Gentle ping? This feature would be pretty useful if we want to really log heavy operations on a relatively small log devices. Thanks, Qu On 2019/6/19 下午4:03, Qu Wenruo wrote: > Current dm-log-writes will record all bios, no matter if the bios is > METADATA (normally what we care) or is DATA (normally we cares less for > the log-replay context). > > This causes a lot of extra space required for log device. E.g write 10M, > sync, overwrite that 10M file, this would cause over 20M for log device > just for the data. > > This patchset introduces two way to specify the dump type: > - dump_type=%s optional option for constructor > The default dump_type is ALL, thus no behavior change. > > - dump_type=%s message type to change type on the fly > > Also to cooperate the new dump_type= option, always output the dump_type > for STATUSTYPE_TABLE. > > A common use case would be: > # dmsetup create log --table 0 $(blockdev --getsz $dev) log-writes $dev $log_dev > # mkfs.btrfs -f /dev/mapper/log > # dmsetup suspend log > # dmsetup message log 0 dump_type=METADATA|FUA|FLUSH|DISCARD|MARK > # dmsetup resume log > # mount /dev/mapper/log <mnt> > # <do some work load> > # umount <mnt> > # dmsetup remove log > # <replay> > > Now the log device will not record data writes, thus hugely reduce the > space requirement for log device, allowing more operations to be down > before hitting the space limit. > > Currently btrfs check doesn't check data checksum by default, thus even > we have wrong data on-disk, we should be fine checking the metadata. > > I'm not 100% sure if this applies to other filesystems, but as long as > metadata writes is marked correctly, other filesystems can also benifit > from this feature. > > Qu Wenruo (2): > dm log writes: Allow dm-log-writes to filter bios based on types to > reduce log device space usage > dm log writes: Introduce dump_type= message type to change dump_type > on the fly > > drivers/md/dm-log-writes.c | 177 ++++++++++++++++++++++++++++++++++--- > 1 file changed, 167 insertions(+), 10 deletions(-) >
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