diff --git a/sys/dev/ata/atapi-cd.c b/sys/dev/ata/atapi-cd.c
index 15a6a2b005da..81c8ed4922ff 100644
--- a/sys/dev/ata/atapi-cd.c
+++ b/sys/dev/ata/atapi-cd.c
@@ -1146,14 +1146,7 @@ acd_start(struct atapi_softc *atp)
 
     bzero(ccb, sizeof(ccb));
     count = (bp->bio_bcount + (cdp->block_size - 1)) / cdp->block_size;
-    {
-    /* XXX Hack until b_offset is always initialized */
-    struct buf *bup = (struct buf *)bp;
-    if (bup->b_flags & B_PHYS)
-	lba = bup->b_offset / cdp->block_size;
-    else
-	lba = bp->bio_blkno / (cdp->block_size / DEV_BSIZE);
-    }
+    lba = bp->bio_offset / cdp->block_size;
 
     if (bp->bio_cmd == BIO_READ) {
 	/* if transfer goes beyond EOM adjust it to be within limits */
diff --git a/sys/kern/subr_disk.c b/sys/kern/subr_disk.c
index 0838056bedbe..cf25c1b1ad5f 100644
--- a/sys/kern/subr_disk.c
+++ b/sys/kern/subr_disk.c
@@ -201,6 +201,8 @@ diskstrategy(struct bio *bp)
 		return;
 	}
 
+	KASSERT(dp->d_devsw != NULL, ("NULL devsw"));
+	KASSERT(dp->d_devsw->d_strategy != NULL, ("NULL d_strategy"));
 	dp->d_devsw->d_strategy(bp);
 	return;
 	
diff --git a/sys/sys/bio.h b/sys/sys/bio.h
index 4a95e8831c87..55a4bc170789 100644
--- a/sys/sys/bio.h
+++ b/sys/sys/bio.h
@@ -137,9 +137,9 @@ struct buf {
 #define	b_iodone	b_io.bio_done
 #define	b_iodone_chain	b_io.bio_done_chain
 #define	b_ioflags	b_io.bio_flags
-#define	b_offset	b_io.bio_offset
 #define	b_pblkno	b_io.bio_pblkno
 #define	b_resid		b_io.bio_resid
+	off_t	b_offset;		/* Offset into file. */
 	LIST_ENTRY(buf) b_hash;		/* Hash chain. */
 	TAILQ_ENTRY(buf) b_vnbufs;	/* Buffer's associated vnode. */
 	TAILQ_ENTRY(buf) b_freelist;	/* Free list position if not active. */
diff --git a/sys/sys/buf.h b/sys/sys/buf.h
index 4a95e8831c87..55a4bc170789 100644
--- a/sys/sys/buf.h
+++ b/sys/sys/buf.h
@@ -137,9 +137,9 @@ struct buf {
 #define	b_iodone	b_io.bio_done
 #define	b_iodone_chain	b_io.bio_done_chain
 #define	b_ioflags	b_io.bio_flags
-#define	b_offset	b_io.bio_offset
 #define	b_pblkno	b_io.bio_pblkno
 #define	b_resid		b_io.bio_resid
+	off_t	b_offset;		/* Offset into file. */
 	LIST_ENTRY(buf) b_hash;		/* Hash chain. */
 	TAILQ_ENTRY(buf) b_vnbufs;	/* Buffer's associated vnode. */
 	TAILQ_ENTRY(buf) b_freelist;	/* Free list position if not active. */
diff --git a/sys/sys/conf.h b/sys/sys/conf.h
index 9052f85aa456..f4ae3d6412cc 100644
--- a/sys/sys/conf.h
+++ b/sys/sys/conf.h
@@ -138,11 +138,15 @@ typedef void devfs_remove_t __P((dev_t dev));
  * of surgery, reset the flag and restart all the stuff on the stall
  * queue.
  */
-#define DEV_STRATEGY(bp, dummy)			\
-	do {					\
+#define DEV_STRATEGY(bp, dummy)						\
+	do {								\
 	if ((!(bp)->b_iocmd) || ((bp)->b_iocmd & ((bp)->b_iocmd - 1)))	\
-		Debugger("d_iocmd botch");	\
-	(*devsw((bp)->b_dev)->d_strategy)(&(bp)->b_io);	\
+		Debugger("d_iocmd botch");				\
+	if ((bp)->b_flags & B_PHYS)					\
+		(bp)->b_io.bio_offset = (bp)->b_offset;			\
+	else								\
+		(bp)->b_io.bio_offset = dbtob((bp)->b_blkno);		\
+	(*devsw((bp)->b_dev)->d_strategy)(&(bp)->b_io);			\
 	} while (0)
 
 /*
diff --git a/sys/sys/linedisc.h b/sys/sys/linedisc.h
index 9052f85aa456..f4ae3d6412cc 100644
--- a/sys/sys/linedisc.h
+++ b/sys/sys/linedisc.h
@@ -138,11 +138,15 @@ typedef void devfs_remove_t __P((dev_t dev));
  * of surgery, reset the flag and restart all the stuff on the stall
  * queue.
  */
-#define DEV_STRATEGY(bp, dummy)			\
-	do {					\
+#define DEV_STRATEGY(bp, dummy)						\
+	do {								\
 	if ((!(bp)->b_iocmd) || ((bp)->b_iocmd & ((bp)->b_iocmd - 1)))	\
-		Debugger("d_iocmd botch");	\
-	(*devsw((bp)->b_dev)->d_strategy)(&(bp)->b_io);	\
+		Debugger("d_iocmd botch");				\
+	if ((bp)->b_flags & B_PHYS)					\
+		(bp)->b_io.bio_offset = (bp)->b_offset;			\
+	else								\
+		(bp)->b_io.bio_offset = dbtob((bp)->b_blkno);		\
+	(*devsw((bp)->b_dev)->d_strategy)(&(bp)->b_io);			\
 	} while (0)
 
 /*