[PATCH RFC 05/10] mm/hugetlb: Make walk_hugetlb_range() RCU-safe

[Peter Xu <peterx@redhat.com>]

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>
---
 mm/pagewalk.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 7f1c9b274906..bbc71c750576 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -302,6 +302,9 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
+	/* For huge_pte_offset() */
+	rcu_read_lock();
+
 	do {
 		next = hugetlb_entry_end(h, addr, end);
 		pte = huge_pte_offset(walk->mm, addr & hmask, sz);
@@ -315,6 +318,8 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 			break;
 	} while (addr = next, addr != end);
 
+	rcu_read_unlock();
+
 	return err;
 }
 
-- 
2.37.3