Commit 62eede62 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

mm: ZERO_PAGE without PTE_SPECIAL 



Reinstate anonymous use of ZERO_PAGE to all architectures, not just to
those which __HAVE_ARCH_PTE_SPECIAL: as suggested by Nick Piggin.

Contrary to how I'd imagined it, there's nothing ugly about this, just a
zero_pfn test built into one or another block of vm_normal_page().

But the MIPS ZERO_PAGE-of-many-colours case demands is_zero_pfn() and
my_zero_pfn() inlines.  Reinstate its mremap move_pte() shuffling of
ZERO_PAGEs we did from 2.6.17 to 2.6.19?  Not unless someone shouts for
that: it would have to take vm_flags to weed out some cases.

Signed-off-by: default avatarHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3ae77f43

arch/mips/include/asm/pgtable.h

+10 −0
Original line number Diff line number Diff line
@@ -76,6 +76,16 @@ extern unsigned long zero_page_mask; 
#define ZERO_PAGE(vaddr) \

	(virt_to_page((void *)(empty_zero_page + (((unsigned long)(vaddr)) & zero_page_mask))))



#define is_zero_pfn is_zero_pfn

static inline int is_zero_pfn(unsigned long pfn)

{

	extern unsigned long zero_pfn;

	unsigned long offset_from_zero_pfn = pfn - zero_pfn;

	return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);

}



#define my_zero_pfn(addr)	page_to_pfn(ZERO_PAGE(addr))



extern void paging_init(void);



/*

mm/memory.c

+25 −11
Original line number Diff line number Diff line
@@ -108,7 +108,7 @@ static int __init disable_randmaps(char *s) 
}

__setup("norandmaps", disable_randmaps);



static unsigned long zero_pfn __read_mostly;

unsigned long zero_pfn __read_mostly;



/*

 * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
@@ -455,6 +455,20 @@ static inline int is_cow_mapping(unsigned int flags) 
	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;

}



#ifndef is_zero_pfn

static inline int is_zero_pfn(unsigned long pfn)

{

	return pfn == zero_pfn;

}

#endif



#ifndef my_zero_pfn

static inline unsigned long my_zero_pfn(unsigned long addr)

{

	return zero_pfn;

}

#endif



/*

 * vm_normal_page -- This function gets the "struct page" associated with a pte.

 *
@@ -512,7 +526,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, 
			goto check_pfn;

		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))

			return NULL;

		if (pfn != zero_pfn)

		if (!is_zero_pfn(pfn))

			print_bad_pte(vma, addr, pte, NULL);

		return NULL;

	}
@@ -534,6 +548,8 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, 
		}

	}



	if (is_zero_pfn(pfn))

		return NULL;

check_pfn:

	if (unlikely(pfn > highest_memmap_pfn)) {

		print_bad_pte(vma, addr, pte, NULL);
@@ -1161,7 +1177,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, 
	page = vm_normal_page(vma, address, pte);

	if (unlikely(!page)) {

		if ((flags & FOLL_DUMP) ||

		    pte_pfn(pte) != zero_pfn)

		    !is_zero_pfn(pte_pfn(pte)))

			goto bad_page;

		page = pte_page(pte);

	}
@@ -1443,10 +1459,6 @@ struct page *get_dump_page(unsigned long addr) 
	if (__get_user_pages(current, current->mm, addr, 1,

			FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)

		return NULL;

	if (page == ZERO_PAGE(0)) {

		page_cache_release(page);

		return NULL;

	}

	flush_cache_page(vma, addr, page_to_pfn(page));

	return page;

}
@@ -1629,7 +1641,8 @@ int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, 
	 * If we don't have pte special, then we have to use the pfn_valid()

	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*

	 * refcount the page if pfn_valid is true (hence insert_page rather

	 * than insert_pfn).

	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP

	 * without pte special, it would there be refcounted as a normal page.

	 */

	if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {

		struct page *page;
@@ -2097,7 +2110,7 @@ gotten: 
	if (unlikely(anon_vma_prepare(vma)))

		goto oom;



	if (pte_pfn(orig_pte) == zero_pfn) {

	if (is_zero_pfn(pte_pfn(orig_pte))) {

		new_page = alloc_zeroed_user_highpage_movable(vma, address);

		if (!new_page)

			goto oom;
@@ -2658,8 +2671,9 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, 
	spinlock_t *ptl;

	pte_t entry;



	if (HAVE_PTE_SPECIAL && !(flags & FAULT_FLAG_WRITE)) {

		entry = pte_mkspecial(pfn_pte(zero_pfn, vma->vm_page_prot));

	if (!(flags & FAULT_FLAG_WRITE)) {

		entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),

						vma->vm_page_prot));

		ptl = pte_lockptr(mm, pmd);

		spin_lock(ptl);

		if (!pte_none(*page_table))

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