[PATCH 1/4] mm: Assert the mmap_lock is held in __anon_vma_prepare()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Convert the comment into an assertion.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/rmap.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 2608c40dffad..619d4d65d99b 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -182,8 +182,6 @@ static void anon_vma_chain_link(struct vm_area_struct *vma,
  * for the new allocation. At the same time, we do not want
  * to do any locking for the common case of already having
  * an anon_vma.
- *
- * This must be called with the mmap_lock held for reading.
  */
 int __anon_vma_prepare(struct vm_area_struct *vma)
 {
@@ -191,6 +189,7 @@ int __anon_vma_prepare(struct vm_area_struct *vma)
 	struct anon_vma *anon_vma, *allocated;
 	struct anon_vma_chain *avc;
 
+	mmap_assert_locked(mm);
 	might_sleep();
 
 	avc = anon_vma_chain_alloc(GFP_KERNEL);
-- 
2.43.0