Btrfs: fix incorrect block_len in merge_extent_mapping

%block_len could be checked on deciding if two em are mergeable.

merge_extent_mapping() has only added the front pad if the front part
of em gets truncated, but it's possible that the end part gets
truncated.

For both compressed extent and inline extent, em->block_len is not
adjusted accordingly, and for regular extent, em->block_len always
equals to em->len, hence this sets em->block_len with em->len.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 633b83b709a1dd9319346adf698839d578d1c67a..f9fd8b14ef08daca08a5e881463083d0b122ac20 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6874,7 +6874,7 @@ static int merge_extent_mapping(struct extent_map_tree *em_tree,
        if (em->block_start < EXTENT_MAP_LAST_BYTE &&
            !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
                em->block_start += start_diff;
-               em->block_len -= start_diff;
+               em->block_len = em->len;
        }
        return add_extent_mapping(em_tree, em, 0);
 }