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

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Message-ID: <5f37995c-2390-e8ca-d002-3639ad39e0d3@kernel.org>
Date:   Mon, 19 Jul 2021 16:54:40 +0800
From:   Chao Yu <chao@...nel.org>
To:     Yangtao Li <frank.li@...o.com>, jaegeuk@...nel.org
Cc:     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 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);
  		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