From patchwork Mon Jul 15 20:19:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 11044953 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 50D9E14F6 for ; Mon, 15 Jul 2019 20:20:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 41716205A8 for ; Mon, 15 Jul 2019 20:20:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 35573262FF; Mon, 15 Jul 2019 20:20:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BA5C8205A8 for ; Mon, 15 Jul 2019 20:20:43 +0000 (UTC) Received: from localhost ([::1]:42628 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hn7Sk-0007RQ-Tg for patchwork-qemu-devel@patchwork.kernel.org; Mon, 15 Jul 2019 16:20:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55317) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hn7SK-0005Wa-Sf for qemu-devel@nongnu.org; Mon, 15 Jul 2019 16:20:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hn7SJ-0007ax-GW for qemu-devel@nongnu.org; Mon, 15 Jul 2019 16:20:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51678) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hn7SG-0007Xn-Sk; Mon, 15 Jul 2019 16:20:13 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D39EB85360; Mon, 15 Jul 2019 20:20:10 +0000 (UTC) Received: from localhost (ovpn-117-120.ams2.redhat.com [10.36.117.120]) by smtp.corp.redhat.com (Postfix) with ESMTP id CDCE819C59; Mon, 15 Jul 2019 20:20:04 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Date: Mon, 15 Jul 2019 21:19:49 +0100 Message-Id: <20190715201950.9444-3-stefanha@redhat.com> In-Reply-To: <20190715201950.9444-1-stefanha@redhat.com> References: <20190715201950.9444-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Mon, 15 Jul 2019 20:20:10 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 2/3] block/io_uring: fix EINTR request resubmission 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 , qemu-block@nongnu.org, Max Reitz , Stefan Hajnoczi , Stefan Hajnoczi , Julia Suvorova , Aarushi Mehta Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Adding the request to sq_overflow isn't enough: 1. luringcb->sqeq is uninitialized if there was space in the sq ring at submission time. 2. Not all code paths invoke ioq_submit() after processing completions, so the request could hang. Additional bugs include checking for EINTR instead of -EINTR and forgetting to skip the completion callback when a request is resubmitted. Fix this by always initializing luringcb->sqeq and ensuring that all code paths invoke ioq_submit() after appending to sq_overflow. Ensure that luring_process_completions() marks the cqe seen and decrements in_flight before resubmitting the request. Signed-off-by: Stefan Hajnoczi --- block/io_uring.c | 64 ++++++++++++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 27 deletions(-) diff --git a/block/io_uring.c b/block/io_uring.c index 19919da4c9..97e4f876d7 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -87,6 +87,18 @@ int luring_register_fd(LuringState *s, unsigned int fd) s->fd.head, s->fd.size); } +/** + * luring_resubmit: + * + * Resubmit a request by appending it to sq_overflow. The caller must ensure + * that ioq_submit() is called later so that sq_overflow requests are started. + */ +static void luring_resubmit(LuringState *s, LuringAIOCB *luringcb) +{ + QSIMPLEQ_INSERT_TAIL(&s->io_q.sq_overflow, luringcb, next); + s->io_q.in_queue++; +} + /** * luring_process_completions: * @s: AIO state @@ -102,7 +114,6 @@ int luring_register_fd(LuringState *s, unsigned int fd) static void luring_process_completions(LuringState *s) { struct io_uring_cqe *cqes; - int ret; /* * Request completion callbacks can run the nested event loop. @@ -122,11 +133,20 @@ static void luring_process_completions(LuringState *s) qemu_bh_schedule(s->completion_bh); while (io_uring_peek_cqe(&s->ring, &cqes) == 0) { + LuringAIOCB *luringcb; + int ret; + if (!cqes) { break; } - LuringAIOCB *luringcb = io_uring_cqe_get_data(cqes); + + luringcb = io_uring_cqe_get_data(cqes); ret = cqes->res; + io_uring_cqe_seen(&s->ring, cqes); + cqes = NULL; + + /* Change counters one-by-one because we can be nested. */ + s->io_q.in_flight--; trace_luring_process_completion(s, luringcb, ret); @@ -143,17 +163,12 @@ static void luring_process_completions(LuringState *s) ret = -ENOSPC;; } /* Add to overflow queue to be resubmitted later */ - } else if (ret == EINTR) { - QSIMPLEQ_INSERT_TAIL(&s->io_q.sq_overflow, luringcb, next); + } else if (ret == -EINTR) { + luring_resubmit(s, luringcb); + continue; } luringcb->ret = ret; - - io_uring_cqe_seen(&s->ring, cqes); - cqes = NULL; - /* Change counters one-by-one because we can be nested. */ - s->io_q.in_flight--; - /* * If the coroutine is already entered it must be in ioq_submit() * and will notice luringcb->ret has been filled in when it @@ -245,16 +260,16 @@ static int ioq_submit(LuringState *s) } s->io_q.in_flight += ret; s->io_q.in_queue -= ret; + + if (s->io_q.in_flight) { + /* + * We can try to complete something just right away if there are + * still requests in-flight. + */ + luring_process_completions(s); + } } s->io_q.blocked = (s->io_q.in_queue > 0); - - if (s->io_q.in_flight) { - /* - * We can try to complete something just right away if there are - * still requests in-flight. - */ - luring_process_completions(s); - } return ret; } @@ -290,15 +305,7 @@ static int luring_do_submit(int fd, LuringAIOCB *luringcb, LuringState *s, uint64_t offset, int type) { int ret; - struct io_uring_sqe *sqes = io_uring_get_sqe(&s->ring); - /* - *If the ring is full and cannot fetch new sqes, add the request to - * to an overflow queue to be submitted later - */ - if (!sqes) { - sqes = &luringcb->sqeq; - QSIMPLEQ_INSERT_TAIL(&s->io_q.sq_overflow, luringcb, next); - } + struct io_uring_sqe *sqes = &luringcb->sqeq; switch (type) { case QEMU_AIO_WRITE: @@ -318,7 +325,10 @@ static int luring_do_submit(int fd, LuringAIOCB *luringcb, LuringState *s, abort(); } io_uring_sqe_set_data(sqes, luringcb); + + QSIMPLEQ_INSERT_TAIL(&s->io_q.sq_overflow, luringcb, next); s->io_q.in_queue++; + trace_luring_do_submit(s, s->io_q.blocked, s->io_q.plugged, s->io_q.in_queue, s->io_q.in_flight); if (!s->io_q.blocked &&