From patchwork Thu Jun 23 22:37:07 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 639952 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3rbGq83yTRz9sXx for ; Fri, 24 Jun 2016 08:49:08 +1000 (AEST) Received: from localhost ([::1]:39791 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGDQo-0008SW-E5 for incoming@patchwork.ozlabs.org; Thu, 23 Jun 2016 18:49:06 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:32897) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGDFw-0004Rd-GG for qemu-devel@nongnu.org; Thu, 23 Jun 2016 18:37:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bGDFq-0005wz-RI for qemu-devel@nongnu.org; Thu, 23 Jun 2016 18:37:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35636) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGDFb-0005ox-Dl; Thu, 23 Jun 2016 18:37:31 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E7826C05B1F1; Thu, 23 Jun 2016 22:37:30 +0000 (UTC) Received: from red.redhat.com (ovpn-116-212.phx2.redhat.com [10.3.116.212]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u5NMbSVI010930; Thu, 23 Jun 2016 18:37:30 -0400 From: Eric Blake To: qemu-devel@nongnu.org Date: Thu, 23 Jun 2016 16:37:07 -0600 Message-Id: <1466721446-27737-4-git-send-email-eblake@redhat.com> In-Reply-To: <1466721446-27737-1-git-send-email-eblake@redhat.com> References: <1466721446-27737-1-git-send-email-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 23 Jun 2016 22:37:30 +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 v3 03/22] block: Fix harmless off-by-one in bdrv_aligned_preadv() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, famz@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" If the amount of data to read ends exactly on the total size of the bs, then we were wasting time creating a local qiov to read the data in preparation for what would normally be appending zeroes beyond the end, even though this corner case has nothing further to do. Signed-off-by: Eric Blake Reviewed-by: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Stefan Hajnoczi --- v3: no change v2: no change, add R-b --- block/io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/io.c b/block/io.c index 994d3fa..82c9ff0 100644 --- a/block/io.c +++ b/block/io.c @@ -1036,7 +1036,7 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, } max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align); - if (bytes < max_bytes) { + if (bytes <= max_bytes) { ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0); } else if (max_bytes > 0) { QEMUIOVector local_qiov;