[dm-devel] [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm
Mikulas Patocka
mpatocka at redhat.com
Wed Sep 1 10:31:53 UTC 2010
On Mon, 30 Aug 2010, Mike Snitzer wrote:
> Hi,
>
> On Mon, Aug 30 2010 at 11:45am -0400,
> Tejun Heo <tj at kernel.org> wrote:
>
> > Here's a version w/ BUG_ON() added. Once the queue hang issue is
> > tracked down, I'll refresh the whole series and repost.
>
> When you next send out the refreshed series, could you cc dm-devel any
> patches that touch DM directly or block patches that are required to
> support DM?
>
> It'd be great to cc Mikulas Patocka on those patches too (I cc'd him).
> Mikulas will be reviewing these DM patches now that we have something
> that works with your larger FLUSH+FUA patchset.
>
> Thanks,
> Mike
My recommended approach to this (on non-request-based dm) is to simply let
the current barrier infrastructure be as it is --- you don't need to
change it now, you can simply map FUA write to barrier write and FLUSH to
zero-data barrier --- and it won't cause any data corruption. It will just
force unneeded I/O queue draining.
Once FLUSH+FUA interface is finalized and committed upstream, we can
remove that I/O queue draining from dm to improve performance.
Mikulas
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