linux-kernel - [PATCH v2 1/2] blk-cgroup: Correctly free percpu iostat

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Message-Id: <20220601165324.60892-1-longman@redhat.com>
Date:   Wed,  1 Jun 2022 12:53:23 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ming Lei <ming.lei@...hat.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v2 1/2] blk-cgroup: Correctly free percpu iostat_cpu in blkg on error exit

Commit f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup
rstat") changes block cgroup IO stats to use the rstat APIs. It added
a new percpu iostat_cpu field into blkg. The blkg_alloc() was modified
to allocate the new percpu iostat_cpu but didn't free it when an error
happened. Fix this by freeing the percpu iostat_cpu on error exit.

Fixes: f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat")
Signed-off-by: Waiman Long <longman@...hat.com>
---
 block/blk-cgroup.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 40161a3f68d0..acd9b0aa8dc8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -219,11 +219,11 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 		return NULL;
 
 	if (percpu_ref_init(&blkg->refcnt, blkg_release, 0, gfp_mask))
-		goto err_free;
+		goto err_free_blkg;
 
 	blkg->iostat_cpu = alloc_percpu_gfp(struct blkg_iostat_set, gfp_mask);
 	if (!blkg->iostat_cpu)
-		goto err_free;
+		goto err_free_blkg;
 
 	if (!blk_get_queue(q))
 		goto err_free;
@@ -259,6 +259,9 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 	return blkg;
 
 err_free:
+	free_percpu(blkg->iostat_cpu);
+
+err_free_blkg:
 	blkg_free(blkg);
 	return NULL;
 }
-- 
2.31.1