khugepaged: fix wrong result value for trace_mm_collapse_huge_page_isolate()

[ Upstream commit 74e579bf231a337ab3786d59e64bc94f45ca7b3f ]

In writable and !referenced case, the result value should be
SCAN_LACK_REFERENCED_PAGE for trace_mm_collapse_huge_page_isolate()
instead of default 0 (SCAN_FAIL) here.

Link: https://lkml.kernel.org/r/20210306032947.35921-5-linmiaohe@huawei.com
Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 753b0e2fef3688d977cc425802f573b69d2017ca..0f1bdbae45e21a12dccbf3fb0325b247d7ee3b00 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -596,17 +596,17 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
                    mmu_notifier_test_young(vma->vm_mm, address))
                        referenced++;
        }
-       if (likely(writable)) {
-               if (likely(referenced)) {
-                       result = SCAN_SUCCEED;
-                       trace_mm_collapse_huge_page_isolate(page, none_or_zero,
-                                                           referenced, writable, result);
-                       return 1;
-               }
-       } else {
+
+       if (unlikely(!writable)) {
                result = SCAN_PAGE_RO;
+       } else if (unlikely(!referenced)) {
+               result = SCAN_LACK_REFERENCED_PAGE;
+       } else {
+               result = SCAN_SUCCEED;
+               trace_mm_collapse_huge_page_isolate(page, none_or_zero,
+                                                   referenced, writable, result);
+               return 1;
        }
-
 out:
        release_pte_pages(pte, _pte);
        trace_mm_collapse_huge_page_isolate(page, none_or_zero,