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Tue, 11 Aug 2020 00:20:08 -0400 X-MC-Unique: ykfP3vrVOFiOtdrP9xwSYw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 510B580BCAE; Tue, 11 Aug 2020 04:20:06 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 180E17B92F; Tue, 11 Aug 2020 04:20:00 +0000 (UTC) Date: Tue, 11 Aug 2020 00:20:00 -0400 From: Mike Snitzer To: Chao Leng Subject: Re: nvme: explicitly use normal NVMe error handling when appropriate Message-ID: <20200811042000.GA22692@redhat.com> References: <20200806184057.GA27858@redhat.com> <20200806191943.GA27868@redhat.com> <6B826235-C504-4621-B8F7-34475B200979@netapp.com> <20200807000755.GA28957@redhat.com> <510f5aff-0437-b1ce-f7ab-c812edbea880@grimberg.me> <20200807045015.GA29737@redhat.com> <20200810143620.GA19127@redhat.com> <20200810172209.GA19535@redhat.com> <7f99724a-a1eb-6bec-f8ae-f9a4601b0487@huawei.com> MIME-Version: 1.0 In-Reply-To: <7f99724a-a1eb-6bec-f8ae-f9a4601b0487@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=msnitzer@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200811_002014_340328_6BEED0CA X-CRM114-Status: GOOD ( 29.96 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sagi Grimberg , Hannes Reinecke , "linux-nvme@lists.infradead.org" , Christoph Hellwig , dm-devel@redhat.com, Ewan Milne , Keith Busch , "Meneghini, John" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Mon, Aug 10 2020 at 11:32pm -0400, Chao Leng wrote: > > > On 2020/8/11 1:22, Mike Snitzer wrote: > >On Mon, Aug 10 2020 at 10:36am -0400, > >Mike Snitzer wrote: > > > >>On Fri, Aug 07 2020 at 7:35pm -0400, > >>Sagi Grimberg wrote: > >> > >>> > >>>>>Hey Mike, > >... > >>>>I think NVMe can easily fix this by having an earlier stage of checking, > >>>>e.g. nvme_local_retry_req(), that shortcircuits ever getting to > >>>>higher-level multipathing consideration (be it native NVMe or DM > >>>>multipathing) for cases like NVME_SC_CMD_INTERRUPTED. > >>>>To be clear: the "default" case of nvme_failover_req() that returns > >>>>false to fallback to NVMe's "local" normal NVMe error handling -- that > >>>>can stay.. but a more explicit handling of cases like > >>>>NVME_SC_CMD_INTERRUPTED should be added to a nvme_local_retry_req() > >>>>check that happens before nvme_failover_req() in nvme_complete_rq(). > >>> > >>>I don't necessarily agree with having a dedicated nvme_local_retry_req(). > >>>a request that isn't failed over, goes to local error handling (retry or > >>>not). I actually think that just adding the condition to > >>>nvme_complete_req and having nvme_failover_req reject it would work. > >>> > >>>Keith? > >> > >>I think that is basically what I'm thinking too. > > > >From: Mike Snitzer > >Subject: nvme: explicitly use normal NVMe error handling when appropriate > > > >Commit 764e9332098c0 ("nvme-multipath: do not reset on unknown > >status"), among other things, fixed NVME_SC_CMD_INTERRUPTED error > >handling by changing multipathing's nvme_failover_req() to short-circuit > >path failover and then fallback to NVMe's normal error handling (which > >takes care of NVME_SC_CMD_INTERRUPTED). > > > >This detour through native NVMe multipathing code is unwelcome because > >it prevents NVMe core from handling NVME_SC_CMD_INTERRUPTED independent > >of any multipathing concerns. > > > >Introduce nvme_status_needs_local_error_handling() to prioritize > >non-failover retry, when appropriate, in terms of normal NVMe error > >handling. nvme_status_needs_local_error_handling() will naturely evolve > >to include handling of any other errors that normal error handling must > >be used for. > > > >nvme_failover_req()'s ability to fallback to normal NVMe error handling > >has been preserved because it may be useful for future NVME_SC that > >nvme_status_needs_local_error_handling() hasn't yet been trained for. > > > >Signed-off-by: Mike Snitzer > >--- > > drivers/nvme/host/core.c | 16 ++++++++++++++-- > > 1 file changed, 14 insertions(+), 2 deletions(-) > > > >diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > >index 88cff309d8e4..be749b690af7 100644 > >--- a/drivers/nvme/host/core.c > >+++ b/drivers/nvme/host/core.c > >@@ -252,6 +252,16 @@ static inline bool nvme_req_needs_retry(struct request *req) > > return true; > > } > >+static inline bool nvme_status_needs_local_error_handling(u16 status) > >+{ > >+ switch (status & 0x7ff) { > >+ case NVME_SC_CMD_INTERRUPTED: > >+ return true; > >+ default: > >+ return false; > >+ } > >+} > >+ > > static void nvme_retry_req(struct request *req) > > { > > struct nvme_ns *ns = req->q->queuedata; > >@@ -270,7 +280,8 @@ static void nvme_retry_req(struct request *req) > > void nvme_complete_rq(struct request *req) > > { > >- blk_status_t status = nvme_error_status(nvme_req(req)->status); > >+ u16 nvme_status = nvme_req(req)->status; > >+ blk_status_t status = nvme_error_status(nvme_status); > > trace_nvme_complete_rq(req); > >@@ -280,7 +291,8 @@ void nvme_complete_rq(struct request *req) > > nvme_req(req)->ctrl->comp_seen = true; > > if (unlikely(status != BLK_STS_OK && nvme_req_needs_retry(req))) { > >- if ((req->cmd_flags & REQ_NVME_MPATH) && nvme_failover_req(req)) > >+ if (!nvme_status_needs_local_error_handling(nvme_status) && > >+ (req->cmd_flags & REQ_NVME_MPATH) && nvme_failover_req(req)) > > This looks no affect. if work with nvme multipath, now is already retry local. Not if NVMe is built without multipathing configured. > If work with dm-multipath, still return error. Yes, I'm aware. Use of REQ_FAILFAST_TRANSPORT isn't something that is needed for NVMe, so why are you proposing hacks in NVMe to deal with it? > > return; > > if (!blk_queue_dying(req->q)) { > > > > Suggest: > REQ_FAILFAST_TRANSPORT may be designed for scsi, because scsi protocol > do not difine the local retry mechanism. SCSI implements a fuzzy local > retry mechanism, so need the REQ_FAILFAST_TRANSPORT for multipath > software, multipath software retry according error code is expected. > nvme is different with scsi about this. It define local retry mechanism > and path error code, so nvme should not care REQ_FAILFAST_TRANSPORT. Exactly. Except by "nvme should not care REQ_FAILFAST_TRANSPORT." your patch says you mean "nvme shouldn't disallow retry if REQ_FAILFAST_TRANSPORT is it". I'm saying: don't try to get such changes into NVMe. In general, aspects of your patch may have merit but overall it is doing too much. Mike _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme