FROMLIST: android: binder: Refactor prev and next buffer into a helper function

(from https://patchwork.kernel.org/patch/9928605/)

Use helper functions buffer_next and buffer_prev instead
of list_entry to get the next and previous buffers.

Bug: 36007193
Change-Id: I422dce84afde3d2138a6d976593b109a9cc49003
Signed-off-by: Sherry Yang <sherryy@android.com>
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index b90222a..8cb979a 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -48,14 +48,23 @@
 			pr_info(x); \
 	} while (0)
 
+static struct binder_buffer *binder_buffer_next(struct binder_buffer *buffer)
+{
+	return list_entry(buffer->entry.next, struct binder_buffer, entry);
+}
+
+static struct binder_buffer *binder_buffer_prev(struct binder_buffer *buffer)
+{
+	return list_entry(buffer->entry.prev, struct binder_buffer, entry);
+}
+
 static size_t binder_alloc_buffer_size(struct binder_alloc *alloc,
 				       struct binder_buffer *buffer)
 {
 	if (list_is_last(&buffer->entry, &alloc->buffers))
 		return alloc->buffer +
 		       alloc->buffer_size - (void *)buffer->data;
-	return (size_t)list_entry(buffer->entry.next,
-			  struct binder_buffer, entry) - (size_t)buffer->data;
+	return (size_t)binder_buffer_next(buffer) - (size_t)buffer->data;
 }
 
 static void binder_insert_free_buffer(struct binder_alloc *alloc,
@@ -470,7 +479,7 @@
 	int free_page_start = 1;
 
 	BUG_ON(alloc->buffers.next == &buffer->entry);
-	prev = list_entry(buffer->entry.prev, struct binder_buffer, entry);
+	prev = binder_buffer_prev(buffer);
 	BUG_ON(!prev->free);
 	if (buffer_end_page(prev) == buffer_start_page(buffer)) {
 		free_page_start = 0;
@@ -482,8 +491,7 @@
 	}
 
 	if (!list_is_last(&buffer->entry, &alloc->buffers)) {
-		next = list_entry(buffer->entry.next,
-				  struct binder_buffer, entry);
+		next = binder_buffer_next(buffer);
 		if (buffer_start_page(next) == buffer_end_page(buffer)) {
 			free_page_end = 0;
 			if (buffer_start_page(next) ==
@@ -544,8 +552,7 @@
 	rb_erase(&buffer->rb_node, &alloc->allocated_buffers);
 	buffer->free = 1;
 	if (!list_is_last(&buffer->entry, &alloc->buffers)) {
-		struct binder_buffer *next = list_entry(buffer->entry.next,
-						struct binder_buffer, entry);
+		struct binder_buffer *next = binder_buffer_next(buffer);
 
 		if (next->free) {
 			rb_erase(&next->rb_node, &alloc->free_buffers);
@@ -553,8 +560,7 @@
 		}
 	}
 	if (alloc->buffers.next != &buffer->entry) {
-		struct binder_buffer *prev = list_entry(buffer->entry.prev,
-						struct binder_buffer, entry);
+		struct binder_buffer *prev = binder_buffer_prev(buffer);
 
 		if (prev->free) {
 			binder_delete_free_buffer(alloc, buffer);