target: Enable WRITE_INSERT emulation in target_execute_cmd

This patch enables WRITE_INSERT emulation in target_execute_cmd()
in order to locally generate DIF PI before submitting the WRITE
to the underlying backend device.

This is required for fabric drivers that currently don't support
DIF over-the-wire, in order to inact with backend devices that
have hardware (IBLOCK) or software (FILEIO + RAMDISK) support
for handling T10 PI.

v2 changes:
   - Convert to sbc_dif_generate() usage (Sagi)
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Quinn Tran <quinn.tran@qlogic.com>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_transport.c

@@ -1767,6 +1767,15 @@ void target_execute_cmd(struct se_cmd *cmd)
 	cmd->t_state = TRANSPORT_PROCESSING;
 	cmd->transport_state |= CMD_T_ACTIVE|CMD_T_BUSY|CMD_T_SENT;
 	spin_unlock_irq(&cmd->t_state_lock);
+	/*
+	 * Perform WRITE_INSERT of PI using software emulation when backend
+	 * device has PI enabled, if the transport has not already generated
+	 * PI using hardware WRITE_INSERT offload.
+	 */
+	if (cmd->prot_op == TARGET_PROT_DOUT_INSERT) {
+		if (!(cmd->se_sess->sup_prot_ops & TARGET_PROT_DOUT_INSERT))
+			sbc_dif_generate(cmd);
+	}
 
 	if (target_handle_task_attr(cmd)) {
 		spin_lock_irq(&cmd->t_state_lock);