mm: define PAGE_MAPPING_FLAGS

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>
This commit is contained in:
Hugh Dickins 2009-12-14 17:58:57 -08:00 committed by Linus Torvalds
parent bb3ab59683
commit 3ca7b3c5b6
6 changed files with 35 additions and 15 deletions

View file

@ -38,7 +38,8 @@ static inline void ksm_exit(struct mm_struct *mm)
*/
static inline int PageKsm(struct page *page)
{
return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
}
/*
@ -47,7 +48,7 @@ static inline int PageKsm(struct page *page)
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 = (void *) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
__inc_zone_page_state(page, NR_ANON_PAGES);
}
}

View file

@ -620,13 +620,22 @@ void page_address_init(void);
/*
* On an anonymous page mapped into a user virtual memory area,
* page->mapping points to its anon_vma, not to a struct address_space;
* with the PAGE_MAPPING_ANON bit set to distinguish it.
* with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h.
*
* On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
* the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
* and then page->mapping points, not to an anon_vma, but to a private
* structure which KSM associates with that merged page. See ksm.h.
*
* PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
*
* Please note that, confusingly, "page_mapping" refers to the inode
* address_space which maps the page from disk; whereas "page_mapped"
* refers to user virtual address space into which the page is mapped.
*/
#define PAGE_MAPPING_ANON 1
#define PAGE_MAPPING_KSM 2
#define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
extern struct address_space swapper_space;
static inline struct address_space *page_mapping(struct page *page)
@ -644,6 +653,12 @@ static inline struct address_space *page_mapping(struct page *page)
return mapping;
}
/* Neutral page->mapping pointer to address_space or anon_vma or other */
static inline void *page_rmapping(struct page *page)
{
return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
}
static inline int PageAnon(struct page *page)
{
return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;

View file

@ -39,6 +39,14 @@ struct anon_vma {
#ifdef CONFIG_MMU
static inline struct anon_vma *page_anon_vma(struct page *page)
{
if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
PAGE_MAPPING_ANON)
return NULL;
return page_rmapping(page);
}
static inline void anon_vma_lock(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;

View file

@ -172,17 +172,14 @@ static void remove_anon_migration_ptes(struct page *old, struct page *new)
{
struct anon_vma *anon_vma;
struct vm_area_struct *vma;
unsigned long mapping;
mapping = (unsigned long)new->mapping;
if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
return;
/*
* We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
*/
anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
anon_vma = page_anon_vma(new);
if (!anon_vma)
return;
spin_lock(&anon_vma->lock);
list_for_each_entry(vma, &anon_vma->head, anon_vma_node)

View file

@ -203,7 +203,7 @@ struct anon_vma *page_lock_anon_vma(struct page *page)
rcu_read_lock();
anon_mapping = (unsigned long) page->mapping;
if (!(anon_mapping & PAGE_MAPPING_ANON))
if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
goto out;
if (!page_mapped(page))
goto out;
@ -248,8 +248,7 @@ vma_address(struct page *page, struct vm_area_struct *vma)
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
if (PageAnon(page)) {
if ((void *)vma->anon_vma !=
(void *)page->mapping - PAGE_MAPPING_ANON)
if (vma->anon_vma != page_anon_vma(page))
return -EFAULT;
} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
if (!vma->vm_file ||
@ -513,7 +512,7 @@ int page_referenced(struct page *page,
referenced++;
*vm_flags = 0;
if (page_mapped(page) && page->mapping) {
if (page_mapped(page) && page_rmapping(page)) {
if (PageAnon(page))
referenced += page_referenced_anon(page, mem_cont,
vm_flags);

View file

@ -938,7 +938,7 @@ static int unuse_vma(struct vm_area_struct *vma,
unsigned long addr, end, next;
int ret;
if (page->mapping) {
if (page_anon_vma(page)) {
addr = page_address_in_vma(page, vma);
if (addr == -EFAULT)
return 0;