On 2016/9/30 8:53, Jaegeuk Kim wrote: > On Thu, Sep 29, 2016 at 08:01:32PM +0800, Chao Yu wrote: >> 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. >> >> Seems with new released v4.8 f2fs, old image with recoverable data could be >> mounted successfully, but meanwhile all fsynced data which needs to be recovered >> will be lost w/o any hints? >> >> Could we release a new version mkfs paired with new kernel module, so we can tag >> image as a new layout one, then new kernel module can recognize the image layout >> and adjust version suited comparing method with old or new image? > > Hmm, how about adding a checkpoint flag like CP_CRC_RECOVERY_FLAG? > Then, we can proceed crc|cp_ver, if the last checkpoint has this flag. > > Any thought? Ah, that's better. :) Thanks, > >> >> Thanks, >> >> > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
