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

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
......@@ -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);
/*
......
......@@ -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 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
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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