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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2009-12-14 17:59:45 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-15 08:53:20 -0800
commitcaed0f486e582eeeb6e3546417fd758230fe4ad9 (patch)
tree203d4724dcfaae3ad4b349e1971bb3efc0da7db2 /mm/rmap.c
parent23ce932a5e3ec3b9f06e92c8797d834d43abfb0f (diff)
mm: 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(). 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>
Diffstat (limited to 'mm/rmap.c')
-rw-r--r--mm/rmap.c35
1 files changed, 22 insertions, 13 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index c81bedd7d527..98135dbd25ba 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -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;
}
@@ -865,18 +864,28 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
out_unmap:
pte_unmap_unlock(pte, ptl);
+out:
+ return ret;
- 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_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);
}
-out:
return ret;
}

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