[PATCH 2/2] dmabuf

[Chris Wilson]

add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-627 (-627)
Function                                     old     new   delta
__warned                                    2352    2350      -2
reservation_object_reserve_shared            196     185     -11
reservation_object_add_shared_fence         1272     658    -614
---
 drivers/dma-buf/reservation.c | 165 ++++++++++++------------------------------
 1 file changed, 46 insertions(+), 119 deletions(-)

diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index 314eb1071cce..4b166a4954a6 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -76,8 +76,6 @@ int reservation_object_reserve_shared(struct reservation_object *obj)
 	if (old && old->shared_max) {
 		if (old->shared_count < old->shared_max) {
 			/* perform an in-place update */
-			kfree(obj->staged);
-			obj->staged = NULL;
 			return 0;
 		} else
 			max = old->shared_max * 2;
@@ -95,146 +93,75 @@ int reservation_object_reserve_shared(struct reservation_object *obj)
 
 	obj->staged = fobj;
 	fobj->shared_max = max;
+	fobj->shared_count = 0;
 	return 0;
 }
 EXPORT_SYMBOL(reservation_object_reserve_shared);
 
-static void
-reservation_object_add_shared_inplace(struct reservation_object *obj,
-				      struct reservation_object_list *fobj,
-				      struct dma_fence *fence)
+/**
+ * reservation_object_add_shared_fence - Add a fence to a shared slot
+ * @obj: the reservation object
+ * @fence: the shared fence to add
+ *
+ * Add a fence to a shared slot, obj->lock must be held, and
+ * reservation_object_reserve_shared() has been called.
+ */
+void reservation_object_add_shared_fence(struct reservation_object *obj,
+					 struct dma_fence *fence)
 {
-	struct dma_fence *signaled = NULL;
-	u32 i, signaled_idx;
+	struct reservation_object_list *old, *fobj;
+	struct dma_fence *replace = NULL;
+	u32 max = 0, i = 0;
 
 	dma_fence_get(fence);
 
-	preempt_disable();
-	write_seqcount_begin(&obj->seq);
-
-	for (i = 0; i < fobj->shared_count; ++i) {
-		struct dma_fence *old_fence;
-
-		old_fence = rcu_dereference_protected(fobj->shared[i],
-						reservation_object_held(obj));
+	old = reservation_object_get_list(obj);
+	if (old) {
+		u32 ctx = fence->context;
 
-		if (old_fence->context == fence->context) {
-			/* memory barrier is added by write_seqcount_begin */
-			RCU_INIT_POINTER(fobj->shared[i], fence);
-			write_seqcount_end(&obj->seq);
-			preempt_enable();
+		for (; i < old->shared_count; ++i) {
+			struct dma_fence *check;
 
-			dma_fence_put(old_fence);
-			return;
-		}
+			check = rcu_dereference_protected(old->shared[i],
+							  reservation_object_held(obj));
 
-		if (!signaled && dma_fence_is_signaled(old_fence)) {
-			signaled = old_fence;
-			signaled_idx = i;
+			if (check->context == ctx ||
+			    dma_fence_is_signaled(check)) {
+				replace = check;
+				break;
+			}
 		}
-	}
 
-	/*
-	 * memory barrier is added by write_seqcount_begin,
-	 * fobj->shared_count is protected by this lock too
-	 */
-	if (signaled) {
-		RCU_INIT_POINTER(fobj->shared[signaled_idx], fence);
-	} else {
-		RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
-		fobj->shared_count++;
+		fobj = old;
+		max = old->shared_max;
 	}
 
-	write_seqcount_end(&obj->seq);
-	preempt_enable();
-
-	dma_fence_put(signaled);
-}
-
-static void
-reservation_object_add_shared_replace(struct reservation_object *obj,
-				      struct reservation_object_list *old,
-				      struct reservation_object_list *fobj,
-				      struct dma_fence *fence)
-{
-	unsigned i, j, k;
-
-	dma_fence_get(fence);
+	if (i >= max) {
+		fobj = obj->staged;
+		obj->staged = NULL;
 
-	if (!old) {
-		RCU_INIT_POINTER(fobj->shared[0], fence);
-		fobj->shared_count = 1;
-		goto done;
-	}
-
-	/*
-	 * no need to bump fence refcounts, rcu_read access
-	 * requires the use of kref_get_unless_zero, and the
-	 * references from the old struct are carried over to
-	 * the new.
-	 */
-	for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; ++i) {
-		struct dma_fence *check;
-
-		check = rcu_dereference_protected(old->shared[i],
-						reservation_object_held(obj));
-
-		if (check->context == fence->context ||
-		    dma_fence_is_signaled(check))
-			RCU_INIT_POINTER(fobj->shared[--k], check);
-		else
-			RCU_INIT_POINTER(fobj->shared[j++], check);
+		if (old) {
+			BUG_ON(fobj->shared_max <= old->shared_count);
+			memcpy(fobj->shared, old->shared, old->shared_count);
+			fobj->shared_count = old->shared_count;
+		}
 	}
-	fobj->shared_count = j;
-	RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
-	fobj->shared_count++;
 
-done:
 	preempt_disable();
 	write_seqcount_begin(&obj->seq);
-	/*
-	 * RCU_INIT_POINTER can be used here,
-	 * seqcount provides the necessary barriers
-	 */
-	RCU_INIT_POINTER(obj->fence, fobj);
-	write_seqcount_end(&obj->seq);
-	preempt_enable();
-
-	if (!old)
-		return;
-
-	/* Drop the references to the signaled fences */
-	for (i = k; i < fobj->shared_max; ++i) {
-		struct dma_fence *f;
 
-		f = rcu_dereference_protected(fobj->shared[i],
-					      reservation_object_held(obj));
-		dma_fence_put(f);
-	}
-	kfree_rcu(old, rcu);
-}
-
-/**
- * reservation_object_add_shared_fence - Add a fence to a shared slot
- * @obj: the reservation object
- * @fence: the shared fence to add
- *
- * Add a fence to a shared slot, obj->lock must be held, and
- * reservation_object_reserve_shared() has been called.
- */
-void reservation_object_add_shared_fence(struct reservation_object *obj,
-					 struct dma_fence *fence)
-{
-	struct reservation_object_list *old, *fobj = obj->staged;
+	RCU_INIT_POINTER(fobj->shared[i], fence);
+	if (!replace)
+		fobj->shared_count++;
+	if (fobj != old)
+		RCU_INIT_POINTER(obj->fence, fobj);
 
-	old = reservation_object_get_list(obj);
-	obj->staged = NULL;
+	write_seqcount_end(&obj->seq);
+	preempt_enable();
 
-	if (!fobj) {
-		BUG_ON(old->shared_count >= old->shared_max);
-		reservation_object_add_shared_inplace(obj, old, fence);
-	} else
-		reservation_object_add_shared_replace(obj, old, fobj, fence);
+	dma_fence_put(replace);
+	if (old && fobj != old)
+		kfree_rcu(old, rcu);
 }
 EXPORT_SYMBOL(reservation_object_add_shared_fence);
 
-- 
2.15.1