linux-kernel - [PATCH] blk-throttle: fix throtl

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Message-Id: <20250916010947.2891471-1-yukuai1@huaweicloud.com>
Date: Tue, 16 Sep 2025 09:09:47 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: tj@...nel.org,
	josef@...icpanda.com,
	axboe@...nel.dk,
	liangjie@...iang.com,
	yukuai3@...wei.com,
	hanguangjiang@...iang.com
Cc: cgroups@...r.kernel.org,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	yukuai1@...weicloud.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	johnny.chenyi@...wei.com
Subject: [PATCH] blk-throttle: fix throtl_data leak during disk release

From: Yu Kuai <yukuai3@...wei.com>

Tightening the throttle activation check in blk_throtl_activated() to
require both q->td presence and policy bit set introduced a memory leak
during disk release:

blkg_destroy_all() clears the policy bit first during queue deactivation,
causing subsequent blk_throtl_exit() to skip throtl_data cleanup when
blk_throtl_activated() fails policy check.

Fix by reordering operations in disk_release() to call blk_throtl_exit()
while throttle policy is still active. We avoid modifying blk_throtl_exit()
activation check because it's intuitive that blk-throtl start from
blk_throtl_init() and end in blk_throtl_exit().

Fixes: bd9fd5be6bc0 ("blk-throttle: fix access race during throttle policy activation")
Reported-by: Yi Zhang <yi.zhang@...hat.com>
Closes: https://lore.kernel.org/all/CAHj4cs-p-ZwBEKigBj7T6hQCOo-H68-kVwCrV6ZvRovrr9Z+HA@mail.gmail.com/
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 7246fc256315..64a56c8697f9 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1539,8 +1539,8 @@ int blkcg_init_disk(struct gendisk *disk)
 
 void blkcg_exit_disk(struct gendisk *disk)
 {
-	blkg_destroy_all(disk);
 	blk_throtl_exit(disk);
+	blkg_destroy_all(disk);
 }
 
 static void blkcg_exit(struct task_struct *tsk)
-- 
2.39.2