mm: Count the number of pages affected in change_protection()

This will be used for three kinds of purposes:

 - to optimize mprotect()

 - to speed up working set scanning for working set areas that
   have not been touched

 - to more accurately scan per real working set

No change in functionality from this patch.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2251648..06e691b 100644 (file)
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -87,7 +87,7 @@ struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
                                pud_t *pud, int write);
 int pmd_huge(pmd_t pmd);
 int pud_huge(pud_t pmd);
-void hugetlb_change_protection(struct vm_area_struct *vma,
+unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
                unsigned long address, unsigned long end, pgprot_t newprot);
 
 #else /* !CONFIG_HUGETLB_PAGE */
@@ -132,7 +132,11 @@ static inline void copy_huge_page(struct page *dst, struct page *src)
 {
 }
 
-#define hugetlb_change_protection(vma, address, end, newprot)
+static inline unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
+               unsigned long address, unsigned long end, pgprot_t newprot)
+{
+       return 0;
+}
 
 static inline void __unmap_hugepage_range_final(struct mmu_gather *tlb,
                        struct vm_area_struct *vma, unsigned long start,

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bcaab4e..1856c62 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1078,6 +1078,9 @@ extern unsigned long move_page_tables(struct vm_area_struct *vma,
 extern unsigned long do_mremap(unsigned long addr,
                               unsigned long old_len, unsigned long new_len,
                               unsigned long flags, unsigned long new_addr);
+extern unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
+                             unsigned long end, pgprot_t newprot,
+                             int dirty_accountable);
 extern int mprotect_fixup(struct vm_area_struct *vma,
                          struct vm_area_struct **pprev, unsigned long start,
                          unsigned long end, unsigned long newflags);

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 59a0059..712895e 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3014,7 +3014,7 @@ same_page:
        return i ? i : -EFAULT;
 }
 
-void hugetlb_change_protection(struct vm_area_struct *vma,
+unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
                unsigned long address, unsigned long end, pgprot_t newprot)
 {
        struct mm_struct *mm = vma->vm_mm;
@@ -3022,6 +3022,7 @@ void hugetlb_change_protection(struct vm_area_struct *vma,
        pte_t *ptep;
        pte_t pte;
        struct hstate *h = hstate_vma(vma);
+       unsigned long pages = 0;
 
        BUG_ON(address >= end);
        flush_cache_range(vma, address, end);
@@ -3032,12 +3033,15 @@ void hugetlb_change_protection(struct vm_area_struct *vma,
                ptep = huge_pte_offset(mm, address);
                if (!ptep)
                        continue;
-               if (huge_pmd_unshare(mm, &address, ptep))
+               if (huge_pmd_unshare(mm, &address, ptep)) {
+                       pages++;
                        continue;
+               }
                if (!huge_pte_none(huge_ptep_get(ptep))) {
                        pte = huge_ptep_get_and_clear(mm, address, ptep);
                        pte = pte_mkhuge(pte_modify(pte, newprot));
                        set_huge_pte_at(mm, address, ptep, pte);
+                       pages++;
                }
        }
        spin_unlock(&mm->page_table_lock);
@@ -3049,6 +3053,8 @@ void hugetlb_change_protection(struct vm_area_struct *vma,
         */
        flush_tlb_range(vma, start, end);
        mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
+
+       return pages << h->order;
 }
 
 int hugetlb_reserve_pages(struct inode *inode,

diff --git a/mm/mprotect.c b/mm/mprotect.c
index a409926..1e265be 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -35,12 +35,13 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
 }
 #endif
 
-static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
+static unsigned long change_pte_range(struct mm_struct *mm, pmd_t *pmd,
                unsigned long addr, unsigned long end, pgprot_t newprot,
                int dirty_accountable)
 {
        pte_t *pte, oldpte;
        spinlock_t *ptl;
+       unsigned long pages = 0;
 
        pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
        arch_enter_lazy_mmu_mode();
@@ -60,6 +61,7 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
                                ptent = pte_mkwrite(ptent);
 
                        ptep_modify_prot_commit(mm, addr, pte, ptent);
+                       pages++;
                } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
                        swp_entry_t entry = pte_to_swp_entry(oldpte);
 
@@ -72,18 +74,22 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
                                set_pte_at(mm, addr, pte,
                                        swp_entry_to_pte(entry));
                        }
+                       pages++;
                }
        } while (pte++, addr += PAGE_SIZE, addr != end);
        arch_leave_lazy_mmu_mode();
        pte_unmap_unlock(pte - 1, ptl);
+
+       return pages;
 }
 
-static inline void change_pmd_range(struct vm_area_struct *vma, pud_t *pud,
+static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pud_t *pud,
                unsigned long addr, unsigned long end, pgprot_t newprot,
                int dirty_accountable)
 {
        pmd_t *pmd;
        unsigned long next;
+       unsigned long pages = 0;
 
        pmd = pmd_offset(pud, addr);
        do {
@@ -91,35 +97,42 @@ static inline void change_pmd_range(struct vm_area_struct *vma, pud_t *pud,
                if (pmd_trans_huge(*pmd)) {
                        if (next - addr != HPAGE_PMD_SIZE)
                                split_huge_page_pmd(vma->vm_mm, pmd);
-                       else if (change_huge_pmd(vma, pmd, addr, newprot))
+                       else if (change_huge_pmd(vma, pmd, addr, newprot)) {
+                               pages += HPAGE_PMD_NR;
                                continue;
+                       }
                        /* fall through */
                }
                if (pmd_none_or_clear_bad(pmd))
                        continue;
-               change_pte_range(vma->vm_mm, pmd, addr, next, newprot,
+               pages += change_pte_range(vma->vm_mm, pmd, addr, next, newprot,
                                 dirty_accountable);
        } while (pmd++, addr = next, addr != end);
+
+       return pages;
 }
 
-static inline void change_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
+static inline unsigned long change_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
                unsigned long addr, unsigned long end, pgprot_t newprot,
                int dirty_accountable)
 {
        pud_t *pud;
        unsigned long next;
+       unsigned long pages = 0;
 
        pud = pud_offset(pgd, addr);
        do {
                next = pud_addr_end(addr, end);
                if (pud_none_or_clear_bad(pud))
                        continue;
-               change_pmd_range(vma, pud, addr, next, newprot,
+               pages += change_pmd_range(vma, pud, addr, next, newprot,
                                 dirty_accountable);
        } while (pud++, addr = next, addr != end);
+
+       return pages;
 }
 
-static void change_protection(struct vm_area_struct *vma,
+static unsigned long change_protection_range(struct vm_area_struct *vma,
                unsigned long addr, unsigned long end, pgprot_t newprot,
                int dirty_accountable)
 {
@@ -127,6 +140,7 @@ static void change_protection(struct vm_area_struct *vma,
        pgd_t *pgd;
        unsigned long next;
        unsigned long start = addr;
+       unsigned long pages = 0;
 
        BUG_ON(addr >= end);
        pgd = pgd_offset(mm, addr);
@@ -135,10 +149,30 @@ 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(vma, pgd, addr, next, newprot,
+               pages += change_pud_range(vma, pgd, addr, next, newprot,
                                 dirty_accountable);
        } while (pgd++, addr = next, addr != end);
+
        flush_tlb_range(vma, start, end);
+
+       return pages;
+}
+
+unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
+                      unsigned long end, pgprot_t newprot,
+                      int dirty_accountable)
+{
+       struct mm_struct *mm = vma->vm_mm;
+       unsigned long pages;
+
+       mmu_notifier_invalidate_range_start(mm, start, end);
+       if (is_vm_hugetlb_page(vma))
+               pages = hugetlb_change_protection(vma, start, end, newprot);
+       else
+               pages = change_protection_range(vma, start, end, newprot, dirty_accountable);
+       mmu_notifier_invalidate_range_end(mm, start, end);
+
+       return pages;
 }
 
 int
@@ -213,12 +247,8 @@ success:
                dirty_accountable = 1;
        }
 
-       mmu_notifier_invalidate_range_start(mm, start, end);
-       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, dirty_accountable);
-       mmu_notifier_invalidate_range_end(mm, start, end);
+       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);
        perf_event_mmap(vma);