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

[Chao Yu]

On 2021/8/25 1:09, Jaegeuk Kim wrote:
> 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

Oh, I doubt that we may failed to flush data of all inodes due to failures during
sync_inodes_sb(), additionally, how about adding retry logic for sync_inodes_sb()
if there is still any F2FS_DIRTY_DATA reference counts in f2fs_enable_checkpoint()
to mitigate this issue, e.g.:

f2fs_enable_checkpoint()

	do {
		sync_inode_sb();
		congestion_wait();
		cond_resched();
	} while (get_pages(sbi, F2FS_DIRTY_DATA) && retry_count--)

	if (get_pages(sbi, F2FS_DIRTY_DATA))
		f2fs_warm("");

Thanks,

> checkpoint=disable test. I don't think this hurts anything but can see
> some mitigation of the issue.
>
> > Thanks,