When unmapping VM_HUGETLB mappings, vm flags need to be updated. Since
the vmas have been detached, so it sounds safe to update vm flags with
read mmap_sem.

Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <redacted>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Yang Shi <redacted>
---
 mm/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 982dd00..490340e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c

@@ -2777,7 +2777,7 @@ static int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 			 * update vm_flags.
 			 */
 			if (downgrade &&
-			    (tmp->vm_flags & (VM_HUGETLB | VM_PFNMAP)))
+			    (tmp->vm_flags & VM_PFNMAP))
 				downgrade = false;
 
 			tmp = tmp->vm_next;

-- 
1.8.3.1