From patchwork Wed Jun 22 19:51:02 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Snow X-Patchwork-Id: 9193691 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 5240E6075F for ; Wed, 22 Jun 2016 19:52:00 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4281028402 for ; Wed, 22 Jun 2016 19:52:00 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 36E4628417; Wed, 22 Jun 2016 19:52:00 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 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 mail.wl.linuxfoundation.org (Postfix) with ESMTPS id DBCAE28402 for ; Wed, 22 Jun 2016 19:51:59 +0000 (UTC) Received: from localhost ([::1]:60511 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFoBr-0001F4-0n for patchwork-qemu-devel@patchwork.kernel.org; Wed, 22 Jun 2016 15:51:59 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53396) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFoBC-00019G-Qs for qemu-devel@nongnu.org; Wed, 22 Jun 2016 15:51:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bFoBA-0004ZO-Tz for qemu-devel@nongnu.org; Wed, 22 Jun 2016 15:51:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47323) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bFoB2-0004Xx-A1; Wed, 22 Jun 2016 15:51:08 -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 D19F2C05B1DD; Wed, 22 Jun 2016 19:51:07 +0000 (UTC) Received: from scv.usersys.redhat.com (dhcp-17-171.bos.redhat.com [10.18.17.171]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u5MJp5bg010740; Wed, 22 Jun 2016 15:51:07 -0400 From: John Snow To: qemu-block@nongnu.org Date: Wed, 22 Jun 2016 15:51:02 -0400 Message-Id: <1466625064-11280-2-git-send-email-jsnow@redhat.com> In-Reply-To: <1466625064-11280-1-git-send-email-jsnow@redhat.com> References: <1466625064-11280-1-git-send-email-jsnow@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]); Wed, 22 Jun 2016 19:51:07 +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 1/3] mirror: clarify mirror_do_read return code 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, jcody@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, John Snow Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP mirror_do_read intends to return the number of sectors processed after the starting sector, without regard to how many sectors were processed before the starting sector due to alignment. Clean up the comments and code to hopefully illustrate this more clearly. This also fixes an issue in initialization where if the mirror buffer size is initialized to smaller than the number of sectors being requested for transfer, we report back an incorrectly large number to the caller. Signed-off-by: John Snow Reviewed-by: Eric Blake Reviewed-by: Fam Zheng --- block/mirror.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index a04ed9c..2ba9642 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -218,7 +218,9 @@ static inline void mirror_wait_for_io(MirrorBlockJob *s) } /* Submit async read while handling COW. - * Returns: nb_sectors if no alignment is necessary, or + * Returns: The number of sectors copied after and including sector_num, + * excluding any sectors copied prior to sector_num due to alignment. + * This will be nb_sectors if no alignment is necessary, or * (new_end - sector_num) if tail is rounded up or down due to * alignment or buffer limit. */ @@ -227,7 +229,7 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num, { BlockBackend *source = s->common.blk; int sectors_per_chunk, nb_chunks; - int ret = nb_sectors; + int ret; MirrorOp *op; sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS; @@ -235,6 +237,7 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num, /* We can only handle as much as buf_size at a time. */ nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors); assert(nb_sectors); + ret = nb_sectors; if (s->cow_bitmap) { ret += mirror_cow_align(s, §or_num, &nb_sectors);