[PATCH 06/11] dma-buf: add dma_resv_list_fence helper

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Instead of repeating the access check over and over again.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-resv.c | 42 +++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index b1a1a31dc009..49f3c1009821 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -93,6 +93,22 @@ static void dma_resv_list_free(struct dma_resv_list *list)
 	kfree_rcu(list, rcu);
 }
 
+/**
+ * dma_resv_list_fence - return fence for index
+ * @obj: the reservation object
+ * @list: list to get the fence from
+ * @idx: index into the fence array
+ *
+ * Return the fence at the specified index double checking that either the rcu
+ * read side or the dma_resv object is held.
+ */
+static struct dma_fence *dma_resv_list_fence(struct dma_resv *obj,
+					     struct dma_resv_list *list,
+					     unsigned int idx)
+{
+	return rcu_dereference_check(list->shared[idx], dma_resv_held(obj));
+}
+
 /**
  * dma_resv_init - initialize a reservation object
  * @obj: the reservation object
@@ -171,8 +187,7 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 	for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
 		struct dma_fence *fence;
 
-		fence = rcu_dereference_protected(old->shared[i],
-						  dma_resv_held(obj));
+		fence = dma_resv_list_fence(obj, old, i);
 		if (dma_fence_is_signaled(fence))
 			RCU_INIT_POINTER(new->shared[--k], fence);
 		else
@@ -194,13 +209,8 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 		return 0;
 
 	/* Drop the references to the signaled fences */
-	for (i = k; i < max; ++i) {
-		struct dma_fence *fence;
-
-		fence = rcu_dereference_protected(new->shared[i],
-						  dma_resv_held(obj));
-		dma_fence_put(fence);
-	}
+	for (i = k; i < max; ++i)
+		dma_fence_put(dma_resv_list_fence(obj, new, i));
 	kfree_rcu(old, rcu);
 
 	return 0;
@@ -251,8 +261,7 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
 
 	for (i = 0; i < count; ++i) {
 
-		old = rcu_dereference_protected(fobj->shared[i],
-						dma_resv_held(obj));
+		old = dma_resv_list_fence(obj, fobj, i);
 		if (old->context == fence->context ||
 		    dma_fence_is_signaled(old))
 			goto replace;
@@ -303,8 +312,7 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
 
 	/* inplace update, no shared fences */
 	while (i--)
-		dma_fence_put(rcu_dereference_protected(old->shared[i],
-						dma_resv_held(obj)));
+		dma_fence_put(dma_resv_list_fence(obj, old, i));
 
 	dma_fence_put(old_fence);
 }
@@ -350,7 +358,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 			struct dma_fence __rcu **dst;
 			struct dma_fence *fence;
 
-			fence = rcu_dereference(src_list->shared[i]);
+			fence = dma_resv_list_fence(src, src_list, i);
 			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 				     &fence->flags))
 				continue;
@@ -459,7 +467,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
 			shared = nshared;
 			shared_count = fobj ? fobj->shared_count : 0;
 			for (i = 0; i < shared_count; ++i) {
-				shared[i] = rcu_dereference(fobj->shared[i]);
+				shared[i] = dma_resv_list_fence(obj, fobj, i);
 				if (!dma_fence_get_rcu(shared[i]))
 					break;
 			}
@@ -543,7 +551,7 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
 		for (i = 0; !fence && i < shared_count; ++i) {
 			struct dma_fence *lfence;
 
-			lfence = rcu_dereference(fobj->shared[i]);
+			lfence = dma_resv_list_fence(obj, fobj, i);
 			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 				     &lfence->flags))
 				continue;
@@ -629,7 +637,7 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
 		for (i = 0; i < shared_count; ++i) {
 			struct dma_fence *fence;
 
-			fence = rcu_dereference(fobj->shared[i]);
+			fence = dma_resv_list_fence(obj, fobj, i);
 			ret = dma_resv_test_signaled_single(fence);
 			if (ret < 0)
 				goto retry;
-- 
2.25.1