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From: Chao Yu <chao@kernel.org>
To: Wenjie Qi <qwjhust@gmail.com>, jaegeuk@kernel.org
Cc: chao@kernel.org, linux-f2fs-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, qiwenjie@xiaomi.com,
	stable@kernel.org
Subject: Re: [PATCH v3 1/2] f2fs: avoid NULL checkpoint thread access in sysfs
Date: Tue, 4 Aug 2026 08:03:55 +0800	[thread overview]
Message-ID: <1c7a599a-2a9a-44f0-9d03-cb1c87f81cd3@kernel.org> (raw)
In-Reply-To: <20260803123251.1522864-1-qiwenjie@xiaomi.com>

On 8/3/26 20:32, Wenjie Qi wrote:
> checkpoint_merge can be enabled even when no checkpoint merge thread is
> running. A read-only mount is one case: f2fs does not start
> f2fs_issue_ckpt there, but ckpt_thread_ioprio is still writable through
> sysfs.
> 
> The ckpt_thread_ioprio store path updates the saved ioprio value and,
> when checkpoint_merge is enabled, calls set_task_ioprio() for the
> checkpoint thread. If cprc->f2fs_issue_ckpt is NULL, that dereferences a
> NULL task pointer.
> 
> Protect ckpt_thread_ioprio sysfs writes with s_umount as well, so the
> checkpoint thread cannot disappear under the store path while updating
> its ioprio.
> 
> Fixes: e65920661708 ("f2fs: add ckpt_thread_ioprio sysfs node")
> Cc: stable@kernel.org
> Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,

      parent reply	other threads:[~2026-08-04  0:03 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-03 12:32 Wenjie Qi
2026-08-03 12:32 ` [PATCH v3 2/2] f2fs: protect critical_task_priority updates with s_umount Wenjie Qi
2026-08-04  0:04   ` Chao Yu
2026-08-04  0:03 ` Chao Yu [this message]

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