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

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Date:   Mon, 14 May 2018 11:39:42 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Sahitya Tummala <stummala@...eaurora.org>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: Fix deadlock in shutdown ioctl

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,

> 
> Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
> ---
>  fs/f2fs/file.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index b926df7..2c2e61b 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1835,10 +1835,6 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
>  	if (get_user(in, (__u32 __user *)arg))
>  		return -EFAULT;
>  
> -	ret = mnt_want_write_file(filp);
> -	if (ret)
> -		return ret;
> -
>  	switch (in) {
>  	case F2FS_GOING_DOWN_FULLSYNC:
>  		sb = freeze_bdev(sb->s_bdev);
> @@ -1878,7 +1874,6 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
>  
>  	f2fs_update_time(sbi, REQ_TIME);
>  out:
> -	mnt_drop_write_file(filp);
>  	return ret;
>  }
>  
>