[PATCH] drm/ttm: Export ttm_bo_get_unless_zero()

[Thomas Hellstrom]

Export ttm_bo_reference_unless_doomed() to be used when looking up buffer
objects that are removed from the lookup structure in the destructor.

Cc: Christian König <christian.koenig at amd.com>
Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
Reviewed-by: Sinclair Yeh <syeh at vmware.com>
---
 drivers/gpu/drm/ttm/ttm_bo_vm.c |  3 +--
 include/drm/ttm/ttm_bo_api.h    | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 6fe91c1b692d..a1d977fbade5 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -409,8 +409,7 @@ static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
 	node = drm_vma_offset_lookup_locked(&bdev->vma_manager, offset, pages);
 	if (likely(node)) {
 		bo = container_of(node, struct ttm_buffer_object, vma_node);
-		if (!kref_get_unless_zero(&bo->kref))
-			bo = NULL;
+		bo = ttm_bo_get_unless_zero(bo);
 	}
 
 	drm_vma_offset_unlock_lookup(&bdev->vma_manager);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 8c19470785e2..3fc4854dce49 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -312,6 +312,24 @@ ttm_bo_reference(struct ttm_buffer_object *bo)
 	return bo;
 }
 
+/**
+ * ttm_bo_get_unless_zero - reference a struct ttm_buffer_object unless
+ * its refcount has already reached zero.
+ * @bo: The buffer object.
+ *
+ * Used to reference a TTM buffer object in lookups where the object is removed
+ * from the lookup structure during the destructor and for RCU lookups.
+ *
+ * Returns: @bo if the referencing was successful, NULL otherwise.
+ */
+static inline __must_check struct ttm_buffer_object *
+ttm_bo_get_unless_zero(struct ttm_buffer_object *bo)
+{
+	if (!kref_get_unless_zero(&bo->kref))
+		return NULL;
+	return bo;
+}
+
 /**
  * ttm_bo_wait - wait for buffer idle.
  *
-- 
2.19.0.rc1