mm: numa: do not automatically migrate KSM pages

KSM pages can be shared between tasks that are not necessarily related
to each other from a NUMA perspective.  This patch causes those pages to
be ignored by automatic NUMA balancing so they do not migrate and do not
cause unrelated tasks to be grouped together.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/mprotect.c b/mm/mprotect.c
index bb53a6591aea..7332c1785744 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -23,6 +23,7 @@
 #include <linux/mmu_notifier.h>
 #include <linux/migrate.h>
 #include <linux/perf_event.h>
+#include <linux/ksm.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/cacheflush.h>
@@ -63,7 +64,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 
                                 ptent = *pte;
                                 page = vm_normal_page(vma, addr, oldpte);
-                                if (page) {
+                                if (page && !PageKsm(page)) {
                                         if (!pte_numa(oldpte)) {
                                                 ptent = pte_mknuma(ptent);
                                                 set_pte_at(mm, addr, pte, ptent);