linux-kernel - Re: [PATCH v1 2/5] mdev: Make mdev alias unique among all mdevs

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Message-ID: <20190828153652.7eb6d6d6@x1.home>
Date:   Wed, 28 Aug 2019 15:36:52 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Parav Pandit <parav@...lanox.com>
Cc:     jiri@...lanox.com, kwankhede@...dia.com, cohuck@...hat.com,
        davem@...emloft.net, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v1 2/5] mdev: Make mdev alias unique among all mdevs

On Tue, 27 Aug 2019 14:16:51 -0500
Parav Pandit <parav@...lanox.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 <parav@...lanox.com>
> 
> ---
> Changelog:
> v0->v1:
>  - Fixed inclusiong of alias for NULL check
>  - Added ratelimited debug print for sha1 hash collision error
> ---
>  drivers/vfio/mdev/mdev_core.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index 62d29f57fe0c..4b9899e40665 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -375,6 +375,13 @@ int mdev_device_create(struct kobject *kobj, struct device *dev,
>  			ret = -EEXIST;
>  			goto mdev_fail;
>  		}
> +		if (tmp->alias && alias && strcmp(tmp->alias, alias) == 0) {

Nit, test if the device we adding has an alias before the device we're
testing against.  The compiler can better optimize keeping alias hot.
Thanks,

Alex

> +			mutex_unlock(&mdev_list_lock);
> +			ret = -EEXIST;
> +			dev_dbg_ratelimited(dev, "Hash collision in alias creation for UUID %pUl\n",
> +					    uuid);
> +			goto mdev_fail;
> +		}
>  	}
>  
>  	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);