target: Perform PROTECT sanity checks for WRITE_SAME

This patch adds a call to sbc_check_prot() within sbc_setup_write_same()
code to perform the various protection releated sanity checks, including
failing if WRPROTECT or RDPROTECT is set for a backend device that has
not advertised support for T10-PI.

Also, since WRITE_SAME + T10-PI is currently not supported by IBLOCK +
FILEIO backends, go ahead and fail if ->execute_write_same() is invoked
with a non zero cmd->prot_op.

Cc: Martin Petersen <martin.petersen@oracle.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index c2aea09..9f1ed77 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -494,6 +494,11 @@
 		target_complete_cmd(cmd, SAM_STAT_GOOD);
 		return 0;
 	}
+	if (cmd->prot_op) {
+		pr_err("WRITE_SAME: Protection information with FILEIO"
+		       " backends not supported\n");
+		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+	}
 	sg = &cmd->t_data_sg[0];
 
 	if (cmd->t_data_nents > 1 ||