mm/vmscan.c: generalize shrink_slab() calls in shrink_node()

The patch makes shrink_slab() be called for root_mem_cgroup in the same
way as it's called for the rest of cgroups.  This simplifies the logic
and improves the readability.

[ktkhai@virtuozzo.com: wrote changelog]
Link: http://lkml.kernel.org/r/153063068338.1818.11496084754797453962.stgit@localhost.localdomain
Signed-off-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Tested-by: Shakeel Butt <shakeelb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Li RongQing <lirongqing@baidu.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Sahitya Tummala <stummala@codeaurora.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@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, 15 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d7a5b8566869..2aa3cb760189 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -627,10 +627,8 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
  * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
  * unaware shrinkers will receive a node id of 0 instead.
  *
- * @memcg specifies the memory cgroup to target. If it is not NULL,
- * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
- * objects from the memory cgroup specified. Otherwise, only unaware
- * shrinkers are called.
+ * @memcg specifies the memory cgroup to target. Unaware shrinkers
+ * are called only if it is the root cgroup.
  *
  * @priority is sc->priority, we take the number of objects and >> by priority
  * in order to get the scan target.
@@ -644,7 +642,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
         struct shrinker *shrinker;
         unsigned long freed = 0;
 
-        if (memcg && !mem_cgroup_is_root(memcg))
+        if (!mem_cgroup_is_root(memcg))
                 return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
 
         if (!down_read_trylock(&shrinker_rwsem))
@@ -657,9 +655,6 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
                         .memcg = memcg,
                 };
 
-                if (!!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE))
-                        continue;
-
                 if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
                         sc.nid = 0;
 
@@ -689,6 +684,7 @@ void drop_slab_node(int nid)
                 struct mem_cgroup *memcg = NULL;
 
                 freed = 0;
+                memcg = mem_cgroup_iter(NULL, NULL, NULL);
                 do {
                         freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
                 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
@@ -2708,9 +2704,8 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
                         shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
                         node_lru_pages += lru_pages;
 
-                        if (memcg)
-                                shrink_slab(sc->gfp_mask, pgdat->node_id,
-                                            memcg, sc->priority);
+                        shrink_slab(sc->gfp_mask, pgdat->node_id,
+                                    memcg, sc->priority);
 
                         /* Record the group's reclaim efficiency */
                         vmpressure(sc->gfp_mask, memcg, false,
@@ -2734,10 +2729,6 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
                         }
                 } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
 
-                if (global_reclaim(sc))
-                        shrink_slab(sc->gfp_mask, pgdat->node_id, NULL,
-                                    sc->priority);
-
                 if (reclaim_state) {
                         sc->nr_reclaimed += reclaim_state->reclaimed_slab;
                         reclaim_state->reclaimed_slab = 0;