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Tue, 27 Aug 2019 16:13:28 +0000 From: Parav Pandit To: Alex Williamson , Cornelia Huck CC: Jiri Pirko , "kwankhede@nvidia.com" , "davem@davemloft.net" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" Subject: RE: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs Thread-Topic: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs Thread-Index: AQHVXE627FcLaFBgXUa8jSc95m92WKcOy/4AgAAKv2CAAAYaAIAAQtGAgAAMQNA= Date: Tue, 27 Aug 2019 16:13:27 +0000 Message-ID: References: <20190826204119.54386-1-parav@mellanox.com> <20190826204119.54386-3-parav@mellanox.com> <20190827122928.752e763b.cohuck@redhat.com> <20190827132946.0b92d259.cohuck@redhat.com> <20190827092855.29702347@x1.home> In-Reply-To: <20190827092855.29702347@x1.home> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=parav@mellanox.com; x-originating-ip: [106.51.18.188] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 11d33b6d-5616-4e8b-ef79-08d72b097f41 x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(5600166)(711020)(4605104)(1401327)(4618075)(4534185)(7168020)(4627221)(201703031133081)(201702281549075)(8990200)(2017052603328)(7193020);SRVR:AM0PR05MB5859; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: 11d33b6d-5616-4e8b-ef79-08d72b097f41 X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Aug 2019 16:13:28.2843 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Jo4GlrF7z6EYVqMeramNFCgWIC9iGwOT7/GrlVFp0AoIXAvOsxNFA82bQgR+/mNaFXWG2vlF4Ogpr53Slbu30Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR05MB5859 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > -----Original Message----- > From: Alex Williamson > Sent: Tuesday, August 27, 2019 8:59 PM > To: Cornelia Huck > Cc: Parav Pandit ; Jiri Pirko ; > kwankhede@nvidia.com; davem@davemloft.net; kvm@vger.kernel.org; linux- > kernel@vger.kernel.org; netdev@vger.kernel.org > Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all mdevs >=20 > On Tue, 27 Aug 2019 13:29:46 +0200 > Cornelia Huck wrote: >=20 > > On Tue, 27 Aug 2019 11:08:59 +0000 > > Parav Pandit wrote: > > > > > > -----Original Message----- > > > > From: Cornelia Huck > > > > Sent: Tuesday, August 27, 2019 3:59 PM > > > > To: Parav Pandit > > > > Cc: alex.williamson@redhat.com; Jiri Pirko ; > > > > kwankhede@nvidia.com; davem@davemloft.net; kvm@vger.kernel.org; > > > > linux- kernel@vger.kernel.org; netdev@vger.kernel.org > > > > Subject: Re: [PATCH 2/4] mdev: Make mdev alias unique among all > > > > mdevs > > > > > > > > On Mon, 26 Aug 2019 15:41:17 -0500 Parav Pandit > > > > wrote: > > > > > > > > > Mdev alias should be unique among all the mdevs, so that when > > > > > such alias is used by the mdev users to derive other objects, > > > > > there is no collision in a given system. > > > > > > > > > > Signed-off-by: Parav Pandit > > > > > --- > > > > > drivers/vfio/mdev/mdev_core.c | 5 +++++ > > > > > 1 file changed, 5 insertions(+) > > > > > > > > > > diff --git a/drivers/vfio/mdev/mdev_core.c > > > > > b/drivers/vfio/mdev/mdev_core.c index e825ff38b037..6eb37f0c6369 > > > > > 100644 > > > > > --- a/drivers/vfio/mdev/mdev_core.c > > > > > +++ b/drivers/vfio/mdev/mdev_core.c > > > > > @@ -375,6 +375,11 @@ int mdev_device_create(struct kobject *kobj, > struct > > > > device *dev, > > > > > ret =3D -EEXIST; > > > > > goto mdev_fail; > > > > > } > > > > > + if (tmp->alias && strcmp(tmp->alias, alias) =3D=3D 0) { > > > > > > > > Any way we can relay to the caller that the uuid was fine, but > > > > that we had a hash collision? Duplicate uuids are much more obvious= than > a collision here. > > > > > > > How do you want to relay this rare event? > > > Netlink interface has way to return the error message back, but sysfs= is > limited due to its error code based interface. > > > > I don't know, that's why I asked :) > > > > The problem is that "uuid already used" and "hash collision" are > > indistinguishable. While "use a different uuid" will probably work in > > both cases, "increase alias length" might be a good alternative in > > some cases. > > > > But if there is no good way to relay the problem, we can live with it. >=20 > It's a rare event, maybe just dev_dbg(dev, "Hash collision creating alias= \"%s\" > for mdev device %pUl\n",... >=20 Ok. dev_dbg_once() to avoid message flood. > Thanks, > Alex >=20 > > > > > + mutex_unlock(&mdev_list_lock); > > > > > + ret =3D -EEXIST; > > > > > + goto mdev_fail; > > > > > + } > > > > > } > > > > > > > > > > mdev =3D kzalloc(sizeof(*mdev), GFP_KERNEL); > > > > >