Commit 2b678aa2 authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Alex Williamson
Browse files

vfio: Use a refcount_t instead of a kref in the vfio_group 



The next patch adds a struct device to the struct vfio_group, and it is
confusing/bad practice to have two krefs in the same struct. This kref is
controlling the period when the vfio_group is registered in sysfs, and
visible in the internal lookup. Switch it to a refcount_t instead.

The refcount_dec_and_mutex_lock() is still required because we need
atomicity of the list searches and sysfs presence.

Reviewed-by: default avatarLiu Yi L <yi.l.liu@intel.com>
Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/4-v3-2fdfe4ca2cc6+18c-vfio_group_cdev_jgg@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 325a31c9

drivers/vfio/vfio.c

+9 −12
Original line number Diff line number Diff line
@@ -69,7 +69,7 @@ struct vfio_unbound_dev { 
};



struct vfio_group {

	struct kref			kref;

	refcount_t			users;

	int				minor;

	atomic_t			container_users;

	struct iommu_group		*iommu_group;
@@ -377,7 +377,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group, 
	if (!group)

		return ERR_PTR(-ENOMEM);



	kref_init(&group->kref);

	refcount_set(&group->users, 1);

	INIT_LIST_HEAD(&group->device_list);

	mutex_init(&group->device_lock);

	INIT_LIST_HEAD(&group->unbound_list);
@@ -433,10 +433,10 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group, 
	return group;

}



/* called with vfio.group_lock held */

static void vfio_group_release(struct kref *kref)

static void vfio_group_put(struct vfio_group *group)

{

	struct vfio_group *group = container_of(kref, struct vfio_group, kref);

	if (!refcount_dec_and_mutex_lock(&group->users, &vfio.group_lock))

		return;



	/*

	 * These data structures all have paired operations that can only be
@@ -454,15 +454,9 @@ static void vfio_group_release(struct kref *kref) 
	vfio_group_unlock_and_free(group);

}



static void vfio_group_put(struct vfio_group *group)

{

	kref_put_mutex(&group->kref, vfio_group_release, &vfio.group_lock);

}



/* Assume group_lock or group reference is held */

static void vfio_group_get(struct vfio_group *group)

{

	kref_get(&group->kref);

	refcount_inc(&group->users);

}



static struct vfio_group *vfio_group_get_from_minor(int minor)
@@ -1657,6 +1651,9 @@ struct vfio_group *vfio_group_get_external_user(struct file *filep) 
	if (ret)

		return ERR_PTR(ret);



	/*

	 * Since the caller holds the fget on the file group->users must be >= 1

	 */

	vfio_group_get(group);



	return group;