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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191120184501.28159-3-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="NYhBkZZFlBegMCyJsGYFenQqvujgOVOE3" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: vsementsov@virtuozzo.com, qemu-devel@nongnu.org, stefanha@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --NYhBkZZFlBegMCyJsGYFenQqvujgOVOE3 Content-Type: multipart/mixed; boundary="CHnrdGmI2BKNMjhcj2vRq1ExJve6kb7rM" --CHnrdGmI2BKNMjhcj2vRq1ExJve6kb7rM Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 20.11.19 19:44, Kevin Wolf wrote: > When extending the size of an image that has a backing file larger than > its old size, make sure that the backing file data doesn't become > visible in the guest, but the added area is properly zeroed out. >=20 > Consider the following scenario where the overlay is shorter than its > backing file: >=20 > base.qcow2: AAAAAAAA > overlay.qcow2: BBBB >=20 > When resizing (extending) overlay.qcow2, the new blocks should not stay > unallocated and make the additional As from base.qcow2 visible like > before this patch, but zeros should be read. >=20 > A similar case happens with the various variants of a commit job when an > intermediate file is short (- for unallocated): >=20 > base.qcow2: A-A-AAAA > mid.qcow2: BB-B > top.qcow2: C--C--C- >=20 > After commit top.qcow2 to mid.qcow2, the following happens: >=20 > mid.qcow2: CB-C00C0 (correct result) > mid.qcow2: CB-C--C- (before this fix) >=20 > Without the fix, blocks that previously read as zeros on top.qcow2 > suddenly turn into A. >=20 > Signed-off-by: Kevin Wolf > --- > block/io.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) Zeroing the intersection may take some time. So is it right for QMP=E2=80= =99s block_resize to do this, seeing it is a synchronous operation? As far as I can tell, jobs actually have the same problem. I don=E2=80=99t think mirror or commit have a pause point before truncating, so they still block the monitor there, don=E2=80=99t they? Max --CHnrdGmI2BKNMjhcj2vRq1ExJve6kb7rM-- --NYhBkZZFlBegMCyJsGYFenQqvujgOVOE3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl3WUgcACgkQ9AfbAGHV z0Cwuwf+OgNqEVrwZ/FgSuVxij3HQswcoHZcYOkb44uG9xH7CzjyJz6C7qfDgEp3 9oP2/ag32/Wq9lmtnreHKxRl9+tunYB2ukre2uhD2qtnGpEpX9HLvNANv1kjSidL HbAz205MdoEJJ6Ux2eVsMfxYM7Gk9CoACT5Ddxghgu6H9p3FGoxqBD+fBSNuhemu GZ09C8O600TxOQtub83GEYgdBTLxrti+Ac/f5X0oiy+rmjoE2gWHoDXA6+sSVYaW 3bXv6wsdgl0Bpcxm9F80bATQcUYsXuwZlc3XdDjuaf6Qypto8dRhYx25lYnPVndH cawhkRFCC6VzWRjCwN0uEkZc/kmBcg== =1dIf -----END PGP SIGNATURE----- --NYhBkZZFlBegMCyJsGYFenQqvujgOVOE3--