xref: /openbsd-src/sbin/fsck_ext2fs/setup.c (revision 8445c53715e7030056b779e8ab40efb7820981f2)
1 /*	$OpenBSD: setup.c,v 1.7 2001/09/18 17:43:15 art Exp $	*/
2 /*	$NetBSD: setup.c,v 1.1 1997/06/11 11:22:01 bouyer Exp $	*/
3 
4 /*
5  * Copyright (c) 1997 Manuel Bouyer.
6  * Copyright (c) 1980, 1986, 1993
7  *	The Regents of the University of California.  All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *	notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *	notice, this list of conditions and the following disclaimer in the
16  *	documentation and/or other materials provided with the distribution.
17  * 3. All advertising materials mentioning features or use of this software
18  *	must display the following acknowledgement:
19  *	This product includes software developed by the University of
20  *	California, Berkeley and its contributors.
21  * 4. Neither the name of the University nor the names of its contributors
22  *	may be used to endorse or promote products derived from this software
23  *	without specific prior written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35  * SUCH DAMAGE.
36  */
37 
38 #define DKTYPENAMES
39 #include <sys/param.h>
40 #include <sys/time.h>
41 #include <ufs/ext2fs/ext2fs_dinode.h>
42 #include <ufs/ext2fs/ext2fs.h>
43 #include <sys/stat.h>
44 #include <sys/ioctl.h>
45 #include <sys/disklabel.h>
46 #include <sys/file.h>
47 
48 #include <errno.h>
49 #include <fcntl.h>
50 #include <stdio.h>
51 #include <stdlib.h>
52 #include <string.h>
53 #include <ctype.h>
54 
55 #include "fsck.h"
56 #include "extern.h"
57 #include "fsutil.h"
58 
59 #define POWEROF2(num)	(((num) & ((num) - 1)) == 0)
60 
61 void badsb __P((int, char *));
62 int calcsb __P((char *, int, struct m_ext2fs *));
63 static struct disklabel *getdisklabel __P((char *, int));
64 static int readsb __P((int));
65 
66 int
67 setup(dev)
68 	char *dev;
69 {
70 	long cg, asked, i;
71 	long bmapsize;
72 	struct disklabel *lp;
73 	off_t sizepb;
74 	struct stat statb;
75 	struct m_ext2fs proto;
76 	int doskipclean;
77 	u_int64_t maxfilesize;
78 
79 	havesb = 0;
80 	fswritefd = -1;
81 	doskipclean = skipclean;
82 	if (stat(dev, &statb) < 0) {
83 		printf("Can't stat %s: %s\n", dev, strerror(errno));
84 		return (0);
85 	}
86 	if (!S_ISCHR(statb.st_mode)) {
87 		pfatal("%s is not a character device", dev);
88 		if (reply("CONTINUE") == 0)
89 			return (0);
90 	}
91 	if ((fsreadfd = open(dev, O_RDONLY)) < 0) {
92 		printf("Can't open %s: %s\n", dev, strerror(errno));
93 		return (0);
94 	}
95 	if (preen == 0)
96 		printf("** %s", dev);
97 	if (nflag || (fswritefd = open(dev, O_WRONLY)) < 0) {
98 		fswritefd = -1;
99 		if (preen)
100 			pfatal("NO WRITE ACCESS");
101 		printf(" (NO WRITE)");
102 	}
103 	if (preen == 0)
104 		printf("\n");
105 	fsmodified = 0;
106 	lfdir = 0;
107 	initbarea(&sblk);
108 	initbarea(&asblk);
109 	sblk.b_un.b_buf = malloc(SBSIZE);
110 	asblk.b_un.b_buf = malloc(SBSIZE);
111 	if (sblk.b_un.b_buf == NULL || asblk.b_un.b_buf == NULL)
112 		errexit("cannot allocate space for superblock\n");
113 	if ((lp = getdisklabel((char *)NULL, fsreadfd)) != NULL)
114 		dev_bsize = secsize = lp->d_secsize;
115 	else
116 		dev_bsize = secsize = DEV_BSIZE;
117 	/*
118 	 * Read in the superblock, looking for alternates if necessary
119 	 */
120 	if (readsb(1) == 0) {
121 		if (bflag || preen || calcsb(dev, fsreadfd, &proto) == 0)
122 			return(0);
123 		if (reply("LOOK FOR ALTERNATE SUPERBLOCKS") == 0)
124 			return (0);
125 		for (cg = 1; cg < proto.e2fs_ncg; cg++) {
126 			bflag = fsbtodb(&proto,
127 				cg * proto.e2fs.e2fs_bpg + proto.e2fs.e2fs_first_dblock);
128 			if (readsb(0) != 0)
129 				break;
130 		}
131 		if (cg >= proto.e2fs_ncg) {
132 			printf("%s %s\n%s %s\n%s %s\n",
133 				"SEARCH FOR ALTERNATE SUPER-BLOCK",
134 				"FAILED. YOU MUST USE THE",
135 				"-b OPTION TO FSCK_FFS TO SPECIFY THE",
136 				"LOCATION OF AN ALTERNATE",
137 				"SUPER-BLOCK TO SUPPLY NEEDED",
138 				"INFORMATION; SEE fsck_ext2fs(8).");
139 			return(0);
140 		}
141 		doskipclean = 0;
142 		pwarn("USING ALTERNATE SUPERBLOCK AT %d\n", bflag);
143 	}
144 	if (debug)
145 		printf("state = %d\n", sblock.e2fs.e2fs_state);
146 	if (sblock.e2fs.e2fs_state == E2FS_ISCLEAN) {
147 		if (doskipclean) {
148 			pwarn("%sile system is clean; not checking\n",
149 				preen ? "f" : "** F");
150 			return (-1);
151 		}
152 		if (!preen)
153 			pwarn("** File system is already clean\n");
154 	}
155 	maxfsblock = sblock.e2fs.e2fs_bcount;
156 	maxino = sblock.e2fs_ncg * sblock.e2fs.e2fs_ipg;
157 	sizepb = sblock.e2fs_bsize;
158 	maxfilesize = sblock.e2fs_bsize * NDADDR - 1;
159 	for (i = 0; i < NIADDR; i++) {
160 		sizepb *= NINDIR(&sblock);
161 		maxfilesize += sizepb;
162 	}
163 	/*
164 	 * Check and potentially fix certain fields in the super block.
165 	 */
166 	if ((sblock.e2fs.e2fs_rbcount < 0) ||
167 			(sblock.e2fs.e2fs_rbcount > sblock.e2fs.e2fs_bcount)) {
168 		pfatal("IMPOSSIBLE RESERVED BLOCK COUNT=%d IN SUPERBLOCK",
169 			sblock.e2fs.e2fs_rbcount);
170 		if (reply("SET TO DEFAULT") == 1) {
171 			sblock.e2fs.e2fs_rbcount = sblock.e2fs.e2fs_bcount * 0.1;
172 			sbdirty();
173 			dirty(&asblk);
174 		}
175 	}
176 	if (sblock.e2fs.e2fs_bpg != sblock.e2fs.e2fs_fpg) {
177 		pfatal("WRONG FPG=%d (BPG=%d) IN SUPERBLOCK",
178 			sblock.e2fs.e2fs_fpg, sblock.e2fs.e2fs_bpg);
179 		return 0;
180 	}
181 	if (asblk.b_dirty && !bflag) {
182 		copyback_sb(&asblk);
183 		flush(fswritefd, &asblk);
184 	}
185 	/*
186 	 * read in the summary info.
187 	 */
188 
189 	sblock.e2fs_gd = malloc(sblock.e2fs_ngdb * sblock.e2fs_bsize);
190 	if (sblock.e2fs_gd == NULL)
191 		errexit("out of memory\n");
192 	asked = 0;
193 	for (i=0; i < sblock.e2fs_ngdb; i++) {
194 		if (bread(fsreadfd,(char *)
195 			&sblock.e2fs_gd[i* sblock.e2fs_bsize / sizeof(struct ext2_gd)],
196 			fsbtodb(&sblock, ((sblock.e2fs_bsize>1024)?0:1)+i+1),
197 			sblock.e2fs_bsize) != 0 && !asked) {
198 			pfatal("BAD SUMMARY INFORMATION");
199 			if (reply("CONTINUE") == 0)
200 				errexit("%s\n", "");
201 			asked++;
202 		}
203 	}
204 	/*
205 	 * allocate and initialize the necessary maps
206 	 */
207 	bmapsize = roundup(howmany(maxfsblock, NBBY), sizeof(int16_t));
208 	blockmap = calloc((unsigned)bmapsize, sizeof (char));
209 	if (blockmap == NULL) {
210 		printf("cannot alloc %u bytes for blockmap\n",
211 			(unsigned)bmapsize);
212 		goto badsblabel;
213 	}
214 	statemap = calloc((unsigned)(maxino + 2), sizeof(char));
215 	if (statemap == NULL) {
216 		printf("cannot alloc %u bytes for statemap\n",
217 			(unsigned)(maxino + 1));
218 		goto badsblabel;
219 	}
220 	typemap = calloc((unsigned)(maxino + 1), sizeof(char));
221 	if (typemap == NULL) {
222 		printf("cannot alloc %u bytes for typemap\n",
223 		    (unsigned)(maxino + 1));
224 		goto badsblabel;
225 	}
226 	lncntp = (int16_t *)calloc((unsigned)(maxino + 1), sizeof(int16_t));
227 	if (lncntp == NULL) {
228 		printf("cannot alloc %u bytes for lncntp\n",
229 			(unsigned)((maxino + 1) * sizeof(int16_t)));
230 		goto badsblabel;
231 	}
232 	for (numdirs = 0, cg = 0; cg < sblock.e2fs_ncg; cg++) {
233 		numdirs += fs2h16(sblock.e2fs_gd[cg].ext2bgd_ndirs);
234 	}
235 	inplast = 0;
236 	listmax = numdirs + 10;
237 	inpsort = (struct inoinfo **)calloc((unsigned)listmax,
238 		sizeof(struct inoinfo *));
239 	inphead = (struct inoinfo **)calloc((unsigned)numdirs,
240 		sizeof(struct inoinfo *));
241 	if (inpsort == NULL || inphead == NULL) {
242 		printf("cannot alloc %u bytes for inphead\n",
243 			(unsigned)(numdirs * sizeof(struct inoinfo *)));
244 		goto badsblabel;
245 	}
246 	bufinit();
247 	return (1);
248 
249 badsblabel:
250 	ckfini(0);
251 	return (0);
252 }
253 
254 /*
255  * Read in the super block and its summary info.
256  */
257 static int
258 readsb(listerr)
259 	int listerr;
260 {
261 	daddr_t super = bflag ? bflag : SBOFF / dev_bsize;
262 
263 	if (bread(fsreadfd, (char *)sblk.b_un.b_fs, super, (long)SBSIZE) != 0)
264 		return (0);
265 	sblk.b_bno = super;
266 	sblk.b_size = SBSIZE;
267 
268 	/* Copy the superblock in memory */
269 	e2fs_sbload(sblk.b_un.b_fs, &sblock.e2fs);
270 
271 	/*
272 	 * run a few consistency checks of the super block
273 	 */
274 	if (sblock.e2fs.e2fs_magic != E2FS_MAGIC) {
275 		badsb(listerr, "MAGIC NUMBER WRONG"); return (0);
276 	}
277 	if (sblock.e2fs.e2fs_log_bsize > 2) {
278 		badsb(listerr, "BAD LOG_BSIZE"); return (0);
279 	}
280 
281 	/* compute the dynamic fields of the in-memory sb */
282 	/* compute dynamic sb infos */
283 	sblock.e2fs_ncg =
284 		howmany(sblock.e2fs.e2fs_bcount - sblock.e2fs.e2fs_first_dblock,
285 		sblock.e2fs.e2fs_bpg);
286 	/* XXX assume hw bsize = 512 */
287 	sblock.e2fs_fsbtodb = sblock.e2fs.e2fs_log_bsize + 1;
288 	sblock.e2fs_bsize = 1024 << sblock.e2fs.e2fs_log_bsize;
289 	sblock.e2fs_bshift = LOG_MINBSIZE + sblock.e2fs.e2fs_log_bsize;
290 	sblock.e2fs_qbmask = sblock.e2fs_bsize - 1;
291 	sblock.e2fs_bmask = ~sblock.e2fs_qbmask;
292 	sblock.e2fs_ngdb = howmany(sblock.e2fs_ncg,
293 		sblock.e2fs_bsize / sizeof(struct ext2_gd));
294 	sblock.e2fs_ipb = sblock.e2fs_bsize / sizeof(struct ext2fs_dinode);
295 	sblock.e2fs_itpg = sblock.e2fs.e2fs_ipg/sblock.e2fs_ipb;
296 
297 	/*
298 	 * Compute block size that the filesystem is based on,
299 	 * according to fsbtodb, and adjust superblock block number
300 	 * so we can tell if this is an alternate later.
301 	 */
302 	super *= dev_bsize;
303 	dev_bsize = sblock.e2fs_bsize / fsbtodb(&sblock, 1);
304 	sblk.b_bno = super / dev_bsize;
305 
306 	getblk(&asblk, 1 * sblock.e2fs.e2fs_bpg + sblock.e2fs.e2fs_first_dblock,
307 		(long)SBSIZE);
308 	if (asblk.b_errs)
309 		return (0);
310 	if (bflag) {
311 		havesb = 1;
312 		return (1);
313 	}
314 
315 	/*
316 	 * Set all possible fields that could differ, then do check
317 	 * of whole super block against an alternate super block.
318 	 * When an alternate super-block is specified this check is skipped.
319 	 */
320 	asblk.b_un.b_fs->e2fs_rbcount = sblk.b_un.b_fs->e2fs_rbcount;
321 	asblk.b_un.b_fs->e2fs_fbcount = sblk.b_un.b_fs->e2fs_fbcount;
322 	asblk.b_un.b_fs->e2fs_ficount = sblk.b_un.b_fs->e2fs_ficount;
323 	asblk.b_un.b_fs->e2fs_mtime = sblk.b_un.b_fs->e2fs_mtime;
324 	asblk.b_un.b_fs->e2fs_wtime = sblk.b_un.b_fs->e2fs_wtime;
325 	asblk.b_un.b_fs->e2fs_mnt_count = sblk.b_un.b_fs->e2fs_mnt_count;
326 	asblk.b_un.b_fs->e2fs_max_mnt_count = sblk.b_un.b_fs->e2fs_max_mnt_count;
327 	asblk.b_un.b_fs->e2fs_state = sblk.b_un.b_fs->e2fs_state;
328 	asblk.b_un.b_fs->e2fs_beh = sblk.b_un.b_fs->e2fs_beh;
329 	asblk.b_un.b_fs->e2fs_lastfsck = sblk.b_un.b_fs->e2fs_lastfsck;
330 	asblk.b_un.b_fs->e2fs_fsckintv = sblk.b_un.b_fs->e2fs_fsckintv;
331 	asblk.b_un.b_fs->e2fs_ruid = sblk.b_un.b_fs->e2fs_ruid;
332 	asblk.b_un.b_fs->e2fs_rgid = sblk.b_un.b_fs->e2fs_rgid;
333 	asblk.b_un.b_fs->e2fs_block_group_nr =
334 	    sblk.b_un.b_fs->e2fs_block_group_nr;
335 	if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
336 	    ((sblock.e2fs.e2fs_features_incompat & ~EXT2F_INCOMPAT_SUPP) ||
337 	    (sblock.e2fs.e2fs_features_rocompat & ~EXT2F_ROCOMPAT_SUPP))) {
338 		if (debug) {
339 			printf("compat 0x%08x, incompat 0x%08x, compat_ro "
340 			    "0x%08x\n",
341 			    sblock.e2fs.e2fs_features_compat,
342 			    sblock.e2fs.e2fs_features_incompat,
343 			    sblock.e2fs.e2fs_features_rocompat);
344 		}
345 		badsb(listerr,"INCOMPATIBLE FEATURE BITS IN SUPER BLOCK");
346 		return 0;
347 	}
348 	if (memcmp(sblk.b_un.b_fs, asblk.b_un.b_fs, SBSIZE)) {
349 		if (debug) {
350 			u_int32_t *nlp, *olp, *endlp;
351 
352 			printf("superblock mismatches\n");
353 			nlp = (u_int32_t *)asblk.b_un.b_fs;
354 			olp = (u_int32_t *)sblk.b_un.b_fs;
355 			endlp = olp + (SBSIZE / sizeof *olp);
356 			for ( ; olp < endlp; olp++, nlp++) {
357 				if (*olp == *nlp)
358 					continue;
359 				printf("offset %ld, original %ld, alternate %ld\n",
360 					(long)(olp - (u_int32_t *)sblk.b_un.b_fs),
361 					(long)fs2h32(*olp),
362 					(long)fs2h32(*nlp));
363 			}
364 		}
365 		badsb(listerr,
366 		"VALUES IN SUPER BLOCK DISAGREE WITH THOSE IN FIRST ALTERNATE");
367 		return (0);
368 	}
369 	havesb = 1;
370 	return (1);
371 }
372 
373 void
374 copyback_sb(bp)
375 	struct bufarea *bp;
376 {
377 	/* Copy the in-memory superblock back to buffer */
378 	bp->b_un.b_fs->e2fs_icount = fs2h32(sblock.e2fs.e2fs_icount);
379 	bp->b_un.b_fs->e2fs_bcount = fs2h32(sblock.e2fs.e2fs_bcount);
380 	bp->b_un.b_fs->e2fs_rbcount = fs2h32(sblock.e2fs.e2fs_rbcount);
381 	bp->b_un.b_fs->e2fs_fbcount = fs2h32(sblock.e2fs.e2fs_fbcount);
382 	bp->b_un.b_fs->e2fs_ficount = fs2h32(sblock.e2fs.e2fs_ficount);
383 	bp->b_un.b_fs->e2fs_first_dblock =
384 					fs2h32(sblock.e2fs.e2fs_first_dblock);
385 	bp->b_un.b_fs->e2fs_log_bsize = fs2h32(sblock.e2fs.e2fs_log_bsize);
386 	bp->b_un.b_fs->e2fs_fsize = fs2h32(sblock.e2fs.e2fs_fsize);
387 	bp->b_un.b_fs->e2fs_bpg = fs2h32(sblock.e2fs.e2fs_bpg);
388 	bp->b_un.b_fs->e2fs_fpg = fs2h32(sblock.e2fs.e2fs_fpg);
389 	bp->b_un.b_fs->e2fs_ipg = fs2h32(sblock.e2fs.e2fs_ipg);
390 	bp->b_un.b_fs->e2fs_mtime = fs2h32(sblock.e2fs.e2fs_mtime);
391 	bp->b_un.b_fs->e2fs_wtime = fs2h32(sblock.e2fs.e2fs_wtime);
392 	bp->b_un.b_fs->e2fs_lastfsck = fs2h32(sblock.e2fs.e2fs_lastfsck);
393 	bp->b_un.b_fs->e2fs_fsckintv = fs2h32(sblock.e2fs.e2fs_fsckintv);
394 	bp->b_un.b_fs->e2fs_creator = fs2h32(sblock.e2fs.e2fs_creator);
395 	bp->b_un.b_fs->e2fs_rev = fs2h32(sblock.e2fs.e2fs_rev);
396 	bp->b_un.b_fs->e2fs_mnt_count = fs2h16(sblock.e2fs.e2fs_mnt_count);
397 	bp->b_un.b_fs->e2fs_max_mnt_count =
398 					fs2h16(sblock.e2fs.e2fs_max_mnt_count);
399 	bp->b_un.b_fs->e2fs_magic = fs2h16(sblock.e2fs.e2fs_magic);
400 	bp->b_un.b_fs->e2fs_state = fs2h16(sblock.e2fs.e2fs_state);
401 	bp->b_un.b_fs->e2fs_beh = fs2h16(sblock.e2fs.e2fs_beh);
402 	bp->b_un.b_fs->e2fs_ruid = fs2h16(sblock.e2fs.e2fs_ruid);
403 	bp->b_un.b_fs->e2fs_rgid = fs2h16(sblock.e2fs.e2fs_rgid);
404 }
405 
406 void
407 badsb(listerr, s)
408 	int listerr;
409 	char *s;
410 {
411 
412 	if (!listerr)
413 		return;
414 	if (preen)
415 		printf("%s: ", cdevname());
416 	pfatal("BAD SUPER BLOCK: %s\n", s);
417 }
418 
419 /*
420  * Calculate a prototype superblock based on information in the disk label.
421  * When done the cgsblock macro can be calculated and the fs_ncg field
422  * can be used. Do NOT attempt to use other macros without verifying that
423  * their needed information is available!
424  */
425 
426 int
427 calcsb(dev, devfd, fs)
428 	char *dev;
429 	int devfd;
430 	struct m_ext2fs *fs;
431 {
432 	struct disklabel *lp;
433 	struct partition *pp;
434 	char *cp;
435 
436 	cp = strchr(dev, '\0') - 1;
437 	if ((cp == (char *)-1 || (*cp < 'a' || *cp > 'h')) && !isdigit(*cp)) {
438 		pfatal("%s: CANNOT FIGURE OUT FILE SYSTEM PARTITION\n", dev);
439 		return (0);
440 	}
441 	lp = getdisklabel(dev, devfd);
442 	if (isdigit(*cp))
443 		pp = &lp->d_partitions[0];
444 	else
445 		pp = &lp->d_partitions[*cp - 'a'];
446 	if (pp->p_fstype != FS_EXT2FS) {
447 		pfatal("%s: NOT LABELED AS A EXT2 FILE SYSTEM (%s)\n",
448 			dev, pp->p_fstype < FSMAXTYPES ?
449 			fstypenames[pp->p_fstype] : "unknown");
450 		return (0);
451 	}
452 	memset(fs, 0, sizeof(struct m_ext2fs));
453 	fs->e2fs_bsize = pp->p_fsize;
454 	fs->e2fs.e2fs_log_bsize = pp->p_fsize / 1024;
455 	fs->e2fs.e2fs_bcount = (pp->p_size * DEV_BSIZE) / fs->e2fs_bsize;
456 	fs->e2fs.e2fs_first_dblock = (fs->e2fs.e2fs_log_bsize == 0) ? 1 : 0;
457 	fs->e2fs.e2fs_bpg = fs->e2fs_bsize * NBBY;
458 	fs->e2fs_bshift = LOG_MINBSIZE + fs->e2fs.e2fs_log_bsize;
459 	fs->e2fs_qbmask = fs->e2fs_bsize - 1;
460 	fs->e2fs_bmask = ~fs->e2fs_qbmask;
461 	fs->e2fs_ncg =
462 		howmany(fs->e2fs.e2fs_bcount - fs->e2fs.e2fs_first_dblock,
463 		fs->e2fs.e2fs_bpg);
464 	fs->e2fs_fsbtodb = fs->e2fs.e2fs_log_bsize + 1;
465 	fs->e2fs_ngdb = howmany(fs->e2fs_ncg,
466 		fs->e2fs_bsize / sizeof(struct ext2_gd));
467 
468 	return (1);
469 }
470 
471 static struct disklabel *
472 getdisklabel(s, fd)
473 	char *s;
474 	int	fd;
475 {
476 	static struct disklabel lab;
477 
478 	if (ioctl(fd, DIOCGDINFO, (char *)&lab) < 0) {
479 		if (s == NULL)
480 			return ((struct disklabel *)NULL);
481 		pwarn("ioctl (GCINFO): %s\n", strerror(errno));
482 		errexit("%s: can't read disk label\n", s);
483 	}
484 	return (&lab);
485 }
486 
487 daddr_t
488 cgoverhead(c)
489 	int c;
490 {
491 	int overh;
492 	overh =	1 /* block bitmap */ +
493 		1 /* inode bitmap */ +
494 		sblock.e2fs_itpg;
495 	if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
496 	    sblock.e2fs.e2fs_features_rocompat & EXT2F_ROCOMPAT_SPARSESUPER) {
497 		if (cg_has_sb(c) == 0)
498 			return overh;
499 	}
500 	overh += 1 + sblock.e2fs_ngdb;
501 	return overh;
502 }
503