RCU makes sure the pte_t* won't go away from under us. Please refer to the comment above huge_pte_offset() for more information. Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- mm/hugetlb.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 9869c12e6460..85214095fb85 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6229,10 +6229,12 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, if (WARN_ON_ONCE(flags & FOLL_PIN)) return NULL; + /* For huge_pte_offset() */ + rcu_read_lock(); retry: pte = huge_pte_offset(mm, haddr, huge_page_size(h)); if (!pte) - return NULL; + goto out_rcu; ptl = huge_pte_lock(h, mm, pte); entry = huge_ptep_get(pte); @@ -6266,6 +6268,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, } out: spin_unlock(ptl); +out_rcu: + rcu_read_unlock(); return page; } -- 2.37.3
