x86/intel_rdt: Implement show_options() for resctrlfs

Implement show_options() callback for intel resource control filesystem
to expose the active mount options in /proc/

Signed-off-by: Shaohua Li <shli@fb.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/7dce7c1886ac9289442d254ea18322c92bd968da.1480717072.git.shli@fb.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/cpu/intel_rdt_rdtgroup.c

@@ -1036,9 +1036,17 @@ out:
 	return ret;
 }
 
+static int rdtgroup_show_options(struct seq_file *seq, struct kernfs_root *kf)
+{
+	if (rdt_resources_all[RDT_RESOURCE_L3DATA].enabled)
+		seq_puts(seq, ",cdp");
+	return 0;
+}
+
 static struct kernfs_syscall_ops rdtgroup_kf_syscall_ops = {
-	.mkdir	= rdtgroup_mkdir,
-	.rmdir	= rdtgroup_rmdir,
+	.mkdir		= rdtgroup_mkdir,
+	.rmdir		= rdtgroup_rmdir,
+	.show_options	= rdtgroup_show_options,
 };
 
 static int __init rdtgroup_setup_root(void)