linux-kernel - Re: [PATCH] f2fs: Fix deadlock in shutdown ioctl

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Message-ID: <20180515075747.GA6293@codeaurora.org>
Date:   Tue, 15 May 2018 13:27:47 +0530
From:   Sahitya Tummala <stummala@...eaurora.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: Fix deadlock in shutdown ioctl

On Mon, May 14, 2018 at 11:39:42AM +0800, Chao Yu wrote:
> On 2018/5/10 21:20, Sahitya Tummala wrote:
> > f2fs_ioc_shutdown() ioctl gets stuck in the below path
> > when going down with full sync (F2FS_GOING_DOWN_FULLSYNC)
> > option.
> > 
> > __switch_to+0x90/0xc4
> > percpu_down_write+0x8c/0xc0
> > freeze_super+0xec/0x1e4
> > freeze_bdev+0xc4/0xcc
> > f2fs_ioctl+0xc0c/0x1ce0
> > f2fs_compat_ioctl+0x98/0x1f0
> > 
> > Fix this by not holding write access during this ioctl.
> 
> I think we can just remove lock coverage for F2FS_GOING_DOWN_FULLSYNC path, for
> other path, we need to keep as it is.
>

Thanks, I thought about it too but then I checked that XFS shutdown ioctl is
not taking any lock for this ioctl. Hence, I followed the same in F2FS.
Do you know why XFS is not taking any lock? Is it really needed in shutdown
ioctl?

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