mm/vmscan.c: simplify shrink_inactive_list()

This merges together duplicated patterns of code.  Also, replace
count_memcg_events() with its irq-careless namesake, because they are
already called in interrupts disabled context.

Link: http://lkml.kernel.org/r/2ece1df4-2989-bc9b-6172-61e9fdde5bfd@virtuozzo.com


Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>