Re: [PATCH 1/2] drm/drm_vma_manager: Add drm_vma_node_allow_once()

"Das, Nirmoy" <nirmoy.das@xxxxxxxxxxxxxxx> · Wed, 18 Jan 2023 10:45:19 +0100

On 1/18/2023 10:38 AM, Andi Shyti wrote:
On Tue, Jan 17, 2023 at 06:52:35PM +0100, Nirmoy Das wrote:
Currently there is no easy way for a drm driver to safely check and allow
drm_vma_offset_node for a drm file just once. Allow drm drivers to call
non-refcounted version of drm_vma_node_allow() so that a driver doesn't
need to keep track of each drm_vma_node_allow() to call subsequent
drm_vma_node_revoke() to prevent memory leak.

Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>

Next time, please, don't leave any spaces between tags.


I will keep that in my mind.


Suggested-by: Chris Wilson <chris.p.wilson@xxxxxxxxx>
Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>


Thanks,

Nirmoy


Thanks,
Andi

---
  drivers/gpu/drm/drm_vma_manager.c | 76 ++++++++++++++++++++++---------
  include/drm/drm_vma_manager.h     |  1 +
  2 files changed, 55 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/drm_vma_manager.c b/drivers/gpu/drm/drm_vma_manager.c
index 7de37f8c68fd..83229a031af0 100644
--- a/drivers/gpu/drm/drm_vma_manager.c
+++ b/drivers/gpu/drm/drm_vma_manager.c
@@ -240,27 +240,8 @@ void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
  }
  EXPORT_SYMBOL(drm_vma_offset_remove);
  
-/**
- * drm_vma_node_allow - Add open-file to list of allowed users
- * @node: Node to modify
- * @tag: Tag of file to remove
- *
- * Add @tag to the list of allowed open-files for this node. If @tag is
- * already on this list, the ref-count is incremented.
- *
- * The list of allowed-users is preserved across drm_vma_offset_add() and
- * drm_vma_offset_remove() calls. You may even call it if the node is currently
- * not added to any offset-manager.
- *
- * You must remove all open-files the same number of times as you added them
- * before destroying the node. Otherwise, you will leak memory.
- *
- * This is locked against concurrent access internally.
- *
- * RETURNS:
- * 0 on success, negative error code on internal failure (out-of-mem)
- */
-int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
+static int vma_node_allow(struct drm_vma_offset_node *node,
+			  struct drm_file *tag, bool ref_counted)
  {
  	struct rb_node **iter;
  	struct rb_node *parent = NULL;
@@ -282,7 +263,8 @@ int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
  		entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
  
  		if (tag == entry->vm_tag) {
-			entry->vm_count++;
+			if (ref_counted)
+				entry->vm_count++;
  			goto unlock;
  		} else if (tag > entry->vm_tag) {
  			iter = &(*iter)->rb_right;
@@ -307,8 +289,58 @@ int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
  	kfree(new);
  	return ret;
  }
+
+/**
+ * drm_vma_node_allow - Add open-file to list of allowed users
+ * @node: Node to modify
+ * @tag: Tag of file to remove
+ *
+ * Add @tag to the list of allowed open-files for this node. If @tag is
+ * already on this list, the ref-count is incremented.
+ *
+ * The list of allowed-users is preserved across drm_vma_offset_add() and
+ * drm_vma_offset_remove() calls. You may even call it if the node is currently
+ * not added to any offset-manager.
+ *
+ * You must remove all open-files the same number of times as you added them
+ * before destroying the node. Otherwise, you will leak memory.
+ *
+ * This is locked against concurrent access internally.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on internal failure (out-of-mem)
+ */
+int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
+{
+	return vma_node_allow(node, tag, true);
+}
  EXPORT_SYMBOL(drm_vma_node_allow);
  
+/**
+ * drm_vma_node_allow_once - Add open-file to list of allowed users
+ * @node: Node to modify
+ * @tag: Tag of file to remove
+ *
+ * Add @tag to the list of allowed open-files for this node.
+ *
+ * The list of allowed-users is preserved across drm_vma_offset_add() and
+ * drm_vma_offset_remove() calls. You may even call it if the node is currently
+ * not added to any offset-manager.
+ *
+ * This is not ref-counted unlike drm_vma_node_allow() hence drm_vma_node_revoke()
+ * should only be called once after this.
+ *
+ * This is locked against concurrent access internally.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on internal failure (out-of-mem)
+ */
+int drm_vma_node_allow_once(struct drm_vma_offset_node *node, struct drm_file *tag)
+{
+	return vma_node_allow(node, tag, false);
+}
+EXPORT_SYMBOL(drm_vma_node_allow_once);
+
  /**
   * drm_vma_node_revoke - Remove open-file from list of allowed users
   * @node: Node to modify
diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h
index 4f8c35206f7c..6c2a2f21dbf0 100644
--- a/include/drm/drm_vma_manager.h
+++ b/include/drm/drm_vma_manager.h
@@ -74,6 +74,7 @@ void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
  			   struct drm_vma_offset_node *node);
  
  int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag);
+int drm_vma_node_allow_once(struct drm_vma_offset_node *node, struct drm_file *tag);
  void drm_vma_node_revoke(struct drm_vma_offset_node *node,
  			 struct drm_file *tag);
  bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
--
2.39.0






