ksm: fix mlockfreed to munlocked

2.6.33-rc1 commit 73848b4684e84a84cfd1555af78d41158f31e16b, adjusted
to include 31e855ea7173bdb0520f9684580423a9560f66e0's movement of
the unlock_page(oldpage), but omit other intervening cleanups.

When KSM merges an mlocked page, it has been forgetting to munlock it:
that's been left to free_page_mlock(), which reports it in /proc/vmstat
as unevictable_pgs_mlockfreed instead of unevictable_pgs_munlocked,
which indicates that such pages _might_ be left unevictable for long
after they should be evictable.  Call munlock_vma_page() to fix that.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 7 insertions, 7 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 5575f8628fe..e9501f83337 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -34,6 +34,7 @@
 #include <linux/ksm.h>
 
 #include <asm/tlbflush.h>
+#include "internal.h"
 
 /*
  * A few notes about the KSM scanning process,
@@ -767,15 +768,14 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
 	 * ptes are necessarily already write-protected.  But in either
 	 * case, we need to lock and check page_count is not raised.
 	 */
-	if (write_protect_page(vma, oldpage, &orig_pte)) {
-		unlock_page(oldpage);
-		goto out_putpage;
-	}
-	unlock_page(oldpage);
-
-	if (pages_identical(oldpage, newpage))
+	if (write_protect_page(vma, oldpage, &orig_pte) == 0 &&
+	    pages_identical(oldpage, newpage))
 		err = replace_page(vma, oldpage, newpage, orig_pte);
 
+	if ((vma->vm_flags & VM_LOCKED) && !err)
+		munlock_vma_page(oldpage);
+
+	unlock_page(oldpage);
 out_putpage:
 	put_page(oldpage);
 	put_page(newpage);