mm: make get_scan_ratio() safe for memcg

Currently, get_scan_ratio() always calculate the balancing value for
global reclaim and memcg reclaim doesn't use it.  Therefore it doesn't
have scan_global_lru() condition.

However, we plan to expand get_scan_ratio() to be usable for memcg too,
latter.  Then, The dependency code of global reclaim in the
get_scan_ratio() insert into scan_global_lru() condision explictly.

This patch doesn't have any functional change.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6827d35954fb..e2b31a522a66 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1376,13 +1376,16 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
                 zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
         file  = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
                 zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
-        free  = zone_page_state(zone, NR_FREE_PAGES);
 
-        /* If we have very few page cache pages, force-scan anon pages. */
-        if (unlikely(file + free <= zone->pages_high)) {
-                percent[0] = 100;
-                percent[1] = 0;
-                return;
+        if (scan_global_lru(sc)) {
+                free  = zone_page_state(zone, NR_FREE_PAGES);
+                /* If we have very few page cache pages,
+                   force-scan anon pages. */
+                if (unlikely(file + free <= zone->pages_high)) {
+                        percent[0] = 100;
+                        percent[1] = 0;
+                        return;
+                }
         }
 
         /*