From patchwork Thu Jul 29 09:10:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fiona Ebner X-Patchwork-Id: 1511135 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) 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 ozlabs.org (Postfix) with ESMTPS id 4Gb4YX01Qfz9sV8 for ; Thu, 29 Jul 2021 19:12:30 +1000 (AEST) Received: from localhost ([::1]:36302 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m925b-0007KF-5R for incoming@patchwork.ozlabs.org; Thu, 29 Jul 2021 05:12:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40628) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m925I-0007K1-Tg; Thu, 29 Jul 2021 05:12:08 -0400 Received: from proxmox-new.maurer-it.com ([94.136.29.106]:46290) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m925G-0006yT-N5; Thu, 29 Jul 2021 05:12:08 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id E24EF42C48; Thu, 29 Jul 2021 11:12:01 +0200 (CEST) From: Fabian Ebner To: qemu-devel@nongnu.org Subject: [PATCH v2] block/io_uring: resubmit when result is -EAGAIN Date: Thu, 29 Jul 2021 11:10:29 +0200 Message-Id: <20210729091029.65369-1-f.ebner@proxmox.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Received-SPF: pass client-ip=94.136.29.106; envelope-from=f.ebner@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: Kevin Wolf , "open list:Linux io_uring" , Stefan Hajnoczi , Julia Suvorova , Max Reitz , Stefan Hajnoczi , Fabian Ebner , Aarushi Mehta , Stefano Garzarella Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" 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 Reviewed-by: Kevin Wolf --- 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; }