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=-17.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 D4D89C433B4 for ; Fri, 16 Apr 2021 14:53:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A768561166 for ; Fri, 16 Apr 2021 14:53:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235877AbhDPOyP (ORCPT ); Fri, 16 Apr 2021 10:54:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:25537 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233916AbhDPOyP (ORCPT ); Fri, 16 Apr 2021 10:54:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618584830; 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=EpMX9YVvuW9vjoyNtTGCOLzykDR5ZQD680fLHRs3kog=; b=VkBW3uF+XaN7+/TQCJndy5R2v7rxIygCvUR5vKNIT4O1LZ8HjOj1ZqPWqO1jxw4uN8wun1 rQ6sLwCkof3P6/rT5sIcikL3gLXVQ26jDYWMWO18WqaA/0fI3I4djkLCVZCqZVCL4XYw+s +FetqkmbSbRTME+/R4pcfOqDnZIzKEc= 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-374-EFLytdQcMEa8zICGLZ5Wcw-1; Fri, 16 Apr 2021 10:53:45 -0400 X-MC-Unique: EFLytdQcMEa8zICGLZ5Wcw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CB3C1501E1; Fri, 16 Apr 2021 14:53:44 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 274AE5D9C0; Fri, 16 Apr 2021 14:53:41 +0000 (UTC) Date: Fri, 16 Apr 2021 10:53:40 -0400 From: Mike Snitzer To: Hannes Reinecke Cc: Christoph Hellwig , Jens Axboe , dm-devel@redhat.com, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, Chao Leng Subject: Re: [PATCH v2 2/4] nvme: allow local retry for requests with REQ_FAILFAST_TRANSPORT set Message-ID: <20210416145340.GB16047@redhat.com> References: <20210415231530.95464-1-snitzer@redhat.com> <20210415231530.95464-3-snitzer@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Apr 16 2021 at 10:01am -0400, Hannes Reinecke wrote: > On 4/16/21 1:15 AM, Mike Snitzer wrote: > > From: Chao Leng > > > > REQ_FAILFAST_TRANSPORT was designed for SCSI, because the SCSI protocol > > does not define the local retry mechanism. SCSI implements a fuzzy > > local retry mechanism, so REQ_FAILFAST_TRANSPORT is needed to allow > > higher-level multipathing software to perform failover/retry. > > > > NVMe is different with SCSI about this. It defines a local retry > > mechanism and path error codes, so NVMe should retry local for non > > path error. If path related error, whether to retry and how to retry > > is still determined by higher-level multipathing's failover. > > > > Unlike SCSI, NVMe shouldn't prevent retry if REQ_FAILFAST_TRANSPORT > > because NVMe's local retry is needed -- as is NVMe specific logic to > > categorize whether an error is path related. > > > > In this way, the mechanism of NVMe multipath or other multipath are > > now equivalent. The mechanism is: non path related error will be > > retried locally, path related error is handled by multipath. > > > > Signed-off-by: Chao Leng > > [snitzer: edited header for grammar and clarity, also added code comment] > > Signed-off-by: Mike Snitzer > > --- > > drivers/nvme/host/core.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 540d6fd8ffef..4134cf3c7e48 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -306,7 +306,14 @@ static inline enum nvme_disposition nvme_decide_disposition(struct request *req) > > if (likely(nvme_req(req)->status == 0)) > > return COMPLETE; > > > > - if (blk_noretry_request(req) || > > + /* > > + * REQ_FAILFAST_TRANSPORT is set by upper layer software that > > + * handles multipathing. Unlike SCSI, NVMe's error handling was > > + * specifically designed to handle local retry for non-path errors. > > + * As such, allow NVMe's local retry mechanism to be used for > > + * requests marked with REQ_FAILFAST_TRANSPORT. > > + */ > > + if ((req->cmd_flags & (REQ_FAILFAST_DEV | REQ_FAILFAST_DRIVER)) || > > (nvme_req(req)->status & NVME_SC_DNR) || > > nvme_req(req)->retries >= nvme_max_retries) > > return COMPLETE; > > > Huh? > > #define blk_noretry_request(rq) \ > ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \ > REQ_FAILFAST_DRIVER)) > > making the only _actual_ change in your patch _not_ evaluating the > REQ_FAILFAST_DRIVER, which incidentally is only used by the NVMe core. No, not sure how you got there. I'd have thought the 5 references to "REQ_FAILFAST_TRANSPORT" would've been sufficient ;) This patch makes it so requests marked with REQ_FAILFAST_TRANSPORT are allowed to use NVMe's local retry (that is required for non-transport errors). > So what is it you're trying to solve? What the patch header, code and code comment detail. Mike