linux-kernel - [PATCH v5 5/5] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge

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Date:   Thu, 14 Jan 2021 18:35:15 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     mike.kravetz@...cle.com, akpm@...ux-foundation.org
Cc:     n-horiguchi@...jp.nec.com, ak@...ux.intel.com, mhocko@...e.cz,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>,
        Michal Hocko <mhocko@...e.com>, stable@...r.kernel.org
Subject: [PATCH v5 5/5] 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.

Fixes: 7e1f049efb86 ("mm: hugetlb: cleanup using paeg_huge_active()")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Cc: stable@...r.kernel.org
---
 mm/hugetlb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 43b7a044f248..6c5dfef682cc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1360,8 +1360,7 @@ struct hstate *size_to_hstate(unsigned long size)
  */
 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 */
-- 
2.11.0