From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41557) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z4Vb2-00041k-PL for qemu-devel@nongnu.org; Mon, 15 Jun 2015 10:42:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z4Vax-0004ki-QE for qemu-devel@nongnu.org; Mon, 15 Jun 2015 10:42:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43707) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z4Vax-0004kW-Kq for qemu-devel@nongnu.org; Mon, 15 Jun 2015 10:42:39 -0400 Date: Mon, 15 Jun 2015 15:42:37 +0100 From: Stefan Hajnoczi Message-ID: <20150615144237.GH9410@stefanha-thinkpad.redhat.com> References: <1433776886-27239-1-git-send-email-vsementsov@virtuozzo.com> <1433776886-27239-3-git-send-email-vsementsov@virtuozzo.com> <20150610143041.GE2430@stefanha-thinkpad.home> <557B2CC9.5020309@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="nOM8ykUjac0mNN89" Content-Disposition: inline In-Reply-To: <557B2CC9.5020309@redhat.com> Subject: Re: [Qemu-devel] [PATCH 2/8] qcow2: add dirty-bitmaps feature List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: John Snow Cc: kwolf@redhat.com, Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy , den@openvz.org, pbonzini@redhat.com --nOM8ykUjac0mNN89 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jun 12, 2015 at 03:02:33PM -0400, John Snow wrote: >=20 >=20 > On 06/10/2015 10:30 AM, Stefan Hajnoczi wrote: > > On Mon, Jun 08, 2015 at 06:21:20PM +0300, Vladimir Sementsov-Ogievskiy = wrote: > >=20 > > I noticed a corner case, it's probably not a problem in practice: > >=20 > > Since the dirty bitmap is stored with the help of a BlockDriverState > > (and its bs->file), it's possible that writing the bitmap will cause > > bits in the bitmap to be dirtied! > >=20 >=20 > But since it's metadata and not stored within a disk sector, can this > actually happen? Do you have an example of a scenario where this might > come up? The persistent dirty bitmap for bs->file is storeed in the qcow2 BDS. This results in recursion. This is a misconfiguration but I just want to understand what happens when someone does this by mistake. Stefan --nOM8ykUjac0mNN89 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJVfuRcAAoJEJykq7OBq3PINrgH/An0N5ELhMtWqUlYtVZFJVKD SnOe71PUyepmtMLdudw3Ub/dujLvbr4y98ZHQFK0rbIpQYaNNTIlVCQbC1CXEWjS R8s0eqAW/V1H6xRjCoSBKxqM2lo9TQtsly7wkisyRNdWnIEQI7QLXtGdC5SnOPkG A6pl79+lp/UMCd4UCFJiNVe4le2fE0RqgOiaq+vOPx/iUBbbg8sXgarx4/nV5Rt/ E/0RY6YnkWYN/nala2CvPlDIMrorGs+eEZnWgU6tAuwxpBcZlpZSTaaN5NKvI7Aj zzUpy/f7zaJXncjqH6ZFCP3iEcxHo2LB6RSMvdwrxCnuf3RbrbQ2+tgMv1e17vc= =4rwz -----END PGP SIGNATURE----- --nOM8ykUjac0mNN89--