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Subject[RFC][PATCH v2 3/8] VM_LOCKED check don't need pte lock
Date
Currently, page_referenced_one() check VM_LOCKED after taking ptelock.
But it's unnecessary. We can check VM_LOCKED before to take lock.

This patch does it.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
---
mm/rmap.c | 13 ++++++-------
1 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 1b50425..fb0983a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -383,21 +383,21 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
spinlock_t *ptl;
int referenced = 0;

- pte = page_check_address(page, mm, address, &ptl, 0);
- if (!pte)
- goto out;
-
/*
* Don't want to elevate referenced for mlocked page that gets this far,
* in order that it progresses to try_to_unmap and is moved to the
* unevictable list.
*/
if (vma->vm_flags & VM_LOCKED) {
- *mapcount = 1; /* break early from loop */
+ *mapcount = 0; /* break early from loop */
*vm_flags |= VM_LOCKED;
- goto out_unmap;
+ goto out;
}

+ pte = page_check_address(page, mm, address, &ptl, 0);
+ if (!pte)
+ goto out;
+
if (ptep_clear_flush_young_notify(vma, address, pte)) {
/*
* Don't treat a reference through a sequentially read
@@ -416,7 +416,6 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
rwsem_is_locked(&mm->mmap_sem))
referenced++;

-out_unmap:
(*mapcount)--;
pte_unmap_unlock(pte, ptl);

--
1.6.5.2




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