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Old 08-25-2010, 11:42 AM
Neil Brown
 
Default md: implment REQ_FLUSH/FUA support

On Wed, 25 Aug 2010 13:22:26 +0200
Tejun Heo <tj@kernel.org> wrote:

> This patch converts md to support REQ_FLUSH/FUA instead of now
> deprecated REQ_HARDBARRIER. In the core part (md.c), the following
> changes are notable.
>
> * Unlike REQ_HARDBARRIER, REQ_FLUSH/FUA don't interfere with
> processing of other requests and thus there is no reason to mark the
> queue congested while FLUSH/FUA is in progress.
>
> * REQ_FLUSH/FUA failures are final and its users don't need retry
> logic. Retry logic is removed.
>
> * Preflush needs to be issued to all member devices but FUA writes can
> be handled the same way as other writes - their processing can be
> deferred to request_queue of member devices. md_barrier_request()
> is renamed to md_flush_request() and simplified accordingly.
>
> For linear, raid0 and multipath, the core changes are enough. raid1,
> 5 and 10 need the following conversions.
>
> * raid1: Handling of FLUSH/FUA bio's can simply be deferred to
> request_queues of member devices. Barrier related logic removed.
>
> * raid5: Queue draining logic dropped. FUA bit is propagated through
> biodrain and stripe resconstruction such that all the updated parts
> of the stripe are written out with FUA writes if any of the dirtying
> writes was FUA. preread_active_stripes handling in make_request()
> is updated as suggested by Neil Brown.
>
> * raid10: FUA bit needs to be propagated to write clones.
>
> linear, raid0, 1, 5 and 10 tested.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Neil Brown <neilb@suse.de>
> ---
> Rebased on top of -rc2 and updated as suggested. Can you please
> review and ack it?

Reviewed-by: NeilBrown <neilb@suse.de>

Thanks!

NeilBrown

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