mm: vmscan: remove all_unreclaimable()

Direct reclaim currently calls shrink_zones() to reclaim all members of
a zonelist, and if that wasn't successful it does another pass through
the same zonelist to check overall reclaimability.

Just check reclaimability in shrink_zones() directly and propagate the
result through the return value.  Then remove all_unreclaimable().

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 24 insertions, 25 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6f43df4a5253..74a9e0ae09b0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2244,9 +2244,10 @@ static inline bool should_continue_reclaim(struct zone *zone,
         }
 }
 
-static void shrink_zone(struct zone *zone, struct scan_control *sc)
+static bool shrink_zone(struct zone *zone, struct scan_control *sc)
 {
         unsigned long nr_reclaimed, nr_scanned;
+        bool reclaimable = false;
 
         do {
                 struct mem_cgroup *root = sc->target_mem_cgroup;
@@ -2290,8 +2291,13 @@ static void shrink_zone(struct zone *zone, struct scan_control *sc)
                            sc->nr_scanned - nr_scanned,
                            sc->nr_reclaimed - nr_reclaimed);
 
+                if (sc->nr_reclaimed - nr_reclaimed)
+                        reclaimable = true;
+
         } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
                                          sc->nr_scanned - nr_scanned, sc));
+
+        return reclaimable;
 }
 
 /* Returns true if compaction should go ahead for a high-order request */
@@ -2340,8 +2346,10 @@ static inline bool compaction_ready(struct zone *zone, int order)
  *
  * If a zone is deemed to be full of pinned pages then just give it a light
  * scan then give up on it.
+ *
+ * Returns true if a zone was reclaimable.
  */
-static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
+static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
 {
         struct zoneref *z;
         struct zone *zone;
@@ -2354,6 +2362,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
                 .gfp_mask = sc->gfp_mask,
         };
         enum zone_type requested_highidx = gfp_zone(sc->gfp_mask);
+        bool reclaimable = false;
 
         /*
          * If the number of buffer_heads in the machine exceeds the maximum
@@ -2414,10 +2423,17 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
                                                 &nr_soft_scanned);
                         sc->nr_reclaimed += nr_soft_reclaimed;
                         sc->nr_scanned += nr_soft_scanned;
+                        if (nr_soft_reclaimed)
+                                reclaimable = true;
                         /* need some check for avoid more shrink_zone() */
                 }
 
-                shrink_zone(zone, sc);
+                if (shrink_zone(zone, sc))
+                        reclaimable = true;
+
+                if (global_reclaim(sc) &&
+                    !reclaimable && zone_reclaimable(zone))
+                        reclaimable = true;
         }
 
         /*
@@ -2439,26 +2455,8 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
          * promoted it to __GFP_HIGHMEM.
          */
         sc->gfp_mask = orig_mask;
-}
-
-/* All zones in zonelist are unreclaimable? */
-static bool all_unreclaimable(struct zonelist *zonelist,
-                struct scan_control *sc)
-{
-        struct zoneref *z;
-        struct zone *zone;
 
-        for_each_zone_zonelist_nodemask(zone, z, zonelist,
-                        gfp_zone(sc->gfp_mask), sc->nodemask) {
-                if (!populated_zone(zone))
-                        continue;
-                if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
-                        continue;
-                if (zone_reclaimable(zone))
-                        return false;
-        }
-
-        return true;
+        return reclaimable;
 }
 
 /*
@@ -2482,6 +2480,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 {
         unsigned long total_scanned = 0;
         unsigned long writeback_threshold;
+        bool zones_reclaimable;
 
         delayacct_freepages_start();
 
@@ -2492,7 +2491,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
                                 sc->priority);
                 sc->nr_scanned = 0;
-                shrink_zones(zonelist, sc);
+                zones_reclaimable = shrink_zones(zonelist, sc);
 
                 total_scanned += sc->nr_scanned;
                 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
@@ -2532,8 +2531,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
         if (sc->compaction_ready)
                 return 1;
 
-        /* top priority shrink_zones still had more to do? don't OOM, then */
-        if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
+        /* Any of the zones still reclaimable?  Don't OOM. */
+        if (zones_reclaimable)
                 return 1;
 
         return 0;