linux-kernel - [PATCH 2/7] blkcg: use blkg_free() in blkcg_init

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Date:	Tue,  7 Jul 2015 11:51:28 -0400
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk
Cc:	jack@...e.cz, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, kernel-team@...com, vgoyal@...hat.com,
	avanzini.arianna@...il.com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/7] blkcg: use blkg_free() in blkcg_init_queue() failure path

When blkcg_init_queue() fails midway after creating a new blkg, it
performs kfree() directly; however, this doesn't free the policy data
areas.  Make it use blkg_free() instead.  In turn, blkg_free() is
updated to handle root request_list special case.

While this fixes a possible memory leak, it's on an unlikely failure
path of an already cold path and the size leaked per occurrence is
miniscule too.  I don't think it needs to be tagged for -stable.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Vivek Goyal <vgoyal@...hat.com>
---
 block/blk-cgroup.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index dacd95d..73209a8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -60,7 +60,8 @@ static void blkg_free(struct blkcg_gq *blkg)
 	for (i = 0; i < BLKCG_MAX_POLS; i++)
 		kfree(blkg->pd[i]);
 
-	blk_exit_rl(&blkg->rl);
+	if (blkg->blkcg != &blkcg_root)
+		blk_exit_rl(&blkg->rl);
 	kfree(blkg);
 }
 
@@ -923,7 +924,7 @@ int blkcg_init_queue(struct request_queue *q)
 		radix_tree_preload_end();
 
 	if (IS_ERR(blkg)) {
-		kfree(new_blkg);
+		blkg_free(new_blkg);
 		return PTR_ERR(blkg);
 	}
 
-- 
2.4.3

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