[PATCH 1/2] mm: kmemleak: move the struct page scan into a helper

[Breno Leitao]

The struct page scanning loop sits inline in __kmemleak_scan(), nested
three levels deep and sharing the caller's "stop" variable with the
zone walk around it. Move it into scan_zone_pages(), which scans one
zone and returns 1 if scanning should stop.

No functional change; this only makes room for changing how the pages
are handed to scan_block().

Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
 mm/kmemleak.c | 57 ++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 34 insertions(+), 23 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 8fa409a4f9fb2..4040547a0af84 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1855,6 +1855,39 @@ static void dedup_flush(struct xarray *dedup)
 	}
 }
 
+/*
+ * Scan the struct pages of a zone, skipping memory holes, pages that belong to
+ * another zone and pages that are not in use. Returns 1 if the scan should be
+ * stopped.
+ */
+static int scan_zone_pages(struct zone *zone)
+{
+	unsigned long start_pfn = zone->zone_start_pfn;
+	unsigned long end_pfn = zone_end_pfn(zone);
+	unsigned long pfn;
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
+		struct page *page = pfn_to_online_page(pfn);
+
+		if (!(pfn & 63))
+			cond_resched_tasks_rcu_qs();
+
+		if (!page)
+			continue;
+
+		/* only scan pages belonging to this zone */
+		if (page_zone(page) != zone)
+			continue;
+		/* only scan if page is in use */
+		if (page_count(page) == 0)
+			continue;
+		if (scan_block(page, page + 1, NULL))
+			return 1;
+	}
+
+	return 0;
+}
+
 /*
  * Scan data sections and all the referenced memory blocks allocated via the
  * kernel's standard allocators. This function must be called with the
@@ -1928,29 +1961,7 @@ static int __kmemleak_scan(bool full)
 	 */
 	get_online_mems();
 	for_each_populated_zone(zone) {
-		unsigned long start_pfn = zone->zone_start_pfn;
-		unsigned long end_pfn = zone_end_pfn(zone);
-		unsigned long pfn;
-
-		for (pfn = start_pfn; pfn < end_pfn; pfn++) {
-			struct page *page = pfn_to_online_page(pfn);
-
-			if (!(pfn & 63))
-				cond_resched_tasks_rcu_qs();
-
-			if (!page)
-				continue;
-
-			/* only scan pages belonging to this zone */
-			if (page_zone(page) != zone)
-				continue;
-			/* only scan if page is in use */
-			if (page_count(page) == 0)
-				continue;
-			stop = scan_block(page, page + 1, NULL);
-			if (stop)
-				break;
-		}
+		stop = scan_zone_pages(zone);
 		if (stop)
 			break;
 	}

-- 
2.53.0-Meta