[PATCH RFC 03/10] mm/hugetlb: Make hugetlb_vma_maps_page() RCU-safe

Peter Xu
2022-10-30T21:30:46Z

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@redhat.com>
---
fs/hugetlbfs/inode.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index ac3a69fe29c3..b9e7825079c7 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -387,21 +387,26 @@ static bool hugetlb_vma_maps_page(struct vm_area_struct *vma,
unsigned long addr, struct page *page)
{
pte_t *ptep, pte;
+ bool result = false;
+
+ /* For huge_pte_offset() */
+ rcu_read_lock();

ptep = huge_pte_offset(vma->vm_mm, addr,
huge_page_size(hstate_vma(vma)));

if (!ptep)
- return false;
+ goto out;

pte = huge_ptep_get(ptep);
if (huge_pte_none(pte) || !pte_present(pte))
- return false;
+ goto out;

if (pte_page(pte) == page)
- return true;
-
- return false;
+ result = true;
+out:
+ rcu_read_unlock();
+ return result;
}

/*
--
2.37.3