target: Update SPC/SBC emulation for sess_prot_type

This patch updates standard INQUIRY, INQUIRY EVPD=0x86, READ_CAPACITY_16
and control mode pages to use se_sess->sess_prot_type when determing which
type of T10-PI related feature bits can be exposed.

This is required for fabric sessions supporting T10-PI metadata to
backend devices that don't have protection enabled.

Reviewed-by: Martin Petersen <martin.petersen@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Doug Gilbert <dgilbert@interlog.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 9efd1fd..67bc188 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -93,6 +93,8 @@
 {
 	struct se_device *dev = cmd->se_dev;
 	struct se_session *sess = cmd->se_sess;
+	int pi_prot_type = dev->dev_attrib.pi_prot_type;
+
 	unsigned char *rbuf;
 	unsigned char buf[32];
 	unsigned long long blocks = dev->transport->get_blocks(dev);
@@ -114,8 +116,15 @@
 	 * Set P_TYPE and PROT_EN bits for DIF support
 	 */
 	if (sess->sup_prot_ops & (TARGET_PROT_DIN_PASS | TARGET_PROT_DOUT_PASS)) {
-		if (dev->dev_attrib.pi_prot_type)
-			buf[12] = (dev->dev_attrib.pi_prot_type - 1) << 1 | 0x1;
+		/*
+		 * Only override a device's pi_prot_type if no T10-PI is
+		 * available, and sess_prot_type has been explicitly enabled.
+		 */
+		if (!pi_prot_type)
+			pi_prot_type = sess->sess_prot_type;
+
+		if (pi_prot_type)
+			buf[12] = (pi_prot_type - 1) << 1 | 0x1;
 	}
 
 	if (dev->transport->get_lbppbe)