[PATCH v4 1/3] nvmet: Expose max queues to configfs

[Daniel Wagner <dwagner@suse.de>]

Allow to set the max queues the target supports. This is useful for
testing the reconnect attempt of the host with changing numbers of
supported queues.

Signed-off-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
 drivers/nvme/target/configfs.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 2bcd60758919..e34a2896fedb 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1281,6 +1281,34 @@ static ssize_t nvmet_subsys_attr_pi_enable_store(struct config_item *item,
 CONFIGFS_ATTR(nvmet_subsys_, attr_pi_enable);
 #endif
 
+static ssize_t nvmet_subsys_attr_qid_max_show(struct config_item *item,
+					      char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", to_subsys(item)->max_qid);
+}
+
+static ssize_t nvmet_subsys_attr_qid_max_store(struct config_item *item,
+					       const char *page, size_t cnt)
+{
+	struct nvmet_port *port = to_nvmet_port(item);
+	u16 qid_max;
+
+	if (nvmet_is_port_enabled(port, __func__))
+		return -EACCES;
+
+	if (sscanf(page, "%hu\n", &qid_max) != 1)
+		return -EINVAL;
+
+	if (qid_max < 1 || qid_max > NVMET_NR_QUEUES)
+		return -EINVAL;
+
+	down_write(&nvmet_config_sem);
+	to_subsys(item)->max_qid = qid_max;
+	up_write(&nvmet_config_sem);
+	return cnt;
+}
+CONFIGFS_ATTR(nvmet_subsys_, attr_qid_max);
+
 static struct configfs_attribute *nvmet_subsys_attrs[] = {
 	&nvmet_subsys_attr_attr_allow_any_host,
 	&nvmet_subsys_attr_attr_version,
@@ -1288,6 +1316,7 @@ static struct configfs_attribute *nvmet_subsys_attrs[] = {
 	&nvmet_subsys_attr_attr_cntlid_min,
 	&nvmet_subsys_attr_attr_cntlid_max,
 	&nvmet_subsys_attr_attr_model,
+	&nvmet_subsys_attr_attr_qid_max,
 #ifdef CONFIG_BLK_DEV_INTEGRITY
 	&nvmet_subsys_attr_attr_pi_enable,
 #endif
-- 
2.37.2