linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: do checkpoint in kill

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Date:   Mon, 9 Jul 2018 23:04:51 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: do checkpoint in kill_sb

On 2018/7/7 9:20, Jaegeuk Kim wrote:
> When unmounting f2fs in force mode, we can get it stuck by io_schedule()

force mode means force shutdown?

> by some pending IOs in meta_inode.
> 
> io_schedule+0xd/0x30
> wait_on_page_bit_common+0xc6/0x130

Looks like a deadlock here? Does this mean we forget to submit cached bio in
somewhere?

Thanks,

> __filemap_fdatawait_range+0xbd/0x100
> filemap_fdatawait_keep_errors+0x15/0x40
> sync_inodes_sb+0x1cf/0x240
> sync_filesystem+0x52/0x90
> generic_shutdown_super+0x1d/0x110
> ceph_kill_sb+0x28/0x80 [ceph]
> deactivate_locked_super+0x35/0x60
> cleanup_mnt+0x36/0x70
> task_work_run+0x79/0xa0
> exit_to_usermode_loop+0x62/0x70
> do_syscall_64+0xdb/0xf0
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 0xffffffffffffffff
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
>  fs/f2fs/super.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 3995e926ba3a..1dc6809fac38 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3089,9 +3089,19 @@ static struct dentry *f2fs_mount(struct file_system_type *fs_type, int flags,
>  static void kill_f2fs_super(struct super_block *sb)
>  {
>  	if (sb->s_root) {
> -		set_sbi_flag(F2FS_SB(sb), SBI_IS_CLOSE);
> -		f2fs_stop_gc_thread(F2FS_SB(sb));
> -		f2fs_stop_discard_thread(F2FS_SB(sb));
> +		struct f2fs_sb_info *sbi = F2FS_SB(sb);
> +
> +		set_sbi_flag(sbi, SBI_IS_CLOSE);
> +		f2fs_stop_gc_thread(sbi);
> +		f2fs_stop_discard_thread(sbi);
> +
> +		if (is_sbi_flag_set(sbi, SBI_IS_DIRTY) ||
> +				!is_set_ckpt_flags(sbi, CP_UMOUNT_FLAG)) {
> +			struct cp_control cpc = {
> +				.reason = CP_UMOUNT,
> +			};
> +			f2fs_write_checkpoint(sbi, &cpc);
> +		}
>  	}
>  	kill_block_super(sb);
>  }
>