From patchwork Wed Jul 14 11:24:12 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 58875 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 1CFB4B6EFE for ; Wed, 14 Jul 2010 21:37:57 +1000 (EST) Received: from localhost ([127.0.0.1]:41749 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OZ0Hh-0006JU-Nf for incoming@patchwork.ozlabs.org; Wed, 14 Jul 2010 07:37:53 -0400 Received: from [140.186.70.92] (port=53602 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OZ057-0006b6-Pg for qemu-devel@nongnu.org; Wed, 14 Jul 2010 07:24:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OZ055-0001V6-UM for qemu-devel@nongnu.org; Wed, 14 Jul 2010 07:24:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25652) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OZ055-0001Uy-NU for qemu-devel@nongnu.org; Wed, 14 Jul 2010 07:24:51 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o6EBOk1K002165 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 14 Jul 2010 07:24:46 -0400 Received: from dhcp-5-188.str.redhat.com (vpn2-8-54.ams2.redhat.com [10.36.8.54]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o6EBOFBq023208; Wed, 14 Jul 2010 07:24:44 -0400 From: Kevin Wolf To: aurelien@aurel32.net Date: Wed, 14 Jul 2010 13:24:12 +0200 Message-Id: <1279106653-24351-14-git-send-email-kwolf@redhat.com> In-Reply-To: <1279106653-24351-1-git-send-email-kwolf@redhat.com> References: <1279106653-24351-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [Qemu-devel] [STABLE][PATCH 13/14] block: Fix early failure in multiwrite X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org bdrv_aio_writev may call the callback immediately (and it will commonly do so in error cases). Current code doesn't consider this. For details see the comment added by this patch. Signed-off-by: Kevin Wolf (cherry picked from commit 453f9a1652629e5805995b165be2e634c8487139) Conflicts: block.c Signed-off-by: Kevin Wolf --- block.c | 37 ++++++++++++++++++++++++++++++------- 1 files changed, 30 insertions(+), 7 deletions(-) diff --git a/block.c b/block.c index e3b3a55..80f2fae 100644 --- a/block.c +++ b/block.c @@ -1802,8 +1802,29 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs) // Check for mergable requests num_reqs = multiwrite_merge(bs, reqs, num_reqs, mcb); - // Run the aio requests + /* + * Run the aio requests. As soon as one request can't be submitted + * successfully, fail all requests that are not yet submitted (we must + * return failure for all requests anyway) + * + * num_requests cannot be set to the right value immediately: If + * bdrv_aio_writev fails for some request, num_requests would be too high + * and therefore multiwrite_cb() would never recognize the multiwrite + * request as completed. We also cannot use the loop variable i to set it + * when the first request fails because the callback may already have been + * called for previously submitted requests. Thus, num_requests must be + * incremented for each request that is submitted. + * + * The problem that callbacks may be called early also means that we need + * to take care that num_requests doesn't become 0 before all requests are + * submitted - multiwrite_cb() would consider the multiwrite request + * completed. A dummy request that is "completed" by a manual call to + * multiwrite_cb() takes care of this. + */ + mcb->num_requests = 1; + for (i = 0; i < num_reqs; i++) { + mcb->num_requests++; acb = bdrv_aio_writev(bs, reqs[i].sector, reqs[i].qiov, reqs[i].nb_sectors, multiwrite_cb, mcb); @@ -1811,23 +1832,25 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs) // We can only fail the whole thing if no request has been // submitted yet. Otherwise we'll wait for the submitted AIOs to // complete and report the error in the callback. - if (mcb->num_requests == 0) { - reqs[i].error = -EIO; + if (i == 0) { goto fail; } else { - mcb->num_requests++; multiwrite_cb(mcb, -EIO); break; } - } else { - mcb->num_requests++; } } + /* Complete the dummy request */ + multiwrite_cb(mcb, 0); + return 0; fail: - free(mcb); + for (i = 0; i < mcb->num_callbacks; i++) { + reqs[i].error = -EIO; + } + qemu_free(mcb); return -1; }