[PATCH 2/2] dma-fence: Do not call kref utility functions from static inline code

[Andy Ritger]

Commit 10383aea2f44 ("kref: Implement 'struct kref' using refcount_t")
updated the kref implementation to use refcount_t.  Commit 29dee3c03abc
("locking/refcounts: Out-of-line everything") changed the refcount_t
utility functions from static inline to EXPORT_SYMBOL_GPL functions.

Through a chain of dma-fence -> kref -> refcount static inline utility
functions, drm drivers can inadvertently pick up a reference to the
EXPORT_SYMBOL_GPL refcount_t functions.

refcount_t is an internal implementation detail and not intended as
an interface.  Thus, EXPORT_SYMBOL_GPL seems reasonable for it.

Higher-level dma-fence functions, on the other hand, are intended as an
interface exposed to drm drivers.  So, it arguably seems reasonable that
dma-fence functions do not require EXPORT_SYMBOL_GPL.

Move dma_fence_{put,get,get_rcu} from static inline in dma-fence.h to
EXPORT_SYMBOL functions in dma-fence, to make the interface boundary clear.

Signed-off-by: Andy Ritger <aritger at nvidia.com>
---
 drivers/dma-buf/dma-fence.c | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/dma-fence.h   | 40 +++-------------------------------------
 2 files changed, 44 insertions(+), 37 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index d195d617076d..863bf55955ef 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -573,3 +573,44 @@ dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
 	trace_dma_fence_init(fence);
 }
 EXPORT_SYMBOL(dma_fence_init);
+
+/**
+ * dma_fence_put - decreases refcount of the fence
+ * @fence:      [in]    fence to reduce refcount of
+ */
+void dma_fence_put(struct dma_fence *fence)
+{
+	if (fence)
+		kref_put(&fence->refcount, dma_fence_release);
+}
+EXPORT_SYMBOL(dma_fence_put);
+
+/**
+ * dma_fence_get - increases refcount of the fence
+ * @fence:      [in]    fence to increase refcount of
+ *
+ * Returns the same fence, with refcount increased by 1.
+ */
+struct dma_fence *dma_fence_get(struct dma_fence *fence)
+{
+	if (fence)
+		kref_get(&fence->refcount);
+	return fence;
+}
+EXPORT_SYMBOL(dma_fence_get);
+
+/**
+ * dma_fence_get_rcu - get a fence from a reservation_object_list with
+ *                     rcu read lock
+ * @fence:      [in]    fence to increase refcount of
+ *
+ * Function returns NULL if no refcount could be obtained, or the fence.
+ */
+struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
+{
+	if (kref_get_unless_zero(&fence->refcount))
+		return fence;
+	else
+		return NULL;
+}
+EXPORT_SYMBOL(dma_fence_get_rcu);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 6048fa404e57..0e8d714a5bc7 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -185,43 +185,9 @@ void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
 void dma_fence_release(struct kref *kref);
 void dma_fence_free(struct dma_fence *fence);
 
-/**
- * dma_fence_put - decreases refcount of the fence
- * @fence:	[in]	fence to reduce refcount of
- */
-static inline void dma_fence_put(struct dma_fence *fence)
-{
-	if (fence)
-		kref_put(&fence->refcount, dma_fence_release);
-}
-
-/**
- * dma_fence_get - increases refcount of the fence
- * @fence:	[in]	fence to increase refcount of
- *
- * Returns the same fence, with refcount increased by 1.
- */
-static inline struct dma_fence *dma_fence_get(struct dma_fence *fence)
-{
-	if (fence)
-		kref_get(&fence->refcount);
-	return fence;
-}
-
-/**
- * dma_fence_get_rcu - get a fence from a reservation_object_list with
- *                     rcu read lock
- * @fence:	[in]	fence to increase refcount of
- *
- * Function returns NULL if no refcount could be obtained, or the fence.
- */
-static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
-{
-	if (kref_get_unless_zero(&fence->refcount))
-		return fence;
-	else
-		return NULL;
-}
+void dma_fence_put(struct dma_fence *fence);
+struct dma_fence *dma_fence_get(struct dma_fence *fence);
+struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence);
 
 /**
  * dma_fence_get_rcu_safe  - acquire a reference to an RCU tracked fence
-- 
2.1.0