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Mon, 17 Aug 2020 12:49:52 +0000 (UTC) Date: Mon, 17 Aug 2020 14:49:51 +0200 From: Kevin Wolf To: Max Reitz Subject: Re: [RFC PATCH 07/22] block/export: Remove magic from block-export-add Message-ID: <20200817124951.GJ11402@linux.fritz.box> References: <20200813162935.210070-1-kwolf@redhat.com> <20200813162935.210070-8-kwolf@redhat.com> <2a6528d8-1792-ec1e-287b-a9b9e2f20eef@redhat.com> MIME-Version: 1.0 In-Reply-To: <2a6528d8-1792-ec1e-287b-a9b9e2f20eef@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@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="ADZbWkCsHQ7r3kzd" Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=kwolf@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=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: qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --ADZbWkCsHQ7r3kzd Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Am 17.08.2020 um 13:41 hat Max Reitz geschrieben: > 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(-) >=20 > [...] >=20 > > 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 >=20 > [...] >=20 > > @@ -34,24 +36,56 @@ static const BlockExportDriver *blk_exp_find_driver= (BlockExportType type) > > return NULL; > > } > > =20 > > -void qmp_block_export_add(BlockExportOptions *export, Error **errp) > > +static BlockExport *blk_exp_add(BlockExportOptions *export, Error **er= rp) > > { > > const BlockExportDriver *drv; > > =20 > > drv =3D blk_exp_find_driver(export->type); > > if (!drv) { > > error_setg(errp, "No driver found for the requested export typ= e"); > > - 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); > > } >=20 > Interesting. I would have added it this way from the start then (with a > note that we=E2=80=99ll need it later). >=20 > > 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, >=20 > This copies *arg=E2=80=99s contents... >=20 > > }; > > - 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 erro= r 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; >=20 > ...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. I thought I had tested this... Well, good catch, thanks. > > + } > > + > > + export =3D blk_exp_add(&export_opts, errp); > > + if (!export) { > > + return; > > + } > > + > > + /* > > + * nbd-server-add removes the export when the named BlockBackend u= sed 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); > > + } > > } >=20 > The longer it gets, the more I think maybe it should be in some NBD file > like blockdev-nbd.c after all. Fair enough. Though I think blockdev-nbd.c in the root directory is something that shouldn't even exist. But I guess I can just leave the functions where they are and we can move the file another day. > [...] >=20 > > 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, voi= d *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); > > + >=20 > 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). Makes sense. 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