Hello,

On 08/16/2010 08:33 PM, Christoph Hellwig wrote:

On Mon, Aug 16, 2010 at 06:52:00PM +0200, Tejun Heo wrote:

quoted

From: Tejun Heo <redacted>

Remove now unused REQ_HARDBARRIER support and implement REQ_FLUSH/FUA
support instead.  A new feature flag VIRTIO_BLK_F_FUA is added to
indicate the support for FUA.

I'm not sure it's worth it.  The pure REQ_FLUSH path works not and is
well tested with kvm/qemu.   We can still easily add a FUA bit, and
even a pre-flush bit if the protocol roundtrips matter in real life
benchmarking.

Hmmm... the underlying storage could be md/dm RAIDs in which case FUA
should be cheaper than FLUSH.

Thanks.

-- 
tejun