nvmet: Move serial number from controller to subsystem

The NVMe specification defines the serial number as:

"Serial Number (SN): Contains the serial number for the NVM subsystem
that is assigned by the vendor as an ASCII string. Refer to section
7.10 for unique identifier requirements. Refer to section 1.5 for ASCII
string requirements"

So move it from the controller to the subsystem, where it belongs.

Signed-off-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/nvme/target/admin-cmd.c

···
 	id->ssvid = 0;
 
 	memset(id->sn, ' ', sizeof(id->sn));
-	snprintf(id->sn, sizeof(id->sn), "%llx", ctrl->serial);
+	snprintf(id->sn, sizeof(id->sn), "%llx", ctrl->subsys->serial);
 
 	memset(id->mn, ' ', sizeof(id->mn));
 	strncpy((char *)id->mn, "Linux", sizeof(id->mn));

drivers/nvme/target/core.c

···
 	memcpy(ctrl->subsysnqn, subsysnqn, NVMF_NQN_SIZE);
 	memcpy(ctrl->hostnqn, hostnqn, NVMF_NQN_SIZE);
 
-	/* generate a random serial number as our controllers are ephemeral: */
-	get_random_bytes(&ctrl->serial, sizeof(ctrl->serial));
-
 	kref_init(&ctrl->ref);
 	ctrl->subsys = subsys;
 
···
 		return NULL;
 
 	subsys->ver = NVME_VS(1, 3, 0); /* NVMe 1.3.0 */
+	/* generate a random serial number as our controllers are ephemeral: */
+	get_random_bytes(&subsys->serial, sizeof(subsys->serial));
 
 	switch (type) {
 	case NVME_NQN_NVME:

drivers/nvme/target/nvmet.h

···
 
 	struct mutex		lock;
 	u64			cap;
-	u64			serial;
 	u32			cc;
 	u32			csts;
 
···
 	u16			max_qid;
 
 	u64			ver;
+	u64			serial;
 	char			*subsysnqn;
 
 	struct config_group	group;