linux-kernel - Re: [PATCH] f2fs: avoid the deadlock case when stopping discard thread

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240321224233.2541-1-hdanton@sina.com>
Date: Fri, 22 Mar 2024 06:42:33 +0800
From: Hillf Danton <hdanton@...a.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Light Hsieh (謝明燈) <Light.Hsieh@...iatek.com>,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH] f2fs: avoid the deadlock case when stopping discard thread

On Tue, 19 Mar 2024 17:14:42 -0700 Jaegeuk Kim <jaegeuk@...nel.org>
> f2fs_ioc_shutdown(F2FS_GOING_DOWN_NOSYNC)  issue_discard_thread
>  - mnt_want_write_file()
>    - sb_start_write(SB_FREEZE_WRITE)
	 __sb_start_write()
	   percpu_down_read()
>                                              - sb_start_intwrite(SB_FREEZE_FS);
						   __sb_start_write()
						     percpu_down_read()

Given lock acquirers for read on both sides, wtf deadlock are you fixing?

>  - f2fs_stop_checkpoint(sbi, false,            : waiting
>     STOP_CP_REASON_SHUTDOWN);
>  - f2fs_stop_discard_thread(sbi);
>    - kthread_stop()
>      : waiting
> 
>  - mnt_drop_write_file(filp);

More important, feel free to add in spin.

	Reported-by: "Light Hsieh (謝明燈)" <Light.Hsieh@...iatek.com>