diff --git a/sys/i386/isa/wd.c b/sys/i386/isa/wd.c
index 9416bc774cc2..49ab5ce81bf1 100644
--- a/sys/i386/isa/wd.c
+++ b/sys/i386/isa/wd.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)wd.c	7.2 (Berkeley) 5/9/91
- *	$Id: wd.c,v 1.90 1995/10/29 17:34:17 bde Exp $
+ *	$Id: wd.c,v 1.91 1995/11/20 12:41:53 phk Exp $
  */
 
 /* TODO:
@@ -245,8 +245,20 @@ struct disk {
 static int wdtest = 0;
 
 static struct disk *wddrives[NWD];	/* table of units */
+static struct buf_queue_head drive_queue[NWD];	/* head of queue per drive */
+static struct {
+	int	b_errcnt;
+	int	b_active;
+} wdutab[NWD];
+/*
 static struct buf wdtab[NWDC];
-static struct buf wdutab[NWD];	/* head of queue per drive */
+*/
+static struct {
+	struct	buf_queue_head controller_queue;
+	int	b_errcnt;
+	int	b_active;
+} wdtab[NWDC];
+
 #ifdef notyet
 static struct buf rwdbuf[NWD];	/* buffers for raw IO */
 #endif
@@ -399,6 +411,7 @@ wdattach(struct isa_device *dvp)
 		return (0);
 
 	kdc_wdc[dvp->id_unit].kdc_state = DC_UNKNOWN; /* XXX */
+	TAILQ_INIT( &wdtab[dvp->id_unit].controller_queue);
 
 	for (wdup = isa_biotab_wdc; wdup->id_driver != 0; wdup++) {
 		if (wdup->id_iobase != dvp->id_iobase)
@@ -406,6 +419,7 @@ wdattach(struct isa_device *dvp)
 		lunit = wdup->id_unit;
 		if (lunit >= NWD)
 			continue;
+
 		unit = wdup->id_physid;
 
 		du = malloc(sizeof *du, M_TEMP, M_NOWAIT);
@@ -414,6 +428,7 @@ wdattach(struct isa_device *dvp)
 		if (wddrives[lunit] != NULL)
 			panic("drive attached twice");
 		wddrives[lunit] = du;
+		TAILQ_INIT( &drive_queue[lunit]);
 		bzero(du, sizeof *du);
 		du->dk_ctrlr = dvp->id_unit;
 		du->dk_unit = unit;
@@ -567,12 +582,11 @@ wdstrategy(register struct buf *bp)
 	}
 
 	/* queue transfer on drive, activate drive and controller if idle */
-	dp = &wdutab[lunit];
 	s = splbio();
 
-	disksort(dp, bp);
+	tqdisksort(&drive_queue[lunit], bp);
 
-	if (dp->b_active == 0)
+	if (wdutab[lunit].b_active == 0)
 		wdustart(du);	/* start drive */
 
 	/* Pick up changes made by readdisklabel(). */
@@ -628,30 +642,25 @@ wdstrategy1(struct buf *bp)
 static void
 wdustart(register struct disk *du)
 {
-	register struct buf *bp, *dp = &wdutab[du->dk_lunit];
+	register struct buf *bp;
 	int	ctrlr = du->dk_ctrlr;
 
 	/* unit already active? */
-	if (dp->b_active)
+	if (wdutab[du->dk_lunit].b_active)
 		return;
 
-	/* anything to start? */
-	bp = dp->b_actf;
-	if (bp == NULL)
-		return;
 
-	dp->b_actf = bp->b_actf;
-	bp->b_actf = NULL;
-	/* link onto controller queue */
-	if (wdtab[ctrlr].b_actf == NULL) {
-		wdtab[ctrlr].b_actf = bp;
-	} else {
-		*wdtab[ctrlr].b_actb = bp;
+	bp = drive_queue[du->dk_lunit].tqh_first;
+	if (bp == NULL) {	/* yes, an assign */
+		return;
 	}
-	wdtab[ctrlr].b_actb = &bp->b_actf;
+	TAILQ_REMOVE( &drive_queue[du->dk_lunit], bp, b_act);
+
+	/* link onto controller queue */
+	TAILQ_INSERT_TAIL( &wdtab[ctrlr].controller_queue, bp, b_act);
 
 	/* mark the drive unit as busy */
-	dp->b_active = 1;
+	wdutab[du->dk_lunit].b_active = 1;
 }
 
 /*
@@ -682,7 +691,7 @@ wdstart(int ctrlr)
 #endif
 loop:
 	/* is there a drive for the controller to do a transfer with? */
-	bp = wdtab[ctrlr].b_actf;
+	bp = wdtab[ctrlr].controller_queue.tqh_first;
 	if (bp == NULL) {
 #ifdef ATAPI
 		if (atapi_start && atapi_start (ctrlr))
@@ -928,9 +937,8 @@ wdintr(int unit)
 		return;
 	}
 #endif
-	bp = wdtab[unit].b_actf;
+	bp = wdtab[unit].controller_queue.tqh_first;
 	du = wddrives[dkunit(bp->b_dev)];
-	dp = &wdutab[du->dk_lunit];
 	du->dk_timeout = 0;
 
 	if (wdwait(du, 0, TIMEOUT) < 0) {
@@ -1070,11 +1078,11 @@ outt:
 done: ;
 		/* done with this transfer, with or without error */
 		du->dk_flags &= ~DKFL_SINGLE;
-		wdtab[unit].b_actf = bp->b_actf;
+		TAILQ_REMOVE(&wdtab[unit].controller_queue, bp, b_act);
 		wdtab[unit].b_errcnt = 0;
 		bp->b_resid = bp->b_bcount - du->dk_skip * DEV_BSIZE;
-		dp->b_active = 0;
-		dp->b_errcnt = 0;
+		wdutab[du->dk_lunit].b_active = 0;
+		wdutab[du->dk_lunit].b_errcnt = 0;
 		du->dk_skip = 0;
 		biodone(bp);
 	}
@@ -1091,7 +1099,7 @@ done: ;
 	/* anything more for controller to do? */
 #ifndef ATAPI
 	/* This is not valid in ATAPI mode. */
-	if (wdtab[unit].b_actf)
+	if (wdtab[unit].controller_queue.tqh_first)
 #endif
 		wdstart(unit);
 }
@@ -1129,7 +1137,7 @@ wdopen(dev_t dev, int flags, int fmt, struct proc *p)
 	wdsleep(du->dk_ctrlr, "wdopn1");
 	du->dk_flags |= DKFL_LABELLING;
 	du->dk_state = WANTOPEN;
-	wdutab[lunit].b_actf = NULL;
+	/* drive_queue[lunit].b_actf = NULL; */
 	{
 	struct disklabel label;
 
@@ -1150,7 +1158,7 @@ wdopen(dev_t dev, int flags, int fmt, struct proc *p)
 	if ((du->dk_flags & DKFL_BSDLABEL) == 0) {
 		/*
 		 * wdtab[ctrlr].b_active != 0 implies
-		 * wdutab[lunit].b_actf == NULL (?)
+		 * drive_queue[lunit].b_actf == NULL (?)
 		 * so the following guards most things (until the next i/o).
 		 * It doesn't guard against a new i/o starting and being
 		 * affected by the label being changed.  Sigh.
@@ -1159,7 +1167,7 @@ wdopen(dev_t dev, int flags, int fmt, struct proc *p)
 
 		du->dk_flags |= DKFL_LABELLING;
 		du->dk_state = WANTOPEN;
-		wdutab[lunit].b_actf = NULL;
+		/* drive_queue[lunit].b_actf = NULL; */
 
 		error = dsinit(dkmodpart(dev, RAW_PART), wdstrategy,
 			       &du->dk_dd, &du->dk_slices);
@@ -1962,8 +1970,10 @@ wdreset(struct disk *du)
 static void
 wdsleep(int ctrlr, char *wmesg)
 {
+	int s = splbio();
 	while (wdtab[ctrlr].b_active)
 		tsleep((caddr_t)&wdtab[ctrlr].b_active, PZERO - 1, wmesg, 1);
+	splx(s);
 }
 
 static void
diff --git a/sys/kern/subr_disklabel.c b/sys/kern/subr_disklabel.c
index be8e81a06507..3598a690f3d4 100644
--- a/sys/kern/subr_disklabel.c
+++ b/sys/kern/subr_disklabel.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ufs_disksubr.c	8.5 (Berkeley) 1/21/94
- * $Id: ufs_disksubr.c,v 1.18 1995/08/28 16:09:11 bde Exp $
+ * $Id: ufs_disksubr.c,v 1.19 1995/09/16 17:04:06 bde Exp $
  */
 
 #include <sys/param.h>
@@ -68,6 +68,99 @@
  */
 #define	b_cylinder	b_resid
 
+void
+tqdisksort(ap, bp)
+	struct buf_queue_head *ap;
+	register struct buf *bp;
+{
+	register struct buf *bq;
+	struct buf *bn;
+
+	/* If the queue is empty, then it's easy. */
+	if ((bq = ap->tqh_first) == NULL) {
+		TAILQ_INSERT_HEAD(ap, bp, b_act);
+		return;
+	}
+
+#if 1
+	/* Put new writes after all reads */
+	if ((bp->b_flags & B_READ) == 0) {
+		while (bn = bq->b_act.tqe_next) {
+			if ((bq->b_flags & B_READ) == 0)
+				break;
+			bq = bn;
+		}
+	} else {
+		while (bn = bq->b_act.tqe_next) {
+			if ((bq->b_flags & B_READ) == 0) {
+				if (ap->tqh_first != bq) {
+					bq = *bq->b_act.tqe_prev;
+				} 
+				break;
+			}
+			bq = bn;
+		}
+		goto insert;
+	}
+#endif
+
+	/*
+	 * If we lie after the first (currently active) request, then we
+	 * must locate the second request list and add ourselves to it.
+	 */
+	if (bp->b_pblkno < bq->b_pblkno) {
+		while (bn = bq->b_act.tqe_next) {
+			/*
+			 * Check for an ``inversion'' in the normally ascending
+			 * cylinder numbers, indicating the start of the second
+			 * request list.
+			 */
+			if (bn->b_pblkno < bq->b_pblkno) {
+				/*
+				 * Search the second request list for the first
+				 * request at a larger cylinder number.  We go
+				 * before that; if there is no such request, we
+				 * go at end.
+				 */
+				do {
+					if (bp->b_pblkno < bn->b_pblkno)
+						goto insert;
+					bq = bn;
+				} while (bn = bq->b_act.tqe_next);
+				goto insert;		/* after last */
+			}
+			bq = bn;
+		}
+		/*
+		 * No inversions... we will go after the last, and
+		 * be the first request in the second request list.
+		 */
+		goto insert;
+	}
+	/*
+	 * Request is at/after the current request...
+	 * sort in the first request list.
+	 */
+	while (bn = bq->b_act.tqe_next) {
+		/*
+		 * We want to go after the current request if there is an
+		 * inversion after it (i.e. it is the end of the first
+		 * request list), or if the next request is a larger cylinder
+		 * than our request.
+		 */
+		if (bn->b_pblkno < bq->b_pblkno ||
+		    bp->b_pblkno < bn->b_pblkno)
+			goto insert;
+		bq = bn;
+	}
+	/*
+	 * Neither a second list nor a larger request... we go at the end of
+	 * the first list, which is the same as the end of the whole schebang.
+	 */
+insert:
+	TAILQ_INSERT_AFTER(ap, bq, bp, b_act);
+}
+
 void
 disksort(ap, bp)
 	register struct buf *ap, *bp;
diff --git a/sys/sys/disk.h b/sys/sys/disk.h
index c90eca5b0d32..04d7d1c1b3c4 100644
--- a/sys/sys/disk.h
+++ b/sys/sys/disk.h
@@ -41,7 +41,7 @@
  *
  *	@(#)disk.h	8.1 (Berkeley) 6/2/93
  *
- * $Id: disk.h,v 1.2 1994/08/02 07:52:48 davidg Exp $
+ * $Id: disk.h,v 1.3 1994/08/21 04:41:39 paul Exp $
  */
 
 #ifndef _SYS_DISK_H_
@@ -108,6 +108,7 @@ struct disksort_stats {
 
 #ifdef KERNEL
 void	disksort __P((struct buf *, struct buf *));
+void	tqdisksort __P((struct buf_queue_head *, struct buf *));
 char	*readdisklabel __P((struct dkdevice *, int));
 int	setdisklabel __P((struct dkdevice *, struct disklabel *));
 int	writedisklabel __P((struct dkdevice *, int));
diff --git a/sys/ufs/ufs/ufs_disksubr.c b/sys/ufs/ufs/ufs_disksubr.c
index be8e81a06507..3598a690f3d4 100644
--- a/sys/ufs/ufs/ufs_disksubr.c
+++ b/sys/ufs/ufs/ufs_disksubr.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ufs_disksubr.c	8.5 (Berkeley) 1/21/94
- * $Id: ufs_disksubr.c,v 1.18 1995/08/28 16:09:11 bde Exp $
+ * $Id: ufs_disksubr.c,v 1.19 1995/09/16 17:04:06 bde Exp $
  */
 
 #include <sys/param.h>
@@ -68,6 +68,99 @@
  */
 #define	b_cylinder	b_resid
 
+void
+tqdisksort(ap, bp)
+	struct buf_queue_head *ap;
+	register struct buf *bp;
+{
+	register struct buf *bq;
+	struct buf *bn;
+
+	/* If the queue is empty, then it's easy. */
+	if ((bq = ap->tqh_first) == NULL) {
+		TAILQ_INSERT_HEAD(ap, bp, b_act);
+		return;
+	}
+
+#if 1
+	/* Put new writes after all reads */
+	if ((bp->b_flags & B_READ) == 0) {
+		while (bn = bq->b_act.tqe_next) {
+			if ((bq->b_flags & B_READ) == 0)
+				break;
+			bq = bn;
+		}
+	} else {
+		while (bn = bq->b_act.tqe_next) {
+			if ((bq->b_flags & B_READ) == 0) {
+				if (ap->tqh_first != bq) {
+					bq = *bq->b_act.tqe_prev;
+				} 
+				break;
+			}
+			bq = bn;
+		}
+		goto insert;
+	}
+#endif
+
+	/*
+	 * If we lie after the first (currently active) request, then we
+	 * must locate the second request list and add ourselves to it.
+	 */
+	if (bp->b_pblkno < bq->b_pblkno) {
+		while (bn = bq->b_act.tqe_next) {
+			/*
+			 * Check for an ``inversion'' in the normally ascending
+			 * cylinder numbers, indicating the start of the second
+			 * request list.
+			 */
+			if (bn->b_pblkno < bq->b_pblkno) {
+				/*
+				 * Search the second request list for the first
+				 * request at a larger cylinder number.  We go
+				 * before that; if there is no such request, we
+				 * go at end.
+				 */
+				do {
+					if (bp->b_pblkno < bn->b_pblkno)
+						goto insert;
+					bq = bn;
+				} while (bn = bq->b_act.tqe_next);
+				goto insert;		/* after last */
+			}
+			bq = bn;
+		}
+		/*
+		 * No inversions... we will go after the last, and
+		 * be the first request in the second request list.
+		 */
+		goto insert;
+	}
+	/*
+	 * Request is at/after the current request...
+	 * sort in the first request list.
+	 */
+	while (bn = bq->b_act.tqe_next) {
+		/*
+		 * We want to go after the current request if there is an
+		 * inversion after it (i.e. it is the end of the first
+		 * request list), or if the next request is a larger cylinder
+		 * than our request.
+		 */
+		if (bn->b_pblkno < bq->b_pblkno ||
+		    bp->b_pblkno < bn->b_pblkno)
+			goto insert;
+		bq = bn;
+	}
+	/*
+	 * Neither a second list nor a larger request... we go at the end of
+	 * the first list, which is the same as the end of the whole schebang.
+	 */
+insert:
+	TAILQ_INSERT_AFTER(ap, bq, bp, b_act);
+}
+
 void
 disksort(ap, bp)
 	register struct buf *ap, *bp;