drm/vma_manage: Drop has_offset

It's racy, creating mmap offsets is a slowpath, so better to remove it
to avoid drivers doing broken things.

The only user is i915, and it's ok there because everything (well
almost) is protected by dev->struct_mutex in i915-gem.

While at it add a note in the create_mmap_offset kerneldoc that
drivers must release it again. And then I also noticed that
drm_gem_object_release entirely lacks kerneldoc.

Cc: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459330852-27668-14-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_gem.c

@@ -422,6 +422,10 @@ EXPORT_SYMBOL(drm_gem_handle_create);
  * @obj: obj in question
  *
  * This routine frees fake offsets allocated by drm_gem_create_mmap_offset().
+ *
+ * Note that drm_gem_object_release() already calls this function, so drivers
+ * don't have to take care of releasing the mmap offset themselves when freeing
+ * the GEM object.
  */
 void
 drm_gem_free_mmap_offset(struct drm_gem_object *obj)
@@ -445,6 +449,9 @@ EXPORT_SYMBOL(drm_gem_free_mmap_offset);
  * This routine allocates and attaches a fake offset for @obj, in cases where
  * the virtual size differs from the physical size (ie. obj->size).  Otherwise
  * just use drm_gem_create_mmap_offset().
+ *
+ * This function is idempotent and handles an already allocated mmap offset
+ * transparently. Drivers do not need to check for this case.
  */
 int
 drm_gem_create_mmap_offset_size(struct drm_gem_object *obj, size_t size)
@@ -466,6 +473,9 @@ EXPORT_SYMBOL(drm_gem_create_mmap_offset_size);
  * structures.
  *
  * This routine allocates and attaches a fake offset for @obj.
+ *
+ * Drivers can call drm_gem_free_mmap_offset() before freeing @obj to release
+ * the fake offset again.
  */
 int drm_gem_create_mmap_offset(struct drm_gem_object *obj)
 {
@@ -759,6 +769,13 @@ drm_gem_release(struct drm_device *dev, struct drm_file *file_private)
 	idr_destroy(&file_private->object_idr);
 }
 
+/**
+ * drm_gem_object_release - release GEM buffer object resources
+ * @obj: GEM buffer object
+ *
+ * This releases any structures and resources used by @obj and is the invers of
+ * drm_gem_object_init().
+ */
 void
 drm_gem_object_release(struct drm_gem_object *obj)
 {

drivers/gpu/drm/i915/i915_gem.c

@@ -2031,9 +2031,6 @@ static int i915_gem_object_create_mmap_offset(struct drm_i915_gem_object *obj)
 	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
 	int ret;
 
-	if (drm_vma_node_has_offset(&obj->base.vma_node))
-		return 0;
-
 	dev_priv->mm.shrinker_no_lock_stealing = true;
 
 	ret = drm_gem_create_mmap_offset(&obj->base);

include/drm/drm_vma_manager.h

@@ -175,19 +175,6 @@ static inline unsigned long drm_vma_node_size(struct drm_vma_offset_node *node)
 	return node->vm_node.size;
 }
 
-/**
- * drm_vma_node_has_offset() - Check whether node is added to offset manager
- * @node: Node to be checked
- *
- * RETURNS:
- * true iff the node was previously allocated an offset and added to
- * an vma offset manager.
- */
-static inline bool drm_vma_node_has_offset(struct drm_vma_offset_node *node)
-{
-	return drm_mm_node_allocated(&node->vm_node);
-}
-
 /**
  * drm_vma_node_offset_addr() - Return sanitized offset for user-space mmaps
  * @node: Linked offset node
@@ -220,7 +207,7 @@ static inline __u64 drm_vma_node_offset_addr(struct drm_vma_offset_node *node)
 static inline void drm_vma_node_unmap(struct drm_vma_offset_node *node,
 				      struct address_space *file_mapping)
 {
-	if (drm_vma_node_has_offset(node))
+	if (drm_mm_node_allocated(&node->vm_node))
 		unmap_mapping_range(file_mapping,
 				    drm_vma_node_offset_addr(node),
 				    drm_vma_node_size(node) << PAGE_SHIFT, 1);