On Tue, 27 Aug 2019 13:29:46 +0200
Cornelia Huck <coh...@redhat.com> wrote:
> On Tue, 27 Aug 2019 11:08:59 +0000
> Parav Pandit <pa...@mellanox.com> wrote:
>
> > > -----Original Message-----
> > > From: Cornelia Huck <coh...@redhat.com>
> > > Sent: Tuesday, August 27, 2019 3:59 PM
> > > To: Parav Pandit <pa...@mellanox.com>
> > > Cc: alex.william...@redhat.com; Jiri Pirko <j...@mellanox.com>;
> > > kwankh...@nvidia.com; da...@davemloft.net; k...@vger.kernel.org; linux-
> > > ker...@vger.kernel.org; net...@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 <pa...@mellanox.com> 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 <pa...@mellanox.com>
> > > > ---
> > > > 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 = -EEXIST;
> > > > goto mdev_fail;
> > > > }
> > > > + if (tmp->alias && strcmp(tmp->alias, alias) == 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.
It's a rare event, maybe just dev_dbg(dev, "Hash collision creating alias
\"%s\" for mdev device %pUl\n",...
Thanks,
Alex
> > > > + mutex_unlock(&mdev_list_lock);
> > > > + ret = -EEXIST;
> > > > + goto mdev_fail;
> > > > + }
> > > > }
> > > >
> > > > mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
> >
>
