From: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Date: Tue, 25 Jun 2013 21:15:36 +0000 (-0700)
Subject: mm/thp: define HPAGE_PMD_* constants as BUILD_BUG() if !THP
X-Git-Tag: v3.11-rc1~94^2~46
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3766a1abc53164f058d74f950599c797cb3fe302;p=pandora-kernel.git

mm/thp: define HPAGE_PMD_* constants as BUILD_BUG() if !THP

Currently, HPAGE_PMD_* constans rely on PMD_SHIFT regardless of
CONFIG_TRANSPARENT_HUGEPAGE.  PMD_SHIFT is not defined everywhere (e.g.
arm nommu case).

It means we can't use anything like this in generic code:

        if (PageTransHuge(page))
                zero_huge_user(page, 0, HPAGE_PMD_SIZE);
        else
                clear_highpage(page);

For !THP case, PageTransHuge() is 0 and compiler can eliminate
zero_huge_user() call.  But it still need to be valid C expression, means
HPAGE_PMD_SIZE has to expand to something compiler can understand.

Previously, HPAGE_PMD_* were defined to BUILD_BUG() for !THP. Let's come
back to it.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

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