From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:52865) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h3NdQ-0008Fb-GU for qemu-devel@nongnu.org; Mon, 11 Mar 2019 12:18:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h3NdP-0008U7-Jc for qemu-devel@nongnu.org; Mon, 11 Mar 2019 12:18:40 -0400 References: <20190305234337.18353-1-jsnow@redhat.com> From: Eric Blake Message-ID: <3a8ed35f-e50b-c411-2004-38917d2164c6@redhat.com> Date: Mon, 11 Mar 2019 11:18:30 -0500 MIME-Version: 1.0 In-Reply-To: <20190305234337.18353-1-jsnow@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="IlhQCBgyQqq6WEAAyjFsu5y93UxfUIwyt" Subject: Re: [Qemu-devel] [PATCH 0/5] block/qcow2-bitmap: Enable resize with persistent bitmaps List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: John Snow , qemu-devel@nongnu.org Cc: vsementsov@virtuozzo.com, Kevin Wolf , qemu-block@nongnu.org, Max Reitz This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --IlhQCBgyQqq6WEAAyjFsu5y93UxfUIwyt From: Eric Blake To: John Snow , qemu-devel@nongnu.org Cc: vsementsov@virtuozzo.com, Kevin Wolf , qemu-block@nongnu.org, Max Reitz Message-ID: <3a8ed35f-e50b-c411-2004-38917d2164c6@redhat.com> Subject: Re: [PATCH 0/5] block/qcow2-bitmap: Enable resize with persistent bitmaps References: <20190305234337.18353-1-jsnow@redhat.com> In-Reply-To: <20190305234337.18353-1-jsnow@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 3/5/19 5:43 PM, John Snow wrote: > This series aims to enable block resizes when persistent bitmaps are > in use. The basic approach here is to recognize that we now load all > persistent bitmaps in memory, and so we can rely on in-memory resizes > and then flush the changed metadata back to disk. >=20 > One part that is potentially now quite strange is that bitmap resizes > may happen twice: once during the qcow2 resize event only if persistent= > bitmaps are found, and then again as part of the generic resize callbac= k > event whether or not we have any persistent bitmaps. >=20 > The second round is required if we are not using qcow2 or we have only > transient bitmaps. The first round is required as we wish to flush the > bitmaps back to disk atomically with the qcow2 resize to avoid violatin= g > our invariants for the bitmap metadata which is checked in many places.= >=20 > This is harmless; hbitmap_truncate will recognize the second round as > a no-op. FWIW - I have not yet reviewed this series closely, but I think it would be wise to get this initial cut in before softfreeze (we can make further tweaks to fix bugs in assumptions during rc1 and rc2, but it's a lot harder to add the series at all if it misses softfreeze). --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --IlhQCBgyQqq6WEAAyjFsu5y93UxfUIwyt Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAlyGilYACgkQp6FrSiUn Q2qAEAf+InN1DB/AfA7EKySnIImIrrdG9kRECroZMddiAD74l8AVB3I8Y7Rph4+G it40aPDXu/S+sAivKNcul3nG6VARENxb5NIeHd3usKKwEvjWObpW0w5kWKajK4uV RyHSj8QEkwqPxuZJoYL+7pxrjZoUzEWsI0Fqj/B3YkWkUtiPVgWzCq5YQ+/Q4rr7 qoOnzo5CKIW5oa31rcAozD58kWkHgFX6MwpxHm3uQwaAI70JWL0r6LcCt5VBxIBG aMhF+2sTv2Rw7aLLj3C8NVebDAx+DMxsoZs5LK++ZzJ5GsT9tzRspiTZpFPw/tk2 RteIVA5g30qiOIlRFKtDDCAKGN/7BQ== =YjeL -----END PGP SIGNATURE----- --IlhQCBgyQqq6WEAAyjFsu5y93UxfUIwyt--