--- linux-2.6.19/drivers/md/raid5.c	2006-12-11 11:33:23.000000000 +0000
+++ linux-2.6.19-git17/drivers/md/raid5.c	2006-12-11 11:31:27.000000000 +0000
@@ -2567,7 +2567,7 @@
 	unsigned int chunk_sectors = mddev->chunk_size >> 9;
 	unsigned int bio_sectors = bio->bi_size >> 9;
 
-	if (bio_data_dir(bio))
+	if (bio_data_dir(bio) == WRITE )
 		return biovec->bv_len; /* always allow writes to be mergeable */
 
 	max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;