On Fri, 2013-08-16 at 18:41 +0200, Alexander Gordeev wrote:

On Thu, Aug 15, 2013 at 07:19:29PM -0700, Nicholas A. Bellinger wrote:

quoted

I'm playing with a patch to do this, but am currently getting hung-up on
what appear to be some separate blk-mq reserved_tags > 0 bugs, the first
of which is passing queue_depth=1 + reserved_tags=1 is broken, and
results in tags->nr_free = 0.

That is not a bug - please look at Jens replies in this thread some week ago.
In short, queue_depth=1 means 1 tags in total and reserved_tags=1 results
in zero normal tags. You need to request the depth=2 and reserved_tags=1.

Ahhh, yes of course.  I'll re-work a proposed patch this afternoon with
this in mind..

But yes, this is a separate topic and I am looking forward to hear from Jens
wrt flushes.

Indeed.  ;)

--nab