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SubjectRe: [PATCH 23/41] dm: implement REQ_FLUSH/FUA support for bio-based dm
On Fri, Sep 03 2010 at  6:29am -0400,
Tejun Heo <tj@kernel.org> wrote:

> This patch converts bio-based dm to support REQ_FLUSH/FUA instead of
> now deprecated REQ_HARDBARRIER.
>
> * -EOPNOTSUPP handling logic dropped.
>
> * Preflush is handled as before but postflush is dropped and replaced
> with passing down REQ_FUA to member request_queues. This replaces
> one array wide cache flush w/ member specific FUA writes.
>
> * __split_and_process_bio() now calls __clone_and_map_flush() directly
> for flushes and guarantees all FLUSH bio's going to targets are zero
> ` length.
>
> * It's now guaranteed that all FLUSH bio's which are passed onto dm
> targets are zero length. bio_empty_barrier() tests are replaced
> with REQ_FLUSH tests.
>
> * Empty WRITE_BARRIERs are replaced with WRITE_FLUSHes.
>
> * Dropped unlikely() around REQ_FLUSH tests. Flushes are not unlikely
> enough to be marked with unlikely().
>
> * Block layer now filters out REQ_FLUSH/FUA bio's if the request_queue
> doesn't support cache flushing. Advertise REQ_FLUSH | REQ_FUA
> capability.
>
> * Request based dm isn't converted yet. dm_init_request_based_queue()
> resets flush support to 0 for now. To avoid disturbing request
> based dm code, dm->flush_error is added for bio based dm while
> requested based dm continues to use dm->barrier_error.
>
> Lightly tested linear, stripe, raid1, snap and crypt targets. Please
> proceed with caution as I'm not familiar with the code base.

Reviewed-by: Mike Snitzer <snitzer@redhat.com>

Mikulas and/or Alasdair won't be able to review this until next week.


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