diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/extent_map.c | 31 |
1 files changed, 16 insertions, 15 deletions
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 25d191f1ac10..668c617444a5 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -243,13 +243,19 @@ static bool mergeable_maps(const struct extent_map *prev, const struct extent_ma /* * Handle the on-disk data extents merge for @prev and @next. * + * @prev: left extent to merge + * @next: right extent to merge + * @merged: the extent we will not discard after the merge; updated with new values + * + * After this, one of the two extents is the new merged extent and the other is + * removed from the tree and likely freed. Note that @merged is one of @prev/@next + * so there is const/non-const aliasing occurring here. + * * Only touches disk_bytenr/disk_num_bytes/offset/ram_bytes. * For now only uncompressed regular extent can be merged. - * - * @prev and @next will be both updated to point to the new merged range. - * Thus one of them should be removed by the caller. */ -static void merge_ondisk_extents(struct extent_map *prev, struct extent_map *next) +static void merge_ondisk_extents(const struct extent_map *prev, const struct extent_map *next, + struct extent_map *merged) { u64 new_disk_bytenr; u64 new_disk_num_bytes; @@ -284,15 +290,10 @@ static void merge_ondisk_extents(struct extent_map *prev, struct extent_map *nex new_disk_bytenr; new_offset = prev->disk_bytenr + prev->offset - new_disk_bytenr; - prev->disk_bytenr = new_disk_bytenr; - prev->disk_num_bytes = new_disk_num_bytes; - prev->ram_bytes = new_disk_num_bytes; - prev->offset = new_offset; - - next->disk_bytenr = new_disk_bytenr; - next->disk_num_bytes = new_disk_num_bytes; - next->ram_bytes = new_disk_num_bytes; - next->offset = new_offset; + merged->disk_bytenr = new_disk_bytenr; + merged->disk_num_bytes = new_disk_num_bytes; + merged->ram_bytes = new_disk_num_bytes; + merged->offset = new_offset; } static void dump_extent_map(struct btrfs_fs_info *fs_info, const char *prefix, @@ -361,7 +362,7 @@ static void try_merge_map(struct btrfs_inode *inode, struct extent_map *em) em->generation = max(em->generation, merge->generation); if (em->disk_bytenr < EXTENT_MAP_LAST_BYTE) - merge_ondisk_extents(merge, em); + merge_ondisk_extents(merge, em, em); em->flags |= EXTENT_FLAG_MERGED; validate_extent_map(fs_info, em); @@ -378,7 +379,7 @@ static void try_merge_map(struct btrfs_inode *inode, struct extent_map *em) if (rb && can_merge_extent_map(merge) && mergeable_maps(em, merge)) { em->len += merge->len; if (em->disk_bytenr < EXTENT_MAP_LAST_BYTE) - merge_ondisk_extents(em, merge); + merge_ondisk_extents(em, merge, em); validate_extent_map(fs_info, em); rb_erase(&merge->rb_node, &tree->root); RB_CLEAR_NODE(&merge->rb_node); |