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

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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: Liu Yi L <yi.l.liu@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/4-v3-2fdfe4ca2cc6+18c-vfio_group_cdev_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Jason Gunthorpe 2021-10-15 08:40:53 -03:00 committed by Alex Williamson
parent 325a31c920
commit 2b678aa2f0
1 changed files with 9 additions and 12 deletions
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21
drivers/vfio/vfio.c
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@ -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;