drm/gem/shmem: Extract drm_gem_shmem_release() from drm_gem_shmem_free()

At the moment, the way that we currently free gem shmem objects is not
ideal for rust bindings. drm_gem_shmem_free() releases all of the
associated memory with a gem shmem object with kfree(), which means that
for us to correctly release a gem shmem object in rust we have to manually
drop all of the contents of our gem object structure in-place by hand
before finally calling drm_gem_shmem_free() to release the shmem resources
and the allocation for the gem object.

Since the only reason this is an issue is because of drm_gem_shmem_free()
calling kfree(), we can fix this by splitting drm_gem_shmem_free() out into
itself and drm_gem_shmem_release(), where drm_gem_shmem_release() releases
the various gem shmem resources without freeing the structure itself. With
this, we can safely re-acquire the KBox for the gem object's memory
allocation and let rust handle cleaning up all of the other struct members
automatically.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250911230147.650077-3-lyude@redhat.com

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index b20a7b75c722888ed9f2e1c0d106b8d9b7e9b45b..50594cf8e17cc7cdad6b1de75d839d4e981a98b5 100644 (file)
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -175,13 +175,13 @@ struct drm_gem_shmem_object *drm_gem_shmem_create_with_mnt(struct drm_device *de
 EXPORT_SYMBOL_GPL(drm_gem_shmem_create_with_mnt);
 
 /**
- * drm_gem_shmem_free - Free resources associated with a shmem GEM object
- * @shmem: shmem GEM object to free
+ * drm_gem_shmem_release - Release resources associated with a shmem GEM object.
+ * @shmem: shmem GEM object
  *
- * This function cleans up the GEM object state and frees the memory used to
- * store the object itself.
+ * This function cleans up the GEM object state, but does not free the memory used to store the
+ * object itself. This function is meant to be a dedicated helper for the Rust GEM bindings.
  */
-void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
+void drm_gem_shmem_release(struct drm_gem_shmem_object *shmem)
 {
        struct drm_gem_object *obj = &shmem->base;
 
@@ -208,6 +208,19 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
        }
 
        drm_gem_object_release(obj);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_release);
+
+/**
+ * drm_gem_shmem_free - Free resources associated with a shmem GEM object
+ * @shmem: shmem GEM object to free
+ *
+ * This function cleans up the GEM object state and frees the memory used to
+ * store the object itself.
+ */
+void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
+{
+       drm_gem_shmem_release(shmem);
        kfree(shmem);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_free);

diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index 235dc33127b9a8dba5e83a54f02e167521fd8b89..589f7bfe7506ebb7b41afa4b77182c9ac49d1f17 100644 (file)
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -112,6 +112,7 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t
 struct drm_gem_shmem_object *drm_gem_shmem_create_with_mnt(struct drm_device *dev,
                                                           size_t size,
                                                           struct vfsmount *gemfs);
+void drm_gem_shmem_release(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem);
 
 void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem);