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Tue, 13 Aug 2019 14:49:24 +0000 (UTC) To: Kevin Wolf References: <20190725155512.9827-1-mreitz@redhat.com> <20190725155512.9827-4-mreitz@redhat.com> <627fbb64-5ffe-aca7-6198-9d991d4219e3@virtuozzo.com> <20190813103838.GD4663@localhost.localdomain> From: Max Reitz Openpgp: preference=signencrypt 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: Tue, 13 Aug 2019 16:49:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190813103838.GD4663@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="jT3F8aajEuFHNDKvzp5LNZ8LoKK9QTqWS" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Tue, 13 Aug 2019 14:49:25 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 3/3] vpc: Do not return RAW from block_status 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: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" , "qemu-block@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) --jT3F8aajEuFHNDKvzp5LNZ8LoKK9QTqWS Content-Type: multipart/mixed; boundary="umaa6q5ZV3IHLOS9UHFyqk2UXRZWLT0WK"; protected-headers="v1" From: Max Reitz To: Kevin Wolf Cc: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" , "qemu-devel@nongnu.org" Message-ID: Subject: Re: [PATCH 3/3] vpc: Do not return RAW from block_status References: <20190725155512.9827-1-mreitz@redhat.com> <20190725155512.9827-4-mreitz@redhat.com> <627fbb64-5ffe-aca7-6198-9d991d4219e3@virtuozzo.com> <20190813103838.GD4663@localhost.localdomain> In-Reply-To: <20190813103838.GD4663@localhost.localdomain> --umaa6q5ZV3IHLOS9UHFyqk2UXRZWLT0WK Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 13.08.19 12:38, Kevin Wolf wrote: > Am 12.08.2019 um 17:56 hat Max Reitz geschrieben: >> On 12.08.19 17:33, Vladimir Sementsov-Ogievskiy wrote: >>> 25.07.2019 18:55, Max Reitz wrote: >>>> vpc is not really a passthrough driver, even when using the fixed >>>> subformat (where host and guest offsets are equal). It should handl= e >>>> preallocation like all other drivers do, namely by returning >>>> DATA | RECURSE instead of RAW. >>>> >>>> There is no tangible difference but the fact that bdrv_is_allocated(= ) no >>>> longer falls through to the protocol layer. >>> >>> Hmm. Isn't a real bug (fixed by this patch) ? >>> >>> Assume vpc->file is qcow2 with backing, which have "unallocated" regi= on, which is >>> backed by actual data in backing file. >> >> Come on now. >> >>> So, this region will be reported as not allocated and will be skipped= by any copying >>> loop using block-status? Is it a bug of BDRV_BLOCK_RAW itself? Or I d= on't understand >>> something.. >> >> I think what you don=E2=80=99t understand is that if you have a vpc fi= le inside >> of a qcow2 file, you=E2=80=99re doing basically everything wrong. ;-) >> >> But maybe we should drop BDRV_BLOCK_RAW... Does it do anything good f= or >> us in the raw driver? Shouldn=E2=80=99t it too just return DATA | REC= URSE? >=20 > DATA | RECURSE is still DATA, i.e. marks the block as allocated. If you= > do that unconditionally, we will never consider a block unallocated. Which is correct for formats that do not have backing files. > RECURSE doesn't undo this, the only thing it might do is settting ZERO > additionally. >=20 > So I would say unconditionally returning DATA | RECURSE is almost alway= s > wrong. I would say it=E2=80=99s always right when it is a format driver and ther= e is no backing file. Max --umaa6q5ZV3IHLOS9UHFyqk2UXRZWLT0WK-- --jT3F8aajEuFHNDKvzp5LNZ8LoKK9QTqWS Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl1SzfIACgkQ9AfbAGHV z0DeHAf+ONnGIh1/BuVdag2xajMYH4vVRayomWwT0oueMqqrQOChz5VMEaHyVqwu hDXledZ7IAQGrjFHIqjoc2NqsZMVKqRBFnoL8+PkgUsWyT5VN1YQ2UO7RqLgSICq 7dPZ/RRhP/95olPeF26/QzQxnxCLUFSdawoyE9CMeVG2JoDv3Hp8unjIoGRh9IbC Ynxi5rGxG+Iv8DPuOsGYdaqDherjTEWuygioBLPPCm2nOOxF4E1cL83yVlxhsx00 7vw8GZzxoQue3iei9Mvn/1NUjn+aFmDtQyxjr8svqVJ1zKKRt3ayw4Q9UYtB0yFb NW0+sOISBN07Si/bOvlgv0YNt082HQ== =iYVz -----END PGP SIGNATURE----- --jT3F8aajEuFHNDKvzp5LNZ8LoKK9QTqWS--