hugetlbfs: call VM_BUG_ON_PAGE earlier in free_huge_page()

Yongkai Wu · torvalds · commit 8ace22bce840 · 2018-12-14T15:05:45.000-08:00
A stack trace was triggered by VM_BUG_ON_PAGE(page_mapcount(page), page) in free_huge_page(). Unfortunately, the page->mapping field was set to NULL before this test. This made it more difficult to determine the root cause of the problem. Move the VM_BUG_ON_PAGE tests earlier in the function so that if they do trigger more information is present in the page struct. Link: http://lkml.kernel.org/r/1543491843-23438-1-git-send-email-nic_w@163.com Signed-off-by: Yongkai Wu <nic_w@163.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: William Kucharski <william.kucharski@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
@@ -1248,10 +1248,11 @@ void free_huge_page(struct page *page)
 		(struct hugepage_subpool *)page_private(page);
 	bool restore_reserve;
 
-	set_page_private(page, 0);
-	page->mapping = NULL;
 	VM_BUG_ON_PAGE(page_count(page), page);
 	VM_BUG_ON_PAGE(page_mapcount(page), page);
+
+	set_page_private(page, 0);
+	page->mapping = NULL;
 	restore_reserve = PagePrivate(page);
 	ClearPagePrivate(page);
 
