xref: /netbsd-src/sbin/fsck_ffs/setup.c (revision ae1bfcddc410612bc8c58b807e1830becb69a24c)
1 /*
2  * Copyright (c) 1980, 1986 The Regents of the University of California.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #ifndef lint
35 /*static char sccsid[] = "from: @(#)setup.c	5.33 (Berkeley) 2/22/91";*/
36 static char rcsid[] = "$Id: setup.c,v 1.9 1994/04/25 18:33:42 cgd Exp $";
37 #endif /* not lint */
38 
39 #define DKTYPENAMES
40 #include <sys/param.h>
41 #include <sys/time.h>
42 #include <ufs/dinode.h>
43 #include <ufs/fs.h>
44 #include <sys/stat.h>
45 #include <sys/ioctl.h>
46 #include <sys/disklabel.h>
47 #include <sys/file.h>
48 #include <sys/mount.h>
49 #include <errno.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #include <ctype.h>
53 #include "fsck.h"
54 
55 struct bufarea asblk;
56 #define altsblock (*asblk.b_un.b_fs)
57 #define POWEROF2(num)	(((num) & ((num) - 1)) == 0)
58 
59 /*
60  * The size of a cylinder group is calculated by CGSIZE. The maximum size
61  * is limited by the fact that cylinder groups are at most one block.
62  * Its size is derived from the size of the maps maintained in the
63  * cylinder group and the (struct cg) size.
64  */
65 #define CGSIZE(fs) \
66     /* base cg */	(sizeof(struct cg) + \
67     /* blktot size */	(fs)->fs_cpg * sizeof(long) + \
68     /* blks size */	(fs)->fs_cpg * (fs)->fs_nrpos * sizeof(short) + \
69     /* inode map */	howmany((fs)->fs_ipg, NBBY) + \
70     /* block map */	howmany((fs)->fs_cpg * (fs)->fs_spc / NSPF(fs), NBBY))
71 
72 char	*index();
73 struct	disklabel *getdisklabel();
74 char	*getmntdev();
75 
76 setup(dev)
77 	char *dev;
78 {
79 	long cg, size, asked, i, j;
80 	long bmapsize;
81 	struct disklabel *lp;
82 	struct stat statb, statb2;
83 	struct fs proto;
84 	char path2[MAXPATHLEN];
85 	char *dev2;
86 
87 	havesb = 0;
88 	if (stat(dev, &statb) < 0) {
89 		printf("Can't stat %s: %s\n", dev, strerror(errno));
90 		return (0);
91 	}
92 	switch (statb.st_mode & S_IFMT) {
93 	case S_IFCHR:
94 		break;
95 	case S_IFDIR:
96 		dev2 = getmntdev(dev);
97 		if (dev2 != NULL && !strncmp(dev2, "/dev/", 5)) {
98 			snprintf(path2, sizeof(path2), "/dev/r%s", dev2 + 5);
99 			if (stat(path2, &statb2) == 0 &&
100 			    (statb2.st_mode & S_IFMT) == S_IFCHR) {
101 				dev = path2;
102 				statb = statb2;
103 				break;
104 			}
105 		}
106 		pfatal("%s is not a character device", dev);
107 		if (reply("CONTINUE") == 0)
108 			return (0);
109 		break;
110 	case S_IFBLK:
111 		if (!strncmp(dev, "/dev/", 5)) {
112 			sprintf(path2, "/dev/r%s", dev + 5);
113 			if (stat(path2, &statb2) == 0 &&
114 			    (statb2.st_mode & S_IFMT) == S_IFCHR &&
115 			    minor(statb2.st_rdev) == minor(statb.st_rdev)) {
116 				dev = path2;
117 				statb = statb2;
118 				break;
119 			}
120 		}
121 		/* fall through */
122 	default:
123 		pfatal("%s is not a character device", dev);
124 		if (reply("CONTINUE") == 0)
125 			return (0);
126 	}
127 	if ((fsreadfd = open(dev, O_RDONLY)) < 0) {
128 		printf("Can't open %s: %s\n", dev, strerror(errno));
129 		return (0);
130 	}
131 	if (preen == 0)
132 		printf("** %s", dev);
133 	if (nflag || (fswritefd = open(dev, O_WRONLY)) < 0) {
134 		fswritefd = -1;
135 		if (preen)
136 			pfatal("NO WRITE ACCESS");
137 		printf(" (NO WRITE)");
138 	}
139 	if (preen == 0)
140 		printf("\n");
141 	fsmodified = 0;
142 	lfdir = 0;
143 	initbarea(&sblk);
144 	initbarea(&asblk);
145 	sblk.b_un.b_buf = malloc(SBSIZE);
146 	asblk.b_un.b_buf = malloc(SBSIZE);
147 	if (sblk.b_un.b_buf == NULL || asblk.b_un.b_buf == NULL)
148 		errexit("cannot allocate space for superblock\n");
149 	if (lp = getdisklabel((char *)NULL, fsreadfd))
150 		dev_bsize = secsize = lp->d_secsize;
151 	else
152 		dev_bsize = secsize = DEV_BSIZE;
153 #ifdef tahoe
154 	/*
155 	 * On the tahoe, the disk label and the disk driver disagree.
156 	 * The label knows that sectors are 512 bytes, but the disk
157 	 * drivers will only transfer in 1024 sized pieces.
158 	 */
159 	secsize = 1024;
160 #endif
161 	/*
162 	 * Read in the superblock, looking for alternates if necessary
163 	 */
164 	if (readsb(1) == 0) {
165 		if (bflag || preen || calcsb(dev, fsreadfd, &proto) == 0)
166 			return(0);
167 		if (reply("LOOK FOR ALTERNATE SUPERBLOCKS") == 0)
168 			return (0);
169 		for (cg = 0; cg < proto.fs_ncg; cg++) {
170 			bflag = fsbtodb(&proto, cgsblock(&proto, cg));
171 			if (readsb(0) != 0)
172 				break;
173 		}
174 		if (cg >= proto.fs_ncg) {
175 			printf("%s %s\n%s %s\n%s %s\n",
176 				"SEARCH FOR ALTERNATE SUPER-BLOCK",
177 				"FAILED. YOU MUST USE THE",
178 				"-b OPTION TO FSCK TO SPECIFY THE",
179 				"LOCATION OF AN ALTERNATE",
180 				"SUPER-BLOCK TO SUPPLY NEEDED",
181 				"INFORMATION; SEE fsck(8).");
182 			return(0);
183 		}
184 		pwarn("USING ALTERNATE SUPERBLOCK AT %d\n", bflag);
185 	}
186 	maxfsblock = sblock.fs_size;
187 	maxino = sblock.fs_ncg * sblock.fs_ipg;
188 	/*
189 	 * Check and potentially fix certain fields in the super block.
190 	 */
191 	if (sblock.fs_optim != FS_OPTTIME && sblock.fs_optim != FS_OPTSPACE) {
192 		pfatal("UNDEFINED OPTIMIZATION IN SUPERBLOCK");
193 		if (reply("SET TO DEFAULT") == 1) {
194 			sblock.fs_optim = FS_OPTTIME;
195 			sbdirty();
196 		}
197 	}
198 	if ((sblock.fs_minfree < 0 || sblock.fs_minfree > 99)) {
199 		pfatal("IMPOSSIBLE MINFREE=%d IN SUPERBLOCK",
200 			sblock.fs_minfree);
201 		if (reply("SET TO DEFAULT") == 1) {
202 			sblock.fs_minfree = 10;
203 			sbdirty();
204 		}
205 	}
206 	if (sblock.fs_interleave < 1 ||
207 	    sblock.fs_interleave > sblock.fs_nsect) {
208 		pwarn("IMPOSSIBLE INTERLEAVE=%d IN SUPERBLOCK",
209 			sblock.fs_interleave);
210 		sblock.fs_interleave = 1;
211 		if (preen)
212 			printf(" (FIXED)\n");
213 		if (preen || reply("SET TO DEFAULT") == 1) {
214 			sbdirty();
215 			dirty(&asblk);
216 		}
217 	}
218 	if (sblock.fs_npsect < sblock.fs_nsect ||
219 	    sblock.fs_npsect > sblock.fs_nsect*2) {
220 		pwarn("IMPOSSIBLE NPSECT=%d IN SUPERBLOCK",
221 			sblock.fs_npsect);
222 		sblock.fs_npsect = sblock.fs_nsect;
223 		if (preen)
224 			printf(" (FIXED)\n");
225 		if (preen || reply("SET TO DEFAULT") == 1) {
226 			sbdirty();
227 			dirty(&asblk);
228 		}
229 	}
230 	if (cvtflag) {
231 		if (sblock.fs_postblformat == FS_42POSTBLFMT) {
232 			/*
233 			 * Requested to convert from old format to new format
234 			 */
235 			if (preen)
236 				pwarn("CONVERTING TO NEW FILE SYSTEM FORMAT\n");
237 			else if (!reply("CONVERT TO NEW FILE SYSTEM FORMAT"))
238 				return(0);
239 			sblock.fs_postblformat = FS_DYNAMICPOSTBLFMT;
240 			sblock.fs_nrpos = 8;
241 			sblock.fs_postbloff =
242 			    (char *)(&sblock.fs_opostbl[0][0]) -
243 			    (char *)(&sblock.fs_link);
244 			sblock.fs_rotbloff = &sblock.fs_space[0] -
245 			    (u_char *)(&sblock.fs_link);
246 			sblock.fs_cgsize =
247 				fragroundup(&sblock, CGSIZE(&sblock));
248 			/*
249 			 * Planning now for future expansion.
250 			 */
251 #			if (BYTE_ORDER == BIG_ENDIAN)
252 				sblock.fs_qbmask.val[0] = 0;
253 				sblock.fs_qbmask.val[1] = ~sblock.fs_bmask;
254 				sblock.fs_qfmask.val[0] = 0;
255 				sblock.fs_qfmask.val[1] = ~sblock.fs_fmask;
256 #			endif /* BIG_ENDIAN */
257 #			if (BYTE_ORDER == LITTLE_ENDIAN)
258 				sblock.fs_qbmask.val[0] = ~sblock.fs_bmask;
259 				sblock.fs_qbmask.val[1] = 0;
260 				sblock.fs_qfmask.val[0] = ~sblock.fs_fmask;
261 				sblock.fs_qfmask.val[1] = 0;
262 #			endif /* LITTLE_ENDIAN */
263 			sbdirty();
264 			dirty(&asblk);
265 		} else if (sblock.fs_postblformat == FS_DYNAMICPOSTBLFMT) {
266 			/*
267 			 * Requested to convert from new format to old format
268 			 */
269 			if (sblock.fs_nrpos != 8 || sblock.fs_ipg > 2048 ||
270 			    sblock.fs_cpg > 32 || sblock.fs_cpc > 16) {
271 				printf(
272 				"PARAMETERS OF CURRENT FILE SYSTEM DO NOT\n\t");
273 				errexit(
274 				"ALLOW CONVERSION TO OLD FILE SYSTEM FORMAT\n");
275 			}
276 			if (preen)
277 				pwarn("CONVERTING TO OLD FILE SYSTEM FORMAT\n");
278 			else if (!reply("CONVERT TO OLD FILE SYSTEM FORMAT"))
279 				return(0);
280 			sblock.fs_postblformat = FS_42POSTBLFMT;
281 			sblock.fs_cgsize = fragroundup(&sblock,
282 			    sizeof(struct ocg) + howmany(sblock.fs_fpg, NBBY));
283 			sbdirty();
284 			dirty(&asblk);
285 		} else {
286 			errexit("UNKNOWN FILE SYSTEM FORMAT\n");
287 		}
288 	}
289 	if (asblk.b_dirty) {
290 		bcopy((char *)&sblock, (char *)&altsblock,
291 			(size_t)sblock.fs_sbsize);
292 		flush(fswritefd, &asblk);
293 	}
294 	/*
295 	 * read in the summary info.
296 	 */
297 	asked = 0;
298 	for (i = 0, j = 0; i < sblock.fs_cssize; i += sblock.fs_bsize, j++) {
299 		size = sblock.fs_cssize - i < sblock.fs_bsize ?
300 		    sblock.fs_cssize - i : sblock.fs_bsize;
301 		sblock.fs_csp[j] = (struct csum *)calloc(1, (unsigned)size);
302 		if (bread(fsreadfd, (char *)sblock.fs_csp[j],
303 		    fsbtodb(&sblock, sblock.fs_csaddr + j * sblock.fs_frag),
304 		    size) != 0 && !asked) {
305 			pfatal("BAD SUMMARY INFORMATION");
306 			if (reply("CONTINUE") == 0)
307 				errexit("");
308 			asked++;
309 		}
310 	}
311 	/*
312 	 * allocate and initialize the necessary maps
313 	 */
314 	bmapsize = roundup(howmany(maxfsblock, NBBY), sizeof(short));
315 	blockmap = calloc((unsigned)bmapsize, sizeof (char));
316 	if (blockmap == NULL) {
317 		printf("cannot alloc %u bytes for blockmap\n",
318 		    (unsigned)bmapsize);
319 		goto badsb;
320 	}
321 	statemap = calloc((unsigned)(maxino + 1), sizeof(char));
322 	if (statemap == NULL) {
323 		printf("cannot alloc %u bytes for statemap\n",
324 		    (unsigned)(maxino + 1));
325 		goto badsb;
326 	}
327 	lncntp = (short *)calloc((unsigned)(maxino + 1), sizeof(short));
328 	if (lncntp == NULL) {
329 		printf("cannot alloc %u bytes for lncntp\n",
330 		    (unsigned)(maxino + 1) * sizeof(short));
331 		goto badsb;
332 	}
333 	numdirs = sblock.fs_cstotal.cs_ndir;
334 	inplast = 0;
335 	listmax = numdirs + 10;
336 	inpsort = (struct inoinfo **)calloc((unsigned)listmax,
337 	    sizeof(struct inoinfo *));
338 	inphead = (struct inoinfo **)calloc((unsigned)numdirs,
339 	    sizeof(struct inoinfo *));
340 	if (inpsort == NULL || inphead == NULL) {
341 		printf("cannot alloc %u bytes for inphead\n",
342 		    (unsigned)numdirs * sizeof(struct inoinfo *));
343 		goto badsb;
344 	}
345 	bufinit();
346 	return (1);
347 
348 badsb:
349 	ckfini();
350 	return (0);
351 }
352 
353 /*
354  * Read in the super block and its summary info.
355  */
356 readsb(listerr)
357 	int listerr;
358 {
359 	daddr_t super = bflag ? bflag : SBOFF / dev_bsize;
360 
361 	if (bread(fsreadfd, (char *)&sblock, super, (long)SBSIZE) != 0)
362 		return (0);
363 	sblk.b_bno = super;
364 	sblk.b_size = SBSIZE;
365 	/*
366 	 * run a few consistency checks of the super block
367 	 */
368 	if (sblock.fs_magic != FS_MAGIC)
369 		{ badsb(listerr, "MAGIC NUMBER WRONG"); return (0); }
370 	if (sblock.fs_ncg < 1)
371 		{ badsb(listerr, "NCG OUT OF RANGE"); return (0); }
372 	if (sblock.fs_cpg < 1)
373 		{ badsb(listerr, "CPG OUT OF RANGE"); return (0); }
374 	if (sblock.fs_ncg * sblock.fs_cpg < sblock.fs_ncyl ||
375 	    (sblock.fs_ncg - 1) * sblock.fs_cpg >= sblock.fs_ncyl)
376 		{ badsb(listerr, "NCYL LESS THAN NCG*CPG"); return (0); }
377 	if (sblock.fs_sbsize > SBSIZE)
378 		{ badsb(listerr, "SIZE PREPOSTEROUSLY LARGE"); return (0); }
379 	/*
380 	 * Compute block size that the filesystem is based on,
381 	 * according to fsbtodb, and adjust superblock block number
382 	 * so we can tell if this is an alternate later.
383 	 */
384 	super *= dev_bsize;
385 	dev_bsize = sblock.fs_fsize / fsbtodb(&sblock, 1);
386 	sblk.b_bno = super / dev_bsize;
387 	/*
388 	 * Set all possible fields that could differ, then do check
389 	 * of whole super block against an alternate super block.
390 	 * When an alternate super-block is specified this check is skipped.
391 	 */
392 	getblk(&asblk, cgsblock(&sblock, sblock.fs_ncg - 1), sblock.fs_sbsize);
393 	if (asblk.b_errs)
394 		return (0);
395 	if (bflag) {
396 		havesb = 1;
397 		return (1);
398 	}
399 	altsblock.fs_link = sblock.fs_link;
400 	altsblock.fs_rlink = sblock.fs_rlink;
401 	altsblock.fs_time = sblock.fs_time;
402 	altsblock.fs_cstotal = sblock.fs_cstotal;
403 	altsblock.fs_cgrotor = sblock.fs_cgrotor;
404 	altsblock.fs_fmod = sblock.fs_fmod;
405 	altsblock.fs_clean = sblock.fs_clean;
406 	altsblock.fs_state = sblock.fs_state;
407 	altsblock.fs_ronly = sblock.fs_ronly;
408 	altsblock.fs_flags = sblock.fs_flags;
409 	altsblock.fs_maxcontig = sblock.fs_maxcontig;
410 	altsblock.fs_minfree = sblock.fs_minfree;
411 	altsblock.fs_optim = sblock.fs_optim;
412 	altsblock.fs_rotdelay = sblock.fs_rotdelay;
413 	altsblock.fs_maxbpg = sblock.fs_maxbpg;
414 	bcopy((char *)sblock.fs_csp, (char *)altsblock.fs_csp,
415 		sizeof sblock.fs_csp);
416 	bcopy((char *)sblock.fs_fsmnt, (char *)altsblock.fs_fsmnt,
417 		sizeof sblock.fs_fsmnt);
418 	bcopy((char *)sblock.fs_sparecon, (char *)altsblock.fs_sparecon,
419 		sizeof sblock.fs_sparecon);
420 	/*
421 	 * The following should not have to be copied.
422 	 */
423 	altsblock.fs_fsbtodb = sblock.fs_fsbtodb;
424 	altsblock.fs_interleave = sblock.fs_interleave;
425 	altsblock.fs_npsect = sblock.fs_npsect;
426 	altsblock.fs_nrpos = sblock.fs_nrpos;
427 	if (bcmp((char *)&sblock, (char *)&altsblock, (int)sblock.fs_sbsize)) {
428 		badsb(listerr,
429 		"VALUES IN SUPER BLOCK DISAGREE WITH THOSE IN FIRST ALTERNATE");
430 		return (0);
431 	}
432 	havesb = 1;
433 	return (1);
434 }
435 
436 badsb(listerr, s)
437 	int listerr;
438 	char *s;
439 {
440 
441 	if (!listerr)
442 		return;
443 	if (preen)
444 		printf("%s: ", devname);
445 	pfatal("BAD SUPER BLOCK: %s\n", s);
446 }
447 
448 /*
449  * Calculate a prototype superblock based on information in the disk label.
450  * When done the cgsblock macro can be calculated and the fs_ncg field
451  * can be used. Do NOT attempt to use other macros without verifying that
452  * their needed information is available!
453  */
454 calcsb(dev, devfd, fs)
455 	char *dev;
456 	int devfd;
457 	register struct fs *fs;
458 {
459 	register struct disklabel *lp;
460 	register struct partition *pp;
461 	register char *cp;
462 	int i;
463 
464 	cp = index(dev, '\0') - 1;
465 	if (cp == (char *)-1 || (*cp < 'a' || *cp > 'h') && !isdigit(*cp)) {
466 		pfatal("%s: CANNOT FIGURE OUT FILE SYSTEM PARTITION\n", dev);
467 		return (0);
468 	}
469 	lp = getdisklabel(dev, devfd);
470 	if (isdigit(*cp))
471 		pp = &lp->d_partitions[0];
472 	else
473 		pp = &lp->d_partitions[*cp - 'a'];
474 	if (pp->p_fstype != FS_BSDFFS) {
475 		pfatal("%s: NOT LABELED AS A BSD FILE SYSTEM (%s)\n",
476 			dev, pp->p_fstype < FSMAXTYPES ?
477 			fstypenames[pp->p_fstype] : "unknown");
478 		return (0);
479 	}
480 	bzero((char *)fs, sizeof(struct fs));
481 	fs->fs_fsize = pp->p_fsize;
482 	fs->fs_frag = pp->p_frag;
483 	fs->fs_cpg = pp->p_cpg;
484 	fs->fs_size = pp->p_size;
485 	fs->fs_ntrak = lp->d_ntracks;
486 	fs->fs_nsect = lp->d_nsectors;
487 	fs->fs_spc = lp->d_secpercyl;
488 	fs->fs_nspf = fs->fs_fsize / lp->d_secsize;
489 	fs->fs_sblkno = roundup(
490 		howmany(lp->d_bbsize + lp->d_sbsize, fs->fs_fsize),
491 		fs->fs_frag);
492 	fs->fs_cgmask = 0xffffffff;
493 	for (i = fs->fs_ntrak; i > 1; i >>= 1)
494 		fs->fs_cgmask <<= 1;
495 	if (!POWEROF2(fs->fs_ntrak))
496 		fs->fs_cgmask <<= 1;
497 	fs->fs_cgoffset = roundup(
498 		howmany(fs->fs_nsect, NSPF(fs)), fs->fs_frag);
499 	fs->fs_fpg = (fs->fs_cpg * fs->fs_spc) / NSPF(fs);
500 	fs->fs_ncg = howmany(fs->fs_size / fs->fs_spc, fs->fs_cpg);
501 	for (fs->fs_fsbtodb = 0, i = NSPF(fs); i > 1; i >>= 1)
502 		fs->fs_fsbtodb++;
503 	dev_bsize = lp->d_secsize;
504 	return (1);
505 }
506 
507 struct disklabel *
508 getdisklabel(s, fd)
509 	char *s;
510 	int	fd;
511 {
512 	static struct disklabel lab;
513 
514 	if (ioctl(fd, DIOCGDINFO, (char *)&lab) < 0) {
515 		if (s == NULL)
516 			return ((struct disklabel *)NULL);
517 		pwarn("ioctl (GCINFO): %s\n", strerror(errno));
518 		errexit("%s: can't read disk label\n", s);
519 	}
520 	return (&lab);
521 }
522 
523 char *
524 getmntdev(name)
525 	char *name;
526 {
527 	long mntsize;
528 	register long i;
529 	struct statfs *mntbuf;
530 
531 	mntsize = getmntinfo(&mntbuf, MNT_NOWAIT);
532 	for (i = 0; i < mntsize; i++) {
533 		if (!strncmp(mntbuf[i].f_fstypename, MOUNT_UFS, MFSNAMELEN) &&
534 		    !strcmp(mntbuf[i].f_mntonname, name))
535 			return (mntbuf[i].f_mntfromname);
536 	}
537 	return ((char *)0);
538 }
539