Unverified Commit aa8c85af authored by Asahi Lina's avatar Asahi Lina Committed by Javier Martinez Canillas
Browse files

drm/shmem-helper: Fix locking for drm_gem_shmem_get_pages_sgt() 



Other functions touching shmem->sgt take the pages lock, so do that here
too. drm_gem_shmem_get_pages() & co take the same lock, so move to the
_locked() variants to avoid recursive locking.

Discovered while auditing locking to write the Rust abstractions.

Fixes: 2194a63a ("drm: Add library for shmem backed GEM objects")
Fixes: 4fa3d66f ("drm/shmem: Do dma_unmap_sg before purging pages")
Signed-off-by: default avatarAsahi Lina <lina@asahilina.net>
Reviewed-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Signed-off-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230205125124.2260-1-lina@asahilina.net
parent 7c18189b

drivers/gpu/drm/drm_gem_shmem_helper.c

+34 −20
Original line number Diff line number Diff line
@@ -678,23 +678,7 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem) 
}

EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);



/**

 * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a

 *				 scatter/gather table for a shmem GEM object.

 * @shmem: shmem GEM object

 *

 * This function returns a scatter/gather table suitable for driver usage. If

 * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg

 * table created.

 *

 * This is the main function for drivers to get at backing storage, and it hides

 * and difference between dma-buf imported and natively allocated objects.

 * drm_gem_shmem_get_sg_table() should not be directly called by drivers.

 *

 * Returns:

 * A pointer to the scatter/gather table of pinned pages or errno on failure.

 */

struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)

static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)

{

	struct drm_gem_object *obj = &shmem->base;

	int ret;
@@ -705,7 +689,7 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem) 


	WARN_ON(obj->import_attach);



	ret = drm_gem_shmem_get_pages(shmem);

	ret = drm_gem_shmem_get_pages_locked(shmem);

	if (ret)

		return ERR_PTR(ret);
@@ -727,10 +711,40 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem) 
	sg_free_table(sgt);

	kfree(sgt);

err_put_pages:

	drm_gem_shmem_put_pages(shmem);

	drm_gem_shmem_put_pages_locked(shmem);

	return ERR_PTR(ret);

}



/**

 * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a

 *				 scatter/gather table for a shmem GEM object.

 * @shmem: shmem GEM object

 *

 * This function returns a scatter/gather table suitable for driver usage. If

 * the sg table doesn't exist, the pages are pinned, dma-mapped, and a sg

 * table created.

 *

 * This is the main function for drivers to get at backing storage, and it hides

 * and difference between dma-buf imported and natively allocated objects.

 * drm_gem_shmem_get_sg_table() should not be directly called by drivers.

 *

 * Returns:

 * A pointer to the scatter/gather table of pinned pages or errno on failure.

 */

struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem)

{

	int ret;

	struct sg_table *sgt;



	ret = mutex_lock_interruptible(&shmem->pages_lock);

	if (ret)

		return ERR_PTR(ret);

	sgt = drm_gem_shmem_get_pages_sgt_locked(shmem);

	mutex_unlock(&shmem->pages_lock);



	return sgt;

}

EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt);

EXPORT_SYMBOL(drm_gem_shmem_get_pages_sgt);



/**

 * drm_gem_shmem_prime_import_sg_table - Produce a shmem GEM object from