrfs_path *path, struct btrfs_key *found_key,
1280                         u64 *flags_ret)
1281 {
1282         int ret;
1283         u64 flags;
1284         u32 item_size;
1285         struct extent_buffer *eb;
1286         struct btrfs_extent_item *ei;
1287         struct btrfs_key key;
1288
1289         key.type = BTRFS_EXTENT_ITEM_KEY;
1290         key.objectid = logical;
1291         key.offset = (u64)-1;
1292
1293         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1294         if (ret < 0)
1295                 return ret;
1296         ret = btrfs_previous_item(fs_info->extent_root, path,
1297                                         0, BTRFS_EXTENT_ITEM_KEY);
1298         if (ret < 0)
1299                 return ret;
1300
1301         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1302         if (found_key->type != BTRFS_EXTENT_ITEM_KEY ||
1303             found_key->objectid > logical ||
1304             found_key->objectid + found_key->offset <= logical) {
1305                 pr_debug("logical %llu is not within any extent\n",
1306                          (unsigned long long)logical);
1307                 return -ENOENT;
1308         }
1309
1310         eb = path->nodes[0];
1311         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1312         BUG_ON(item_size < sizeof(*ei));
1313
1314         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1315         flags = btrfs_extent_flags(eb, ei);
1316
1317         pr_debug("logical %llu is at position %llu within the extent (%llu "
1318                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1319                  (unsigned long long)logical,
1320                  (unsigned long long)(logical - found_key->objectid),
1321                  (unsigned long long)found_key->objectid,
1322                  (unsigned long long)found_key->offset,
1323                  (unsigned long long)flags, item_size);
1324
1325         WARN_ON(!flags_ret);
1326         if (flags_ret) {
1327                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1328                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1329                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1330                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1331                 else
1332                         BUG_ON(1);
1333                 return 0;
1334         }
1335
1336         return -EIO;
1337 }
1338
1339 /*
1340  * helper function to iterate extent inline refs. ptr must point to a 0 value
1341  * for the first call and may be modified. it is used to track state.
1342  * if more refs exist, 0 is returned and the next call to
1343  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1344  * next ref. after the last ref was processed, 1 is returned.
1345  * returns <0 on error
1346  */
1347 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1348                                 struct btrfs_extent_item *ei, u32 item_size,
1349                                 struct btrfs_extent_inline_ref **out_eiref,
1350                                 int *out_type)
1351 {
1352         unsigned long end;
1353         u64 flags;
1354         struct btrfs_tree_block_info *info;
1355
1356         if (!*ptr) {
1357                 /* first call */
1358                 flags = btrfs_extent_flags(eb, ei);
1359                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1360                         info = (struct btrfs_tree_block_info *)(ei + 1);
1361                         *out_eiref =
1362                                 (struct btrfs_extent_inline_ref *)(info + 1);
1363                 } else {
1364                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1365                 }
1366                 *ptr = (unsigned long)*out_eiref;
1367                 if ((void *)*ptr >= (void *)ei + item_size)
1368                         return -ENOENT;
1369         }
1370
1371         end = (unsigned long)ei + item_size;
1372         *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
1373         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1374
1375         *ptr += btrfs_extent_inline_ref_size(*out_type);
1376         WARN_ON(*ptr > end);
1377         if (*ptr == end)
1378                 return 1; /* last */
1379
1380         return 0;
1381 }
1382
1383 /*
1384  * reads the tree block backref for an extent. tree level and root are returned
1385  * through out_level and out_root. ptr must point to a 0 value for the first
1386  * call and may be modified (see __get_extent_inline_ref comment).
1387  * returns 0 if data was provided, 1 if there was no more data to provide or
1388  * <0 on error.
1389  */
1390 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1391                                 struct btrfs_extent_item *ei, u32 item_size,
1392                                 u64 *out_root, u8 *out_level)
1393 {
1394         int ret;
1395         int type;
1396         struct btrfs_tree_block_info *info;
1397         struct btrfs_extent_inline_ref *eiref;
1398
1399         if (*ptr == (unsigned long)-1)
1400                 return 1;
1401
1402         while (1) {
1403                 ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
1404                                                 &eiref, &type);
1405                 if (ret < 0)
1406                         return ret;
1407
1408                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1409                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1410                         break;
1411
1412                 if (ret == 1)
1413                         return 1;
1414         }
1415
1416         /* we can treat both ref types equally here */
1417         info = (struct btrfs_tree_block_info *)(ei + 1);
1418         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1419         *out_level = btrfs_tree_block_level(eb, info);
1420
1421         if (ret == 1)
1422                 *ptr = (unsigned long)-1;
1423
1424         return 0;
1425 }
1426
1427 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1428                                 u64 root, u64 extent_item_objectid,
1429                                 iterate_extent_inodes_t *iterate, void *ctx)
1430 {
1431         struct extent_inode_elem *eie;
1432         int ret = 0;
1433
1434         for (eie = inode_list; eie; eie = eie->next) {
1435                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1436                          "root %llu\n", extent_item_objectid,
1437                          eie->inum, eie->offset, root);
1438                 ret = iterate(eie->inum, eie->offset, root, ctx);
1439                 if (ret) {
1440                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1441                                  extent_item_objectid, ret);
1442                         break;
1443                 }
1444         }
1445
1446         return ret;
1447 }
1448
1449 /*
1450  * calls iterate() for every inode that references the extent identified by
1451  * the given parameters.
1452  * when the iterator function returns a non-zero value, iteration stops.
1453  */
1454 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1455                                 u64 extent_item_objectid, u64 extent_item_pos,
1456                                 int search_commit_root,
1457                                 iterate_extent_inodes_t *iterate, void *ctx)
1458 {
1459         int ret;
1460         struct list_head data_refs = LIST_HEAD_INIT(data_refs);
1461         struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
1462         struct btrfs_trans_handle *trans;
1463         struct ulist *refs = NULL;
1464         struct ulist *roots = NULL;
1465         struct ulist_node *ref_node = NULL;
1466         struct ulist_node *root_node = NULL;
1467         struct seq_list tree_mod_seq_elem = {};
1468         struct ulist_iterator ref_uiter;
1469         struct ulist_iterator root_uiter;
1470
1471         pr_debug("resolving all inodes for extent %llu\n",
1472                         extent_item_objectid);
1473
1474         if (search_commit_root) {
1475                 trans = BTRFS_BACKREF_SEARCH_COMMIT_ROOT;
1476         } else {
1477                 trans = btrfs_join_transaction(fs_info->extent_root);
1478                 if (IS_ERR(trans))
1479                         return PTR_ERR(trans);
1480                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1481         }
1482
1483         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1484                                    tree_mod_seq_elem.seq, &refs,
1485                                    &extent_item_pos);
1486         if (ret)
1487                 goto out;
1488
1489         ULIST_ITER_INIT(&ref_uiter);
1490         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1491                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1492                                            tree_mod_seq_elem.seq, &roots);
1493                 if (ret)
1494                         break;
1495                 ULIST_ITER_INIT(&root_uiter);
1496                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1497                         pr_debug("root %llu references leaf %llu, data list "
1498                                  "%#llx\n", root_node->val, ref_node->val,
1499                                  (long long)ref_node->aux);
1500                         ret = iterate_leaf_refs((struct extent_inode_elem *)
1501                                                 (uintptr_t)ref_node->aux,
1502                                                 root_node->val,
1503                                                 extent_item_objectid,
1504                                                 iterate, ctx);
1505                 }
1506                 ulist_free(roots);
1507                 roots = NULL;
1508         }
1509
1510         free_leaf_list(refs);
1511         ulist_free(roots);
1512 out:
1513         if (!search_commit_root) {
1514                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1515                 btrfs_end_transaction(trans, fs_info->extent_root);
1516         }
1517
1518         return ret;
1519 }
1520
1521 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1522                                 struct btrfs_path *path,
1523                                 iterate_extent_inodes_t *iterate, void *ctx)
1524 {
1525         int ret;
1526         u64 extent_item_pos;
1527         u64 flags = 0;
1528         struct btrfs_key found_key;
1529         int search_commit_root = path->search_commit_root;
1530
1531         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1532         btrfs_release_path(path);
1533         if (ret < 0)
1534                 return ret;
1535         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1536                 return -EINVAL;
1537
1538         extent_item_pos = logical - found_key.objectid;
1539         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1540                                         extent_item_pos, search_commit_root,
1541                                         iterate, ctx);
1542
1543         return ret;
1544 }
1545
1546 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1547                               struct extent_buffer *eb, void *ctx);
1548
1549 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1550                               struct btrfs_path *path,
1551                               iterate_irefs_t *iterate, void *ctx)
1552 {
1553         int ret = 0;
1554         int slot;
1555         u32 cur;
1556         u32 len;
1557         u32 name_len;
1558         u64 parent = 0;
1559         int found = 0;
1560         struct extent_buffer *eb;
1561         struct btrfs_item *item;
1562         struct btrfs_inode_ref *iref;
1563         struct btrfs_key found_key;
1564
1565         while (!ret) {
1566                 path->leave_spinning = 1;
1567                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1568                                      &found_key);
1569                 if (ret < 0)
1570                         break;
1571                 if (ret) {
1572                         ret = found ? 0 : -ENOENT;
1573                         break;
1574                 }
1575                 ++found;
1576
1577                 parent = found_key.offset;
1578                 slot = path->slots[0];
1579                 eb = path->nodes[0];
1580                 /* make sure we can use eb after releasing the path */
1581                 atomic_inc(&eb->refs);
1582                 btrfs_tree_read_lock(eb);
1583                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1584                 btrfs_release_path(path);
1585
1586                 item = btrfs_item_nr(eb, slot);
1587                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1588
1589                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1590                         name_len = btrfs_inode_ref_name_len(eb, iref);
1591                         /* path must be released before calling iterate()! */
1592                         pr_debug("following ref at offset %u for inode %llu in "
1593                                  "tree %llu\n", cur,
1594                                  (unsigned long long)found_key.objectid,
1595                                  (unsigned long long)fs_root->objectid);
1596                         ret = iterate(parent, name_len,
1597                                       (unsigned long)(iref + 1), eb, ctx);
1598                         if (ret)
1599                                 break;
1600                         len = sizeof(*iref) + name_len;
1601                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1602                 }
1603                 btrfs_tree_read_unlock_blocking(eb);
1604                 free_extent_buffer(eb);
1605         }
1606
1607         btrfs_release_path(path);
1608
1609         return ret;
1610 }
1611
1612 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1613                                  struct btrfs_path *path,
1614                                  iterate_irefs_t *iterate, void *ctx)
1615 {
1616         int ret;
1617         int slot;
1618         u64 offset = 0;
1619         u64 parent;
1620         int found = 0;
1621         struct extent_buffer *eb;
1622         struct btrfs_inode_extref *extref;
1623         struct extent_buffer *leaf;
1624         u32 item_size;
1625         u32 cur_offset;
1626         unsigned long ptr;
1627
1628         while (1) {
1629                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1630                                             &offset);
1631                 if (ret < 0)
1632                         break;
1633                 if (ret) {
1634                         ret = found ? 0 : -ENOENT;
1635                         break;
1636                 }
1637                 ++found;
1638
1639                 slot = path->slots[0];
1640                 eb = path->nodes[0];
1641                 /* make sure we can use eb after releasing the path */
1642                 atomic_inc(&eb->refs);
1643
1644                 btrfs_tree_read_lock(eb);
1645                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1646                 btrfs_release_path(path);
1647
1648                 leaf = path->nodes[0];
1649                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
1650                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1651                 cur_offset = 0;
1652
1653                 while (cur_offset < item_size) {
1654                         u32 name_len;
1655
1656                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1657                         parent = btrfs_inode_extref_parent(eb, extref);
1658                         name_len = btrfs_inode_extref_name_len(eb, extref);
1659                         ret = iterate(parent, name_len,
1660                                       (unsigned long)&extref->name, eb, ctx);
1661                         if (ret)
1662                                 break;
1663
1664                         cur_offset += btrfs_inode_extref_name_len(leaf, extref);
1665                         cur_offset += sizeof(*extref);
1666                 }
1667                 btrfs_tree_read_unlock_blocking(eb);
1668                 free_extent_buffer(eb);
1669
1670                 offset++;
1671         }
1672
1673         btrfs_release_path(path);
1674
1675         return ret;
1676 }
1677
1678 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1679                          struct btrfs_path *path, iterate_irefs_t *iterate,
1680                          void *ctx)
1681 {
1682         int ret;
1683         int found_refs = 0;
1684
1685         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1686         if (!ret)
1687                 ++found_refs;
1688         else if (ret != -ENOENT)
1689                 return ret;
1690
1691         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1692         if (ret == -ENOENT && found_refs)
1693                 return 0;
1694
1695         return ret;
1696 }
1697
1698 /*
1699  * returns 0 if the path could be dumped (probably truncated)
1700  * returns <0 in case of an error
1701  */
1702 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1703                          struct extent_buffer *eb, void *ctx)
1704 {
1705         struct inode_fs_paths *ipath = ctx;
1706         char *fspath;
1707         char *fspath_min;
1708         int i = ipath->fspath->elem_cnt;
1709         const int s_ptr = sizeof(char *);
1710         u32 bytes_left;
1711
1712         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1713                                         ipath->fspath->bytes_left - s_ptr : 0;
1714
1715         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1716         fspath = ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1717                              name_off, eb, inum, fspath_min,
1718                              bytes_left);
1719         if (IS_ERR(fspath))
1720                 return PTR_ERR(fspath);
1721
1722         if (fspath > fspath_min) {
1723                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1724                 ++ipath->fspath->elem_cnt;
1725                 ipath->fspath->bytes_left = fspath - fspath_min;
1726         } else {
1727                 ++ipath->fspath->elem_missed;
1728                 ipath->fspath->bytes_missing += fspath_min - fspath;
1729                 ipath->fspath->bytes_left = 0;
1730         }
1731
1732         return 0;
1733 }
1734
1735 /*
1736  * this dumps all file system paths to the inode into the ipath struct, provided
1737  * is has been created large enough. each path is zero-terminated and accessed
1738  * from ipath->fspath->val[i].
1739  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1740  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1741  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1742  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1743  * have been needed to return all paths.
1744  */
1745 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1746 {
1747         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1748                              inode_to_path, ipath);
1749 }
1750
1751 struct btrfs_data_container *init_data_container(u32 total_bytes)
1752 {
1753         struct btrfs_data_container *data;
1754         size_t alloc_bytes;
1755
1756         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1757         data = vmalloc(alloc_bytes);
1758         if (!data)
1759                 return ERR_PTR(-ENOMEM);
1760
1761         if (total_bytes >= sizeof(*data)) {
1762                 data->bytes_left = total_bytes - sizeof(*data);
1763                 data->bytes_missing = 0;
1764         } else {
1765                 data->bytes_missing = sizeof(*data) - total_bytes;
1766                 data->bytes_left = 0;
1767         }
1768
1769         data->elem_cnt = 0;
1770         data->elem_missed = 0;
1771
1772         return data;
1773 }
1774
1775 /*
1776  * allocates space to return multiple file system paths for an inode.
1777  * total_bytes to allocate are passed, note that space usable for actual path
1778  * information will be total_bytes - sizeof(struct inode_fs_paths).
1779  * the returned pointer must be freed with free_ipath() in the end.
1780  */
1781 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1782                                         struct btrfs_path *path)
1783 {
1784         struct inode_fs_paths *ifp;
1785         struct btrfs_data_container *fspath;
1786
1787         fspath = init_data_container(total_bytes);
1788         if (IS_ERR(fspath))
1789                 return (void *)fspath;
1790
1791         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1792         if (!ifp) {
1793                 kfree(fspath);
1794                 return ERR_PTR(-ENOMEM);
1795         }
1796
1797         ifp->btrfs_path = path;
1798         ifp->fspath = fspath;
1799         ifp->fs_root = fs_root;
1800
1801         return ifp;
1802 }
1803
1804 void free_ipath(struct inode_fs_paths *ipath)
1805 {
1806         if (!ipath)
1807                 return;
1808         vfree(ipath->fspath);
1809         kfree(ipath);
1810 }