fat.c revision 268629 
1/*
2 * Copyright (C) 1995, 1996, 1997 Wolfgang Solfrank
3 * Copyright (c) 1995 Martin Husemann
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 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26
27#include <sys/cdefs.h>
28#ifndef lint
29__RCSID("$NetBSD: fat.c,v 1.18 2006/06/05 16:51:18 christos Exp $");
30static const char rcsid[] =
31  "$FreeBSD: stable/10/sbin/fsck_msdosfs/fat.c 268629 2014-07-14 20:07:23Z pfg $";
32#endif /* not lint */
33
34#include <stdlib.h>
35#include <string.h>
36#include <ctype.h>
37#include <stdio.h>
38#include <unistd.h>
39
40#include "ext.h"
41#include "fsutil.h"
42
43static int checkclnum(struct bootblock *, u_int, cl_t, cl_t *);
44static int clustdiffer(cl_t, cl_t *, cl_t *, u_int);
45static int tryclear(struct bootblock *, struct fatEntry *, cl_t, cl_t *);
46static int _readfat(int, struct bootblock *, u_int, u_char **);
47
48/*-
49 * The first 2 FAT entries contain pseudo-cluster numbers with the following
50 * layout:
51 *
52 * 31...... ........ ........ .......0
53 * rrrr1111 11111111 11111111 mmmmmmmm         FAT32 entry 0
54 * rrrrsh11 11111111 11111111 11111xxx         FAT32 entry 1
55 *
56 *                   11111111 mmmmmmmm         FAT16 entry 0
57 *                   sh111111 11111xxx         FAT16 entry 1
58 *
59 * r = reserved
60 * m = BPB media ID byte
61 * s = clean flag (1 = dismounted; 0 = still mounted)
62 * h = hard error flag (1 = ok; 0 = I/O error)
63 * x = any value ok
64 */
65
66int
67checkdirty(int fs, struct bootblock *boot)
68{
69	off_t off;
70	u_char *buffer;
71	int ret = 0;
72	size_t len;
73
74	if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
75		return 0;
76
77	off = boot->bpbResSectors;
78	off *= boot->bpbBytesPerSec;
79
80	buffer = malloc(len = boot->bpbBytesPerSec);
81	if (buffer == NULL) {
82		perr("No space for FAT sectors (%zu)", len);
83		return 1;
84	}
85
86	if (lseek(fs, off, SEEK_SET) != off) {
87		perr("Unable to read FAT");
88		goto err;
89	}
90
91	if ((size_t)read(fs, buffer, boot->bpbBytesPerSec) !=
92	    boot->bpbBytesPerSec) {
93		perr("Unable to read FAT");
94		goto err;
95	}
96
97	/*
98	 * If we don't understand the FAT, then the file system must be
99	 * assumed to be unclean.
100	 */
101	if (buffer[0] != boot->bpbMedia || buffer[1] != 0xff)
102		goto err;
103	if (boot->ClustMask == CLUST16_MASK) {
104		if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f)
105			goto err;
106	} else {
107		if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f
108		    || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff
109		    || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03)
110			goto err;
111	}
112
113	/*
114	 * Now check the actual clean flag (and the no-error flag).
115	 */
116	if (boot->ClustMask == CLUST16_MASK) {
117		if ((buffer[3] & 0xc0) == 0xc0)
118			ret = 1;
119	} else {
120		if ((buffer[7] & 0x0c) == 0x0c)
121			ret = 1;
122	}
123
124err:
125	free(buffer);
126	return ret;
127}
128
129/*
130 * Check a cluster number for valid value
131 */
132static int
133checkclnum(struct bootblock *boot, u_int fat, cl_t cl, cl_t *next)
134{
135	if (*next >= (CLUST_RSRVD&boot->ClustMask))
136		*next |= ~boot->ClustMask;
137	if (*next == CLUST_FREE) {
138		boot->NumFree++;
139		return FSOK;
140	}
141	if (*next == CLUST_BAD) {
142		boot->NumBad++;
143		return FSOK;
144	}
145	if (*next < CLUST_FIRST
146	    || (*next >= boot->NumClusters && *next < CLUST_EOFS)) {
147		pwarn("Cluster %u in FAT %d continues with %s cluster number %u\n",
148		      cl, fat,
149		      *next < CLUST_RSRVD ? "out of range" : "reserved",
150		      *next&boot->ClustMask);
151		if (ask(0, "Truncate")) {
152			*next = CLUST_EOF;
153			return FSFATMOD;
154		}
155		return FSERROR;
156	}
157	return FSOK;
158}
159
160/*
161 * Read a FAT from disk. Returns 1 if successful, 0 otherwise.
162 */
163static int
164_readfat(int fs, struct bootblock *boot, u_int no, u_char **buffer)
165{
166	off_t off;
167	size_t len;
168
169	*buffer = malloc(len = boot->FATsecs * boot->bpbBytesPerSec);
170	if (*buffer == NULL) {
171		perr("No space for FAT sectors (%zu)", len);
172		return 0;
173	}
174
175	off = boot->bpbResSectors + no * boot->FATsecs;
176	off *= boot->bpbBytesPerSec;
177
178	if (lseek(fs, off, SEEK_SET) != off) {
179		perr("Unable to read FAT");
180		goto err;
181	}
182
183	if ((size_t)read(fs, *buffer, boot->FATsecs * boot->bpbBytesPerSec)
184	    != boot->FATsecs * boot->bpbBytesPerSec) {
185		perr("Unable to read FAT");
186		goto err;
187	}
188
189	return 1;
190
191    err:
192	free(*buffer);
193	return 0;
194}
195
196/*
197 * Read a FAT and decode it into internal format
198 */
199int
200readfat(int fs, struct bootblock *boot, u_int no, struct fatEntry **fp)
201{
202	struct fatEntry *fat;
203	u_char *buffer, *p;
204	cl_t cl;
205	int ret = FSOK;
206	size_t len;
207
208	boot->NumFree = boot->NumBad = 0;
209
210	if (!_readfat(fs, boot, no, &buffer))
211		return FSFATAL;
212
213	fat = malloc(len = boot->NumClusters * sizeof(struct fatEntry));
214	if (fat == NULL) {
215		perr("No space for FAT clusters (%zu)", len);
216		free(buffer);
217		return FSFATAL;
218	}
219	(void)memset(fat, 0, len);
220
221	if (buffer[0] != boot->bpbMedia
222	    || buffer[1] != 0xff || buffer[2] != 0xff
223	    || (boot->ClustMask == CLUST16_MASK && buffer[3] != 0xff)
224	    || (boot->ClustMask == CLUST32_MASK
225		&& ((buffer[3]&0x0f) != 0x0f
226		    || buffer[4] != 0xff || buffer[5] != 0xff
227		    || buffer[6] != 0xff || (buffer[7]&0x0f) != 0x0f))) {
228
229		/* Windows 95 OSR2 (and possibly any later) changes
230		 * the FAT signature to 0xXXffff7f for FAT16 and to
231		 * 0xXXffff0fffffff07 for FAT32 upon boot, to know that the
232		 * file system is dirty if it doesn't reboot cleanly.
233		 * Check this special condition before errorring out.
234		 */
235		if (buffer[0] == boot->bpbMedia && buffer[1] == 0xff
236		    && buffer[2] == 0xff
237		    && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f)
238			|| (boot->ClustMask == CLUST32_MASK
239			    && buffer[3] == 0x0f && buffer[4] == 0xff
240			    && buffer[5] == 0xff && buffer[6] == 0xff
241			    && buffer[7] == 0x07)))
242			ret |= FSDIRTY;
243		else {
244			/* just some odd byte sequence in FAT */
245
246			switch (boot->ClustMask) {
247			case CLUST32_MASK:
248				pwarn("%s (%02x%02x%02x%02x%02x%02x%02x%02x)\n",
249				      "FAT starts with odd byte sequence",
250				      buffer[0], buffer[1], buffer[2], buffer[3],
251				      buffer[4], buffer[5], buffer[6], buffer[7]);
252				break;
253			case CLUST16_MASK:
254				pwarn("%s (%02x%02x%02x%02x)\n",
255				    "FAT starts with odd byte sequence",
256				    buffer[0], buffer[1], buffer[2], buffer[3]);
257				break;
258			default:
259				pwarn("%s (%02x%02x%02x)\n",
260				    "FAT starts with odd byte sequence",
261				    buffer[0], buffer[1], buffer[2]);
262				break;
263			}
264
265
266			if (ask(1, "Correct"))
267				ret |= FSFIXFAT;
268		}
269	}
270	switch (boot->ClustMask) {
271	case CLUST32_MASK:
272		p = buffer + 8;
273		break;
274	case CLUST16_MASK:
275		p = buffer + 4;
276		break;
277	default:
278		p = buffer + 3;
279		break;
280	}
281	for (cl = CLUST_FIRST; cl < boot->NumClusters;) {
282		switch (boot->ClustMask) {
283		case CLUST32_MASK:
284			fat[cl].next = p[0] + (p[1] << 8)
285				       + (p[2] << 16) + (p[3] << 24);
286			fat[cl].next &= boot->ClustMask;
287			ret |= checkclnum(boot, no, cl, &fat[cl].next);
288			cl++;
289			p += 4;
290			break;
291		case CLUST16_MASK:
292			fat[cl].next = p[0] + (p[1] << 8);
293			ret |= checkclnum(boot, no, cl, &fat[cl].next);
294			cl++;
295			p += 2;
296			break;
297		default:
298			fat[cl].next = (p[0] + (p[1] << 8)) & 0x0fff;
299			ret |= checkclnum(boot, no, cl, &fat[cl].next);
300			cl++;
301			if (cl >= boot->NumClusters)
302				break;
303			fat[cl].next = ((p[1] >> 4) + (p[2] << 4)) & 0x0fff;
304			ret |= checkclnum(boot, no, cl, &fat[cl].next);
305			cl++;
306			p += 3;
307			break;
308		}
309	}
310
311	free(buffer);
312	if (ret & FSFATAL) {
313		free(fat);
314		*fp = NULL;
315	} else
316		*fp = fat;
317	return ret;
318}
319
320/*
321 * Get type of reserved cluster
322 */
323const char *
324rsrvdcltype(cl_t cl)
325{
326	if (cl == CLUST_FREE)
327		return "free";
328	if (cl < CLUST_BAD)
329		return "reserved";
330	if (cl > CLUST_BAD)
331		return "as EOF";
332	return "bad";
333}
334
335static int
336clustdiffer(cl_t cl, cl_t *cp1, cl_t *cp2, u_int fatnum)
337{
338	if (*cp1 == CLUST_FREE || *cp1 >= CLUST_RSRVD) {
339		if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
340			if ((*cp1 != CLUST_FREE && *cp1 < CLUST_BAD
341			     && *cp2 != CLUST_FREE && *cp2 < CLUST_BAD)
342			    || (*cp1 > CLUST_BAD && *cp2 > CLUST_BAD)) {
343				pwarn("Cluster %u is marked %s with different indicators\n",
344				      cl, rsrvdcltype(*cp1));
345				if (ask(1, "Fix")) {
346					*cp2 = *cp1;
347					return FSFATMOD;
348				}
349				return FSFATAL;
350			}
351			pwarn("Cluster %u is marked %s in FAT 0, %s in FAT %u\n",
352			      cl, rsrvdcltype(*cp1), rsrvdcltype(*cp2), fatnum);
353			if (ask(0, "Use FAT 0's entry")) {
354				*cp2 = *cp1;
355				return FSFATMOD;
356			}
357			if (ask(0, "Use FAT %u's entry", fatnum)) {
358				*cp1 = *cp2;
359				return FSFATMOD;
360			}
361			return FSFATAL;
362		}
363		pwarn("Cluster %u is marked %s in FAT 0, but continues with cluster %u in FAT %d\n",
364		      cl, rsrvdcltype(*cp1), *cp2, fatnum);
365		if (ask(0, "Use continuation from FAT %u", fatnum)) {
366			*cp1 = *cp2;
367			return FSFATMOD;
368		}
369		if (ask(0, "Use mark from FAT 0")) {
370			*cp2 = *cp1;
371			return FSFATMOD;
372		}
373		return FSFATAL;
374	}
375	if (*cp2 == CLUST_FREE || *cp2 >= CLUST_RSRVD) {
376		pwarn("Cluster %u continues with cluster %u in FAT 0, but is marked %s in FAT %u\n",
377		      cl, *cp1, rsrvdcltype(*cp2), fatnum);
378		if (ask(0, "Use continuation from FAT 0")) {
379			*cp2 = *cp1;
380			return FSFATMOD;
381		}
382		if (ask(0, "Use mark from FAT %d", fatnum)) {
383			*cp1 = *cp2;
384			return FSFATMOD;
385		}
386		return FSERROR;
387	}
388	pwarn("Cluster %u continues with cluster %u in FAT 0, but with cluster %u in FAT %u\n",
389	      cl, *cp1, *cp2, fatnum);
390	if (ask(0, "Use continuation from FAT 0")) {
391		*cp2 = *cp1;
392		return FSFATMOD;
393	}
394	if (ask(0, "Use continuation from FAT %u", fatnum)) {
395		*cp1 = *cp2;
396		return FSFATMOD;
397	}
398	return FSERROR;
399}
400
401/*
402 * Compare two FAT copies in memory. Resolve any conflicts and merge them
403 * into the first one.
404 */
405int
406comparefat(struct bootblock *boot, struct fatEntry *first,
407    struct fatEntry *second, u_int fatnum)
408{
409	cl_t cl;
410	int ret = FSOK;
411
412	for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++)
413		if (first[cl].next != second[cl].next)
414			ret |= clustdiffer(cl, &first[cl].next, &second[cl].next, fatnum);
415	return ret;
416}
417
418void
419clearchain(struct bootblock *boot, struct fatEntry *fat, cl_t head)
420{
421	cl_t p, q;
422
423	for (p = head; p >= CLUST_FIRST && p < boot->NumClusters; p = q) {
424		if (fat[p].head != head)
425			break;
426		q = fat[p].next;
427		fat[p].next = fat[p].head = CLUST_FREE;
428		fat[p].length = 0;
429	}
430}
431
432int
433tryclear(struct bootblock *boot, struct fatEntry *fat, cl_t head, cl_t *truncp)
434{
435	if (ask(0, "Clear chain starting at %u", head)) {
436		clearchain(boot, fat, head);
437		return FSFATMOD;
438	} else if (ask(0, "Truncate")) {
439		*truncp = CLUST_EOF;
440		return FSFATMOD;
441	} else
442		return FSERROR;
443}
444
445/*
446 * Check a complete FAT in-memory for crosslinks
447 */
448int
449checkfat(struct bootblock *boot, struct fatEntry *fat)
450{
451	cl_t head, p, h, n;
452	u_int len;
453	int ret = 0;
454	int conf;
455
456	/*
457	 * pass 1: figure out the cluster chains.
458	 */
459	for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
460		/* find next untravelled chain */
461		if (fat[head].head != 0		/* cluster already belongs to some chain */
462		    || fat[head].next == CLUST_FREE
463		    || fat[head].next == CLUST_BAD)
464			continue;		/* skip it. */
465
466		/* follow the chain and mark all clusters on the way */
467		for (len = 0, p = head;
468		     p >= CLUST_FIRST && p < boot->NumClusters;
469		     p = fat[p].next) {
470			fat[p].head = head;
471			len++;
472		}
473
474		/* the head record gets the length */
475		fat[head].length = fat[head].next == CLUST_FREE ? 0 : len;
476	}
477
478	/*
479	 * pass 2: check for crosslinked chains (we couldn't do this in pass 1 because
480	 * we didn't know the real start of the chain then - would have treated partial
481	 * chains as interlinked with their main chain)
482	 */
483	for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
484		/* find next untravelled chain */
485		if (fat[head].head != head)
486			continue;
487
488		/* follow the chain to its end (hopefully) */
489		for (p = head;
490		     (n = fat[p].next) >= CLUST_FIRST && n < boot->NumClusters;
491		     p = n)
492			if (fat[n].head != head)
493				break;
494		if (n >= CLUST_EOFS)
495			continue;
496
497		if (n == CLUST_FREE || n >= CLUST_RSRVD) {
498			pwarn("Cluster chain starting at %u ends with cluster marked %s\n",
499			      head, rsrvdcltype(n));
500			ret |= tryclear(boot, fat, head, &fat[p].next);
501			continue;
502		}
503		if (n < CLUST_FIRST || n >= boot->NumClusters) {
504			pwarn("Cluster chain starting at %u ends with cluster out of range (%u)\n",
505			      head, n);
506			ret |= tryclear(boot, fat, head, &fat[p].next);
507			continue;
508		}
509		pwarn("Cluster chains starting at %u and %u are linked at cluster %u\n",
510		      head, fat[n].head, n);
511		conf = tryclear(boot, fat, head, &fat[p].next);
512		if (ask(0, "Clear chain starting at %u", h = fat[n].head)) {
513			if (conf == FSERROR) {
514				/*
515				 * Transfer the common chain to the one not cleared above.
516				 */
517				for (p = n;
518				     p >= CLUST_FIRST && p < boot->NumClusters;
519				     p = fat[p].next) {
520					if (h != fat[p].head) {
521						/*
522						 * Have to reexamine this chain.
523						 */
524						head--;
525						break;
526					}
527					fat[p].head = head;
528				}
529			}
530			clearchain(boot, fat, h);
531			conf |= FSFATMOD;
532		}
533		ret |= conf;
534	}
535
536	return ret;
537}
538
539/*
540 * Write out FATs encoding them from the internal format
541 */
542int
543writefat(int fs, struct bootblock *boot, struct fatEntry *fat, int correct_fat)
544{
545	u_char *buffer, *p;
546	cl_t cl;
547	u_int i;
548	size_t fatsz;
549	off_t off;
550	int ret = FSOK;
551
552	buffer = malloc(fatsz = boot->FATsecs * boot->bpbBytesPerSec);
553	if (buffer == NULL) {
554		perr("No space for FAT sectors (%zu)", fatsz);
555		return FSFATAL;
556	}
557	memset(buffer, 0, fatsz);
558	boot->NumFree = 0;
559	p = buffer;
560	if (correct_fat) {
561		*p++ = (u_char)boot->bpbMedia;
562		*p++ = 0xff;
563		*p++ = 0xff;
564		switch (boot->ClustMask) {
565		case CLUST16_MASK:
566			*p++ = 0xff;
567			break;
568		case CLUST32_MASK:
569			*p++ = 0x0f;
570			*p++ = 0xff;
571			*p++ = 0xff;
572			*p++ = 0xff;
573			*p++ = 0x0f;
574			break;
575		}
576	} else {
577		/* use same FAT signature as the old FAT has */
578		int count;
579		u_char *old_fat;
580
581		switch (boot->ClustMask) {
582		case CLUST32_MASK:
583			count = 8;
584			break;
585		case CLUST16_MASK:
586			count = 4;
587			break;
588		default:
589			count = 3;
590			break;
591		}
592
593		if (!_readfat(fs, boot, boot->ValidFat >= 0 ? boot->ValidFat :0,
594					 &old_fat)) {
595			free(buffer);
596			return FSFATAL;
597		}
598
599		memcpy(p, old_fat, count);
600		free(old_fat);
601		p += count;
602	}
603
604	for (cl = CLUST_FIRST; cl < boot->NumClusters; cl++) {
605		switch (boot->ClustMask) {
606		case CLUST32_MASK:
607			if (fat[cl].next == CLUST_FREE)
608				boot->NumFree++;
609			*p++ = (u_char)fat[cl].next;
610			*p++ = (u_char)(fat[cl].next >> 8);
611			*p++ = (u_char)(fat[cl].next >> 16);
612			*p &= 0xf0;
613			*p++ |= (fat[cl].next >> 24)&0x0f;
614			break;
615		case CLUST16_MASK:
616			if (fat[cl].next == CLUST_FREE)
617				boot->NumFree++;
618			*p++ = (u_char)fat[cl].next;
619			*p++ = (u_char)(fat[cl].next >> 8);
620			break;
621		default:
622			if (fat[cl].next == CLUST_FREE)
623				boot->NumFree++;
624			if (cl + 1 < boot->NumClusters
625			    && fat[cl + 1].next == CLUST_FREE)
626				boot->NumFree++;
627			*p++ = (u_char)fat[cl].next;
628			*p++ = (u_char)((fat[cl].next >> 8) & 0xf)
629			       |(u_char)(fat[cl+1].next << 4);
630			*p++ = (u_char)(fat[++cl].next >> 4);
631			break;
632		}
633	}
634	for (i = 0; i < boot->bpbFATs; i++) {
635		off = boot->bpbResSectors + i * boot->FATsecs;
636		off *= boot->bpbBytesPerSec;
637		if (lseek(fs, off, SEEK_SET) != off
638		    || (size_t)write(fs, buffer, fatsz) != fatsz) {
639			perr("Unable to write FAT");
640			ret = FSFATAL; /* Return immediately?		XXX */
641		}
642	}
643	free(buffer);
644	return ret;
645}
646
647/*
648 * Check a complete in-memory FAT for lost cluster chains
649 */
650int
651checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
652{
653	cl_t head;
654	int mod = FSOK;
655	int ret;
656
657	for (head = CLUST_FIRST; head < boot->NumClusters; head++) {
658		/* find next untravelled chain */
659		if (fat[head].head != head
660		    || fat[head].next == CLUST_FREE
661		    || (fat[head].next >= CLUST_RSRVD
662			&& fat[head].next < CLUST_EOFS)
663		    || (fat[head].flags & FAT_USED))
664			continue;
665
666		pwarn("Lost cluster chain at cluster %u\n%d Cluster(s) lost\n",
667		      head, fat[head].length);
668		mod |= ret = reconnect(dosfs, boot, fat, head);
669		if (mod & FSFATAL)
670			break;
671		if (ret == FSERROR && ask(0, "Clear")) {
672			clearchain(boot, fat, head);
673			mod |= FSFATMOD;
674		}
675	}
676	finishlf();
677
678	if (boot->bpbFSInfo) {
679		ret = 0;
680		if (boot->FSFree != 0xffffffffU &&
681		    boot->FSFree != boot->NumFree) {
682			pwarn("Free space in FSInfo block (%u) not correct (%u)\n",
683			      boot->FSFree, boot->NumFree);
684			if (ask(1, "Fix")) {
685				boot->FSFree = boot->NumFree;
686				ret = 1;
687			}
688		}
689		if (ret)
690			mod |= writefsinfo(dosfs, boot);
691	}
692
693	return mod;
694}
695