diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
index 6618c151288676e94585ceaedc004ba422c27fa0..e278b95984282e894865bfdc9754b84ff0759fad 100644
--- a/include/linux/maple_tree.h
+++ b/include/linux/maple_tree.h
@@ -187,10 +187,13 @@ typedef struct lockdep_map *lockdep_map_p;
 
 #define mt_set_external_lock(mt, lock)					\
 	(mt)->ma_external_lock = &(lock)->dep_map
+
+#define mt_on_stack(mt)			(mt).ma_external_lock = NULL
 #else
 typedef struct { /* nothing */ } lockdep_map_p;
 #define mt_lock_is_held(mt)	1
 #define mt_set_external_lock(mt, lock)	do { } while (0)
+#define mt_on_stack(mt)			do { } while (0)
 #endif
 
 /*
diff --git a/mm/mmap.c b/mm/mmap.c
index cdbeff089049afe0441fe271fe01ed982d8a8cb2..7bd1caa09dddf072ccfe16ec30f38d9fe46a4225 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2428,7 +2428,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	unsigned long locked_vm = 0;
 	MA_STATE(mas_detach, &mt_detach, 0, 0);
 	mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
-	mt_set_external_lock(&mt_detach, &mm->mmap_lock);
+	mt_on_stack(mt_detach);
 
 	/*
 	 * If we need to split any vma, do it now to save pain later.
@@ -2546,11 +2546,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	/* Statistics and freeing VMAs */
 	mas_set(&mas_detach, start);
 	remove_mt(mm, &mas_detach);
-	__mt_destroy(&mt_detach);
 	validate_mm(mm);
 	if (unlock)
 		mmap_read_unlock(mm);
 
+	__mt_destroy(&mt_detach);
 	return 0;
 
 clear_tree_failed: