[patch 04/18] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active

From: Muchun Song <redacted>
Subject: mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active

The page_huge_active() can be called from scan_movable_pages() which do
not hold a reference count to the HugeTLB page.  So when we call
page_huge_active() from scan_movable_pages(), the HugeTLB page can be
freed parallel.  Then we will trigger a BUG_ON which is in the
page_huge_active() when CONFIG_DEBUG_VM is enabled.  Just remove the
VM_BUG_ON_PAGE.

Link: https://lkml.kernel.org/r/20210115124942.46403-6-songmuchun@bytedance.com
Fixes: 7e1f049efb86 ("mm: hugetlb: cleanup using paeg_huge_active()")
Signed-off-by: Muchun Song <redacted>
Reviewed-by: Mike Kravetz <redacted>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <redacted>
Cc: Yang Shi <redacted>
Cc: <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-remove-vm_bug_on_page-from-page_huge_active
+++ a/mm/hugetlb.c

@@ -1361,8 +1361,7 @@ struct hstate *size_to_hstate(unsigned l
  */
 bool page_huge_active(struct page *page)
 {
-	VM_BUG_ON_PAGE(!PageHuge(page), page);
-	return PageHead(page) && PagePrivate(&page[1]);
+	return PageHeadHuge(page) && PagePrivate(&page[1]);
 }
 
 /* never called for tail page */

_