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

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Since follow_hugetlb_page() 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/20221216155223.2043727-1-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 10:52:23 -05:00 committed by Andrew Morton
parent 7d049f3a03
commit eefc7fa536
1 changed files with 7 additions and 0 deletions
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7
mm/hugetlb.c
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@ -6454,6 +6454,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
break;
}
hugetlb_vma_lock_read(vma);
/*
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make sure we get the
@ -6478,6 +6479,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
!hugetlbfs_pagecache_present(h, vma, vaddr)) {
if (pte)
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
remainder = 0;
break;
}
@ -6499,6 +6501,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (pte)
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
if (flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
else if (unshare)
@ -6561,6 +6565,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
remainder -= pages_per_huge_page(h);
i += pages_per_huge_page(h);
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
continue;
}
@ -6590,6 +6595,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs,
flags))) {
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
remainder = 0;
err = -ENOMEM;
break;
@ -6601,6 +6607,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
i += refs;
spin_unlock(ptl);
hugetlb_vma_unlock_read(vma);
}
*nr_pages = remainder;
/*