[PATCH v3 3/3] mm/kmemleak: stop the per-cpu and struct page scans early too

[Breno Leitao]

The per-cpu and struct page scan loops have no reschedule-stop check of
their own: once a scan is interrupted they keep calling scan_block() for
every remaining block, which scans nothing useful.

Propagate scan_block()'s interrupted status through scan_large_block()
and break both loops as soon as it is set.

Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
 mm/kmemleak.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 916af7cecb3b4..7fa7124727e36 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1558,18 +1558,22 @@ static int scan_block(void *_start, void *_end,
 
 /*
  * Scan a large memory block in MAX_SCAN_SIZE chunks to reduce the latency.
+ * Return non-zero if the scan was interrupted.
  */
 #ifdef CONFIG_SMP
-static void scan_large_block(void *start, void *end)
+static int scan_large_block(void *start, void *end)
 {
 	void *next;
 
 	while (start < end) {
 		next = min(start + MAX_SCAN_SIZE, end);
-		scan_block(start, next, NULL);
+		if (scan_block(start, next, NULL))
+			return 1;
 		start = next;
 		cond_resched();
 	}
+
+	return 0;
 }
 #endif
 
@@ -1889,9 +1893,11 @@ static void kmemleak_scan(void)
 
 #ifdef CONFIG_SMP
 	/* per-cpu sections scanning */
-	for_each_possible_cpu(i)
-		scan_large_block(__per_cpu_start + per_cpu_offset(i),
-				 __per_cpu_end + per_cpu_offset(i));
+	for_each_possible_cpu(i) {
+		if (scan_large_block(__per_cpu_start + per_cpu_offset(i),
+				     __per_cpu_end + per_cpu_offset(i)))
+			break;
+	}
 #endif
 
 	/*
@@ -1902,6 +1908,7 @@ static void kmemleak_scan(void)
 		unsigned long start_pfn = zone->zone_start_pfn;
 		unsigned long end_pfn = zone_end_pfn(zone);
 		unsigned long pfn;
+		int stop = 0;
 
 		for (pfn = start_pfn; pfn < end_pfn; pfn++) {
 			struct page *page = pfn_to_online_page(pfn);
@@ -1918,8 +1925,12 @@ static void kmemleak_scan(void)
 			/* only scan if page is in use */
 			if (page_count(page) == 0)
 				continue;
-			scan_block(page, page + 1, NULL);
+			stop = scan_block(page, page + 1, NULL);
+			if (stop)
+				break;
 		}
+		if (stop)
+			break;
 	}
 	put_online_mems();
 

-- 
2.53.0-Meta