[PATCH v3 08/14] drm/gem/shmem: Extract drm_gem_shmem_release() from drm_gem_shmem_free()

[Lyude Paul]

At the moment the way that freeing 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 <ly...@redhat.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 23 ++++++++++++++++++-----
 include/drm/drm_gem_shmem_helper.h     |  1 +
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c 
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index b20a7b75c7228..50594cf8e17cc 100644
--- 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 235dc33127b9a..589f7bfe7506e 100644
--- 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);
-- 
2.50.0