bcache: return attach error when no cache set exist

[ Upstream commit 7f4fc93 ]

I attach a back-end device to a cache set, and the cache set is not
registered yet, this back-end device did not attach successfully, and no
error returned:
[root]# echo 87859280-fec6-4bcc-20df7ca8f86b > /sys/block/sde/bcache/attach
[root]#

In sysfs_attach(), the return value "v" is initialized to "size" in
the beginning, and if no cache set exist in bch_cache_sets, the "v" value
would not change any more, and return to sysfs, sysfs regard it as success
since the "size" is a positive number.

This patch fixes this issue by assigning "v" with "-ENOENT" in the
initialization.

Signed-off-by: Tang Junhui <[email protected]>
Reviewed-by: Michael Lyle <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Tang Junhui

drivers/md/bcache/sysfs.c

@@ -193,7 +193,7 @@ STORE(__cached_dev)
 {
 	struct cached_dev *dc = container_of(kobj, struct cached_dev,
 					     disk.kobj);
-	ssize_t v = size;
+	ssize_t v;
 	struct cache_set *c;
 	struct kobj_uevent_env *env;
 
@@ -270,14 +270,15 @@ STORE(__cached_dev)
 		if (bch_parse_uuid(buf, set_uuid) < 16)
 			return -EINVAL;
 
+		v = -ENOENT;
 		list_for_each_entry(c, &bch_cache_sets, list) {
 			v = bch_cached_dev_attach(dc, c, set_uuid);
 			if (!v)
 				return size;
 		}
 
 		pr_err("Can't attach %s: cache set not found", buf);
-		size = v;
+		return v;
 	}
 
 	if (attr == &sysfs_detach && dc->disk.c)