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Mon, 17 Aug 2020 11:41:46 +0000 (UTC) Subject: Re: [RFC PATCH 07/22] block/export: Remove magic from block-export-add To: Kevin Wolf , qemu-block@nongnu.org References: <20200813162935.210070-1-kwolf@redhat.com> <20200813162935.210070-8-kwolf@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: <2a6528d8-1792-ec1e-287b-a9b9e2f20eef@redhat.com> Date: Mon, 17 Aug 2020 13:41:45 +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: <20200813162935.210070-8-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="cfLlZpKZTqquCFIvt4X6DJPcVxFPTbRNS" Received-SPF: pass client-ip=205.139.110.61; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/17 05:03:47 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=ham 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: 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) --cfLlZpKZTqquCFIvt4X6DJPcVxFPTbRNS Content-Type: multipart/mixed; boundary="cjXCyBvClO6CdwHjdHkDEG2BwUwzuu3jO" --cjXCyBvClO6CdwHjdHkDEG2BwUwzuu3jO Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 13.08.20 18:29, Kevin Wolf wrote: > nbd-server-add tries to be convenient and adds two questionable > features that we don't want to share in block-export-add, even for NBD > exports: >=20 > 1. When requesting a writable export of a read-only device, the export > is silently downgraded to read-only. This should be an error in the > context of block-export-add. >=20 > 2. When using a BlockBackend name, unplugging the device from the guest > will automatically stop the NBD server, too. This may sometimes be > what you want, but it could also be very surprising. Let's keep > things explicit with block-export-add. If the user wants to stop the > export, they should tell us so. >=20 > Move these things into the nbd-server-add QMP command handler so that > they apply only there. >=20 > Signed-off-by: Kevin Wolf > --- > include/block/nbd.h | 3 ++- > block/export/export.c | 44 ++++++++++++++++++++++++++++++++++++++----- > blockdev-nbd.c | 10 ++++------ > nbd/server.c | 19 ++++++++++++------- > qemu-nbd.c | 3 +-- > 5 files changed, 58 insertions(+), 21 deletions(-) [...] > diff --git a/block/export/export.c b/block/export/export.c > index 3d0dacb3f2..2d5f92861c 100644 > --- a/block/export/export.c > +++ b/block/export/export.c [...] > @@ -34,24 +36,56 @@ static const BlockExportDriver *blk_exp_find_driver(B= lockExportType type) > return NULL; > } > =20 > -void qmp_block_export_add(BlockExportOptions *export, Error **errp) > +static BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp= ) > { > const BlockExportDriver *drv; > =20 > drv =3D blk_exp_find_driver(export->type); > if (!drv) { > error_setg(errp, "No driver found for the requested export type"= ); > - return; > + return NULL; > } > =20 > - drv->create(export, errp); > + return drv->create(export, errp); > +} > + > +void qmp_block_export_add(BlockExportOptions *export, Error **errp) > +{ > + blk_exp_add(export, errp); > } Interesting. I would have added it this way from the start then (with a note that we=E2=80=99ll need it later). > void qmp_nbd_server_add(BlockExportOptionsNbd *arg, Error **errp) > { > - BlockExportOptions export =3D { > + BlockExport *export; > + BlockDriverState *bs; > + BlockBackend *on_eject_blk; > + > + BlockExportOptions export_opts =3D { > .type =3D BLOCK_EXPORT_TYPE_NBD, > .u.nbd =3D *arg, This copies *arg=E2=80=99s contents... > }; > - qmp_block_export_add(&export, errp); > + > + /* > + * nbd-server-add doesn't complain when a read-only device should be > + * exported as writable, but simply downgrades it. This is an error = with > + * block-export-add. > + */ > + bs =3D bdrv_lookup_bs(arg->device, arg->device, NULL); > + if (bs && bdrv_is_read_only(bs)) { > + arg->writable =3D false; ...and here you only modify the original *arg, but not export_opts.u.nbd. So I don=E2=80=99t think this will have any effect. > + } > + > + export =3D blk_exp_add(&export_opts, errp); > + if (!export) { > + return; > + } > + > + /* > + * nbd-server-add removes the export when the named BlockBackend use= d for > + * @device goes away. > + */ > + on_eject_blk =3D blk_by_name(arg->device); > + if (on_eject_blk) { > + nbd_export_set_on_eject_blk(export, on_eject_blk); > + } > } The longer it gets, the more I think maybe it should be in some NBD file like blockdev-nbd.c after all. [...] > diff --git a/nbd/server.c b/nbd/server.c > index 92360d1f08..0b84fd30e2 100644 > --- a/nbd/server.c > +++ b/nbd/server.c > @@ -1506,11 +1506,22 @@ static void nbd_eject_notifier(Notifier *n, void = *data) > aio_context_release(aio_context); > } > =20 > +void nbd_export_set_on_eject_blk(BlockExport *exp, BlockBackend *blk) > +{ > + NBDExport *nbd_exp =3D container_of(exp, NBDExport, common); > + assert(exp->drv =3D=3D &blk_exp_nbd); > + I think asserting that the nbd_exp->eject_notifier is unused so far would make sense (e.g. just checking that eject_notifier_blk is NULL). Max > + blk_ref(blk); > + nbd_exp->eject_notifier_blk =3D blk; > + nbd_exp->eject_notifier.notify =3D nbd_eject_notifier; > + blk_add_remove_bs_notifier(blk, &nbd_exp->eject_notifier); > +} > + --cjXCyBvClO6CdwHjdHkDEG2BwUwzuu3jO-- --cfLlZpKZTqquCFIvt4X6DJPcVxFPTbRNS Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl86bPkACgkQ9AfbAGHV z0Do1wf/TCM4XY2djVhyLOLsF6csyyzeRnGwvnOk+kym078jLLJwLJOUKRLfW9i8 wvoxjqjRb/xmap+XsL8yTGVbSHwUMWgTBgb0MRFnaTffDkDLsLv3tMrmFHzNA9oR sEGidZdCKJ5hMb2luGXqKYI6+o0qUtANbkWmp9HGyQr3D/xp+Yu0fhDYa4mhI8QP u5eysoHGi721YMx9TZxdMrVM/kFzyMydHMKn2DNLEXJcYwKxI+j4tR6p+XJHrT0R Zcalr1GtOk9PRAPWejjHksy9+McdgdDolP61MrwDk7JB90bLA6Y815MhZFpsgy8J Gr6wJ6lZHAmX8pQKWOtDbhtUG51Umg== =+qWQ -----END PGP SIGNATURE----- --cfLlZpKZTqquCFIvt4X6DJPcVxFPTbRNS--