mm: memcontrol: let v2 cgroups follow changes in system swappiness

commit 4550c4e157ca3da929593bb6c64080a59141af35 upstream.

Cgroup2 currently doesn't have a per-cgroup swappiness setting.  We
might want to add one later - that's a different discussion - but until
we do, the cgroups should always follow the system setting.  Otherwise
it will be unchangeably set to whatever the ancestor inherited from the
system setting at the time of cgroup creation.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/swap.h b/include/linux/swap.h
index d18b65c53dbb8b421f5a1499a2791ddc4f594319..5fa4aa4ddd05a2f4f2959e06206d122163af96a7 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -533,6 +533,10 @@ static inline swp_entry_t get_swap_page(void)
 #ifdef CONFIG_MEMCG
 static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 {
+       /* Cgroup2 doesn't have per-cgroup swappiness */
+       if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
+               return vm_swappiness;
+
        /* root ? */
        if (mem_cgroup_disabled() || !memcg->css.parent)
                return vm_swappiness;