From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38037) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VK8LK-0001wh-EV for qemu-devel@nongnu.org; Thu, 12 Sep 2013 10:58:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VK8LF-0004ME-DZ for qemu-devel@nongnu.org; Thu, 12 Sep 2013 10:58:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44870) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VK8LF-0004M9-5M for qemu-devel@nongnu.org; Thu, 12 Sep 2013 10:57:57 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r8CEvtO9031978 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 12 Sep 2013 10:57:56 -0400 Message-ID: <5231D673.6050907@redhat.com> Date: Thu, 12 Sep 2013 08:57:55 -0600 From: Eric Blake MIME-Version: 1.0 References: <1378106712-29856-1-git-send-email-mreitz@redhat.com> In-Reply-To: <1378106712-29856-1-git-send-email-mreitz@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Fet1QmDQ0BKCqGt6xOVm6C1SIiFxdccXr" Subject: Re: [Qemu-devel] [PATCH v5 0/8] Add metadata overlap checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: Kevin Wolf , qemu-devel@nongnu.org, Stefan Hajnoczi This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --Fet1QmDQ0BKCqGt6xOVm6C1SIiFxdccXr Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 09/02/2013 01:25 AM, Max Reitz wrote: > If a qcow2 image file becomes corrupted, any write may inadvertently > overwrite important metadata structures such as the L1 table. This > series adds functionality for detecting, preventing and (to some extent= ) > repairing such collisions. >=20 > v5: > - fixed patch 6 (forgot to update the event_names array for the new > event BLKDBG_REFTABLE_UPDATE); no other changes >=20 > v4: > - fixed handling of preallocated zero clusters in patch 4 > - moved OFLAG_COPIED checks into a separate function (this affects > patches 4 and 5); functionality remains unchanged > - patches 1, 2, 3, 6, 7 and 8 remain unmodified (except for line > numbers in block/qcow2-refcount.c) Just now looking at this series, and I have several questions. It looks like Kevin applied v4 rather than v5; have we fixed that up? Next, what sort of overhead do these new checks add to the write case? Is it something that would be a noticeable slowdown? I'd love to see some benchmark numbers (hopefully, the default set of checks are in the noise compared to the overhead of actual I/O). Also, is there a way to tune the set of checks used at runtime, or are we stuck with the compiled-in default? That is, can a user opt in to more expensive tests for robustness, or opt out of default tests for speed, via a runtime command, or is it something where they have to recompile to choose a different QCOW2_OL_DEFAULT value? --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --Fet1QmDQ0BKCqGt6xOVm6C1SIiFxdccXr Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJSMdZzAAoJEKeha0olJ0Nqm6UH/RjxGsJvL0AWritYqWnYlY5E EvTDNnaRVneZrMxszl6DwVy9A86wsXWU1MD/2YJYrKdn+tXFwCMSqI/yIJ2npCUt W5smXbeJtFP8piaxpYWEw9C35tl9y5YVAqObyLj/VWzPJlSZOOCQROH1ke+gT4Nm 8GfnQmLpmUzX1mUqjEJpyQufaF1vLyroXpTknwzd5kmtxU5w+ribx2qmP2n00IKN aC2dVjExbtM0ATCZShbJibFcs6luRKQTj2iPePlTeB/3WAk7RyV+ZrUnynPbL6e2 lY1fSWnLPZ8ix3eOIsW0BT+iaSMo+vEzdStnd6jm6ICBzsMOOiVRyVtjsYL5aZQ= =aK4M -----END PGP SIGNATURE----- --Fet1QmDQ0BKCqGt6xOVm6C1SIiFxdccXr--