linux-kernel - Re: [PATCH 1/1] vfio: put off the allocation of "minor" in vfio_create

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Date:	Mon, 16 Mar 2015 16:00:16 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Zhen Lei <thunder.leizhen@...wei.com>
Cc:	KVM <kvm@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Zefan Li <lizefan@...wei.com>, Xinwei Hu <huxinwei@...wei.com>,
	Tianhong Ding <dingtianhong@...wei.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH 1/1] vfio: put off the allocation of "minor" in
 vfio_create_group

On Thu, 2014-11-20 at 19:25 +0800, Zhen Lei wrote:
> The next code fragment "list_for_each_entry" is not depend on "minor". With this
> patch, the free of "minor" in "list_for_each_entry" can be reduced, and there is
> no functional change.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  drivers/vfio/vfio.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index f018d8d..737eb468 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -225,22 +225,21 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
> 
>  	mutex_lock(&vfio.group_lock);
> 
> -	minor = vfio_alloc_group_minor(group);
> -	if (minor < 0) {
> -		vfio_group_unlock_and_free(group);
> -		return ERR_PTR(minor);
> -	}
> -
>  	/* Did we race creating this group? */
>  	list_for_each_entry(tmp, &vfio.group_list, vfio_next) {
>  		if (tmp->iommu_group == iommu_group) {
>  			vfio_group_get(tmp);
> -			vfio_free_group_minor(minor);
>  			vfio_group_unlock_and_free(group);
>  			return tmp;
>  		}
>  	}
> 
> +	minor = vfio_alloc_group_minor(group);
> +	if (minor < 0) {
> +		vfio_group_unlock_and_free(group);
> +		return ERR_PTR(minor);
> +	}
> +
>  	dev = device_create(vfio.class, NULL,
>  			    MKDEV(MAJOR(vfio.group_devt), minor),
>  			    group, "%d", iommu_group_id(iommu_group));

Applied to next for v4.1.  Sorry I didn't put this in earlier, it got
lost in my inbox.  Thanks,

Alex

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