From: Mel Gorman <mgorman@suse.de>
Date: Mon, 16 Dec 2013 23:44:43 +0000 (+1100)
Subject: mm: numa: do not clear PMD during PTE update scan
X-Git-Tag: next-20131220~2^2~271
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1463967443ab695e970617af901020556168dd87;p=karo-tx-linux.git

mm: numa: do not clear PMD during PTE update scan

If the PMD is flushed then a parallel fault in handle_mm_fault() will
enter the pmd_none and do_huge_pmd_anonymous_page() path where it'll
attempt to insert a huge zero page.  This is wasteful so the patch avoids
clearing the PMD when setting pmd_numa.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 51f069303ab9..420826efda48 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1539,7 +1539,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 			 */
 			if (!is_huge_zero_page(page) &&
 			    !pmd_numa(*pmd)) {
-				entry = pmdp_get_and_clear(mm, addr, pmd);
+				entry = *pmd;
 				entry = pmd_mknuma(entry);
 				ret = HPAGE_PMD_NR;
 			}