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    Subject[PATCH 3/6] mm: msync() cleanup

    From: Peter Zijlstra <a.p.zijlstra@chello.nl>

    With the tracking of dirty pages properly done now, msync doesn't need to
    scan the PTEs anymore to determine the dirty status.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

    mm/msync.c | 129 ++++---------------------------------------------------------
    1 file changed, 9 insertions(+), 120 deletions(-)

    Index: 2.6-mm/mm/msync.c
    ===================================================================
    --- 2.6-mm.orig/mm/msync.c 2006-06-19 16:21:13.000000000 +0200
    +++ 2.6-mm/mm/msync.c 2006-06-19 16:21:21.000000000 +0200
    @@ -20,109 +20,14 @@
    #include <asm/pgtable.h>
    #include <asm/tlbflush.h>

    -static unsigned long msync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
    - unsigned long addr, unsigned long end)
    -{
    - pte_t *pte;
    - spinlock_t *ptl;
    - int progress = 0;
    - unsigned long ret = 0;
    -
    -again:
    - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
    - do {
    - struct page *page;
    -
    - if (progress >= 64) {
    - progress = 0;
    - if (need_resched() || need_lockbreak(ptl))
    - break;
    - }
    - progress++;
    - if (!pte_present(*pte))
    - continue;
    - if (!pte_maybe_dirty(*pte))
    - continue;
    - page = vm_normal_page(vma, addr, *pte);
    - if (!page)
    - continue;
    - if (ptep_clear_flush_dirty(vma, addr, pte) ||
    - page_test_and_clear_dirty(page))
    - ret += set_page_dirty(page);
    - progress += 3;
    - } while (pte++, addr += PAGE_SIZE, addr != end);
    - pte_unmap_unlock(pte - 1, ptl);
    - cond_resched();
    - if (addr != end)
    - goto again;
    - return ret;
    -}
    -
    -static inline unsigned long msync_pmd_range(struct vm_area_struct *vma,
    - pud_t *pud, unsigned long addr, unsigned long end)
    -{
    - pmd_t *pmd;
    - unsigned long next;
    - unsigned long ret = 0;
    -
    - pmd = pmd_offset(pud, addr);
    - do {
    - next = pmd_addr_end(addr, end);
    - if (pmd_none_or_clear_bad(pmd))
    - continue;
    - ret += msync_pte_range(vma, pmd, addr, next);
    - } while (pmd++, addr = next, addr != end);
    - return ret;
    -}
    -
    -static inline unsigned long msync_pud_range(struct vm_area_struct *vma,
    - pgd_t *pgd, unsigned long addr, unsigned long end)
    -{
    - pud_t *pud;
    - unsigned long next;
    - unsigned long ret = 0;
    -
    - pud = pud_offset(pgd, addr);
    - do {
    - next = pud_addr_end(addr, end);
    - if (pud_none_or_clear_bad(pud))
    - continue;
    - ret += msync_pmd_range(vma, pud, addr, next);
    - } while (pud++, addr = next, addr != end);
    - return ret;
    -}
    -
    -static unsigned long msync_page_range(struct vm_area_struct *vma,
    - unsigned long addr, unsigned long end)
    -{
    - pgd_t *pgd;
    - unsigned long next;
    - unsigned long ret = 0;
    -
    - /* For hugepages we can't go walking the page table normally,
    - * but that's ok, hugetlbfs is memory based, so we don't need
    - * to do anything more on an msync().
    - */
    - if (vma->vm_flags & VM_HUGETLB)
    - return 0;
    -
    - BUG_ON(addr >= end);
    - pgd = pgd_offset(vma->vm_mm, addr);
    - flush_cache_range(vma, addr, end);
    - do {
    - next = pgd_addr_end(addr, end);
    - if (pgd_none_or_clear_bad(pgd))
    - continue;
    - ret += msync_pud_range(vma, pgd, addr, next);
    - } while (pgd++, addr = next, addr != end);
    - return ret;
    -}
    -
    /*
    * MS_SYNC syncs the entire file - including mappings.
    *
    - * MS_ASYNC does not start I/O (it used to, up to 2.5.67). Instead, it just
    - * marks the relevant pages dirty. The application may now run fsync() to
    + * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
    + * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
    + * Now it doesn't do anything, since dirty pages are properly tracked.
    + *
    + * The application may now run fsync() to
    * write out the dirty pages and wait on the writeout and check the result.
    * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
    * async writeout immediately.
    @@ -130,16 +35,11 @@ static unsigned long msync_page_range(st
    * applications.
    */
    static int msync_interval(struct vm_area_struct *vma, unsigned long addr,
    - unsigned long end, int flags,
    - unsigned long *nr_pages_dirtied)
    + unsigned long end, int flags)
    {
    - struct file *file = vma->vm_file;
    -
    if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))
    return -EBUSY;

    - if (file && (vma->vm_flags & VM_SHARED))
    - *nr_pages_dirtied = msync_page_range(vma, addr, end);
    return 0;
    }

    @@ -178,7 +78,6 @@ asmlinkage long sys_msync(unsigned long
    goto out_unlock;
    }
    do {
    - unsigned long nr_pages_dirtied = 0;
    struct file *file;

    /* Here start < vma->vm_end. */
    @@ -189,8 +88,7 @@ asmlinkage long sys_msync(unsigned long
    /* Here vma->vm_start <= start < vma->vm_end. */
    if (end <= vma->vm_end) {
    if (start < end) {
    - error = msync_interval(vma, start, end, flags,
    - &nr_pages_dirtied);
    + error = msync_interval(vma, start, end, flags);
    if (error)
    goto out_unlock;
    }
    @@ -198,22 +96,13 @@ asmlinkage long sys_msync(unsigned long
    done = 1;
    } else {
    /* Here vma->vm_start <= start < vma->vm_end < end. */
    - error = msync_interval(vma, start, vma->vm_end, flags,
    - &nr_pages_dirtied);
    + error = msync_interval(vma, start, vma->vm_end, flags);
    if (error)
    goto out_unlock;
    }
    file = vma->vm_file;
    start = vma->vm_end;
    - if ((flags & MS_ASYNC) && file && nr_pages_dirtied) {
    - get_file(file);
    - up_read(&current->mm->mmap_sem);
    - balance_dirty_pages_ratelimited_nr(file->f_mapping,
    - nr_pages_dirtied);
    - fput(file);
    - down_read(&current->mm->mmap_sem);
    - vma = find_vma(current->mm, start);
    - } else if ((flags & MS_SYNC) && file &&
    + if ((flags & MS_SYNC) && file &&
    (vma->vm_flags & VM_SHARED)) {
    get_file(file);
    up_read(&current->mm->mmap_sem);
    -
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