nvmet-tcp: validate so_priority modparam value

The module parameter so_priority is passed to the function
sock_set_priority() which has following prototype and expect
priotity arg type to be u32:-

void sock_set_priority(struct sock *sk, u32 priority);

Add a module parameter validation callback to reject any negative
values for the so_priority as it is defigned as int. Use this
oppurtunity to update the module parameter description and print the
default value.

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Author: Chaitanya Kulkarni

drivers/nvme/target/tcp.c

@@ -20,15 +20,40 @@
 
 #define NVMET_TCP_DEF_INLINE_DATA_SIZE	(4 * PAGE_SIZE)
 
+static int param_store_val(const char *str, int *val, int min, int max)
+{
+	int ret, new_val;
+
+	ret = kstrtoint(str, 10, &new_val);
+	if (ret)
+		return -EINVAL;
+
+	if (new_val < min || new_val > max)
+		return -EINVAL;
+
+	*val = new_val;
+	return 0;
+}
+
+static int set_params(const char *str, const struct kernel_param *kp)
+{
+	return param_store_val(str, kp->arg, 0, INT_MAX);
+}
+
+static const struct kernel_param_ops set_param_ops = {
+	.set	= set_params,
+	.get	= param_get_int,
+};
+
 /* Define the socket priority to use for connections were it is desirable
  * that the NIC consider performing optimized packet processing or filtering.
  * A non-zero value being sufficient to indicate general consideration of any
  * possible optimization.  Making it a module param allows for alternative
  * values that may be unique for some NIC implementations.
  */
 static int so_priority;
-module_param(so_priority, int, 0644);
-MODULE_PARM_DESC(so_priority, "nvmet tcp socket optimize priority");
+device_param_cb(so_priority, &set_param_ops, &so_priority, 0644);
+MODULE_PARM_DESC(so_priority, "nvmet tcp socket optimize priority: Default 0");
 
 /* Define a time period (in usecs) that io_work() shall sample an activated
  * queue before determining it to be idle.  This optional module behavior