sunrpc: provide multipath info in the sysfs directory

Allow to query xrpt_switch attributes. Currently showing the following
fields of the rpc_xprt_switch structure: xps_nxprts, xps_nactive,
xps_queuelen.
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

net/sunrpc/sysfs.c

@@ -67,6 +67,15 @@ rpc_sysfs_xprt_kobj_get_xprt(struct kobject *kobj)
 	return xprt_get(x->xprt);
 }
 
+static inline struct rpc_xprt_switch *
+rpc_sysfs_xprt_switch_kobj_get_xprt(struct kobject *kobj)
+{
+	struct rpc_sysfs_xprt_switch *x = container_of(kobj,
+		struct rpc_sysfs_xprt_switch, kobject);
+
+	return xprt_switch_get(x->xprt_switch);
+}
+
 static ssize_t rpc_sysfs_xprt_dstaddr_show(struct kobject *kobj,
 					   struct kobj_attribute *attr,
 					   char *buf)
@@ -102,6 +111,23 @@ static ssize_t rpc_sysfs_xprt_info_show(struct kobject *kobj,
 	return ret + 1;
 }
 
+static ssize_t rpc_sysfs_xprt_switch_info_show(struct kobject *kobj,
+					       struct kobj_attribute *attr,
+					       char *buf)
+{
+	struct rpc_xprt_switch *xprt_switch =
+		rpc_sysfs_xprt_switch_kobj_get_xprt(kobj);
+	ssize_t ret;
+
+	if (!xprt_switch)
+		return 0;
+	ret = sprintf(buf, "num_xprts=%u\nnum_active=%u\nqueue_len=%ld\n",
+		      xprt_switch->xps_nxprts, xprt_switch->xps_nactive,
+		      atomic_long_read(&xprt_switch->xps_queuelen));
+	xprt_switch_put(xprt_switch);
+	return ret + 1;
+}
+
 static ssize_t rpc_sysfs_xprt_dstaddr_store(struct kobject *kobj,
 					    struct kobj_attribute *attr,
 					    const char *buf, size_t count)
@@ -235,6 +261,14 @@ static struct attribute *rpc_sysfs_xprt_attrs[] = {
 	NULL,
 };
 
+static struct kobj_attribute rpc_sysfs_xprt_switch_info =
+	__ATTR(xprt_switch_info, 0444, rpc_sysfs_xprt_switch_info_show, NULL);
+
+static struct attribute *rpc_sysfs_xprt_switch_attrs[] = {
+	&rpc_sysfs_xprt_switch_info.attr,
+	NULL,
+};
+
 static struct kobj_type rpc_sysfs_client_type = {
 	.release = rpc_sysfs_client_release,
 	.sysfs_ops = &kobj_sysfs_ops,
@@ -243,6 +277,7 @@ static struct kobj_type rpc_sysfs_client_type = {
 
 static struct kobj_type rpc_sysfs_xprt_switch_type = {
 	.release = rpc_sysfs_xprt_switch_release,
+	.default_attrs = rpc_sysfs_xprt_switch_attrs,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.namespace = rpc_sysfs_xprt_switch_namespace,
 };