From mboxrd@z Thu Jan  1 00:00:00 1970
From: keith.busch@intel.com (Keith Busch)
Date: Tue, 9 Jan 2018 10:38:58 -0700
Subject: [PATCH 2/5] nvme/multipath: Consult blk_status_t for failover
In-Reply-To: <20180108095707.GD4673@lst.de>
References: <20180104224623.8944-1-keith.busch@intel.com>
 <20180104224623.8944-3-keith.busch@intel.com>
 <20180108095707.GD4673@lst.de>
Message-ID: <20180109173857.GF15154@localhost.localdomain>

On Mon, Jan 08, 2018@01:57:07AM -0800, Christoph Hellwig wrote:
> > -	if (unlikely(nvme_req(req)->status && nvme_req_needs_retry(req))) {
> > -		if (nvme_req_needs_failover(req)) {
> > +	blk_status_t status = nvme_error_status(req);
> > +
> > +	if (unlikely(status != BLK_STS_OK && nvme_req_needs_retry(req))) {
> > +		if (nvme_req_needs_failover(req, status)) {
> 
> We don't really need to call nvme_error_status if nvme_req(req)->status
> is zero.

We are already calling nvme_error_status unconditionally for
blk_mq_end_request, so we currently read nvme_req(req)->status multiple
times in the completion path. I think we'd prefer to read it just once.