TARGET/sbc,loopback: Adjust command data length in case pi exists on the wire

In various areas of the code, it is assumed that
se_cmd->data_length describes pure data. In case
that protection information exists over the wire
(protect bits is are on) the target core re-calculates
the data length from the CDB and the backed device
block size (instead of each transport peeking in the cdb).

Modify loopback device to include protection information
in the transferred data length (like other scsi transports).

Signed-off-by: Sagi Grimberg <[e-mail]>
Cc: [e-mail] # 3.15+
Signed-off-by: Nicholas Bellinger <[e-mail]>

drivers/target/loopback/tcm_loop.c

···
 	struct tcm_loop_hba *tl_hba;
 	struct tcm_loop_tpg *tl_tpg;
 	struct scatterlist *sgl_bidi = NULL;
-	u32 sgl_bidi_count = 0;
+	u32 sgl_bidi_count = 0, transfer_length;
 	int rc;
 
 	tl_hba = *(struct tcm_loop_hba **)shost_priv(sc->device->host);
···
 
 	}
 
-	if (!scsi_prot_sg_count(sc) && scsi_get_prot_op(sc) != SCSI_PROT_NORMAL)
+	transfer_length = scsi_transfer_length(sc);
+	if (!scsi_prot_sg_count(sc) &&
+	    scsi_get_prot_op(sc) != SCSI_PROT_NORMAL) {
 		se_cmd->prot_pto = true;
+		/*
+		 * loopback transport doesn't support
+		 * WRITE_GENERATE, READ_STRIP protection
+		 * information operations, go ahead unprotected.
+		 */
+		transfer_length = scsi_bufflen(sc);
+	}
 
 	rc = target_submit_cmd_map_sgls(se_cmd, tl_nexus->se_sess, sc->cmnd,
 			&tl_cmd->tl_sense_buf[0], tl_cmd->sc->device->lun,
-			scsi_bufflen(sc), tcm_loop_sam_attr(sc),
+			transfer_length, tcm_loop_sam_attr(sc),
 			sc->sc_data_direction, 0,
 			scsi_sglist(sc), scsi_sg_count(sc),
 			sgl_bidi, sgl_bidi_count,

drivers/target/target_core_sbc.c

···
 
 	cmd->prot_type = dev->dev_attrib.pi_prot_type;
 	cmd->prot_length = dev->prot_length * sectors;
-	pr_debug("%s: prot_type=%d, prot_length=%d prot_op=%d prot_checks=%d\n",
-		 __func__, cmd->prot_type, cmd->prot_length,
+
+	/**
+	 * In case protection information exists over the wire
+	 * we modify command data length to describe pure data.
+	 * The actual transfer length is data length + protection
+	 * length
+	 **/
+	if (protect)
+		cmd->data_length = sectors * dev->dev_attrib.block_size;
+
+	pr_debug("%s: prot_type=%d, data_length=%d, prot_length=%d "
+		 "prot_op=%d prot_checks=%d\n",
+		 __func__, cmd->prot_type, cmd->data_length, cmd->prot_length,
 		 cmd->prot_op, cmd->prot_checks);
 
 	return true;