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mm/hugetlb: make hugetlb_follow_page_mask() safe to pmd unshare

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

Link: https://lkml.kernel.org/r/20221216155219.2043714-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2022-12-16 10:52:19 -05:00 committed by Andrew Morton
parent b8da2e4660
commit 7d049f3a03
1 changed files with 4 additions and 1 deletions
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5
mm/hugetlb.c
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@ -6396,9 +6396,10 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
hugetlb_vma_lock_read(vma);
pte = huge_pte_offset(mm, haddr, huge_page_size(h));
if (!pte)
return NULL;
goto out_unlock;
ptl = huge_pte_lock(h, mm, pte);
entry = huge_ptep_get(pte);
@ -6421,6 +6422,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
}
out:
spin_unlock(ptl);
out_unlock:
hugetlb_vma_unlock_read(vma);
return page;
}