linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: don't ignore writing pages on fsync during checkpoint=disable

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Date:   Tue, 24 Aug 2021 10:09:42 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: don't ignore writing pages on fsync
 during checkpoint=disable

On 08/24, Chao Yu wrote:
> On 2021/8/24 1:01, Jaegeuk Kim wrote:
> > We must flush dirty pages when calling fsync() during checkpoint=disable.
> > Returning zero makes inode being clear, which fails to flush them when
> > enabling checkpoint back even by sync_inodes_sb().
> 
> Without this patch, file can be persisted via checkpoint=enable as well, my
> testcase:
> 
> - mount -t f2fs -o checkpoint=disable,checkpoint_nomerge /dev/pmem0 /mnt/f2fs/
> - cp file /mnt/f2fs/
> - xfs_io /mnt/f2fs/file -c "fdatasync"
> - mount -o remount,checkpoint=enable /dev/pmem0 /mnt/f2fs/
> - umount /mnt/f2fs
> - mount /dev/pmem0 /mnt/f2fs
> - md5sum file /mnt/f2fs/file
> chksum values are the same.
> 
> Am I missing something?

I'm trying to address one subtle issue where a file has only NEW_ADDR by the
checkpoint=disable test. I don't think this hurts anything but can see
some mitigation of the issue.

> 
> Thanks,