xref: /netbsd-src/sys/dev/dksubr.c (revision b7b7574d3bf8eeb51a1fa3977b59142ec6434a55)
1 /* $NetBSD: dksubr.c,v 1.51 2014/06/14 07:39:00 hannken Exp $ */
2 
3 /*-
4  * Copyright (c) 1996, 1997, 1998, 1999, 2002, 2008 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Jason R. Thorpe and Roland C. Dowdeswell.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29  * POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 #include <sys/cdefs.h>
33 __KERNEL_RCSID(0, "$NetBSD: dksubr.c,v 1.51 2014/06/14 07:39:00 hannken Exp $");
34 
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/stat.h>
38 #include <sys/proc.h>
39 #include <sys/ioctl.h>
40 #include <sys/device.h>
41 #include <sys/disk.h>
42 #include <sys/disklabel.h>
43 #include <sys/buf.h>
44 #include <sys/bufq.h>
45 #include <sys/vnode.h>
46 #include <sys/fcntl.h>
47 #include <sys/namei.h>
48 #include <sys/module.h>
49 
50 #include <dev/dkvar.h>
51 #include <miscfs/specfs/specdev.h> /* for v_rdev */
52 
53 int	dkdebug = 0;
54 
55 #ifdef DEBUG
56 #define DKDB_FOLLOW	0x1
57 #define DKDB_INIT	0x2
58 #define DKDB_VNODE	0x4
59 
60 #define IFDEBUG(x,y)		if (dkdebug & (x)) y
61 #define DPRINTF(x,y)		IFDEBUG(x, printf y)
62 #define DPRINTF_FOLLOW(y)	DPRINTF(DKDB_FOLLOW, y)
63 #else
64 #define IFDEBUG(x,y)
65 #define DPRINTF(x,y)
66 #define DPRINTF_FOLLOW(y)
67 #endif
68 
69 static int dk_subr_modcmd(modcmd_t, void *);
70 
71 #define DKLABELDEV(dev)	\
72 	(MAKEDISKDEV(major((dev)), DISKUNIT((dev)), RAW_PART))
73 
74 static void	dk_makedisklabel(struct dk_intf *, struct dk_softc *);
75 
76 void
77 dk_sc_init(struct dk_softc *dksc, const char *xname)
78 {
79 
80 	memset(dksc, 0x0, sizeof(*dksc));
81 	strncpy(dksc->sc_xname, xname, DK_XNAME_SIZE);
82 	dksc->sc_dkdev.dk_name = dksc->sc_xname;
83 }
84 
85 /* ARGSUSED */
86 int
87 dk_open(struct dk_intf *di, struct dk_softc *dksc, dev_t dev,
88     int flags, int fmt, struct lwp *l)
89 {
90 	struct	disklabel *lp = dksc->sc_dkdev.dk_label;
91 	int	part = DISKPART(dev);
92 	int	pmask = 1 << part;
93 	int	ret = 0;
94 	struct disk *dk = &dksc->sc_dkdev;
95 
96 	DPRINTF_FOLLOW(("dk_open(%s, %p, 0x%"PRIx64", 0x%x)\n",
97 	    di->di_dkname, dksc, dev, flags));
98 
99 	mutex_enter(&dk->dk_openlock);
100 	part = DISKPART(dev);
101 
102 	/*
103 	 * If there are wedges, and this is not RAW_PART, then we
104 	 * need to fail.
105 	 */
106 	if (dk->dk_nwedges != 0 && part != RAW_PART) {
107 		ret = EBUSY;
108 		goto done;
109 	}
110 
111 	pmask = 1 << part;
112 
113 	/*
114 	 * If we're init'ed and there are no other open partitions then
115 	 * update the in-core disklabel.
116 	 */
117 	if ((dksc->sc_flags & DKF_INITED)) {
118 		if (dk->dk_openmask == 0) {
119 			dk_getdisklabel(di, dksc, dev);
120 		}
121 		/* XXX re-discover wedges? */
122 	}
123 
124 	/* Fail if we can't find the partition. */
125 	if ((part != RAW_PART) &&
126 	    (((dksc->sc_flags & DKF_INITED) == 0) ||
127 	    ((part >= lp->d_npartitions) ||
128 	    (lp->d_partitions[part].p_fstype == FS_UNUSED)))) {
129 		ret = ENXIO;
130 		goto done;
131 	}
132 
133 	/* Mark our unit as open. */
134 	switch (fmt) {
135 	case S_IFCHR:
136 		dk->dk_copenmask |= pmask;
137 		break;
138 	case S_IFBLK:
139 		dk->dk_bopenmask |= pmask;
140 		break;
141 	}
142 
143 	dk->dk_openmask = dk->dk_copenmask | dk->dk_bopenmask;
144 
145 done:
146 	mutex_exit(&dk->dk_openlock);
147 	return ret;
148 }
149 
150 /* ARGSUSED */
151 int
152 dk_close(struct dk_intf *di, struct dk_softc *dksc, dev_t dev,
153     int flags, int fmt, struct lwp *l)
154 {
155 	int	part = DISKPART(dev);
156 	int	pmask = 1 << part;
157 	struct disk *dk = &dksc->sc_dkdev;
158 
159 	DPRINTF_FOLLOW(("dk_close(%s, %p, 0x%"PRIx64", 0x%x)\n",
160 	    di->di_dkname, dksc, dev, flags));
161 
162 	mutex_enter(&dk->dk_openlock);
163 
164 	switch (fmt) {
165 	case S_IFCHR:
166 		dk->dk_copenmask &= ~pmask;
167 		break;
168 	case S_IFBLK:
169 		dk->dk_bopenmask &= ~pmask;
170 		break;
171 	}
172 	dk->dk_openmask = dk->dk_copenmask | dk->dk_bopenmask;
173 
174 	mutex_exit(&dk->dk_openlock);
175 	return 0;
176 }
177 
178 void
179 dk_strategy(struct dk_intf *di, struct dk_softc *dksc, struct buf *bp)
180 {
181 	int	s;
182 	int	wlabel;
183 	daddr_t	blkno;
184 
185 	DPRINTF_FOLLOW(("dk_strategy(%s, %p, %p)\n",
186 	    di->di_dkname, dksc, bp));
187 
188 	if (!(dksc->sc_flags & DKF_INITED)) {
189 		DPRINTF_FOLLOW(("dk_strategy: not inited\n"));
190 		bp->b_error  = ENXIO;
191 		biodone(bp);
192 		return;
193 	}
194 
195 	/* XXX look for some more errors, c.f. ld.c */
196 
197 	bp->b_resid = bp->b_bcount;
198 
199 	/* If there is nothing to do, then we are done */
200 	if (bp->b_bcount == 0) {
201 		biodone(bp);
202 		return;
203 	}
204 
205 	wlabel = dksc->sc_flags & (DKF_WLABEL|DKF_LABELLING);
206 	if (DISKPART(bp->b_dev) != RAW_PART &&
207 	    bounds_check_with_label(&dksc->sc_dkdev, bp, wlabel) <= 0) {
208 		biodone(bp);
209 		return;
210 	}
211 
212 	blkno = bp->b_blkno;
213 	if (DISKPART(bp->b_dev) != RAW_PART) {
214 		struct partition *pp;
215 
216 		pp =
217 		    &dksc->sc_dkdev.dk_label->d_partitions[DISKPART(bp->b_dev)];
218 		blkno += pp->p_offset;
219 	}
220 	bp->b_rawblkno = blkno;
221 
222 	/*
223 	 * Start the unit by calling the start routine
224 	 * provided by the individual driver.
225 	 */
226 	s = splbio();
227 	bufq_put(dksc->sc_bufq, bp);
228 	di->di_diskstart(dksc);
229 	splx(s);
230 	return;
231 }
232 
233 int
234 dk_size(struct dk_intf *di, struct dk_softc *dksc, dev_t dev)
235 {
236 	struct	disklabel *lp;
237 	int	is_open;
238 	int	part;
239 	int	size;
240 
241 	if ((dksc->sc_flags & DKF_INITED) == 0)
242 		return -1;
243 
244 	part = DISKPART(dev);
245 	is_open = dksc->sc_dkdev.dk_openmask & (1 << part);
246 
247 	if (!is_open && di->di_open(dev, 0, S_IFBLK, curlwp))
248 		return -1;
249 
250 	lp = dksc->sc_dkdev.dk_label;
251 	if (lp->d_partitions[part].p_fstype != FS_SWAP)
252 		size = -1;
253 	else
254 		size = lp->d_partitions[part].p_size *
255 		    (lp->d_secsize / DEV_BSIZE);
256 
257 	if (!is_open && di->di_close(dev, 0, S_IFBLK, curlwp))
258 		return 1;
259 
260 	return size;
261 }
262 
263 int
264 dk_ioctl(struct dk_intf *di, struct dk_softc *dksc, dev_t dev,
265 	    u_long cmd, void *data, int flag, struct lwp *l)
266 {
267 	struct	disklabel *lp;
268 	struct	disk *dk;
269 #ifdef __HAVE_OLD_DISKLABEL
270 	struct	disklabel newlabel;
271 #endif
272 	int	error = 0;
273 
274 	DPRINTF_FOLLOW(("dk_ioctl(%s, %p, 0x%"PRIx64", 0x%lx)\n",
275 	    di->di_dkname, dksc, dev, cmd));
276 
277 	/* ensure that the pseudo disk is open for writes for these commands */
278 	switch (cmd) {
279 	case DIOCSDINFO:
280 	case DIOCWDINFO:
281 #ifdef __HAVE_OLD_DISKLABEL
282 	case ODIOCSDINFO:
283 	case ODIOCWDINFO:
284 #endif
285 	case DIOCWLABEL:
286 	case DIOCAWEDGE:
287 	case DIOCDWEDGE:
288 		if ((flag & FWRITE) == 0)
289 			return EBADF;
290 	}
291 
292 	/* ensure that the pseudo-disk is initialized for these */
293 	switch (cmd) {
294 #ifdef DIOCGSECTORSIZE
295 	case DIOCGSECTORSIZE:
296 	case DIOCGMEDIASIZE:
297 #endif
298 	case DIOCGDINFO:
299 	case DIOCSDINFO:
300 	case DIOCWDINFO:
301 	case DIOCGPART:
302 	case DIOCWLABEL:
303 	case DIOCGDEFLABEL:
304 	case DIOCAWEDGE:
305 	case DIOCDWEDGE:
306 	case DIOCLWEDGES:
307 	case DIOCCACHESYNC:
308 #ifdef __HAVE_OLD_DISKLABEL
309 	case ODIOCGDINFO:
310 	case ODIOCSDINFO:
311 	case ODIOCWDINFO:
312 	case ODIOCGDEFLABEL:
313 #endif
314 		if ((dksc->sc_flags & DKF_INITED) == 0)
315 			return ENXIO;
316 	}
317 
318 	switch (cmd) {
319 #ifdef DIOCGSECTORSIZE
320 	case DIOCGSECTORSIZE:
321 		*(u_int *)data = dksc->sc_dkdev.dk_geom.dg_secsize;
322 		return 0;
323 	case DIOCGMEDIASIZE:
324 		*(off_t *)data =
325 		    (off_t)dksc->sc_dkdev.dk_geom.dg_secsize *
326 		    dksc->sc_dkdev.dk_geom.dg_nsectors;
327 		return 0;
328 #endif
329 
330 	case DIOCGDINFO:
331 		*(struct disklabel *)data = *(dksc->sc_dkdev.dk_label);
332 		break;
333 
334 #ifdef __HAVE_OLD_DISKLABEL
335 	case ODIOCGDINFO:
336 		newlabel = *(dksc->sc_dkdev.dk_label);
337 		if (newlabel.d_npartitions > OLDMAXPARTITIONS)
338 			return ENOTTY;
339 		memcpy(data, &newlabel, sizeof (struct olddisklabel));
340 		break;
341 #endif
342 
343 	case DIOCGPART:
344 		((struct partinfo *)data)->disklab = dksc->sc_dkdev.dk_label;
345 		((struct partinfo *)data)->part =
346 		    &dksc->sc_dkdev.dk_label->d_partitions[DISKPART(dev)];
347 		break;
348 
349 	case DIOCWDINFO:
350 	case DIOCSDINFO:
351 #ifdef __HAVE_OLD_DISKLABEL
352 	case ODIOCWDINFO:
353 	case ODIOCSDINFO:
354 #endif
355 #ifdef __HAVE_OLD_DISKLABEL
356 		if (cmd == ODIOCSDINFO || cmd == ODIOCWDINFO) {
357 			memset(&newlabel, 0, sizeof newlabel);
358 			memcpy(&newlabel, data, sizeof (struct olddisklabel));
359 			lp = &newlabel;
360 		} else
361 #endif
362 		lp = (struct disklabel *)data;
363 
364 		dk = &dksc->sc_dkdev;
365 		mutex_enter(&dk->dk_openlock);
366 		dksc->sc_flags |= DKF_LABELLING;
367 
368 		error = setdisklabel(dksc->sc_dkdev.dk_label,
369 		    lp, 0, dksc->sc_dkdev.dk_cpulabel);
370 		if (error == 0) {
371 			if (cmd == DIOCWDINFO
372 #ifdef __HAVE_OLD_DISKLABEL
373 			    || cmd == ODIOCWDINFO
374 #endif
375 			   )
376 				error = writedisklabel(DKLABELDEV(dev),
377 				    di->di_strategy, dksc->sc_dkdev.dk_label,
378 				    dksc->sc_dkdev.dk_cpulabel);
379 		}
380 
381 		dksc->sc_flags &= ~DKF_LABELLING;
382 		mutex_exit(&dk->dk_openlock);
383 		break;
384 
385 	case DIOCWLABEL:
386 		if (*(int *)data != 0)
387 			dksc->sc_flags |= DKF_WLABEL;
388 		else
389 			dksc->sc_flags &= ~DKF_WLABEL;
390 		break;
391 
392 	case DIOCGDEFLABEL:
393 		dk_getdefaultlabel(di, dksc, (struct disklabel *)data);
394 		break;
395 
396 #ifdef __HAVE_OLD_DISKLABEL
397 	case ODIOCGDEFLABEL:
398 		dk_getdefaultlabel(di, dksc, &newlabel);
399 		if (newlabel.d_npartitions > OLDMAXPARTITIONS)
400 			return ENOTTY;
401 		memcpy(data, &newlabel, sizeof (struct olddisklabel));
402 		break;
403 #endif
404 
405 	case DIOCAWEDGE:
406 	    {
407 	    	struct dkwedge_info *dkw = (void *)data;
408 
409 		if ((flag & FWRITE) == 0)
410 			return (EBADF);
411 
412 		/* If the ioctl happens here, the parent is us. */
413 		strcpy(dkw->dkw_parent, dksc->sc_dkdev.dk_name);
414 		return (dkwedge_add(dkw));
415 	    }
416 
417 	case DIOCDWEDGE:
418 	    {
419 	    	struct dkwedge_info *dkw = (void *)data;
420 
421 		if ((flag & FWRITE) == 0)
422 			return (EBADF);
423 
424 		/* If the ioctl happens here, the parent is us. */
425 		strcpy(dkw->dkw_parent, dksc->sc_dkdev.dk_name);
426 		return (dkwedge_del(dkw));
427 	    }
428 
429 	case DIOCLWEDGES:
430 	    {
431 	    	struct dkwedge_list *dkwl = (void *)data;
432 
433 		return (dkwedge_list(&dksc->sc_dkdev, dkwl, l));
434 	    }
435 
436 	case DIOCGSTRATEGY:
437 	    {
438 		struct disk_strategy *dks = (void *)data;
439 		int s;
440 
441 		s = splbio();
442 		strlcpy(dks->dks_name, bufq_getstrategyname(dksc->sc_bufq),
443 		    sizeof(dks->dks_name));
444 		splx(s);
445 		dks->dks_paramlen = 0;
446 
447 		return 0;
448 	    }
449 
450 	case DIOCSSTRATEGY:
451 	    {
452 		struct disk_strategy *dks = (void *)data;
453 		struct bufq_state *new;
454 		struct bufq_state *old;
455 		int s;
456 
457 		if ((flag & FWRITE) == 0) {
458 			return EBADF;
459 		}
460 		if (dks->dks_param != NULL) {
461 			return EINVAL;
462 		}
463 		dks->dks_name[sizeof(dks->dks_name) - 1] = 0; /* ensure term */
464 		error = bufq_alloc(&new, dks->dks_name,
465 		    BUFQ_EXACT|BUFQ_SORT_RAWBLOCK);
466 		if (error) {
467 			return error;
468 		}
469 		s = splbio();
470 		old = dksc->sc_bufq;
471 		bufq_move(new, old);
472 		dksc->sc_bufq = new;
473 		splx(s);
474 		bufq_free(old);
475 
476 		return 0;
477 	    }
478 
479 	default:
480 		error = ENOTTY;
481 	}
482 
483 	return error;
484 }
485 
486 /*
487  * dk_dump dumps all of physical memory into the partition specified.
488  * This requires substantially more framework than {s,w}ddump, and hence
489  * is probably much more fragile.
490  *
491  * XXX: we currently do not implement this.
492  */
493 
494 #define DKF_READYFORDUMP	(DKF_INITED|DKF_TAKEDUMP)
495 #define DKFF_READYFORDUMP(x)	(((x) & DKF_READYFORDUMP) == DKF_READYFORDUMP)
496 static volatile int	dk_dumping = 0;
497 
498 /* ARGSUSED */
499 int
500 dk_dump(struct dk_intf *di, struct dk_softc *dksc, dev_t dev,
501     daddr_t blkno, void *va, size_t size)
502 {
503 
504 	/*
505 	 * ensure that we consider this device to be safe for dumping,
506 	 * and that the device is configured.
507 	 */
508 	if (!DKFF_READYFORDUMP(dksc->sc_flags))
509 		return ENXIO;
510 
511 	/* ensure that we are not already dumping */
512 	if (dk_dumping)
513 		return EFAULT;
514 	dk_dumping = 1;
515 
516 	/* XXX: unimplemented */
517 
518 	dk_dumping = 0;
519 
520 	/* XXX: actually for now, we are going to leave this alone */
521 	return ENXIO;
522 }
523 
524 /* ARGSUSED */
525 void
526 dk_getdefaultlabel(struct dk_intf *di, struct dk_softc *dksc,
527 		      struct disklabel *lp)
528 {
529 	struct disk_geom *dg = &dksc->sc_dkdev.dk_geom;
530 
531 	memset(lp, 0, sizeof(*lp));
532 
533 	lp->d_secperunit = dg->dg_secperunit;
534 	lp->d_secsize = dg->dg_secsize;
535 	lp->d_nsectors = dg->dg_nsectors;
536 	lp->d_ntracks = dg->dg_ntracks;
537 	lp->d_ncylinders = dg->dg_ncylinders;
538 	lp->d_secpercyl = lp->d_ntracks * lp->d_nsectors;
539 
540 	strncpy(lp->d_typename, di->di_dkname, sizeof(lp->d_typename));
541 	lp->d_type = di->di_dtype;
542 	strncpy(lp->d_packname, "fictitious", sizeof(lp->d_packname));
543 	lp->d_rpm = 3600;
544 	lp->d_interleave = 1;
545 	lp->d_flags = 0;
546 
547 	lp->d_partitions[RAW_PART].p_offset = 0;
548 	lp->d_partitions[RAW_PART].p_size = dg->dg_secperunit;
549 	lp->d_partitions[RAW_PART].p_fstype = FS_UNUSED;
550 	lp->d_npartitions = RAW_PART + 1;
551 
552 	lp->d_magic = DISKMAGIC;
553 	lp->d_magic2 = DISKMAGIC;
554 	lp->d_checksum = dkcksum(dksc->sc_dkdev.dk_label);
555 }
556 
557 /* ARGSUSED */
558 void
559 dk_getdisklabel(struct dk_intf *di, struct dk_softc *dksc, dev_t dev)
560 {
561 	struct	 disklabel *lp = dksc->sc_dkdev.dk_label;
562 	struct	 cpu_disklabel *clp = dksc->sc_dkdev.dk_cpulabel;
563 	struct disk_geom *dg = &dksc->sc_dkdev.dk_geom;
564 	struct	 partition *pp;
565 	int	 i;
566 	const char	*errstring;
567 
568 	memset(clp, 0x0, sizeof(*clp));
569 	dk_getdefaultlabel(di, dksc, lp);
570 	errstring = readdisklabel(DKLABELDEV(dev), di->di_strategy,
571 	    dksc->sc_dkdev.dk_label, dksc->sc_dkdev.dk_cpulabel);
572 	if (errstring) {
573 		dk_makedisklabel(di, dksc);
574 		if (dksc->sc_flags & DKF_WARNLABEL)
575 			printf("%s: %s\n", dksc->sc_xname, errstring);
576 		return;
577 	}
578 
579 	if ((dksc->sc_flags & DKF_LABELSANITY) == 0)
580 		return;
581 
582 	/* Sanity check */
583 	if (lp->d_secperunit != dg->dg_secperunit)
584 		printf("WARNING: %s: total sector size in disklabel (%d) "
585 		    "!= the size of %s (%" PRId64 ")\n", dksc->sc_xname,
586 		    lp->d_secperunit, di->di_dkname, dg->dg_secperunit);
587 
588 	for (i=0; i < lp->d_npartitions; i++) {
589 		pp = &lp->d_partitions[i];
590 		if (pp->p_offset + pp->p_size > dg->dg_secperunit)
591 			printf("WARNING: %s: end of partition `%c' exceeds "
592 			    "the size of %s (%" PRId64 ")\n", dksc->sc_xname,
593 			    'a' + i, di->di_dkname, dg->dg_secperunit);
594 	}
595 }
596 
597 /* ARGSUSED */
598 static void
599 dk_makedisklabel(struct dk_intf *di, struct dk_softc *dksc)
600 {
601 	struct	disklabel *lp = dksc->sc_dkdev.dk_label;
602 
603 	lp->d_partitions[RAW_PART].p_fstype = FS_BSDFFS;
604 	strncpy(lp->d_packname, "default label", sizeof(lp->d_packname));
605 	lp->d_checksum = dkcksum(lp);
606 }
607 
608 /* This function is taken from ccd.c:1.76  --rcd */
609 
610 /*
611  * XXX this function looks too generic for dksubr.c, shouldn't we
612  *     put it somewhere better?
613  */
614 
615 /*
616  * Lookup the provided name in the filesystem.  If the file exists,
617  * is a valid block device, and isn't being used by anyone else,
618  * set *vpp to the file's vnode.
619  */
620 int
621 dk_lookup(struct pathbuf *pb, struct lwp *l, struct vnode **vpp)
622 {
623 	struct nameidata nd;
624 	struct vnode *vp;
625 	int     error;
626 
627 	if (l == NULL)
628 		return ESRCH;	/* Is ESRCH the best choice? */
629 
630 	NDINIT(&nd, LOOKUP, FOLLOW, pb);
631 	if ((error = vn_open(&nd, FREAD | FWRITE, 0)) != 0) {
632 		DPRINTF((DKDB_FOLLOW|DKDB_INIT),
633 		    ("dk_lookup: vn_open error = %d\n", error));
634 		return error;
635 	}
636 
637 	vp = nd.ni_vp;
638 	if (vp->v_type != VBLK) {
639 		error = ENOTBLK;
640 		goto out;
641 	}
642 
643 	/* Reopen as anonymous vnode to protect against forced unmount. */
644 	if ((error = bdevvp(vp->v_rdev, vpp)) != 0)
645 		goto out;
646 	VOP_UNLOCK(vp);
647 	if ((error = vn_close(vp, FREAD | FWRITE, l->l_cred)) != 0) {
648 		vrele(*vpp);
649 		return error;
650 	}
651 	if ((error = VOP_OPEN(*vpp, FREAD | FWRITE, l->l_cred)) != 0) {
652 		vrele(*vpp);
653 		return error;
654 	}
655 	mutex_enter((*vpp)->v_interlock);
656 	(*vpp)->v_writecount++;
657 	mutex_exit((*vpp)->v_interlock);
658 
659 	IFDEBUG(DKDB_VNODE, vprint("dk_lookup: vnode info", *vpp));
660 
661 	return 0;
662 out:
663 	VOP_UNLOCK(vp);
664 	(void) vn_close(vp, FREAD | FWRITE, l->l_cred);
665 	return error;
666 }
667 
668 MODULE(MODULE_CLASS_MISC, dk_subr, NULL);
669 
670 static int
671 dk_subr_modcmd(modcmd_t cmd, void *arg)
672 {
673 	switch (cmd) {
674 	case MODULE_CMD_INIT:
675 	case MODULE_CMD_FINI:
676 		return 0;
677 	case MODULE_CMD_STAT:
678 	case MODULE_CMD_AUTOUNLOAD:
679 	default:
680 		return ENOTTY;
681 	}
682 }
683