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mm: Count the number of pages affected in change_protection()
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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>
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Peter Zijlstra authored and Mel Gorman committed Dec 11, 2012
1 parent 4fd0177 commit 7da4d64
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Showing 4 changed files with 61 additions and 18 deletions.
8 changes: 6 additions & 2 deletions include/linux/hugetlb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down Expand Up @@ -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,
Expand Down
3 changes: 3 additions & 0 deletions include/linux/mm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down
10 changes: 8 additions & 2 deletions mm/hugetlb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3014,14 +3014,15 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
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;
unsigned long start = address;
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);
Expand All @@ -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);
Expand All @@ -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,
Expand Down
58 changes: 44 additions & 14 deletions mm/mprotect.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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();
Expand All @@ -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);

Expand All @@ -72,61 +74,73 @@ 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 {
next = pmd_addr_end(addr, end);
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)
{
struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
unsigned long next;
unsigned long start = addr;
unsigned long pages = 0;

BUG_ON(addr >= end);
pgd = pgd_offset(mm, addr);
Expand All @@ -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
Expand Down Expand Up @@ -213,12 +247,8 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
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);
Expand Down

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