ata: libata-scsi: simplify __ata_scsi_queuecmd()

This patch cleans up the code of __ata_scsi_queuecmd(). Since each
branch of the "if" condition check that scmd->cmd_len is not zero, move
this check out of the "if" to simplify the conditions being checked in
the "else" branch.

While at it, avoid the if-else-if-else structure using if-else if
structure and remove the redundant rc local variable.

This patch does not change the function logic.

Signed-off-by: Wenchao Hao <haowenchao@huawei.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

Author: wenchao-hao

drivers/ata/libata-scsi.c

@@ -3958,42 +3958,39 @@ int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
 {
 	u8 scsi_op = scmd->cmnd[0];
 	ata_xlat_func_t xlat_func;
-	int rc = 0;
+
+	if (unlikely(!scmd->cmd_len))
+		goto bad_cdb_len;
 
 	if (dev->class == ATA_DEV_ATA || dev->class == ATA_DEV_ZAC) {
-		if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
+		if (unlikely(scmd->cmd_len > dev->cdb_len))
 			goto bad_cdb_len;
 
 		xlat_func = ata_get_xlat_func(dev, scsi_op);
-	} else {
-		if (unlikely(!scmd->cmd_len))
-			goto bad_cdb_len;
+	} else if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
+		/* relay SCSI command to ATAPI device */
+		int len = COMMAND_SIZE(scsi_op);
 
-		xlat_func = NULL;
-		if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
-			/* relay SCSI command to ATAPI device */
-			int len = COMMAND_SIZE(scsi_op);
-			if (unlikely(len > scmd->cmd_len ||
-				     len > dev->cdb_len ||
-				     scmd->cmd_len > ATAPI_CDB_LEN))
-				goto bad_cdb_len;
+		if (unlikely(len > scmd->cmd_len ||
+			     len > dev->cdb_len ||
+			     scmd->cmd_len > ATAPI_CDB_LEN))
+			goto bad_cdb_len;
 
-			xlat_func = atapi_xlat;
-		} else {
-			/* ATA_16 passthru, treat as an ATA command */
-			if (unlikely(scmd->cmd_len > 16))
-				goto bad_cdb_len;
+		xlat_func = atapi_xlat;
+	} else {
+		/* ATA_16 passthru, treat as an ATA command */
+		if (unlikely(scmd->cmd_len > 16))
+			goto bad_cdb_len;
 
-			xlat_func = ata_get_xlat_func(dev, scsi_op);
-		}
+		xlat_func = ata_get_xlat_func(dev, scsi_op);
 	}
 
 	if (xlat_func)
-		rc = ata_scsi_translate(dev, scmd, xlat_func);
-	else
-		ata_scsi_simulate(dev, scmd);
+		return ata_scsi_translate(dev, scmd, xlat_func);
 
-	return rc;
+	ata_scsi_simulate(dev, scmd);
+
+	return 0;
 
  bad_cdb_len:
 	scmd->result = DID_ERROR << 16;