vfio: convert to idr_alloc()

Convert to the much saner new idr interface.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/vfio/vfio.c

@@ -139,23 +139,8 @@ EXPORT_SYMBOL_GPL(vfio_unregister_iommu_driver);
  */
 static int vfio_alloc_group_minor(struct vfio_group *group)
 {
-	int ret, minor;
-
-again:
-	if (unlikely(idr_pre_get(&vfio.group_idr, GFP_KERNEL) == 0))
-		return -ENOMEM;
-
 	/* index 0 is used by /dev/vfio/vfio */
-	ret = idr_get_new_above(&vfio.group_idr, group, 1, &minor);
-	if (ret == -EAGAIN)
-		goto again;
-	if (ret || minor > MINORMASK) {
-		if (minor > MINORMASK)
-			idr_remove(&vfio.group_idr, minor);
-		return -ENOSPC;
-	}
-
-	return minor;
+	return idr_alloc(&vfio.group_idr, group, 1, MINORMASK + 1, GFP_KERNEL);
 }
 
 static void vfio_free_group_minor(int minor)