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Wed, 4 Mar 2026 21:37:20 -0500 Received: (from bmarzins@localhost) by bmarzins-01.fast.eng.rdu2.dc.redhat.com (8.18.1/8.18.1/Submit) id 6252bIIF1952897; Wed, 4 Mar 2026 21:37:18 -0500 Date: Wed, 4 Mar 2026 21:37:18 -0500 From: Benjamin Marzinski To: John Garry Cc: hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@fb.com, martin.petersen@oracle.com, james.bottomley@hansenpartnership.com, hare@suse.com, jmeneghi@redhat.com, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, michael.christie@oracle.com, snitzer@kernel.org, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/24] scsi-multipath: add scsi_mpath_{start,end}_request() Message-ID: References: <20260225153627.1032500-1-john.g.garry@oracle.com> <20260225153627.1032500-11-john.g.garry@oracle.com> <93752514-3225-4cdf-b9a5-e0964d693b5b@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <93752514-3225-4cdf-b9a5-e0964d693b5b@oracle.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On Wed, Mar 04, 2026 at 11:11:08AM +0000, John Garry wrote: > On 04/03/2026 06:13, Benjamin Marzinski wrote: > > > + scsi_mpath_end_request(req); > > > + > > > /* > > > * In the MQ case the command gets freed by __blk_mq_end_request, > > > * so we have to do all cleanup that depends on it earlier. > > This looks wrong. We start accounting in scsi_queue_rq(), and we need to > > end it whenever we complete or requeue the request, otherwise the > > accounting will get off. But not all requests go through > > scsi_end_request(). scsi_mpath_failover_req(), for instance, calls > > blk_mq_end_request() directly, and other functions, like > > scsi_queue_insert() call blk_mq_requeue_request(). I'm pretty sure that > > this should go in scsi_complete(), as well in the error path of > > scsi_queue_rq(). > > ok, let me check that further. > I think I was a little hasty here. Looking at sd_mpath_start_command() and sd_mpath_end_command() in patch 17, I can see that they protect against repeat calls, so requeueing the request should be o.k. There's still a problem when scsi_mpath_failover_req() calls blk_mq_end_request() directly, and when scsi_queue_rq() exits with a failure where the request won't requeued (all the returns except BLK_STS_OK, BLK_STS_RESOURCE, and BLK_STS_DEV_RESOURCE). -Ben > Thanks for the notice.