staging: ion: use compound pages on high order pages for system heap

Using compound pages relieves burden on tracking the meta information
which are currently stored in page_info.

Signed-off-by: Heesub Shin <heesub.shin@samsung.com>
Reviewed-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_page_pool.c

@@ -95,6 +95,8 @@ void ion_page_pool_free(struct ion_page_pool *pool, struct page *page)
 {
 	int ret;
 
+	BUG_ON(pool->order != compound_order(page));
+
 	ret = ion_page_pool_add(pool, page);
 	if (ret)
 		ion_page_pool_free_pages(pool, page);
@@ -150,7 +152,7 @@ struct ion_page_pool *ion_page_pool_create(gfp_t gfp_mask, unsigned int order)
 	pool->low_count = 0;
 	INIT_LIST_HEAD(&pool->low_items);
 	INIT_LIST_HEAD(&pool->high_items);
-	pool->gfp_mask = gfp_mask;
+	pool->gfp_mask = gfp_mask | __GFP_COMP;
 	pool->order = order;
 	mutex_init(&pool->mutex);
 	plist_node_init(&pool->list, order);

drivers/staging/android/ion/ion_system_heap.c

@@ -73,7 +73,7 @@ static struct page *alloc_buffer_page(struct ion_system_heap *heap,
 
 		if (order > 4)
 			gfp_flags = high_order_gfp_flags;
-		page = alloc_pages(gfp_flags, order);
+		page = alloc_pages(gfp_flags | __GFP_COMP, order);
 		if (!page)
 			return NULL;
 		ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order,