From: Marcos Paulo de Souza mpdesouza@suse.com
commit e3e39c72b99f93bbd0420d38c858e7c4a061bb63 upstream.
[BUG] After commit 9afc66498a0b ("btrfs: block-group: refactor how we read one block group item"), cache->length is being assigned after calling btrfs_create_block_group_cache. This causes a problem since set_free_space_tree_thresholds calculates the free-space threshold to decide if the free-space tree should convert from extents to bitmaps.
The current code calls set_free_space_tree_thresholds with cache->length being 0, which then makes cache->bitmap_high_thresh zero. This implies the system will always use bitmap instead of extents, which is not desired if the block group is not fragmented.
This behavior can be seen by a test that expects to repair systems with FREE_SPACE_EXTENT and FREE_SPACE_BITMAP, but the current code only created FREE_SPACE_BITMAP.
[FIX] Call set_free_space_tree_thresholds after setting cache->length. There is now a WARN_ON in set_free_space_tree_thresholds to help preventing the same mistake to happen again in the future.
Link: https://github.com/kdave/btrfs-progs/issues/251 Fixes: 9afc66498a0b ("btrfs: block-group: refactor how we read one block group item") CC: stable@vger.kernel.org # 5.8+ Reviewed-by: Qu Wenruo wqu@suse.com Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Marcos Paulo de Souza mpdesouza@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/block-group.c | 4 +++- fs/btrfs/free-space-tree.c | 4 ++++ 2 files changed, 7 insertions(+), 1 deletion(-)
--- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1814,7 +1814,6 @@ static struct btrfs_block_group *btrfs_c
cache->fs_info = fs_info; cache->full_stripe_len = btrfs_full_stripe_len(fs_info, start); - set_free_space_tree_thresholds(cache);
cache->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
@@ -1928,6 +1927,8 @@ static int read_one_block_group(struct b if (ret < 0) goto error;
+ set_free_space_tree_thresholds(cache); + if (need_clear) { /* * When we mount with old space cache, we need to @@ -2148,6 +2149,7 @@ int btrfs_make_block_group(struct btrfs_ return -ENOMEM;
cache->length = size; + set_free_space_tree_thresholds(cache); cache->used = bytes_used; cache->flags = type; cache->last_byte_to_unpin = (u64)-1; --- a/fs/btrfs/free-space-tree.c +++ b/fs/btrfs/free-space-tree.c @@ -22,6 +22,10 @@ void set_free_space_tree_thresholds(stru size_t bitmap_size; u64 num_bitmaps, total_bitmap_size;
+ if (WARN_ON(cache->length == 0)) + btrfs_warn(cache->fs_info, "block group %llu length is zero", + cache->start); + /* * We convert to bitmaps when the disk space required for using extents * exceeds that required for using bitmaps.