staging: ion: shrink page-pool by page unit

This patch shrink page-pool by page unit.

The system shrinker calls ion_heap_shrink_count() to get nr_to_scan,
and pass it to ion_heap_shrink_scan().
The problem is the return value of ion_heap_shrink_count() is the number
of pages but ion_system_heap_shrink(), which is called by
ion_heap_shrink_scan(), gets the number of chunk.

The main root of this is that ion_page_pool_shrink() returns page count
via ion_page_pool_total() if it have to check pool size. But it frees
chunks of pages if it have to free pools.

This patch first fix ion_page_pool_shrink() to count only pages,
not chunks. And then ion_system_heap_shrink() to work on pages.
Signed-off-by: Gioh Kim <gioh.kim@lge.com>
Reviewed-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_page_pool.c

@@ -116,7 +116,7 @@ static int ion_page_pool_total(struct ion_page_pool *pool, bool high)
 int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
 				int nr_to_scan)
 {
-	int freed;
+	int freed = 0;
 	bool high;
 
 	if (current_is_kswapd())
@@ -127,7 +127,7 @@ int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
 	if (nr_to_scan == 0)
 		return ion_page_pool_total(pool, high);
 
-	for (freed = 0; freed < nr_to_scan; freed++) {
+	while (freed < nr_to_scan) {
 		struct page *page;
 
 		mutex_lock(&pool->mutex);
@@ -141,6 +141,7 @@ int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
 		}
 		mutex_unlock(&pool->mutex);
 		ion_page_pool_free_pages(pool, page);
+		freed += (1 << pool->order);
 	}
 
 	return freed;

drivers/staging/android/ion/ion_system_heap.c

@@ -212,14 +212,26 @@ static int ion_system_heap_shrink(struct ion_heap *heap, gfp_t gfp_mask,
 {
 	struct ion_system_heap *sys_heap;
 	int nr_total = 0;
-	int i;
+	int i, nr_freed;
+	int only_scan = 0;
 
 	sys_heap = container_of(heap, struct ion_system_heap, heap);
 
+	if (!nr_to_scan)
+		only_scan = 1;
+
 	for (i = 0; i < num_orders; i++) {
 		struct ion_page_pool *pool = sys_heap->pools[i];
 
-		nr_total += ion_page_pool_shrink(pool, gfp_mask, nr_to_scan);
+		nr_freed = ion_page_pool_shrink(pool, gfp_mask, nr_to_scan);
+		nr_total += nr_freed;
+
+		if (!only_scan) {
+			nr_to_scan -= nr_freed;
+			/* shrink completed */
+			if (nr_to_scan <= 0)
+				break;
+		}
 	}
 
 	return nr_total;