[dm-devel] dm-bufio

[Kasatkin, Dmitry]

On Fri, Mar 23, 2012 at 4:32 PM, Mike Snitzer <snitzer at redhat.com> wrote:
> On Fri, Mar 23 2012 at 10:29am -0400,
> Kasatkin, Dmitry <dmitry.kasatkin at intel.com> wrote:
>
>> On Fri, Mar 23, 2012 at 4:21 PM, Mike Snitzer <snitzer at redhat.com> wrote:
>> > On Fri, Mar 23 2012 at 10:12am -0400,
>> > Kasatkin, Dmitry <dmitry.kasatkin at intel.com> wrote:
>> >
>> >> On Fri, Mar 23, 2012 at 1:26 PM, Kasatkin, Dmitry
>> >> <dmitry.kasatkin at intel.com> wrote:
>> >> > On Fri, Mar 23, 2012 at 1:10 PM, Zdenek Kabelac <zkabelac at redhat.com> wrote:
>> >> >> Dne 23.3.2012 12:01, Kasatkin, Dmitry napsal(a):
>> >> >>> Hello,
>> >> >>>
>> >> >>> When using dm-bufio and dm-io in general, how to ensure that all dirty
>> >> >>> buffers are written to the storage when machine reboots?
>> >> >>> suspend hooks could be used, but they are not called on reboot, only
>> >> >>> when suspending/removing the target...
>> >> >>>
>> >> >>
>> >> >> You mean you reboot without running  'sync' command?
>> >> >>
>> >> >> And yes - on reboot you should properly unmount devices - so you should
>> >> >> see removal of target on your shutdown sequence -  I believe Fedora currently
>> >> >> tries to support switch to some shutdown ramdisk, so all filesystem and
>> >> >> devices might be properly unmounted and destroyed.
>> >> >>
>> >> >
>> >> > Hello,
>> >> >
>> >> > Thanks for response.
>> >> > I use bufio to store some data on block device.
>> >> > It is not mounted in anyway. My target just use it to load/store data.
>> >> > When machine reboots, I want to be sure that bufio written all dirty buffers...
>> >> >
>> >> > - Dmitry
>> >> >
>> >>
>> >> At the moment, I have reboot notifier which does the following
>> >>
>> >>       dm_bufio_write_dirty_buffers(d->bufio);
>> >>       sync_blockdev(d->dev->bdev);
>> >>       blkdev_issue_flush(d->dev->bdev, GFP_KERNEL, NULL);
>> >>
>> >> without first line on the next boot I got corrupted/not updated blocks.
>> >> and I am not sure if I need last 2 lines...
>> >
>> > Are you cleanly removing the target from the kernel before reboot
>> > (e.g. dmsetup remove devname)?
>> >
>> > As long as your target's .dtr is making sure to flush all outstanding IO
>> > (like your reboot notifier does) you should be fine.
>> >
>>
>> The target contains rootfs... On reboot, it is remounted read-only.
>> I cannot remove it...
>>
>> Sometime ago I had "message" operation "sync", to sync backing devices.
>> But reboot notifier looks nice... It is automatically called.
>
> OK.
>
> As an aside, just curious: what does your target do?

I have experimented with integrity protection.

Thanks.