dma-buf: use new iterator in dma_resv_get_fences v3

This makes the function much simpler since the complex
retry logic is now handled elsewhere.

v2: use sizeof(void*) instead
v3: fix rebase bug
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-6-christian.koenig@amd.com

drivers/dma-buf/dma-resv.c

@@ -489,99 +489,61 @@ EXPORT_SYMBOL(dma_resv_copy_fences);
  * dma_resv_get_fences - Get an object's shared and exclusive
  * fences without update side lock held
  * @obj: the reservation object
- * @pfence_excl: the returned exclusive fence (or NULL)
- * @pshared_count: the number of shared fences returned
- * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
+ * @fence_excl: the returned exclusive fence (or NULL)
+ * @shared_count: the number of shared fences returned
+ * @shared: the array of shared fence ptrs returned (array is krealloc'd to
  * the required size, and must be freed by caller)
  *
  * Retrieve all fences from the reservation object. If the pointer for the
  * exclusive fence is not specified the fence is put into the array of the
  * shared fences as well. Returns either zero or -ENOMEM.
  */
-int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl,
-			unsigned int *pshared_count,
-			struct dma_fence ***pshared)
+int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **fence_excl,
+			unsigned int *shared_count, struct dma_fence ***shared)
 {
-	struct dma_fence **shared = NULL;
-	struct dma_fence *fence_excl;
-	unsigned int shared_count;
-	int ret = 1;
-
-	do {
-		struct dma_resv_list *fobj;
-		unsigned int i, seq;
-		size_t sz = 0;
-
-		shared_count = i = 0;
-
-		rcu_read_lock();
-		seq = read_seqcount_begin(&obj->seq);
+	struct dma_resv_iter cursor;
+	struct dma_fence *fence;
 
-		fence_excl = dma_resv_excl_fence(obj);
-		if (fence_excl && !dma_fence_get_rcu(fence_excl))
-			goto unlock;
+	*shared_count = 0;
+	*shared = NULL;
 
-		fobj = dma_resv_shared_list(obj);
-		if (fobj)
-			sz += sizeof(*shared) * fobj->shared_max;
+	if (fence_excl)
+		*fence_excl = NULL;
 
-		if (!pfence_excl && fence_excl)
-			sz += sizeof(*shared);
+	dma_resv_iter_begin(&cursor, obj, true);
+	dma_resv_for_each_fence_unlocked(&cursor, fence) {
 
-		if (sz) {
-			struct dma_fence **nshared;
+		if (dma_resv_iter_is_restarted(&cursor)) {
+			unsigned int count;
 
-			nshared = krealloc(shared, sz,
-					   GFP_NOWAIT | __GFP_NOWARN);
-			if (!nshared) {
-				rcu_read_unlock();
+			while (*shared_count)
+				dma_fence_put((*shared)[--(*shared_count)]);
 
-				dma_fence_put(fence_excl);
-				fence_excl = NULL;
+			if (fence_excl)
+				dma_fence_put(*fence_excl);
 
-				nshared = krealloc(shared, sz, GFP_KERNEL);
-				if (nshared) {
-					shared = nshared;
-					continue;
-				}
+			count = cursor.fences ? cursor.fences->shared_count : 0;
+			count += fence_excl ? 0 : 1;
 
-				ret = -ENOMEM;
-				break;
-			}
-			shared = nshared;
-			shared_count = fobj ? fobj->shared_count : 0;
-			for (i = 0; i < shared_count; ++i) {
-				shared[i] = rcu_dereference(fobj->shared[i]);
-				if (!dma_fence_get_rcu(shared[i]))
-					break;
-			}
+			/* Eventually re-allocate the array */
+			*shared = krealloc_array(*shared, count,
+						 sizeof(void *),
+						 GFP_KERNEL);
+			if (count && !*shared) {
+				dma_resv_iter_end(&cursor);
+				return -ENOMEM;
 			}
-
-		if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
-			while (i--)
-				dma_fence_put(shared[i]);
-			dma_fence_put(fence_excl);
-			goto unlock;
 		}
 
-		ret = 0;
-unlock:
-		rcu_read_unlock();
-	} while (ret);
-
-	if (pfence_excl)
-		*pfence_excl = fence_excl;
-	else if (fence_excl)
-		shared[shared_count++] = fence_excl;
-
-	if (!shared_count) {
-		kfree(shared);
-		shared = NULL;
+		dma_fence_get(fence);
+		if (dma_resv_iter_is_exclusive(&cursor) && fence_excl)
+			*fence_excl = fence;
+		else
+			(*shared)[(*shared_count)++] = fence;
 	}
+	dma_resv_iter_end(&cursor);
 
-	*pshared_count = shared_count;
-	*pshared = shared;
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(dma_resv_get_fences);