xref: /netbsd-src/sys/miscfs/specfs/spec_vnops.c (revision 27578b9aac214cc7796ead81dcc5427e79d5f2a0)
1 /*	$NetBSD: spec_vnops.c,v 1.58 2001/09/21 08:02:55 chs 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	8.15 (Berkeley) 7/14/95
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 <sys/lockf.h>
53 
54 #include <miscfs/genfs/genfs.h>
55 #include <miscfs/specfs/specdev.h>
56 
57 /* symbolic sleep message strings for devices */
58 const char	devopn[] = "devopn";
59 const char	devio[] = "devio";
60 const char	devwait[] = "devwait";
61 const char	devin[] = "devin";
62 const char	devout[] = "devout";
63 const char	devioc[] = "devioc";
64 const char	devcls[] = "devcls";
65 
66 /*
67  * This vnode operations vector is used for two things only:
68  * - special device nodes created from whole cloth by the kernel.
69  * - as a temporary vnodeops replacement for vnodes which were found to
70  *	be aliased by callers of checkalias().
71  * For the ops vector for vnodes built from special devices found in a
72  * filesystem, see (e.g) ffs_specop_entries[] in ffs_vnops.c or the
73  * equivalent for other filesystems.
74  */
75 
76 int (**spec_vnodeop_p) __P((void *));
77 const struct vnodeopv_entry_desc spec_vnodeop_entries[] = {
78 	{ &vop_default_desc, vn_default_error },
79 	{ &vop_lookup_desc, spec_lookup },		/* lookup */
80 	{ &vop_create_desc, spec_create },		/* create */
81 	{ &vop_mknod_desc, spec_mknod },		/* mknod */
82 	{ &vop_open_desc, spec_open },			/* open */
83 	{ &vop_close_desc, spec_close },		/* close */
84 	{ &vop_access_desc, spec_access },		/* access */
85 	{ &vop_getattr_desc, spec_getattr },		/* getattr */
86 	{ &vop_setattr_desc, spec_setattr },		/* setattr */
87 	{ &vop_read_desc, spec_read },			/* read */
88 	{ &vop_write_desc, spec_write },		/* write */
89 	{ &vop_lease_desc, spec_lease_check },		/* lease */
90 	{ &vop_fcntl_desc, spec_fcntl },		/* fcntl */
91 	{ &vop_ioctl_desc, spec_ioctl },		/* ioctl */
92 	{ &vop_poll_desc, spec_poll },			/* poll */
93 	{ &vop_revoke_desc, spec_revoke },		/* revoke */
94 	{ &vop_mmap_desc, spec_mmap },			/* mmap */
95 	{ &vop_fsync_desc, spec_fsync },		/* fsync */
96 	{ &vop_seek_desc, spec_seek },			/* seek */
97 	{ &vop_remove_desc, spec_remove },		/* remove */
98 	{ &vop_link_desc, spec_link },			/* link */
99 	{ &vop_rename_desc, spec_rename },		/* rename */
100 	{ &vop_mkdir_desc, spec_mkdir },		/* mkdir */
101 	{ &vop_rmdir_desc, spec_rmdir },		/* rmdir */
102 	{ &vop_symlink_desc, spec_symlink },		/* symlink */
103 	{ &vop_readdir_desc, spec_readdir },		/* readdir */
104 	{ &vop_readlink_desc, spec_readlink },		/* readlink */
105 	{ &vop_abortop_desc, spec_abortop },		/* abortop */
106 	{ &vop_inactive_desc, spec_inactive },		/* inactive */
107 	{ &vop_reclaim_desc, spec_reclaim },		/* reclaim */
108 	{ &vop_lock_desc, spec_lock },			/* lock */
109 	{ &vop_unlock_desc, spec_unlock },		/* unlock */
110 	{ &vop_bmap_desc, spec_bmap },			/* bmap */
111 	{ &vop_strategy_desc, spec_strategy },		/* strategy */
112 	{ &vop_print_desc, spec_print },		/* print */
113 	{ &vop_islocked_desc, spec_islocked },		/* islocked */
114 	{ &vop_pathconf_desc, spec_pathconf },		/* pathconf */
115 	{ &vop_advlock_desc, spec_advlock },		/* advlock */
116 	{ &vop_blkatoff_desc, spec_blkatoff },		/* blkatoff */
117 	{ &vop_valloc_desc, spec_valloc },		/* valloc */
118 	{ &vop_vfree_desc, spec_vfree },		/* vfree */
119 	{ &vop_truncate_desc, spec_truncate },		/* truncate */
120 	{ &vop_update_desc, spec_update },		/* update */
121 	{ &vop_bwrite_desc, spec_bwrite },		/* bwrite */
122 	{ &vop_getpages_desc, spec_getpages },		/* getpages */
123 	{ &vop_putpages_desc, spec_putpages },		/* putpages */
124 	{ NULL, NULL }
125 };
126 const struct vnodeopv_desc spec_vnodeop_opv_desc =
127 	{ &spec_vnodeop_p, spec_vnodeop_entries };
128 
129 /*
130  * Trivial lookup routine that always fails.
131  */
132 int
133 spec_lookup(v)
134 	void *v;
135 {
136 	struct vop_lookup_args /* {
137 		struct vnode *a_dvp;
138 		struct vnode **a_vpp;
139 		struct componentname *a_cnp;
140 	} */ *ap = v;
141 
142 	*ap->a_vpp = NULL;
143 	return (ENOTDIR);
144 }
145 
146 /*
147  * Open a special file.
148  */
149 /* ARGSUSED */
150 int
151 spec_open(v)
152 	void *v;
153 {
154 	struct vop_open_args /* {
155 		struct vnode *a_vp;
156 		int  a_mode;
157 		struct ucred *a_cred;
158 		struct proc *a_p;
159 	} */ *ap = v;
160 	struct proc *p = ap->a_p;
161 	struct vnode *bvp, *vp = ap->a_vp;
162 	dev_t bdev, dev = (dev_t)vp->v_rdev;
163 	int maj = major(dev);
164 	int error;
165 	struct partinfo pi;
166 
167 	/*
168 	 * Don't allow open if fs is mounted -nodev.
169 	 */
170 	if (vp->v_mount && (vp->v_mount->mnt_flag & MNT_NODEV))
171 		return (ENXIO);
172 
173 	switch (vp->v_type) {
174 
175 	case VCHR:
176 		if ((u_int)maj >= nchrdev)
177 			return (ENXIO);
178 		if (ap->a_cred != FSCRED && (ap->a_mode & FWRITE)) {
179 			/*
180 			 * When running in very secure mode, do not allow
181 			 * opens for writing of any disk character devices.
182 			 */
183 			if (securelevel >= 2 && cdevsw[maj].d_type == D_DISK)
184 				return (EPERM);
185 			/*
186 			 * When running in secure mode, do not allow opens
187 			 * for writing of /dev/mem, /dev/kmem, or character
188 			 * devices whose corresponding block devices are
189 			 * currently mounted.
190 			 */
191 			if (securelevel >= 1) {
192 				if ((bdev = chrtoblk(dev)) != (dev_t)NODEV &&
193 				    vfinddev(bdev, VBLK, &bvp) &&
194 				    (error = vfs_mountedon(bvp)))
195 					return (error);
196 				if (iskmemdev(dev))
197 					return (EPERM);
198 			}
199 		}
200 		if (cdevsw[maj].d_type == D_TTY)
201 			vp->v_flag |= VISTTY;
202 		VOP_UNLOCK(vp, 0);
203 		error = (*cdevsw[maj].d_open)(dev, ap->a_mode, S_IFCHR, p);
204 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
205 		return (error);
206 
207 	case VBLK:
208 		if ((u_int)maj >= nblkdev)
209 			return (ENXIO);
210 		/*
211 		 * When running in very secure mode, do not allow
212 		 * opens for writing of any disk block devices.
213 		 */
214 		if (securelevel >= 2 && ap->a_cred != FSCRED &&
215 		    (ap->a_mode & FWRITE) && bdevsw[maj].d_type == D_DISK)
216 			return (EPERM);
217 		/*
218 		 * Do not allow opens of block devices that are
219 		 * currently mounted.
220 		 */
221 		if ((error = vfs_mountedon(vp)) != 0)
222 			return (error);
223 		error = (*bdevsw[maj].d_open)(dev, ap->a_mode, S_IFBLK, p);
224 		if (error) {
225 			return error;
226 		}
227 		error = (*bdevsw[major(vp->v_rdev)].d_ioctl)(vp->v_rdev,
228 		    DIOCGPART, (caddr_t)&pi, FREAD, curproc);
229 		if (error == 0) {
230 			vp->v_size = (voff_t)pi.disklab->d_secsize *
231 			    pi.part->p_size;
232 		}
233 		return 0;
234 
235 	case VNON:
236 	case VLNK:
237 	case VDIR:
238 	case VREG:
239 	case VBAD:
240 	case VFIFO:
241 	case VSOCK:
242 		break;
243 	}
244 	return (0);
245 }
246 
247 /*
248  * Vnode op for read
249  */
250 /* ARGSUSED */
251 int
252 spec_read(v)
253 	void *v;
254 {
255 	struct vop_read_args /* {
256 		struct vnode *a_vp;
257 		struct uio *a_uio;
258 		int  a_ioflag;
259 		struct ucred *a_cred;
260 	} */ *ap = v;
261 	struct vnode *vp = ap->a_vp;
262 	struct uio *uio = ap->a_uio;
263  	struct proc *p = uio->uio_procp;
264 	struct buf *bp;
265 	daddr_t bn;
266 	int bsize, bscale, ssize;
267 	struct partinfo dpart;
268 	int n, on, majordev;
269 	int (*ioctl) __P((dev_t, u_long, caddr_t, int, struct proc *));
270 	int error = 0;
271 
272 #ifdef DIAGNOSTIC
273 	if (uio->uio_rw != UIO_READ)
274 		panic("spec_read mode");
275 	if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != curproc)
276 		panic("spec_read proc");
277 #endif
278 	if (uio->uio_resid == 0)
279 		return (0);
280 
281 	switch (vp->v_type) {
282 
283 	case VCHR:
284 		VOP_UNLOCK(vp, 0);
285 		error = (*cdevsw[major(vp->v_rdev)].d_read)
286 			(vp->v_rdev, uio, ap->a_ioflag);
287 		vn_lock(vp, LK_SHARED | LK_RETRY);
288 		return (error);
289 
290 	case VBLK:
291 		if (uio->uio_offset < 0)
292 			return (EINVAL);
293 		bsize = BLKDEV_IOSIZE;
294 		ssize = DEV_BSIZE;
295 		if ((majordev = major(vp->v_rdev)) < nblkdev &&
296 		    (ioctl = bdevsw[majordev].d_ioctl) != NULL &&
297 		    (*ioctl)(vp->v_rdev, DIOCGPART, (caddr_t)&dpart, FREAD, p) == 0) {
298 			if (dpart.part->p_fstype == FS_BSDFFS &&
299 			    dpart.part->p_frag != 0 && dpart.part->p_fsize != 0)
300 				bsize = dpart.part->p_frag *
301 				    dpart.part->p_fsize;
302 			if (dpart.disklab->d_secsize != 0)
303 				ssize = dpart.disklab->d_secsize;
304 		}
305 		bscale = bsize / ssize;
306 		do {
307 			bn = (uio->uio_offset / ssize) &~ (bscale - 1);
308 			on = uio->uio_offset % bsize;
309 			n = min((unsigned)(bsize - on), uio->uio_resid);
310 			error = bread(vp, bn, bsize, NOCRED, &bp);
311 			n = min(n, bsize - bp->b_resid);
312 			if (error) {
313 				brelse(bp);
314 				return (error);
315 			}
316 			error = uiomove((char *)bp->b_data + on, n, uio);
317 			brelse(bp);
318 		} while (error == 0 && uio->uio_resid > 0 && n != 0);
319 		return (error);
320 
321 	default:
322 		panic("spec_read type");
323 	}
324 	/* NOTREACHED */
325 }
326 
327 /*
328  * Vnode op for write
329  */
330 /* ARGSUSED */
331 int
332 spec_write(v)
333 	void *v;
334 {
335 	struct vop_write_args /* {
336 		struct vnode *a_vp;
337 		struct uio *a_uio;
338 		int  a_ioflag;
339 		struct ucred *a_cred;
340 	} */ *ap = v;
341 	struct vnode *vp = ap->a_vp;
342 	struct uio *uio = ap->a_uio;
343 	struct proc *p = uio->uio_procp;
344 	struct buf *bp;
345 	daddr_t bn;
346 	int bsize, bscale, ssize;
347 	struct partinfo dpart;
348 	int n, on, majordev;
349 	int (*ioctl) __P((dev_t, u_long, caddr_t, int, struct proc *));
350 	int error = 0;
351 
352 #ifdef DIAGNOSTIC
353 	if (uio->uio_rw != UIO_WRITE)
354 		panic("spec_write mode");
355 	if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != curproc)
356 		panic("spec_write proc");
357 #endif
358 
359 	switch (vp->v_type) {
360 
361 	case VCHR:
362 		VOP_UNLOCK(vp, 0);
363 		error = (*cdevsw[major(vp->v_rdev)].d_write)
364 			(vp->v_rdev, uio, ap->a_ioflag);
365 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
366 		return (error);
367 
368 	case VBLK:
369 		if (uio->uio_resid == 0)
370 			return (0);
371 		if (uio->uio_offset < 0)
372 			return (EINVAL);
373 		bsize = BLKDEV_IOSIZE;
374 		ssize = DEV_BSIZE;
375 		if ((majordev = major(vp->v_rdev)) < nblkdev &&
376 		    (ioctl = bdevsw[majordev].d_ioctl) != NULL &&
377 		    (*ioctl)(vp->v_rdev, DIOCGPART, (caddr_t)&dpart, FREAD, p) == 0) {
378 			if (dpart.part->p_fstype == FS_BSDFFS &&
379 			    dpart.part->p_frag != 0 && dpart.part->p_fsize != 0)
380 				bsize = dpart.part->p_frag *
381 				    dpart.part->p_fsize;
382 			if (dpart.disklab->d_secsize != 0)
383 				ssize = dpart.disklab->d_secsize;
384 		}
385 		bscale = bsize / ssize;
386 		do {
387 			bn = (uio->uio_offset / ssize) &~ (bscale - 1);
388 			on = uio->uio_offset % bsize;
389 			n = min((unsigned)(bsize - on), uio->uio_resid);
390 			if (n == bsize)
391 				bp = getblk(vp, bn, bsize, 0, 0);
392 			else
393 				error = bread(vp, bn, bsize, NOCRED, &bp);
394 			if (error) {
395 				brelse(bp);
396 				return (error);
397 			}
398 			n = min(n, bsize - bp->b_resid);
399 			error = uiomove((char *)bp->b_data + on, n, uio);
400 			if (error)
401 				brelse(bp);
402 			else {
403 				if (n + on == bsize)
404 					bawrite(bp);
405 				else
406 					bdwrite(bp);
407 				if (bp->b_flags & B_ERROR)
408 					error = bp->b_error;
409 			}
410 		} while (error == 0 && uio->uio_resid > 0 && n != 0);
411 		return (error);
412 
413 	default:
414 		panic("spec_write type");
415 	}
416 	/* NOTREACHED */
417 }
418 
419 /*
420  * Device ioctl operation.
421  */
422 /* ARGSUSED */
423 int
424 spec_ioctl(v)
425 	void *v;
426 {
427 	struct vop_ioctl_args /* {
428 		struct vnode *a_vp;
429 		u_long a_command;
430 		caddr_t  a_data;
431 		int  a_fflag;
432 		struct ucred *a_cred;
433 		struct proc *a_p;
434 	} */ *ap = v;
435 	dev_t dev = ap->a_vp->v_rdev;
436 	int maj = major(dev);
437 
438 	switch (ap->a_vp->v_type) {
439 
440 	case VCHR:
441 		return ((*cdevsw[maj].d_ioctl)(dev, ap->a_command, ap->a_data,
442 		    ap->a_fflag, ap->a_p));
443 
444 	case VBLK:
445 		if (ap->a_command == 0 && (long)ap->a_data == B_TAPE) {
446 			if (bdevsw[maj].d_type == D_TAPE)
447 				return (0);
448 			else
449 				return (1);
450 		}
451 		return ((*bdevsw[maj].d_ioctl)(dev, ap->a_command, ap->a_data,
452 		   ap->a_fflag, ap->a_p));
453 
454 	default:
455 		panic("spec_ioctl");
456 		/* NOTREACHED */
457 	}
458 }
459 
460 /* ARGSUSED */
461 int
462 spec_poll(v)
463 	void *v;
464 {
465 	struct vop_poll_args /* {
466 		struct vnode *a_vp;
467 		int a_events;
468 		struct proc *a_p;
469 	} */ *ap = v;
470 	dev_t dev;
471 
472 	switch (ap->a_vp->v_type) {
473 
474 	case VCHR:
475 		dev = ap->a_vp->v_rdev;
476 		return (*cdevsw[major(dev)].d_poll)(dev, ap->a_events, ap->a_p);
477 
478 	default:
479 		return (genfs_poll(v));
480 	}
481 }
482 /*
483  * Synch buffers associated with a block device
484  */
485 /* ARGSUSED */
486 int
487 spec_fsync(v)
488 	void *v;
489 {
490 	struct vop_fsync_args /* {
491 		struct vnode *a_vp;
492 		struct ucred *a_cred;
493 		int  a_flags;
494 		off_t offlo;
495 		off_t offhi;
496 		struct proc *a_p;
497 	} */ *ap = v;
498 	struct vnode *vp = ap->a_vp;
499 
500 	if (vp->v_type == VBLK)
501 		vflushbuf(vp, (ap->a_flags & FSYNC_WAIT) != 0);
502 	return (0);
503 }
504 
505 /*
506  * Just call the device strategy routine
507  */
508 int
509 spec_strategy(v)
510 	void *v;
511 {
512 	struct vop_strategy_args /* {
513 		struct buf *a_bp;
514 	} */ *ap = v;
515 	struct buf *bp;
516 
517 	bp = ap->a_bp;
518 	if (!(bp->b_flags & B_READ) &&
519 	    (LIST_FIRST(&bp->b_dep)) != NULL && bioops.io_start)
520 		(*bioops.io_start)(bp);
521 	(*bdevsw[major(bp->b_dev)].d_strategy)(bp);
522 	return (0);
523 }
524 
525 int
526 spec_inactive(v)
527 	void *v;
528 {
529 	struct vop_inactive_args /* {
530 		struct vnode *a_vp;
531 		struct proc *a_p;
532 	} */ *ap = v;
533 
534 	VOP_UNLOCK(ap->a_vp, 0);
535 	return (0);
536 }
537 
538 /*
539  * This is a noop, simply returning what one has been given.
540  */
541 int
542 spec_bmap(v)
543 	void *v;
544 {
545 	struct vop_bmap_args /* {
546 		struct vnode *a_vp;
547 		daddr_t  a_bn;
548 		struct vnode **a_vpp;
549 		daddr_t *a_bnp;
550 		int *a_runp;
551 	} */ *ap = v;
552 
553 	if (ap->a_vpp != NULL)
554 		*ap->a_vpp = ap->a_vp;
555 	if (ap->a_bnp != NULL)
556 		*ap->a_bnp = ap->a_bn;
557 	if (ap->a_runp != NULL)
558 		*ap->a_runp = (MAXBSIZE >> DEV_BSHIFT) - 1;
559 	return (0);
560 }
561 
562 /*
563  * Device close routine
564  */
565 /* ARGSUSED */
566 int
567 spec_close(v)
568 	void *v;
569 {
570 	struct vop_close_args /* {
571 		struct vnode *a_vp;
572 		int  a_fflag;
573 		struct ucred *a_cred;
574 		struct proc *a_p;
575 	} */ *ap = v;
576 	struct vnode *vp = ap->a_vp;
577 	dev_t dev = vp->v_rdev;
578 	int (*devclose) __P((dev_t, int, int, struct proc *));
579 	int mode, error, count, flags, flags1;
580 
581 	count = vcount(vp);
582 	simple_lock(&vp->v_interlock);
583 	flags = vp->v_flag;
584 	simple_unlock(&vp->v_interlock);
585 
586 	switch (vp->v_type) {
587 
588 	case VCHR:
589 		/*
590 		 * Hack: a tty device that is a controlling terminal
591 		 * has a reference from the session structure.
592 		 * We cannot easily tell that a character device is
593 		 * a controlling terminal, unless it is the closing
594 		 * process' controlling terminal.  In that case,
595 		 * if the reference count is 2 (this last descriptor
596 		 * plus the session), release the reference from the session.
597 		 */
598 		if (count == 2 && ap->a_p &&
599 		    vp == ap->a_p->p_session->s_ttyvp) {
600 			vrele(vp);
601 			count--;
602 			ap->a_p->p_session->s_ttyvp = NULL;
603 		}
604 		/*
605 		 * If the vnode is locked, then we are in the midst
606 		 * of forcably closing the device, otherwise we only
607 		 * close on last reference.
608 		 */
609 		if (count > 1 && (flags & VXLOCK) == 0)
610 			return (0);
611 		devclose = cdevsw[major(dev)].d_close;
612 		mode = S_IFCHR;
613 		break;
614 
615 	case VBLK:
616 		/*
617 		 * On last close of a block device (that isn't mounted)
618 		 * we must invalidate any in core blocks, so that
619 		 * we can, for instance, change floppy disks.
620 		 */
621 		error = vinvalbuf(vp, V_SAVE, ap->a_cred, ap->a_p, 0, 0);
622 		if (error)
623 			return (error);
624 		/*
625 		 * We do not want to really close the device if it
626 		 * is still in use unless we are trying to close it
627 		 * forcibly. Since every use (buffer, vnode, swap, cmap)
628 		 * holds a reference to the vnode, and because we mark
629 		 * any other vnodes that alias this device, when the
630 		 * sum of the reference counts on all the aliased
631 		 * vnodes descends to one, we are on last close.
632 		 */
633 		if (count > 1 && (flags & VXLOCK) == 0)
634 			return (0);
635 		devclose = bdevsw[major(dev)].d_close;
636 		mode = S_IFBLK;
637 		break;
638 
639 	default:
640 		panic("spec_close: not special");
641 	}
642 
643 	flags1 = ap->a_fflag;
644 
645 	/*
646 	 * if VXLOCK is set, then we're going away soon, so make this
647 	 * non-blocking. Also ensures that we won't wedge in vn_lock below.
648 	 */
649 	if (flags & VXLOCK)
650 		flags1 |= FNONBLOCK;
651 
652 	/*
653 	 * If we're able to block, release the vnode lock & reaquire. We
654 	 * might end up sleaping for someone else who wants our queues. They
655 	 * won't get them if we hold the vnode locked. Also, if VXLOCK is set,
656 	 * don't release the lock as we won't be able to regain it.
657 	 */
658 	if (!(flags1 & FNONBLOCK))
659 		VOP_UNLOCK(vp, 0);
660 
661 	error =  (*devclose)(dev, flags1, mode, ap->a_p);
662 
663 	if (!(flags1 & FNONBLOCK))
664 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
665 
666 	return (error);
667 }
668 
669 /*
670  * Print out the contents of a special device vnode.
671  */
672 int
673 spec_print(v)
674 	void *v;
675 {
676 	struct vop_print_args /* {
677 		struct vnode *a_vp;
678 	} */ *ap = v;
679 
680 	printf("tag VT_NON, dev %d, %d\n", major(ap->a_vp->v_rdev),
681 	    minor(ap->a_vp->v_rdev));
682 	return 0;
683 }
684 
685 /*
686  * Return POSIX pathconf information applicable to special devices.
687  */
688 int
689 spec_pathconf(v)
690 	void *v;
691 {
692 	struct vop_pathconf_args /* {
693 		struct vnode *a_vp;
694 		int a_name;
695 		register_t *a_retval;
696 	} */ *ap = v;
697 
698 	switch (ap->a_name) {
699 	case _PC_LINK_MAX:
700 		*ap->a_retval = LINK_MAX;
701 		return (0);
702 	case _PC_MAX_CANON:
703 		*ap->a_retval = MAX_CANON;
704 		return (0);
705 	case _PC_MAX_INPUT:
706 		*ap->a_retval = MAX_INPUT;
707 		return (0);
708 	case _PC_PIPE_BUF:
709 		*ap->a_retval = PIPE_BUF;
710 		return (0);
711 	case _PC_CHOWN_RESTRICTED:
712 		*ap->a_retval = 1;
713 		return (0);
714 	case _PC_VDISABLE:
715 		*ap->a_retval = _POSIX_VDISABLE;
716 		return (0);
717 	case _PC_SYNC_IO:
718 		*ap->a_retval = 1;
719 		return (0);
720 	default:
721 		return (EINVAL);
722 	}
723 	/* NOTREACHED */
724 }
725 
726 /*
727  * Advisory record locking support.
728  */
729 int
730 spec_advlock(v)
731 	void *v;
732 {
733 	struct vop_advlock_args /* {
734 		struct vnode *a_vp;
735 		caddr_t a_id;
736 		int a_op;
737 		struct flock *a_fl;
738 		int a_flags;
739 	} */ *ap = v;
740 	struct vnode *vp = ap->a_vp;
741 
742 	return lf_advlock(ap, &vp->v_speclockf, (off_t)0);
743 }
744