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Thu, 16 Jul 2020 14:46:04 +0000 (UTC) Subject: Re: [PATCH v7 01/47] block: Add child access functions To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20200625152215.941773-1-mreitz@redhat.com> <20200625152215.941773-2-mreitz@redhat.com> <12e568be-f931-fc16-0ca2-a7ec54e538ea@virtuozzo.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: <6a40dbf6-5756-8483-680b-23916a6a962b@redhat.com> Date: Thu, 16 Jul 2020 16:46:03 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <12e568be-f931-fc16-0ca2-a7ec54e538ea@virtuozzo.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="fZr1TwGfLawxLkZabN9s0YGCnkQNZhFww" Received-SPF: pass client-ip=205.139.110.120; envelope-from=mreitz@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/15 19:36:06 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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 , 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) --fZr1TwGfLawxLkZabN9s0YGCnkQNZhFww Content-Type: multipart/mixed; boundary="agDegy1On7lw5PhEzEALwnIQ4t4qjedoZ" --agDegy1On7lw5PhEzEALwnIQ4t4qjedoZ Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 13.07.20 11:06, Vladimir Sementsov-Ogievskiy wrote: > 25.06.2020 18:21, Max Reitz wrote: >> There are BDS children that the general block layer code can access, >> namely bs->file and bs->backing.=C2=A0 Since the introduction of filters= and >> external data files, their meaning is not quite clear.=C2=A0 bs->backing= can >> be a COW source, or it can be a filtered child; bs->file can be a >> filtered child, it can be data and metadata storage, or it can be just >> metadata storage. >> >> This overloading really is not helpful.=C2=A0 This patch adds functions = that >> retrieve the correct child for each exact purpose.=C2=A0 Later patches i= n >> this series will make use of them.=C2=A0 Doing so will allow us to handl= e >> filter nodes in a meaningful way. >> >> Signed-off-by: Max Reitz >> --- >=20 > [..] >=20 >> +/* >> + * Return the primary child of this node: For filters, that is the >> + * filtered child.=C2=A0 For other nodes, that is usually the child sto= ring >> + * metadata. >> + * (A generally more helpful description is that this is (usually) the >> + * child that has the same filename as @bs.) >> + * >> + * Drivers do not necessarily have a primary child; for example quorum >> + * does not. >> + */ >> +BdrvChild *bdrv_primary_child(BlockDriverState *bs) >> +{ >> +=C2=A0=C2=A0=C2=A0 BdrvChild *c; >> + >> +=C2=A0=C2=A0=C2=A0 QLIST_FOREACH(c, &bs->children, next) { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (c->role & BDRV_CHILD_PRI= MARY) { >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 retu= rn c; >> +=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 return NULL; >> +} >> >=20 > Suggest squash-in to also assert that not more than one primary child: > --- a/block.c > +++ b/block.c > @@ -6998,13 +6998,14 @@ BdrvChild > *bdrv_filter_or_cow_child(BlockDriverState *bs) > =C2=A0 */ > =C2=A0BdrvChild *bdrv_primary_child(BlockDriverState *bs) > =C2=A0{ > -=C2=A0=C2=A0=C2=A0 BdrvChild *c; > +=C2=A0=C2=A0=C2=A0 BdrvChild *c, *found =3D NULL; > =C2=A0 > =C2=A0=C2=A0=C2=A0=C2=A0 QLIST_FOREACH(c, &bs->children, next) { > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (c->role & BDRV_CHILD= _PRIMARY) { > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 retur= n c; > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 asser= t(!found); Hm, why not. > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 found= =3D c; > =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 return NULL; > +=C2=A0=C2=A0=C2=A0 return c; > =C2=A0} >=20 >=20 > with or without: > Reviewed-by: Vladimir Sementsov-Ogievskiy In any case, thanks for reviewing! Max --agDegy1On7lw5PhEzEALwnIQ4t4qjedoZ-- --fZr1TwGfLawxLkZabN9s0YGCnkQNZhFww Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl8QaCsACgkQ9AfbAGHV z0BbQwf+Prf2dHfnnpHeHpvU9TxshsvIw4u89cyi8q+D208LAEYPFnpNxCPiBfQP zkkzWYRdb0yP21s8fZ874lX4yZ+z0dVU0wTYRJ2SRUOrGhrTbcLVqhmXAaTzX3Jr BBQTgZ2SB1jUZOVQBDWpepUsZbE+9FLbvlApowchT8Eee7Sf9VbdwuU0i1aGKI9L LX4wHnt4dxqKyNZMxmDKSeVwrSv/LOf3k0w7K9NKNPoa+Zi5wBiJe8YEkePUivOn Xw5ZPtlDPg4H2aLz03320t5eYRF00IFelSh5JTk9gCqKySU+OZb21p4j0qFsPobz ajM63uJDv1fUfZyDfW90WWQOVlHpeA== =MWap -----END PGP SIGNATURE----- --fZr1TwGfLawxLkZabN9s0YGCnkQNZhFww--