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Thu, 6 Feb 2020 11:06:37 +0000 (UTC) Received: from dresden.str.redhat.com (unknown [10.36.118.15]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 54B358885D; Thu, 6 Feb 2020 11:06:36 +0000 (UTC) Subject: Re: [PATCH v2 09/33] block: Add generic bdrv_inherited_options() To: Eric Blake , qemu-block@nongnu.org References: <20200204170848.614480-1-mreitz@redhat.com> <20200204170848.614480-10-mreitz@redhat.com> <87197a53-64e5-ec56-acff-13288256dee0@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: <9e93e4ef-5e20-6b7b-971b-3a3541c6cf31@redhat.com> Date: Thu, 6 Feb 2020 12:06:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <87197a53-64e5-ec56-acff-13288256dee0@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ulKRRD1IDcEJC4gbtDg1dk6J23snjamas" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] 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 , Vladimir Sementsov-Ogievskiy , 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) --ulKRRD1IDcEJC4gbtDg1dk6J23snjamas Content-Type: multipart/mixed; boundary="sl6hxqi4bcyV10hYxEcYmFjfB33PxDA5O" --sl6hxqi4bcyV10hYxEcYmFjfB33PxDA5O Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 05.02.20 17:48, Eric Blake wrote: > On 2/4/20 11:08 AM, Max Reitz wrote: >> After the series this patch belongs to, we want to have a common >> BdrvChildClass that encompasses all of child_file, child_format, and >> child_backing.=C2=A0 Such a single class needs a single .inherit_options= () >> implementation, and this patch introduces it. >> >> The next patch will show how the existing implementations can fall back >> to it just by passing appropriate BdrvChildRole and parent_is_format >> values. >> >> Signed-off-by: Max Reitz >> --- >> =C2=A0 block.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++= +++++ >> =C2=A0 1 file changed, 84 insertions(+) >> >=20 > No impact until the next patch, but the division of patches was wise. >=20 >=20 >> +=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0 * First, decide whether to set, clear, or leav= e BDRV_O_PROTOCOL. >> +=C2=A0=C2=A0=C2=A0=C2=A0 * Generally, the question to answer is: Should= this child be >> +=C2=A0=C2=A0=C2=A0=C2=A0 * format-probed by default? >> +=C2=A0=C2=A0=C2=A0=C2=A0 */ >> + >> +=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0 * Pure and non-filtered data children of non-f= ormat nodes should >> +=C2=A0=C2=A0=C2=A0=C2=A0 * be probed by default (even when the node its= elf has >> BDRV_O_PROTOCOL >> +=C2=A0=C2=A0=C2=A0=C2=A0 * set).=C2=A0 This only affects a very limited= set of drivers (namely >> +=C2=A0=C2=A0=C2=A0=C2=A0 * quorum and blkverify when this comment was w= ritten). >> +=C2=A0=C2=A0=C2=A0=C2=A0 * Force-clear BDRV_O_PROTOCOL then. >> +=C2=A0=C2=A0=C2=A0=C2=A0 */ >> +=C2=A0=C2=A0=C2=A0 if (!parent_is_format && >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 (role & (BDRV_CHILD_DATA | B= DRV_CHILD_METADATA | >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 BDRV_CHILD_FILTERED)) =3D=3D >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 BDRV= _CHILD_DATA) >> +=C2=A0=C2=A0=C2=A0 { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 flags &=3D ~BDRV_O_PROTOCOL; >> +=C2=A0=C2=A0=C2=A0 } >> + >> +=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0 * All children of format nodes (except for COW= children) and all >> +=C2=A0=C2=A0=C2=A0=C2=A0 * metadata children in general should never be= format-probed. >> +=C2=A0=C2=A0=C2=A0=C2=A0 * Force-set BDRV_O_PROTOCOL then. >> +=C2=A0=C2=A0=C2=A0=C2=A0 */ >> +=C2=A0=C2=A0=C2=A0 if ((parent_is_format && !(role & BDRV_CHILD_COW)) |= | >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 (role & BDRV_CHILD_METADATA)= ) >=20 > Should this use 'else if', to make it obvious that we never have a path > that both force-clears and force-sets BDRV_O_PROTOCOL?=C2=A0 But a carefu= l > reading shows that the two 'if' are mutually exclusive, even without the > second using 'else if'. It could or maybe even should, but that would make the comments more awkward to place. Locally, at some point I had two bools that were just set to the result of the conditions, and then I used them in an if/else if tree, but that wasn=E2=80=99t any less awkward. >> +=C2=A0=C2=A0=C2=A0 { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 flags |=3D BDRV_O_PROTOCOL; >> +=C2=A0=C2=A0=C2=A0 } >> + >=20 > Looks good!=C2=A0 Lots of decision trees, but also lots of good comments > backing up that complexity. OK :-) Max --sl6hxqi4bcyV10hYxEcYmFjfB33PxDA5O-- --ulKRRD1IDcEJC4gbtDg1dk6J23snjamas Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl478zoACgkQ9AfbAGHV z0C/lwgAw/S/DuWcehbIcX0MqWX44af3kqJ0+GgN9Wg+ztvDuvzwmHDZjssRTTMv C7KZxJzHLkvDfwJxhUwbyfPxDOaKaA3OKG1GfGoCWTLCVzFfTLZwSdQrXDpROj4W eLu8J0/EpeDOSohB7anhCVUVcsQ4C9BBuhKtgB0vbpXIULmsvfjj79Yx9CcnfHyr kw31p1KrRW9hj/4XT9KPKg+V0YzsFc7txuF6L/0MJ8o0HO74zqXPWNd3NS575Tj9 2utY6m3OZVnx++h6SPDwT6XqUiYgz4o/Lmuqe0AdI4SG07AYtKkmn7URzpy0pi2y Nv5TRYRlH7knTLrRL+IpViKepwjymA== =JQyp -----END PGP SIGNATURE----- --ulKRRD1IDcEJC4gbtDg1dk6J23snjamas--