Add better support for larger I/O clusters, including larger physical

I/O.  The support is not mature yet, and some of the underlying implementation
needs help.  However, support does exist for IDE devices now.

17 files changed, 207 insertions, 61 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index b1d7bf4..fa544df 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)machdep.c	7.4 (Berkeley) 6/3/91
- *	$Id: machdep.c,v 1.281 1998/01/12 05:16:03 dyson Exp $
+ *	$Id: machdep.c,v 1.282 1998/01/22 17:29:26 dyson Exp $
  */
 
 #include "apm.h"
@@ -302,7 +302,7 @@ again:
 		if( physmem > 1024)
 			nbuf += min((physmem - 1024) / 8, 2048);
 	}
-	nswbuf = max(min(nbuf/4, 128), 16);
+	nswbuf = max(min(nbuf/4, 64), 16);
 
 	valloc(swbuf, struct buf, nswbuf);
 	valloc(buf, struct buf, nbuf);
diff --git a/sys/gnu/ext2fs/ext2_bmap.c b/sys/gnu/ext2fs/ext2_bmap.c
index 84df148..4cab099 100644
--- a/sys/gnu/ext2fs/ext2_bmap.c
+++ b/sys/gnu/ext2fs/ext2_bmap.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ufs_bmap.c	8.7 (Berkeley) 3/21/95
- * $Id: ufs_bmap.c,v 1.16 1997/09/02 20:06:56 bde Exp $
+ * $Id: ufs_bmap.c,v 1.17 1997/11/24 16:33:03 bde Exp $
  */
 
 #include <sys/param.h>
@@ -46,11 +46,13 @@
 #include <sys/vnode.h>
 #include <sys/mount.h>
 #include <sys/resourcevar.h>
+#include <sys/conf.h>
 
 #include <ufs/ufs/quota.h>
 #include <ufs/ufs/inode.h>
 #include <ufs/ufs/ufsmount.h>
 #include <ufs/ufs/ufs_extern.h>
+#include <miscfs/specfs/specdev.h>
 
 /*
  * Bmap converts a the logical block number of a file to its physical block
@@ -124,18 +126,48 @@ ufs_bmaparray(vp, bn, bnp, ap, nump, runp, runb)
 #endif
 
 	if (runp) {
+		*runp = 0;
+	}
+
+	if (runb) {
+		*runb = 0;
+	}
+
+	maxrun = 0;
+	if (runp || runb || (vp->v_maxio == 0)) {
+
+		struct vnode *devvp;
+		int blksize;
+
+		blksize = mp->mnt_stat.f_iosize;
+
 		/*
 		 * XXX
 		 * If MAXPHYS is the largest transfer the disks can handle,
 		 * we probably want maxrun to be 1 block less so that we
 		 * don't create a block larger than the device can handle.
 		 */
-		*runp = 0;
-		maxrun = MAXPHYS / mp->mnt_stat.f_iosize - 1;
-	}
+		devvp = ip->i_devvp;
 
-	if (runb) {
-		*runb = 0;
+		if (devvp && devvp->v_type == VBLK &&
+			(devvp->v_rdev != NODEV) &&
+			(major(devvp->v_rdev) < nblkdev)) {
+			if (bdevsw[major(devvp->v_rdev)]->d_maxio > MAXPHYS) {
+				maxrun = MAXPHYS;
+				vp->v_maxio = MAXPHYS;
+			} else {
+				maxrun = bdevsw[major(devvp->v_rdev)]->d_maxio;
+				vp->v_maxio = bdevsw[major(devvp->v_rdev)]->d_maxio;
+			}
+			maxrun = maxrun / blksize;
+			maxrun -= 1;
+		}
+
+		if (maxrun == 0) {
+			vp->v_maxio = DFLTPHYS;
+			maxrun = DFLTPHYS / blksize;
+			maxrun -= 1;
+		}
 	}
 
 	xap = ap == NULL ? a : ap;
diff --git a/sys/gnu/fs/ext2fs/ext2_bmap.c b/sys/gnu/fs/ext2fs/ext2_bmap.c
index 84df148..4cab099 100644
--- a/sys/gnu/fs/ext2fs/ext2_bmap.c
+++ b/sys/gnu/fs/ext2fs/ext2_bmap.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ufs_bmap.c	8.7 (Berkeley) 3/21/95
- * $Id: ufs_bmap.c,v 1.16 1997/09/02 20:06:56 bde Exp $
+ * $Id: ufs_bmap.c,v 1.17 1997/11/24 16:33:03 bde Exp $
  */
 
 #include <sys/param.h>
@@ -46,11 +46,13 @@
 #include <sys/vnode.h>
 #include <sys/mount.h>
 #include <sys/resourcevar.h>
+#include <sys/conf.h>
 
 #include <ufs/ufs/quota.h>
 #include <ufs/ufs/inode.h>
 #include <ufs/ufs/ufsmount.h>
 #include <ufs/ufs/ufs_extern.h>
+#include <miscfs/specfs/specdev.h>
 
 /*
  * Bmap converts a the logical block number of a file to its physical block
@@ -124,18 +126,48 @@ ufs_bmaparray(vp, bn, bnp, ap, nump, runp, runb)
 #endif
 
 	if (runp) {
+		*runp = 0;
+	}
+
+	if (runb) {
+		*runb = 0;
+	}
+
+	maxrun = 0;
+	if (runp || runb || (vp->v_maxio == 0)) {
+
+		struct vnode *devvp;
+		int blksize;
+
+		blksize = mp->mnt_stat.f_iosize;
+
 		/*
 		 * XXX
 		 * If MAXPHYS is the largest transfer the disks can handle,
 		 * we probably want maxrun to be 1 block less so that we
 		 * don't create a block larger than the device can handle.
 		 */
-		*runp = 0;
-		maxrun = MAXPHYS / mp->mnt_stat.f_iosize - 1;
-	}
+		devvp = ip->i_devvp;
 
-	if (runb) {
-		*runb = 0;
+		if (devvp && devvp->v_type == VBLK &&
+			(devvp->v_rdev != NODEV) &&
+			(major(devvp->v_rdev) < nblkdev)) {
+			if (bdevsw[major(devvp->v_rdev)]->d_maxio > MAXPHYS) {
+				maxrun = MAXPHYS;
+				vp->v_maxio = MAXPHYS;
+			} else {
+				maxrun = bdevsw[major(devvp->v_rdev)]->d_maxio;
+				vp->v_maxio = bdevsw[major(devvp->v_rdev)]->d_maxio;
+			}
+			maxrun = maxrun / blksize;
+			maxrun -= 1;
+		}
+
+		if (maxrun == 0) {
+			vp->v_maxio = DFLTPHYS;
+			maxrun = DFLTPHYS / blksize;
+			maxrun -= 1;
+		}
 	}
 
 	xap = ap == NULL ? a : ap;
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index b1d7bf4..fa544df 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)machdep.c	7.4 (Berkeley) 6/3/91
- *	$Id: machdep.c,v 1.281 1998/01/12 05:16:03 dyson Exp $
+ *	$Id: machdep.c,v 1.282 1998/01/22 17:29:26 dyson Exp $
  */
 
 #include "apm.h"
@@ -302,7 +302,7 @@ again:
 		if( physmem > 1024)
 			nbuf += min((physmem - 1024) / 8, 2048);
 	}
-	nswbuf = max(min(nbuf/4, 128), 16);
+	nswbuf = max(min(nbuf/4, 64), 16);
 
 	valloc(swbuf, struct buf, nswbuf);
 	valloc(buf, struct buf, nbuf);
diff --git a/sys/i386/include/param.h b/sys/i386/include/param.h
index 2e8c637..db3af03 100644
--- a/sys/i386/include/param.h
+++ b/sys/i386/include/param.h
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)param.h	5.8 (Berkeley) 6/28/91
- *	$Id: param.h,v 1.16 1997/08/30 01:22:01 smp Exp smp $
+ *	$Id: param.h,v 1.41 1997/08/30 08:07:50 fsmp Exp $
  */
 
 #ifndef _MACHINE_PARAM_H_
@@ -76,7 +76,8 @@
 #define DEV_BSIZE	(1<<DEV_BSHIFT)
 
 #define BLKDEV_IOSIZE	2048
-#define MAXPHYS		(64 * 1024)	/* max raw I/O transfer size */
+#define DFLTPHYS	(64 * 1024)		/* default max raw I/O transfer size */
+#define MAXPHYS		(128 * 1024)	/* max raw I/O transfer size */
 
 #define IOPAGES	2		/* pages of i/o permission bitmap */
 #define UPAGES	2		/* pages of u-area */
diff --git a/sys/i386/isa/wd.c b/sys/i386/isa/wd.c
index 8812a6b..d214090 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 1.146 1997/12/06 14:27:20 bde Exp $
+ *	$Id: wd.c,v 1.147 1998/01/16 22:13:06 pst Exp $
  */
 
 /* TODO:
@@ -2429,6 +2429,8 @@ static void 	wd_drvinit(void *unused)
 {
 
 	if( ! wd_devsw_installed ) {
+		if (wd_bdevsw.d_maxio == 0)
+			wd_bdevsw.d_maxio = 248 * 512;
 		bdevsw_add_generic(BDEV_MAJOR,CDEV_MAJOR, &wd_bdevsw);
 		wd_devsw_installed = 1;
     	}
diff --git a/sys/kern/kern_physio.c b/sys/kern/kern_physio.c
index 652c37a..c6cb72f 100644
--- a/sys/kern/kern_physio.c
+++ b/sys/kern/kern_physio.c
@@ -16,7 +16,7 @@
  * 4. Modifications may be freely made to this file if the above conditions
  *    are met.
  *
- * $Id: kern_physio.c,v 1.21 1997/08/26 00:15:04 bde Exp $
+ * $Id: kern_physio.c,v 1.22 1997/09/02 20:05:40 bde Exp $
  */
 
 #include <sys/param.h>
@@ -28,6 +28,7 @@
 #include <vm/vm_extern.h>
 
 static void	physwakeup __P((struct buf *bp));
+static struct buf * phygetvpbuf(dev_t dev, int resid);
 
 int
 physio(strategy, bp, dev, rw, minp, uio)
@@ -52,7 +53,7 @@ physio(strategy, bp, dev, rw, minp, uio)
 	curproc->p_flag |= P_PHYSIO;
 
 	/* create and build a buffer header for a transfer */
-	bpa = (struct buf *)getpbuf();
+	bpa = (struct buf *)phygetvpbuf(dev, uio->uio_resid);
 	if (!bp_alloc) {
 		spl = splbio();
 		while (bp->b_flags & B_BUSY) {
@@ -70,12 +71,12 @@ physio(strategy, bp, dev, rw, minp, uio)
 	 */
 	sa = bpa->b_data;
 	bp->b_proc = curproc;
-	bp->b_dev = dev;
 	error = bp->b_error = 0;
 
 	for(i=0;i<uio->uio_iovcnt;i++) {
 		while( uio->uio_iov[i].iov_len) {
 
+			bp->b_dev = dev;
 			bp->b_bcount = uio->uio_iov[i].iov_len;
 			bp->b_flags = B_BUSY | B_PHYS | B_CALL | bufflags;
 			bp->b_iodone = physwakeup;
@@ -168,18 +169,46 @@ u_int
 minphys(bp)
 	struct buf *bp;
 {
-	u_int maxphys = MAXPHYS;
+	u_int maxphys = DFLTPHYS;
+	struct bdevsw *bdsw;
+	int offset;
 
-	if( ((vm_offset_t) bp->b_data) & PAGE_MASK) {
-		maxphys = MAXPHYS - PAGE_SIZE;
+	bdsw = cdevsw[major(bp->b_dev)]->d_bdev;
+
+	if (bdsw && bdsw->d_maxio) {
+		maxphys = bdsw->d_maxio;
+	}
+	if (bp->b_kvasize < maxphys)
+		maxphys = bp->b_kvasize;
+
+	if(((vm_offset_t) bp->b_data) & PAGE_MASK) {
+		maxphys -= PAGE_SIZE;
 	}
 
 	if( bp->b_bcount > maxphys) {
 		bp->b_bcount = maxphys;
 	}
+
 	return bp->b_bcount;
 }
 
+struct buf *
+phygetvpbuf(dev_t dev, int resid)
+{
+	struct bdevsw *bdsw;
+	int maxio;
+
+	bdsw = cdevsw[major(dev)]->d_bdev;
+	if (bdsw == NULL)
+		return getpbuf();
+
+	maxio = bdsw->d_maxio;
+	if (resid > maxio)
+		resid = maxio;
+
+	return getpbuf();
+}
+
 int
 rawread(dev, uio, ioflag)
 	dev_t dev;
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 22acde6..86bf5c7 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -11,7 +11,7 @@
  * 2. Absolutely no warranty of function or purpose is made by the author
  *		John S. Dyson.
  *
- * $Id: vfs_bio.c,v 1.143 1998/01/17 09:16:26 dyson Exp $
+ * $Id: vfs_bio.c,v 1.144 1998/01/22 17:29:51 dyson Exp $
  */
 
 /*
@@ -1132,17 +1132,26 @@ findkvaspace:
 		if (vm_map_findspace(buffer_map,
 			vm_map_min(buffer_map), maxsize, &addr)) {
 			if (kvafreespace > 0) {
-				int tfree = 0;
-				for (bp1 = TAILQ_FIRST(&bufqueues[QUEUE_EMPTY]);
-					bp1 != NULL; bp1 = TAILQ_NEXT(bp1, b_freelist))
-					if (bp1->b_kvasize != 0) {
-						tfree += bp1->b_kvasize;
-						bremfree(bp1);
-						bfreekva(bp1);
-						brelse(bp1);
-						if (tfree >= maxsize)
-							goto findkvaspace;
+				int totfree = 0, freed;
+				do {
+					freed = 0;
+					for (bp1 = TAILQ_FIRST(&bufqueues[QUEUE_EMPTY]);
+						bp1 != NULL; bp1 = TAILQ_NEXT(bp1, b_freelist)) {
+						if (bp1->b_kvasize != 0) {
+							totfree += bp1->b_kvasize;
+							freed = bp1->b_kvasize;
+							bremfree(bp1);
+							bfreekva(bp1);
+							brelse(bp1);
+							break;
+						}
 					}
+				} while (freed);
+				/*
+				 * if we found free space, then retry with the same buffer.
+				 */
+				if (totfree)
+					goto findkvaspace;
 			}
 			bp->b_flags |= B_INVAL;
 			brelse(bp);
diff --git a/sys/kern/vfs_cluster.c b/sys/kern/vfs_cluster.c
index 3d82c5e..407d33d 100644
--- a/sys/kern/vfs_cluster.c
+++ b/sys/kern/vfs_cluster.c
@@ -33,7 +33,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_cluster.c	8.7 (Berkeley) 2/13/94
- * $Id: vfs_cluster.c,v 1.49 1997/11/07 08:53:05 phk Exp $
+ * $Id: vfs_cluster.c,v 1.50 1998/01/06 05:16:01 dyson Exp $
  */
 
 #include <sys/param.h>
@@ -92,12 +92,14 @@ cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
 	long origtotread;
 
 	error = 0;
+	if (vp->v_maxio == 0)
+		vp->v_maxio = DFLTPHYS;
 
 	/*
 	 * Try to limit the amount of read-ahead by a few
 	 * ad-hoc parameters.  This needs work!!!
 	 */
-	racluster = MAXPHYS/size;
+	racluster = vp->v_maxio/size;
 	maxra = 2 * racluster + (totread / size);
 	if (maxra > MAXRA)
 		maxra = MAXRA;
@@ -356,11 +358,13 @@ cluster_rbuild(vp, filesize, lbn, blkno, size, run, fbp)
 	bp->b_bufsize = 0;
 	bp->b_npages = 0;
 
+	if (vp->v_maxio == 0)
+		vp->v_maxio = DFLTPHYS;
 	inc = btodb(size);
 	for (bn = blkno, i = 0; i < run; ++i, bn += inc) {
 		if (i != 0) {
 			if ((bp->b_npages * PAGE_SIZE) +
-				round_page(size) > MAXPHYS)
+				round_page(size) > vp->v_maxio)
 				break;
 
 			if (incore(vp, lbn + i))
@@ -492,6 +496,8 @@ cluster_write(bp, filesize)
 	int async;
 
 	vp = bp->b_vp;
+	if (vp->v_maxio == 0)
+		vp->v_maxio = DFLTPHYS;
 	if (vp->v_type == VREG) {
 		async = vp->v_mount->mnt_flag & MNT_ASYNC;
 		lblocksize = vp->v_mount->mnt_stat.f_iosize;
@@ -507,7 +513,7 @@ cluster_write(bp, filesize)
 
 	if (vp->v_clen == 0 || lbn != vp->v_lastw + 1 ||
 	    (bp->b_blkno != vp->v_lasta + btodb(lblocksize))) {
-		maxclen = MAXPHYS / lblocksize - 1;
+		maxclen = vp->v_maxio / lblocksize - 1;
 		if (vp->v_clen != 0) {
 			/*
 			 * Next block is not sequential.
@@ -703,7 +709,7 @@ cluster_wbuild(vp, size, start_lbn, len)
 
 				if ((tbp->b_bcount != size) ||
 					((bp->b_blkno + dbsize * i) != tbp->b_blkno) ||
-					((tbp->b_npages + bp->b_npages) > (MAXPHYS / PAGE_SIZE))) {
+					((tbp->b_npages + bp->b_npages) > (vp->v_maxio / PAGE_SIZE))) {
 					splx(s);
 					break;
 				}
diff --git a/sys/kern/vfs_export.c b/sys/kern/vfs_export.c
index 2bfc934..8b757e5 100644
--- a/sys/kern/vfs_export.c
+++ b/sys/kern/vfs_export.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_subr.c	8.31 (Berkeley) 5/26/95
- * $Id: vfs_subr.c,v 1.124 1998/01/17 09:16:28 dyson Exp $
+ * $Id: vfs_subr.c,v 1.125 1998/01/22 17:29:52 dyson Exp $
  */
 
 /*
@@ -458,6 +458,7 @@ getnewvnode(tag, mp, vops, vpp)
 		vp->v_clen = 0;
 		vp->v_socket = 0;
 		vp->v_writecount = 0;	/* XXX */
+		vp->v_maxio = 0;
 	} else {
 		simple_unlock(&vnode_free_list_slock);
 		vp = (struct vnode *) zalloc(vnode_zone);
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 2bfc934..8b757e5 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_subr.c	8.31 (Berkeley) 5/26/95
- * $Id: vfs_subr.c,v 1.124 1998/01/17 09:16:28 dyson Exp $
+ * $Id: vfs_subr.c,v 1.125 1998/01/22 17:29:52 dyson Exp $
  */
 
 /*
@@ -458,6 +458,7 @@ getnewvnode(tag, mp, vops, vpp)
 		vp->v_clen = 0;
 		vp->v_socket = 0;
 		vp->v_writecount = 0;	/* XXX */
+		vp->v_maxio = 0;
 	} else {
 		simple_unlock(&vnode_free_list_slock);
 		vp = (struct vnode *) zalloc(vnode_zone);
diff --git a/sys/sys/conf.h b/sys/sys/conf.h
index c39f0ca..ff5662f 100644
--- a/sys/sys/conf.h
+++ b/sys/sys/conf.h
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)conf.h	8.5 (Berkeley) 1/9/95
- * $Id: conf.h,v 1.36 1997/09/27 13:39:46 kato Exp $
+ * $Id: conf.h,v 1.37 1997/11/22 08:35:42 bde Exp $
  */
 
 #ifndef _SYS_CONF_H_
@@ -108,6 +108,7 @@ struct bdevsw {
 	char 		*d_name;	/* name of the driver e.g. audio */
 	struct cdevsw	*d_cdev; 	/* cross pointer to the cdev */
 	int		d_maj;		/* the major number we were assigned */
+	int		d_maxio;
 };
 
 #ifdef KERNEL
diff --git a/sys/sys/linedisc.h b/sys/sys/linedisc.h
index c39f0ca..ff5662f 100644
--- a/sys/sys/linedisc.h
+++ b/sys/sys/linedisc.h
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)conf.h	8.5 (Berkeley) 1/9/95
- * $Id: conf.h,v 1.36 1997/09/27 13:39:46 kato Exp $
+ * $Id: conf.h,v 1.37 1997/11/22 08:35:42 bde Exp $
  */
 
 #ifndef _SYS_CONF_H_
@@ -108,6 +108,7 @@ struct bdevsw {
 	char 		*d_name;	/* name of the driver e.g. audio */
 	struct cdevsw	*d_cdev; 	/* cross pointer to the cdev */
 	int		d_maj;		/* the major number we were assigned */
+	int		d_maxio;
 };
 
 #ifdef KERNEL
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index c9689f0..7f2bd50 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vnode.h	8.7 (Berkeley) 2/4/94
- * $Id: vnode.h,v 1.64 1998/01/12 01:44:08 dyson Exp $
+ * $Id: vnode.h,v 1.65 1998/01/17 09:16:39 dyson Exp $
  */
 
 #ifndef _SYS_VNODE_H_
@@ -107,6 +107,7 @@ struct vnode {
 	daddr_t	v_cstart;			/* start block of cluster */
 	daddr_t	v_lasta;			/* last allocation */
 	int	v_clen;				/* length of current cluster */
+	int	v_maxio;			/* maximum I/O cluster size */
 	struct vm_object *v_object;		/* Place to store VM object */
 	struct	simplelock v_interlock;		/* lock on usecount and flag */
 	struct	lock *v_vnlock;			/* used for non-locking fs's */
diff --git a/sys/ufs/lfs/lfs_segment.c b/sys/ufs/lfs/lfs_segment.c
index 77862de..3916d17 100644
--- a/sys/ufs/lfs/lfs_segment.c
+++ b/sys/ufs/lfs/lfs_segment.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)lfs_segment.c	8.10 (Berkeley) 6/10/95
- * $Id: lfs_segment.c,v 1.25 1997/10/16 11:58:30 phk Exp $
+ * $Id: lfs_segment.c,v 1.26 1997/12/02 21:07:17 phk Exp $
  */
 
 #include <sys/param.h>
@@ -931,7 +931,7 @@ lfs_writeseg(fs, sp)
 	/*
 	 * When we simply write the blocks we lose a rotation for every block
 	 * written.  To avoid this problem, we allocate memory in chunks, copy
-	 * the buffers into the chunk and write the chunk.  MAXPHYS is the
+	 * the buffers into the chunk and write the chunk.  DFLTPHYS is the
 	 * largest size I/O devices can handle.
 	 * When the data is copied to the chunk, turn off the the B_LOCKED bit
 	 * and brelse the buffer (which will move them to the LRU list).  Add
@@ -945,16 +945,16 @@ lfs_writeseg(fs, sp)
 	 */
 	for (bpp = sp->bpp, i = nblocks; i;) {
 		cbp = lfs_newbuf(VTOI(fs->lfs_ivnode)->i_devvp,
-		    (*bpp)->b_blkno, MAXPHYS);
+		    (*bpp)->b_blkno, DFLTPHYS);
 		cbp->b_dev = i_dev;
 		cbp->b_flags |= B_ASYNC | B_BUSY;
 		cbp->b_bcount = 0;
 
 		s = splbio();
 		++fs->lfs_iocount;
-		for (p = cbp->b_data; i && cbp->b_bcount < MAXPHYS; i--) {
+		for (p = cbp->b_data; i && cbp->b_bcount < DFLTPHYS; i--) {
 			bp = *bpp;
-			if (bp->b_bcount > (MAXPHYS - cbp->b_bcount))
+			if (bp->b_bcount > (DFLTPHYS - cbp->b_bcount))
 				break;
 			bpp++;
 
diff --git a/sys/ufs/ufs/ufs_bmap.c b/sys/ufs/ufs/ufs_bmap.c
index 84df148..4cab099 100644
--- a/sys/ufs/ufs/ufs_bmap.c
+++ b/sys/ufs/ufs/ufs_bmap.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ufs_bmap.c	8.7 (Berkeley) 3/21/95
- * $Id: ufs_bmap.c,v 1.16 1997/09/02 20:06:56 bde Exp $
+ * $Id: ufs_bmap.c,v 1.17 1997/11/24 16:33:03 bde Exp $
  */
 
 #include <sys/param.h>
@@ -46,11 +46,13 @@
 #include <sys/vnode.h>
 #include <sys/mount.h>
 #include <sys/resourcevar.h>
+#include <sys/conf.h>
 
 #include <ufs/ufs/quota.h>
 #include <ufs/ufs/inode.h>
 #include <ufs/ufs/ufsmount.h>
 #include <ufs/ufs/ufs_extern.h>
+#include <miscfs/specfs/specdev.h>
 
 /*
  * Bmap converts a the logical block number of a file to its physical block
@@ -124,18 +126,48 @@ ufs_bmaparray(vp, bn, bnp, ap, nump, runp, runb)
 #endif
 
 	if (runp) {
+		*runp = 0;
+	}
+
+	if (runb) {
+		*runb = 0;
+	}
+
+	maxrun = 0;
+	if (runp || runb || (vp->v_maxio == 0)) {
+
+		struct vnode *devvp;
+		int blksize;
+
+		blksize = mp->mnt_stat.f_iosize;
+
 		/*
 		 * XXX
 		 * If MAXPHYS is the largest transfer the disks can handle,
 		 * we probably want maxrun to be 1 block less so that we
 		 * don't create a block larger than the device can handle.
 		 */
-		*runp = 0;
-		maxrun = MAXPHYS / mp->mnt_stat.f_iosize - 1;
-	}
+		devvp = ip->i_devvp;
 
-	if (runb) {
-		*runb = 0;
+		if (devvp && devvp->v_type == VBLK &&
+			(devvp->v_rdev != NODEV) &&
+			(major(devvp->v_rdev) < nblkdev)) {
+			if (bdevsw[major(devvp->v_rdev)]->d_maxio > MAXPHYS) {
+				maxrun = MAXPHYS;
+				vp->v_maxio = MAXPHYS;
+			} else {
+				maxrun = bdevsw[major(devvp->v_rdev)]->d_maxio;
+				vp->v_maxio = bdevsw[major(devvp->v_rdev)]->d_maxio;
+			}
+			maxrun = maxrun / blksize;
+			maxrun -= 1;
+		}
+
+		if (maxrun == 0) {
+			vp->v_maxio = DFLTPHYS;
+			maxrun = DFLTPHYS / blksize;
+			maxrun -= 1;
+		}
 	}
 
 	xap = ap == NULL ? a : ap;
diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
index 44a3bc0..35f491b 100644
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -61,7 +61,7 @@
  * any improvements or extensions that they make and grant Carnegie the
  * rights to redistribute these changes.
  *
- * $Id: vm_pager.c,v 1.30 1997/10/12 20:26:31 phk Exp $
+ * $Id: vm_pager.c,v 1.31 1997/12/29 00:25:06 dyson Exp $
  */
 
 /*
@@ -136,13 +136,11 @@ vm_pager_bufferinit()
 	/*
 	 * Now set up swap and physical I/O buffer headers.
 	 */
-	for (i = 0; i < nswbuf - 1; i++, bp++) {
+	for (i = 0; i < nswbuf; i++, bp++) {
 		TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
 		bp->b_rcred = bp->b_wcred = NOCRED;
 		bp->b_vnbufs.le_next = NOLIST;
 	}
-	bp->b_rcred = bp->b_wcred = NOCRED;
-	bp->b_vnbufs.le_next = NOLIST;
 
 	swapbkva = kmem_alloc_pageable(pager_map, nswbuf * MAXPHYS);
 	if (!swapbkva)