x86/resctrl: Refactor mkdir_mondata_subdir() with a helper function

In Sub-NUMA Cluster (SNC) mode Linux must create the monitor
files in the original "mon_L3_XX" directories and also in each
of the "mon_sub_L3_YY" directories.

Refactor mkdir_mondata_subdir() to move the creation of monitoring files
into a helper function to avoid the need to duplicate code later.

No functional change.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20240628215619.76401-12-tony.luck@intel.com

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -3025,14 +3025,37 @@ static void rmdir_mondata_subdir_allrdtgrp(struct rdt_resource *r,
 	}
 }
 
+static int mon_add_all_files(struct kernfs_node *kn, struct rdt_mon_domain *d,
+			     struct rdt_resource *r, struct rdtgroup *prgrp)
+{
+	struct rmid_read rr = {0};
+	union mon_data_bits priv;
+	struct mon_evt *mevt;
+	int ret;
+
+	if (WARN_ON(list_empty(&r->evt_list)))
+		return -EPERM;
+
+	priv.u.rid = r->rid;
+	priv.u.domid = d->hdr.id;
+	list_for_each_entry(mevt, &r->evt_list, list) {
+		priv.u.evtid = mevt->evtid;
+		ret = mon_addfile(kn, mevt->name, priv.priv);
+		if (ret)
+			return ret;
+
+		if (is_mbm_event(mevt->evtid))
+			mon_event_read(&rr, r, d, prgrp, mevt->evtid, true);
+	}
+
+	return 0;
+}
+
 static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
 				struct rdt_mon_domain *d,
 				struct rdt_resource *r, struct rdtgroup *prgrp)
 {
-	struct rmid_read rr = {0};
-	union mon_data_bits priv;
 	struct kernfs_node *kn;
-	struct mon_evt *mevt;
 	char name[32];
 	int ret;
 
@@ -3046,22 +3069,10 @@ static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
 	if (ret)
 		goto out_destroy;
 
-	if (WARN_ON(list_empty(&r->evt_list))) {
-		ret = -EPERM;
+	ret = mon_add_all_files(kn, d, r, prgrp);
+	if (ret)
 		goto out_destroy;
-	}
 
-	priv.u.rid = r->rid;
-	priv.u.domid = d->hdr.id;
-	list_for_each_entry(mevt, &r->evt_list, list) {
-		priv.u.evtid = mevt->evtid;
-		ret = mon_addfile(kn, mevt->name, priv.priv);
-		if (ret)
-			goto out_destroy;
-
-		if (is_mbm_event(mevt->evtid))
-			mon_event_read(&rr, r, d, prgrp, mevt->evtid, true);
-	}
 	kernfs_activate(kn);
 	return 0;