From 2b678aa2f0990a25e15cdef66256a131566ecd2e Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Fri, 15 Oct 2021 08:40:53 -0300 Subject: 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: Liu Yi L Reviewed-by: Kevin Tian Reviewed-by: Christoph Hellwig Signed-off-by: Jason Gunthorpe Link: https://lore.kernel.org/r/4-v3-2fdfe4ca2cc6+18c-vfio_group_cdev_jgg@nvidia.com Signed-off-by: Alex Williamson --- drivers/vfio/vfio.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) (limited to 'drivers/vfio') diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 4abb2e5e1965..e313fa030b91 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -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; -- cgit v1.2.3