--- sys/sys/file.h.orig	2008-11-27 21:46:47.000000000 +0000
+++ sys/sys/file.h	2008-11-27 21:50:10.000000000 +0000
@@ -133,11 +133,11 @@
 	int	f_msgcount;	/* (f) references from message queue */
 
 	/* DTYPE_VNODE specific fields */
-	int	f_seqcount;	/*
+	int	f_seqcount[2];	/*
 				 * count of sequential accesses -- cleared
 				 * by most seek operations.
 				 */
-	off_t	f_nextoff;	/*
+	off_t	f_nextoff[2];	/*
 				 * offset of next expected read or write
 				 */
 	void	*f_label;	/* Place-holder for struct label pointer. */
--- sys/kern/vfs_vnops.c.orig	2008-11-27 21:47:19.000000000 +0000
+++ sys/kern/vfs_vnops.c	2008-11-27 21:48:59.000000000 +0000
@@ -302,30 +302,30 @@
  */
 static __inline
 int
-sequential_heuristic(struct uio *uio, struct file *fp)
+sequential_heuristic(struct uio *uio, struct file *fp, int idx)
 {
 
-	if ((uio->uio_offset == 0 && fp->f_seqcount > 0) ||
-	    uio->uio_offset == fp->f_nextoff) {
+	if ((uio->uio_offset == 0 && fp->f_seqcount[idx] > 0) ||
+	    uio->uio_offset == fp->f_nextoff[idx]) {
 		/*
 		 * XXX we assume that the filesystem block size is
 		 * the default.  Not true, but still gives us a pretty
 		 * good indicator of how sequential the read operations
 		 * are.
 		 */
-		fp->f_seqcount += (uio->uio_resid + BKVASIZE - 1) / BKVASIZE;
-		if (fp->f_seqcount > IO_SEQMAX)
-			fp->f_seqcount = IO_SEQMAX;
-		return(fp->f_seqcount << IO_SEQSHIFT);
+		fp->f_seqcount[idx] += (uio->uio_resid + BKVASIZE - 1) / BKVASIZE;
+		if (fp->f_seqcount[idx] > IO_SEQMAX)
+			fp->f_seqcount[idx] = IO_SEQMAX;
+		return(fp->f_seqcount[idx] << IO_SEQSHIFT);
 	}
 
 	/*
 	 * Not sequential, quick draw-down of seqcount
 	 */
-	if (fp->f_seqcount > 1)
-		fp->f_seqcount = 1;
+	if (fp->f_seqcount[idx] > 1)
+		fp->f_seqcount[idx] = 1;
 	else
-		fp->f_seqcount = 0;
+		fp->f_seqcount[idx] = 0;
 	return(0);
 }
 
@@ -517,7 +517,7 @@
 	} else
 		vn_lock(vp, LK_SHARED | LK_RETRY, td);
 
-	ioflag |= sequential_heuristic(uio, fp);
+	ioflag |= sequential_heuristic(uio, fp, 0);
 
 #ifdef MAC
 	error = mac_check_vnode_read(active_cred, fp->f_cred, vp);
@@ -532,7 +532,7 @@
 		fp->f_vnread_flags = 0;
 		FILE_UNLOCK(fp);
 	}
-	fp->f_nextoff = uio->uio_offset;
+	fp->f_nextoff[0] = uio->uio_offset;
 	VOP_UNLOCK(vp, 0, td);
 	VFS_UNLOCK_GIANT(vfslocked);
 	return (error);
@@ -578,7 +578,7 @@
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
 	if ((flags & FOF_OFFSET) == 0)
 		uio->uio_offset = fp->f_offset;
-	ioflag |= sequential_heuristic(uio, fp);
+	ioflag |= sequential_heuristic(uio, fp, 1);
 #ifdef MAC
 	error = mac_check_vnode_write(active_cred, fp->f_cred, vp);
 	if (error == 0)
@@ -586,7 +586,7 @@
 		error = VOP_WRITE(vp, uio, ioflag, fp->f_cred);
 	if ((flags & FOF_OFFSET) == 0)
 		fp->f_offset = uio->uio_offset;
-	fp->f_nextoff = uio->uio_offset;
+	fp->f_nextoff[1] = uio->uio_offset;
 	VOP_UNLOCK(vp, 0, td);
 	if (vp->v_type != VCHR)
 		vn_finished_write(mp);
--- sys/kern/vfs_syscalls.c.orig	2008-11-27 21:47:07.000000000 +0000
+++ sys/kern/vfs_syscalls.c	2008-11-27 21:49:18.000000000 +0000
@@ -1076,7 +1076,7 @@
 	if (fp->f_data == NULL)
 		fp->f_data = vp;
 	fp->f_flag = flags & FMASK;
-	fp->f_seqcount = 1;
+	fp->f_seqcount[0] = fp->f_seqcount[1] = 1;
 	fp->f_type = (vp->v_type == VFIFO ? DTYPE_FIFO : DTYPE_VNODE);
 	if (fp->f_ops == &badfileops)
 		fp->f_ops = &vnops;
--- sys/fs/devfs/devfs_vnops.c.orig	2008-11-27 21:47:45.000000000 +0000
+++ sys/fs/devfs/devfs_vnops.c	2008-11-27 21:49:42.000000000 +0000
@@ -1005,7 +1005,7 @@
 
 	if ((flags & FOF_OFFSET) == 0)
 		fp->f_offset = uio->uio_offset;
-	fp->f_nextoff = uio->uio_offset;
+	fp->f_nextoff[0] = uio->uio_offset;
 	return (error);
 }
 
@@ -1437,7 +1437,7 @@
 
 	if ((flags & FOF_OFFSET) == 0)
 		fp->f_offset = uio->uio_offset;
-	fp->f_nextoff = uio->uio_offset;
+	fp->f_nextoff[1] = uio->uio_offset;
 	return (error);
 }