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ksm: fix mlockfreed to munlocked

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2.6.33-rc1 commit 73848b4684, 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>
This commit is contained in:
Hugh Dickins 2009-12-30 23:00:30 +00:00 committed by Greg Kroah-Hartman
parent b2ea8cb9c8
commit 8ac9e80200
3 changed files with 11 additions and 10 deletions
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3
mm/internal.h
View File

@ -107,9 +107,10 @@ static inline int is_mlocked_vma(struct vm_area_struct *vma, struct page *page)
}
/*
* 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

14
mm/ksm.c
View File

@ -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);

4
mm/mlock.c
View File

@ -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));