--- x/mm/mmap.c
+++ y/mm/mmap.c
@@ -2657,8 +2657,6 @@ do_vmi_align_munmap(struct vma_iterator
 	/* Point of no return */
 	mm->locked_vm -= locked_vm;
 	mm->map_count -= count;
-	if (unlock)
-		mmap_write_downgrade(mm);
 
 	prev = vma_iter_prev_range(vmi);
 	next = vma_next(vmi);
@@ -2677,7 +2675,7 @@ do_vmi_align_munmap(struct vma_iterator
 	remove_mt(mm, &mas_detach);
 	validate_mm(mm);
 	if (unlock)
-		mmap_read_unlock(mm);
+		mmap_write_unlock(mm);
 
 	__mt_destroy(&mt_detach);
 	return 0;