diff -uNr linux-2.4.20.recerr/drivers/scsi/scsi_debug.c linux-2.4.20/drivers/scsi/scsi_debug.c
--- linux-2.4.20.recerr/drivers/scsi/scsi_debug.c	2002-11-29 00:53:14.000000000 +0100
+++ linux-2.4.20/drivers/scsi/scsi_debug.c	2003-02-08 02:40:21.000000000 +0100
@@ -80,6 +80,8 @@
 static int scsi_debug_every_nth = DEF_EVERY_NTH;
 static int scsi_debug_cmnd_count = 0;
 static int scsi_debug_delay = DEF_DELAY;
+static int scsi_debug_inj_rec_err = 0;
+
 
 #define NR_HOSTS_PRESENT (((scsi_debug_num_devs - 1) / 7) + 1)
 #define N_HEAD          8
@@ -324,6 +326,12 @@
 			num = cmd[4];
 		}
 		errsts = resp_read(SCpnt, upper_blk, block, num, devip);
+ 		if (scsi_debug_inj_rec_err && !(SCpnt->pid % scsi_debug_inj_rec_err)) {
+ 			SCpnt->result = (COMMAND_COMPLETE << 8) | 
+ 					(CHECK_CONDITION << 1);
+ 			mk_sense_buffer(devip, RECOVERED_ERROR, 0x5d, 0, 14);
+ 		} else
+ 			SCpnt->result = 0;
 		break;
 	case REPORT_LUNS:
 		errsts = resp_report_luns(cmd, buff, bufflen, devip);
@@ -361,6 +369,12 @@
 	case MODE_SENSE:
 	case MODE_SENSE_10:
 		errsts = resp_mode_sense(cmd, target, buff, bufflen, devip);
+		if (scsi_debug_inj_rec_err && !(SCpnt->pid % scsi_debug_inj_rec_err)) {
+			SCpnt->result = (COMMAND_COMPLETE << 8) | 
+					(CHECK_CONDITION << 1);
+			mk_sense_buffer(devip, RECOVERED_ERROR, 0x5d, 0, 14);
+		} else
+			SCpnt->result = 0;
 		break;
 	default:
 #if 0
@@ -1160,6 +1174,8 @@
 MODULE_PARM_DESC(scsi_debug_every_nth, "timeout every nth command(def=100)");
 MODULE_PARM(scsi_debug_delay, "i");
 MODULE_PARM_DESC(scsi_debug_delay, "# of jiffies to delay response(def=1)");
+MODULE_PARM(scsi_debug_inj_rec_err, "i");
+MODULE_PARM_DESC(scsi_debug_inj_rec_err, "inject recovered errors every N read/write command");
 #ifdef MODULE_LICENSE
 MODULE_LICENSE("GPL");
 #endif