memcg: fix oops in mem_cgroup_shrink_usage
memcg: fix oops in mem_cgroup_shrink_usage

Got an oops in mem_cgroup_shrink_usage() when testing loop over tmpfs:
yes, of course, loop0 has no mm: other entry points check but this didn't.

Signed-off-by: Hugh Dickins <a6c5230a10c458028ff1bd5985dd47c394028d47@veritas.com>
Cc: KAMEZAWA Hiroyuki <634f508bd7c47cf0ee4126243675c3e598920fbc@jp.fujitsu.com>
Acked-by: Balbir Singh <65a1aed538f36fed73d8c45e9ddfc585ce9f4abf@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas