[PATCH 12/12] mm: fix minor scan count bugs

[Wu Fengguang <wfg@mail.ustc.edu.cn>]

[-- Attachment #1: mm-scan-accounting-fix.patch --]
[-- Type: text/plain, Size: 1100 bytes --]

- in isolate_lru_pages(): reports one more scan. Fix it.
- in shrink_cache(): 0 pages taken does not mean 0 pages scanned. Fix it.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---

 mm/vmscan.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

--- linux.orig/mm/vmscan.c
+++ linux/mm/vmscan.c
@@ -920,7 +920,8 @@ static int isolate_lru_pages(int nr_to_s
 	struct page *page;
 	int scan = 0;
 
-	while (scan++ < nr_to_scan && !list_empty(src)) {
+	while (scan < nr_to_scan && !list_empty(src)) {
+		scan++;
 		page = lru_to_page(src);
 		prefetchw_prev_lru_page(page, src, flags);
 
@@ -967,14 +968,15 @@ static void shrink_cache(struct zone *zo
 	update_zone_age(zone, nr_scan);
 	spin_unlock_irq(&zone->lru_lock);
 
-	if (nr_taken == 0)
-		return;
-
 	sc->nr_scanned += nr_scan;
 	if (current_is_kswapd())
 		mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
 	else
 		mod_page_state_zone(zone, pgscan_direct, nr_scan);
+
+	if (nr_taken == 0)
+		return;
+
 	nr_freed = shrink_list(&page_list, sc);
 	if (current_is_kswapd())
 		mod_page_state(kswapd_steal, nr_freed);

--