staging: ion: remove struct ion_page_pool_item

The page pool uses an internal data structure, ion_page_pool_item, for
wrapping pooled pages and constructing a list. As the struct page
already provides ways for doing exactly the same thing, we do not need
to reinvent the wheel. This commit removes the data structure and slab
allocations for it.

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

@@ -23,11 +23,6 @@
 #include <linux/slab.h>
 #include "ion_priv.h"
 
-struct ion_page_pool_item {
-	struct page *page;
-	struct list_head list;
-};
-
 static void *ion_page_pool_alloc_pages(struct ion_page_pool *pool)
 {
 	struct page *page = alloc_pages(pool->gfp_mask, pool->order);
@@ -47,19 +42,12 @@ static void ion_page_pool_free_pages(struct ion_page_pool *pool,
 
 static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
 {
-	struct ion_page_pool_item *item;
-
-	item = kmalloc(sizeof(struct ion_page_pool_item), GFP_KERNEL);
-	if (!item)
-		return -ENOMEM;
-
 	mutex_lock(&pool->mutex);
-	item->page = page;
 	if (PageHighMem(page)) {
-		list_add_tail(&item->list, &pool->high_items);
+		list_add_tail(&page->lru, &pool->high_items);
 		pool->high_count++;
 	} else {
-		list_add_tail(&item->list, &pool->low_items);
+		list_add_tail(&page->lru, &pool->low_items);
 		pool->low_count++;
 	}
 	mutex_unlock(&pool->mutex);
@@ -68,24 +56,19 @@ static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
 
 static struct page *ion_page_pool_remove(struct ion_page_pool *pool, bool high)
 {
-	struct ion_page_pool_item *item;
 	struct page *page;
 
 	if (high) {
 		BUG_ON(!pool->high_count);
-		item = list_first_entry(&pool->high_items,
-					struct ion_page_pool_item, list);
+		page = list_first_entry(&pool->high_items, struct page, lru);
 		pool->high_count--;
 	} else {
 		BUG_ON(!pool->low_count);
-		item = list_first_entry(&pool->low_items,
-					struct ion_page_pool_item, list);
+		page = list_first_entry(&pool->low_items, struct page, lru);
 		pool->low_count--;
 	}
 
-	list_del(&item->list);
-	page = item->page;
-	kfree(item);
+	list_del(&page->lru);
 	return page;
 }