• Marcos Paulo de Souza's avatar
    btrfs: block-group: fix free-space bitmap threshold · e3e39c72
    Marcos Paulo de Souza authored
    [BUG]
    After commit 9afc6649 ("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: 9afc6649 ("btrfs: block-group: refactor how we read one block group item")
    CC: stable@vger.kernel.org # 5.8+
    Reviewed-by: default avatarQu Wenruo <wqu@suse.com>
    Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
    Signed-off-by: default avatarMarcos Paulo de Souza <mpdesouza@suse.com>
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    e3e39c72
free-space-tree.c 39.3 KB