Re: [f2fs-dev] [PATCH 1/2] f2fs: use crc and cp version to determine roll-forward recovery

[Jaegeuk Kim]

On Tue, Sep 20, 2016 at 11:48:24PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2016/9/20 10:55, Jaegeuk Kim wrote:
> > Previously, we used cp_version only to detect recoverable dnodes.
> > In order to avoid same garbage cp_version, we needed to truncate the next
> > dnode during checkpoint, resulting in additional discard or data write.
> > If we can distinguish this by using crc in addition to cp_version, we can
> > remove this overhead.
> > 
> > There is backward compatibility concern where it changes node_footer layout.
> > But, it only affects the direct nodes written after the last checkpoint.
> > We simply expect that user would change kernel versions back and forth after
> > stable checkpoint.
> 
> With it, tests/generic/050 of fstest will fail:
> 
>      setting device read-only
>      mounting filesystem that needs recovery on a read-only device:
>      mount: SCRATCH_DEV is write-protected, mounting read-only
>     -mount: cannot mount SCRATCH_DEV read-only
>      unmounting read-only filesystem
>     -umount: SCRATCH_DEV: not mounted
>      mounting filesystem with -o norecovery on a read-only device:
> 
> Could you have a look at it?

Confirmed. There was a bug in the retrial path of fill_super().
I'm testing with this patch without any failure.

Thanks,