tree 1943f0cac035d6aab5217ba42df1a8d243c2d270
parent 0e6d31a7336f41ef0375f5398c79e54de8e219b6
author Kirill A. Shutemov <kirill.shutemov@linux.intel.com> 1452905481 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1452909392 -0800

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>
Cc: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>