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Mon, 28 Oct 2019 11:10:59 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-117-83.ams2.redhat.com [10.36.117.83]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EC26667600; Mon, 28 Oct 2019 11:10:55 +0000 (UTC) Subject: Re: [PATCH 0/8] block: Add @exact parameter to bdrv_co_truncate() To: qemu-block@nongnu.org References: <20190918095144.955-1-mreitz@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: <0dbdc19b-c740-92e1-4ee7-294d3d7581e1@redhat.com> Date: Mon, 28 Oct 2019 12:10:54 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20190918095144.955-1-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="yBBtTOcrqWgaU6ApJEKiI8nbLj6PMeLkJ" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 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: Kevin Wolf , Fam Zheng , qemu-devel@nongnu.org, Stefan Hajnoczi , Maxim Levitsky 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) --yBBtTOcrqWgaU6ApJEKiI8nbLj6PMeLkJ Content-Type: multipart/mixed; boundary="DfuUGou6JQGaPermJIjMsnzC1fxRzDwT5" --DfuUGou6JQGaPermJIjMsnzC1fxRzDwT5 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 18.09.19 11:51, Max Reitz wrote: > Hi, >=20 > This series is supposed to pull out some of the problems from my > =E2=80=9CGeneric file creation fallback=E2=80=9D series. >=20 > The blk_truncate_for_formatting() function added there was buggy, as > Maxim noted, in that it did not check whether blk_truncate() actually > resized the block node to the target offset. One way to fix this is to > add a parameter to it that forces the block driver to do so, and that is > done by this series. >=20 > I think this is generally useful (you can see the diff stat saldo is > only +23 lines), because it allows us to drop a special check in > qemu-img resize, and it fixes a bug in qed (which has relied on this > behavior for over 8 years, but unfortunately bdrv_truncate()=E2=80=99s be= havior > changed quite exactly 8 years ago). >=20 > However, in the process I noticed we actually don=E2=80=99t need > blk_truncate_for_formatting(): The underlying problem is that some > format drivers truncate their underlying file node to 0 before > formatting it to drop all data. So they should pass exact=3Dtrue, but > they cannot, because this would break creation on block devices. Hence > blk_truncate_for_formatting(). >=20 > It turns out, though, that three of the four drivers in question don=E2= =80=99t > need to truncate their file node at all. The remaining one is qed which > simply really should pass exact=3Dtrue (it=E2=80=99s a bug fix). >=20 > (I do drop those blk_truncate() invocations in this series, because > otherwise I feel like it is impossible to decide whether they should get > exact=3Dfalse or exact=3Dtrue. Either way is wrong.) Thanks for the review, I=E2=80=99ve applied the series to my block branch a= nd changed the comment in qed.c as requested and suggested by Maxim on patch 7= : https://git.xanclic.moe/XanClic/qemu/commits/branch/block Max --DfuUGou6JQGaPermJIjMsnzC1fxRzDwT5-- --yBBtTOcrqWgaU6ApJEKiI8nbLj6PMeLkJ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl22zL4ACgkQ9AfbAGHV z0BFvAgAoRgG5m6J/MnfL+xDj0uBA6vDUlwZ3srH0V/6O1/2hgnv47nr0HD/NvQp bQc8AmR68r0NWhFq57Y6hi3Vjgoz1tFRJRFEAM1y9mzJX2848eh2QFnKtecGNOTe J5eiv2B3DzeyykCZ/PNsMizhRwkSLJ+pH9H9IMDElaaxw/JVRRBOEhNfyhPZ9OVD RLYnirHhES73TjNo9Xyni2nQ5JhP3hj/Jf1lFFKqCp8oS2GOR2wX5xzrFY0dLAOm GkFU6uKWq27UPk2uW5iEM19dGIYC8aD7+2+6Moe1CGrClf4Gt5WxUPSnTPcNQU9z sqa+BNmiMvSjL8JYQOqkbyUtJkIDJg== =2dKI -----END PGP SIGNATURE----- --yBBtTOcrqWgaU6ApJEKiI8nbLj6PMeLkJ--