cifs: Ratelimit kernel log messages

Under some conditions, CIFS can repeatedly call the cifs_dbg() logging
wrapper. If done rapidly enough, the console framebuffer can softlockup
or "rcu_sched self-detected stall". Apply the built-in log ratelimiters
to prevent such hangs.

Signed-off-by: Jamie Bainbridge <jamie.bainbridge@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
CC: Stable <stable@vger.kernel.org>

fs/cifs/cifs_debug.c

@@ -50,7 +50,7 @@ void cifs_vfs_err(const char *fmt, ...)
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	pr_err("CIFS VFS: %pV", &vaf);
+	pr_err_ratelimited("CIFS VFS: %pV", &vaf);
 
 	va_end(args);
 }