From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/mlock: stop counting mlocked pages when none vma is found

There will be no vma satisfies addr < vm_end when find_vma() returns NULL.
Thus it's meaningless to traverse the vma list below because we can't
find any vma to count mlocked pages.  Stop counting mlocked pages in this
case to save some vma list traversal cycles.

Link: https://lkml.kernel.org/r/20210204110705.17586-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mlock.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/mlock.c~mm-mlock-stop-counting-mlocked-pages-when-none-vma-is-found
+++ a/mm/mlock.c

@@ -622,7 +622,7 @@ static unsigned long count_mm_mlocked_pa
 
 	vma = find_vma(mm, start);
 	if (vma == NULL)
-		vma = mm->mmap;
+		return 0;
 
 	for (; vma ; vma = vma->vm_next) {
 		if (start >= vma->vm_end)

_