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,