Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c1e6098b authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

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



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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent edc79b2a

mm/mprotect.c

+24 −10
Original line number Diff line number Diff line
@@ -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 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 
	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;