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Mon, 9 Sep 2019 08:09:57 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-116-179.ams2.redhat.com [10.36.116.179]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A2B595D6A7; Mon, 9 Sep 2019 08:09:55 +0000 (UTC) To: Kevin Wolf References: <20190809161407.11920-1-mreitz@redhat.com> <20190809161407.11920-12-mreitz@redhat.com> <20190905131129.GB4911@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: Mon, 9 Sep 2019 10:09:53 +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: <20190905131129.GB4911@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nixpVsvusBQEuLQyq5pPTMIZ5mzMnxnBH" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.63]); Mon, 09 Sep 2019 08:09:57 +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 v6 11/42] block: Add bdrv_supports_compressed_writes() 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) --nixpVsvusBQEuLQyq5pPTMIZ5mzMnxnBH Content-Type: multipart/mixed; boundary="7qRg2VnbPlqX2fVp0nZ6p4mDrcu2TNwyd"; protected-headers="v1" From: Max Reitz To: Kevin Wolf Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Vladimir Sementsov-Ogievskiy Message-ID: Subject: Re: [PATCH v6 11/42] block: Add bdrv_supports_compressed_writes() References: <20190809161407.11920-1-mreitz@redhat.com> <20190809161407.11920-12-mreitz@redhat.com> <20190905131129.GB4911@localhost.localdomain> In-Reply-To: <20190905131129.GB4911@localhost.localdomain> --7qRg2VnbPlqX2fVp0nZ6p4mDrcu2TNwyd Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 05.09.19 15:11, Kevin Wolf wrote: > Am 09.08.2019 um 18:13 hat Max Reitz geschrieben: >> Filters cannot compress data themselves but they have to implement >> .bdrv_co_pwritev_compressed() still (or they cannot forward compressed= >> writes). Therefore, checking whether >> bs->drv->bdrv_co_pwritev_compressed is non-NULL is not sufficient to >> know whether the node can actually handle compressed writes. This >> function looks down the filter chain to see whether there is a >> non-filter that can actually convert the compressed writes into >> compressed data (and thus normal writes). >> >> Signed-off-by: Max Reitz >> Reviewed-by: Vladimir Sementsov-Ogievskiy >=20 > Should patches 2 and 3 that add the .bdrv_co_pwritev_compressed() > callback to filter drivers come only after this one? Why not. > And should we also > support it in the mirror filter? Hm. AFAIU, compressed writes have very limited use. You can basically only use them when writing to a new image (where you=E2=80=99d never writ= e anywhere you=E2=80=99ve already written something to), i.e. for qemu-img = convert or the backup target. It makes sense to blockdev-backup to throttle, so that=E2=80=99s why it should be implemented there. I don=E2=80=99t reall= y see how it would make sense for mirror. OTOH, it doesn=E2=80=99t make sense for COR either. And it isn=E2=80=99t= that hard. Now I don=E2=80=99t have a strong preference for either dropping the COR = patch or adding it to mirror as well... Max --7qRg2VnbPlqX2fVp0nZ6p4mDrcu2TNwyd-- --nixpVsvusBQEuLQyq5pPTMIZ5mzMnxnBH Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl12CNEACgkQ9AfbAGHV z0AMIQf/cTthBastzJ2Z62fDneVWVOPEdVin46ZChtH9vXJdpWU63f1YeHQwKMjI fP6Sz5JPgYMzW1b1aK29sCC5M2q2xnZIRZznMtvVE9glqJA2qCNgpfzqlsU//G2u athqwOZlN11LvojO2POG45KYeawUNlrmgJpFY5Sp45ejanCRajvOtLQ04GeZSoGP Y6+H3HCLCe3GOEBaxrq9y7bR3NfnU2PG/sdpVfPhx38/vpcPhSHsoDjr9c6WfKtT yyDNe6pjUc/zBo657QoXsPYu2btjMRCLo3h8b0aMj9lf7VVw9QU0K+jGkIDheU1O Mgr93tDOslchjSWQgrEv3Ya5aPx9fQ== =FhhJ -----END PGP SIGNATURE----- --nixpVsvusBQEuLQyq5pPTMIZ5mzMnxnBH--