From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:50493)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1assje-0004XK-T9
	for qemu-devel@nongnu.org; Wed, 20 Apr 2016 10:04:11 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <kwolf@redhat.com>) id 1assjZ-0007Td-AY
	for qemu-devel@nongnu.org; Wed, 20 Apr 2016 10:04:06 -0400
Date: Wed, 20 Apr 2016 16:03:52 +0200
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20160420140352.GM6517@noname.str.redhat.com>
References: <1461120516-14569-1-git-send-email-famz@redhat.com>
	<1461120516-14569-2-git-send-email-famz@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1461120516-14569-2-git-send-email-famz@redhat.com>
Subject: Re: [Qemu-devel] [PATCH for-2.6 v2 1/3] mirror: Don't extend the
 last sub-chunk
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel/>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, Jeff Cody <jcody@redhat.com>, Max Reitz <mreitz@redhat.com>, qemu-block@nongnu.org

Am 20.04.2016 um 04:48 hat Fam Zheng geschrieben:
> The last sub-chunk is rounded up to the copy granularity in the target
> image, resulting in a larger size than the source.
> 
> Add a function to clip the copied sectors to the end.
> 
> This undoes the "wrong" changes to tests/qemu-iotests/109.out in
> e5b43573e28. The remaining two offset changes are okay.
> 
> Reported-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Fam Zheng <famz@redhat.com>

I think you're missing at least one place where we need DIV_ROUND_UP
now. Specifically I'm talking about the calculation of nb_chunks in
mirror_iteration_done(), which causes the partial last cluster to stay
marked as in-flight forever.

I would also have used DIV_ROUND_UP in mirror_iteration(), but there we
have a sector_num < end check which saves us from an endless loop.

In order to reproduce the bug, this hangs for me without DIV_ROUND_UP:

$ ls -l /tmp/test.raw
-rw-r--r--. 1 kwolf kwolf 1049600 20. Apr 15:57 /tmp/test.raw
$ (echo -e "drive_mirror none0 /tmp/copy.raw raw\n"; sleep 1; echo -e 'qemu-io none0 "write 1M 512"\nblock_job_complete none0\nquit') | x86_64-softmmu/qemu-system-x86_64 -drive if=none,file=/tmp/test.raw -monitor stdio

Kevin