+ mm-optimize-the-new-mprotect-code-a-bit.patch added to -mm tree

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The patch titled

     mm: optimize the new mprotect() code a bit

has been added to the -mm tree.  Its filename is

     mm-optimize-the-new-mprotect-code-a-bit.patch

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: mm: optimize the new mprotect() code a bit
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>

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@xxxxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---

 mm/mprotect.c |   34 ++++++++++++++++++++++++----------
 1 files changed, 24 insertions(+), 10 deletions(-)

diff -puN mm/mprotect.c~mm-optimize-the-new-mprotect-code-a-bit mm/mprotect.c
--- a/mm/mprotect.c~mm-optimize-the-new-mprotect-code-a-bit
+++ a/mm/mprotect.c
@@ -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_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
@@ -66,7 +74,8 @@ 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;
@@ -76,12 +85,13 @@ 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;
@@ -91,12 +101,13 @@ 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;
@@ -110,7 +121,7 @@ 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);
 }
@@ -126,6 +137,7 @@ mprotect_fixup(struct vm_area_struct *vm
 	unsigned long mask = VM_READ|VM_WRITE|VM_EXEC|VM_SHARED;
 	pgoff_t pgoff;
 	int error;
+	int dirty_accountable = 0;
 
 	if (newflags == oldflags) {
 		*pprev = vma;
@@ -180,14 +192,16 @@ success:
 	 * held in write mode.
 	 */
 	vma->vm_flags = newflags;
-	if (vma_wants_writenotify(vma, VM_NOTIFY_NO_PROT))
+	if (vma_wants_writenotify(vma, VM_NOTIFY_NO_PROT)) {
 		mask &= ~VM_SHARED;
+		dirty_accountable = 1;
+	}
 	vma->vm_page_prot = protection_map[newflags & mask];
 
 	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;
_

Patches currently in -mm which might be from a.p.zijlstra@xxxxxxxxx are

origin.patch
mm-tracking-shared-dirty-pages.patch
mm-balance-dirty-pages.patch
mm-msync-cleanup.patch
mm-optimize-the-new-mprotect-code-a-bit.patch
mm-small-cleanup-of-install_page.patch
mm-tracking-shared-dirty-pages-checks.patch

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