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mm: simplify try_to_unmap_one()

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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().

Also, add some commentary to try_to_unmap_one().

Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KOSAKI Motohiro 2009-12-14 17:59:45 -08:00 committed by Linus Torvalds
parent 23ce932a5e
commit caed0f486e
1 changed files with 24 additions and 15 deletions
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39
mm/rmap.c
View file

@ -789,10 +789,9 @@ 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_mlock;
if (TTU_ACTION(flags) == TTU_MUNLOCK)
goto out_unmap;
}
@ -865,19 +864,29 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
out_unmap:
pte_unmap_unlock(pte, ptl);
if (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:
return ret;
out_mlock:
pte_unmap_unlock(pte, ptl);
/*
* We need mmap_sem locking, Otherwise VM_LOCKED check makes
* unstable result and race. Plus, We can't wait here because
* we now hold anon_vma->lock or mapping->i_mmap_lock.
* if trylock failed, the page remain in evictable lru and later
* vmscan could retry to move the page to unevictable lru if the
* page is actually mlocked.
*/
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);
}
return ret;
}
/*