iommufd: Move putting a hwpt to a helper function

Next patch will need to call this from two places.

Link: https://lore.kernel.org/r/8-v8-6659224517ea+532-iommufd_alloc_jgg@nvidia.comReviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/device.c

@@ -526,11 +526,7 @@ void iommufd_device_detach(struct iommufd_device *idev)
 	struct iommufd_hw_pagetable *hwpt;
 
 	hwpt = iommufd_hw_pagetable_detach(idev);
-	if (hwpt->auto_domain)
-		iommufd_object_destroy_user(idev->ictx, &hwpt->obj);
-	else
-		refcount_dec(&hwpt->obj.users);
-
+	iommufd_hw_pagetable_put(idev->ictx, hwpt);
 	refcount_dec(&idev->obj.users);
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD);

drivers/iommu/iommufd/iommufd_private.h

@@ -260,6 +260,16 @@ struct iommufd_hw_pagetable *
 iommufd_hw_pagetable_detach(struct iommufd_device *idev);
 void iommufd_hw_pagetable_destroy(struct iommufd_object *obj);
 
+static inline void iommufd_hw_pagetable_put(struct iommufd_ctx *ictx,
+					    struct iommufd_hw_pagetable *hwpt)
+{
+	lockdep_assert_not_held(&hwpt->ioas->mutex);
+	if (hwpt->auto_domain)
+		iommufd_object_destroy_user(ictx, &hwpt->obj);
+	else
+		refcount_dec(&hwpt->obj.users);
+}
+
 struct iommufd_group {
 	struct kref ref;
 	struct mutex lock;