From: Bart Van Assche <bart.vanassche@sandisk.com>
Date: Thu, 29 Sep 2016 15:33:30 +0000 (-0700)
Subject: blkcg: Unlock blkcg_pol_mutex only once when cpd == NULL
X-Git-Tag: firefly_0821_release~176^2~4^2~22^2~31
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6d4c93affe9e3ee9c61404fc6aa7f45ba3aba40f;p=firefly-linux-kernel-4.4.55.git

blkcg: Unlock blkcg_pol_mutex only once when cpd == NULL

commit bbb427e342495df1cda10051d0566388697499c0 upstream.

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>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 5a37188b559f..9d359e05fad7 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1331,10 +1331,8 @@ 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;