Re: dm-bufio

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Mar 23 2012 at 10:29am -0400,
Kasatkin, Dmitry <dmitry.kasatkin@intel.com> wrote:

> On Fri, Mar 23, 2012 at 4:21 PM, Mike Snitzer <snitzer@redhat.com> wrote:
> > On Fri, Mar 23 2012 at 10:12am -0400,
> > Kasatkin, Dmitry <dmitry.kasatkin@intel.com> wrote:
> >
> >> On Fri, Mar 23, 2012 at 1:26 PM, Kasatkin, Dmitry
> >> <dmitry.kasatkin@intel.com> wrote:
> >> > On Fri, Mar 23, 2012 at 1:10 PM, Zdenek Kabelac <zkabelac@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?