fs/resctrl: Refactor mkdir_mondata_subdir()

Population of a monitor group's mon_data directory is unreasonably complicated
because of the support for Sub-NUMA Cluster (SNC) mode.

Split out the SNC code into a helper function to make it easier to add support
for a new telemetry resource.

Move all the duplicated code to make and set owner of domain directories into
the mon_add_all_files() helper and rename to _mkdir_mondata_subdir().

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
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>
Link: https://lore.kernel.org/20251217172121.12030-1-tony.luck@intel.com

Author: aegl

fs/resctrl/rdtgroup.c

@@ -3260,57 +3260,65 @@ static void rmdir_mondata_subdir_allrdtgrp(struct rdt_resource *r,
 	}
 }
 
-static int mon_add_all_files(struct kernfs_node *kn, struct rdt_domain_hdr *hdr,
-			     struct rdt_resource *r, struct rdtgroup *prgrp,
-			     bool do_sum)
+/*
+ * Create a directory for a domain and populate it with monitor files. Create
+ * summing monitors when @hdr is NULL. No need to initialize summing monitors.
+ */
+static struct kernfs_node *_mkdir_mondata_subdir(struct kernfs_node *parent_kn, char *name,
+						 struct rdt_domain_hdr *hdr,
+						 struct rdt_resource *r,
+						 struct rdtgroup *prgrp, int domid)
 {
-	struct rdt_l3_mon_domain *d;
 	struct rmid_read rr = {0};
+	struct kernfs_node *kn;
 	struct mon_data *priv;
 	struct mon_evt *mevt;
-	int ret, domid;
+	int ret;
 
-	if (!domain_header_is_valid(hdr, RESCTRL_MON_DOMAIN, RDT_RESOURCE_L3))
-		return -EINVAL;
+	kn = kernfs_create_dir(parent_kn, name, parent_kn->mode, prgrp);
+	if (IS_ERR(kn))
+		return kn;
+
+	ret = rdtgroup_kn_set_ugid(kn);
+	if (ret)
+		goto out_destroy;
 
-	d = container_of(hdr, struct rdt_l3_mon_domain, hdr);
 	for_each_mon_event(mevt) {
 		if (mevt->rid != r->rid || !mevt->enabled)
 			continue;
-		domid = do_sum ? d->ci_id : d->hdr.id;
-		priv = mon_get_kn_priv(r->rid, domid, mevt, do_sum);
-		if (WARN_ON_ONCE(!priv))
-			return -EINVAL;
+		priv = mon_get_kn_priv(r->rid, domid, mevt, !hdr);
+		if (WARN_ON_ONCE(!priv)) {
+			ret = -EINVAL;
+			goto out_destroy;
+		}
 
 		ret = mon_addfile(kn, mevt->name, priv);
 		if (ret)
-			return ret;
+			goto out_destroy;
 
-		if (!do_sum && resctrl_is_mbm_event(mevt->evtid))
+		if (hdr && resctrl_is_mbm_event(mevt->evtid))
 			mon_event_read(&rr, r, hdr, prgrp, &hdr->cpu_mask, mevt, true);
 	}
 
-	return 0;
+	return kn;
+out_destroy:
+	kernfs_remove(kn);
+	return ERR_PTR(ret);
 }
 
-static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
-				struct rdt_domain_hdr *hdr,
-				struct rdt_resource *r, struct rdtgroup *prgrp)
+static int mkdir_mondata_subdir_snc(struct kernfs_node *parent_kn,
+				    struct rdt_domain_hdr *hdr,
+				    struct rdt_resource *r, struct rdtgroup *prgrp)
 {
-	struct kernfs_node *kn, *ckn;
+	struct kernfs_node *ckn, *kn;
 	struct rdt_l3_mon_domain *d;
 	char name[32];
-	bool snc_mode;
-	int ret = 0;
-
-	lockdep_assert_held(&rdtgroup_mutex);
 
 	if (!domain_header_is_valid(hdr, RESCTRL_MON_DOMAIN, RDT_RESOURCE_L3))
 		return -EINVAL;
 
 	d = container_of(hdr, struct rdt_l3_mon_domain, hdr);
-	snc_mode = r->mon_scope == RESCTRL_L3_NODE;
-	sprintf(name, "mon_%s_%02d", r->name, snc_mode ? d->ci_id : d->hdr.id);
+	sprintf(name, "mon_%s_%02d", r->name, d->ci_id);
 	kn = kernfs_find_and_get(parent_kn, name);
 	if (kn) {
 		/*
@@ -3319,41 +3327,41 @@ static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
 		 */
 		kernfs_put(kn);
 	} else {
-		kn = kernfs_create_dir(parent_kn, name, parent_kn->mode, prgrp);
+		kn = _mkdir_mondata_subdir(parent_kn, name, NULL, r, prgrp, d->ci_id);
 		if (IS_ERR(kn))
 			return PTR_ERR(kn);
+	}
 
-		ret = rdtgroup_kn_set_ugid(kn);
-		if (ret)
-			goto out_destroy;
-		ret = mon_add_all_files(kn, hdr, r, prgrp, snc_mode);
-		if (ret)
-			goto out_destroy;
+	sprintf(name, "mon_sub_%s_%02d", r->name, hdr->id);
+	ckn = _mkdir_mondata_subdir(kn, name, hdr, r, prgrp, hdr->id);
+	if (IS_ERR(ckn)) {
+		kernfs_remove(kn);
+		return PTR_ERR(ckn);
 	}
 
-	if (snc_mode) {
-		sprintf(name, "mon_sub_%s_%02d", r->name, hdr->id);
-		ckn = kernfs_create_dir(kn, name, parent_kn->mode, prgrp);
-		if (IS_ERR(ckn)) {
-			ret = -EINVAL;
-			goto out_destroy;
-		}
+	kernfs_activate(kn);
+	return 0;
+}
 
-		ret = rdtgroup_kn_set_ugid(ckn);
-		if (ret)
-			goto out_destroy;
+static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
+				struct rdt_domain_hdr *hdr,
+				struct rdt_resource *r, struct rdtgroup *prgrp)
+{
+	struct kernfs_node *kn;
+	char name[32];
 
-		ret = mon_add_all_files(ckn, hdr, r, prgrp, false);
-		if (ret)
-			goto out_destroy;
-	}
+	lockdep_assert_held(&rdtgroup_mutex);
+
+	if (r->rid == RDT_RESOURCE_L3 && r->mon_scope == RESCTRL_L3_NODE)
+		return mkdir_mondata_subdir_snc(parent_kn, hdr, r, prgrp);
+
+	sprintf(name, "mon_%s_%02d", r->name, hdr->id);
+	kn = _mkdir_mondata_subdir(parent_kn, name, hdr, r, prgrp, hdr->id);
+	if (IS_ERR(kn))
+		return PTR_ERR(kn);
 
 	kernfs_activate(kn);
 	return 0;
-
-out_destroy:
-	kernfs_remove(kn);
-	return ret;
 }
 
 /*