The implementation of the lruvec stat functions and their variants for
accounting through a page, or accounting from a preemptible context, are
mostly identical and needlessly repetitive.

Implement the lruvec_page functions by looking up the page's lruvec and
then using the lruvec function.

Implement the functions for preemptible contexts by disabling preemption
before calling the atomic context functions.

Link: http://lkml.kernel.org/r/20171103153336.24044-2-hannes@cmpxchg.orgSigned-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NVladimir Davydov <vdavydov.dev@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>