btrfs: be a bit more careful when setting mirror_num_ret in btrfs_map…

…_block 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: 03793cb ("btrfs: add fast path for single device io in __btrfs_map_block") Reported-by: Dan Carpenter <[email protected]> Reviewed-by: Qu Wenruo <[email protected]> Reviewed-by: Johannes Thumshirn <[email protected]> Signed-off-by: Christoph Hellwig <[email protected]> Reviewed-by: David Sterba <[email protected]> Signed-off-by: David Sterba <[email protected]>
SamirMulani · Jul 11, 2023 · 4e7de35 · 4e7de35
1 parent b19c98f
commit 4e7de35
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
@@ -6398,7 +6398,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 	    (op == BTRFS_MAP_READ || !dev_replace_is_ongoing ||
 	     !dev_replace->tgtdev)) {
 		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;
 		goto out;