In cases when VMA flags are modified after VMA was isolated and mmap_lock
was downgraded, flags modifications do not require per-VMA locking and
an attempt to lock the VMA would result in an assertion because mmap
write lock is not held.
Introduce mod_vm_flags_nolock to be used in such situation.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 include/linux/mm.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2e3be1d45371..7d436a5027cc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -743,6 +743,14 @@ void clear_vm_flags(struct vm_area_struct *vma, unsigned long flags)
 	vma->vm_flags &= ~flags;
 }
 
+static inline
+void mod_vm_flags_nolock(struct vm_area_struct *vma,
+		  unsigned long set, unsigned long clear)
+{
+	vma->vm_flags |= set;
+	vma->vm_flags &= ~clear;
+}
+
 static inline
 void mod_vm_flags(struct vm_area_struct *vma,
 		  unsigned long set, unsigned long clear)

-- 
2.39.0