From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:33157)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <jsnow@redhat.com>) id 1ZV0Lo-0001Y7-PV
	for qemu-devel@nongnu.org; Thu, 27 Aug 2015 12:48:33 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <jsnow@redhat.com>) id 1ZV0Ln-0001Dc-RA
	for qemu-devel@nongnu.org; Thu, 27 Aug 2015 12:48:32 -0400
References: <CAFEAcA8CpHkkVi9_BUomseA1mB+6au2ybfdAxKC9D3V6T0eD4Q@mail.gmail.com>
	<55DF2CDA.1070609@redhat.com>
From: John Snow <jsnow@redhat.com>
Message-ID: <55DF3F58.4070809@redhat.com>
Date: Thu, 27 Aug 2015 12:48:24 -0400
MIME-Version: 1.0
In-Reply-To: <55DF2CDA.1070609@redhat.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] hd-geo-test creates 4GB files on FSes that don't
 support sparse images, doesn't delete them on error
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: Eric Blake <eblake@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>
Cc: Markus Armbruster <armbru@redhat.com>, Qemu-block <qemu-block@nongnu.org>



On 08/27/2015 11:29 AM, Eric Blake wrote:
> On 08/27/2015 09:17 AM, Peter Maydell wrote:
>> I've noticed recently that tests/hd-geo-test.c creates test disk
>> images which are 4GB in size, which is a problem if the filesystem
>> on the host doesn't support sparse files. In particular, OSX's HFS+
>> doesn't have sparse file support, and Windows probably doesn't either.
> 
> Windows NTFS supports sparse files (minimum hole size of 64k), but it
> can be a pain to set up, and while it saves disk space, it may actually
> slow your program down.
> 
> [At one point cygwin created sparse files on windows by default, but
> because it was demonstrated to hurt performance in dealing with sparse
> files, because Windows doesn't handle sparse files efficiently, the
> cygwin defaults were switched so that it now requires an explicit opt-in
> mount option before even attempting sparse files]
> 
>> Worse, if the test fails an assertion somewhere the test doesn't
>> clean up after itself and leaves a 4GB file lying around in /tmp/.
>>
>> It would be nice if we could skip these tests on filesystems that
>> don't have sparse file support...
> 
> Or even where sparse files are supported but not default.
> 

Does this test *require* the raw format?

Use tests/libqos/libqos.c mkqcow2 instead. I'll send a patch.

--js