linux-kernel - Re: [PATCH v2] f2fs: Fix deadlock in shutdown ioctl

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Message-ID: <b7d045f3-f37b-46da-3c1c-2b6d99efc9e7@huawei.com>
Date:   Thu, 17 May 2018 19:12:43 +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 v2] f2fs: Fix deadlock in shutdown ioctl

On 2018/5/17 16:03, Sahitya Tummala wrote:
> f2fs_ioc_shutdown() ioctl gets stuck in the below path
> when issued with 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
> 
> Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
> ---
> v2:
> remove lock coverage for only F2FS_GOING_DOWN_FULLSYNC case as suggested by Chao.
> 
>  fs/f2fs/file.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6b94f19..5a132c9 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1857,6 +1857,7 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)

How about:

if (in != F2FS_GOING_DOWN_FULLSYNC)
	mnt_want_write_file();

switch()
{
	handle command;
}

if (in != F2FS_GOING_DOWN_FULLSYNC)
	mnt_drop_write_file();

Thanks,

>  
>  	switch (in) {
>  	case F2FS_GOING_DOWN_FULLSYNC:
> +		mnt_drop_write_file(filp);
>  		sb = freeze_bdev(sb->s_bdev);
>  		if (IS_ERR(sb)) {
>  			ret = PTR_ERR(sb);
> @@ -1894,7 +1895,8 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg)
>  
>  	f2fs_update_time(sbi, REQ_TIME);
>  out:
> -	mnt_drop_write_file(filp);
> +	if (in != F2FS_GOING_DOWN_FULLSYNC)
> +		mnt_drop_write_file(filp);
>  	return ret;
>  }
>  
>