linux-kernel - [PATCH 08/10] mm/hugetlb: Make walk_hugetlb

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Message-Id: <20221129193526.3588187-9-peterx@redhat.com>
Date:   Tue, 29 Nov 2022 14:35:24 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     James Houghton <jthoughton@...gle.com>,
        Jann Horn <jannh@...gle.com>, peterx@...hat.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        David Hildenbrand <david@...hat.com>
Subject: [PATCH 08/10] mm/hugetlb: Make walk_hugetlb_range() safe to pmd unshare

Since walk_hugetlb_range() walks the pgtable, it needs the vma lock
to make sure the pgtable page will not be freed concurrently.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/pagewalk.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 7f1c9b274906..d98564a7be57 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -302,6 +302,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
+	hugetlb_vma_lock_read(vma);
 	do {
 		next = hugetlb_entry_end(h, addr, end);
 		pte = huge_pte_offset(walk->mm, addr & hmask, sz);
@@ -314,6 +315,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 		if (err)
 			break;
 	} while (addr = next, addr != end);
+	hugetlb_vma_unlock_read(vma);
 
 	return err;
 }
-- 
2.37.3