On Mon, Aug 23, 2010 at 04:13:36PM +0200, Tejun Heo wrote:

Yeah, that sounds reasonable.  blk_queue_flush() can be called anytime
without locking anyway, so it should be really easy to implement too.

I don't think we can simply call blk_queue_flush - we must ensure to
never set more bits than the device allows.  We'll just need two
sets of flags in the request queue, with the sysfs file checking that
it never allows more flags than blk_queue_flush.

I'll prepare a patch for this on top of the current series.