[RFC PATCH net-next 08/13] net/smc: introduce loopback-ism runtime switch

[Wen Gu <guwen@linux.alibaba.com>]

This provides a runtime switch to activate or deactivate loopback-ism
device by echo {1|0} > /sys/devices/virtual/smc/loopback-ism/active. It
will trigger the registration or removal of loopback-ism from the SMC-D
device list.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_loopback.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++
 net/smc/smc_loopback.h |  1 +
 2 files changed, 56 insertions(+)

diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
index 83bc9a7..04f8612 100644
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -28,6 +28,58 @@
 static struct smc_lo_dev *lo_dev;
 static struct class *smc_class;
 
+static int smcd_lo_register_dev(struct smc_lo_dev *ldev);
+static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev);
+
+static ssize_t active_show(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct smc_lo_dev *ldev =
+		container_of(dev, struct smc_lo_dev, dev);
+
+	return sysfs_emit(buf, "%d\n", ldev->active);
+}
+
+static ssize_t active_store(struct device *dev,
+			    struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct smc_lo_dev *ldev =
+		container_of(dev, struct smc_lo_dev, dev);
+	bool active;
+	int ret;
+
+	ret = kstrtobool(buf, &active);
+	if (ret)
+		return ret;
+
+	if (active && !ldev->active) {
+		/* activate loopback-ism */
+		ret = smcd_lo_register_dev(ldev);
+		if (ret)
+			return ret;
+	} else if (!active && ldev->active) {
+		/* deactivate loopback-ism */
+		smcd_lo_unregister_dev(ldev);
+	}
+
+	return count;
+}
+static DEVICE_ATTR_RW(active);
+static struct attribute *smc_lo_attrs[] = {
+	&dev_attr_active.attr,
+	NULL
+};
+
+static struct attribute_group smc_lo_attr_group = {
+	.attrs  = smc_lo_attrs,
+};
+
+static const struct attribute_group *smc_lo_attr_groups[] = {
+	&smc_lo_attr_group,
+	NULL,
+};
+
 static void smc_lo_generate_id(struct smc_lo_dev *ldev)
 {
 	struct smcd_gid *lgid = &ldev->local_gid;
@@ -277,6 +329,7 @@ static int smcd_lo_register_dev(struct smc_lo_dev *ldev)
 	mutex_lock(&smcd_dev_list.mutex);
 	list_add(&smcd->list, &smcd_dev_list.list);
 	mutex_unlock(&smcd_dev_list.mutex);
+	ldev->active = 1;
 	pr_warn_ratelimited("smc: adding smcd device %s\n",
 			    smc_lo_dev_name);
 	return 0;
@@ -288,6 +341,7 @@ static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev)
 
 	pr_warn_ratelimited("smc: removing smcd device %s\n",
 			    smc_lo_dev_name);
+	ldev->active = 0;
 	smcd->going_away = 1;
 	smc_smcd_terminate_all(smcd);
 	mutex_lock(&smcd_dev_list.mutex);
@@ -335,6 +389,7 @@ static int smc_lo_dev_probe(void)
 
 	ldev->dev.parent = NULL;
 	ldev->dev.class = smc_class;
+	ldev->dev.groups = smc_lo_attr_groups;
 	ldev->dev.release = smc_lo_dev_release;
 	device_initialize(&ldev->dev);
 	dev_set_name(&ldev->dev, smc_lo_dev_name);
diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
index 3d5d2f5..0cc2f83 100644
--- a/net/smc/smc_loopback.h
+++ b/net/smc/smc_loopback.h
@@ -35,6 +35,7 @@ struct smc_lo_dmb_node {
 struct smc_lo_dev {
 	struct smcd_dev *smcd;
 	struct device dev;
+	u8 active;
 	u16 chid;
 	struct smcd_gid local_gid;
 	rwlock_t dmb_ht_lock;
-- 
1.8.3.1