Re: [PATCH 2/2] dmcache: Implement a flush message

[Peter Rajnoha <prajnoha@redhat.com>]

On 11.05.2013 17:25, Mike Snitzer wrote:> On Fri, May 10 2013 at  1:51pm
-0400,
> Darrick J. Wong <darrick.wong@oracle.com> wrote:
>
...
>> afaict, there isn't anything in the initscripts that tears down dm
devices
>> prior to invoking reboot(), and the kernel drivers don't have reboot
notifiers
>> to flush things out either.  I've been told that lvm does this, but I
don't see
>> anything in the Ubuntu or RHEL6 that would suggest a teardown script...
>
> See:
https://git.fedorahosted.org/cgit/lvm2.git/commit/?id=c698ee14bbb1310cf2383c8977d14a8e29139f8c
>
> But I'm not sure which distros have hooked blkdeactivate in (cc'ing
> prajnoha for his insight).
>

The blk-availability initscript/systemd unit that gets called at
shutdown/reboot and which in turn calls the blkdeactivate is already
used in RHEL 6.4 onwards and also in Fedora 18 onwards. However, for
Fedora, you need to enable the systemd unit explicitly at the moment
(systemctl enable blk-availability.service). To have it enabled by
default, the distro-wide default systemd configuration needs to be
edited which is controlled by systemd-preset file (I hope F19 is going
to have this enabled by default finally).

As for any other distros, it's up to the maintainers in that distro to
make use of the new script - I haven't looked if they started using it
or not. But upstream already provides it since lvm2 v2.02.98.

Peter