blkcg: Unlock blkcg_pol_mutex only once when 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'

Fixes: 06b285bd1125 ("blkcg: fix blkcg_policy_data allocation bug")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org> # v4.2+
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index dd38e5c..b08ccbb 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1340,10 +1340,8 @@ int blkcg_policy_register(struct blkcg_policy *pol)
                        struct blkcg_policy_data *cpd;
 
                        cpd = pol->cpd_alloc_fn(GFP_KERNEL);
-                       if (!cpd) {
-                               mutex_unlock(&blkcg_pol_mutex);
+                       if (!cpd)
                                goto err_free_cpds;
-                       }
 
                        blkcg->cpd[pol->plid] = cpd;
                        cpd->blkcg = blkcg;