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

KOSAKI Motohiro
2009-11-13T06:30:15Z

> @@ -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