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

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Message-ID: <41409fd5-2df1-ab1d-848a-3b14e9983338@redhat.com>
Date: Tue, 26 Aug 2025 16:50:12 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Zheng Qixing <zhengqixing@...weicloud.com>
cc: agk@...hat.com, snitzer@...nel.org, axboe@...nel.dk, ming.lei@...hat.com, 
    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: Re: [PATCH-next 0/2] dm: fix quiesce asymmetry and null pointer in
 suspend/load race



On Tue, 26 Aug 2025, Zheng Qixing wrote:

> 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

Both patches applied, thanks.

Mikulas