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>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cd4a5ed..c55763e 100644 (file)
--- 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:
        /*