linux-kernel - [PATCH 4.9 36/43] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge

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Message-Id: <20210208145807.768478692@linuxfoundation.org>
Date:   Mon,  8 Feb 2021 16:01:02 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.9 36/43] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active

From: Muchun Song <songmuchun@...edance.com>

commit ecbf4724e6061b4b01be20f6d797d64d462b2bc8 upstream.

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 <songmuchun@...edance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
Cc: David Hildenbrand <david@...hat.com>
Cc: Yang Shi <shy828301@...il.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/hugetlb.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1210,8 +1210,7 @@ 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 */