Re: [PATCH 2/6] mm: mlocking in try_to_unmap_one

Hugh Dickins
2009-11-15T22:17:00Z

On Fri, 13 Nov 2009, KOSAKI Motohiro wrote:
>
> Very small nit. How about this?

Yes, that takes it a stage further, I prefer that, thanks: but better
redo against mmotm, I removed the "MLOCK_PAGES && " in a later patch.

Hugh

>
>
> ------------------------------------------------------------
> 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