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TOMOYO Linux Cross Reference
Linux/fs/btrfs/backref.c

Version: ~ [ linux-5.2 ] ~ [ linux-5.1.16 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.57 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.132 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.184 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.184 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.69 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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  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 /* Just an arbitrary number so we can be sure this happened */
 29 #define BACKREF_FOUND_SHARED 6
 30 
 31 struct extent_inode_elem {
 32         u64 inum;
 33         u64 offset;
 34         struct extent_inode_elem *next;
 35 };
 36 
 37 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
 38                                 struct btrfs_file_extent_item *fi,
 39                                 u64 extent_item_pos,
 40                                 struct extent_inode_elem **eie)
 41 {
 42         u64 offset = 0;
 43         struct extent_inode_elem *e;
 44 
 45         if (!btrfs_file_extent_compression(eb, fi) &&
 46             !btrfs_file_extent_encryption(eb, fi) &&
 47             !btrfs_file_extent_other_encoding(eb, fi)) {
 48                 u64 data_offset;
 49                 u64 data_len;
 50 
 51                 data_offset = btrfs_file_extent_offset(eb, fi);
 52                 data_len = btrfs_file_extent_num_bytes(eb, fi);
 53 
 54                 if (extent_item_pos < data_offset ||
 55                     extent_item_pos >= data_offset + data_len)
 56                         return 1;
 57                 offset = extent_item_pos - data_offset;
 58         }
 59 
 60         e = kmalloc(sizeof(*e), GFP_NOFS);
 61         if (!e)
 62                 return -ENOMEM;
 63 
 64         e->next = *eie;
 65         e->inum = key->objectid;
 66         e->offset = key->offset + offset;
 67         *eie = e;
 68 
 69         return 0;
 70 }
 71 
 72 static void free_inode_elem_list(struct extent_inode_elem *eie)
 73 {
 74         struct extent_inode_elem *eie_next;
 75 
 76         for (; eie; eie = eie_next) {
 77                 eie_next = eie->next;
 78                 kfree(eie);
 79         }
 80 }
 81 
 82 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
 83                                 u64 extent_item_pos,
 84                                 struct extent_inode_elem **eie)
 85 {
 86         u64 disk_byte;
 87         struct btrfs_key key;
 88         struct btrfs_file_extent_item *fi;
 89         int slot;
 90         int nritems;
 91         int extent_type;
 92         int ret;
 93 
 94         /*
 95          * from the shared data ref, we only have the leaf but we need
 96          * the key. thus, we must look into all items and see that we
 97          * find one (some) with a reference to our extent item.
 98          */
 99         nritems = btrfs_header_nritems(eb);
100         for (slot = 0; slot < nritems; ++slot) {
101                 btrfs_item_key_to_cpu(eb, &key, slot);
102                 if (key.type != BTRFS_EXTENT_DATA_KEY)
103                         continue;
104                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
105                 extent_type = btrfs_file_extent_type(eb, fi);
106                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
107                         continue;
108                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
109                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
110                 if (disk_byte != wanted_disk_byte)
111                         continue;
112 
113                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
114                 if (ret < 0)
115                         return ret;
116         }
117 
118         return 0;
119 }
120 
121 /*
122  * this structure records all encountered refs on the way up to the root
123  */
124 struct __prelim_ref {
125         struct list_head list;
126         u64 root_id;
127         struct btrfs_key key_for_search;
128         int level;
129         int count;
130         struct extent_inode_elem *inode_list;
131         u64 parent;
132         u64 wanted_disk_byte;
133 };
134 
135 static struct kmem_cache *btrfs_prelim_ref_cache;
136 
137 int __init btrfs_prelim_ref_init(void)
138 {
139         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
140                                         sizeof(struct __prelim_ref),
141                                         0,
142                                         SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
143                                         NULL);
144         if (!btrfs_prelim_ref_cache)
145                 return -ENOMEM;
146         return 0;
147 }
148 
149 void btrfs_prelim_ref_exit(void)
150 {
151         if (btrfs_prelim_ref_cache)
152                 kmem_cache_destroy(btrfs_prelim_ref_cache);
153 }
154 
155 /*
156  * the rules for all callers of this function are:
157  * - obtaining the parent is the goal
158  * - if you add a key, you must know that it is a correct key
159  * - if you cannot add the parent or a correct key, then we will look into the
160  *   block later to set a correct key
161  *
162  * delayed refs
163  * ============
164  *        backref type | shared | indirect | shared | indirect
165  * information         |   tree |     tree |   data |     data
166  * --------------------+--------+----------+--------+----------
167  *      parent logical |    y   |     -    |    -   |     -
168  *      key to resolve |    -   |     y    |    y   |     y
169  *  tree block logical |    -   |     -    |    -   |     -
170  *  root for resolving |    y   |     y    |    y   |     y
171  *
172  * - column 1:       we've the parent -> done
173  * - column 2, 3, 4: we use the key to find the parent
174  *
175  * on disk refs (inline or keyed)
176  * ==============================
177  *        backref type | shared | indirect | shared | indirect
178  * information         |   tree |     tree |   data |     data
179  * --------------------+--------+----------+--------+----------
180  *      parent logical |    y   |     -    |    y   |     -
181  *      key to resolve |    -   |     -    |    -   |     y
182  *  tree block logical |    y   |     y    |    y   |     y
183  *  root for resolving |    -   |     y    |    y   |     y
184  *
185  * - column 1, 3: we've the parent -> done
186  * - column 2:    we take the first key from the block to find the parent
187  *                (see __add_missing_keys)
188  * - column 4:    we use the key to find the parent
189  *
190  * additional information that's available but not required to find the parent
191  * block might help in merging entries to gain some speed.
192  */
193 
194 static int __add_prelim_ref(struct list_head *head, u64 root_id,
195                             struct btrfs_key *key, int level,
196                             u64 parent, u64 wanted_disk_byte, int count,
197                             gfp_t gfp_mask)
198 {
199         struct __prelim_ref *ref;
200 
201         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
202                 return 0;
203 
204         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
205         if (!ref)
206                 return -ENOMEM;
207 
208         ref->root_id = root_id;
209         if (key) {
210                 ref->key_for_search = *key;
211                 /*
212                  * We can often find data backrefs with an offset that is too
213                  * large (>= LLONG_MAX, maximum allowed file offset) due to
214                  * underflows when subtracting a file's offset with the data
215                  * offset of its corresponding extent data item. This can
216                  * happen for example in the clone ioctl.
217                  * So if we detect such case we set the search key's offset to
218                  * zero to make sure we will find the matching file extent item
219                  * at add_all_parents(), otherwise we will miss it because the
220                  * offset taken form the backref is much larger then the offset
221                  * of the file extent item. This can make us scan a very large
222                  * number of file extent items, but at least it will not make
223                  * us miss any.
224                  * This is an ugly workaround for a behaviour that should have
225                  * never existed, but it does and a fix for the clone ioctl
226                  * would touch a lot of places, cause backwards incompatibility
227                  * and would not fix the problem for extents cloned with older
228                  * kernels.
229                  */
230                 if (ref->key_for_search.type == BTRFS_EXTENT_DATA_KEY &&
231                     ref->key_for_search.offset >= LLONG_MAX)
232                         ref->key_for_search.offset = 0;
233         } else {
234                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
235         }
236 
237         ref->inode_list = NULL;
238         ref->level = level;
239         ref->count = count;
240         ref->parent = parent;
241         ref->wanted_disk_byte = wanted_disk_byte;
242         list_add_tail(&ref->list, head);
243 
244         return 0;
245 }
246 
247 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
248                            struct ulist *parents, struct __prelim_ref *ref,
249                            int level, u64 time_seq, const u64 *extent_item_pos,
250                            u64 total_refs)
251 {
252         int ret = 0;
253         int slot;
254         struct extent_buffer *eb;
255         struct btrfs_key key;
256         struct btrfs_key *key_for_search = &ref->key_for_search;
257         struct btrfs_file_extent_item *fi;
258         struct extent_inode_elem *eie = NULL, *old = NULL;
259         u64 disk_byte;
260         u64 wanted_disk_byte = ref->wanted_disk_byte;
261         u64 count = 0;
262 
263         if (level != 0) {
264                 eb = path->nodes[level];
265                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
266                 if (ret < 0)
267                         return ret;
268                 return 0;
269         }
270 
271         /*
272          * We normally enter this function with the path already pointing to
273          * the first item to check. But sometimes, we may enter it with
274          * slot==nritems. In that case, go to the next leaf before we continue.
275          */
276         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
277                 if (time_seq == (u64)-1)
278                         ret = btrfs_next_leaf(root, path);
279                 else
280                         ret = btrfs_next_old_leaf(root, path, time_seq);
281         }
282 
283         while (!ret && count < total_refs) {
284                 eb = path->nodes[0];
285                 slot = path->slots[0];
286 
287                 btrfs_item_key_to_cpu(eb, &key, slot);
288 
289                 if (key.objectid != key_for_search->objectid ||
290                     key.type != BTRFS_EXTENT_DATA_KEY)
291                         break;
292 
293                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
294                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
295 
296                 if (disk_byte == wanted_disk_byte) {
297                         eie = NULL;
298                         old = NULL;
299                         count++;
300                         if (extent_item_pos) {
301                                 ret = check_extent_in_eb(&key, eb, fi,
302                                                 *extent_item_pos,
303                                                 &eie);
304                                 if (ret < 0)
305                                         break;
306                         }
307                         if (ret > 0)
308                                 goto next;
309                         ret = ulist_add_merge_ptr(parents, eb->start,
310                                                   eie, (void **)&old, GFP_NOFS);
311                         if (ret < 0)
312                                 break;
313                         if (!ret && extent_item_pos) {
314                                 while (old->next)
315                                         old = old->next;
316                                 old->next = eie;
317                         }
318                         eie = NULL;
319                 }
320 next:
321                 if (time_seq == (u64)-1)
322                         ret = btrfs_next_item(root, path);
323                 else
324                         ret = btrfs_next_old_item(root, path, time_seq);
325         }
326 
327         if (ret > 0)
328                 ret = 0;
329         else if (ret < 0)
330                 free_inode_elem_list(eie);
331         return ret;
332 }
333 
334 /*
335  * resolve an indirect backref in the form (root_id, key, level)
336  * to a logical address
337  */
338 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
339                                   struct btrfs_path *path, u64 time_seq,
340                                   struct __prelim_ref *ref,
341                                   struct ulist *parents,
342                                   const u64 *extent_item_pos, u64 total_refs)
343 {
344         struct btrfs_root *root;
345         struct btrfs_key root_key;
346         struct extent_buffer *eb;
347         int ret = 0;
348         int root_level;
349         int level = ref->level;
350         int index;
351 
352         root_key.objectid = ref->root_id;
353         root_key.type = BTRFS_ROOT_ITEM_KEY;
354         root_key.offset = (u64)-1;
355 
356         index = srcu_read_lock(&fs_info->subvol_srcu);
357 
358         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
359         if (IS_ERR(root)) {
360                 srcu_read_unlock(&fs_info->subvol_srcu, index);
361                 ret = PTR_ERR(root);
362                 goto out;
363         }
364 
365         if (path->search_commit_root)
366                 root_level = btrfs_header_level(root->commit_root);
367         else if (time_seq == (u64)-1)
368                 root_level = btrfs_header_level(root->node);
369         else
370                 root_level = btrfs_old_root_level(root, time_seq);
371 
372         if (root_level + 1 == level) {
373                 srcu_read_unlock(&fs_info->subvol_srcu, index);
374                 goto out;
375         }
376 
377         path->lowest_level = level;
378         if (time_seq == (u64)-1)
379                 ret = btrfs_search_slot(NULL, root, &ref->key_for_search, path,
380                                         0, 0);
381         else
382                 ret = btrfs_search_old_slot(root, &ref->key_for_search, path,
383                                             time_seq);
384 
385         /* root node has been locked, we can release @subvol_srcu safely here */
386         srcu_read_unlock(&fs_info->subvol_srcu, index);
387 
388         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
389                  "%d for key (%llu %u %llu)\n",
390                  ref->root_id, level, ref->count, ret,
391                  ref->key_for_search.objectid, ref->key_for_search.type,
392                  ref->key_for_search.offset);
393         if (ret < 0)
394                 goto out;
395 
396         eb = path->nodes[level];
397         while (!eb) {
398                 if (WARN_ON(!level)) {
399                         ret = 1;
400                         goto out;
401                 }
402                 level--;
403                 eb = path->nodes[level];
404         }
405 
406         ret = add_all_parents(root, path, parents, ref, level, time_seq,
407                               extent_item_pos, total_refs);
408 out:
409         path->lowest_level = 0;
410         btrfs_release_path(path);
411         return ret;
412 }
413 
414 /*
415  * resolve all indirect backrefs from the list
416  */
417 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
418                                    struct btrfs_path *path, u64 time_seq,
419                                    struct list_head *head,
420                                    const u64 *extent_item_pos, u64 total_refs,
421                                    u64 root_objectid)
422 {
423         int err;
424         int ret = 0;
425         struct __prelim_ref *ref;
426         struct __prelim_ref *ref_safe;
427         struct __prelim_ref *new_ref;
428         struct ulist *parents;
429         struct ulist_node *node;
430         struct ulist_iterator uiter;
431 
432         parents = ulist_alloc(GFP_NOFS);
433         if (!parents)
434                 return -ENOMEM;
435 
436         /*
437          * _safe allows us to insert directly after the current item without
438          * iterating over the newly inserted items.
439          * we're also allowed to re-assign ref during iteration.
440          */
441         list_for_each_entry_safe(ref, ref_safe, head, list) {
442                 if (ref->parent)        /* already direct */
443                         continue;
444                 if (ref->count == 0)
445                         continue;
446                 if (root_objectid && ref->root_id != root_objectid) {
447                         ret = BACKREF_FOUND_SHARED;
448                         goto out;
449                 }
450                 err = __resolve_indirect_ref(fs_info, path, time_seq, ref,
451                                              parents, extent_item_pos,
452                                              total_refs);
453                 /*
454                  * we can only tolerate ENOENT,otherwise,we should catch error
455                  * and return directly.
456                  */
457                 if (err == -ENOENT) {
458                         continue;
459                 } else if (err) {
460                         ret = err;
461                         goto out;
462                 }
463 
464                 /* we put the first parent into the ref at hand */
465                 ULIST_ITER_INIT(&uiter);
466                 node = ulist_next(parents, &uiter);
467                 ref->parent = node ? node->val : 0;
468                 ref->inode_list = node ?
469                         (struct extent_inode_elem *)(uintptr_t)node->aux : NULL;
470 
471                 /* additional parents require new refs being added here */
472                 while ((node = ulist_next(parents, &uiter))) {
473                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
474                                                    GFP_NOFS);
475                         if (!new_ref) {
476                                 ret = -ENOMEM;
477                                 goto out;
478                         }
479                         memcpy(new_ref, ref, sizeof(*ref));
480                         new_ref->parent = node->val;
481                         new_ref->inode_list = (struct extent_inode_elem *)
482                                                         (uintptr_t)node->aux;
483                         list_add(&new_ref->list, &ref->list);
484                 }
485                 ulist_reinit(parents);
486         }
487 out:
488         ulist_free(parents);
489         return ret;
490 }
491 
492 static inline int ref_for_same_block(struct __prelim_ref *ref1,
493                                      struct __prelim_ref *ref2)
494 {
495         if (ref1->level != ref2->level)
496                 return 0;
497         if (ref1->root_id != ref2->root_id)
498                 return 0;
499         if (ref1->key_for_search.type != ref2->key_for_search.type)
500                 return 0;
501         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
502                 return 0;
503         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
504                 return 0;
505         if (ref1->parent != ref2->parent)
506                 return 0;
507 
508         return 1;
509 }
510 
511 /*
512  * read tree blocks and add keys where required.
513  */
514 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
515                               struct list_head *head)
516 {
517         struct list_head *pos;
518         struct extent_buffer *eb;
519 
520         list_for_each(pos, head) {
521                 struct __prelim_ref *ref;
522                 ref = list_entry(pos, struct __prelim_ref, list);
523 
524                 if (ref->parent)
525                         continue;
526                 if (ref->key_for_search.type)
527                         continue;
528                 BUG_ON(!ref->wanted_disk_byte);
529                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
530                                      0);
531                 if (IS_ERR(eb)) {
532                         return PTR_ERR(eb);
533                 } else if (!extent_buffer_uptodate(eb)) {
534                         free_extent_buffer(eb);
535                         return -EIO;
536                 }
537                 btrfs_tree_read_lock(eb);
538                 if (btrfs_header_level(eb) == 0)
539                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
540                 else
541                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
542                 btrfs_tree_read_unlock(eb);
543                 free_extent_buffer(eb);
544         }
545         return 0;
546 }
547 
548 /*
549  * merge backrefs and adjust counts accordingly
550  *
551  * mode = 1: merge identical keys, if key is set
552  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
553  *           additionally, we could even add a key range for the blocks we
554  *           looked into to merge even more (-> replace unresolved refs by those
555  *           having a parent).
556  * mode = 2: merge identical parents
557  */
558 static void __merge_refs(struct list_head *head, int mode)
559 {
560         struct list_head *pos1;
561 
562         list_for_each(pos1, head) {
563                 struct list_head *n2;
564                 struct list_head *pos2;
565                 struct __prelim_ref *ref1;
566 
567                 ref1 = list_entry(pos1, struct __prelim_ref, list);
568 
569                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
570                      pos2 = n2, n2 = pos2->next) {
571                         struct __prelim_ref *ref2;
572                         struct __prelim_ref *xchg;
573                         struct extent_inode_elem *eie;
574 
575                         ref2 = list_entry(pos2, struct __prelim_ref, list);
576 
577                         if (!ref_for_same_block(ref1, ref2))
578                                 continue;
579                         if (mode == 1) {
580                                 if (!ref1->parent && ref2->parent) {
581                                         xchg = ref1;
582                                         ref1 = ref2;
583                                         ref2 = xchg;
584                                 }
585                         } else {
586                                 if (ref1->parent != ref2->parent)
587                                         continue;
588                         }
589 
590                         eie = ref1->inode_list;
591                         while (eie && eie->next)
592                                 eie = eie->next;
593                         if (eie)
594                                 eie->next = ref2->inode_list;
595                         else
596                                 ref1->inode_list = ref2->inode_list;
597                         ref1->count += ref2->count;
598 
599                         list_del(&ref2->list);
600                         kmem_cache_free(btrfs_prelim_ref_cache, ref2);
601                 }
602 
603         }
604 }
605 
606 /*
607  * add all currently queued delayed refs from this head whose seq nr is
608  * smaller or equal that seq to the list
609  */
610 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
611                               struct list_head *prefs, u64 *total_refs,
612                               u64 inum)
613 {
614         struct btrfs_delayed_ref_node *node;
615         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
616         struct btrfs_key key;
617         struct btrfs_key op_key = {0};
618         int sgn;
619         int ret = 0;
620 
621         if (extent_op && extent_op->update_key)
622                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
623 
624         spin_lock(&head->lock);
625         list_for_each_entry(node, &head->ref_list, list) {
626                 if (node->seq > seq)
627                         continue;
628 
629                 switch (node->action) {
630                 case BTRFS_ADD_DELAYED_EXTENT:
631                 case BTRFS_UPDATE_DELAYED_HEAD:
632                         WARN_ON(1);
633                         continue;
634                 case BTRFS_ADD_DELAYED_REF:
635                         sgn = 1;
636                         break;
637                 case BTRFS_DROP_DELAYED_REF:
638                         sgn = -1;
639                         break;
640                 default:
641                         BUG_ON(1);
642                 }
643                 *total_refs += (node->ref_mod * sgn);
644                 switch (node->type) {
645                 case BTRFS_TREE_BLOCK_REF_KEY: {
646                         struct btrfs_delayed_tree_ref *ref;
647 
648                         ref = btrfs_delayed_node_to_tree_ref(node);
649                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
650                                                ref->level + 1, 0, node->bytenr,
651                                                node->ref_mod * sgn, GFP_ATOMIC);
652                         break;
653                 }
654                 case BTRFS_SHARED_BLOCK_REF_KEY: {
655                         struct btrfs_delayed_tree_ref *ref;
656 
657                         ref = btrfs_delayed_node_to_tree_ref(node);
658                         ret = __add_prelim_ref(prefs, 0, NULL,
659                                                ref->level + 1, ref->parent,
660                                                node->bytenr,
661                                                node->ref_mod * sgn, GFP_ATOMIC);
662                         break;
663                 }
664                 case BTRFS_EXTENT_DATA_REF_KEY: {
665                         struct btrfs_delayed_data_ref *ref;
666                         ref = btrfs_delayed_node_to_data_ref(node);
667 
668                         key.objectid = ref->objectid;
669                         key.type = BTRFS_EXTENT_DATA_KEY;
670                         key.offset = ref->offset;
671 
672                         /*
673                          * Found a inum that doesn't match our known inum, we
674                          * know it's shared.
675                          */
676                         if (inum && ref->objectid != inum) {
677                                 ret = BACKREF_FOUND_SHARED;
678                                 break;
679                         }
680 
681                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
682                                                node->bytenr,
683                                                node->ref_mod * sgn, GFP_ATOMIC);
684                         break;
685                 }
686                 case BTRFS_SHARED_DATA_REF_KEY: {
687                         struct btrfs_delayed_data_ref *ref;
688 
689                         ref = btrfs_delayed_node_to_data_ref(node);
690                         ret = __add_prelim_ref(prefs, 0, NULL, 0,
691                                                ref->parent, node->bytenr,
692                                                node->ref_mod * sgn, GFP_ATOMIC);
693                         break;
694                 }
695                 default:
696                         WARN_ON(1);
697                 }
698                 if (ret)
699                         break;
700         }
701         spin_unlock(&head->lock);
702         return ret;
703 }
704 
705 /*
706  * add all inline backrefs for bytenr to the list
707  */
708 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
709                              struct btrfs_path *path, u64 bytenr,
710                              int *info_level, struct list_head *prefs,
711                              u64 *total_refs, u64 inum)
712 {
713         int ret = 0;
714         int slot;
715         struct extent_buffer *leaf;
716         struct btrfs_key key;
717         struct btrfs_key found_key;
718         unsigned long ptr;
719         unsigned long end;
720         struct btrfs_extent_item *ei;
721         u64 flags;
722         u64 item_size;
723 
724         /*
725          * enumerate all inline refs
726          */
727         leaf = path->nodes[0];
728         slot = path->slots[0];
729 
730         item_size = btrfs_item_size_nr(leaf, slot);
731         BUG_ON(item_size < sizeof(*ei));
732 
733         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
734         flags = btrfs_extent_flags(leaf, ei);
735         *total_refs += btrfs_extent_refs(leaf, ei);
736         btrfs_item_key_to_cpu(leaf, &found_key, slot);
737 
738         ptr = (unsigned long)(ei + 1);
739         end = (unsigned long)ei + item_size;
740 
741         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
742             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
743                 struct btrfs_tree_block_info *info;
744 
745                 info = (struct btrfs_tree_block_info *)ptr;
746                 *info_level = btrfs_tree_block_level(leaf, info);
747                 ptr += sizeof(struct btrfs_tree_block_info);
748                 BUG_ON(ptr > end);
749         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
750                 *info_level = found_key.offset;
751         } else {
752                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
753         }
754 
755         while (ptr < end) {
756                 struct btrfs_extent_inline_ref *iref;
757                 u64 offset;
758                 int type;
759 
760                 iref = (struct btrfs_extent_inline_ref *)ptr;
761                 type = btrfs_extent_inline_ref_type(leaf, iref);
762                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
763 
764                 switch (type) {
765                 case BTRFS_SHARED_BLOCK_REF_KEY:
766                         ret = __add_prelim_ref(prefs, 0, NULL,
767                                                 *info_level + 1, offset,
768                                                 bytenr, 1, GFP_NOFS);
769                         break;
770                 case BTRFS_SHARED_DATA_REF_KEY: {
771                         struct btrfs_shared_data_ref *sdref;
772                         int count;
773 
774                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
775                         count = btrfs_shared_data_ref_count(leaf, sdref);
776                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
777                                                bytenr, count, GFP_NOFS);
778                         break;
779                 }
780                 case BTRFS_TREE_BLOCK_REF_KEY:
781                         ret = __add_prelim_ref(prefs, offset, NULL,
782                                                *info_level + 1, 0,
783                                                bytenr, 1, GFP_NOFS);
784                         break;
785                 case BTRFS_EXTENT_DATA_REF_KEY: {
786                         struct btrfs_extent_data_ref *dref;
787                         int count;
788                         u64 root;
789 
790                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
791                         count = btrfs_extent_data_ref_count(leaf, dref);
792                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
793                                                                       dref);
794                         key.type = BTRFS_EXTENT_DATA_KEY;
795                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
796 
797                         if (inum && key.objectid != inum) {
798                                 ret = BACKREF_FOUND_SHARED;
799                                 break;
800                         }
801 
802                         root = btrfs_extent_data_ref_root(leaf, dref);
803                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
804                                                bytenr, count, GFP_NOFS);
805                         break;
806                 }
807                 default:
808                         WARN_ON(1);
809                 }
810                 if (ret)
811                         return ret;
812                 ptr += btrfs_extent_inline_ref_size(type);
813         }
814 
815         return 0;
816 }
817 
818 /*
819  * add all non-inline backrefs for bytenr to the list
820  */
821 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
822                             struct btrfs_path *path, u64 bytenr,
823                             int info_level, struct list_head *prefs, u64 inum)
824 {
825         struct btrfs_root *extent_root = fs_info->extent_root;
826         int ret;
827         int slot;
828         struct extent_buffer *leaf;
829         struct btrfs_key key;
830 
831         while (1) {
832                 ret = btrfs_next_item(extent_root, path);
833                 if (ret < 0)
834                         break;
835                 if (ret) {
836                         ret = 0;
837                         break;
838                 }
839 
840                 slot = path->slots[0];
841                 leaf = path->nodes[0];
842                 btrfs_item_key_to_cpu(leaf, &key, slot);
843 
844                 if (key.objectid != bytenr)
845                         break;
846                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
847                         continue;
848                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
849                         break;
850 
851                 switch (key.type) {
852                 case BTRFS_SHARED_BLOCK_REF_KEY:
853                         ret = __add_prelim_ref(prefs, 0, NULL,
854                                                 info_level + 1, key.offset,
855                                                 bytenr, 1, GFP_NOFS);
856                         break;
857                 case BTRFS_SHARED_DATA_REF_KEY: {
858                         struct btrfs_shared_data_ref *sdref;
859                         int count;
860 
861                         sdref = btrfs_item_ptr(leaf, slot,
862                                               struct btrfs_shared_data_ref);
863                         count = btrfs_shared_data_ref_count(leaf, sdref);
864                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
865                                                 bytenr, count, GFP_NOFS);
866                         break;
867                 }
868                 case BTRFS_TREE_BLOCK_REF_KEY:
869                         ret = __add_prelim_ref(prefs, key.offset, NULL,
870                                                info_level + 1, 0,
871                                                bytenr, 1, GFP_NOFS);
872                         break;
873                 case BTRFS_EXTENT_DATA_REF_KEY: {
874                         struct btrfs_extent_data_ref *dref;
875                         int count;
876                         u64 root;
877 
878                         dref = btrfs_item_ptr(leaf, slot,
879                                               struct btrfs_extent_data_ref);
880                         count = btrfs_extent_data_ref_count(leaf, dref);
881                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
882                                                                       dref);
883                         key.type = BTRFS_EXTENT_DATA_KEY;
884                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
885 
886                         if (inum && key.objectid != inum) {
887                                 ret = BACKREF_FOUND_SHARED;
888                                 break;
889                         }
890 
891                         root = btrfs_extent_data_ref_root(leaf, dref);
892                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
893                                                bytenr, count, GFP_NOFS);
894                         break;
895                 }
896                 default:
897                         WARN_ON(1);
898                 }
899                 if (ret)
900                         return ret;
901 
902         }
903 
904         return ret;
905 }
906 
907 /*
908  * this adds all existing backrefs (inline backrefs, backrefs and delayed
909  * refs) for the given bytenr to the refs list, merges duplicates and resolves
910  * indirect refs to their parent bytenr.
911  * When roots are found, they're added to the roots list
912  *
913  * NOTE: This can return values > 0
914  *
915  * If time_seq is set to (u64)-1, it will not search delayed_refs, and behave
916  * much like trans == NULL case, the difference only lies in it will not
917  * commit root.
918  * The special case is for qgroup to search roots in commit_transaction().
919  *
920  * FIXME some caching might speed things up
921  */
922 static int find_parent_nodes(struct btrfs_trans_handle *trans,
923                              struct btrfs_fs_info *fs_info, u64 bytenr,
924                              u64 time_seq, struct ulist *refs,
925                              struct ulist *roots, const u64 *extent_item_pos,
926                              u64 root_objectid, u64 inum)
927 {
928         struct btrfs_key key;
929         struct btrfs_path *path;
930         struct btrfs_delayed_ref_root *delayed_refs = NULL;
931         struct btrfs_delayed_ref_head *head;
932         int info_level = 0;
933         int ret;
934         struct list_head prefs_delayed;
935         struct list_head prefs;
936         struct __prelim_ref *ref;
937         struct extent_inode_elem *eie = NULL;
938         u64 total_refs = 0;
939 
940         INIT_LIST_HEAD(&prefs);
941         INIT_LIST_HEAD(&prefs_delayed);
942 
943         key.objectid = bytenr;
944         key.offset = (u64)-1;
945         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
946                 key.type = BTRFS_METADATA_ITEM_KEY;
947         else
948                 key.type = BTRFS_EXTENT_ITEM_KEY;
949 
950         path = btrfs_alloc_path();
951         if (!path)
952                 return -ENOMEM;
953         if (!trans) {
954                 path->search_commit_root = 1;
955                 path->skip_locking = 1;
956         }
957 
958         if (time_seq == (u64)-1)
959                 path->skip_locking = 1;
960 
961         /*
962          * grab both a lock on the path and a lock on the delayed ref head.
963          * We need both to get a consistent picture of how the refs look
964          * at a specified point in time
965          */
966 again:
967         head = NULL;
968 
969         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
970         if (ret < 0)
971                 goto out;
972         BUG_ON(ret == 0);
973 
974 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
975         if (trans && likely(trans->type != __TRANS_DUMMY) &&
976             time_seq != (u64)-1) {
977 #else
978         if (trans && time_seq != (u64)-1) {
979 #endif
980                 /*
981                  * look if there are updates for this ref queued and lock the
982                  * head
983                  */
984                 delayed_refs = &trans->transaction->delayed_refs;
985                 spin_lock(&delayed_refs->lock);
986                 head = btrfs_find_delayed_ref_head(trans, bytenr);
987                 if (head) {
988                         if (!mutex_trylock(&head->mutex)) {
989                                 atomic_inc(&head->node.refs);
990                                 spin_unlock(&delayed_refs->lock);
991 
992                                 btrfs_release_path(path);
993 
994                                 /*
995                                  * Mutex was contended, block until it's
996                                  * released and try again
997                                  */
998                                 mutex_lock(&head->mutex);
999                                 mutex_unlock(&head->mutex);
1000                                 btrfs_put_delayed_ref(&head->node);
1001                                 goto again;
1002                         }
1003                         spin_unlock(&delayed_refs->lock);
1004                         ret = __add_delayed_refs(head, time_seq,
1005                                                  &prefs_delayed, &total_refs,
1006                                                  inum);
1007                         mutex_unlock(&head->mutex);
1008                         if (ret)
1009                                 goto out;
1010                 } else {
1011                         spin_unlock(&delayed_refs->lock);
1012                 }
1013         }
1014 
1015         if (path->slots[0]) {
1016                 struct extent_buffer *leaf;
1017                 int slot;
1018 
1019                 path->slots[0]--;
1020                 leaf = path->nodes[0];
1021                 slot = path->slots[0];
1022                 btrfs_item_key_to_cpu(leaf, &key, slot);
1023                 if (key.objectid == bytenr &&
1024                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
1025                      key.type == BTRFS_METADATA_ITEM_KEY)) {
1026                         ret = __add_inline_refs(fs_info, path, bytenr,
1027                                                 &info_level, &prefs,
1028                                                 &total_refs, inum);
1029                         if (ret)
1030                                 goto out;
1031                         ret = __add_keyed_refs(fs_info, path, bytenr,
1032                                                info_level, &prefs, inum);
1033                         if (ret)
1034                                 goto out;
1035                 }
1036         }
1037         btrfs_release_path(path);
1038 
1039         list_splice_init(&prefs_delayed, &prefs);
1040 
1041         ret = __add_missing_keys(fs_info, &prefs);
1042         if (ret)
1043                 goto out;
1044 
1045         __merge_refs(&prefs, 1);
1046 
1047         ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs,
1048                                       extent_item_pos, total_refs,
1049                                       root_objectid);
1050         if (ret)
1051                 goto out;
1052 
1053         __merge_refs(&prefs, 2);
1054 
1055         while (!list_empty(&prefs)) {
1056                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
1057                 WARN_ON(ref->count < 0);
1058                 if (roots && ref->count && ref->root_id && ref->parent == 0) {
1059                         if (root_objectid && ref->root_id != root_objectid) {
1060                                 ret = BACKREF_FOUND_SHARED;
1061                                 goto out;
1062                         }
1063 
1064                         /* no parent == root of tree */
1065                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
1066                         if (ret < 0)
1067                                 goto out;
1068                 }
1069                 if (ref->count && ref->parent) {
1070                         if (extent_item_pos && !ref->inode_list &&
1071                             ref->level == 0) {
1072                                 struct extent_buffer *eb;
1073 
1074                                 eb = read_tree_block(fs_info->extent_root,
1075                                                            ref->parent, 0);
1076                                 if (IS_ERR(eb)) {
1077                                         ret = PTR_ERR(eb);
1078                                         goto out;
1079                                 } else if (!extent_buffer_uptodate(eb)) {
1080                                         free_extent_buffer(eb);
1081                                         ret = -EIO;
1082                                         goto out;
1083                                 }
1084                                 btrfs_tree_read_lock(eb);
1085                                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1086                                 ret = find_extent_in_eb(eb, bytenr,
1087                                                         *extent_item_pos, &eie);
1088                                 btrfs_tree_read_unlock_blocking(eb);
1089                                 free_extent_buffer(eb);
1090                                 if (ret < 0)
1091                                         goto out;
1092                                 ref->inode_list = eie;
1093                         }
1094                         ret = ulist_add_merge_ptr(refs, ref->parent,
1095                                                   ref->inode_list,
1096                                                   (void **)&eie, GFP_NOFS);
1097                         if (ret < 0)
1098                                 goto out;
1099                         if (!ret && extent_item_pos) {
1100                                 /*
1101                                  * we've recorded that parent, so we must extend
1102                                  * its inode list here
1103                                  */
1104                                 BUG_ON(!eie);
1105                                 while (eie->next)
1106                                         eie = eie->next;
1107                                 eie->next = ref->inode_list;
1108                         }
1109                         eie = NULL;
1110                 }
1111                 list_del(&ref->list);
1112                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1113         }
1114 
1115 out:
1116         btrfs_free_path(path);
1117         while (!list_empty(&prefs)) {
1118                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
1119                 list_del(&ref->list);
1120                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1121         }
1122         while (!list_empty(&prefs_delayed)) {
1123                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
1124                                        list);
1125                 list_del(&ref->list);
1126                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1127         }
1128         if (ret < 0)
1129                 free_inode_elem_list(eie);
1130         return ret;
1131 }
1132 
1133 static void free_leaf_list(struct ulist *blocks)
1134 {
1135         struct ulist_node *node = NULL;
1136         struct extent_inode_elem *eie;
1137         struct ulist_iterator uiter;
1138 
1139         ULIST_ITER_INIT(&uiter);
1140         while ((node = ulist_next(blocks, &uiter))) {
1141                 if (!node->aux)
1142                         continue;
1143                 eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
1144                 free_inode_elem_list(eie);
1145                 node->aux = 0;
1146         }
1147 
1148         ulist_free(blocks);
1149 }
1150 
1151 /*
1152  * Finds all leafs with a reference to the specified combination of bytenr and
1153  * offset. key_list_head will point to a list of corresponding keys (caller must
1154  * free each list element). The leafs will be stored in the leafs ulist, which
1155  * must be freed with ulist_free.
1156  *
1157  * returns 0 on success, <0 on error
1158  */
1159 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1160                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1161                                 u64 time_seq, struct ulist **leafs,
1162                                 const u64 *extent_item_pos)
1163 {
1164         int ret;
1165 
1166         *leafs = ulist_alloc(GFP_NOFS);
1167         if (!*leafs)
1168                 return -ENOMEM;
1169 
1170         ret = find_parent_nodes(trans, fs_info, bytenr,
1171                                 time_seq, *leafs, NULL, extent_item_pos, 0, 0);
1172         if (ret < 0 && ret != -ENOENT) {
1173                 free_leaf_list(*leafs);
1174                 return ret;
1175         }
1176 
1177         return 0;
1178 }
1179 
1180 /*
1181  * walk all backrefs for a given extent to find all roots that reference this
1182  * extent. Walking a backref means finding all extents that reference this
1183  * extent and in turn walk the backrefs of those, too. Naturally this is a
1184  * recursive process, but here it is implemented in an iterative fashion: We
1185  * find all referencing extents for the extent in question and put them on a
1186  * list. In turn, we find all referencing extents for those, further appending
1187  * to the list. The way we iterate the list allows adding more elements after
1188  * the current while iterating. The process stops when we reach the end of the
1189  * list. Found roots are added to the roots list.
1190  *
1191  * returns 0 on success, < 0 on error.
1192  */
1193 static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1194                                   struct btrfs_fs_info *fs_info, u64 bytenr,
1195                                   u64 time_seq, struct ulist **roots)
1196 {
1197         struct ulist *tmp;
1198         struct ulist_node *node = NULL;
1199         struct ulist_iterator uiter;
1200         int ret;
1201 
1202         tmp = ulist_alloc(GFP_NOFS);
1203         if (!tmp)
1204                 return -ENOMEM;
1205         *roots = ulist_alloc(GFP_NOFS);
1206         if (!*roots) {
1207                 ulist_free(tmp);
1208                 return -ENOMEM;
1209         }
1210 
1211         ULIST_ITER_INIT(&uiter);
1212         while (1) {
1213                 ret = find_parent_nodes(trans, fs_info, bytenr,
1214                                         time_seq, tmp, *roots, NULL, 0, 0);
1215                 if (ret < 0 && ret != -ENOENT) {
1216                         ulist_free(tmp);
1217                         ulist_free(*roots);
1218                         return ret;
1219                 }
1220                 node = ulist_next(tmp, &uiter);
1221                 if (!node)
1222                         break;
1223                 bytenr = node->val;
1224                 cond_resched();
1225         }
1226 
1227         ulist_free(tmp);
1228         return 0;
1229 }
1230 
1231 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1232                          struct btrfs_fs_info *fs_info, u64 bytenr,
1233                          u64 time_seq, struct ulist **roots)
1234 {
1235         int ret;
1236 
1237         if (!trans)
1238                 down_read(&fs_info->commit_root_sem);
1239         ret = __btrfs_find_all_roots(trans, fs_info, bytenr, time_seq, roots);
1240         if (!trans)
1241                 up_read(&fs_info->commit_root_sem);
1242         return ret;
1243 }
1244 
1245 /**
1246  * btrfs_check_shared - tell us whether an extent is shared
1247  *
1248  * @trans: optional trans handle
1249  *
1250  * btrfs_check_shared uses the backref walking code but will short
1251  * circuit as soon as it finds a root or inode that doesn't match the
1252  * one passed in. This provides a significant performance benefit for
1253  * callers (such as fiemap) which want to know whether the extent is
1254  * shared but do not need a ref count.
1255  *
1256  * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1257  */
1258 int btrfs_check_shared(struct btrfs_trans_handle *trans,
1259                        struct btrfs_fs_info *fs_info, u64 root_objectid,
1260                        u64 inum, u64 bytenr)
1261 {
1262         struct ulist *tmp = NULL;
1263         struct ulist *roots = NULL;
1264         struct ulist_iterator uiter;
1265         struct ulist_node *node;
1266         struct seq_list elem = SEQ_LIST_INIT(elem);
1267         int ret = 0;
1268 
1269         tmp = ulist_alloc(GFP_NOFS);
1270         roots = ulist_alloc(GFP_NOFS);
1271         if (!tmp || !roots) {
1272                 ulist_free(tmp);
1273                 ulist_free(roots);
1274                 return -ENOMEM;
1275         }
1276 
1277         if (trans)
1278                 btrfs_get_tree_mod_seq(fs_info, &elem);
1279         else
1280                 down_read(&fs_info->commit_root_sem);
1281         ULIST_ITER_INIT(&uiter);
1282         while (1) {
1283                 ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
1284                                         roots, NULL, root_objectid, inum);
1285                 if (ret == BACKREF_FOUND_SHARED) {
1286                         /* this is the only condition under which we return 1 */
1287                         ret = 1;
1288                         break;
1289                 }
1290                 if (ret < 0 && ret != -ENOENT)
1291                         break;
1292                 ret = 0;
1293                 node = ulist_next(tmp, &uiter);
1294                 if (!node)
1295                         break;
1296                 bytenr = node->val;
1297                 cond_resched();
1298         }
1299         if (trans)
1300                 btrfs_put_tree_mod_seq(fs_info, &elem);
1301         else
1302                 up_read(&fs_info->commit_root_sem);
1303         ulist_free(tmp);
1304         ulist_free(roots);
1305         return ret;
1306 }
1307 
1308 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1309                           u64 start_off, struct btrfs_path *path,
1310                           struct btrfs_inode_extref **ret_extref,
1311                           u64 *found_off)
1312 {
1313         int ret, slot;
1314         struct btrfs_key key;
1315         struct btrfs_key found_key;
1316         struct btrfs_inode_extref *extref;
1317         struct extent_buffer *leaf;
1318         unsigned long ptr;
1319 
1320         key.objectid = inode_objectid;
1321         key.type = BTRFS_INODE_EXTREF_KEY;
1322         key.offset = start_off;
1323 
1324         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1325         if (ret < 0)
1326                 return ret;
1327 
1328         while (1) {
1329                 leaf = path->nodes[0];
1330                 slot = path->slots[0];
1331                 if (slot >= btrfs_header_nritems(leaf)) {
1332                         /*
1333                          * If the item at offset is not found,
1334                          * btrfs_search_slot will point us to the slot
1335                          * where it should be inserted. In our case
1336                          * that will be the slot directly before the
1337                          * next INODE_REF_KEY_V2 item. In the case
1338                          * that we're pointing to the last slot in a
1339                          * leaf, we must move one leaf over.
1340                          */
1341                         ret = btrfs_next_leaf(root, path);
1342                         if (ret) {
1343                                 if (ret >= 1)
1344                                         ret = -ENOENT;
1345                                 break;
1346                         }
1347                         continue;
1348                 }
1349 
1350                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1351 
1352                 /*
1353                  * Check that we're still looking at an extended ref key for
1354                  * this particular objectid. If we have different
1355                  * objectid or type then there are no more to be found
1356                  * in the tree and we can exit.
1357                  */
1358                 ret = -ENOENT;
1359                 if (found_key.objectid != inode_objectid)
1360                         break;
1361                 if (found_key.type != BTRFS_INODE_EXTREF_KEY)
1362                         break;
1363 
1364                 ret = 0;
1365                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1366                 extref = (struct btrfs_inode_extref *)ptr;
1367                 *ret_extref = extref;
1368                 if (found_off)
1369                         *found_off = found_key.offset;
1370                 break;
1371         }
1372 
1373         return ret;
1374 }
1375 
1376 /*
1377  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1378  * Elements of the path are separated by '/' and the path is guaranteed to be
1379  * 0-terminated. the path is only given within the current file system.
1380  * Therefore, it never starts with a '/'. the caller is responsible to provide
1381  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1382  * the start point of the resulting string is returned. this pointer is within
1383  * dest, normally.
1384  * in case the path buffer would overflow, the pointer is decremented further
1385  * as if output was written to the buffer, though no more output is actually
1386  * generated. that way, the caller can determine how much space would be
1387  * required for the path to fit into the buffer. in that case, the returned
1388  * value will be smaller than dest. callers must check this!
1389  */
1390 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1391                         u32 name_len, unsigned long name_off,
1392                         struct extent_buffer *eb_in, u64 parent,
1393                         char *dest, u32 size)
1394 {
1395         int slot;
1396         u64 next_inum;
1397         int ret;
1398         s64 bytes_left = ((s64)size) - 1;
1399         struct extent_buffer *eb = eb_in;
1400         struct btrfs_key found_key;
1401         int leave_spinning = path->leave_spinning;
1402         struct btrfs_inode_ref *iref;
1403 
1404         if (bytes_left >= 0)
1405                 dest[bytes_left] = '\0';
1406 
1407         path->leave_spinning = 1;
1408         while (1) {
1409                 bytes_left -= name_len;
1410                 if (bytes_left >= 0)
1411                         read_extent_buffer(eb, dest + bytes_left,
1412                                            name_off, name_len);
1413                 if (eb != eb_in) {
1414                         btrfs_tree_read_unlock_blocking(eb);
1415                         free_extent_buffer(eb);
1416                 }
1417                 ret = btrfs_find_item(fs_root, path, parent, 0,
1418                                 BTRFS_INODE_REF_KEY, &found_key);
1419                 if (ret > 0)
1420                         ret = -ENOENT;
1421                 if (ret)
1422                         break;
1423 
1424                 next_inum = found_key.offset;
1425 
1426                 /* regular exit ahead */
1427                 if (parent == next_inum)
1428                         break;
1429 
1430                 slot = path->slots[0];
1431                 eb = path->nodes[0];
1432                 /* make sure we can use eb after releasing the path */
1433                 if (eb != eb_in) {
1434                         atomic_inc(&eb->refs);
1435                         btrfs_tree_read_lock(eb);
1436                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1437                 }
1438                 btrfs_release_path(path);
1439                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1440 
1441                 name_len = btrfs_inode_ref_name_len(eb, iref);
1442                 name_off = (unsigned long)(iref + 1);
1443 
1444                 parent = next_inum;
1445                 --bytes_left;
1446                 if (bytes_left >= 0)
1447                         dest[bytes_left] = '/';
1448         }
1449 
1450         btrfs_release_path(path);
1451         path->leave_spinning = leave_spinning;
1452 
1453         if (ret)
1454                 return ERR_PTR(ret);
1455 
1456         return dest + bytes_left;
1457 }
1458 
1459 /*
1460  * this makes the path point to (logical EXTENT_ITEM *)
1461  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1462  * tree blocks and <0 on error.
1463  */
1464 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1465                         struct btrfs_path *path, struct btrfs_key *found_key,
1466                         u64 *flags_ret)
1467 {
1468         int ret;
1469         u64 flags;
1470         u64 size = 0;
1471         u32 item_size;
1472         struct extent_buffer *eb;
1473         struct btrfs_extent_item *ei;
1474         struct btrfs_key key;
1475 
1476         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1477                 key.type = BTRFS_METADATA_ITEM_KEY;
1478         else
1479                 key.type = BTRFS_EXTENT_ITEM_KEY;
1480         key.objectid = logical;
1481         key.offset = (u64)-1;
1482 
1483         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1484         if (ret < 0)
1485                 return ret;
1486 
1487         ret = btrfs_previous_extent_item(fs_info->extent_root, path, 0);
1488         if (ret) {
1489                 if (ret > 0)
1490                         ret = -ENOENT;
1491                 return ret;
1492         }
1493         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1494         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1495                 size = fs_info->extent_root->nodesize;
1496         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1497                 size = found_key->offset;
1498 
1499         if (found_key->objectid > logical ||
1500             found_key->objectid + size <= logical) {
1501                 pr_debug("logical %llu is not within any extent\n", logical);
1502                 return -ENOENT;
1503         }
1504 
1505         eb = path->nodes[0];
1506         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1507         BUG_ON(item_size < sizeof(*ei));
1508 
1509         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1510         flags = btrfs_extent_flags(eb, ei);
1511 
1512         pr_debug("logical %llu is at position %llu within the extent (%llu "
1513                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1514                  logical, logical - found_key->objectid, found_key->objectid,
1515                  found_key->offset, flags, item_size);
1516 
1517         WARN_ON(!flags_ret);
1518         if (flags_ret) {
1519                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1520                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1521                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1522                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1523                 else
1524                         BUG_ON(1);
1525                 return 0;
1526         }
1527 
1528         return -EIO;
1529 }
1530 
1531 /*
1532  * helper function to iterate extent inline refs. ptr must point to a 0 value
1533  * for the first call and may be modified. it is used to track state.
1534  * if more refs exist, 0 is returned and the next call to
1535  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1536  * next ref. after the last ref was processed, 1 is returned.
1537  * returns <0 on error
1538  */
1539 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1540                                    struct btrfs_key *key,
1541                                    struct btrfs_extent_item *ei, u32 item_size,
1542                                    struct btrfs_extent_inline_ref **out_eiref,
1543                                    int *out_type)
1544 {
1545         unsigned long end;
1546         u64 flags;
1547         struct btrfs_tree_block_info *info;
1548 
1549         if (!*ptr) {
1550                 /* first call */
1551                 flags = btrfs_extent_flags(eb, ei);
1552                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1553                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1554                                 /* a skinny metadata extent */
1555                                 *out_eiref =
1556                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1557                         } else {
1558                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1559                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1560                                 *out_eiref =
1561                                    (struct btrfs_extent_inline_ref *)(info + 1);
1562                         }
1563                 } else {
1564                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1565                 }
1566                 *ptr = (unsigned long)*out_eiref;
1567                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1568                         return -ENOENT;
1569         }
1570 
1571         end = (unsigned long)ei + item_size;
1572         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1573         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1574 
1575         *ptr += btrfs_extent_inline_ref_size(*out_type);
1576         WARN_ON(*ptr > end);
1577         if (*ptr == end)
1578                 return 1; /* last */
1579 
1580         return 0;
1581 }
1582 
1583 /*
1584  * reads the tree block backref for an extent. tree level and root are returned
1585  * through out_level and out_root. ptr must point to a 0 value for the first
1586  * call and may be modified (see __get_extent_inline_ref comment).
1587  * returns 0 if data was provided, 1 if there was no more data to provide or
1588  * <0 on error.
1589  */
1590 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1591                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1592                             u32 item_size, u64 *out_root, u8 *out_level)
1593 {
1594         int ret;
1595         int type;
1596         struct btrfs_extent_inline_ref *eiref;
1597 
1598         if (*ptr == (unsigned long)-1)
1599                 return 1;
1600 
1601         while (1) {
1602                 ret = __get_extent_inline_ref(ptr, eb, key, ei, item_size,
1603                                               &eiref, &type);
1604                 if (ret < 0)
1605                         return ret;
1606 
1607                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1608                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1609                         break;
1610 
1611                 if (ret == 1)
1612                         return 1;
1613         }
1614 
1615         /* we can treat both ref types equally here */
1616         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1617 
1618         if (key->type == BTRFS_EXTENT_ITEM_KEY) {
1619                 struct btrfs_tree_block_info *info;
1620 
1621                 info = (struct btrfs_tree_block_info *)(ei + 1);
1622                 *out_level = btrfs_tree_block_level(eb, info);
1623         } else {
1624                 ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
1625                 *out_level = (u8)key->offset;
1626         }
1627 
1628         if (ret == 1)
1629                 *ptr = (unsigned long)-1;
1630 
1631         return 0;
1632 }
1633 
1634 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1635                                 u64 root, u64 extent_item_objectid,
1636                                 iterate_extent_inodes_t *iterate, void *ctx)
1637 {
1638         struct extent_inode_elem *eie;
1639         int ret = 0;
1640 
1641         for (eie = inode_list; eie; eie = eie->next) {
1642                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1643                          "root %llu\n", extent_item_objectid,
1644                          eie->inum, eie->offset, root);
1645                 ret = iterate(eie->inum, eie->offset, root, ctx);
1646                 if (ret) {
1647                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1648                                  extent_item_objectid, ret);
1649                         break;
1650                 }
1651         }
1652 
1653         return ret;
1654 }
1655 
1656 /*
1657  * calls iterate() for every inode that references the extent identified by
1658  * the given parameters.
1659  * when the iterator function returns a non-zero value, iteration stops.
1660  */
1661 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1662                                 u64 extent_item_objectid, u64 extent_item_pos,
1663                                 int search_commit_root,
1664                                 iterate_extent_inodes_t *iterate, void *ctx)
1665 {
1666         int ret;
1667         struct btrfs_trans_handle *trans = NULL;
1668         struct ulist *refs = NULL;
1669         struct ulist *roots = NULL;
1670         struct ulist_node *ref_node = NULL;
1671         struct ulist_node *root_node = NULL;
1672         struct seq_list tree_mod_seq_elem = SEQ_LIST_INIT(tree_mod_seq_elem);
1673         struct ulist_iterator ref_uiter;
1674         struct ulist_iterator root_uiter;
1675 
1676         pr_debug("resolving all inodes for extent %llu\n",
1677                         extent_item_objectid);
1678 
1679         if (!search_commit_root) {
1680                 trans = btrfs_join_transaction(fs_info->extent_root);
1681                 if (IS_ERR(trans))
1682                         return PTR_ERR(trans);
1683                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1684         } else {
1685                 down_read(&fs_info->commit_root_sem);
1686         }
1687 
1688         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1689                                    tree_mod_seq_elem.seq, &refs,
1690                                    &extent_item_pos);
1691         if (ret)
1692                 goto out;
1693 
1694         ULIST_ITER_INIT(&ref_uiter);
1695         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1696                 ret = __btrfs_find_all_roots(trans, fs_info, ref_node->val,
1697                                              tree_mod_seq_elem.seq, &roots);
1698                 if (ret)
1699                         break;
1700                 ULIST_ITER_INIT(&root_uiter);
1701                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1702                         pr_debug("root %llu references leaf %llu, data list "
1703                                  "%#llx\n", root_node->val, ref_node->val,
1704                                  ref_node->aux);
1705                         ret = iterate_leaf_refs((struct extent_inode_elem *)
1706                                                 (uintptr_t)ref_node->aux,
1707                                                 root_node->val,
1708                                                 extent_item_objectid,
1709                                                 iterate, ctx);
1710                 }
1711                 ulist_free(roots);
1712         }
1713 
1714         free_leaf_list(refs);
1715 out:
1716         if (!search_commit_root) {
1717                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1718                 btrfs_end_transaction(trans, fs_info->extent_root);
1719         } else {
1720                 up_read(&fs_info->commit_root_sem);
1721         }
1722 
1723         return ret;
1724 }
1725 
1726 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1727                                 struct btrfs_path *path,
1728                                 iterate_extent_inodes_t *iterate, void *ctx)
1729 {
1730         int ret;
1731         u64 extent_item_pos;
1732         u64 flags = 0;
1733         struct btrfs_key found_key;
1734         int search_commit_root = path->search_commit_root;
1735 
1736         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1737         btrfs_release_path(path);
1738         if (ret < 0)
1739                 return ret;
1740         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1741                 return -EINVAL;
1742 
1743         extent_item_pos = logical - found_key.objectid;
1744         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1745                                         extent_item_pos, search_commit_root,
1746                                         iterate, ctx);
1747 
1748         return ret;
1749 }
1750 
1751 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1752                               struct extent_buffer *eb, void *ctx);
1753 
1754 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1755                               struct btrfs_path *path,
1756                               iterate_irefs_t *iterate, void *ctx)
1757 {
1758         int ret = 0;
1759         int slot;
1760         u32 cur;
1761         u32 len;
1762         u32 name_len;
1763         u64 parent = 0;
1764         int found = 0;
1765         struct extent_buffer *eb;
1766         struct btrfs_item *item;
1767         struct btrfs_inode_ref *iref;
1768         struct btrfs_key found_key;
1769 
1770         while (!ret) {
1771                 ret = btrfs_find_item(fs_root, path, inum,
1772                                 parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
1773                                 &found_key);
1774 
1775                 if (ret < 0)
1776                         break;
1777                 if (ret) {
1778                         ret = found ? 0 : -ENOENT;
1779                         break;
1780                 }
1781                 ++found;
1782 
1783                 parent = found_key.offset;
1784                 slot = path->slots[0];
1785                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1786                 if (!eb) {
1787                         ret = -ENOMEM;
1788                         break;
1789                 }
1790                 extent_buffer_get(eb);
1791                 btrfs_tree_read_lock(eb);
1792                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1793                 btrfs_release_path(path);
1794 
1795                 item = btrfs_item_nr(slot);
1796                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1797 
1798                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1799                         name_len = btrfs_inode_ref_name_len(eb, iref);
1800                         /* path must be released before calling iterate()! */
1801                         pr_debug("following ref at offset %u for inode %llu in "
1802                                  "tree %llu\n", cur, found_key.objectid,
1803                                  fs_root->objectid);
1804                         ret = iterate(parent, name_len,
1805                                       (unsigned long)(iref + 1), eb, ctx);
1806                         if (ret)
1807                                 break;
1808                         len = sizeof(*iref) + name_len;
1809                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1810                 }
1811                 btrfs_tree_read_unlock_blocking(eb);
1812                 free_extent_buffer(eb);
1813         }
1814 
1815         btrfs_release_path(path);
1816 
1817         return ret;
1818 }
1819 
1820 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1821                                  struct btrfs_path *path,
1822                                  iterate_irefs_t *iterate, void *ctx)
1823 {
1824         int ret;
1825         int slot;
1826         u64 offset = 0;
1827         u64 parent;
1828         int found = 0;
1829         struct extent_buffer *eb;
1830         struct btrfs_inode_extref *extref;
1831         u32 item_size;
1832         u32 cur_offset;
1833         unsigned long ptr;
1834 
1835         while (1) {
1836                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1837                                             &offset);
1838                 if (ret < 0)
1839                         break;
1840                 if (ret) {
1841                         ret = found ? 0 : -ENOENT;
1842                         break;
1843                 }
1844                 ++found;
1845 
1846                 slot = path->slots[0];
1847                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1848                 if (!eb) {
1849                         ret = -ENOMEM;
1850                         break;
1851                 }
1852                 extent_buffer_get(eb);
1853 
1854                 btrfs_tree_read_lock(eb);
1855                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1856                 btrfs_release_path(path);
1857 
1858                 item_size = btrfs_item_size_nr(eb, slot);
1859                 ptr = btrfs_item_ptr_offset(eb, slot);
1860                 cur_offset = 0;
1861 
1862                 while (cur_offset < item_size) {
1863                         u32 name_len;
1864 
1865                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1866                         parent = btrfs_inode_extref_parent(eb, extref);
1867                         name_len = btrfs_inode_extref_name_len(eb, extref);
1868                         ret = iterate(parent, name_len,
1869                                       (unsigned long)&extref->name, eb, ctx);
1870                         if (ret)
1871                                 break;
1872 
1873                         cur_offset += btrfs_inode_extref_name_len(eb, extref);
1874                         cur_offset += sizeof(*extref);
1875                 }
1876                 btrfs_tree_read_unlock_blocking(eb);
1877                 free_extent_buffer(eb);
1878 
1879                 offset++;
1880         }
1881 
1882         btrfs_release_path(path);
1883 
1884         return ret;
1885 }
1886 
1887 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1888                          struct btrfs_path *path, iterate_irefs_t *iterate,
1889                          void *ctx)
1890 {
1891         int ret;
1892         int found_refs = 0;
1893 
1894         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1895         if (!ret)
1896                 ++found_refs;
1897         else if (ret != -ENOENT)
1898                 return ret;
1899 
1900         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1901         if (ret == -ENOENT && found_refs)
1902                 return 0;
1903 
1904         return ret;
1905 }
1906 
1907 /*
1908  * returns 0 if the path could be dumped (probably truncated)
1909  * returns <0 in case of an error
1910  */
1911 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1912                          struct extent_buffer *eb, void *ctx)
1913 {
1914         struct inode_fs_paths *ipath = ctx;
1915         char *fspath;
1916         char *fspath_min;
1917         int i = ipath->fspath->elem_cnt;
1918         const int s_ptr = sizeof(char *);
1919         u32 bytes_left;
1920 
1921         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1922                                         ipath->fspath->bytes_left - s_ptr : 0;
1923 
1924         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1925         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1926                                    name_off, eb, inum, fspath_min, bytes_left);
1927         if (IS_ERR(fspath))
1928                 return PTR_ERR(fspath);
1929 
1930         if (fspath > fspath_min) {
1931                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1932                 ++ipath->fspath->elem_cnt;
1933                 ipath->fspath->bytes_left = fspath - fspath_min;
1934         } else {
1935                 ++ipath->fspath->elem_missed;
1936                 ipath->fspath->bytes_missing += fspath_min - fspath;
1937                 ipath->fspath->bytes_left = 0;
1938         }
1939 
1940         return 0;
1941 }
1942 
1943 /*
1944  * this dumps all file system paths to the inode into the ipath struct, provided
1945  * is has been created large enough. each path is zero-terminated and accessed
1946  * from ipath->fspath->val[i].
1947  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1948  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1949  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1950  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1951  * have been needed to return all paths.
1952  */
1953 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1954 {
1955         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1956                              inode_to_path, ipath);
1957 }
1958 
1959 struct btrfs_data_container *init_data_container(u32 total_bytes)
1960 {
1961         struct btrfs_data_container *data;
1962         size_t alloc_bytes;
1963 
1964         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1965         data = vmalloc(alloc_bytes);
1966         if (!data)
1967                 return ERR_PTR(-ENOMEM);
1968 
1969         if (total_bytes >= sizeof(*data)) {
1970                 data->bytes_left = total_bytes - sizeof(*data);
1971                 data->bytes_missing = 0;
1972         } else {
1973                 data->bytes_missing = sizeof(*data) - total_bytes;
1974                 data->bytes_left = 0;
1975         }
1976 
1977         data->elem_cnt = 0;
1978         data->elem_missed = 0;
1979 
1980         return data;
1981 }
1982 
1983 /*
1984  * allocates space to return multiple file system paths for an inode.
1985  * total_bytes to allocate are passed, note that space usable for actual path
1986  * information will be total_bytes - sizeof(struct inode_fs_paths).
1987  * the returned pointer must be freed with free_ipath() in the end.
1988  */
1989 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1990                                         struct btrfs_path *path)
1991 {
1992         struct inode_fs_paths *ifp;
1993         struct btrfs_data_container *fspath;
1994 
1995         fspath = init_data_container(total_bytes);
1996         if (IS_ERR(fspath))
1997                 return (void *)fspath;
1998 
1999         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
2000         if (!ifp) {
2001                 kfree(fspath);
2002                 return ERR_PTR(-ENOMEM);
2003         }
2004 
2005         ifp->btrfs_path = path;
2006         ifp->fspath = fspath;
2007         ifp->fs_root = fs_root;
2008 
2009         return ifp;
2010 }
2011 
2012 void free_ipath(struct inode_fs_paths *ipath)
2013 {
2014         if (!ipath)
2015                 return;
2016         vfree(ipath->fspath);
2017         kfree(ipath);
2018 }
2019 

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