linux-kernel - [PATCH-next 0/2] dm: fix quiesce asymmetry and null pointer in suspend/load race

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Message-Id: <20250826074204.390111-1-zhengqixing@huaweicloud.com>
Date: Tue, 26 Aug 2025 15:42:02 +0800
From: Zheng Qixing <zhengqixing@...weicloud.com>
To: agk@...hat.com,
	snitzer@...nel.org,
	mpatocka@...hat.com,
	axboe@...nel.dk,
	ming.lei@...hat.com
Cc: dm-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	houtao1@...wei.com,
	zhengqixing@...wei.com
Subject: [PATCH-next 0/2] dm: fix quiesce asymmetry and null pointer in suspend/load race

From: Zheng Qixing <zhengqixing@...wei.com>

Hello,

During reliability testing of the dm module, we discovered two bugs when
performing create/remove and suspend/resume operations at high frequency.

Analysis revealed that race conditions between suspend and table load
operations cause asymmetric handling of q->quiesce_depth and null pointer
dereference issues with q->tag_set.

To address the q->tag_set null pointer issue, patch 2 determines whether
to perform certain suspend actions for request-based devices based on the
existence of the table (map).

For detailed information, please refer to the patch commits.

Additionally, since modern Linux kernels have indeed transitioned to
multi-queue as the default (and single-queue is largely deprecated),
is using queue_is_mq() to determine dm_request_based() obsolete?

Zheng Qixing (2):
  dm: fix queue start/stop imbalance under suspend/load/resume races
  dm: fix NULL pointer dereference in __dm_suspend()

 drivers/md/dm-core.h |  1 +
 drivers/md/dm.c      | 13 ++++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

-- 
2.39.2