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mm: fix for infinite churning of mlocked pages 

An mlocked page might lose the isolatation race.  This causes the page to
clear PG_mlocked while it remains in a VM_LOCKED vma.  This means it can
be put onto the [in]active list.  We can rescue it by using try_to_unmap()
in shrink_page_list().

But now, As Wu Fengguang pointed out, vmscan has a bug.  If the page has
PG_referenced, it can't reach try_to_unmap() in shrink_page_list() but is
put into the active list.  If the page is referenced repeatedly, it can
remain on the [in]active list without being moving to the unevictable
list.

This patch fixes it.

Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <<kosaki.motohiro@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2009-08-26 14:29:23 -07:00 committed by Linus Torvalds
parent b62e408c05
commit 03ef83af52
2 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
mm/rmap.c
View File

@ -358,6 +358,7 @@ static int page_referenced_one(struct page *page,
*/ */
if (vma->vm_flags & VM_LOCKED) { if (vma->vm_flags & VM_LOCKED) {
*mapcount = 1; /* break early from loop */ *mapcount = 1; /* break early from loop */
*vm_flags |= VM_LOCKED;
goto out_unmap; goto out_unmap;
} }

9
mm/vmscan.c
View File

@ -630,9 +630,14 @@ static unsigned long shrink_page_list(struct list_head *page_list,
referenced = page_referenced(page, 1, referenced = page_referenced(page, 1,
sc->mem_cgroup, &vm_flags); sc->mem_cgroup, &vm_flags);
/* In active use or really unfreeable? Activate it. */ /*
* In active use or really unfreeable? Activate it.
* If page which have PG_mlocked lost isoltation race,
* try_to_unmap moves it to unevictable list
*/
if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
referenced && page_mapping_inuse(page)) referenced && page_mapping_inuse(page)
&& !(vm_flags & VM_LOCKED))
goto activate_locked; goto activate_locked;
/* /*