Re: [PATCH 1/1] block: rework flush sequencing for blk-mq

[Christoph Hellwig]

On Fri, Mar 14, 2014 at 10:30:53AM +0100, Hannes Reinecke wrote:
> That was actually one of my plans, move dm-multipath over to use
> blk-mq. But then I'd need to discuss with Jens et al how to best
> achieve this; the current static hctx allocation doesn't play well
> with multipaths dynamic path management.

I'd say it the other way around: the clone + insert hacks in
dm-multipath don't work well with blk-mq.  Not allowing non-owned
requests is fundamentally part of the blk-mq model to allow things
like the integrated tag allocator and queue depth limiting or the
preallocated driver specific data.

Instead dm-multipath should alway resubmit the request like it already
does for the slow path for the first step.  Longer term we might be able
to operate using a cheaper temporary structure, but I'm not sure that's
going to be worth it.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/