Re: [PATCH 13/16] mm: fix minor scan count bugs

[Wu Fengguang]

Hi Andrew,

Here is the standalone version for -mm inclusion.


Subject: mm: fix minor scan count bugs

- 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@xxxxxxxxxxxxxxxx>
---

--- linux.orig/mm/vmscan.c
+++ linux/mm/vmscan.c
@@ -837,7 +837,8 @@ 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);
 
@@ -886,14 +887,15 @@ static void shrink_cache(struct zone *zo
 		zone->pages_scanned += nr_scan;
 		spin_unlock_irq(&zone->lru_lock);
 
-		if (nr_taken == 0)
-			goto done;
-
 		max_scan -= 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)
+			goto done;
+
 		nr_freed = shrink_list(&page_list, sc);
 		if (current_is_kswapd())
 			mod_page_state(kswapd_steal, nr_freed);
-
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