[PATCH 2/3 -mmotm-2009-12-10-17-19] Count zero page as file_rss

[Minchan Kim <minchan.kim@gmail.com>]

Long time ago, we counted zero page as file_rss.
But after reinstanted zero page, we don't do it.
It means rss of process would be smaller than old.

It could chage OOM victim selection.

Kame reported following as
"Before starting zero-page works, I checked "questions" in lkml and
found some reports that some applications start to go OOM after zero-page
removal.

For me, I know one of my customer's application depends on behavior of
zero page (on RHEL5). So, I tried to add again it before RHEL6 because
I think removal of zero-page corrupts compatibility."

So how about adding zero page as file_rss again for compatibility?

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
---
 mm/memory.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 3743fb5..a4ba271 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1995,6 +1995,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	int reuse = 0, ret = 0;
 	int page_mkwrite = 0;
 	struct page *dirty_page = NULL;
+	int zero_pfn = 0;
 
 	old_page = vm_normal_page(vma, address, orig_pte);
 	if (!old_page) {
@@ -2117,7 +2118,8 @@ gotten:
 	if (unlikely(anon_vma_prepare(vma)))
 		goto oom;
 
-	if (is_zero_pfn(pte_pfn(orig_pte))) {
+	zero_pfn = is_zero_pfn(pte_pfn(orig_pte));
+	if (zero_pfn) {
 		new_page = alloc_zeroed_user_highpage_movable(vma, address);
 		if (!new_page)
 			goto oom;
@@ -2147,7 +2149,7 @@ gotten:
 	 */
 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
 	if (likely(pte_same(*page_table, orig_pte))) {
-		if (old_page) {
+		if (old_page || zero_pfn) {
 			if (!PageAnon(old_page)) {
 				dec_mm_counter(mm, file_rss);
 				inc_mm_counter(mm, anon_rss);
@@ -2650,6 +2652,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		spin_lock(ptl);
 		if (!pte_none(*page_table))
 			goto unlock;
+		inc_mm_counter(mm, file_rss);
 		goto setpte;
 	}
 
-- 
1.5.6.5

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