linux-kernel - [PATCH RFC v2 09/12] mm/hugetlb: Use hugetlb walker lock in hugetlb_vma_maps

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Message-Id: <20221118011025.2178986-10-peterx@redhat.com>
Date:   Thu, 17 Nov 2022 20:10:22 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Rik van Riel <riel@...riel.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>, peterx@...hat.com,
        James Houghton <jthoughton@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH RFC v2 09/12] mm/hugetlb: Use hugetlb walker lock in hugetlb_vma_maps_page()

Hugetlb walker lock makes sure the pte_t* won't go away from under us.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 fs/hugetlbfs/inode.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index fdb16246f46e..265508981ba1 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -387,21 +387,24 @@ static bool hugetlb_vma_maps_page(struct vm_area_struct *vma,
 				unsigned long addr, struct page *page)
 {
 	pte_t *ptep, pte;
+	bool result = false;
 
+	hugetlb_walker_lock();
 	ptep = huge_pte_offset(vma->vm_mm, addr,
 			huge_page_size(hstate_vma(vma)));
 
 	if (!ptep)
-		return false;
+		goto out;
 
 	pte = huge_ptep_get(ptep);
 	if (huge_pte_none(pte) || !pte_present(pte))
-		return false;
+		goto out;
 
 	if (pte_page(pte) == page)
-		return true;
-
-	return false;
+		result = true;
+out:
+	hugetlb_walker_unlock();
+	return result;
 }
 
 /*
-- 
2.37.3