vmscan: remove all_unreclaimable scan control

This scan control is abused to communicate a return value from
shrink_zones().  Write this idiomatically and remove the knob.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cd4a5edf5be2..c55763ee8312 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -73,8 +73,6 @@ struct scan_control {
 
         int swappiness;
 
-        int all_unreclaimable;
-
         int order;
 
         /*
@@ -1716,14 +1714,14 @@ static void shrink_zone(int priority, struct zone *zone,
  * If a zone is deemed to be full of pinned pages then just give it a light
  * scan then give up on it.
  */
-static void shrink_zones(int priority, struct zonelist *zonelist,
+static int shrink_zones(int priority, struct zonelist *zonelist,
                                         struct scan_control *sc)
 {
         enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
         struct zoneref *z;
         struct zone *zone;
+        int progress = 0;
 
-        sc->all_unreclaimable = 1;
         for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
                                         sc->nodemask) {
                 if (!populated_zone(zone))
@@ -1739,19 +1737,19 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
 
                         if (zone->all_unreclaimable && priority != DEF_PRIORITY)
                                 continue;       /* Let kswapd poll it */
-                        sc->all_unreclaimable = 0;
                 } else {
                         /*
                          * Ignore cpuset limitation here. We just want to reduce
                          * # of used pages by us regardless of memory shortage.
                          */
-                        sc->all_unreclaimable = 0;
                         mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
                                                         priority);
                 }
 
                 shrink_zone(priority, zone, sc);
+                progress = 1;
         }
+        return progress;
 }
 
 /*
@@ -1805,7 +1803,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                 sc->nr_scanned = 0;
                 if (!priority)
                         disable_swap_token();
-                shrink_zones(priority, zonelist, sc);
+                ret = shrink_zones(priority, zonelist, sc);
                 /*
                  * Don't shrink slabs when reclaiming memory from
                  * over limit cgroups
@@ -1842,7 +1840,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                         congestion_wait(BLK_RW_ASYNC, HZ/10);
         }
         /* top priority shrink_zones still had more to do? don't OOM, then */
-        if (!sc->all_unreclaimable && scanning_global_lru(sc))
+        if (ret && scanning_global_lru(sc))
                 ret = sc->nr_reclaimed;
 out:
         /*