[PATCH 08/10] mm/hugetlb: Make walk_hugetlb_range() safe to pmd unshare

[Peter Xu]

Since walk_hugetlb_range() 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@xxxxxxxxxx>
---
 mm/pagewalk.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 7f1c9b274906..d98564a7be57 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -302,6 +302,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 	const struct mm_walk_ops *ops = walk->ops;
 	int err = 0;
 
+	hugetlb_vma_lock_read(vma);
 	do {
 		next = hugetlb_entry_end(h, addr, end);
 		pte = huge_pte_offset(walk->mm, addr & hmask, sz);
@@ -314,6 +315,7 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
 		if (err)
 			break;
 	} while (addr = next, addr != end);
+	hugetlb_vma_unlock_read(vma);
 
 	return err;
 }
-- 
2.37.3