From: Christoph Hellwig <hch@xxxxxx> [ Upstream commit 4e7de35eb7d1a1d4f2dda15f39fbedd4798a0b8d ] The mirror_num_ret is allowed to be NULL, although it has to be set when smap is set. Unfortunately that is not a well enough specifiable invariant for static type checkers, so add a NULL check to make sure they are fine. Fixes: 03793cbbc80f ("btrfs: add fast path for single device io in __btrfs_map_block") Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Reviewed-by: Qu Wenruo <wqu@xxxxxxxx> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx> Signed-off-by: Christoph Hellwig <hch@xxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/btrfs/volumes.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 7433ae929fdcb..2e0832d70406c 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -6595,11 +6595,13 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, if (patch_the_first_stripe_for_dev_replace) { smap->dev = dev_replace->tgtdev; smap->physical = physical_to_patch_in_first_stripe; - *mirror_num_ret = map->num_stripes + 1; + if (mirror_num_ret) + *mirror_num_ret = map->num_stripes + 1; } else { set_io_stripe(smap, map, stripe_index, stripe_offset, stripe_nr); - *mirror_num_ret = mirror_num; + if (mirror_num_ret) + *mirror_num_ret = mirror_num; } *bioc_ret = NULL; ret = 0; -- 2.39.2