f2fs: add spin_lock to cover radix operations in IO tracer

This patch adds spin_lock to cover radix tree operations in IO tracer.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/trace.h b/fs/f2fs/trace.h
index aa6663b..eb39fa0 100644
--- a/fs/f2fs/trace.h
+++ b/fs/f2fs/trace.h
@@ -34,9 +34,11 @@
 
 extern void f2fs_trace_pid(struct page *);
 extern void f2fs_trace_ios(struct page *, struct f2fs_io_info *, int);
+extern void f2fs_build_trace_ios(void);
 #else
 #define f2fs_trace_pid(p)
 #define f2fs_trace_ios(p, i, n)
+#define f2fs_build_trace_ios()
 
 #endif
 #endif /* __F2FS_TRACE_H__ */