page-flags: introduce page flags policies wrt compound pages

page-flags: introduce page flags policies wrt compound pages

This patch adds a third argument to macros which create function
definitions for page flags.  This argument defines how page-flags helpers
behave on compound functions.

For now we define four policies:

- PF_ANY: the helper function operates on the page it gets, regardless
  if it's non-compound, head or tail.

- PF_HEAD: the helper function operates on the head page of the compound
  page if it gets tail page.

- PF_NO_TAIL: only head and non-compond pages are acceptable for this
  helper function.

- PF_NO_COMPOUND: only non-compound pages are acceptable for this helper
  function.

For now we use policy PF_ANY for all helpers, which matches current
behaviour.

We do not enforce the policy for TESTPAGEFLAG, because we have flags
checked for random pages all over the kernel.  Noticeable exception to
this is PageTransHuge() which triggers VM_BUG_ON() for tail page.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>