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spec_vnops.c revision 1.22
      1 /*	$NetBSD: spec_vnops.c,v 1.22 1994/12/14 18:49:38 mycroft Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1989, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  *
     35  *	@(#)spec_vnops.c	8.8 (Berkeley) 11/21/94
     36  */
     37 
     38 #include <sys/param.h>
     39 #include <sys/proc.h>
     40 #include <sys/systm.h>
     41 #include <sys/kernel.h>
     42 #include <sys/conf.h>
     43 #include <sys/buf.h>
     44 #include <sys/mount.h>
     45 #include <sys/namei.h>
     46 #include <sys/vnode.h>
     47 #include <sys/stat.h>
     48 #include <sys/errno.h>
     49 #include <sys/ioctl.h>
     50 #include <sys/file.h>
     51 #include <sys/disklabel.h>
     52 #include <miscfs/specfs/specdev.h>
     53 
     54 /* symbolic sleep message strings for devices */
     55 char	devopn[] = "devopn";
     56 char	devio[] = "devio";
     57 char	devwait[] = "devwait";
     58 char	devin[] = "devin";
     59 char	devout[] = "devout";
     60 char	devioc[] = "devioc";
     61 char	devcls[] = "devcls";
     62 
     63 int (**spec_vnodeop_p)();
     64 struct vnodeopv_entry_desc spec_vnodeop_entries[] = {
     65 	{ &vop_default_desc, vn_default_error },
     66 	{ &vop_lookup_desc, spec_lookup },		/* lookup */
     67 	{ &vop_create_desc, spec_create },		/* create */
     68 	{ &vop_mknod_desc, spec_mknod },		/* mknod */
     69 	{ &vop_open_desc, spec_open },			/* open */
     70 	{ &vop_close_desc, spec_close },		/* close */
     71 	{ &vop_access_desc, spec_access },		/* access */
     72 	{ &vop_getattr_desc, spec_getattr },		/* getattr */
     73 	{ &vop_setattr_desc, spec_setattr },		/* setattr */
     74 	{ &vop_read_desc, spec_read },			/* read */
     75 	{ &vop_write_desc, spec_write },		/* write */
     76 	{ &vop_lease_desc, spec_lease_check },		/* lease */
     77 	{ &vop_ioctl_desc, spec_ioctl },		/* ioctl */
     78 	{ &vop_select_desc, spec_select },		/* select */
     79 	{ &vop_mmap_desc, spec_mmap },			/* mmap */
     80 	{ &vop_fsync_desc, spec_fsync },		/* fsync */
     81 	{ &vop_seek_desc, spec_seek },			/* seek */
     82 	{ &vop_remove_desc, spec_remove },		/* remove */
     83 	{ &vop_link_desc, spec_link },			/* link */
     84 	{ &vop_rename_desc, spec_rename },		/* rename */
     85 	{ &vop_mkdir_desc, spec_mkdir },		/* mkdir */
     86 	{ &vop_rmdir_desc, spec_rmdir },		/* rmdir */
     87 	{ &vop_symlink_desc, spec_symlink },		/* symlink */
     88 	{ &vop_readdir_desc, spec_readdir },		/* readdir */
     89 	{ &vop_readlink_desc, spec_readlink },		/* readlink */
     90 	{ &vop_abortop_desc, spec_abortop },		/* abortop */
     91 	{ &vop_inactive_desc, spec_inactive },		/* inactive */
     92 	{ &vop_reclaim_desc, spec_reclaim },		/* reclaim */
     93 	{ &vop_lock_desc, spec_lock },			/* lock */
     94 	{ &vop_unlock_desc, spec_unlock },		/* unlock */
     95 	{ &vop_bmap_desc, spec_bmap },			/* bmap */
     96 	{ &vop_strategy_desc, spec_strategy },		/* strategy */
     97 	{ &vop_print_desc, spec_print },		/* print */
     98 	{ &vop_islocked_desc, spec_islocked },		/* islocked */
     99 	{ &vop_pathconf_desc, spec_pathconf },		/* pathconf */
    100 	{ &vop_advlock_desc, spec_advlock },		/* advlock */
    101 	{ &vop_blkatoff_desc, spec_blkatoff },		/* blkatoff */
    102 	{ &vop_valloc_desc, spec_valloc },		/* valloc */
    103 	{ &vop_vfree_desc, spec_vfree },		/* vfree */
    104 	{ &vop_truncate_desc, spec_truncate },		/* truncate */
    105 	{ &vop_update_desc, spec_update },		/* update */
    106 	{ &vop_bwrite_desc, spec_bwrite },		/* bwrite */
    107 	{ (struct vnodeop_desc*)NULL, (int(*)())NULL }
    108 };
    109 struct vnodeopv_desc spec_vnodeop_opv_desc =
    110 	{ &spec_vnodeop_p, spec_vnodeop_entries };
    111 
    112 /*
    113  * Trivial lookup routine that always fails.
    114  */
    115 int
    116 spec_lookup(ap)
    117 	struct vop_lookup_args /* {
    118 		struct vnode *a_dvp;
    119 		struct vnode **a_vpp;
    120 		struct componentname *a_cnp;
    121 	} */ *ap;
    122 {
    123 
    124 	*ap->a_vpp = NULL;
    125 	return (ENOTDIR);
    126 }
    127 
    128 /*
    129  * Open a special file.
    130  */
    131 /* ARGSUSED */
    132 spec_open(ap)
    133 	struct vop_open_args /* {
    134 		struct vnode *a_vp;
    135 		int  a_mode;
    136 		struct ucred *a_cred;
    137 		struct proc *a_p;
    138 	} */ *ap;
    139 {
    140 	struct vnode *bvp, *vp = ap->a_vp;
    141 	dev_t bdev, dev = (dev_t)vp->v_rdev;
    142 	register int maj = major(dev);
    143 	int error;
    144 
    145 	/*
    146 	 * Don't allow open if fs is mounted -nodev.
    147 	 */
    148 	if (vp->v_mount && (vp->v_mount->mnt_flag & MNT_NODEV))
    149 		return (ENXIO);
    150 
    151 	switch (vp->v_type) {
    152 
    153 	case VCHR:
    154 		if ((u_int)maj >= nchrdev)
    155 			return (ENXIO);
    156 		if (ap->a_cred != FSCRED && (ap->a_mode & FWRITE)) {
    157 			/*
    158 			 * When running in very secure mode, do not allow
    159 			 * opens for writing of any disk character devices.
    160 			 */
    161 			if (securelevel >= 2 && isdisk(dev, VCHR))
    162 				return (EPERM);
    163 			/*
    164 			 * When running in secure mode, do not allow opens
    165 			 * for writing of /dev/mem, /dev/kmem, or character
    166 			 * devices whose corresponding block devices are
    167 			 * currently mounted.
    168 			 */
    169 			if (securelevel >= 1) {
    170 				if ((bdev = chrtoblk(dev)) != NODEV &&
    171 				    vfinddev(bdev, VBLK, &bvp) &&
    172 				    bvp->v_usecount > 0 &&
    173 				    (error = vfs_mountedon(bvp)))
    174 					return (error);
    175 				if (iskmemdev(dev))
    176 					return (EPERM);
    177 			}
    178 		}
    179 		VOP_UNLOCK(vp);
    180 		error = (*cdevsw[maj].d_open)(dev, ap->a_mode, S_IFCHR, ap->a_p);
    181 		VOP_LOCK(vp);
    182 		return (error);
    183 
    184 	case VBLK:
    185 		if ((u_int)maj >= nblkdev)
    186 			return (ENXIO);
    187 		/*
    188 		 * When running in very secure mode, do not allow
    189 		 * opens for writing of any disk block devices.
    190 		 */
    191 		if (securelevel >= 2 && ap->a_cred != FSCRED &&
    192 		    (ap->a_mode & FWRITE) && isdisk(dev, VBLK))
    193 			return (EPERM);
    194 		/*
    195 		 * Do not allow opens of block devices that are
    196 		 * currently mounted.
    197 		 */
    198 		if (error = vfs_mountedon(vp))
    199 			return (error);
    200 		return ((*bdevsw[maj].d_open)(dev, ap->a_mode, S_IFBLK, ap->a_p));
    201 	}
    202 	return (0);
    203 }
    204 
    205 /*
    206  * Vnode op for read
    207  */
    208 /* ARGSUSED */
    209 spec_read(ap)
    210 	struct vop_read_args /* {
    211 		struct vnode *a_vp;
    212 		struct uio *a_uio;
    213 		int  a_ioflag;
    214 		struct ucred *a_cred;
    215 	} */ *ap;
    216 {
    217 	register struct vnode *vp = ap->a_vp;
    218 	register struct uio *uio = ap->a_uio;
    219  	struct proc *p = uio->uio_procp;
    220 	struct buf *bp;
    221 	daddr_t bn, nextbn;
    222 	long bsize, bscale, ssize;
    223 	struct partinfo dpart;
    224 	int n, on, majordev, (*ioctl)();
    225 	int error = 0;
    226 	dev_t dev;
    227 
    228 #ifdef DIAGNOSTIC
    229 	if (uio->uio_rw != UIO_READ)
    230 		panic("spec_read mode");
    231 	if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != curproc)
    232 		panic("spec_read proc");
    233 #endif
    234 	if (uio->uio_resid == 0)
    235 		return (0);
    236 
    237 	switch (vp->v_type) {
    238 
    239 	case VCHR:
    240 		VOP_UNLOCK(vp);
    241 		error = (*cdevsw[major(vp->v_rdev)].d_read)
    242 			(vp->v_rdev, uio, ap->a_ioflag);
    243 		VOP_LOCK(vp);
    244 		return (error);
    245 
    246 	case VBLK:
    247 		if (uio->uio_offset < 0)
    248 			return (EINVAL);
    249 		bsize = BLKDEV_IOSIZE;
    250 		ssize = DEV_BSIZE;
    251 		dev = vp->v_rdev;
    252 		if ((majordev = major(dev)) < nblkdev &&
    253 		    (ioctl = bdevsw[majordev].d_ioctl) != NULL &&
    254 		    (*ioctl)(dev, DIOCGPART, (caddr_t)&dpart, FREAD, p) == 0) {
    255 			if (dpart.part->p_fstype == FS_BSDFFS &&
    256 			    dpart.part->p_frag != 0 && dpart.part->p_fsize != 0)
    257 				bsize = dpart.part->p_frag *
    258 				    dpart.part->p_fsize;
    259 			if (dpart.disklab->d_secsize != 0)
    260 				ssize = dpart.disklab->d_secsize;
    261 		}
    262 		bscale = bsize / ssize;
    263 		do {
    264 			bn = (uio->uio_offset / ssize) &~ (bscale - 1);
    265 			on = uio->uio_offset % bsize;
    266 			n = min((unsigned)(bsize - on), uio->uio_resid);
    267 			if (vp->v_lastr + bscale == bn) {
    268 				nextbn = bn + bscale;
    269 				error = breadn(vp, bn, (int)bsize, &nextbn,
    270 					(int *)&bsize, 1, NOCRED, &bp);
    271 			} else
    272 				error = bread(vp, bn, (int)bsize, NOCRED, &bp);
    273 			vp->v_lastr = bn;
    274 			n = min(n, bsize - bp->b_resid);
    275 			if (error) {
    276 				brelse(bp);
    277 				return (error);
    278 			}
    279 			error = uiomove((char *)bp->b_data + on, n, uio);
    280 			if (n + on == bsize)
    281 				bp->b_flags |= B_AGE;
    282 			brelse(bp);
    283 		} while (error == 0 && uio->uio_resid > 0 && n != 0);
    284 		return (error);
    285 
    286 	default:
    287 		panic("spec_read type");
    288 	}
    289 	/* NOTREACHED */
    290 }
    291 
    292 /*
    293  * Vnode op for write
    294  */
    295 /* ARGSUSED */
    296 spec_write(ap)
    297 	struct vop_write_args /* {
    298 		struct vnode *a_vp;
    299 		struct uio *a_uio;
    300 		int  a_ioflag;
    301 		struct ucred *a_cred;
    302 	} */ *ap;
    303 {
    304 	register struct vnode *vp = ap->a_vp;
    305 	register struct uio *uio = ap->a_uio;
    306 	struct proc *p = uio->uio_procp;
    307 	struct buf *bp;
    308 	daddr_t bn;
    309 	int bsize, blkmask, ssize;
    310 	struct partinfo dpart;
    311 	register int n, on;
    312 	int error = 0;
    313 
    314 #ifdef DIAGNOSTIC
    315 	if (uio->uio_rw != UIO_WRITE)
    316 		panic("spec_write mode");
    317 	if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != curproc)
    318 		panic("spec_write proc");
    319 #endif
    320 
    321 	switch (vp->v_type) {
    322 
    323 	case VCHR:
    324 		VOP_UNLOCK(vp);
    325 		error = (*cdevsw[major(vp->v_rdev)].d_write)
    326 			(vp->v_rdev, uio, ap->a_ioflag);
    327 		VOP_LOCK(vp);
    328 		return (error);
    329 
    330 	case VBLK:
    331 		if (uio->uio_resid == 0)
    332 			return (0);
    333 		if (uio->uio_offset < 0)
    334 			return (EINVAL);
    335 		bsize = BLKDEV_IOSIZE;
    336 		ssize = DEV_BSIZE;
    337 		if ((*bdevsw[major(vp->v_rdev)].d_ioctl)(vp->v_rdev, DIOCGPART,
    338 		    (caddr_t)&dpart, FREAD, p) == 0) {
    339 			if (dpart.part->p_fstype == FS_BSDFFS &&
    340 			    dpart.part->p_frag != 0 && dpart.part->p_fsize != 0)
    341 				bsize = dpart.part->p_frag *
    342 				    dpart.part->p_fsize;
    343 			if (dpart.disklab->d_secsize != 0)
    344 				ssize = dpart.disklab->d_secsize;
    345 		}
    346 		blkmask = (bsize / ssize) - 1;
    347 		do {
    348 			bn = (uio->uio_offset / ssize) &~ blkmask;
    349 			on = uio->uio_offset % bsize;
    350 			n = min((unsigned)(bsize - on), uio->uio_resid);
    351 			if (n == bsize)
    352 				bp = getblk(vp, bn, bsize, 0, 0);
    353 			else
    354 				error = bread(vp, bn, bsize, NOCRED, &bp);
    355 			n = min(n, bsize - bp->b_resid);
    356 			if (error) {
    357 				brelse(bp);
    358 				return (error);
    359 			}
    360 			error = uiomove((char *)bp->b_data + on, n, uio);
    361 			if (n + on == bsize) {
    362 				bp->b_flags |= B_AGE;
    363 				bawrite(bp);
    364 			} else
    365 				bdwrite(bp);
    366 		} while (error == 0 && uio->uio_resid > 0 && n != 0);
    367 		return (error);
    368 
    369 	default:
    370 		panic("spec_write type");
    371 	}
    372 	/* NOTREACHED */
    373 }
    374 
    375 /*
    376  * Device ioctl operation.
    377  */
    378 /* ARGSUSED */
    379 spec_ioctl(ap)
    380 	struct vop_ioctl_args /* {
    381 		struct vnode *a_vp;
    382 		u_long a_command;
    383 		caddr_t  a_data;
    384 		int  a_fflag;
    385 		struct ucred *a_cred;
    386 		struct proc *a_p;
    387 	} */ *ap;
    388 {
    389 	dev_t dev = ap->a_vp->v_rdev;
    390 
    391 	switch (ap->a_vp->v_type) {
    392 
    393 	case VCHR:
    394 		return ((*cdevsw[major(dev)].d_ioctl)(dev, ap->a_command, ap->a_data,
    395 		    ap->a_fflag, ap->a_p));
    396 
    397 	case VBLK:
    398 		if (ap->a_command == 0 && (long)ap->a_data == B_TAPE)
    399 			if (bdevsw[major(dev)].d_flags & B_TAPE)
    400 				return (0);
    401 			else
    402 				return (1);
    403 		return ((*bdevsw[major(dev)].d_ioctl)(dev, ap->a_command, ap->a_data,
    404 		   ap->a_fflag, ap->a_p));
    405 
    406 	default:
    407 		panic("spec_ioctl");
    408 		/* NOTREACHED */
    409 	}
    410 }
    411 
    412 /* ARGSUSED */
    413 spec_select(ap)
    414 	struct vop_select_args /* {
    415 		struct vnode *a_vp;
    416 		int  a_which;
    417 		int  a_fflags;
    418 		struct ucred *a_cred;
    419 		struct proc *a_p;
    420 	} */ *ap;
    421 {
    422 	register dev_t dev;
    423 
    424 	switch (ap->a_vp->v_type) {
    425 
    426 	default:
    427 		return (1);		/* XXX */
    428 
    429 	case VCHR:
    430 		dev = ap->a_vp->v_rdev;
    431 		return (*cdevsw[major(dev)].d_select)(dev, ap->a_which, ap->a_p);
    432 	}
    433 }
    434 /*
    435  * Synch buffers associated with a block device
    436  */
    437 /* ARGSUSED */
    438 int
    439 spec_fsync(ap)
    440 	struct vop_fsync_args /* {
    441 		struct vnode *a_vp;
    442 		struct ucred *a_cred;
    443 		int  a_waitfor;
    444 		struct proc *a_p;
    445 	} */ *ap;
    446 {
    447 	register struct vnode *vp = ap->a_vp;
    448 	register struct buf *bp;
    449 	struct buf *nbp;
    450 	int s;
    451 
    452 	if (vp->v_type == VCHR)
    453 		return (0);
    454 	/*
    455 	 * Flush all dirty buffers associated with a block device.
    456 	 */
    457 loop:
    458 	s = splbio();
    459 	for (bp = vp->v_dirtyblkhd.lh_first; bp; bp = nbp) {
    460 		nbp = bp->b_vnbufs.le_next;
    461 		if ((bp->b_flags & B_BUSY))
    462 			continue;
    463 		if ((bp->b_flags & B_DELWRI) == 0)
    464 			panic("spec_fsync: not dirty");
    465 		bremfree(bp);
    466 		bp->b_flags |= B_BUSY;
    467 		splx(s);
    468 		bawrite(bp);
    469 		goto loop;
    470 	}
    471 	if (ap->a_waitfor == MNT_WAIT) {
    472 		while (vp->v_numoutput) {
    473 			vp->v_flag |= VBWAIT;
    474 			sleep((caddr_t)&vp->v_numoutput, PRIBIO + 1);
    475 		}
    476 #ifdef DIAGNOSTIC
    477 		if (vp->v_dirtyblkhd.lh_first) {
    478 			vprint("spec_fsync: dirty", vp);
    479 			goto loop;
    480 		}
    481 #endif
    482 	}
    483 	splx(s);
    484 	return (0);
    485 }
    486 
    487 /*
    488  * Just call the device strategy routine
    489  */
    490 spec_strategy(ap)
    491 	struct vop_strategy_args /* {
    492 		struct buf *a_bp;
    493 	} */ *ap;
    494 {
    495 
    496 	(*bdevsw[major(ap->a_bp->b_dev)].d_strategy)(ap->a_bp);
    497 	return (0);
    498 }
    499 
    500 /*
    501  * This is a noop, simply returning what one has been given.
    502  */
    503 spec_bmap(ap)
    504 	struct vop_bmap_args /* {
    505 		struct vnode *a_vp;
    506 		daddr_t  a_bn;
    507 		struct vnode **a_vpp;
    508 		daddr_t *a_bnp;
    509 	} */ *ap;
    510 {
    511 
    512 	if (ap->a_vpp != NULL)
    513 		*ap->a_vpp = ap->a_vp;
    514 	if (ap->a_bnp != NULL)
    515 		*ap->a_bnp = ap->a_bn;
    516 	return (0);
    517 }
    518 
    519 /*
    520  * At the moment we do not do any locking.
    521  */
    522 /* ARGSUSED */
    523 spec_lock(ap)
    524 	struct vop_lock_args /* {
    525 		struct vnode *a_vp;
    526 	} */ *ap;
    527 {
    528 
    529 	return (0);
    530 }
    531 
    532 /* ARGSUSED */
    533 spec_unlock(ap)
    534 	struct vop_unlock_args /* {
    535 		struct vnode *a_vp;
    536 	} */ *ap;
    537 {
    538 
    539 	return (0);
    540 }
    541 
    542 /*
    543  * Device close routine
    544  */
    545 /* ARGSUSED */
    546 spec_close(ap)
    547 	struct vop_close_args /* {
    548 		struct vnode *a_vp;
    549 		int  a_fflag;
    550 		struct ucred *a_cred;
    551 		struct proc *a_p;
    552 	} */ *ap;
    553 {
    554 	register struct vnode *vp = ap->a_vp;
    555 	dev_t dev = vp->v_rdev;
    556 	int (*devclose) __P((dev_t, int, int, struct proc *));
    557 	int mode, error;
    558 
    559 	switch (vp->v_type) {
    560 
    561 	case VCHR:
    562 		/*
    563 		 * Hack: a tty device that is a controlling terminal
    564 		 * has a reference from the session structure.
    565 		 * We cannot easily tell that a character device is
    566 		 * a controlling terminal, unless it is the closing
    567 		 * process' controlling terminal.  In that case,
    568 		 * if the reference count is 2 (this last descriptor
    569 		 * plus the session), release the reference from the session.
    570 		 */
    571 		if (vcount(vp) == 2 && ap->a_p &&
    572 		    vp == ap->a_p->p_session->s_ttyvp) {
    573 			vrele(vp);
    574 			ap->a_p->p_session->s_ttyvp = NULL;
    575 		}
    576 		/*
    577 		 * If the vnode is locked, then we are in the midst
    578 		 * of forcably closing the device, otherwise we only
    579 		 * close on last reference.
    580 		 */
    581 		if (vcount(vp) > 1 && (vp->v_flag & VXLOCK) == 0)
    582 			return (0);
    583 		devclose = cdevsw[major(dev)].d_close;
    584 		mode = S_IFCHR;
    585 		break;
    586 
    587 	case VBLK:
    588 		/*
    589 		 * On last close of a block device (that isn't mounted)
    590 		 * we must invalidate any in core blocks, so that
    591 		 * we can, for instance, change floppy disks.
    592 		 */
    593 		if (error = vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_p, 0, 0))
    594 			return (error);
    595 		/*
    596 		 * We do not want to really close the device if it
    597 		 * is still in use unless we are trying to close it
    598 		 * forcibly. Since every use (buffer, vnode, swap, cmap)
    599 		 * holds a reference to the vnode, and because we mark
    600 		 * any other vnodes that alias this device, when the
    601 		 * sum of the reference counts on all the aliased
    602 		 * vnodes descends to one, we are on last close.
    603 		 */
    604 		if (vcount(vp) > 1 && (vp->v_flag & VXLOCK) == 0)
    605 			return (0);
    606 		devclose = bdevsw[major(dev)].d_close;
    607 		mode = S_IFBLK;
    608 		break;
    609 
    610 	default:
    611 		panic("spec_close: not special");
    612 	}
    613 
    614 	return ((*devclose)(dev, ap->a_fflag, mode, ap->a_p));
    615 }
    616 
    617 /*
    618  * Print out the contents of a special device vnode.
    619  */
    620 spec_print(ap)
    621 	struct vop_print_args /* {
    622 		struct vnode *a_vp;
    623 	} */ *ap;
    624 {
    625 
    626 	printf("tag VT_NON, dev %d, %d\n", major(ap->a_vp->v_rdev),
    627 		minor(ap->a_vp->v_rdev));
    628 }
    629 
    630 /*
    631  * Return POSIX pathconf information applicable to special devices.
    632  */
    633 spec_pathconf(ap)
    634 	struct vop_pathconf_args /* {
    635 		struct vnode *a_vp;
    636 		int a_name;
    637 		register_t *a_retval;
    638 	} */ *ap;
    639 {
    640 
    641 	switch (ap->a_name) {
    642 	case _PC_LINK_MAX:
    643 		*ap->a_retval = LINK_MAX;
    644 		return (0);
    645 	case _PC_MAX_CANON:
    646 		*ap->a_retval = MAX_CANON;
    647 		return (0);
    648 	case _PC_MAX_INPUT:
    649 		*ap->a_retval = MAX_INPUT;
    650 		return (0);
    651 	case _PC_PIPE_BUF:
    652 		*ap->a_retval = PIPE_BUF;
    653 		return (0);
    654 	case _PC_CHOWN_RESTRICTED:
    655 		*ap->a_retval = 1;
    656 		return (0);
    657 	case _PC_VDISABLE:
    658 		*ap->a_retval = _POSIX_VDISABLE;
    659 		return (0);
    660 	default:
    661 		return (EINVAL);
    662 	}
    663 	/* NOTREACHED */
    664 }
    665 
    666 /*
    667  * Special device advisory byte-level locks.
    668  */
    669 /* ARGSUSED */
    670 spec_advlock(ap)
    671 	struct vop_advlock_args /* {
    672 		struct vnode *a_vp;
    673 		caddr_t  a_id;
    674 		int  a_op;
    675 		struct flock *a_fl;
    676 		int  a_flags;
    677 	} */ *ap;
    678 {
    679 
    680 	return (EOPNOTSUPP);
    681 }
    682 
    683 /*
    684  * Special device failed operation
    685  */
    686 spec_ebadf()
    687 {
    688 
    689 	return (EBADF);
    690 }
    691 
    692 /*
    693  * Special device bad operation
    694  */
    695 spec_badop()
    696 {
    697 
    698 	panic("spec_badop called");
    699 	/* NOTREACHED */
    700 }
    701