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Fri, 24 Apr 2020 14:07:41 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-113-192.ams2.redhat.com [10.36.113.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B98155D70C; Fri, 24 Apr 2020 14:07:36 +0000 (UTC) Subject: Re: [PATCH v7 04/10] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate To: Kevin Wolf , qemu-block@nongnu.org References: <20200424125448.63318-1-kwolf@redhat.com> <20200424125448.63318-5-kwolf@redhat.com> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Fri, 24 Apr 2020 16:07:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200424125448.63318-5-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="gKFvYhRsfWkcnyGodQwMIys8QhNyVeQBy" Received-SPF: pass client-ip=207.211.31.81; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/24 03:11:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: berto@igalia.com, vsementsov@virtuozzo.com, qemu-devel@nongnu.org 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) --gKFvYhRsfWkcnyGodQwMIys8QhNyVeQBy Content-Type: multipart/mixed; boundary="fYN912Q6tURLy0AQlxZZrz7nUEpp2BZUG" --fYN912Q6tURLy0AQlxZZrz7nUEpp2BZUG Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 24.04.20 14:54, Kevin Wolf wrote: > If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling > qcow2_cluster_zeroize() with flags=3D0 does the right thing: It doesn't > undo any previous preallocation, but just adds the zero flag to all > relevant L2 entries. If an external data file is in use, a write_zeroes > request to the data file is made instead. >=20 > Signed-off-by: Kevin Wolf > --- > block/qcow2-cluster.c | 2 +- > block/qcow2.c | 34 ++++++++++++++++++++++++++++++++++ > 2 files changed, 35 insertions(+), 1 deletion(-) [...] > diff --git a/block/qcow2.c b/block/qcow2.c > index 9cfbdfc939..98065d7808 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c [...] > @@ -4214,6 +4215,39 @@ static int coroutine_fn qcow2_co_truncate(BlockDri= verState *bs, int64_t offset, [...] > + /* Write explicit zeros for the unaligned head */ > + if (zero_start > old_length) { > + uint64_t len =3D zero_start - old_length; > + uint8_t *buf =3D qemu_blockalign0(bs, len); I wonder whether I should raise the question of why this should be block-aligned when we make no effort to align the offset its written to (and we know it isn=E2=80=99t aligned to qcow2 clusters at least). I probably should not. Reviewed-by: Max Reitz > + QEMUIOVector qiov; > + qemu_iovec_init_buf(&qiov, buf, len); > + > + qemu_co_mutex_unlock(&s->lock); > + ret =3D qcow2_co_pwritev_part(bs, old_length, len, &qiov, 0,= 0); > + qemu_co_mutex_lock(&s->lock); > + > + qemu_vfree(buf); > + if (ret < 0) { > + error_setg_errno(errp, -ret, "Failed to zero out the new= area"); > + goto fail; > + } > + } --fYN912Q6tURLy0AQlxZZrz7nUEpp2BZUG-- --gKFvYhRsfWkcnyGodQwMIys8QhNyVeQBy Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl6i8qcACgkQ9AfbAGHV z0CHGwf/SggTyahiD49Z7Qi5RToh+BkTGwFuwn5d5atXqGDSDV77C0N93wM3pP5T Btc8VZhZeQnQd+mb1IJc15yytyeL29uPjmdpL7kX29CTpe2IRoMHgV1lWYgRJKY7 MnY2eqoHYw8DvWxUjEdXgeFoVQKbeDr9t9boFqJ/N+EYND2juTxcsCH67jGPPyDe jFCg/2NeFTRy03XRaTKiRZwTNKqQFtqFGgUR9rFq5nfSNtSIpkzyTjcrA2f/8CYB /L58IPIQKTY+srq1ZqaxDrZE70N5cOvE7eNn2q8dve1m+vLfGoHd2+9l4m2RJYqo kwvUG/WeqnxZ1WDrc96n6vgCuRhzZA== =Egyl -----END PGP SIGNATURE----- --gKFvYhRsfWkcnyGodQwMIys8QhNyVeQBy--