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Tue, 13 Aug 2019 15:04:19 +0000 (UTC) To: Kevin Wolf References: <35b23140-25d5-627e-7a86-4b50fbc5be52@redhat.com> <3d5fcc5b-cdb0-f028-1ea2-af85850db20e@virtuozzo.com> <15cf7372-826a-0684-d6ad-90deea36959e@virtuozzo.com> <43fb7754-6f94-00f6-6172-70cbb53e787c@virtuozzo.com> <94ccf129-cc7e-2778-7688-fd718f8df249@virtuozzo.com> <20190813115115.GG4663@localhost.localdomain> <48fa03d6-259d-9ded-dacb-a4975f8d24e4@virtuozzo.com> <20190813150303.GK4663@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 17:04:18 +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: <20190813150303.GK4663@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="X6YRewNllq3g3hDyuJl6T9ou5StReP0HE" 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 15:04:21 +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 0/2] deal with BDRV_BLOCK_RAW 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" , Denis Lunev 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) --X6YRewNllq3g3hDyuJl6T9ou5StReP0HE Content-Type: multipart/mixed; boundary="88SGst3zyB0DYtRgIzx92wxFrVopd0KvC"; protected-headers="v1" From: Max Reitz To: Kevin Wolf Cc: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" , "qemu-devel@nongnu.org" , Denis Lunev Message-ID: Subject: Re: [PATCH 0/2] deal with BDRV_BLOCK_RAW References: <35b23140-25d5-627e-7a86-4b50fbc5be52@redhat.com> <3d5fcc5b-cdb0-f028-1ea2-af85850db20e@virtuozzo.com> <15cf7372-826a-0684-d6ad-90deea36959e@virtuozzo.com> <43fb7754-6f94-00f6-6172-70cbb53e787c@virtuozzo.com> <94ccf129-cc7e-2778-7688-fd718f8df249@virtuozzo.com> <20190813115115.GG4663@localhost.localdomain> <48fa03d6-259d-9ded-dacb-a4975f8d24e4@virtuozzo.com> <20190813150303.GK4663@localhost.localdomain> In-Reply-To: <20190813150303.GK4663@localhost.localdomain> --88SGst3zyB0DYtRgIzx92wxFrVopd0KvC Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 13.08.19 17:03, Kevin Wolf wrote: > Am 13.08.2019 um 16:53 hat Max Reitz geschrieben: >> On 13.08.19 16:46, Vladimir Sementsov-Ogievskiy wrote: >>> 13.08.2019 17:31, Max Reitz wrote: >>>> On 13.08.19 13:51, Kevin Wolf wrote: >>>> >>>> [...] >>>> >>>>> Hm... This is a mess. :-) >>>> >>>> Just out of curiosity: Why? >>>> >>>> Aren=E2=80=99t there only two things we really need from the block_s= tatus >>>> infrastructure? >>>> >>>> (1) Whether something is allocated in the given layer of the backing= chain, >>>> >>>> (2) Whether we know that a given range reads as zeroes. >>>> >>>> Do we really need anything else? >>>> >>> >>> qemu-img map? >> >> Which is a debugging tool. So it doesn=E2=80=99t fall under =E2=80=9C= really=E2=80=9D in my >> book. If removing everything but allocation+zero information would ma= ke >> the code a lot simpler, I think that would be worth it. >> >>> 1. We need to fix the bug somehow >>> 2. We need to fix comment about different block-status flags, as it r= eally >>> lacks information of what actually "DATA" means (together with *file)= =2E >>> And what finally means "allocated", can you define it precisely? >> >> As I wrote in my other mails, I think the problem is that it=E2=80=99s= just >> unexpected that block_status automatically skips through for filters. >> It shouldn=E2=80=99t, that=E2=80=99s just black magic that the caller = should not rely on. >> >> (We see precisely here that it=E2=80=99s wrong, because the callers ar= e not >> prepared for the allocation information returned to be associated with= a >> different node than what they passed.) >> >> So my definition is just =E2=80=9CIf the node has a COW backing file a= nd >> block_status returns =E2=80=98not allocated=E2=80=99, the data will be= there. >> Otherwise, the data is in the current node.=E2=80=9D Yes, that means = that >> filters should appear as fully allocated. >=20 > You can do that, but then the callers need to learn to do the recursion= > instead. After all, just copying everything if a filter is in the > subtree isn't the desired behaviour. Yes, hence the =E2=80=9Cdeal with filters=E2=80=9D series. Max --88SGst3zyB0DYtRgIzx92wxFrVopd0KvC-- --X6YRewNllq3g3hDyuJl6T9ou5StReP0HE Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl1S0XIACgkQ9AfbAGHV z0BdFggAxLh8edib3SUF5/bJfgxioUYqyos5HrOx8z38tVuRrpXRc+drSEiLD92/ Ys0ppBT1TiVyYZ3jIKtkRIE1Mb3fhzC+fNDvPZuPZCLrSejqxNnDLH5e2TKWm7Xw Fvy+SUMCQHMjhcGAH3ViCLn10FSMOby7uM38UpSkfRG1EGLcVftkb4Rx+AolI+Gi f0L1YY7GJAV49gyuftoapvdT8n4KSNfTLZKgrjzOOjSo6OvPoo141P0cX2cH/Xjm BxdOGfv89mNRZ8AhD3t1m8oT7+h9LZl31repR+hvR7cxncDFe9wQ1ZMzsKd+B2gK udvJw7MOkGn2jtjIIJKGNt9aEpXMcg== =SM0j -----END PGP SIGNATURE----- --X6YRewNllq3g3hDyuJl6T9ou5StReP0HE--