From: Peter Zijlstra <[email protected]>
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 <[email protected]>
---
mm/mprotect.c | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
Index: 2.6-mm/mm/mprotect.c
===================================================================
--- 2.6-mm.orig/mm/mprotect.c 2006-06-23 01:35:24.000000000 +0200
+++ 2.6-mm/mm/mprotect.c 2006-06-23 15:06:10.000000000 +0200
@@ -28,7 +28,8 @@
#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;
@@ -43,7 +44,14 @@ static void change_pte_range(struct mm_s
* 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
@@ -67,7 +75,8 @@ static void change_pte_range(struct mm_s
}
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;
@@ -77,12 +86,13 @@ static inline void change_pmd_range(stru
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;
@@ -92,12 +102,13 @@ static inline void change_pud_range(stru
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;
@@ -111,7 +122,7 @@ static void change_protection(struct vm_
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);
}
@@ -128,6 +139,7 @@ mprotect_fixup(struct vm_area_struct *vm
pgprot_t newprot;
pgoff_t pgoff;
int error;
+ int dirty_accountable = 0;
if (newflags == oldflags) {
*pprev = vma;
@@ -190,8 +202,10 @@ success:
(VM_WRITE|VM_SHARED)) &&
vma->vm_file && vma->vm_file->f_mapping &&
mapping_cap_account_dirty(vma->vm_file->f_mapping)) ||
- (vma->vm_ops && vma->vm_ops->page_mkwrite))
+ (vma->vm_ops && vma->vm_ops->page_mkwrite)) {
mask &= ~VM_SHARED;
+ dirty_accountable = 1;
+ }
newprot = protection_map[newflags & mask];
@@ -204,7 +218,7 @@ success:
if (is_vm_hugetlb_page(vma))
hugetlb_change_protection(vma, start, end, newprot);
else
- change_protection(vma, start, end, newprot);
+ change_protection(vma, start, end, newprot, dirty_accountable);
vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
vm_stat_account(mm, newflags, vma->vm_file, nrpages);
return 0;
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
