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? > > 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
