Re: [PATCH] blkcg: Unlock blkcg_pol_mutex once if cpd == NULL

Unlocking a mutex twice is wrong. Hence modify blkcg_policy_register()
such that blkcg_pol_mutex is unlocked once if cpd == NULL. This patch
avoids that smatch reports the following error:

block/blk-cgroup.c:1378: blkcg_policy_register() error: double unlock 'mutex:&blkcg_pol_mutex'

Signed-off-by: Bart Van Assche <redacted>
Cc: Tejun Heo <tj@kernel.org>
Cc: <redacted>
---
 block/blk-cgroup.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index dd38e5c..cdbca1c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c

@@ -1327,8 +1327,10 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 	for (i = 0; i < BLKCG_MAX_POLS; i++)
 		if (!blkcg_policy[i])
 			break;
-	if (i >= BLKCG_MAX_POLS)
+	if (i >= BLKCG_MAX_POLS) {
+		mutex_unlock(&blkcg_pol_mutex);
 		goto err_unlock;
+	}