From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01985C433DF for ; Tue, 11 Aug 2020 14:12:31 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C6D5520782 for ; Tue, 11 Aug 2020 14:12:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="c9hnInyh"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="caEVSzpC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C6D5520782 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZbdxOAPSDoV3UhLm1O0F8hMCD3yOAmskhCQISikAQXM=; b=c9hnInyhFa2E/R8eJx2Umdbvt tonKP4UcIIAkhxs6U3vqUpYfx9WSFgQdYWrgKRfw+yDg2k+T1SS9xCdDVvFdOIFkwn1YK8q8OWExs xB1xslXseaHMnCu+3KsXsu0lZbq1xjX0hClKUG2PWoI4yqbhxq7426Vt4wEtuzQbLIp4FjwzwuoiH /KQE9XJbBi22IO+A+UGCbP2hLBxG8Sz/TYfTGvNPaK4NJziPH/U00fZpRQV1WPonBYOhZG3PpdEtq GrgyJJSgkmwUs+LzHZWRfvwblr66sb1NCD+fh9TQhTmuzYVP3B7NsP0VnrKWvfk/GAsXXjAVYO2tn slgb1pmaQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k5V0q-0006Ap-NM; Tue, 11 Aug 2020 14:12:24 +0000 Received: from us-smtp-2.mimecast.com ([205.139.110.61] helo=us-smtp-delivery-1.mimecast.com) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k5V0m-0006A4-8v for linux-nvme@lists.infradead.org; Tue, 11 Aug 2020 14:12:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597155139; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZZbm9u1gzdVJdyrfRJlLMurWLWySxfYh3fgyx2JBxss=; b=caEVSzpCGxehsBajAPQ7jG3LaedlMAEhqe76OzZI3GzgpwW0nEXahb4ozJN8Krm4DLyg+l 4+hP2UuDczbcl5YPoBT0xnju6/SyGIpcjUm/I5vNh/jSRpZHG8nrvLhMf+uzBoMIL9FYgY EiHDzJ8TWS2B+TGC8GXfttwWOBei7Ps= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-290-5Qh6pdVJNYmwWBEjO7rcRA-1; Tue, 11 Aug 2020 10:12:17 -0400 X-MC-Unique: 5Qh6pdVJNYmwWBEjO7rcRA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 61B911853DB4; Tue, 11 Aug 2020 14:12:16 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7447B65C6F; Tue, 11 Aug 2020 14:12:10 +0000 (UTC) Date: Tue, 11 Aug 2020 10:12:09 -0400 From: Mike Snitzer To: Chao Leng Subject: Re: nvme: explicitly use normal NVMe error handling when appropriate Message-ID: <20200811141209.GA25261@redhat.com> References: <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> <20200811042000.GA22692@redhat.com> <07bd0219-b39b-dcec-35f0-edc22df0d2ae@huawei.com> MIME-Version: 1.0 In-Reply-To: <07bd0219-b39b-dcec-35f0-edc22df0d2ae@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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_101220_414361_CC299D1B X-CRM114-Status: GOOD ( 32.62 ) 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 Tue, Aug 11 2020 at 2:17am -0400, Chao Leng wrote: > > > On 2020/8/11 12:20, Mike Snitzer wrote: > >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 without nvme multipathing configured, now is also retry local, do not need > !nvme_status_needs_local_error_handling(nvme_status). True, REQ_NVME_MPATH won't be set, so it'll fall through. The real benefit of my patch is that there is a cleaner code flow for handling errors with normal NVMe retry (without bouncing into failover code and then falling back to normal retry -- code that your patch does remove). SO my change is an obvious yet small improvement that makes the NVMe core error handling clearer -- yet preserves that fallback from failover_retry to help future-proof NVMe from new NVME_SC: which John M. is very clear about needing. > >>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? > I just describe the possible scenarios:1.nvme multipathing configured. > 2.without any multipath.3. with dm-multipath. I understand. > > > >>> 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. > > no. the patch just mean: if path error, fail over to retry by multipath > (nvme multipath or dm-multipath). Other need local retry local, retry > after a defined time according to status(CRD) and CRDT. Now nvme multipath > is already do like this, the patch make dm-multipath work like nvme multipath. I appreciate your enthusiasm for making native NVMe multipathing and dm-multipath coexist. But I think you're naive about the willingness to make that a reality. As such, any change that only benefits dm-multipath is dead on arrival. Your patch is mixed with various changes like that. I'd be stunned if Christoph accepted it. Thanks, Mike _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme