Messages in this thread | | | Date | Wed, 7 Dec 2022 15:25:59 -0800 | Subject | Re: [PATCH v2 07/10] mm/hugetlb: Make follow_hugetlb_page() safe to pmd unshare | From | John Hubbard <> |
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On 12/7/22 12:30, Peter Xu wrote: > Since follow_hugetlb_page() walks the pgtable, it needs the vma lock > to make sure the pgtable page will not be freed concurrently. > > Acked-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > mm/hugetlb.c | 7 +++++++ > 1 file changed, 7 insertions(+)
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
thanks, -- John Hubbard NVIDIA
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 3fbbd599d015..f42399522805 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6284,6 +6284,7 @@ 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 > @@ -6308,6 +6309,7 @@ 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; > } > @@ -6329,6 +6331,8 @@ 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) > @@ -6388,6 +6392,7 @@ 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; > } > > @@ -6415,6 +6420,7 @@ 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; > @@ -6426,6 +6432,7 @@ 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; > /*
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