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Commit 3ca7b3c5 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

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: default avatarHugh 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: default avatarRik 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bb3ab596

include/linux/ksm.h

+3 −2
Original line number Diff line number Diff line
@@ -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);

	}

}

include/linux/mm.h

+16 −1
Original line number Diff line number Diff line
@@ -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;

include/linux/rmap.h

+8 −0
Original line number Diff line number Diff line
@@ -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;

mm/migrate.c

+4 −7
Original line number Diff line number Diff line
@@ -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)

mm/rmap.c

+3 −4
Original line number Diff line number Diff line
@@ -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);