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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 5CFB5C433B4 for ; Fri, 16 Apr 2021 14:01:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 348926117A for ; Fri, 16 Apr 2021 14:01:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235796AbhDPOB1 (ORCPT ); Fri, 16 Apr 2021 10:01:27 -0400 Received: from mx2.suse.de ([195.135.220.15]:52300 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235196AbhDPOB0 (ORCPT ); Fri, 16 Apr 2021 10:01:26 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0484EB12D; Fri, 16 Apr 2021 14:01:01 +0000 (UTC) To: Mike Snitzer , Christoph Hellwig , Jens Axboe Cc: dm-devel@redhat.com, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, Chao Leng References: <20210415231530.95464-1-snitzer@redhat.com> <20210415231530.95464-3-snitzer@redhat.com> From: Hannes Reinecke Organization: SUSE Linux GmbH Subject: Re: [PATCH v2 2/4] nvme: allow local retry for requests with REQ_FAILFAST_TRANSPORT set Message-ID: Date: Fri, 16 Apr 2021 16:01:00 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210415231530.95464-3-snitzer@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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. So what is it you're trying to solve? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, 90409 Nürnberg GF: F. Imendörffer, HRB 36809 (AG Nürnberg) 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=-15.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 D14F5C433ED for ; Fri, 16 Apr 2021 14:01:28 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 35E1360FEE for ; Fri, 16 Apr 2021 14:01:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 35E1360FEE Authentication-Results: mail.kernel.org; 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charset="utf-8" Content-Transfer-Encoding: base64 Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org T24gNC8xNi8yMSAxOjE1IEFNLCBNaWtlIFNuaXR6ZXIgd3JvdGU6Cj4gRnJvbTogQ2hhbyBMZW5n IDxsZW5nY2hhb0BodWF3ZWkuY29tPgo+IAo+IFJFUV9GQUlMRkFTVF9UUkFOU1BPUlQgd2FzIGRl c2lnbmVkIGZvciBTQ1NJLCBiZWNhdXNlIHRoZSBTQ1NJIHByb3RvY29sCj4gZG9lcyBub3QgZGVm aW5lIHRoZSBsb2NhbCByZXRyeSBtZWNoYW5pc20uIFNDU0kgaW1wbGVtZW50cyBhIGZ1enp5Cj4g bG9jYWwgcmV0cnkgbWVjaGFuaXNtLCBzbyBSRVFfRkFJTEZBU1RfVFJBTlNQT1JUIGlzIG5lZWRl ZCB0byBhbGxvdwo+IGhpZ2hlci1sZXZlbCBtdWx0aXBhdGhpbmcgc29mdHdhcmUgdG8gcGVyZm9y bSBmYWlsb3Zlci9yZXRyeS4KPiAKPiBOVk1lIGlzIGRpZmZlcmVudCB3aXRoIFNDU0kgYWJvdXQg dGhpcy4gSXQgZGVmaW5lcyBhIGxvY2FsIHJldHJ5Cj4gbWVjaGFuaXNtIGFuZCBwYXRoIGVycm9y IGNvZGVzLCBzbyBOVk1lIHNob3VsZCByZXRyeSBsb2NhbCBmb3Igbm9uCj4gcGF0aCBlcnJvci4g SWYgcGF0aCByZWxhdGVkIGVycm9yLCB3aGV0aGVyIHRvIHJldHJ5IGFuZCBob3cgdG8gcmV0cnkK PiBpcyBzdGlsbCBkZXRlcm1pbmVkIGJ5IGhpZ2hlci1sZXZlbCBtdWx0aXBhdGhpbmcncyBmYWls b3Zlci4KPiAKPiBVbmxpa2UgU0NTSSwgTlZNZSBzaG91bGRuJ3QgcHJldmVudCByZXRyeSBpZiBS RVFfRkFJTEZBU1RfVFJBTlNQT1JUCj4gYmVjYXVzZSBOVk1lJ3MgbG9jYWwgcmV0cnkgaXMgbmVl ZGVkIC0tIGFzIGlzIE5WTWUgc3BlY2lmaWMgbG9naWMgdG8KPiBjYXRlZ29yaXplIHdoZXRoZXIg YW4gZXJyb3IgaXMgcGF0aCByZWxhdGVkLgo+IAo+IEluIHRoaXMgd2F5LCB0aGUgbWVjaGFuaXNt IG9mIE5WTWUgbXVsdGlwYXRoIG9yIG90aGVyIG11bHRpcGF0aCBhcmUKPiBub3cgZXF1aXZhbGVu dC4gVGhlIG1lY2hhbmlzbSBpczogbm9uIHBhdGggcmVsYXRlZCBlcnJvciB3aWxsIGJlCj4gcmV0 cmllZCBsb2NhbGx5LCBwYXRoIHJlbGF0ZWQgZXJyb3IgaXMgaGFuZGxlZCBieSBtdWx0aXBhdGgu Cj4gCj4gU2lnbmVkLW9mZi1ieTogQ2hhbyBMZW5nIDxsZW5nY2hhb0BodWF3ZWkuY29tPgo+IFtz bml0emVyOiBlZGl0ZWQgaGVhZGVyIGZvciBncmFtbWFyIGFuZCBjbGFyaXR5LCBhbHNvIGFkZGVk IGNvZGUgY29tbWVudF0KPiBTaWduZWQtb2ZmLWJ5OiBNaWtlIFNuaXR6ZXIgPHNuaXR6ZXJAcmVk aGF0LmNvbT4KPiAtLS0KPiAgZHJpdmVycy9udm1lL2hvc3QvY29yZS5jIHwgOSArKysrKysrKy0K PiAgMSBmaWxlIGNoYW5nZWQsIDggaW5zZXJ0aW9ucygrKSwgMSBkZWxldGlvbigtKQo+IAo+IGRp ZmYgLS1naXQgYS9kcml2ZXJzL252bWUvaG9zdC9jb3JlLmMgYi9kcml2ZXJzL252bWUvaG9zdC9j b3JlLmMKPiBpbmRleCA1NDBkNmZkOGZmZWYuLjQxMzRjZjNjN2U0OCAxMDA2NDQKPiAtLS0gYS9k cml2ZXJzL252bWUvaG9zdC9jb3JlLmMKPiArKysgYi9kcml2ZXJzL252bWUvaG9zdC9jb3JlLmMK PiBAQCAtMzA2LDcgKzMwNiwxNCBAQCBzdGF0aWMgaW5saW5lIGVudW0gbnZtZV9kaXNwb3NpdGlv biBudm1lX2RlY2lkZV9kaXNwb3NpdGlvbihzdHJ1Y3QgcmVxdWVzdCAqcmVxKQo+ICAJaWYgKGxp a2VseShudm1lX3JlcShyZXEpLT5zdGF0dXMgPT0gMCkpCj4gIAkJcmV0dXJuIENPTVBMRVRFOwo+ ICAKPiAtCWlmIChibGtfbm9yZXRyeV9yZXF1ZXN0KHJlcSkgfHwKPiArCS8qCj4gKwkgKiBSRVFf RkFJTEZBU1RfVFJBTlNQT1JUIGlzIHNldCBieSB1cHBlciBsYXllciBzb2Z0d2FyZSB0aGF0Cj4g KwkgKiBoYW5kbGVzIG11bHRpcGF0aGluZy4gVW5saWtlIFNDU0ksIE5WTWUncyBlcnJvciBoYW5k bGluZyB3YXMKPiArCSAqIHNwZWNpZmljYWxseSBkZXNpZ25lZCB0byBoYW5kbGUgbG9jYWwgcmV0 cnkgZm9yIG5vbi1wYXRoIGVycm9ycy4KPiArCSAqIEFzIHN1Y2gsIGFsbG93IE5WTWUncyBsb2Nh bCByZXRyeSBtZWNoYW5pc20gdG8gYmUgdXNlZCBmb3IKPiArCSAqIHJlcXVlc3RzIG1hcmtlZCB3 aXRoIFJFUV9GQUlMRkFTVF9UUkFOU1BPUlQuCj4gKwkgKi8KPiArCWlmICgocmVxLT5jbWRfZmxh Z3MgJiAoUkVRX0ZBSUxGQVNUX0RFViB8IFJFUV9GQUlMRkFTVF9EUklWRVIpKSB8fAo+ICAJICAg IChudm1lX3JlcShyZXEpLT5zdGF0dXMgJiBOVk1FX1NDX0ROUikgfHwKPiAgCSAgICBudm1lX3Jl cShyZXEpLT5yZXRyaWVzID49IG52bWVfbWF4X3JldHJpZXMpCj4gIAkJcmV0dXJuIENPTVBMRVRF Owo+IApIdWg/CgojZGVmaW5lIGJsa19ub3JldHJ5X3JlcXVlc3QocnEpIFwKICAgICAgICAoKHJx KS0+Y21kX2ZsYWdzICYgKFJFUV9GQUlMRkFTVF9ERVZ8UkVRX0ZBSUxGQVNUX1RSQU5TUE9SVHwg XAogICAgICAgICAgICAgICAgICAgICAgICAgICAgIFJFUV9GQUlMRkFTVF9EUklWRVIpKQoKbWFr aW5nIHRoZSBvbmx5IF9hY3R1YWxfIGNoYW5nZSBpbiB5b3VyIHBhdGNoIF9ub3RfIGV2YWx1YXRp bmcgdGhlClJFUV9GQUlMRkFTVF9EUklWRVIsIHdoaWNoIGluY2lkZW50YWxseSBpcyBvbmx5IHVz ZWQgYnkgdGhlIE5WTWUgY29yZS4KU28gd2hhdCBpcyBpdCB5b3UncmUgdHJ5aW5nIHRvIHNvbHZl PwoKQ2hlZXJzLAoKSGFubmVzCi0tIApEci4gSGFubmVzIFJlaW5lY2tlCQkgICAgICAgIEtlcm5l bCBTdG9yYWdlIEFyY2hpdGVjdApoYXJlQHN1c2UuZGUJCQkgICAgICAgICAgICAgICArNDkgOTEx IDc0MDUzIDY4OApTVVNFIFNvZnR3YXJlIFNvbHV0aW9ucyBHZXJtYW55IEdtYkgsIDkwNDA5IE7D vHJuYmVyZwpHRjogRi4gSW1lbmTDtnJmZmVyLCBIUkIgMzY4MDkgKEFHIE7DvHJuYmVyZykKCl9f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCkxpbnV4LW52bWUg bWFpbGluZyBsaXN0CkxpbnV4LW52bWVAbGlzdHMuaW5mcmFkZWFkLm9yZwpodHRwOi8vbGlzdHMu aW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LW52bWUK 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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 085F0C433B4 for ; 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