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    SubjectRe: [PATCH 2/6] mm: mlocking in try_to_unmap_one
    Date
    > @@ -787,6 +787,8 @@ static int try_to_unmap_one(struct page
    > ret = SWAP_MLOCK;
    > goto out_unmap;
    > }
    > + if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK)
    > + goto out_unmap;
    > }
    > if (!(flags & TTU_IGNORE_ACCESS)) {
    > if (ptep_clear_flush_young_notify(vma, address, pte)) {
    > @@ -852,12 +854,22 @@ static int try_to_unmap_one(struct page
    > } else
    > dec_mm_counter(mm, file_rss);
    >
    > -
    > page_remove_rmap(page);
    > page_cache_release(page);
    >
    > out_unmap:
    > pte_unmap_unlock(pte, ptl);
    > +
    > + if (MLOCK_PAGES && ret == SWAP_MLOCK) {
    > + ret = SWAP_AGAIN;
    > + if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
    > + if (vma->vm_flags & VM_LOCKED) {
    > + mlock_vma_page(page);
    > + ret = SWAP_MLOCK;
    > + }
    > + up_read(&vma->vm_mm->mmap_sem);
    > + }
    > + }
    > out:

    Very small nit. How about this?


    ------------------------------------------------------------
    From 9d4b507572eccf88dcaa02e650df59874216528c Mon Sep 17 00:00:00 2001
    From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Date: Fri, 13 Nov 2009 15:00:04 +0900
    Subject: [PATCH] Simplify try_to_unmap_one()

    SWAP_MLOCK mean "We marked the page as PG_MLOCK, please move it to
    unevictable-lru". So, following code is easy confusable.

    if (vma->vm_flags & VM_LOCKED) {
    ret = SWAP_MLOCK;
    goto out_unmap;
    }

    Plus, if the VMA doesn't have VM_LOCKED, We don't need to check
    the needed of calling mlock_vma_page().

    Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    ---
    mm/rmap.c | 25 ++++++++++++-------------
    1 files changed, 12 insertions(+), 13 deletions(-)

    diff --git a/mm/rmap.c b/mm/rmap.c
    index 4440a86..81a168c 100644
    --- a/mm/rmap.c
    +++ b/mm/rmap.c
    @@ -784,10 +784,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
    * skipped over this mm) then we should reactivate it.
    */
    if (!(flags & TTU_IGNORE_MLOCK)) {
    - if (vma->vm_flags & VM_LOCKED) {
    - ret = SWAP_MLOCK;
    - goto out_unmap;
    - }
    + if (vma->vm_flags & VM_LOCKED)
    + goto out_unlock;
    if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK)
    goto out_unmap;
    }
    @@ -856,18 +854,19 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,

    out_unmap:
    pte_unmap_unlock(pte, ptl);
    +out:
    + return ret;

    - if (MLOCK_PAGES && ret == SWAP_MLOCK) {
    - ret = SWAP_AGAIN;
    - if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
    - if (vma->vm_flags & VM_LOCKED) {
    - mlock_vma_page(page);
    - ret = SWAP_MLOCK;
    - }
    - up_read(&vma->vm_mm->mmap_sem);
    +out_unlock:
    + pte_unmap_unlock(pte, ptl);
    +
    + if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
    + if (vma->vm_flags & VM_LOCKED) {
    + mlock_vma_page(page);
    + ret = SWAP_MLOCK;
    }
    + up_read(&vma->vm_mm->mmap_sem);
    }
    -out:
    return ret;
    }

    --
    1.6.2.5






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