xnu-201.tar.gz

[apple/xnu.git] / bsd / miscfs / specfs / spec_vnops.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1989, 1993, 1995
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)spec_vnops.c        8.14 (Berkeley) 5/21/95
 */

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/buf.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/stat.h>
#include <sys/errno.h>
#include <sys/ioctl.h>
#include <sys/file.h>
#include <sys/malloc.h>
#include <dev/disk.h>
#include <miscfs/specfs/specdev.h>
#include <vfs/vfs_support.h>


struct vnode *speclisth[SPECHSZ];

/* symbolic sleep message strings for devices */
char    devopn[] = "devopn";
char    devio[] = "devio";
char    devwait[] = "devwait";
char    devin[] = "devin";
char    devout[] = "devout";
char    devioc[] = "devioc";
char    devcls[] = "devcls";

#define VOPFUNC int (*)(void *)

int (**spec_vnodeop_p)(void *);
struct vnodeopv_entry_desc spec_vnodeop_entries[] = {
        { &vop_default_desc, (VOPFUNC)vn_default_error },
        { &vop_lookup_desc, (VOPFUNC)spec_lookup },             /* lookup */
        { &vop_create_desc, (VOPFUNC)err_create },              /* create */
        { &vop_mknod_desc, (VOPFUNC)err_mknod },                /* mknod */
        { &vop_open_desc, (VOPFUNC)spec_open },                 /* open */
        { &vop_close_desc, (VOPFUNC)spec_close },               /* close */
        { &vop_access_desc, (VOPFUNC)spec_access },             /* access */
        { &vop_getattr_desc, (VOPFUNC)spec_getattr },           /* getattr */
        { &vop_setattr_desc, (VOPFUNC)spec_setattr },           /* setattr */
        { &vop_read_desc, (VOPFUNC)spec_read },                 /* read */
        { &vop_write_desc, (VOPFUNC)spec_write },               /* write */
        { &vop_lease_desc, (VOPFUNC)nop_lease },                /* lease */
        { &vop_ioctl_desc, (VOPFUNC)spec_ioctl },               /* ioctl */
        { &vop_select_desc, (VOPFUNC)spec_select },             /* select */
        { &vop_revoke_desc, (VOPFUNC)nop_revoke },              /* revoke */
        { &vop_mmap_desc, (VOPFUNC)err_mmap },                  /* mmap */
        { &vop_fsync_desc, (VOPFUNC)spec_fsync },               /* fsync */
        { &vop_seek_desc, (VOPFUNC)err_seek },                  /* seek */
        { &vop_remove_desc, (VOPFUNC)err_remove },              /* remove */
        { &vop_link_desc, (VOPFUNC)err_link },                  /* link */
        { &vop_rename_desc, (VOPFUNC)err_rename },              /* rename */
        { &vop_mkdir_desc, (VOPFUNC)err_mkdir },                /* mkdir */
        { &vop_rmdir_desc, (VOPFUNC)err_rmdir },                /* rmdir */
        { &vop_symlink_desc, (VOPFUNC)err_symlink },            /* symlink */
        { &vop_readdir_desc, (VOPFUNC)err_readdir },            /* readdir */
        { &vop_readlink_desc, (VOPFUNC)err_readlink },          /* readlink */
        { &vop_abortop_desc, (VOPFUNC)err_abortop },            /* abortop */
        { &vop_inactive_desc, (VOPFUNC)nop_inactive },          /* inactive */
        { &vop_reclaim_desc, (VOPFUNC)nop_reclaim },            /* reclaim */
        { &vop_lock_desc, (VOPFUNC)nop_lock },                  /* lock */
        { &vop_unlock_desc, (VOPFUNC)nop_unlock },              /* unlock */
        { &vop_bmap_desc, (VOPFUNC)spec_bmap },                 /* bmap */
        { &vop_strategy_desc, (VOPFUNC)spec_strategy },         /* strategy */
        { &vop_print_desc, (VOPFUNC)spec_print },               /* print */
        { &vop_islocked_desc, (VOPFUNC)nop_islocked },          /* islocked */
        { &vop_pathconf_desc, (VOPFUNC)spec_pathconf },         /* pathconf */
        { &vop_advlock_desc, (VOPFUNC)err_advlock },            /* advlock */
        { &vop_blkatoff_desc, (VOPFUNC)err_blkatoff },          /* blkatoff */
        { &vop_valloc_desc, (VOPFUNC)err_valloc },              /* valloc */
        { &vop_vfree_desc, (VOPFUNC)err_vfree },                /* vfree */
        { &vop_truncate_desc, (VOPFUNC)nop_truncate },          /* truncate */
        { &vop_update_desc, (VOPFUNC)nop_update },              /* update */
        { &vop_bwrite_desc, (VOPFUNC)spec_bwrite },             /* bwrite */
        { &vop_devblocksize_desc, (VOPFUNC)spec_devblocksize }, /* devblocksize */
        { &vop_pagein_desc, (VOPFUNC)err_pagein },              /* Pagein */
        { &vop_pageout_desc, (VOPFUNC)err_pageout },            /* Pageout */
        { &vop_copyfile_desc, (VOPFUNC)err_copyfile },          /* Copyfile */
        { &vop_blktooff_desc, (VOPFUNC)spec_blktooff },         /* blktooff */
        { &vop_offtoblk_desc, (VOPFUNC)spec_offtoblk },         /* offtoblk */
        { &vop_cmap_desc, (VOPFUNC)spec_cmap },         /* cmap */
        { (struct vnodeop_desc*)NULL, (int(*)())NULL }
};
struct vnodeopv_desc spec_vnodeop_opv_desc =
        { &spec_vnodeop_p, spec_vnodeop_entries };

/*
 * Trivial lookup routine that always fails.
 */
int
spec_lookup(ap)
        struct vop_lookup_args /* {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
        } */ *ap;
{

        *ap->a_vpp = NULL;
        return (ENOTDIR);
}

void
set_blocksize(struct vnode *vp, dev_t dev)
{
    int (*size)();
    int rsize;

    if ((major(dev) < nblkdev) && (size = bdevsw[major(dev)].d_psize)) {
        rsize = (*size)(dev);
        if (rsize <= 0)        /* did size fail? */
            vp->v_specsize = DEV_BSIZE;
        else
            vp->v_specsize = rsize;
    }
    else
            vp->v_specsize = DEV_BSIZE;
}

void
set_fsblocksize(struct vnode *vp)
{
        
        if (vp->v_type == VBLK) {
                dev_t dev = (dev_t)vp->v_rdev;
                int maj = major(dev);

                if ((u_int)maj >= nblkdev)
                        return;

                set_blocksize(vp, dev);
        }

}


/*
 * Open a special file.
 */
/* ARGSUSED */
spec_open(ap)
        struct vop_open_args /* {
                struct vnode *a_vp;
                int  a_mode;
                struct ucred *a_cred;
                struct proc *a_p;
        } */ *ap;
{
        struct proc *p = ap->a_p;
        struct vnode *bvp, *vp = ap->a_vp;
        dev_t bdev, dev = (dev_t)vp->v_rdev;
        int maj = major(dev);
        int error;

        /*
         * Don't allow open if fs is mounted -nodev.
         */
        if (vp->v_mount && (vp->v_mount->mnt_flag & MNT_NODEV))
                return (ENXIO);

        switch (vp->v_type) {

        case VCHR:
                if ((u_int)maj >= nchrdev)
                        return (ENXIO);
                if (ap->a_cred != FSCRED && (ap->a_mode & FWRITE)) {
                        /*
                         * When running in very secure mode, do not allow
                         * opens for writing of any disk character devices.
                         */
                        if (securelevel >= 2 && isdisk(dev, VCHR))
                                return (EPERM);
                        /*
                         * When running in secure mode, do not allow opens
                         * for writing of /dev/mem, /dev/kmem, or character
                         * devices whose corresponding block devices are
                         * currently mounted.
                         */
                        if (securelevel >= 1) {
                                if ((bdev = chrtoblk(dev)) != NODEV &&
                                    vfinddev(bdev, VBLK, &bvp) &&
                                    bvp->v_usecount > 0 &&
                                    (error = vfs_mountedon(bvp)))
                                        return (error);
                                if (iskmemdev(dev))
                                        return (EPERM);
                        }
                }
                if (cdevsw[maj].d_type == D_TTY)
                        vp->v_flag |= VISTTY;
                VOP_UNLOCK(vp, 0, p);
                error = (*cdevsw[maj].d_open)(dev, ap->a_mode, S_IFCHR, p);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
                return (error);

        case VBLK:
                if ((u_int)maj >= nblkdev)
                        return (ENXIO);
                /*
                 * When running in very secure mode, do not allow
                 * opens for writing of any disk block devices.
                 */
                if (securelevel >= 2 && ap->a_cred != FSCRED &&
                    (ap->a_mode & FWRITE) && bdevsw[maj].d_type == D_DISK)
                        return (EPERM);
                /*
                 * Do not allow opens of block devices that are
                 * currently mounted.
                 */
                if (error = vfs_mountedon(vp))
                        return (error);
                error = (*bdevsw[maj].d_open)(dev, ap->a_mode, S_IFBLK, p);
                if (!error) {
                    set_blocksize(vp, dev);
                }
                return(error);
        }
        return (0);
}

/*
 * Vnode op for read
 */
/* ARGSUSED */
spec_read(ap)
        struct vop_read_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                struct ucred *a_cred;
        } */ *ap;
{
        register struct vnode *vp = ap->a_vp;
        register struct uio *uio = ap->a_uio;
        struct proc *p = uio->uio_procp;
        struct buf *bp;
        daddr_t bn, nextbn;
        long bsize, bscale;
        int devBlockSize=0;
        int n, on, majordev, (*ioctl)();
        int error = 0;
        dev_t dev;

#if DIAGNOSTIC
        if (uio->uio_rw != UIO_READ)
                panic("spec_read mode");
        if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != current_proc())
                panic("spec_read proc");
#endif
        if (uio->uio_resid == 0)
                return (0);

        switch (vp->v_type) {

        case VCHR:
                VOP_UNLOCK(vp, 0, p);
                error = (*cdevsw[major(vp->v_rdev)].d_read)
                        (vp->v_rdev, uio, ap->a_ioflag);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
                return (error);

        case VBLK:
                if (uio->uio_offset < 0)
                        return (EINVAL);

                dev = vp->v_rdev;

                devBlockSize = vp->v_specsize;

                if (devBlockSize > PAGE_SIZE) 
                        return (EINVAL);

                bscale = PAGE_SIZE / devBlockSize;
                bsize = bscale * devBlockSize;

                do {
                        on = uio->uio_offset % bsize;

                        bn = (uio->uio_offset / devBlockSize) &~ (bscale - 1);
                        
                        if (vp->v_lastr + bscale == bn) {
                                nextbn = bn + bscale;
                                error = breadn(vp, bn, (int)bsize, &nextbn,
                                               (int *)&bsize, 1, NOCRED, &bp);
                        } else
                                error = bread(vp, bn, (int)bsize, NOCRED, &bp);

                        vp->v_lastr = bn;
                        n = bsize - bp->b_resid;
                        if ((on > n) || error) {
                                if (!error)
                                        error = EINVAL;
                                brelse(bp);
                                return (error);
                        }
                        n = min((unsigned)(n  - on), uio->uio_resid);

                        error = uiomove((char *)bp->b_data + on, n, uio);
                        if (n + on == bsize)
                                bp->b_flags |= B_AGE;
                        brelse(bp);
                } while (error == 0 && uio->uio_resid > 0 && n != 0);
                return (error);

        default:
                panic("spec_read type");
        }
        /* NOTREACHED */
}

/*
 * Vnode op for write
 */
/* ARGSUSED */
spec_write(ap)
        struct vop_write_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                struct ucred *a_cred;
        } */ *ap;
{
        register struct vnode *vp = ap->a_vp;
        register struct uio *uio = ap->a_uio;
        struct proc *p = uio->uio_procp;
        struct buf *bp;
        daddr_t bn;
        int bsize, blkmask, bscale;
        register int io_sync;
        register int io_size;
        int devBlockSize=0;
        register int n, on;
        int error = 0;
        dev_t dev;

#if DIAGNOSTIC
        if (uio->uio_rw != UIO_WRITE)
                panic("spec_write mode");
        if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != current_proc())
                panic("spec_write proc");
#endif

        switch (vp->v_type) {

        case VCHR:
                VOP_UNLOCK(vp, 0, p);
                error = (*cdevsw[major(vp->v_rdev)].d_write)
                        (vp->v_rdev, uio, ap->a_ioflag);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
                return (error);

        case VBLK:
                if (uio->uio_resid == 0)
                        return (0);
                if (uio->uio_offset < 0)
                        return (EINVAL);

                io_sync = (ap->a_ioflag & IO_SYNC);
                io_size = uio->uio_resid;

                dev = (vp->v_rdev);

                devBlockSize = vp->v_specsize;
                if (devBlockSize > PAGE_SIZE)
                        return(EINVAL);

                bscale = PAGE_SIZE / devBlockSize;
                blkmask = bscale - 1;
                bsize = bscale * devBlockSize;
                

                do {
                        bn = (uio->uio_offset / devBlockSize) &~ blkmask;
                        on = uio->uio_offset % bsize;

                        n = min((unsigned)(bsize - on), uio->uio_resid);

                        if (n == bsize)
                                bp = getblk(vp, bn, bsize, 0, 0, BLK_WRITE);
                        else
                                error = bread(vp, bn, bsize, NOCRED, &bp);

                        if (error) {
                                brelse(bp);
                                return (error);
                        }
                        n = min(n, bsize - bp->b_resid);

                        error = uiomove((char *)bp->b_data + on, n, uio);

                        bp->b_flags |= B_AGE;

                        if (io_sync) 
                                bwrite(bp);
                        else {
                                if ((n + on) == bsize)
                                        bawrite(bp);
                                else
                                        bdwrite(bp);
                        }
                } while (error == 0 && uio->uio_resid > 0 && n != 0);
                return (error);

        default:
                panic("spec_write type");
        }
        /* NOTREACHED */
}

/*
 * Device ioctl operation.
 */
/* ARGSUSED */
spec_ioctl(ap)
        struct vop_ioctl_args /* {
                struct vnode *a_vp;
                int  a_command;
                caddr_t  a_data;
                int  a_fflag;
                struct ucred *a_cred;
                struct proc *a_p;
        } */ *ap;
{
        dev_t dev = ap->a_vp->v_rdev;

        switch (ap->a_vp->v_type) {

        case VCHR:
                return ((*cdevsw[major(dev)].d_ioctl)(dev, ap->a_command, ap->a_data,
                    ap->a_fflag, ap->a_p));

        case VBLK:
                if (ap->a_command == 0 && (int)ap->a_data == B_TAPE)
                        if (bdevsw[major(dev)].d_type == D_TAPE)
                                return (0);
                        else
                                return (1);
                return ((*bdevsw[major(dev)].d_ioctl)(dev, ap->a_command, ap->a_data,
                   ap->a_fflag, ap->a_p));

        default:
                panic("spec_ioctl");
                /* NOTREACHED */
        }
}

/* ARGSUSED */
spec_select(ap)
        struct vop_select_args /* {
                struct vnode *a_vp;
                int  a_which;
                int  a_fflags;
                struct ucred *a_cred;
                void * a_wql;
                struct proc *a_p;
        } */ *ap;
{
        register dev_t dev;

        switch (ap->a_vp->v_type) {

        default:
                return (1);             /* XXX */

        case VCHR:
                dev = ap->a_vp->v_rdev;
                return (*cdevsw[major(dev)].d_select)(dev, ap->a_which, ap->a_wql, ap->a_p);
        }
}
/*
 * Synch buffers associated with a block device
 */
/* ARGSUSED */
int
spec_fsync(ap)
        struct vop_fsync_args /* {
                struct vnode *a_vp;
                struct ucred *a_cred;
                int  a_waitfor;
                struct proc *a_p;
        } */ *ap;
{
        register struct vnode *vp = ap->a_vp;
        register struct buf *bp;
        struct buf *nbp;
        int s;

        if (vp->v_type == VCHR)
                return (0);
        /*
         * Flush all dirty buffers associated with a block device.
         */
loop:
        s = splbio();
        for (bp = vp->v_dirtyblkhd.lh_first; bp; bp = nbp) {
                nbp = bp->b_vnbufs.le_next;
                if ((bp->b_flags & B_BUSY))
                        continue;
                if ((bp->b_flags & B_DELWRI) == 0)
                        panic("spec_fsync: not dirty");
                bremfree(bp);
                bp->b_flags |= B_BUSY;
                splx(s);
                bawrite(bp);
                goto loop;
        }
        if (ap->a_waitfor == MNT_WAIT) {
                while (vp->v_numoutput) {
                        vp->v_flag |= VBWAIT;
                        tsleep((caddr_t)&vp->v_numoutput, PRIBIO + 1, "spec_fsync", 0);
                }
#if DIAGNOSTIC
                if (vp->v_dirtyblkhd.lh_first) {
                        vprint("spec_fsync: dirty", vp);
                        splx(s);
                        goto loop;
                }
#endif
        }
        splx(s);
        return (0);
}

/*
 * Just call the device strategy routine
 */
spec_strategy(ap)
        struct vop_strategy_args /* {
                struct buf *a_bp;
        } */ *ap;
{
        (*bdevsw[major(ap->a_bp->b_dev)].d_strategy)(ap->a_bp);
        return (0);
}

/*
 * This is a noop, simply returning what one has been given.
 */
spec_bmap(ap)
        struct vop_bmap_args /* {
                struct vnode *a_vp;
                daddr_t  a_bn;
                struct vnode **a_vpp;
                daddr_t *a_bnp;
                int *a_runp;
        } */ *ap;
{

        if (ap->a_vpp != NULL)
                *ap->a_vpp = ap->a_vp;
        if (ap->a_bnp != NULL)
                *ap->a_bnp = ap->a_bn * (PAGE_SIZE / ap->a_vp->v_specsize);
        if (ap->a_runp != NULL)
                *ap->a_runp = (MAXPHYSIO / PAGE_SIZE) - 1;
        return (0);
}

/*
 * This is a noop, simply returning what one has been given.
 */
spec_cmap(ap)
        struct vop_cmap_args /* {
                struct vnode *a_vp;
                off_t a_offset;    
                size_t a_size;
                daddr_t *a_bpn;
                size_t *a_run;
                void *a_poff;
        } */ *ap;
{
        return (EOPNOTSUPP);
}


/*
 * Device close routine
 */
/* ARGSUSED */
spec_close(ap)
        struct vop_close_args /* {
                struct vnode *a_vp;
                int  a_fflag;
                struct ucred *a_cred;
                struct proc *a_p;
        } */ *ap;
{
        register struct vnode *vp = ap->a_vp;
        dev_t dev = vp->v_rdev;
        int (*devclose) __P((dev_t, int, int, struct proc *));
        int mode, error;

        switch (vp->v_type) {

        case VCHR:
                /*
                 * Hack: a tty device that is a controlling terminal
                 * has a reference from the session structure.
                 * We cannot easily tell that a character device is
                 * a controlling terminal, unless it is the closing
                 * process' controlling terminal.  In that case,
                 * if the reference count is 2 (this last descriptor
                 * plus the session), release the reference from the session.
                 */
                if (vcount(vp) == 2 && ap->a_p &&
                    vp == ap->a_p->p_session->s_ttyvp) {
                        vrele(vp);
                        ap->a_p->p_session->s_ttyvp = NULL;
                }
                /*
                 * If the vnode is locked, then we are in the midst
                 * of forcably closing the device, otherwise we only
                 * close on last reference.
                 */
                if (vcount(vp) > 1 && (vp->v_flag & VXLOCK) == 0)
                        return (0);
                devclose = cdevsw[major(dev)].d_close;
                mode = S_IFCHR;
                break;

        case VBLK:
#ifdef DEVFS_IMPLEMENTS_LOCKING
                /*
                 * On last close of a block device (that isn't mounted)
                 * we must invalidate any in core blocks, so that
                 * we can, for instance, change floppy disks.
                 */
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, ap->a_p);
                error = vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_p, 0, 0);
                VOP_UNLOCK(vp, 0, ap->a_p);
                if (error)
                        return (error);
                /*
                 * We do not want to really close the device if it
                 * is still in use unless we are trying to close it
                 * forcibly. Since every use (buffer, vnode, swap, cmap)
                 * holds a reference to the vnode, and because we mark
                 * any other vnodes that alias this device, when the
                 * sum of the reference counts on all the aliased
                 * vnodes descends to one, we are on last close.
                 */
                if (vcount(vp) > 1 && (vp->v_flag & VXLOCK) == 0)
                        return (0);
#else /* DEVFS_IMPLEMENTS_LOCKING */
                /*
                 * We do not want to really close the device if it
                 * is still in use unless we are trying to close it
                 * forcibly. Since every use (buffer, vnode, swap, cmap)
                 * holds a reference to the vnode, and because we mark
                 * any other vnodes that alias this device, when the
                 * sum of the reference counts on all the aliased
                 * vnodes descends to one, we are on last close.
                 */
                if (vcount(vp) > 1 && (vp->v_flag & VXLOCK) == 0)
                        return (0);

                /*
                 * On last close of a block device (that isn't mounted)
                 * we must invalidate any in core blocks, so that
                 * we can, for instance, change floppy disks.
                 */
                error = vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_p, 0, 0);
                if (error)
                        return (error);
#endif /* DEVFS_IMPLEMENTS_LOCKING */
                devclose = bdevsw[major(dev)].d_close;
                mode = S_IFBLK;
                break;

        default:
                panic("spec_close: not special");
        }

        return ((*devclose)(dev, ap->a_fflag, mode, ap->a_p));
}

/*
 * Print out the contents of a special device vnode.
 */
spec_print(ap)
        struct vop_print_args /* {
                struct vnode *a_vp;
        } */ *ap;
{

        printf("tag VT_NON, dev %d, %d\n", major(ap->a_vp->v_rdev),
                minor(ap->a_vp->v_rdev));
}

/*
 * Return POSIX pathconf information applicable to special devices.
 */
spec_pathconf(ap)
        struct vop_pathconf_args /* {
                struct vnode *a_vp;
                int a_name;
                int *a_retval;
        } */ *ap;
{

        switch (ap->a_name) {
        case _PC_LINK_MAX:
                *ap->a_retval = LINK_MAX;
                return (0);
        case _PC_MAX_CANON:
                *ap->a_retval = MAX_CANON;
                return (0);
        case _PC_MAX_INPUT:
                *ap->a_retval = MAX_INPUT;
                return (0);
        case _PC_PIPE_BUF:
                *ap->a_retval = PIPE_BUF;
                return (0);
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = 1;
                return (0);
        case _PC_VDISABLE:
                *ap->a_retval = _POSIX_VDISABLE;
                return (0);
        default:
                return (EINVAL);
        }
        /* NOTREACHED */
}

int
spec_devblocksize(ap)
        struct vop_devblocksize_args /* {
                struct vnode *a_vp;
                int *a_retval;
        } */ *ap;
{
        *ap->a_retval = (ap->a_vp->v_specsize);
        return (0);
}

/*
 * Special device failed operation
 */
spec_ebadf()
{

        return (EBADF);
}

/*
 * Special device bad operation
 */
spec_badop()
{

        panic("spec_badop called");
        /* NOTREACHED */
}

/* Blktooff derives file offset from logical block number */
int
spec_blktooff(ap)
        struct vop_blktooff_args /* {
                struct vnode *a_vp;
                daddr_t a_lblkno;
                off_t *a_offset;    
        } */ *ap;
{
        register struct vnode *vp = ap->a_vp;

        switch (vp->v_type) {
        case VCHR:
                *ap->a_offset = (off_t)-1; /* failure */
                return (EOPNOTSUPP);

        case VBLK:
                printf("spec_blktooff: not implemented for VBLK\n");
                *ap->a_offset = (off_t)-1; /* failure */
                return (EOPNOTSUPP);

        default:
                panic("spec_blktooff type");
        }
        /* NOTREACHED */
}

/* Offtoblk derives logical block number from file offset */
int
spec_offtoblk(ap)
        struct vop_offtoblk_args /* {
                struct vnode *a_vp;
                off_t a_offset;    
                daddr_t *a_lblkno;
        } */ *ap;
{
        register struct vnode *vp = ap->a_vp;

        switch (vp->v_type) {
        case VCHR:
                *ap->a_lblkno = (daddr_t)-1; /* failure */
                return (EOPNOTSUPP);

        case VBLK:
                printf("spec_offtoblk: not implemented for VBLK\n");
                *ap->a_lblkno = (daddr_t)-1; /* failure */
                return (EOPNOTSUPP);

        default:
                panic("spec_offtoblk type");
        }
        /* NOTREACHED */
}