mm: memcg: don't periodically flush stats when memcg is disabled

The root memcg is onlined even when memcg is disabled.  When it's onlined
a 2 second periodic stat flush is started, but no stat flushing is
required when memcg is disabled because there can be no child memcgs. 
Most calls to flush memcg stats are avoided when memcg is disabled as a
result of the mem_cgroup_disabled check added in 7d7ef0a4686a ("mm: memcg:
restore subtree stats flushing"), but the periodic flushing started in
mem_cgroup_css_online is not.  Skip it.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: aa48e47e3906 ("memcg: infrastructure to flush memcg stats")
Signed-off-by: T.J. Mercier <[email protected]>
Acked-by: Shakeel Butt <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Chris Li <[email protected]>
Reported-by: Minchan Kim <[email protected]>
Reviewed-by: Yosry Ahmed <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Michal Koutn <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions