mm: vmscan: remove memcg_shrinker_map_size

Both memcg_shrinker_map_size and shrinker_nr_max is maintained, but
actually the map size can be calculated via shrinker_nr_max, so it seems
unnecessary to keep both.  Remove memcg_shrinker_map_size since
shrinker_nr_max is also used by iterating the bit map.

Link: https://lkml.kernel.org/r/20210311190845.9708-5-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.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 d3fba55..dff5112 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -185,8 +185,12 @@ static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 
 #ifdef CONFIG_MEMCG
+static int shrinker_nr_max;
 
-static int memcg_shrinker_map_size;
+static inline int shrinker_map_size(int nr_items)
+{
+       return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
+}
 
 static void free_shrinker_map_rcu(struct rcu_head *head)
 {
@@ -248,7 +252,7 @@ int alloc_shrinker_maps(struct mem_cgroup *memcg)
                return 0;
 
        down_write(&shrinker_rwsem);
-       size = memcg_shrinker_map_size;
+       size = shrinker_map_size(shrinker_nr_max);
        for_each_node(nid) {
                map = kvzalloc_node(sizeof(*map) + size, GFP_KERNEL, nid);
                if (!map) {
@@ -266,12 +270,13 @@ int alloc_shrinker_maps(struct mem_cgroup *memcg)
 static int expand_shrinker_maps(int new_id)
 {
        int size, old_size, ret = 0;
+       int new_nr_max = new_id + 1;
        struct mem_cgroup *memcg;
 
-       size = DIV_ROUND_UP(new_id + 1, BITS_PER_LONG) * sizeof(unsigned long);
-       old_size = memcg_shrinker_map_size;
+       size = shrinker_map_size(new_nr_max);
+       old_size = shrinker_map_size(shrinker_nr_max);
        if (size <= old_size)
-               return 0;
+               goto out;
 
        if (!root_mem_cgroup)
                goto out;
@@ -290,7 +295,7 @@ static int expand_shrinker_maps(int new_id)
        } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 out:
        if (!ret)
-               memcg_shrinker_map_size = size;
+               shrinker_nr_max = new_nr_max;
 
        return ret;
 }
@@ -323,7 +328,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
 #define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
 
 static DEFINE_IDR(shrinker_idr);
-static int shrinker_nr_max;
 
 static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 {
@@ -340,8 +344,6 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
                        idr_remove(&shrinker_idr, id);
                        goto unlock;
                }
-
-               shrinker_nr_max = id + 1;
        }
        shrinker->id = id;
        ret = 0;