From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54266) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VgWF4-00074h-Fs for qemu-devel@nongnu.org; Wed, 13 Nov 2013 03:56:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VgWEz-0007Jq-EE for qemu-devel@nongnu.org; Wed, 13 Nov 2013 03:56:06 -0500 Received: from mx3-phx2.redhat.com ([209.132.183.24]:55627) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VgWEz-0007Jk-5h for qemu-devel@nongnu.org; Wed, 13 Nov 2013 03:56:01 -0500 Date: Wed, 13 Nov 2013 03:55:59 -0500 (EST) From: Miroslav Rezanina Message-ID: <795456228.30035773.1384332959394.JavaMail.root@redhat.com> In-Reply-To: <1384315458-23417-1-git-send-email-famz@redhat.com> References: <1384315458-23417-1-git-send-email-famz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qemu-img: Fix content mismatch offset of image compare List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fam Zheng Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com ----- Original Message ----- > From: "Fam Zheng" > To: qemu-devel@nongnu.org > Cc: stefanha@redhat.com, kwolf@redhat.com, "Miroslav Rezanina" > Sent: Wednesday, November 13, 2013 5:04:18 AM > Subject: [PATCH] qemu-img: Fix content mismatch offset of image compare > > We were lucky to pass qemu-iotests 048 (qemu-img compare case) but when > I tried to run with TEST_DIR=/tmp (tmpfs), it fails with a very weird > mismatch offset. This fixes the bug. > > In the if branch, setting ret to 1 before using it makes dead code in > the next line: pnum is never added to mismatch offset even if ret was 0. > > Signed-off-by: Fam Zheng > --- > qemu-img.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/qemu-img.c b/qemu-img.c > index bf3fb4f..2bab20d 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -1020,10 +1020,10 @@ static int img_compare(int argc, char **argv) > } > ret = compare_sectors(buf1, buf2, nb_sectors, &pnum); > if (ret || pnum != nb_sectors) { > - ret = 1; > qprintf(quiet, "Content mismatch at offset %" PRId64 > "!\n", > sectors_to_bytes( > ret ? sector_num : sector_num + pnum)); > + ret = 1; > goto out; > } > } > -- > 1.8.4.2 > > Correct fix, setting variable to constant before test is definitely wrong. Reviewed-by: Miroslav Rezanina -- Miroslav Rezanina Software Engineer - Virtualization Team