[PATCH v3 19/32] hugepage: convert huge zero page shrinker to new shrinker API

[Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

It consists of:

* returning long instead of int
* separating count from scan
* returning the number of freed entities in scan

Signed-off-by: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
CC: Dave Chinner <dchinner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 mm/huge_memory.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e2f7f5aa..8bf43d3 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -212,24 +212,30 @@ static void put_huge_zero_page(void)
 	BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 }
 
-static int shrink_huge_zero_page(struct shrinker *shrink,
-		struct shrink_control *sc)
+
+static long shrink_huge_zero_page_count(struct shrinker *shrink,
+					struct shrink_control *sc)
 {
-	if (!sc->nr_to_scan)
-		/* we can free zero page only if last reference remains */
-		return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
+	/* we can free zero page only if last reference remains */
+	return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
+}
 
+static long shrink_huge_zero_page_scan(struct shrinker *shrink,
+				       struct shrink_control *sc)
+{
 	if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 		unsigned long zero_pfn = xchg(&huge_zero_pfn, 0);
 		BUG_ON(zero_pfn == 0);
 		__free_page(__pfn_to_page(zero_pfn));
+		return HPAGE_PMD_NR;
 	}
 
 	return 0;
 }
 
 static struct shrinker huge_zero_page_shrinker = {
-	.shrink = shrink_huge_zero_page,
+	.scan_objects = shrink_huge_zero_page_scan,
+	.count_objects = shrink_huge_zero_page_count,
 	.seeks = DEFAULT_SEEKS,
 };
 
-- 
1.8.1.4