IB/srp: Stop the scsi_eh_<n> and scsi_tmf_<n> threads if login fails

scsi_host_alloc() not only allocates memory for a SCSI host but also
creates the scsi_eh_<n> kernel thread and the scsi_tmf_<n> workqueue.
Stop these threads if login fails by calling scsi_host_put().

Reported-by: Konstantin Krotov <[e-mail]>
Fixes: fb49c8bbaae7 ("Remove an extraneous scsi_host_put() from an error path")
Signed-off-by: Bart Van Assche <[e-mail]>
Cc: Sagi Grimberg <[e-mail]>
Cc: Sebastian Parschauer <[e-mail]>
Cc: <[e-mail]> #v3.19
Signed-off-by: Doug Ledford <[e-mail]>

drivers/infiniband/ulp/srp/ib_srp.c

···
 	return c;
 }
 
+/*
+ * Return values:
+ * < 0 upon failure. Caller is responsible for SRP target port cleanup.
+ * 0 and target->state == SRP_TARGET_REMOVED if asynchronous target port
+ *    removal has been scheduled.
+ * 0 and target->state != SRP_TARGET_REMOVED upon success.
+ */
 static int srp_add_target(struct srp_host *host, struct srp_target_port *target)
 {
 	struct srp_rport_identifiers ids;
···
 	mutex_unlock(&host->add_target_mutex);
 
 	scsi_host_put(target->scsi_host);
+	if (ret < 0)
+		scsi_host_put(target->scsi_host);
 
 	return ret;