diff --git a/block/blk-core.c b/block/blk-core.c
index c89883b..6c03f54 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -163,8 +163,13 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
 		if (bio_integrity(bio))
 			bio_integrity_advance(bio, nbytes);
 
-		if (bio->bi_size == 0)
+		if (bio->bi_size == 0) {
+			if (error)
+				printk("XXX %s: failing bio %p with %d\n",
+				       rq->rq_disk ? rq->rq_disk->disk_name : "?",
+				       bio, error);
 			bio_endio(bio, error);
+		}
 	} else {
 
 		/*
diff --git a/fs/bio.c b/fs/bio.c
index 9871164..c26364a 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1391,13 +1391,24 @@ void bio_check_pages_dirty(struct bio *bio)
  **/
 void bio_endio(struct bio *bio, int error)
 {
+	char name[BDEVNAME_SIZE] = "?";
+
+	if (bio->bi_bdev)
+		bdevname(bio->bi_bdev, name);
+
 	if (error)
 		clear_bit(BIO_UPTODATE, &bio->bi_flags);
-	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
+		printk("XXX %s: !uptodate on bio %p\n", name, bio);
 		error = -EIO;
+	}
 
-	if (bio->bi_end_io)
+	if (bio->bi_end_io) {
+		if (error)
+			printk("XXX %s: bio=%p error=%d bi_end_io=%p\n",
+			       name, bio, error, bio->bi_end_io);
 		bio->bi_end_io(bio, error);
+	}
 }
 
 void bio_pair_release(struct bio_pair *bp)