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Thu, 23 Apr 2020 18:05:45 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-113-212.ams2.redhat.com [10.36.113.212]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BE4A15D9CC; Thu, 23 Apr 2020 18:05:40 +0000 (UTC) Subject: Re: [PATCH v6 10/10] qcow2: Forward ZERO_WRITE flag for full preallocation To: Kevin Wolf , qemu-block@nongnu.org References: <20200423150127.142609-1-kwolf@redhat.com> <20200423150127.142609-11-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: Thu, 23 Apr 2020 20:05:38 +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: <20200423150127.142609-11-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="aP6YmBds9is5xHVj8iaTIqVYfzIJ5pvEC" 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 = 2020/04/23 02:14:02 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) --aP6YmBds9is5xHVj8iaTIqVYfzIJ5pvEC Content-Type: multipart/mixed; boundary="dFJcVgFUHNvoPAVPGE7WZ29lequt9LwT8" --dFJcVgFUHNvoPAVPGE7WZ29lequt9LwT8 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 23.04.20 17:01, Kevin Wolf wrote: > The BDRV_REQ_ZERO_WRITE is currently implemented in a way that first the > image is possibly preallocated and then the zero flag is added to all > clusters. This means that a copy-on-write operation may be needed when > writing to these clusters, despite having used preallocation, negating > one of the major benefits of preallocation. >=20 > Instead, try to forward the BDRV_REQ_ZERO_WRITE to the protocol driver, > and if the protocol driver can ensure that the new area reads as zeros, > we can skip setting the zero flag in the qcow2 layer. >=20 > Unfortunately, the same approach doesn't work for metadata > preallocation, so we'll still set the zero flag there. >=20 > Signed-off-by: Kevin Wolf > --- > block/qcow2.c | 22 +++++++++++++++++++--- > tests/qemu-iotests/274.out | 4 ++-- > 2 files changed, 21 insertions(+), 5 deletions(-) Oh, nice. I didn=E2=80=99t think you (or anyone else for that matter) woul= d actually do this. :) With the errp thing fixed: Reviewed-by: Max Reitz --dFJcVgFUHNvoPAVPGE7WZ29lequt9LwT8-- --aP6YmBds9is5xHVj8iaTIqVYfzIJ5pvEC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl6h2PIACgkQ9AfbAGHV z0CByAgAimMQMm5rSkaHprIQxHCexmF3aWtmBXwjUEbG+ZJM0e0a4913WF8K5+Dh CC7T2k4XKFFA+KWIXOMA8IiaMLrwOo6QkePHoZdwXqebP/rqjlnE6sZytojLrsW5 ZI3gpjeUxA0l0C5T6LYLCkmNsa9PjNDPqUQcUBOWX06DfBIg+0Opw502H9M2XeOK 9yrQx0M4m1DhJFdc7qrNJSaep/vzux597Jl9RguyQPShmeROaTQU5k58PHQjNFF0 DMSi3rM1fNQgXNwpi2742N9Z6cezoAFxWmOovGavic/pnmnW2IBanXJxuVkbsw4f NSFqLzv3KW5USW7FiGhIEbJnW90+mA== =ARZl -----END PGP SIGNATURE----- --aP6YmBds9is5xHVj8iaTIqVYfzIJ5pvEC--