xref: /netbsd-src/sys/dev/vnd.c (revision 76dfffe33547c37f8bdd446e3e4ab0f3c16cea4b)
1 /*	$NetBSD: vnd.c,v 1.30 1996/10/13 01:37:08 christos Exp $	*/
2 
3 /*
4  * Copyright (c) 1988 University of Utah.
5  * Copyright (c) 1990, 1993
6  *	The Regents of the University of California.  All rights reserved.
7  *
8  * This code is derived from software contributed to Berkeley by
9  * the Systems Programming Group of the University of Utah Computer
10  * Science Department.
11  *
12  * Redistribution and use in source and binary forms, with or without
13  * modification, are permitted provided that the following conditions
14  * are met:
15  * 1. Redistributions of source code must retain the above copyright
16  *    notice, this list of conditions and the following disclaimer.
17  * 2. Redistributions in binary form must reproduce the above copyright
18  *    notice, this list of conditions and the following disclaimer in the
19  *    documentation and/or other materials provided with the distribution.
20  * 3. All advertising materials mentioning features or use of this software
21  *    must display the following acknowledgement:
22  *	This product includes software developed by the University of
23  *	California, Berkeley and its contributors.
24  * 4. Neither the name of the University nor the names of its contributors
25  *    may be used to endorse or promote products derived from this software
26  *    without specific prior written permission.
27  *
28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38  * SUCH DAMAGE.
39  *
40  * from: Utah $Hdr: vn.c 1.13 94/04/02$
41  *
42  *	@(#)vn.c	8.6 (Berkeley) 4/1/94
43  */
44 
45 /*
46  * Vnode disk driver.
47  *
48  * Block/character interface to a vnode.  Allows one to treat a file
49  * as a disk (e.g. build a filesystem in it, mount it, etc.).
50  *
51  * NOTE 1: This uses the VOP_BMAP/VOP_STRATEGY interface to the vnode
52  * instead of a simple VOP_RDWR.  We do this to avoid distorting the
53  * local buffer cache.
54  *
55  * NOTE 2: There is a security issue involved with this driver.
56  * Once mounted all access to the contents of the "mapped" file via
57  * the special file is controlled by the permissions on the special
58  * file, the protection of the mapped file is ignored (effectively,
59  * by using root credentials in all transactions).
60  *
61  * NOTE 3: Doesn't interact with leases, should it?
62  */
63 
64 #include <sys/param.h>
65 #include <sys/systm.h>
66 #include <sys/namei.h>
67 #include <sys/proc.h>
68 #include <sys/errno.h>
69 #include <sys/buf.h>
70 #include <sys/malloc.h>
71 #include <sys/ioctl.h>
72 #include <sys/disklabel.h>
73 #include <sys/device.h>
74 #include <sys/disk.h>
75 #include <sys/stat.h>
76 #include <sys/mount.h>
77 #include <sys/vnode.h>
78 #include <sys/file.h>
79 #include <sys/uio.h>
80 #include <sys/conf.h>
81 
82 #include <miscfs/specfs/specdev.h>
83 
84 #include <dev/vndioctl.h>
85 
86 #ifdef DEBUG
87 int dovndcluster = 1;
88 int vnddebug = 0x00;
89 #define VDB_FOLLOW	0x01
90 #define VDB_INIT	0x02
91 #define VDB_IO		0x04
92 #endif
93 
94 #define b_cylin	b_resid
95 
96 #define	vndunit(x)	DISKUNIT(x)
97 
98 struct vndbuf {
99 	struct buf	vb_buf;
100 	struct buf	*vb_obp;
101 };
102 
103 #define	getvndbuf()	\
104 	((struct vndbuf *)malloc(sizeof(struct vndbuf), M_DEVBUF, M_WAITOK))
105 #define putvndbuf(vbp)	\
106 	free((caddr_t)(vbp), M_DEVBUF)
107 
108 struct vnd_softc {
109 	int		 sc_flags;	/* flags */
110 	size_t		 sc_size;	/* size of vnd */
111 	struct vnode	*sc_vp;		/* vnode */
112 	struct ucred	*sc_cred;	/* credentials */
113 	int		 sc_maxactive;	/* max # of active requests */
114 	struct buf	 sc_tab;	/* transfer queue */
115 	char		 sc_xname[8];	/* XXX external name */
116 	struct disk	 sc_dkdev;	/* generic disk device info */
117 };
118 
119 /* sc_flags */
120 #define	VNF_ALIVE	0x01
121 #define VNF_INITED	0x02
122 #define VNF_WANTED	0x40
123 #define VNF_LOCKED	0x80
124 
125 struct vnd_softc *vnd_softc;
126 int numvnd = 0;
127 
128 /* called by main() at boot time */
129 void	vndattach __P((int));
130 
131 void	vndclear __P((struct vnd_softc *));
132 void	vndstart __P((struct vnd_softc *));
133 int	vndsetcred __P((struct vnd_softc *, struct ucred *));
134 void	vndthrottle __P((struct vnd_softc *, struct vnode *));
135 void	vndiodone __P((struct buf *));
136 void	vndshutdown __P((void));
137 
138 static	int vndlock __P((struct vnd_softc *));
139 static	void vndunlock __P((struct vnd_softc *));
140 
141 void
142 vndattach(num)
143 	int num;
144 {
145 	char *mem;
146 	register u_long size;
147 
148 	if (num <= 0)
149 		return;
150 	size = num * sizeof(struct vnd_softc);
151 	mem = malloc(size, M_DEVBUF, M_NOWAIT);
152 	if (mem == NULL) {
153 		printf("WARNING: no memory for vnode disks\n");
154 		return;
155 	}
156 	bzero(mem, size);
157 	vnd_softc = (struct vnd_softc *)mem;
158 	numvnd = num;
159 }
160 
161 int
162 vndopen(dev, flags, mode, p)
163 	dev_t dev;
164 	int flags, mode;
165 	struct proc *p;
166 {
167 	int unit = vndunit(dev);
168 	struct vnd_softc *sc;
169 	int error = 0, part, pmask;
170 
171 	/*
172 	 * XXX Should support disklabels.
173 	 */
174 
175 #ifdef DEBUG
176 	if (vnddebug & VDB_FOLLOW)
177 		printf("vndopen(%x, %x, %x, %p)\n", dev, flags, mode, p);
178 #endif
179 	if (unit >= numvnd)
180 		return (ENXIO);
181 	sc = &vnd_softc[unit];
182 
183 	if ((error = vndlock(sc)) != 0)
184 		return (error);
185 
186 	part = DISKPART(dev);
187 	pmask = (1 << part);
188 
189 	/* Prevent our unit from being unconfigured while open. */
190 	switch (mode) {
191 	case S_IFCHR:
192 		sc->sc_dkdev.dk_copenmask |= pmask;
193 		break;
194 
195 	case S_IFBLK:
196 		sc->sc_dkdev.dk_bopenmask |= pmask;
197 		break;
198 	}
199 	sc->sc_dkdev.dk_openmask =
200 	    sc->sc_dkdev.dk_copenmask | sc->sc_dkdev.dk_bopenmask;
201 
202 	vndunlock(sc);
203 	return (0);
204 }
205 
206 int
207 vndclose(dev, flags, mode, p)
208 	dev_t dev;
209 	int flags, mode;
210 	struct proc *p;
211 {
212 	int unit = vndunit(dev);
213 	struct vnd_softc *sc;
214 	int error = 0, part;
215 
216 #ifdef DEBUG
217 	if (vnddebug & VDB_FOLLOW)
218 		printf("vndclose(%x, %x, %x, %p)\n", dev, flags, mode, p);
219 #endif
220 
221 	if (unit >= numvnd)
222 		return (ENXIO);
223 	sc = &vnd_softc[unit];
224 
225 	if ((error = vndlock(sc)) != 0)
226 		return (error);
227 
228 	part = DISKPART(dev);
229 
230 	/* ...that much closer to allowing unconfiguration... */
231 	switch (mode) {
232 	case S_IFCHR:
233 		sc->sc_dkdev.dk_copenmask &= ~(1 << part);
234 		break;
235 
236 	case S_IFBLK:
237 		sc->sc_dkdev.dk_bopenmask &= ~(1 << part);
238 		break;
239 	}
240 	sc->sc_dkdev.dk_openmask =
241 	    sc->sc_dkdev.dk_copenmask | sc->sc_dkdev.dk_bopenmask;
242 
243 	vndunlock(sc);
244 	return (0);
245 }
246 
247 /*
248  * Break the request into bsize pieces and submit using VOP_BMAP/VOP_STRATEGY.
249  * Note that this driver can only be used for swapping over NFS on the hp
250  * since nfs_strategy on the vax cannot handle u-areas and page tables.
251  */
252 void
253 vndstrategy(bp)
254 	register struct buf *bp;
255 {
256 	int unit = vndunit(bp->b_dev);
257 	register struct vnd_softc *vnd = &vnd_softc[unit];
258 	register struct vndbuf *nbp;
259 	register int bn, bsize, resid;
260 	register caddr_t addr;
261 	int sz, flags, error;
262 
263 #ifdef DEBUG
264 	if (vnddebug & VDB_FOLLOW)
265 		printf("vndstrategy(%p): unit %d\n", bp, unit);
266 #endif
267 	if ((vnd->sc_flags & VNF_INITED) == 0) {
268 		bp->b_error = ENXIO;
269 		bp->b_flags |= B_ERROR;
270 		biodone(bp);
271 		return;
272 	}
273 	bn = bp->b_blkno;
274 	sz = howmany(bp->b_bcount, DEV_BSIZE);
275 	bp->b_resid = bp->b_bcount;
276 	if (bn < 0 || bn + sz > vnd->sc_size) {
277 		if (bn != vnd->sc_size) {
278 			bp->b_error = EINVAL;
279 			bp->b_flags |= B_ERROR;
280 		}
281 		biodone(bp);
282 		return;
283 	}
284 	bn = dbtob(bn);
285  	bsize = vnd->sc_vp->v_mount->mnt_stat.f_iosize;
286 	addr = bp->b_data;
287 	flags = bp->b_flags | B_CALL;
288 	for (resid = bp->b_resid; resid; resid -= sz) {
289 		struct vnode *vp;
290 		daddr_t nbn;
291 		int off, s, nra;
292 
293 		nra = 0;
294 		VOP_LOCK(vnd->sc_vp);
295 		error = VOP_BMAP(vnd->sc_vp, bn / bsize, &vp, &nbn, &nra);
296 		VOP_UNLOCK(vnd->sc_vp);
297 		if (error == 0 && (long)nbn == -1)
298 			error = EIO;
299 #ifdef DEBUG
300 		if (!dovndcluster)
301 			nra = 0;
302 #endif
303 
304 		if ((off = bn % bsize) != 0)
305 			sz = bsize - off;
306 		else
307 			sz = (1 + nra) * bsize;
308 		if (resid < sz)
309 			sz = resid;
310 #ifdef DEBUG
311 		if (vnddebug & VDB_IO)
312 			printf("vndstrategy: vp %p/%p bn %x/%x sz %x\n",
313 			    vnd->sc_vp, vp, bn, nbn, sz);
314 #endif
315 
316 		nbp = getvndbuf();
317 		nbp->vb_buf.b_flags = flags;
318 		nbp->vb_buf.b_bcount = sz;
319 		nbp->vb_buf.b_bufsize = bp->b_bufsize;
320 		nbp->vb_buf.b_error = 0;
321 		if (vp->v_type == VBLK || vp->v_type == VCHR)
322 			nbp->vb_buf.b_dev = vp->v_rdev;
323 		else
324 			nbp->vb_buf.b_dev = NODEV;
325 		nbp->vb_buf.b_data = addr;
326 		nbp->vb_buf.b_blkno = nbn + btodb(off);
327 		nbp->vb_buf.b_proc = bp->b_proc;
328 		nbp->vb_buf.b_iodone = vndiodone;
329 		nbp->vb_buf.b_vp = vp;
330 		nbp->vb_buf.b_rcred = vnd->sc_cred;	/* XXX crdup? */
331 		nbp->vb_buf.b_wcred = vnd->sc_cred;	/* XXX crdup? */
332 		nbp->vb_buf.b_dirtyoff = bp->b_dirtyoff;
333 		nbp->vb_buf.b_dirtyend = bp->b_dirtyend;
334 		nbp->vb_buf.b_validoff = bp->b_validoff;
335 		nbp->vb_buf.b_validend = bp->b_validend;
336 
337 		/* save a reference to the old buffer */
338 		nbp->vb_obp = bp;
339 
340 		/*
341 		 * If there was an error or a hole in the file...punt.
342 		 * Note that we deal with this after the nbp allocation.
343 		 * This ensures that we properly clean up any operations
344 		 * that we have already fired off.
345 		 *
346 		 * XXX we could deal with holes here but it would be
347 		 * a hassle (in the write case).
348 		 */
349 		if (error) {
350 			nbp->vb_buf.b_error = error;
351 			nbp->vb_buf.b_flags |= B_ERROR;
352 			bp->b_resid -= (resid - sz);
353 			biodone(&nbp->vb_buf);
354 			return;
355 		}
356 		/*
357 		 * Just sort by block number
358 		 */
359 		nbp->vb_buf.b_cylin = nbp->vb_buf.b_blkno;
360 		s = splbio();
361 		disksort(&vnd->sc_tab, &nbp->vb_buf);
362 		if (vnd->sc_tab.b_active < vnd->sc_maxactive) {
363 			vnd->sc_tab.b_active++;
364 			vndstart(vnd);
365 		}
366 		splx(s);
367 		bn += sz;
368 		addr += sz;
369 	}
370 }
371 
372 /*
373  * Feed requests sequentially.
374  * We do it this way to keep from flooding NFS servers if we are connected
375  * to an NFS file.  This places the burden on the client rather than the
376  * server.
377  */
378 void
379 vndstart(vnd)
380 	register struct vnd_softc *vnd;
381 {
382 	register struct buf *bp;
383 
384 	/*
385 	 * Dequeue now since lower level strategy routine might
386 	 * queue using same links
387 	 */
388 	bp = vnd->sc_tab.b_actf;
389 	vnd->sc_tab.b_actf = bp->b_actf;
390 #ifdef DEBUG
391 	if (vnddebug & VDB_IO)
392 		printf("vndstart(%ld): bp %p vp %p blkno %x addr %p cnt %lx\n",
393 		    (long) (vnd-vnd_softc), bp, bp->b_vp, bp->b_blkno,
394 		    bp->b_data, bp->b_bcount);
395 #endif
396 
397 	/* Instrumentation. */
398 	disk_busy(&vnd->sc_dkdev);
399 
400 	if ((bp->b_flags & B_READ) == 0)
401 		bp->b_vp->v_numoutput++;
402 	VOP_STRATEGY(bp);
403 }
404 
405 void
406 vndiodone(bp)
407 	struct buf *bp;
408 {
409 	register struct vndbuf *vbp = (struct vndbuf *) bp;
410 	register struct buf *pbp = vbp->vb_obp;
411 	register struct vnd_softc *vnd = &vnd_softc[vndunit(pbp->b_dev)];
412 	int s;
413 
414 	s = splbio();
415 #ifdef DEBUG
416 	if (vnddebug & VDB_IO)
417 		printf("vndiodone(%ld): vbp %p vp %p blkno %x addr %p cnt %lx\n",
418 		    (long) (vnd-vnd_softc), vbp, vbp->vb_buf.b_vp,
419 		    vbp->vb_buf.b_blkno, vbp->vb_buf.b_data,
420 		    vbp->vb_buf.b_bcount);
421 #endif
422 
423 	if (vbp->vb_buf.b_error) {
424 #ifdef DEBUG
425 		if (vnddebug & VDB_IO)
426 			printf("vndiodone: vbp %p error %d\n", vbp,
427 			    vbp->vb_buf.b_error);
428 #endif
429 		pbp->b_flags |= B_ERROR;
430 		pbp->b_error = biowait(&vbp->vb_buf);
431 	}
432 	pbp->b_resid -= vbp->vb_buf.b_bcount;
433 	putvndbuf(vbp);
434 	disk_unbusy(&vnd->sc_dkdev, (pbp->b_bcount - pbp->b_resid));
435 	if (pbp->b_resid == 0) {
436 #ifdef DEBUG
437 		if (vnddebug & VDB_IO)
438 			printf("vndiodone: pbp %p iodone\n", pbp);
439 #endif
440 		biodone(pbp);
441 	}
442 	if (vnd->sc_tab.b_actf)
443 		vndstart(vnd);
444 	else
445 		vnd->sc_tab.b_active--;
446 	splx(s);
447 }
448 
449 /* ARGSUSED */
450 int
451 vndread(dev, uio, flags)
452 	dev_t dev;
453 	struct uio *uio;
454 	int flags;
455 {
456 	int unit = vndunit(dev);
457 	struct vnd_softc *sc;
458 
459 #ifdef DEBUG
460 	if (vnddebug & VDB_FOLLOW)
461 		printf("vndread(%x, %p)\n", dev, uio);
462 #endif
463 
464 	if (unit >= numvnd)
465 		return (ENXIO);
466 	sc = &vnd_softc[unit];
467 
468 	if ((sc->sc_flags & VNF_INITED) == 0)
469 		return (ENXIO);
470 
471 	return (physio(vndstrategy, NULL, dev, B_READ, minphys, uio));
472 }
473 
474 /* ARGSUSED */
475 int
476 vndwrite(dev, uio, flags)
477 	dev_t dev;
478 	struct uio *uio;
479 	int flags;
480 {
481 	int unit = vndunit(dev);
482 	struct vnd_softc *sc;
483 
484 #ifdef DEBUG
485 	if (vnddebug & VDB_FOLLOW)
486 		printf("vndwrite(%x, %p)\n", dev, uio);
487 #endif
488 
489 	if (unit >= numvnd)
490 		return (ENXIO);
491 	sc = &vnd_softc[unit];
492 
493 	if ((sc->sc_flags & VNF_INITED) == 0)
494 		return (ENXIO);
495 
496 	return (physio(vndstrategy, NULL, dev, B_WRITE, minphys, uio));
497 }
498 
499 /* ARGSUSED */
500 int
501 vndioctl(dev, cmd, data, flag, p)
502 	dev_t dev;
503 	u_long cmd;
504 	caddr_t data;
505 	int flag;
506 	struct proc *p;
507 {
508 	int unit = vndunit(dev);
509 	register struct vnd_softc *vnd;
510 	struct vnd_ioctl *vio;
511 	struct vattr vattr;
512 	struct nameidata nd;
513 	int error, part, pmask, s;
514 
515 #ifdef DEBUG
516 	if (vnddebug & VDB_FOLLOW)
517 		printf("vndioctl(%x, %lx, %p, %x, %p): unit %d\n",
518 		    dev, cmd, data, flag, p, unit);
519 #endif
520 	error = suser(p->p_ucred, &p->p_acflag);
521 	if (error)
522 		return (error);
523 	if (unit >= numvnd)
524 		return (ENXIO);
525 
526 	vnd = &vnd_softc[unit];
527 	vio = (struct vnd_ioctl *)data;
528 	switch (cmd) {
529 
530 	case VNDIOCSET:
531 		if (vnd->sc_flags & VNF_INITED)
532 			return (EBUSY);
533 
534 		if ((error = vndlock(vnd)) != 0)
535 			return (error);
536 
537 		/*
538 		 * Always open for read and write.
539 		 * This is probably bogus, but it lets vn_open()
540 		 * weed out directories, sockets, etc. so we don't
541 		 * have to worry about them.
542 		 */
543 		NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, vio->vnd_file, p);
544 		if ((error = vn_open(&nd, FREAD|FWRITE, 0)) != 0) {
545 			vndunlock(vnd);
546 			return(error);
547 		}
548 		error = VOP_GETATTR(nd.ni_vp, &vattr, p->p_ucred, p);
549 		if (error) {
550 			VOP_UNLOCK(nd.ni_vp);
551 			(void) vn_close(nd.ni_vp, FREAD|FWRITE, p->p_ucred, p);
552 			vndunlock(vnd);
553 			return(error);
554 		}
555 		VOP_UNLOCK(nd.ni_vp);
556 		vnd->sc_vp = nd.ni_vp;
557 		vnd->sc_size = btodb(vattr.va_size);	/* note truncation */
558 		if ((error = vndsetcred(vnd, p->p_ucred)) != 0) {
559 			(void) vn_close(nd.ni_vp, FREAD|FWRITE, p->p_ucred, p);
560 			vndunlock(vnd);
561 			return(error);
562 		}
563 		vndthrottle(vnd, vnd->sc_vp);
564 		vio->vnd_size = dbtob(vnd->sc_size);
565 		vnd->sc_flags |= VNF_INITED;
566 #ifdef DEBUG
567 		if (vnddebug & VDB_INIT)
568 			printf("vndioctl: SET vp %p size %lx\n",
569 			    vnd->sc_vp, (unsigned long) vnd->sc_size);
570 #endif
571 
572 		/* Attach the disk. */
573 		bzero(vnd->sc_xname, sizeof(vnd->sc_xname));	/* XXX */
574 		sprintf(vnd->sc_xname, "vnd%d", unit);		/* XXX */
575 		vnd->sc_dkdev.dk_name = vnd->sc_xname;
576 		disk_attach(&vnd->sc_dkdev);
577 
578 		vndunlock(vnd);
579 
580 		break;
581 
582 	case VNDIOCCLR:
583 		if ((vnd->sc_flags & VNF_INITED) == 0)
584 			return (ENXIO);
585 
586 		if ((error = vndlock(vnd)) != 0)
587 			return (error);
588 
589 		/*
590 		 * Don't unconfigure if any other partitions are open
591 		 * or if both the character and block flavors of this
592 		 * partition are open.
593 		 */
594 		part = DISKPART(dev);
595 		pmask = (1 << part);
596 		if ((vnd->sc_dkdev.dk_openmask & ~pmask) ||
597 		    ((vnd->sc_dkdev.dk_bopenmask & pmask) &&
598 		    (vnd->sc_dkdev.dk_copenmask & pmask))) {
599 			vndunlock(vnd);
600 			return (EBUSY);
601 		}
602 
603 		vndclear(vnd);
604 #ifdef DEBUG
605 		if (vnddebug & VDB_INIT)
606 			printf("vndioctl: CLRed\n");
607 #endif
608 
609 		/* Detatch the disk. */
610 		disk_detach(&vnd->sc_dkdev);
611 
612 		/* This must be atomic. */
613 		s = splhigh();
614 		vndunlock(vnd);
615 		bzero(vnd, sizeof(struct vnd_softc));
616 		splx(s);
617 
618 		break;
619 
620 	/*
621 	 * XXX Should support disklabels.
622 	 */
623 
624 	default:
625 		return(ENOTTY);
626 	}
627 
628 	return (0);
629 }
630 
631 /*
632  * Duplicate the current processes' credentials.  Since we are called only
633  * as the result of a SET ioctl and only root can do that, any future access
634  * to this "disk" is essentially as root.  Note that credentials may change
635  * if some other uid can write directly to the mapped file (NFS).
636  */
637 int
638 vndsetcred(vnd, cred)
639 	register struct vnd_softc *vnd;
640 	struct ucred *cred;
641 {
642 	struct uio auio;
643 	struct iovec aiov;
644 	char *tmpbuf;
645 	int error;
646 
647 	vnd->sc_cred = crdup(cred);
648 	tmpbuf = malloc(DEV_BSIZE, M_TEMP, M_WAITOK);
649 
650 	/* XXX: Horrible kludge to establish credentials for NFS */
651 	aiov.iov_base = tmpbuf;
652 	aiov.iov_len = min(DEV_BSIZE, dbtob(vnd->sc_size));
653 	auio.uio_iov = &aiov;
654 	auio.uio_iovcnt = 1;
655 	auio.uio_offset = 0;
656 	auio.uio_rw = UIO_READ;
657 	auio.uio_segflg = UIO_SYSSPACE;
658 	auio.uio_resid = aiov.iov_len;
659 	VOP_LOCK(vnd->sc_vp);
660 	error = VOP_READ(vnd->sc_vp, &auio, 0, vnd->sc_cred);
661 	VOP_UNLOCK(vnd->sc_vp);
662 
663 	free(tmpbuf, M_TEMP);
664 	return (error);
665 }
666 
667 /*
668  * Set maxactive based on FS type
669  */
670 void
671 vndthrottle(vnd, vp)
672 	register struct vnd_softc *vnd;
673 	struct vnode *vp;
674 {
675 #ifdef NFSCLIENT
676 	extern int (**nfsv2_vnodeop_p) __P((void *));
677 
678 	if (vp->v_op == nfsv2_vnodeop_p)
679 		vnd->sc_maxactive = 2;
680 	else
681 #endif
682 		vnd->sc_maxactive = 8;
683 
684 	if (vnd->sc_maxactive < 1)
685 		vnd->sc_maxactive = 1;
686 }
687 
688 void
689 vndshutdown()
690 {
691 	register struct vnd_softc *vnd;
692 
693 	for (vnd = &vnd_softc[0]; vnd < &vnd_softc[numvnd]; vnd++)
694 		if (vnd->sc_flags & VNF_INITED)
695 			vndclear(vnd);
696 }
697 
698 void
699 vndclear(vnd)
700 	register struct vnd_softc *vnd;
701 {
702 	register struct vnode *vp = vnd->sc_vp;
703 	struct proc *p = curproc;		/* XXX */
704 
705 #ifdef DEBUG
706 	if (vnddebug & VDB_FOLLOW)
707 		printf("vndclear(%p): vp %p\n", vnd, vp);
708 #endif
709 	vnd->sc_flags &= ~VNF_INITED;
710 	if (vp == (struct vnode *)0)
711 		panic("vndioctl: null vp");
712 	(void) vn_close(vp, FREAD|FWRITE, vnd->sc_cred, p);
713 	crfree(vnd->sc_cred);
714 	vnd->sc_vp = (struct vnode *)0;
715 	vnd->sc_cred = (struct ucred *)0;
716 	vnd->sc_size = 0;
717 }
718 
719 int
720 vndsize(dev)
721 	dev_t dev;
722 {
723 	int unit = vndunit(dev);
724 	register struct vnd_softc *vnd = &vnd_softc[unit];
725 
726 	if (unit >= numvnd || (vnd->sc_flags & VNF_INITED) == 0)
727 		return(-1);
728 	return(vnd->sc_size);
729 }
730 
731 int
732 vnddump(dev, blkno, va, size)
733 	dev_t dev;
734 	daddr_t blkno;
735 	caddr_t va;
736 	size_t size;
737 {
738 
739 	/* Not implemented. */
740 	return ENXIO;
741 }
742 
743 /*
744  * Wait interruptibly for an exclusive lock.
745  *
746  * XXX
747  * Several drivers do this; it should be abstracted and made MP-safe.
748  */
749 static int
750 vndlock(sc)
751 	struct vnd_softc *sc;
752 {
753 	int error;
754 
755 	while ((sc->sc_flags & VNF_LOCKED) != 0) {
756 		sc->sc_flags |= VNF_WANTED;
757 		if ((error = tsleep(sc, PRIBIO | PCATCH, "vndlck", 0)) != 0)
758 			return (error);
759 	}
760 	sc->sc_flags |= VNF_LOCKED;
761 	return (0);
762 }
763 
764 /*
765  * Unlock and wake up any waiters.
766  */
767 static void
768 vndunlock(sc)
769 	struct vnd_softc *sc;
770 {
771 
772 	sc->sc_flags &= ~VNF_LOCKED;
773 	if ((sc->sc_flags & VNF_WANTED) != 0) {
774 		sc->sc_flags &= ~VNF_WANTED;
775 		wakeup(sc);
776 	}
777 }
778