From: Hugh Dickins <hugh@veritas.com>
Date: Tue, 5 Feb 2008 06:29:23 +0000 (-0800)
Subject: mm: don't waste swap on locked pages
X-Git-Tag: v2.6.25-rc1~933
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=5a9bbdcd29adbb786c53eba1dfc3c2d256020d6b

mm: don't waste swap on locked pages

try_to_unmap always fails on a page found in a VM_LOCKED vma (unless
migrating), and recycles it back to the active list.  But if it's an
anonymous page, we've already allocated swap to it: just wasting swap.
Spot locked pages in page_referenced_one and treat them as referenced.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Tested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ethan Solomita <solo@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/rmap.c b/mm/rmap.c
index 0334c8f6b741..57ad276900c9 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -283,7 +283,10 @@ static int page_referenced_one(struct page *page,
 	if (!pte)
 		goto out;
 
-	if (ptep_clear_flush_young(vma, address, pte))
+	if (vma->vm_flags & VM_LOCKED) {
+		referenced++;
+		*mapcount = 1;	/* break early from loop */
+	} else if (ptep_clear_flush_young(vma, address, pte))
 		referenced++;
 
 	/* Pretend the page is referenced if the task has the