linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: reset free segment to prefree status when do

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Message-ID: <YPXDtEyBg5W2ToD/@google.com>
Date:   Mon, 19 Jul 2021 11:25:56 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     Yangtao Li <frank.li@...o.com>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: reset free segment to prefree status
 when do_checkpoint() fail

On 07/19, Chao Yu wrote:
> On 2021/4/27 20:37, Chao Yu wrote:
> > I think just reverting dirty/free bitmap is not enough if checkpoint fails,
> > due to we have updated sbi->cur_cp_pack and nat/sit bitmap, next CP tries
> > to overwrite last valid meta/node/data, then filesystem will be corrupted.
> > 
> > So I suggest to set cp_error if do_checkpoint() fails until we can handle
> > all cases, which is not so easy.
> > 
> > How do you think?
> 
> Let's add below patch first before you figure out the patch which covers all
> things.
> 
> From 3af957c98e9e04259f8bb93ca0b74ba164f3f27e Mon Sep 17 00:00:00 2001
> From: Chao Yu <chao@...nel.org>
> Date: Mon, 19 Jul 2021 16:37:44 +0800
> Subject: [PATCH] f2fs: fix to stop filesystem update once CP failed
> 
> During f2fs_write_checkpoint(), once we failed in
> f2fs_flush_nat_entries() or do_checkpoint(), metadata of filesystem
> such as prefree bitmap, nat/sit version bitmap won't be recovered,
> it may cause f2fs image to be inconsistent, let's just set CP error
> flag to avoid further updates until we figure out a scheme to rollback
> all metadatas in such condition.
> 
> Reported-by: Yangtao Li <frank.li@...o.com>
> Signed-off-by: Yangtao Li <frank.li@...o.com>
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>  fs/f2fs/checkpoint.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 6c208108d69c..096c85022f62 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1639,8 +1639,10 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> 
>  	/* write cached NAT/SIT entries to NAT/SIT area */
>  	err = f2fs_flush_nat_entries(sbi, cpc);
> -	if (err)
> +	if (err) {
> +		f2fs_stop_checkpoint(sbi, false);

I think we should abuse this, since we can get any known ENOMEM as well.

>  		goto stop;
> +	}
> 
>  	f2fs_flush_sit_entries(sbi, cpc);
> 
> @@ -1648,10 +1650,12 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  	f2fs_save_inmem_curseg(sbi);
> 
>  	err = do_checkpoint(sbi, cpc);
> -	if (err)
> +	if (err) {
> +		f2fs_stop_checkpoint(sbi, false);
>  		f2fs_release_discard_addrs(sbi);
> -	else
> +	} else {
>  		f2fs_clear_prefree_segments(sbi, cpc);
> +	}
> 
>  	f2fs_restore_inmem_curseg(sbi);
>  stop:
> -- 
> 2.22.1