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SubjectRe: [00/97] 2.6.32.3 stable review
On Mon, 4 Jan 2010, Greg KH wrote:
> This is the start of the stable review cycle for the 2.6.32.3 release.
> There are 97 patches in this series, all will be posted as a response to
> this one. If anyone has any issues with these being applied, please let
> us know. If anyone is a maintainer of the proper subsystem, and wants
> to add a Signed-off-by: line to the patch, please respond with it.

I had hoped that the patch below would make it into 2.6.32.3:
but so long as it's not lost, I think it can wait until 2.6.32.4.

Thanks,
Hugh

From hugh.dickins@tiscali.co.uk Wed Dec 30 23:00:31 2009
Date: Wed, 30 Dec 2009 23:00:30 +0000 (GMT)
From: Hugh Dickins <hugh.dickins@tiscali.co.uk>
To: stable@kernel.org
Cc: Izik Eidus <ieidus@redhat.com>, Andrea Arcangeli <aarcange@redhat.com>, Chris Wright <chrisw@redhat.com>, Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH 2.6.32-stable] 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>
---

mm/internal.h | 3 ++-
mm/ksm.c | 14 +++++++-------
mm/mlock.c | 4 ++--
3 files changed, 11 insertions(+), 10 deletions(-)

--- 2.6.32.2/mm/internal.h 2009-12-03 03:51:21.000000000 +0000
+++ stable/mm/internal.h 2009-12-30 20:38:17.000000000 +0000
@@ -107,9 +107,10 @@ static inline int is_mlocked_vma(struct
}

/*
- * must be called with vma's mmap_sem held for read, and page locked.
+ * must be called with vma's mmap_sem held for read or write, and page locked.
*/
extern void mlock_vma_page(struct page *page);
+extern void munlock_vma_page(struct page *page);

/*
* Clear the page's PageMlocked(). This can be useful in a situation where
--- 2.6.32.2/mm/ksm.c 2009-12-03 03:51:21.000000000 +0000
+++ stable/mm/ksm.c 2009-12-30 20:38:17.000000000 +0000
@@ -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
* 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);
--- 2.6.32.2/mm/mlock.c 2009-12-03 03:51:21.000000000 +0000
+++ stable/mm/mlock.c 2009-12-30 20:38:17.000000000 +0000
@@ -99,14 +99,14 @@ void mlock_vma_page(struct page *page)
* not get another chance to clear PageMlocked. If we successfully
* isolate the page and try_to_munlock() detects other VM_LOCKED vmas
* mapping the page, it will restore the PageMlocked state, unless the page
- * is mapped in a non-linear vma. So, we go ahead and SetPageMlocked(),
+ * is mapped in a non-linear vma. So, we go ahead and ClearPageMlocked(),
* perhaps redundantly.
* If we lose the isolation race, and the page is mapped by other VM_LOCKED
* vmas, we'll detect this in vmscan--via try_to_munlock() or try_to_unmap()
* either of which will restore the PageMlocked state by calling
* mlock_vma_page() above, if it can grab the vma's mmap sem.
*/
-static void munlock_vma_page(struct page *page)
+void munlock_vma_page(struct page *page)
{
BUG_ON(!PageLocked(page));


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