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[PATCH] mm: optimize the new mprotect() code a bit

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mprotect() resets the page protections, which could result in extra write
faults for those pages whose dirty state we track using write faults and are
dirty already.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Peter Zijlstra 2006-09-25 23:30:59 -07:00 committed by Linus Torvalds
parent edc79b2a46
commit c1e6098b23
1 changed files with 24 additions and 10 deletions
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34
mm/mprotect.c
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@ -27,7 +27,8 @@
#include <asm/tlbflush.h>
static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
unsigned long addr, unsigned long end, pgprot_t newprot)
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
{
pte_t *pte, oldpte;
spinlock_t *ptl;
@ -42,7 +43,14 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
* bits by wiping the pte and then setting the new pte
* into place.
*/
ptent = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot);
ptent = ptep_get_and_clear(mm, addr, pte);
ptent = pte_modify(ptent, newprot);
/*
* Avoid taking write faults for pages we know to be
* dirty.
*/
if (dirty_accountable && pte_dirty(ptent))
ptent = pte_mkwrite(ptent);
set_pte_at(mm, addr, pte, ptent);
lazy_mmu_prot_update(ptent);
#ifdef CONFIG_MIGRATION
@ -66,7 +74,8 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
}
static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
unsigned long addr, unsigned long end, pgprot_t newprot)
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
{
pmd_t *pmd;
unsigned long next;
@ -76,12 +85,13 @@ static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud,
next = pmd_addr_end(addr, end);
if (pmd_none_or_clear_bad(pmd))
continue;
change_pte_range(mm, pmd, addr, next, newprot);
change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable);
} while (pmd++, addr = next, addr != end);
}
static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
unsigned long addr, unsigned long end, pgprot_t newprot)
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
{
pud_t *pud;
unsigned long next;
@ -91,12 +101,13 @@ static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd,
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud))
continue;
change_pmd_range(mm, pud, addr, next, newprot);
change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable);
} while (pud++, addr = next, addr != end);
}
static void change_protection(struct vm_area_struct *vma,
unsigned long addr, unsigned long end, pgprot_t newprot)
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
{
struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
@ -110,7 +121,7 @@ static void change_protection(struct vm_area_struct *vma,
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
change_pud_range(mm, pgd, addr, next, newprot);
change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable);
} while (pgd++, addr = next, addr != end);
flush_tlb_range(vma, start, end);
}
@ -125,6 +136,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
unsigned long charged = 0;
pgoff_t pgoff;
int error;
int dirty_accountable = 0;
if (newflags == oldflags) {
*pprev = vma;
@ -181,14 +193,16 @@ success:
vma->vm_flags = newflags;
vma->vm_page_prot = protection_map[newflags &
(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
if (vma_wants_writenotify(vma))
if (vma_wants_writenotify(vma)) {
vma->vm_page_prot = protection_map[newflags &
(VM_READ|VM_WRITE|VM_EXEC)];
dirty_accountable = 1;
}
if (is_vm_hugetlb_page(vma))
hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
else
change_protection(vma, start, end, vma->vm_page_prot);
change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
vm_stat_account(mm, newflags, vma->vm_file, nrpages);
return 0;