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Subject[PATCH 1/9] ksm: fix mlockfreed to munlocked
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 (and
whinges "Page flag mlocked set for process" in mmotm, whereas mainline
is silently forgiving). Call munlock_vma_page() to fix that.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
---
Is this a fix that I ought to backport to 2.6.32? It does rely on part of
an earlier patch (moved unlock_page down), so does not apply cleanly as is.
mm/internal.h | 3 ++-
mm/ksm.c | 4 ++++
mm/mlock.c | 4 ++--
3 files changed, 8 insertions(+), 3 deletions(-)
--- ksm0/mm/internal.h 2009-11-14 10:17:02.000000000 +0000
+++ ksm1/mm/internal.h 2009-11-22 20:39:56.000000000 +0000
@@ -105,9 +105,10 @@ 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
--- ksm0/mm/ksm.c 2009-11-14 10:17:02.000000000 +0000
+++ ksm1/mm/ksm.c 2009-11-22 20:39:56.000000000 +0000
@@ -34,6 +34,7 @@
#include <linux/ksm.h>

#include <asm/tlbflush.h>
+#include "internal.h"

/*
* A few notes about the KSM scanning process,
@@ -762,6 +763,9 @@ static int try_to_merge_one_page(struct
pages_identical(page, kpage))
err = replace_page(vma, page, kpage, orig_pte);

+ if ((vma->vm_flags & VM_LOCKED) && !err)
+ munlock_vma_page(page);
+
unlock_page(page);
out:
return err;
--- ksm0/mm/mlock.c 2009-11-14 10:17:02.000000000 +0000
+++ ksm1/mm/mlock.c 2009-11-22 20:39:56.000000000 +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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