![Hugh Dickins](/assets/img/avatar_default.png)
At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set in page->mapping, with the higher bits a pointer to the anon_vma; and have defined PageKsm(page) as that with NULL anon_vma. But KSM swapping will need to store a pointer there: so in preparation for that, now define PAGE_MAPPING_FLAGS as the low two bits, including PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some other use for the bit emerges). Declare page_rmapping(page) to return the pointer part of page->mapping, and page_anon_vma(page) to return the anon_vma pointer when that's what it is. Use these in a few appropriate places: notably, unuse_vma() has been testing page->mapping, but is better to be testing page_anon_vma() (cases may be added in which flag bits are set without any pointer). Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: Izik Eidus <ieidus@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Nick Piggin <npiggin@suse.de> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
81 lines
1.9 KiB
C
81 lines
1.9 KiB
C
#ifndef __LINUX_KSM_H
|
|
#define __LINUX_KSM_H
|
|
/*
|
|
* Memory merging support.
|
|
*
|
|
* This code enables dynamic sharing of identical pages found in different
|
|
* memory areas, even if they are not shared by fork().
|
|
*/
|
|
|
|
#include <linux/bitops.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/vmstat.h>
|
|
|
|
#ifdef CONFIG_KSM
|
|
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
|
|
unsigned long end, int advice, unsigned long *vm_flags);
|
|
int __ksm_enter(struct mm_struct *mm);
|
|
void __ksm_exit(struct mm_struct *mm);
|
|
|
|
static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
|
|
{
|
|
if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
|
|
return __ksm_enter(mm);
|
|
return 0;
|
|
}
|
|
|
|
static inline void ksm_exit(struct mm_struct *mm)
|
|
{
|
|
if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
|
|
__ksm_exit(mm);
|
|
}
|
|
|
|
/*
|
|
* A KSM page is one of those write-protected "shared pages" or "merged pages"
|
|
* which KSM maps into multiple mms, wherever identical anonymous page content
|
|
* is found in VM_MERGEABLE vmas. It's a PageAnon page, with NULL anon_vma.
|
|
*/
|
|
static inline int PageKsm(struct page *page)
|
|
{
|
|
return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
|
|
(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
|
|
}
|
|
|
|
/*
|
|
* But we have to avoid the checking which page_add_anon_rmap() performs.
|
|
*/
|
|
static inline void page_add_ksm_rmap(struct page *page)
|
|
{
|
|
if (atomic_inc_and_test(&page->_mapcount)) {
|
|
page->mapping = (void *) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
|
|
__inc_zone_page_state(page, NR_ANON_PAGES);
|
|
}
|
|
}
|
|
#else /* !CONFIG_KSM */
|
|
|
|
static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
|
|
unsigned long end, int advice, unsigned long *vm_flags)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline void ksm_exit(struct mm_struct *mm)
|
|
{
|
|
}
|
|
|
|
static inline int PageKsm(struct page *page)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
/* No stub required for page_add_ksm_rmap(page) */
|
|
#endif /* !CONFIG_KSM */
|
|
|
|
#endif
|