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

[Chao Yu]

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?

Thanks,