[PATCH 06/10] mm/hugetlb: Make hugetlb_follow_page_mask() safe to pmd unshare

Peter Xu
2022-11-29T19:38:58Z

Since hugetlb_follow_page_mask() 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@redhat.com>
---
mm/hugetlb.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 776e34ccf029..d6bb1d22f1c4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6232,9 +6232,10 @@ 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);
@@ -6257,6 +6258,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
}
out:
spin_unlock(ptl);
+out_unlock:
+ hugetlb_vma_unlock_read(vma);
return page;
}

--
2.37.3