1 // SPDX-License-Identifier: GPL-2.0
4 #include <linux/slab.h>
5 #include <linux/spinlock.h>
8 #include "extent_map.h"
9 #include "compression.h"
10 #include "btrfs_inode.h"
13 static struct kmem_cache *extent_map_cache;
15 int __init extent_map_init(void)
17 extent_map_cache = kmem_cache_create("btrfs_extent_map",
18 sizeof(struct extent_map), 0,
19 SLAB_MEM_SPREAD, NULL);
20 if (!extent_map_cache)
25 void __cold extent_map_exit(void)
27 kmem_cache_destroy(extent_map_cache);
31 * extent_map_tree_init - initialize extent map tree
32 * @tree: tree to initialize
34 * Initialize the extent tree @tree. Should be called for each new inode
35 * or other user of the extent_map interface.
37 void extent_map_tree_init(struct extent_map_tree *tree)
39 tree->map = RB_ROOT_CACHED;
40 INIT_LIST_HEAD(&tree->modified_extents);
41 rwlock_init(&tree->lock);
45 * alloc_extent_map - allocate new extent map structure
47 * Allocate a new extent_map structure. The new structure is
48 * returned with a reference count of one and needs to be
49 * freed using free_extent_map()
51 struct extent_map *alloc_extent_map(void)
53 struct extent_map *em;
54 em = kmem_cache_zalloc(extent_map_cache, GFP_NOFS);
57 RB_CLEAR_NODE(&em->rb_node);
58 em->compress_type = BTRFS_COMPRESS_NONE;
59 refcount_set(&em->refs, 1);
60 INIT_LIST_HEAD(&em->list);
65 * free_extent_map - drop reference count of an extent_map
66 * @em: extent map being released
68 * Drops the reference out on @em by one and free the structure
69 * if the reference count hits zero.
71 void free_extent_map(struct extent_map *em)
75 if (refcount_dec_and_test(&em->refs)) {
76 WARN_ON(extent_map_in_tree(em));
77 WARN_ON(!list_empty(&em->list));
78 if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
79 kfree(em->map_lookup);
80 kmem_cache_free(extent_map_cache, em);
84 /* simple helper to do math around the end of an extent, handling wrap */
85 static u64 range_end(u64 start, u64 len)
87 if (start + len < start)
92 static int tree_insert(struct rb_root_cached *root, struct extent_map *em)
94 struct rb_node **p = &root->rb_root.rb_node;
95 struct rb_node *parent = NULL;
96 struct extent_map *entry = NULL;
97 struct rb_node *orig_parent = NULL;
98 u64 end = range_end(em->start, em->len);
103 entry = rb_entry(parent, struct extent_map, rb_node);
105 if (em->start < entry->start) {
107 } else if (em->start >= extent_map_end(entry)) {
115 orig_parent = parent;
116 while (parent && em->start >= extent_map_end(entry)) {
117 parent = rb_next(parent);
118 entry = rb_entry(parent, struct extent_map, rb_node);
121 if (end > entry->start && em->start < extent_map_end(entry))
124 parent = orig_parent;
125 entry = rb_entry(parent, struct extent_map, rb_node);
126 while (parent && em->start < entry->start) {
127 parent = rb_prev(parent);
128 entry = rb_entry(parent, struct extent_map, rb_node);
131 if (end > entry->start && em->start < extent_map_end(entry))
134 rb_link_node(&em->rb_node, orig_parent, p);
135 rb_insert_color_cached(&em->rb_node, root, leftmost);
140 * search through the tree for an extent_map with a given offset. If
141 * it can't be found, try to find some neighboring extents
143 static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
144 struct rb_node **prev_or_next_ret)
146 struct rb_node *n = root->rb_node;
147 struct rb_node *prev = NULL;
148 struct rb_node *orig_prev = NULL;
149 struct extent_map *entry;
150 struct extent_map *prev_entry = NULL;
152 ASSERT(prev_or_next_ret);
155 entry = rb_entry(n, struct extent_map, rb_node);
159 if (offset < entry->start)
161 else if (offset >= extent_map_end(entry))
168 while (prev && offset >= extent_map_end(prev_entry)) {
169 prev = rb_next(prev);
170 prev_entry = rb_entry(prev, struct extent_map, rb_node);
174 * Previous extent map found, return as in this case the caller does not
175 * care about the next one.
178 *prev_or_next_ret = prev;
183 prev_entry = rb_entry(prev, struct extent_map, rb_node);
184 while (prev && offset < prev_entry->start) {
185 prev = rb_prev(prev);
186 prev_entry = rb_entry(prev, struct extent_map, rb_node);
188 *prev_or_next_ret = prev;
193 /* check to see if two extent_map structs are adjacent and safe to merge */
194 static int mergable_maps(struct extent_map *prev, struct extent_map *next)
196 if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
200 * don't merge compressed extents, we need to know their
203 if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
206 if (test_bit(EXTENT_FLAG_LOGGING, &prev->flags) ||
207 test_bit(EXTENT_FLAG_LOGGING, &next->flags))
211 * We don't want to merge stuff that hasn't been written to the log yet
212 * since it may not reflect exactly what is on disk, and that would be
215 if (!list_empty(&prev->list) || !list_empty(&next->list))
218 ASSERT(next->block_start != EXTENT_MAP_DELALLOC &&
219 prev->block_start != EXTENT_MAP_DELALLOC);
221 if (prev->map_lookup || next->map_lookup)
222 ASSERT(test_bit(EXTENT_FLAG_FS_MAPPING, &prev->flags) &&
223 test_bit(EXTENT_FLAG_FS_MAPPING, &next->flags));
225 if (extent_map_end(prev) == next->start &&
226 prev->flags == next->flags &&
227 prev->map_lookup == next->map_lookup &&
228 ((next->block_start == EXTENT_MAP_HOLE &&
229 prev->block_start == EXTENT_MAP_HOLE) ||
230 (next->block_start == EXTENT_MAP_INLINE &&
231 prev->block_start == EXTENT_MAP_INLINE) ||
232 (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
233 next->block_start == extent_map_block_end(prev)))) {
239 static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)
241 struct extent_map *merge = NULL;
245 * We can't modify an extent map that is in the tree and that is being
246 * used by another task, as it can cause that other task to see it in
247 * inconsistent state during the merging. We always have 1 reference for
248 * the tree and 1 for this task (which is unpinning the extent map or
249 * clearing the logging flag), so anything > 2 means it's being used by
252 if (refcount_read(&em->refs) > 2)
255 if (em->start != 0) {
256 rb = rb_prev(&em->rb_node);
258 merge = rb_entry(rb, struct extent_map, rb_node);
259 if (rb && mergable_maps(merge, em)) {
260 em->start = merge->start;
261 em->orig_start = merge->orig_start;
262 em->len += merge->len;
263 em->block_len += merge->block_len;
264 em->block_start = merge->block_start;
265 em->mod_len = (em->mod_len + em->mod_start) - merge->mod_start;
266 em->mod_start = merge->mod_start;
267 em->generation = max(em->generation, merge->generation);
268 set_bit(EXTENT_FLAG_MERGED, &em->flags);
270 rb_erase_cached(&merge->rb_node, &tree->map);
271 RB_CLEAR_NODE(&merge->rb_node);
272 free_extent_map(merge);
276 rb = rb_next(&em->rb_node);
278 merge = rb_entry(rb, struct extent_map, rb_node);
279 if (rb && mergable_maps(em, merge)) {
280 em->len += merge->len;
281 em->block_len += merge->block_len;
282 rb_erase_cached(&merge->rb_node, &tree->map);
283 RB_CLEAR_NODE(&merge->rb_node);
284 em->mod_len = (merge->mod_start + merge->mod_len) - em->mod_start;
285 em->generation = max(em->generation, merge->generation);
286 set_bit(EXTENT_FLAG_MERGED, &em->flags);
287 free_extent_map(merge);
292 * unpin_extent_cache - unpin an extent from the cache
293 * @tree: tree to unpin the extent in
294 * @start: logical offset in the file
295 * @len: length of the extent
296 * @gen: generation that this extent has been modified in
298 * Called after an extent has been written to disk properly. Set the generation
299 * to the generation that actually added the file item to the inode so we know
300 * we need to sync this extent when we call fsync().
302 int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len,
306 struct extent_map *em;
307 bool prealloc = false;
309 write_lock(&tree->lock);
310 em = lookup_extent_mapping(tree, start, len);
312 WARN_ON(!em || em->start != start);
317 em->generation = gen;
318 clear_bit(EXTENT_FLAG_PINNED, &em->flags);
319 em->mod_start = em->start;
320 em->mod_len = em->len;
322 if (test_bit(EXTENT_FLAG_FILLING, &em->flags)) {
324 clear_bit(EXTENT_FLAG_FILLING, &em->flags);
327 try_merge_map(tree, em);
330 em->mod_start = em->start;
331 em->mod_len = em->len;
336 write_unlock(&tree->lock);
341 void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em)
343 lockdep_assert_held_write(&tree->lock);
345 clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
346 if (extent_map_in_tree(em))
347 try_merge_map(tree, em);
350 static inline void setup_extent_mapping(struct extent_map_tree *tree,
351 struct extent_map *em,
354 refcount_inc(&em->refs);
355 em->mod_start = em->start;
356 em->mod_len = em->len;
359 list_move(&em->list, &tree->modified_extents);
361 try_merge_map(tree, em);
364 static void extent_map_device_set_bits(struct extent_map *em, unsigned bits)
366 struct map_lookup *map = em->map_lookup;
367 u64 stripe_size = em->orig_block_len;
370 for (i = 0; i < map->num_stripes; i++) {
371 struct btrfs_io_stripe *stripe = &map->stripes[i];
372 struct btrfs_device *device = stripe->dev;
374 set_extent_bits_nowait(&device->alloc_state, stripe->physical,
375 stripe->physical + stripe_size - 1, bits);
379 static void extent_map_device_clear_bits(struct extent_map *em, unsigned bits)
381 struct map_lookup *map = em->map_lookup;
382 u64 stripe_size = em->orig_block_len;
385 for (i = 0; i < map->num_stripes; i++) {
386 struct btrfs_io_stripe *stripe = &map->stripes[i];
387 struct btrfs_device *device = stripe->dev;
389 __clear_extent_bit(&device->alloc_state, stripe->physical,
390 stripe->physical + stripe_size - 1, bits,
391 NULL, GFP_NOWAIT, NULL);
396 * Add new extent map to the extent tree
398 * @tree: tree to insert new map in
400 * @modified: indicate whether the given @em should be added to the
401 * modified list, which indicates the extent needs to be logged
403 * Insert @em into @tree or perform a simple forward/backward merge with
404 * existing mappings. The extent_map struct passed in will be inserted
405 * into the tree directly, with an additional reference taken, or a
406 * reference dropped if the merge attempt was successful.
408 int add_extent_mapping(struct extent_map_tree *tree,
409 struct extent_map *em, int modified)
413 lockdep_assert_held_write(&tree->lock);
415 ret = tree_insert(&tree->map, em);
419 setup_extent_mapping(tree, em, modified);
420 if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags)) {
421 extent_map_device_set_bits(em, CHUNK_ALLOCATED);
422 extent_map_device_clear_bits(em, CHUNK_TRIMMED);
428 static struct extent_map *
429 __lookup_extent_mapping(struct extent_map_tree *tree,
430 u64 start, u64 len, int strict)
432 struct extent_map *em;
433 struct rb_node *rb_node;
434 struct rb_node *prev_or_next = NULL;
435 u64 end = range_end(start, len);
437 rb_node = __tree_search(&tree->map.rb_root, start, &prev_or_next);
440 rb_node = prev_or_next;
445 em = rb_entry(rb_node, struct extent_map, rb_node);
447 if (strict && !(end > em->start && start < extent_map_end(em)))
450 refcount_inc(&em->refs);
455 * lookup_extent_mapping - lookup extent_map
456 * @tree: tree to lookup in
457 * @start: byte offset to start the search
458 * @len: length of the lookup range
460 * Find and return the first extent_map struct in @tree that intersects the
461 * [start, len] range. There may be additional objects in the tree that
462 * intersect, so check the object returned carefully to make sure that no
463 * additional lookups are needed.
465 struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
468 return __lookup_extent_mapping(tree, start, len, 1);
472 * search_extent_mapping - find a nearby extent map
473 * @tree: tree to lookup in
474 * @start: byte offset to start the search
475 * @len: length of the lookup range
477 * Find and return the first extent_map struct in @tree that intersects the
478 * [start, len] range.
480 * If one can't be found, any nearby extent may be returned
482 struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
485 return __lookup_extent_mapping(tree, start, len, 0);
489 * remove_extent_mapping - removes an extent_map from the extent tree
490 * @tree: extent tree to remove from
491 * @em: extent map being removed
493 * Removes @em from @tree. No reference counts are dropped, and no checks
494 * are done to see if the range is in use
496 void remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
498 lockdep_assert_held_write(&tree->lock);
500 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));
501 rb_erase_cached(&em->rb_node, &tree->map);
502 if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))
503 list_del_init(&em->list);
504 if (test_bit(EXTENT_FLAG_FS_MAPPING, &em->flags))
505 extent_map_device_clear_bits(em, CHUNK_ALLOCATED);
506 RB_CLEAR_NODE(&em->rb_node);
509 void replace_extent_mapping(struct extent_map_tree *tree,
510 struct extent_map *cur,
511 struct extent_map *new,
514 lockdep_assert_held_write(&tree->lock);
516 WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags));
517 ASSERT(extent_map_in_tree(cur));
518 if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags))
519 list_del_init(&cur->list);
520 rb_replace_node_cached(&cur->rb_node, &new->rb_node, &tree->map);
521 RB_CLEAR_NODE(&cur->rb_node);
523 setup_extent_mapping(tree, new, modified);
526 static struct extent_map *next_extent_map(struct extent_map *em)
528 struct rb_node *next;
530 next = rb_next(&em->rb_node);
533 return container_of(next, struct extent_map, rb_node);
536 static struct extent_map *prev_extent_map(struct extent_map *em)
538 struct rb_node *prev;
540 prev = rb_prev(&em->rb_node);
543 return container_of(prev, struct extent_map, rb_node);
547 * Helper for btrfs_get_extent. Given an existing extent in the tree,
548 * the existing extent is the nearest extent to map_start,
549 * and an extent that you want to insert, deal with overlap and insert
550 * the best fitted new extent into the tree.
552 static noinline int merge_extent_mapping(struct extent_map_tree *em_tree,
553 struct extent_map *existing,
554 struct extent_map *em,
557 struct extent_map *prev;
558 struct extent_map *next;
563 BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
565 if (existing->start > map_start) {
567 prev = prev_extent_map(next);
570 next = next_extent_map(prev);
573 start = prev ? extent_map_end(prev) : em->start;
574 start = max_t(u64, start, em->start);
575 end = next ? next->start : extent_map_end(em);
576 end = min_t(u64, end, extent_map_end(em));
577 start_diff = start - em->start;
579 em->len = end - start;
580 if (em->block_start < EXTENT_MAP_LAST_BYTE &&
581 !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
582 em->block_start += start_diff;
583 em->block_len = em->len;
585 return add_extent_mapping(em_tree, em, 0);
589 * Add extent mapping into em_tree
591 * @fs_info: the filesystem
592 * @em_tree: extent tree into which we want to insert the extent mapping
593 * @em_in: extent we are inserting
594 * @start: start of the logical range btrfs_get_extent() is requesting
595 * @len: length of the logical range btrfs_get_extent() is requesting
597 * Note that @em_in's range may be different from [start, start+len),
598 * but they must be overlapped.
600 * Insert @em_in into @em_tree. In case there is an overlapping range, handle
601 * the -EEXIST by either:
602 * a) Returning the existing extent in @em_in if @start is within the
604 * b) Merge the existing extent with @em_in passed in.
606 * Return 0 on success, otherwise -EEXIST.
609 int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
610 struct extent_map_tree *em_tree,
611 struct extent_map **em_in, u64 start, u64 len)
614 struct extent_map *em = *em_in;
616 ret = add_extent_mapping(em_tree, em, 0);
617 /* it is possible that someone inserted the extent into the tree
618 * while we had the lock dropped. It is also possible that
619 * an overlapping map exists in the tree
621 if (ret == -EEXIST) {
622 struct extent_map *existing;
626 existing = search_extent_mapping(em_tree, start, len);
628 trace_btrfs_handle_em_exist(fs_info, existing, em, start, len);
631 * existing will always be non-NULL, since there must be
632 * extent causing the -EEXIST.
634 if (start >= existing->start &&
635 start < extent_map_end(existing)) {
640 u64 orig_start = em->start;
641 u64 orig_len = em->len;
644 * The existing extent map is the one nearest to
645 * the [start, start + len) range which overlaps
647 ret = merge_extent_mapping(em_tree, existing,
653 "unexpected error %d: merge existing(start %llu len %llu) with em(start %llu len %llu)\n",
654 ret, existing->start, existing->len,
655 orig_start, orig_len);
657 free_extent_map(existing);
661 ASSERT(ret == 0 || ret == -EEXIST);
666 * Drop all extent maps from a tree in the fastest possible way, rescheduling
667 * if needed. This avoids searching the tree, from the root down to the first
668 * extent map, before each deletion.
670 static void drop_all_extent_maps_fast(struct extent_map_tree *tree)
672 write_lock(&tree->lock);
673 while (!RB_EMPTY_ROOT(&tree->map.rb_root)) {
674 struct extent_map *em;
675 struct rb_node *node;
677 node = rb_first_cached(&tree->map);
678 em = rb_entry(node, struct extent_map, rb_node);
679 clear_bit(EXTENT_FLAG_PINNED, &em->flags);
680 clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
681 remove_extent_mapping(tree, em);
683 cond_resched_rwlock_write(&tree->lock);
685 write_unlock(&tree->lock);
689 * Drop all extent maps in a given range.
691 * @inode: The target inode.
692 * @start: Start offset of the range.
693 * @end: End offset of the range (inclusive value).
694 * @skip_pinned: Indicate if pinned extent maps should be ignored or not.
696 * This drops all the extent maps that intersect the given range [@start, @end].
697 * Extent maps that partially overlap the range and extend behind or beyond it,
699 * The caller should have locked an appropriate file range in the inode's io
700 * tree before calling this function.
702 void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end,
705 struct extent_map *split;
706 struct extent_map *split2;
707 struct extent_map *em;
708 struct extent_map_tree *em_tree = &inode->extent_tree;
709 u64 len = end - start + 1;
711 WARN_ON(end < start);
712 if (end == (u64)-1) {
713 if (start == 0 && !skip_pinned) {
714 drop_all_extent_maps_fast(em_tree);
719 /* Make end offset exclusive for use in the loop below. */
724 * It's ok if we fail to allocate the extent maps, see the comment near
725 * the bottom of the loop below. We only need two spare extent maps in
726 * the worst case, where the first extent map that intersects our range
727 * starts before the range and the last extent map that intersects our
728 * range ends after our range (and they might be the same extent map),
729 * because we need to split those two extent maps at the boundaries.
731 split = alloc_extent_map();
732 split2 = alloc_extent_map();
734 write_lock(&em_tree->lock);
735 em = lookup_extent_mapping(em_tree, start, len);
738 /* extent_map_end() returns exclusive value (last byte + 1). */
739 const u64 em_end = extent_map_end(em);
740 struct extent_map *next_em = NULL;
747 next_em = next_extent_map(em);
749 if (next_em->start < end)
750 refcount_inc(&next_em->refs);
756 if (skip_pinned && test_bit(EXTENT_FLAG_PINNED, &em->flags)) {
759 len = start + len - em_end;
763 clear_bit(EXTENT_FLAG_PINNED, &em->flags);
764 clear_bit(EXTENT_FLAG_LOGGING, &flags);
765 modified = !list_empty(&em->list);
768 * The extent map does not cross our target range, so no need to
769 * split it, we can remove it directly.
771 if (em->start >= start && em_end <= end)
775 gen = em->generation;
776 compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
778 if (em->start < start) {
785 split->start = em->start;
786 split->len = start - em->start;
788 if (em->block_start < EXTENT_MAP_LAST_BYTE) {
789 split->orig_start = em->orig_start;
790 split->block_start = em->block_start;
793 split->block_len = em->block_len;
795 split->block_len = split->len;
796 split->orig_block_len = max(split->block_len,
798 split->ram_bytes = em->ram_bytes;
800 split->orig_start = split->start;
801 split->block_len = 0;
802 split->block_start = em->block_start;
803 split->orig_block_len = 0;
804 split->ram_bytes = split->len;
807 split->generation = gen;
808 split->flags = flags;
809 split->compress_type = em->compress_type;
810 replace_extent_mapping(em_tree, em, split, modified);
811 free_extent_map(split);
822 split->start = start + len;
823 split->len = em_end - (start + len);
824 split->block_start = em->block_start;
825 split->flags = flags;
826 split->compress_type = em->compress_type;
827 split->generation = gen;
829 if (em->block_start < EXTENT_MAP_LAST_BYTE) {
830 split->orig_block_len = max(em->block_len,
833 split->ram_bytes = em->ram_bytes;
835 split->block_len = em->block_len;
836 split->orig_start = em->orig_start;
838 const u64 diff = start + len - em->start;
840 split->block_len = split->len;
841 split->block_start += diff;
842 split->orig_start = em->orig_start;
845 split->ram_bytes = split->len;
846 split->orig_start = split->start;
847 split->block_len = 0;
848 split->orig_block_len = 0;
851 if (extent_map_in_tree(em)) {
852 replace_extent_mapping(em_tree, em, split,
857 ret = add_extent_mapping(em_tree, split,
859 /* Logic error, shouldn't happen. */
861 if (WARN_ON(ret != 0) && modified)
862 btrfs_set_inode_full_sync(inode);
864 free_extent_map(split);
868 if (extent_map_in_tree(em)) {
870 * If the extent map is still in the tree it means that
871 * either of the following is true:
873 * 1) It fits entirely in our range (doesn't end beyond
874 * it or starts before it);
876 * 2) It starts before our range and/or ends after our
877 * range, and we were not able to allocate the extent
878 * maps for split operations, @split and @split2.
880 * If we are at case 2) then we just remove the entire
881 * extent map - this is fine since if anyone needs it to
882 * access the subranges outside our range, will just
883 * load it again from the subvolume tree's file extent
884 * item. However if the extent map was in the list of
885 * modified extents, then we must mark the inode for a
886 * full fsync, otherwise a fast fsync will miss this
887 * extent if it's new and needs to be logged.
889 if ((em->start < start || em_end > end) && modified) {
891 btrfs_set_inode_full_sync(inode);
893 remove_extent_mapping(em_tree, em);
897 * Once for the tree reference (we replaced or removed the
898 * extent map from the tree).
902 /* Once for us (for our lookup reference). */
908 write_unlock(&em_tree->lock);
910 free_extent_map(split);
911 free_extent_map(split2);
915 * Replace a range in the inode's extent map tree with a new extent map.
917 * @inode: The target inode.
918 * @new_em: The new extent map to add to the inode's extent map tree.
919 * @modified: Indicate if the new extent map should be added to the list of
920 * modified extents (for fast fsync tracking).
922 * Drops all the extent maps in the inode's extent map tree that intersect the
923 * range of the new extent map and adds the new extent map to the tree.
924 * The caller should have locked an appropriate file range in the inode's io
925 * tree before calling this function.
927 int btrfs_replace_extent_map_range(struct btrfs_inode *inode,
928 struct extent_map *new_em,
931 const u64 end = new_em->start + new_em->len - 1;
932 struct extent_map_tree *tree = &inode->extent_tree;
935 ASSERT(!extent_map_in_tree(new_em));
938 * The caller has locked an appropriate file range in the inode's io
939 * tree, but getting -EEXIST when adding the new extent map can still
940 * happen in case there are extents that partially cover the range, and
941 * this is due to two tasks operating on different parts of the extent.
942 * See commit 18e83ac75bfe67 ("Btrfs: fix unexpected EEXIST from
943 * btrfs_get_extent") for an example and details.
946 btrfs_drop_extent_map_range(inode, new_em->start, end, false);
947 write_lock(&tree->lock);
948 ret = add_extent_mapping(tree, new_em, modified);
949 write_unlock(&tree->lock);
950 } while (ret == -EEXIST);