Re: [PATCH] f2fs: Fix deadlock in shutdown ioctl

From: Chao Yu
Date: Sun May 13 2018 - 23:39:52 EST


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@xxxxxxxxxxxxxx>
> ---
> 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;
> }
>
>