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=-13.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 84E8CC4338F for ; Mon, 2 Aug 2021 12:42:10 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 377EF60F36 for ; Mon, 2 Aug 2021 12:42:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 377EF60F36 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; 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auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.701, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "open list:Linux io_uring" , Stefan Hajnoczi , Julia Suvorova , qemu-devel@nongnu.org, Max Reitz , Stefan Hajnoczi , Aarushi Mehta , Stefano Garzarella Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 29.07.2021 um 11:10 hat Fabian Ebner geschrieben: > Linux SCSI can throw spurious -EAGAIN in some corner cases in its > completion path, which will end up being the result in the completed > io_uring request. > > Resubmitting such requests should allow block jobs to complete, even > if such spurious errors are encountered. > > Co-authored-by: Stefan Hajnoczi > Reviewed-by: Stefano Garzarella > Signed-off-by: Fabian Ebner > --- > > Changes from v1: > * Focus on what's relevant for the patch itself in the commit > message. > * Add Stefan's comment. > * Add Stefano's R-b tag (I hope that's fine, since there was no > change code-wise). > > block/io_uring.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/block/io_uring.c b/block/io_uring.c > index 00a3ee9fb8..dfa475cc87 100644 > --- a/block/io_uring.c > +++ b/block/io_uring.c > @@ -165,7 +165,21 @@ static void luring_process_completions(LuringState *s) > total_bytes = ret + luringcb->total_read; > > if (ret < 0) { > - if (ret == -EINTR) { > + /* > + * Only writev/readv/fsync requests on regular files or host block > + * devices are submitted. Therefore -EAGAIN is not expected but it's > + * known to happen sometimes with Linux SCSI. Submit again and hope > + * the request completes successfully. > + * > + * For more information, see: > + * https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u > + * > + * If the code is changed to submit other types of requests in the > + * future, then this workaround may need to be extended to deal with > + * genuine -EAGAIN results that should not be resubmitted > + * immediately. > + */ > + if (ret == -EINTR || ret == -EAGAIN) { > luring_resubmit(s, luringcb); > continue; > } Reviewed-by: Kevin Wolf Question about the preexisting code, though: luring_resubmit() requires that the caller calls ioq_submit() later so that the request doesn't just sit in a queue without getting any attention, but actually gets submitted to the kernel. In the call chain ioq_submit() -> luring_process_completions() -> luring_resubmit(), who takes care of that? Kevin