nvme: track subsystems

This adds a new nvme_subsystem structure so that we can track multiple
controllers that belong to a single subsystem.  For now we only use it
to store the NQN, and to check that we don't have duplicate NQNs unless
the involved subsystems support multiple controllers.

Includes code originally from Hannes Reinecke to expose the subsystems
in sysfs.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/fabrics.c

@@ -882,10 +882,10 @@ nvmf_create_ctrl(struct device *dev, const char *buf, size_t count)
 		goto out_unlock;
 	}
 
-	if (strcmp(ctrl->subnqn, opts->subsysnqn)) {
+	if (strcmp(ctrl->subsys->subnqn, opts->subsysnqn)) {
 		dev_warn(ctrl->device,
 			"controller returned incorrect NQN: \"%s\".\n",
-			ctrl->subnqn);
+			ctrl->subsys->subnqn);
 		up_read(&nvmf_transports_rwsem);
 		nvme_delete_ctrl_sync(ctrl);
 		return ERR_PTR(-EINVAL);

drivers/nvme/host/nvme.h

@@ -140,13 +140,12 @@ struct nvme_ctrl {
 	struct work_struct reset_work;
 	struct work_struct delete_work;
 
+	struct nvme_subsystem *subsys;
+	struct list_head subsys_entry;
+
 	struct opal_dev *opal_dev;
 
 	char name[12];
-	char serial[20];
-	char model[40];
-	char firmware_rev[8];
-	char subnqn[NVMF_NQN_SIZE];
 	u16 cntlid;
 
 	u32 ctrl_config;
@@ -157,7 +156,6 @@ struct nvme_ctrl {
 	u32 page_size;
 	u32 max_hw_sectors;
 	u16 oncs;
-	u16 vid;
 	u16 oacs;
 	u16 nssa;
 	u16 nr_streams;
@@ -200,6 +198,25 @@ struct nvme_ctrl {
 	struct nvmf_ctrl_options *opts;
 };
 
+struct nvme_subsystem {
+	int			instance;
+	struct device		dev;
+	/*
+	 * Because we unregister the device on the last put we need
+	 * a separate refcount.
+	 */
+	struct kref		ref;
+	struct list_head	entry;
+	struct mutex		lock;
+	struct list_head	ctrls;
+	char			subnqn[NVMF_NQN_SIZE];
+	char			serial[20];
+	char			model[40];
+	char			firmware_rev[8];
+	u8			cmic;
+	u16			vendor_id;
+};
+
 struct nvme_ns {
 	struct list_head list;