memcg: convert threshold to bytes

commit 424cdc14138088ada1b0e407a2195b2783c6e5ef upstream.

page_counter_memparse() returns pages for the threshold, while
mem_cgroup_usage() returns bytes for memory usage.  Convert the
threshold to bytes.

Fixes: 3e32cb2e0a12b6915 ("memcg: rename cgroup_event to mem_cgroup_event").
Signed-off-by: Shaohua Li <shli@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.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/mm/memcontrol.c b/mm/memcontrol.c
index a04225d..68dea90 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3677,6 +3677,7 @@
 	ret = page_counter_memparse(args, "-1", &threshold);
 	if (ret)
 		return ret;
+	threshold <<= PAGE_SHIFT;
 
 	mutex_lock(&memcg->thresholds_lock);