[PATCH v20 12/18] x86/resctrl: Create Sub-NUMA Cluster (SNC) monitor files

[Tony Luck <tony.luck@intel.com>]

When SNC mode is enabled, create subdirectories and files to monitor
at the SNC node granularity. Legacy behavior is preserved by tagging
the monitor files at the L3 granularity with the "sum" attribute.
When the user reads these files the kernel will read monitor data
from all SNC nodes that share the same L3 cache instance and return
the aggregated value to the user.

Note that the "domid" field for files that must sum across SNC domains
has the L3 cache instance id, while non-summing files use the domain id.

The "sum" files do not need to make a call to mon_event_read() to
initialize the MBM counters. This will be handled by initializing the
individual SNC nodes that share the L3.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 62 +++++++++++++++++++-------
 1 file changed, 46 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 66acbad1c585..fc7f3f139800 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3022,7 +3022,8 @@ 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 rdt_resource *r, struct rdtgroup *prgrp,
+			     bool do_sum)
 {
 	union mon_data_bits priv;
 	struct mon_evt *mevt;
@@ -3033,14 +3034,15 @@ static int mon_add_all_files(struct kernfs_node *kn, struct rdt_mon_domain *d,
 		return -EPERM;
 
 	priv.u.rid = r->rid;
-	priv.u.domid = d->hdr.id;
+	priv.u.domid = do_sum ? d->ci->id : d->hdr.id;
+	priv.u.sum = do_sum;
 	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))
+		if (!do_sum && is_mbm_event(mevt->evtid))
 			mon_event_read(&rr, r, d, prgrp, mevt->evtid, true);
 	}
 
@@ -3051,23 +3053,51 @@ static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
 				struct rdt_mon_domain *d,
 				struct rdt_resource *r, struct rdtgroup *prgrp)
 {
-	struct kernfs_node *kn;
+	struct kernfs_node *kn, *ckn;
 	char name[32];
-	int ret;
+	bool snc_mode;
+	int ret = 0;
 
-	sprintf(name, "mon_%s_%02d", r->name, d->hdr.id);
-	/* create the directory */
-	kn = kernfs_create_dir(parent_kn, name, parent_kn->mode, prgrp);
-	if (IS_ERR(kn))
-		return PTR_ERR(kn);
+	lockdep_assert_held(&rdtgroup_mutex);
 
-	ret = rdtgroup_kn_set_ugid(kn);
-	if (ret)
-		goto out_destroy;
+	snc_mode = r->mon_scope != RESCTRL_L3_CACHE;
+	sprintf(name, "mon_%s_%02d", r->name, d->ci->id);
+	kn = kernfs_find_and_get(parent_kn, name);
+	if (kn) {
+		/*
+		 * rdtgroup_mutex will prevent this directory from being
+		 * removed. No need to keep this hold.
+		 */
+		kernfs_put(kn);
+	} else {
+		kn = kernfs_create_dir(parent_kn, name, parent_kn->mode, prgrp);
+		if (IS_ERR(kn))
+			return PTR_ERR(kn);
 
-	ret = mon_add_all_files(kn, d, r, prgrp);
-	if (ret)
-		goto out_destroy;
+		ret = rdtgroup_kn_set_ugid(kn);
+		if (ret)
+			goto out_destroy;
+		ret = mon_add_all_files(kn, d, r, prgrp, snc_mode);
+		if (ret)
+			goto out_destroy;
+	}
+
+	if (snc_mode) {
+		sprintf(name, "mon_sub_%s_%02d", r->name, d->hdr.id);
+		ckn = kernfs_create_dir(kn, name, parent_kn->mode, prgrp);
+		if (IS_ERR(ckn)) {
+			ret = -EINVAL;
+			goto out_destroy;
+		}
+
+		ret = rdtgroup_kn_set_ugid(ckn);
+		if (ret)
+			goto out_destroy;
+
+		ret = mon_add_all_files(ckn, d, r, prgrp, false);
+		if (ret)
+			goto out_destroy;
+	}
 
 	kernfs_activate(kn);
 	return 0;
-- 
2.45.0