diff -rup linux-2.4.20-uml/fs/jbd/transaction.c linux-2.4.21-rc2/fs/jbd/transaction.c
--- linux-2.4.20-uml/fs/jbd/transaction.c	Thu Nov 28 16:53:15 2002
+++ linux-2.4.21-rc2/fs/jbd/transaction.c	Fri May 16 11:00:40 2003
@@ -735,7 +743,8 @@ done_locked:
 		int offset;
 		char *source;
 
-		J_ASSERT_JH(jh, buffer_uptodate(jh2bh(jh)));
+		J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)),
+			    "Possible IO failure.\n");
 		page = jh2bh(jh)->b_page;
 		offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK;
 		source = kmap(page);
diff -rup linux-2.4.20-uml/include/linux/jbd.h linux-2.4.21-rc2/include/linux/jbd.h
--- linux-2.4.20-uml/include/linux/jbd.h	Mon Aug 25 16:16:57 2003
+++ linux-2.4.21-rc2/include/linux/jbd.h	Tue May 13 13:28:29 2003
@@ -40,6 +40,15 @@
  */
 #undef JBD_PARANOID_WRITES
 
+/*
+ * Define JBD_PARANIOD_IOFAIL to cause a kernel BUG() if ext3 finds
+ * certain classes of error which can occur due to failed IOs.  Under
+ * normal use we want ext3 to continue after such errors, because
+ * hardware _can_ fail, but for debugging purposes when running tests on
+ * known-good hardware we may want to trap these errors.
+ */
+#undef JBD_PARANOID_IOFAIL
+
 #ifdef CONFIG_JBD_DEBUG
 /*
  * Define JBD_EXPENSIVE_CHECKING to enable more expensive internal
@@ -232,6 +272,23 @@ void buffer_assertion_failure(struct buf
 #define J_ASSERT(assert)	do { } while (0)
 #endif		/* JBD_ASSERTIONS */
 
+#if defined(JBD_PARANOID_IOFAIL)
+#define J_EXPECT(expr, why...)		J_ASSERT(expr)
+#define J_EXPECT_BH(bh, expr, why...)	J_ASSERT_BH(bh, expr)
+#define J_EXPECT_JH(jh, expr, why...)	J_ASSERT_JH(jh, expr)
+#else
+#define __journal_expect(expr, why...)					     \
+	do {								     \
+		if (!(expr)) {						     \
+			printk(KERN_ERR "EXT3-fs unexpected failure: %s;\n", # expr); \
+			printk(KERN_ERR why);				     \
+		}							     \
+	} while (0)
+#define J_EXPECT(expr, why...)		__journal_expect(expr, ## why)
+#define J_EXPECT_BH(bh, expr, why...)	__journal_expect(expr, ## why)
+#define J_EXPECT_JH(jh, expr, why...)	__journal_expect(expr, ## why)
+#endif
+
 enum jbd_state_bits {
 	BH_JWrite
 	  = BH_PrivateStart,	/* 1 if being written to log (@@@ DEBUGGING) */