Clustered read and write are switched at mount-option level.

1. Clustered I/O is switched by the MNT_NOCLUSTERR and MNT_NOCLUSTERW
   bits of the mnt_flag.  The sysctl variables, vfs.foo.doclusterread
   and vfs.foo.doclusterwrite are deleted.  Only mount option can
   control clustered I/O from userland.
2. When foofs_mount mounts block device, foofs_mount checks D_CLUSTERR
   and D_CLUSTERW bits of the d_flags member in the block device switch
   table.  If D_NOCLUSTERR / D_NOCLUSTERW are set, MNT_NOCLUSTERR /
   MNT_NOCLUSTERW bits will be set.  In this case, MNT_NOCLUSTERR and
   MNT_NOCLUSTERW cannot be cleared from userland.
3. Vnode driver disables both clustered read and write.
4. Union filesystem disables clutered write.

Reviewed by:	bde

27 files changed, 161 insertions, 155 deletions

diff --git a/sys/dev/vn/vn.c b/sys/dev/vn/vn.c
index 6cb4856..d851d2a 100644
--- a/sys/dev/vn/vn.c
+++ b/sys/dev/vn/vn.c
@@ -38,7 +38,7 @@
  * from: Utah Hdr: vn.c 1.13 94/04/02
  *
  *	from: @(#)vn.c	8.6 (Berkeley) 4/1/94
- *	$Id: vn.c,v 1.48 1997/06/14 13:56:09 bde Exp $
+ *	$Id: vn.c,v 1.49 1997/08/14 13:44:19 kato Exp $
  */
 
 /*
@@ -101,8 +101,8 @@ static	d_strategy_t	vnstrategy;
 #define BDEV_MAJOR 15
 static struct cdevsw vn_cdevsw;
 static struct bdevsw vn_bdevsw = 
-	{ vnopen,	vnclose,	vnstrategy,	vnioctl,	/*15*/
-	  vndump,	vnsize,		D_DISK,	"vn",	&vn_cdevsw,	-1 };
+	{ vnopen, vnclose, vnstrategy,                      vnioctl,	/*15*/
+	  vndump, vnsize,  D_DISK | D_NOCLUSTERRW, "vn",    &vn_cdevsw, -1 };
 
 
 #ifdef DEBUG
diff --git a/sys/fs/cd9660/cd9660_vfsops.c b/sys/fs/cd9660/cd9660_vfsops.c
index c652ab1..b29a042 100644
--- a/sys/fs/cd9660/cd9660_vfsops.c
+++ b/sys/fs/cd9660/cd9660_vfsops.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)cd9660_vfsops.c	8.18 (Berkeley) 5/22/95
- * $Id: cd9660_vfsops.c,v 1.27 1997/08/16 19:15:00 wollman Exp $
+ * $Id: cd9660_vfsops.c,v 1.28 1997/09/07 16:20:42 bde Exp $
  */
 
 #include <sys/param.h>
@@ -183,9 +183,11 @@ cd9660_mount(mp, path, data, ndp, p)
 	int error;
 	struct iso_mnt *imp = 0;
 
-	if ((mp->mnt_flag & MNT_ROOTFS) != 0)
+	if ((mp->mnt_flag & MNT_ROOTFS) != 0) {
+		if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
 		return (iso_mountroot(mp, p));
-
+	}
 	if ((error = copyin(data, (caddr_t)&args, sizeof (struct iso_args))))
 		return (error);
 
@@ -195,9 +197,13 @@ cd9660_mount(mp, path, data, ndp, p)
 	/*
 	 * If updating, check whether changing from read-only to
 	 * read/write; if there is no device name, that's all we do.
+	 * Disallow clearing MNT_NOCLUSTERR flag, if block device requests.
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
 		imp = VFSTOISOFS(mp);
+		if (bdevsw[major(imp->im_devvp->v_rdev)]->d_flags &
+		    D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
 		if (args.fspec == 0)
 			return (vfs_export(mp, &imp->im_export, &args.export));
 	}
@@ -218,9 +224,11 @@ cd9660_mount(mp, path, data, ndp, p)
 		vrele(devvp);
 		return ENXIO;
 	}
-	if ((mp->mnt_flag & MNT_UPDATE) == 0)
+	if ((mp->mnt_flag & MNT_UPDATE) == 0) {
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
 		error = iso_mountfs(devvp, mp, p, &args);
-	else {
+	} else {
 		if (devvp != imp->im_devvp)
 			error = EINVAL;	/* needs translation */
 		else
diff --git a/sys/fs/cd9660/cd9660_vnops.c b/sys/fs/cd9660/cd9660_vnops.c
index e518e89..cddb6fd 100644
--- a/sys/fs/cd9660/cd9660_vnops.c
+++ b/sys/fs/cd9660/cd9660_vnops.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)cd9660_vnops.c	8.19 (Berkeley) 5/27/95
- * $Id: cd9660_vnops.c,v 1.38 1997/09/14 02:57:43 peter Exp $
+ * $Id: cd9660_vnops.c,v 1.39 1997/09/21 04:22:40 dyson Exp $
  */
 
 #include <sys/param.h>
@@ -81,17 +81,6 @@ static int cd9660_print __P((struct vop_print_args *));
 static int cd9660_islocked __P((struct vop_islocked_args *));
 
 /*
- * Sysctl values for the cd9660 filesystem.
- */
-#define	CD9660_CLUSTERREAD	1	/* cluster reading enabled */
-#define	CD9660_MAXID		2	/* number of valid cd9660 ids */
-
-#define	CD9660_NAMES { \
-	{0, 0}, \
-	{ "doclusterread", CTLTYPE_INT}, \
-}
-
-/*
  * Setattr call. Only allowed for block and character special devices.
  */
 int
@@ -299,11 +288,6 @@ cd9660_getattr(ap)
 	return (0);
 }
 
-static int	cd9660_doclusterread = 1;
-SYSCTL_NODE(_vfs, MOUNT_CD9660, cd9660, CTLFLAG_RW, 0, "CD9660 filesystem");
-SYSCTL_INT(_vfs_cd9660, CD9660_CLUSTERREAD, doclusterread,
-		   CTLFLAG_RW, &cd9660_doclusterread, 0, "");
-
 /*
  * Vnode op for reading.
  */
@@ -344,7 +328,7 @@ cd9660_read(ap)
 			n = diff;
 		size = blksize(imp, ip, lbn);
 		rablock = lbn + 1;
-		if (cd9660_doclusterread) {
+		if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
 			if (lblktosize(imp, rablock) <= ip->i_size)
 				error = cluster_read(vp, (off_t)ip->i_size,
 				         lbn, size, NOCRED, uio->uio_resid,
diff --git a/sys/fs/specfs/spec_vnops.c b/sys/fs/specfs/spec_vnops.c
index b5407ee..dd05fc0 100644
--- a/sys/fs/specfs/spec_vnops.c
+++ b/sys/fs/specfs/spec_vnops.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)spec_vnops.c	8.14 (Berkeley) 5/21/95
- * $Id: spec_vnops.c,v 1.41 1997/09/02 20:06:12 bde Exp $
+ * $Id: spec_vnops.c,v 1.42 1997/09/14 02:58:02 peter Exp $
  */
 
 #include <sys/param.h>
@@ -176,7 +176,8 @@ spec_open(ap)
 			 */
 			if (securelevel >= 2
 			    && cdevsw[maj]->d_bdev
-			    && cdevsw[maj]->d_bdev->d_flags == D_DISK)
+			    && (cdevsw[maj]->d_bdev->d_flags & D_TYPEMASK) == 
+			    D_DISK)
 				return (EPERM);
 			/*
 			 * When running in secure mode, do not allow opens
@@ -220,7 +221,8 @@ spec_open(ap)
 		 * opens for writing of any disk block devices.
 		 */
 		if (securelevel >= 2 && ap->a_cred != FSCRED &&
-		    (ap->a_mode & FWRITE) && bdevsw[maj]->d_flags == D_DISK)
+		    (ap->a_mode & FWRITE) &&
+		    (bdevsw[maj]->d_flags & D_TYPEMASK) == D_DISK)
 			return (EPERM);
 		/*
 		 * Do not allow opens of block devices that are
@@ -422,7 +424,8 @@ spec_ioctl(ap)
 
 	case VBLK:
 		if (ap->a_command == 0 && (int)ap->a_data == B_TAPE)
-			if (bdevsw[major(dev)]->d_flags == D_TAPE)
+			if ((bdevsw[major(dev)]->d_flags & D_TYPEMASK) ==
+			    D_TAPE)
 				return (0);
 			else
 				return (1);
diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c
index e7954be..8478a1c 100644
--- a/sys/fs/unionfs/union_vfsops.c
+++ b/sys/fs/unionfs/union_vfsops.c
@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)union_vfsops.c	8.20 (Berkeley) 5/20/95
- * $Id: union_vfsops.c,v 1.18 1997/08/02 14:32:29 bde Exp $
+ * $Id: union_vfsops.c,v 1.19 1997/08/16 19:15:22 wollman Exp $
  */
 
 /*
@@ -103,6 +103,11 @@ union_mount(mp, path, data, ndp, p)
 #endif
 
 	/*
+	 * Disable clustered write, otherwise system becomes unstable.
+	 */
+	mp->mnt_flag |= MNT_NOCLUSTERW;
+
+	/*
 	 * Update is a no-op
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
diff --git a/sys/gnu/ext2fs/ext2_extern.h b/sys/gnu/ext2fs/ext2_extern.h
index 277106b..4c32799 100644
--- a/sys/gnu/ext2fs/ext2_extern.h
+++ b/sys/gnu/ext2fs/ext2_extern.h
@@ -42,19 +42,6 @@
 #ifndef _SYS_GNU_EXT2FS_EXT2_EXTERN_H_
 #define	_SYS_GNU_EXT2FS_EXT2_EXTERN_H_
 
-/*
- * Sysctl values for the ext2fs filesystem.
- */
-#define	EXT2FS_CLUSTERREAD		1		/* cluster reading enabled */
-#define	EXT2FS_CLUSTERWRITE		2		/* cluster writing enable */
-#define	EXT2FS_MAXID			3		/* number of valid ext2fs ids */
-
-#define	EXT2FS_NAMES {\
-	{0, 0}, \
-	{ "doclusterread", CTLTYPE_INT }, \
-	{ "doculsterwrite", CTLTYPE_INT }, \
-}
-
 struct dinode;
 struct ext2_inode;
 struct inode;
diff --git a/sys/gnu/ext2fs/ext2_readwrite.c b/sys/gnu/ext2fs/ext2_readwrite.c
index e28cd0a..986bc14 100644
--- a/sys/gnu/ext2fs/ext2_readwrite.c
+++ b/sys/gnu/ext2fs/ext2_readwrite.c
@@ -112,7 +112,7 @@ READ(ap)
 
 		if (lblktosize(fs, nextlbn) >= ip->i_size)
 			error = bread(vp, lbn, size, NOCRED, &bp);
-		else if (ext2_doclusterread)
+		else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0)
 			error = cluster_read(vp,
 			    ip->i_size, lbn, size, NOCRED,
 				uio->uio_resid, (ap->a_ioflag >> 16), &bp);
@@ -277,7 +277,7 @@ WRITE(ap)
 		if (ioflag & IO_SYNC) {
 			(void)bwrite(bp);
 		} else if (xfersize + blkoffset == fs->s_frag_size) {
-			if (ext2_doclusterwrite) {
+			if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0) {
 #if defined(__FreeBSD__)
 				bp->b_flags |= B_CLUSTEROK;
 #endif
diff --git a/sys/gnu/ext2fs/ext2_vfsops.c b/sys/gnu/ext2fs/ext2_vfsops.c
index 7aef5f6..11d1b33 100644
--- a/sys/gnu/ext2fs/ext2_vfsops.c
+++ b/sys/gnu/ext2fs/ext2_vfsops.c
@@ -149,6 +149,10 @@ ext2_mountroot()
 	bzero((char *)mp, (u_long)sizeof(struct mount));
 	mp->mnt_op = &ext2fs_vfsops;
 	mp->mnt_flag = MNT_RDONLY;
+	if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERR)
+		mp->mnt_flag |= MNT_NOCLUSTERR;
+	if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERW)
+		mp->mnt_flag |= MNT_NOCLUSTERW;
 	if (error = ext2_mountfs(rootvp, mp, p)) {
 		bsd_free(mp, M_MOUNT);
 		return (error);
@@ -206,11 +210,17 @@ ext2_mount(mp, path, data, ndp, p)
 	/*
 	 * If updating, check whether changing from read-only to
 	 * read/write; if there is no device name, that's all we do.
+	 * Disallow clearing MNT_NOCLUSTERR and MNT_NOCLUSTERW flags,
+	 * if block device requests.
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
 		ump = VFSTOUFS(mp);
 		fs = ump->um_e2fs;
 		error = 0;
+		if (bdevsw[major(ump->um_dev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(ump->um_dev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
 		if (fs->s_rd_only == 0 && (mp->mnt_flag & MNT_RDONLY)) {
 			flags = WRITECLOSE;
 			if (mp->mnt_flag & MNT_FORCE)
@@ -255,9 +265,13 @@ ext2_mount(mp, path, data, ndp, p)
 		vrele(devvp);
 		return (ENXIO);
 	}
-	if ((mp->mnt_flag & MNT_UPDATE) == 0)
+	if ((mp->mnt_flag & MNT_UPDATE) == 0) {
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
 		error = ext2_mountfs(devvp, mp, p);
-	else {
+	} else {
 		if (devvp != ump->um_devvp)
 			error = EINVAL;	/* needs translation */
 		else
diff --git a/sys/gnu/ext2fs/ext2_vnops.c b/sys/gnu/ext2fs/ext2_vnops.c
index 583164b..94fe0a7 100644
--- a/sys/gnu/ext2fs/ext2_vnops.c
+++ b/sys/gnu/ext2fs/ext2_vnops.c
@@ -237,17 +237,6 @@ static struct vnodeopv_desc ext2fs_fifoop_opv_desc =
 	VNODEOP_SET(ext2fs_fifoop_opv_desc);
 #endif
 
-/*
- * Enabling cluster read/write operations.
- */
-static int	ext2_doclusterread = 1;
-static int	ext2_doclusterwrite = 1;
-SYSCTL_NODE(_vfs, MOUNT_EXT2FS, ext2fs, CTLFLAG_RW, 0, "EXT2FS filesystem");
-SYSCTL_INT(_vfs_ext2fs, EXT2FS_CLUSTERREAD, doclusterread,
-		   CTLFLAG_RW, &ext2_doclusterread, 0, "");
-SYSCTL_INT(_vfs_ext2fs, EXT2FS_CLUSTERWRITE, doclusterwrite,
-		   CTLFLAG_RW, &ext2_doclusterwrite, 0, "");
-
 #include <gnu/ext2fs/ext2_readwrite.c>
 
 /*
diff --git a/sys/gnu/fs/ext2fs/ext2_extern.h b/sys/gnu/fs/ext2fs/ext2_extern.h
index 277106b..4c32799 100644
--- a/sys/gnu/fs/ext2fs/ext2_extern.h
+++ b/sys/gnu/fs/ext2fs/ext2_extern.h
@@ -42,19 +42,6 @@
 #ifndef _SYS_GNU_EXT2FS_EXT2_EXTERN_H_
 #define	_SYS_GNU_EXT2FS_EXT2_EXTERN_H_
 
-/*
- * Sysctl values for the ext2fs filesystem.
- */
-#define	EXT2FS_CLUSTERREAD		1		/* cluster reading enabled */
-#define	EXT2FS_CLUSTERWRITE		2		/* cluster writing enable */
-#define	EXT2FS_MAXID			3		/* number of valid ext2fs ids */
-
-#define	EXT2FS_NAMES {\
-	{0, 0}, \
-	{ "doclusterread", CTLTYPE_INT }, \
-	{ "doculsterwrite", CTLTYPE_INT }, \
-}
-
 struct dinode;
 struct ext2_inode;
 struct inode;
diff --git a/sys/gnu/fs/ext2fs/ext2_readwrite.c b/sys/gnu/fs/ext2fs/ext2_readwrite.c
index e28cd0a..986bc14 100644
--- a/sys/gnu/fs/ext2fs/ext2_readwrite.c
+++ b/sys/gnu/fs/ext2fs/ext2_readwrite.c
@@ -112,7 +112,7 @@ READ(ap)
 
 		if (lblktosize(fs, nextlbn) >= ip->i_size)
 			error = bread(vp, lbn, size, NOCRED, &bp);
-		else if (ext2_doclusterread)
+		else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0)
 			error = cluster_read(vp,
 			    ip->i_size, lbn, size, NOCRED,
 				uio->uio_resid, (ap->a_ioflag >> 16), &bp);
@@ -277,7 +277,7 @@ WRITE(ap)
 		if (ioflag & IO_SYNC) {
 			(void)bwrite(bp);
 		} else if (xfersize + blkoffset == fs->s_frag_size) {
-			if (ext2_doclusterwrite) {
+			if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0) {
 #if defined(__FreeBSD__)
 				bp->b_flags |= B_CLUSTEROK;
 #endif
diff --git a/sys/gnu/fs/ext2fs/ext2_vfsops.c b/sys/gnu/fs/ext2fs/ext2_vfsops.c
index 7aef5f6..11d1b33 100644
--- a/sys/gnu/fs/ext2fs/ext2_vfsops.c
+++ b/sys/gnu/fs/ext2fs/ext2_vfsops.c
@@ -149,6 +149,10 @@ ext2_mountroot()
 	bzero((char *)mp, (u_long)sizeof(struct mount));
 	mp->mnt_op = &ext2fs_vfsops;
 	mp->mnt_flag = MNT_RDONLY;
+	if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERR)
+		mp->mnt_flag |= MNT_NOCLUSTERR;
+	if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERW)
+		mp->mnt_flag |= MNT_NOCLUSTERW;
 	if (error = ext2_mountfs(rootvp, mp, p)) {
 		bsd_free(mp, M_MOUNT);
 		return (error);
@@ -206,11 +210,17 @@ ext2_mount(mp, path, data, ndp, p)
 	/*
 	 * If updating, check whether changing from read-only to
 	 * read/write; if there is no device name, that's all we do.
+	 * Disallow clearing MNT_NOCLUSTERR and MNT_NOCLUSTERW flags,
+	 * if block device requests.
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
 		ump = VFSTOUFS(mp);
 		fs = ump->um_e2fs;
 		error = 0;
+		if (bdevsw[major(ump->um_dev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(ump->um_dev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
 		if (fs->s_rd_only == 0 && (mp->mnt_flag & MNT_RDONLY)) {
 			flags = WRITECLOSE;
 			if (mp->mnt_flag & MNT_FORCE)
@@ -255,9 +265,13 @@ ext2_mount(mp, path, data, ndp, p)
 		vrele(devvp);
 		return (ENXIO);
 	}
-	if ((mp->mnt_flag & MNT_UPDATE) == 0)
+	if ((mp->mnt_flag & MNT_UPDATE) == 0) {
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
 		error = ext2_mountfs(devvp, mp, p);
-	else {
+	} else {
 		if (devvp != ump->um_devvp)
 			error = EINVAL;	/* needs translation */
 		else
diff --git a/sys/gnu/fs/ext2fs/ext2_vnops.c b/sys/gnu/fs/ext2fs/ext2_vnops.c
index 583164b..94fe0a7 100644
--- a/sys/gnu/fs/ext2fs/ext2_vnops.c
+++ b/sys/gnu/fs/ext2fs/ext2_vnops.c
@@ -237,17 +237,6 @@ static struct vnodeopv_desc ext2fs_fifoop_opv_desc =
 	VNODEOP_SET(ext2fs_fifoop_opv_desc);
 #endif
 
-/*
- * Enabling cluster read/write operations.
- */
-static int	ext2_doclusterread = 1;
-static int	ext2_doclusterwrite = 1;
-SYSCTL_NODE(_vfs, MOUNT_EXT2FS, ext2fs, CTLFLAG_RW, 0, "EXT2FS filesystem");
-SYSCTL_INT(_vfs_ext2fs, EXT2FS_CLUSTERREAD, doclusterread,
-		   CTLFLAG_RW, &ext2_doclusterread, 0, "");
-SYSCTL_INT(_vfs_ext2fs, EXT2FS_CLUSTERWRITE, doclusterwrite,
-		   CTLFLAG_RW, &ext2_doclusterwrite, 0, "");
-
 #include <gnu/ext2fs/ext2_readwrite.c>
 
 /*
diff --git a/sys/isofs/cd9660/cd9660_vfsops.c b/sys/isofs/cd9660/cd9660_vfsops.c
index c652ab1..b29a042 100644
--- a/sys/isofs/cd9660/cd9660_vfsops.c
+++ b/sys/isofs/cd9660/cd9660_vfsops.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)cd9660_vfsops.c	8.18 (Berkeley) 5/22/95
- * $Id: cd9660_vfsops.c,v 1.27 1997/08/16 19:15:00 wollman Exp $
+ * $Id: cd9660_vfsops.c,v 1.28 1997/09/07 16:20:42 bde Exp $
  */
 
 #include <sys/param.h>
@@ -183,9 +183,11 @@ cd9660_mount(mp, path, data, ndp, p)
 	int error;
 	struct iso_mnt *imp = 0;
 
-	if ((mp->mnt_flag & MNT_ROOTFS) != 0)
+	if ((mp->mnt_flag & MNT_ROOTFS) != 0) {
+		if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
 		return (iso_mountroot(mp, p));
-
+	}
 	if ((error = copyin(data, (caddr_t)&args, sizeof (struct iso_args))))
 		return (error);
 
@@ -195,9 +197,13 @@ cd9660_mount(mp, path, data, ndp, p)
 	/*
 	 * If updating, check whether changing from read-only to
 	 * read/write; if there is no device name, that's all we do.
+	 * Disallow clearing MNT_NOCLUSTERR flag, if block device requests.
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
 		imp = VFSTOISOFS(mp);
+		if (bdevsw[major(imp->im_devvp->v_rdev)]->d_flags &
+		    D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
 		if (args.fspec == 0)
 			return (vfs_export(mp, &imp->im_export, &args.export));
 	}
@@ -218,9 +224,11 @@ cd9660_mount(mp, path, data, ndp, p)
 		vrele(devvp);
 		return ENXIO;
 	}
-	if ((mp->mnt_flag & MNT_UPDATE) == 0)
+	if ((mp->mnt_flag & MNT_UPDATE) == 0) {
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
 		error = iso_mountfs(devvp, mp, p, &args);
-	else {
+	} else {
 		if (devvp != imp->im_devvp)
 			error = EINVAL;	/* needs translation */
 		else
diff --git a/sys/isofs/cd9660/cd9660_vnops.c b/sys/isofs/cd9660/cd9660_vnops.c
index e518e89..cddb6fd 100644
--- a/sys/isofs/cd9660/cd9660_vnops.c
+++ b/sys/isofs/cd9660/cd9660_vnops.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)cd9660_vnops.c	8.19 (Berkeley) 5/27/95
- * $Id: cd9660_vnops.c,v 1.38 1997/09/14 02:57:43 peter Exp $
+ * $Id: cd9660_vnops.c,v 1.39 1997/09/21 04:22:40 dyson Exp $
  */
 
 #include <sys/param.h>
@@ -81,17 +81,6 @@ static int cd9660_print __P((struct vop_print_args *));
 static int cd9660_islocked __P((struct vop_islocked_args *));
 
 /*
- * Sysctl values for the cd9660 filesystem.
- */
-#define	CD9660_CLUSTERREAD	1	/* cluster reading enabled */
-#define	CD9660_MAXID		2	/* number of valid cd9660 ids */
-
-#define	CD9660_NAMES { \
-	{0, 0}, \
-	{ "doclusterread", CTLTYPE_INT}, \
-}
-
-/*
  * Setattr call. Only allowed for block and character special devices.
  */
 int
@@ -299,11 +288,6 @@ cd9660_getattr(ap)
 	return (0);
 }
 
-static int	cd9660_doclusterread = 1;
-SYSCTL_NODE(_vfs, MOUNT_CD9660, cd9660, CTLFLAG_RW, 0, "CD9660 filesystem");
-SYSCTL_INT(_vfs_cd9660, CD9660_CLUSTERREAD, doclusterread,
-		   CTLFLAG_RW, &cd9660_doclusterread, 0, "");
-
 /*
  * Vnode op for reading.
  */
@@ -344,7 +328,7 @@ cd9660_read(ap)
 			n = diff;
 		size = blksize(imp, ip, lbn);
 		rablock = lbn + 1;
-		if (cd9660_doclusterread) {
+		if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
 			if (lblktosize(imp, rablock) <= ip->i_size)
 				error = cluster_read(vp, (off_t)ip->i_size,
 				         lbn, size, NOCRED, uio->uio_resid,
diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
index 1030648..fba334b 100644
--- a/sys/kern/kern_conf.c
+++ b/sys/kern/kern_conf.c
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $Id: kern_conf.c,v 1.20 1997/09/21 22:14:54 julian Exp $
+ * $Id: kern_conf.c,v 1.21 1997/09/21 22:20:12 julian Exp $
  */
 
 #include <sys/param.h>
@@ -198,10 +198,12 @@ bdevsw_add_generic(int bdev, int cdev, struct bdevsw *bdevsw)
 	/*
 	 * XXX hack alert.
 	 */
-	if (isdisk(makedev(bdev, 0), VBLK) && bdevsw->d_flags != D_DISK) {
+	if (isdisk(makedev(bdev, 0), VBLK) &&
+	    (bdevsw->d_flags & D_TYPEMASK) != D_DISK) {
 	    printf("bdevsw_add_generic: adding D_DISK flag for device %d\n",
 		   bdev);
-	    bdevsw->d_flags = D_DISK;
+	    bdevsw->d_flags &= ~D_TYPEMASK;
+	    bdevsw->d_flags |= D_DISK;
 	}
 	cdevsw_make(bdevsw);
 	dev = makedev(cdev, 0);
diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index b8da035..d3b100b 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_syscalls.c	8.13 (Berkeley) 4/15/94
- * $Id: vfs_syscalls.c,v 1.72 1997/09/21 04:23:03 dyson Exp $
+ * $Id: vfs_syscalls.c,v 1.73 1997/09/24 07:46:54 phk Exp $
  */
 
 /*
@@ -253,10 +253,11 @@ update:
 	else if (mp->mnt_flag & MNT_RDONLY)
 		mp->mnt_flag |= MNT_WANTRDWR;
 	mp->mnt_flag &=~ (MNT_NOSUID | MNT_NOEXEC | MNT_NODEV |
-	    MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME);
+	    MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME |
+	    MNT_NOCLUSTERR | MNT_NOCLUSTERW);
 	mp->mnt_flag |= SCARG(uap, flags) & (MNT_NOSUID | MNT_NOEXEC |
 	    MNT_NODEV | MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_FORCE |
-	    MNT_NOATIME);
+	    MNT_NOATIME | MNT_NOCLUSTERR | MNT_NOCLUSTERW);
 	/*
 	 * Mount the filesystem.
 	 */
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index b8da035..d3b100b 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_syscalls.c	8.13 (Berkeley) 4/15/94
- * $Id: vfs_syscalls.c,v 1.72 1997/09/21 04:23:03 dyson Exp $
+ * $Id: vfs_syscalls.c,v 1.73 1997/09/24 07:46:54 phk Exp $
  */
 
 /*
@@ -253,10 +253,11 @@ update:
 	else if (mp->mnt_flag & MNT_RDONLY)
 		mp->mnt_flag |= MNT_WANTRDWR;
 	mp->mnt_flag &=~ (MNT_NOSUID | MNT_NOEXEC | MNT_NODEV |
-	    MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME);
+	    MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_NOATIME |
+	    MNT_NOCLUSTERR | MNT_NOCLUSTERW);
 	mp->mnt_flag |= SCARG(uap, flags) & (MNT_NOSUID | MNT_NOEXEC |
 	    MNT_NODEV | MNT_SYNCHRONOUS | MNT_UNION | MNT_ASYNC | MNT_FORCE |
-	    MNT_NOATIME);
+	    MNT_NOATIME | MNT_NOCLUSTERR | MNT_NOCLUSTERW);
 	/*
 	 * Mount the filesystem.
 	 */
diff --git a/sys/miscfs/specfs/spec_vnops.c b/sys/miscfs/specfs/spec_vnops.c
index b5407ee..dd05fc0 100644
--- a/sys/miscfs/specfs/spec_vnops.c
+++ b/sys/miscfs/specfs/spec_vnops.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)spec_vnops.c	8.14 (Berkeley) 5/21/95
- * $Id: spec_vnops.c,v 1.41 1997/09/02 20:06:12 bde Exp $
+ * $Id: spec_vnops.c,v 1.42 1997/09/14 02:58:02 peter Exp $
  */
 
 #include <sys/param.h>
@@ -176,7 +176,8 @@ spec_open(ap)
 			 */
 			if (securelevel >= 2
 			    && cdevsw[maj]->d_bdev
-			    && cdevsw[maj]->d_bdev->d_flags == D_DISK)
+			    && (cdevsw[maj]->d_bdev->d_flags & D_TYPEMASK) == 
+			    D_DISK)
 				return (EPERM);
 			/*
 			 * When running in secure mode, do not allow opens
@@ -220,7 +221,8 @@ spec_open(ap)
 		 * opens for writing of any disk block devices.
 		 */
 		if (securelevel >= 2 && ap->a_cred != FSCRED &&
-		    (ap->a_mode & FWRITE) && bdevsw[maj]->d_flags == D_DISK)
+		    (ap->a_mode & FWRITE) &&
+		    (bdevsw[maj]->d_flags & D_TYPEMASK) == D_DISK)
 			return (EPERM);
 		/*
 		 * Do not allow opens of block devices that are
@@ -422,7 +424,8 @@ spec_ioctl(ap)
 
 	case VBLK:
 		if (ap->a_command == 0 && (int)ap->a_data == B_TAPE)
-			if (bdevsw[major(dev)]->d_flags == D_TAPE)
+			if ((bdevsw[major(dev)]->d_flags & D_TYPEMASK) ==
+			    D_TAPE)
 				return (0);
 			else
 				return (1);
diff --git a/sys/miscfs/union/union_vfsops.c b/sys/miscfs/union/union_vfsops.c
index e7954be..8478a1c 100644
--- a/sys/miscfs/union/union_vfsops.c
+++ b/sys/miscfs/union/union_vfsops.c
@@ -35,7 +35,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)union_vfsops.c	8.20 (Berkeley) 5/20/95
- * $Id: union_vfsops.c,v 1.18 1997/08/02 14:32:29 bde Exp $
+ * $Id: union_vfsops.c,v 1.19 1997/08/16 19:15:22 wollman Exp $
  */
 
 /*
@@ -103,6 +103,11 @@ union_mount(mp, path, data, ndp, p)
 #endif
 
 	/*
+	 * Disable clustered write, otherwise system becomes unstable.
+	 */
+	mp->mnt_flag |= MNT_NOCLUSTERW;
+
+	/*
 	 * Update is a no-op
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
diff --git a/sys/sys/conf.h b/sys/sys/conf.h
index 0a7e323..194bfd9 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 1.34 1997/02/22 09:44:58 peter Exp $
+ * $Id: conf.h,v 1.35 1997/09/14 02:25:40 peter Exp $
  */
 
 #ifndef _SYS_CONF_H_
@@ -85,6 +85,15 @@ typedef int l_modem_t __P((struct tty *tp, int flag));
 #define	D_DISK	2
 #define	D_TTY	3
 
+#define	D_TYPEMASK	0xffff
+
+/*
+ * Flags for d_flags.
+ */
+#define	D_NOCLUSTERR	0x10000		/* disables cluter read */
+#define	D_NOCLUSTERW	0x20000		/* disables cluster write */
+#define	D_NOCLUSTERRW	(D_NOCLUSTERR | D_NOCLUSTERW)
+
 /*
  * Block device switch table
  */
@@ -95,7 +104,7 @@ struct bdevsw {
 	d_ioctl_t	*d_ioctl;
 	d_dump_t	*d_dump;
 	d_psize_t	*d_psize;
-	int		d_flags;
+	u_int		d_flags;
 	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 */
diff --git a/sys/sys/linedisc.h b/sys/sys/linedisc.h
index 0a7e323..194bfd9 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 1.34 1997/02/22 09:44:58 peter Exp $
+ * $Id: conf.h,v 1.35 1997/09/14 02:25:40 peter Exp $
  */
 
 #ifndef _SYS_CONF_H_
@@ -85,6 +85,15 @@ typedef int l_modem_t __P((struct tty *tp, int flag));
 #define	D_DISK	2
 #define	D_TTY	3
 
+#define	D_TYPEMASK	0xffff
+
+/*
+ * Flags for d_flags.
+ */
+#define	D_NOCLUSTERR	0x10000		/* disables cluter read */
+#define	D_NOCLUSTERW	0x20000		/* disables cluster write */
+#define	D_NOCLUSTERRW	(D_NOCLUSTERR | D_NOCLUSTERW)
+
 /*
  * Block device switch table
  */
@@ -95,7 +104,7 @@ struct bdevsw {
 	d_ioctl_t	*d_ioctl;
 	d_dump_t	*d_dump;
 	d_psize_t	*d_psize;
-	int		d_flags;
+	u_int		d_flags;
 	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 */
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index 73c4af0..b194be0 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)mount.h	8.21 (Berkeley) 5/20/95
- *	$Id: mount.h,v 1.45 1997/08/16 19:16:12 wollman Exp $
+ *	$Id: mount.h,v 1.46 1997/09/16 14:44:24 bde Exp $
  */
 
 #ifndef _SYS_MOUNT_H_
@@ -166,6 +166,8 @@ struct mount {
 #define	MNT_UNION	0x00000020	/* union with underlying filesystem */
 #define	MNT_ASYNC	0x00000040	/* file system written asynchronously */
 #define	MNT_NOATIME	0x10000000	/* Disable update of file access times */
+#define	MNT_NOCLUSTERR	0x40000000	/* Disable cluster read */
+#define	MNT_NOCLUSTERW	0x80000000	/* Disable cluster read */
 
 /*
  * exported mount flags.
@@ -189,9 +191,10 @@ struct mount {
  * Mask of flags that are visible to statfs()
  */
 #define	MNT_VISFLAGMASK	(MNT_RDONLY|MNT_SYNCHRONOUS|MNT_NOEXEC|MNT_NOSUID| \
-			 MNT_NODEV|MNT_UNION|MNT_ASYNC|MNT_EXRDONLY|MNT_EXPORTED| \
-			 MNT_DEFEXPORTED|MNT_EXPORTANON|MNT_EXKERB|MNT_LOCAL| \
-			 MNT_USER|MNT_QUOTA|MNT_ROOTFS|MNT_NOATIME)
+			 MNT_NODEV|MNT_UNION|MNT_ASYNC|MNT_EXRDONLY| \
+			 MNT_EXPORTED|MNT_DEFEXPORTED|MNT_EXPORTANON| \
+			 MNT_EXKERB|MNT_LOCAL|MNT_USER|MNT_QUOTA|MNT_ROOTFS| \
+			 MNT_NOATIME|MNT_NOCLUSTERR|MNT_NOCLUSTERW)
 
 /*
  * External filesystem control flags.
diff --git a/sys/ufs/ffs/ffs_extern.h b/sys/ufs/ffs/ffs_extern.h
index 5c6a519..8fd7d70 100644
--- a/sys/ufs/ffs/ffs_extern.h
+++ b/sys/ufs/ffs/ffs_extern.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ffs_extern.h	8.6 (Berkeley) 3/30/95
- * $Id: ffs_extern.h,v 1.15 1997/02/22 09:47:02 peter Exp $
+ * $Id: ffs_extern.h,v 1.16 1997/08/16 19:16:19 wollman Exp $
  */
 
 #ifndef _UFS_FFS_EXTERN_H
@@ -40,16 +40,14 @@
 /*
  * Sysctl values for the fast filesystem.
  */
-#define FFS_CLUSTERREAD		1	/* cluster reading enabled */
-#define FFS_CLUSTERWRITE	2	/* cluster writing enabled */
 #define FFS_REALLOCBLKS		3	/* block reallocation enabled */
 #define FFS_ASYNCFREE		4	/* asynchronous block freeing enabled */
 #define	FFS_MAXID		5	/* number of valid ffs ids */
 
 #define FFS_NAMES { \
 	{ 0, 0 }, \
-	{ "doclusterread", CTLTYPE_INT }, \
-	{ "doclusterwrite", CTLTYPE_INT }, \
+	{ 0, 0 }, \
+	{ 0, 0 }, \
 	{ "doreallocblks", CTLTYPE_INT }, \
 	{ "doasyncfree", CTLTYPE_INT }, \
 }
diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index a835da5..c0dae9a 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ffs_vfsops.c	8.31 (Berkeley) 5/20/95
- * $Id: ffs_vfsops.c,v 1.54 1997/09/02 20:06:46 bde Exp $
+ * $Id: ffs_vfsops.c,v 1.55 1997/09/07 16:20:59 bde Exp $
  */
 
 #include "opt_quota.h"
@@ -44,6 +44,7 @@
 #include <sys/vnode.h>
 #include <sys/mount.h>
 #include <sys/buf.h>
+#include <sys/conf.h>
 #include <sys/fcntl.h>
 #include <sys/disklabel.h>
 #include <sys/malloc.h>
@@ -155,9 +156,10 @@ ffs_mount( mp, path, data, ndp, p)
 			return (err);
 		}
 
-		/*
-		 * Attempt mount
-		 */
+		if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(rootdev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
 		if( ( err = ffs_mountfs(rootvp, mp, p)) != 0) {
 			/* fs specific cleanup (if any)*/
 			goto error_1;
@@ -181,11 +183,17 @@ ffs_mount( mp, path, data, ndp, p)
 	/*
 	 * If updating, check whether changing from read-only to
 	 * read/write; if there is no device name, that's all we do.
+	 * Disallow clearing MNT_NOCLUSTERR and MNT_NOCLUSTERW flags,
+	 * if block device requests.
 	 */
 	if (mp->mnt_flag & MNT_UPDATE) {
 		ump = VFSTOUFS(mp);
 		fs = ump->um_fs;
 		err = 0;
+		if (bdevsw[major(ump->um_dev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(ump->um_dev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
 		if (fs->fs_ronly == 0 && (mp->mnt_flag & MNT_RDONLY)) {
 			flags = WRITECLOSE;
 			if (mp->mnt_flag & MNT_FORCE)
@@ -275,6 +283,11 @@ ffs_mount( mp, path, data, ndp, p)
 		 ********************
 		 */
 
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERR)
+			mp->mnt_flag |= MNT_NOCLUSTERR;
+		if (bdevsw[major(devvp->v_rdev)]->d_flags & D_NOCLUSTERW)
+			mp->mnt_flag |= MNT_NOCLUSTERW;
+
 		/*
 		 * Since this is a new mount, we want the names for
 		 * the device and the mount point copied in.  If an
diff --git a/sys/ufs/ffs/ffs_vnops.c b/sys/ufs/ffs/ffs_vnops.c
index a546fb8..084e3a9 100644
--- a/sys/ufs/ffs/ffs_vnops.c
+++ b/sys/ufs/ffs/ffs_vnops.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ffs_vnops.c	8.15 (Berkeley) 5/14/95
- * $Id: ffs_vnops.c,v 1.28 1997/09/02 20:06:46 bde Exp $
+ * $Id: ffs_vnops.c,v 1.29 1997/09/14 02:58:05 peter Exp $
  */
 
 #include <sys/param.h>
@@ -239,17 +239,7 @@ VNODEOP_SET(ffs_vnodeop_opv_desc);
 VNODEOP_SET(ffs_specop_opv_desc);
 VNODEOP_SET(ffs_fifoop_opv_desc);
 
-/*
- * Enabling cluster read/write operations.
- */
-static int ffs_doclusterread = 1;
-static int ffs_doclusterwrite = 1;
-
 SYSCTL_NODE(_vfs, MOUNT_UFS, ffs, CTLFLAG_RW, 0, "FFS filesystem");
-SYSCTL_INT(_vfs_ffs, FFS_CLUSTERREAD, doclusterread,
-		   CTLFLAG_RW, &ffs_doclusterread, 0, "");
-SYSCTL_INT(_vfs_ffs, FFS_CLUSTERWRITE, doclusterwrite,
-		   CTLFLAG_RW, &ffs_doclusterwrite, 0, "");
 
 #include <ufs/ufs/ufs_readwrite.c>
 
diff --git a/sys/ufs/ufs/ufs_readwrite.c b/sys/ufs/ufs/ufs_readwrite.c
index c598833..929a289 100644
--- a/sys/ufs/ufs/ufs_readwrite.c
+++ b/sys/ufs/ufs/ufs_readwrite.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ufs_readwrite.c	8.11 (Berkeley) 5/8/95
- * $Id: ufs_readwrite.c,v 1.29 1997/03/22 06:53:44 bde Exp $
+ * $Id: ufs_readwrite.c,v 1.30 1997/08/25 08:18:39 kato Exp $
  */
 
 #ifdef LFS_READWRITE
@@ -123,7 +123,7 @@ READ(ap)
 #else
 		if (lblktosize(fs, nextlbn) >= ip->i_size)
 			error = bread(vp, lbn, size, NOCRED, &bp);
-		else if (ffs_doclusterread)
+		else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0)
 			error = cluster_read(vp, ip->i_size, lbn,
 				size, NOCRED, uio->uio_resid, seqcount, &bp);
 		else if (lbn - 1 == vp->v_lastr) {
@@ -281,7 +281,7 @@ WRITE(ap)
 		if (ioflag & IO_SYNC) {
 			(void)bwrite(bp);
 		} else if (xfersize + blkoffset == fs->fs_bsize) {
-			if (ffs_doclusterwrite) {
+			if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0) {
 				bp->b_flags |= B_CLUSTEROK;
 				cluster_write(bp, ip->i_size);
 			} else {