diff -ur /opt/kernel/linux-2.4.20-pre1/drivers/block/loop.c linux/drivers/block/loop.c
--- /opt/kernel/linux-2.4.20-pre1/drivers/block/loop.c	2002-08-03 02:39:43.000000000 +0200
+++ linux/drivers/block/loop.c	2002-08-09 09:59:42.000000000 +0200
@@ -473,6 +473,11 @@
 	atomic_inc(&lo->lo_pending);
 	spin_unlock_irq(&lo->lo_lock);
 
+	if (lo->lo_flags & LO_FLAGS_FAIL) {
+		printk("%s: failing %s\n", kdevname(rbh->b_rdev), rw == WRITE ? "write" : "read");
+		goto err;
+	}
+
 	if (rw == WRITE) {
 		if (lo->lo_flags & LO_FLAGS_READ_ONLY)
 			goto err;
@@ -877,6 +880,14 @@
 	case LOOP_GET_STATUS:
 		err = loop_get_status(lo, (struct loop_info *) arg);
 		break;
+	case LOOP_SET_FAIL:
+		lo->lo_flags |= LO_FLAGS_FAIL;
+		err = 0;
+		break;
+	case LOOP_CLEAR_FAIL:
+		lo->lo_flags &= ~LO_FLAGS_FAIL;
+		err = 0;
+		break;
 	case BLKGETSIZE:
 		if (lo->lo_state != Lo_bound) {
 			err = -ENXIO;
diff -ur /opt/kernel/linux-2.4.20-pre1/include/linux/loop.h linux/include/linux/loop.h
--- /opt/kernel/linux-2.4.20-pre1/include/linux/loop.h	2001-09-17 22:16:30.000000000 +0200
+++ linux/include/linux/loop.h	2002-08-08 12:01:56.000000000 +0200
@@ -78,6 +78,7 @@
 #define LO_FLAGS_DO_BMAP	1
 #define LO_FLAGS_READ_ONLY	2
 #define LO_FLAGS_BH_REMAP	4
+#define LO_FLAGS_FAIL		8
 
 /* 
  * Note that this structure gets the wrong offsets when directly used
@@ -151,5 +152,7 @@
 #define LOOP_CLR_FD	0x4C01
 #define LOOP_SET_STATUS	0x4C02
 #define LOOP_GET_STATUS	0x4C03
+#define LOOP_SET_FAIL	0x4c04
+#define LOOP_CLEAR_FAIL	0x4c05
 
 #endif