mm/memcg: set pos explicitly for reclaim and !reclaim

During mem_cgroup_iter, there are two ways to get iteration position:
reclaim vs non-reclaim mode.

Let's do it explicitly for reclaim vs non-reclaim mode.

Link: https://lkml.kernel.org/r/20220330234719.18340-3-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f06b5c2..1b76d56 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1013,9 +1013,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
        if (!root)
                root = root_mem_cgroup;
 
-       if (prev && !reclaim)
-               pos = prev;
-
        rcu_read_lock();
 
        if (reclaim) {
@@ -1041,6 +1038,8 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
                         */
                        (void)cmpxchg(&iter->position, pos, NULL);
                }
+       } else if (prev) {
+               pos = prev;
        }
 
        if (pos)