Commit c08c9310 authored by Lyude Paul's avatar Lyude Paul
Browse files

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: default avatarLyude Paul <lyude@redhat.com>
Reviewed-by: default avatarDaniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250911230147.650077-3-lyude@redhat.com
parent e3f4bdaf

drivers/gpu/drm/drm_gem_shmem_helper.c

+18 −5
Original line number Diff line number Diff line
@@ -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);

include/drm/drm_gem_shmem_helper.h

+1 −0
Original line number Diff line number Diff line
@@ -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);