xref: /openbsd-src/sbin/fsck_ext2fs/setup.c (revision a28daedfc357b214be5c701aa8ba8adb29a7f1c2)
1 /*	$OpenBSD: setup.c,v 1.15 2007/09/02 15:19:23 deraadt 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. 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 #define DKTYPENAMES
35 #include <sys/param.h>
36 #include <sys/time.h>
37 #include <ufs/ext2fs/ext2fs_dinode.h>
38 #include <ufs/ext2fs/ext2fs.h>
39 #include <sys/stat.h>
40 #include <sys/ioctl.h>
41 #include <sys/disklabel.h>
42 #include <sys/file.h>
43 
44 #include <errno.h>
45 #include <fcntl.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <ctype.h>
50 
51 #include "fsck.h"
52 #include "extern.h"
53 #include "fsutil.h"
54 
55 #define POWEROF2(num)	(((num) & ((num) - 1)) == 0)
56 
57 void badsb(int, char *);
58 int calcsb(char *, int, struct m_ext2fs *);
59 static struct disklabel *getdisklabel(char *, int);
60 static int readsb(int);
61 
62 int
63 setup(char *dev)
64 {
65 	long cg, asked, i;
66 	long bmapsize;
67 	struct disklabel *lp;
68 	off_t sizepb;
69 	struct stat statb;
70 	struct m_ext2fs proto;
71 	int doskipclean;
72 	u_int64_t maxfilesize;
73 
74 	havesb = 0;
75 	fswritefd = -1;
76 	doskipclean = skipclean;
77 	if (stat(dev, &statb) < 0) {
78 		printf("Can't stat %s: %s\n", dev, strerror(errno));
79 		return (0);
80 	}
81 	if (!S_ISCHR(statb.st_mode)) {
82 		pfatal("%s is not a character device", dev);
83 		if (reply("CONTINUE") == 0)
84 			return (0);
85 	}
86 	if ((fsreadfd = open(dev, O_RDONLY)) < 0) {
87 		printf("Can't open %s: %s\n", dev, strerror(errno));
88 		return (0);
89 	}
90 	if (preen == 0)
91 		printf("** %s", dev);
92 	if (nflag || (fswritefd = open(dev, O_WRONLY)) < 0) {
93 		fswritefd = -1;
94 		if (preen)
95 			pfatal("NO WRITE ACCESS");
96 		printf(" (NO WRITE)");
97 	}
98 	if (preen == 0)
99 		printf("\n");
100 	fsmodified = 0;
101 	lfdir = 0;
102 	initbarea(&sblk);
103 	initbarea(&asblk);
104 	sblk.b_un.b_buf = malloc(SBSIZE);
105 	asblk.b_un.b_buf = malloc(SBSIZE);
106 	if (sblk.b_un.b_buf == NULL || asblk.b_un.b_buf == NULL)
107 		errexit("cannot allocate space for superblock\n");
108 	if ((lp = getdisklabel((char *)NULL, fsreadfd)) != NULL)
109 		dev_bsize = secsize = lp->d_secsize;
110 	else
111 		dev_bsize = secsize = DEV_BSIZE;
112 	/*
113 	 * Read in the superblock, looking for alternates if necessary
114 	 */
115 	if (readsb(1) == 0) {
116 		if (bflag || preen || calcsb(dev, fsreadfd, &proto) == 0)
117 			return(0);
118 		if (reply("LOOK FOR ALTERNATE SUPERBLOCKS") == 0)
119 			return (0);
120 		for (cg = 1; cg < proto.e2fs_ncg; cg++) {
121 			bflag = fsbtodb(&proto,
122 				cg * proto.e2fs.e2fs_bpg + proto.e2fs.e2fs_first_dblock);
123 			if (readsb(0) != 0)
124 				break;
125 		}
126 		if (cg >= proto.e2fs_ncg) {
127 			printf("%s %s\n%s %s\n%s %s\n",
128 				"SEARCH FOR ALTERNATE SUPER-BLOCK",
129 				"FAILED. YOU MUST USE THE",
130 				"-b OPTION TO FSCK_FFS TO SPECIFY THE",
131 				"LOCATION OF AN ALTERNATE",
132 				"SUPER-BLOCK TO SUPPLY NEEDED",
133 				"INFORMATION; SEE fsck_ext2fs(8).");
134 			return(0);
135 		}
136 		doskipclean = 0;
137 		pwarn("USING ALTERNATE SUPERBLOCK AT %d\n", bflag);
138 	}
139 	if (debug)
140 		printf("state = %d\n", sblock.e2fs.e2fs_state);
141 	if (sblock.e2fs.e2fs_state == E2FS_ISCLEAN) {
142 		if (doskipclean) {
143 			pwarn("%sile system is clean; not checking\n",
144 				preen ? "f" : "** F");
145 			return (-1);
146 		}
147 		if (!preen)
148 			pwarn("** File system is already clean\n");
149 	}
150 	maxfsblock = sblock.e2fs.e2fs_bcount;
151 	maxino = sblock.e2fs_ncg * sblock.e2fs.e2fs_ipg;
152 	sizepb = sblock.e2fs_bsize;
153 	maxfilesize = sblock.e2fs_bsize * NDADDR - 1;
154 	for (i = 0; i < NIADDR; i++) {
155 		sizepb *= NINDIR(&sblock);
156 		maxfilesize += sizepb;
157 	}
158 	/*
159 	 * Check and potentially fix certain fields in the super block.
160 	 */
161 	if ((sblock.e2fs.e2fs_rbcount < 0) ||
162 			(sblock.e2fs.e2fs_rbcount > sblock.e2fs.e2fs_bcount)) {
163 		pfatal("IMPOSSIBLE RESERVED BLOCK COUNT=%d IN SUPERBLOCK",
164 			sblock.e2fs.e2fs_rbcount);
165 		if (reply("SET TO DEFAULT") == 1) {
166 			sblock.e2fs.e2fs_rbcount = sblock.e2fs.e2fs_bcount * 0.1;
167 			sbdirty();
168 			dirty(&asblk);
169 		}
170 	}
171 	if (sblock.e2fs.e2fs_bpg != sblock.e2fs.e2fs_fpg) {
172 		pfatal("WRONG FPG=%d (BPG=%d) IN SUPERBLOCK",
173 			sblock.e2fs.e2fs_fpg, sblock.e2fs.e2fs_bpg);
174 		return 0;
175 	}
176 	if (asblk.b_dirty && !bflag) {
177 		copyback_sb(&asblk);
178 		flush(fswritefd, &asblk);
179 	}
180 	/*
181 	 * read in the summary info.
182 	 */
183 
184 	sblock.e2fs_gd = calloc(sblock.e2fs_ngdb, sblock.e2fs_bsize);
185 	if (sblock.e2fs_gd == NULL)
186 		errexit("out of memory\n");
187 	asked = 0;
188 	for (i=0; i < sblock.e2fs_ngdb; i++) {
189 		if (bread(fsreadfd,(char *)
190 			&sblock.e2fs_gd[i* sblock.e2fs_bsize / sizeof(struct ext2_gd)],
191 			fsbtodb(&sblock, ((sblock.e2fs_bsize>1024)?0:1)+i+1),
192 			sblock.e2fs_bsize) != 0 && !asked) {
193 			pfatal("BAD SUMMARY INFORMATION");
194 			if (reply("CONTINUE") == 0)
195 				errexit("%s\n", "");
196 			asked++;
197 		}
198 	}
199 	/*
200 	 * allocate and initialize the necessary maps
201 	 */
202 	bmapsize = roundup(howmany(maxfsblock, NBBY), sizeof(int16_t));
203 	blockmap = calloc((unsigned)bmapsize, sizeof (char));
204 	if (blockmap == NULL) {
205 		printf("cannot alloc %u bytes for blockmap\n",
206 			(unsigned)bmapsize);
207 		goto badsblabel;
208 	}
209 	statemap = calloc((unsigned)(maxino + 2), sizeof(char));
210 	if (statemap == NULL) {
211 		printf("cannot alloc %u bytes for statemap\n",
212 			(unsigned)(maxino + 1));
213 		goto badsblabel;
214 	}
215 	typemap = calloc((unsigned)(maxino + 1), sizeof(char));
216 	if (typemap == NULL) {
217 		printf("cannot alloc %u bytes for typemap\n",
218 		    (unsigned)(maxino + 1));
219 		goto badsblabel;
220 	}
221 	lncntp = (int16_t *)calloc((unsigned)(maxino + 1), sizeof(int16_t));
222 	if (lncntp == NULL) {
223 		printf("cannot alloc %u bytes for lncntp\n",
224 			(unsigned)((maxino + 1) * sizeof(int16_t)));
225 		goto badsblabel;
226 	}
227 	for (numdirs = 0, cg = 0; cg < sblock.e2fs_ncg; cg++) {
228 		numdirs += fs2h16(sblock.e2fs_gd[cg].ext2bgd_ndirs);
229 	}
230 	inplast = 0;
231 	listmax = numdirs + 10;
232 	inpsort = (struct inoinfo **)calloc((unsigned)listmax,
233 		sizeof(struct inoinfo *));
234 	inphead = (struct inoinfo **)calloc((unsigned)numdirs,
235 		sizeof(struct inoinfo *));
236 	if (inpsort == NULL || inphead == NULL) {
237 		printf("cannot alloc %u bytes for inphead\n",
238 			(unsigned)(numdirs * sizeof(struct inoinfo *)));
239 		goto badsblabel;
240 	}
241 	bufinit();
242 	return (1);
243 
244 badsblabel:
245 	ckfini(0);
246 	return (0);
247 }
248 
249 /*
250  * Read in the super block and its summary info.
251  */
252 static int
253 readsb(int listerr)
254 {
255 	daddr_t super = bflag ? bflag : SBOFF / dev_bsize;
256 
257 	if (bread(fsreadfd, (char *)sblk.b_un.b_fs, super, (long)SBSIZE) != 0)
258 		return (0);
259 	sblk.b_bno = super;
260 	sblk.b_size = SBSIZE;
261 
262 	/* Copy the superblock in memory */
263 	e2fs_sbload(sblk.b_un.b_fs, &sblock.e2fs);
264 
265 	/*
266 	 * run a few consistency checks of the super block
267 	 */
268 	if (sblock.e2fs.e2fs_magic != E2FS_MAGIC) {
269 		badsb(listerr, "MAGIC NUMBER WRONG"); return (0);
270 	}
271 	if (sblock.e2fs.e2fs_log_bsize > 2) {
272 		badsb(listerr, "BAD LOG_BSIZE"); return (0);
273 	}
274 
275 	/* compute the dynamic fields of the in-memory sb */
276 	/* compute dynamic sb infos */
277 	sblock.e2fs_ncg =
278 		howmany(sblock.e2fs.e2fs_bcount - sblock.e2fs.e2fs_first_dblock,
279 		sblock.e2fs.e2fs_bpg);
280 	/* XXX assume hw bsize = 512 */
281 	sblock.e2fs_fsbtodb = sblock.e2fs.e2fs_log_bsize + 1;
282 	sblock.e2fs_bsize = 1024 << sblock.e2fs.e2fs_log_bsize;
283 	sblock.e2fs_bshift = LOG_MINBSIZE + sblock.e2fs.e2fs_log_bsize;
284 	sblock.e2fs_qbmask = sblock.e2fs_bsize - 1;
285 	sblock.e2fs_bmask = ~sblock.e2fs_qbmask;
286 	sblock.e2fs_ngdb = howmany(sblock.e2fs_ncg,
287 		sblock.e2fs_bsize / sizeof(struct ext2_gd));
288 	sblock.e2fs_ipb = sblock.e2fs_bsize / sizeof(struct ext2fs_dinode);
289 	sblock.e2fs_itpg = sblock.e2fs.e2fs_ipg/sblock.e2fs_ipb;
290 
291 	/*
292 	 * Compute block size that the filesystem is based on,
293 	 * according to fsbtodb, and adjust superblock block number
294 	 * so we can tell if this is an alternate later.
295 	 */
296 	super *= dev_bsize;
297 	dev_bsize = sblock.e2fs_bsize / fsbtodb(&sblock, 1);
298 	sblk.b_bno = super / dev_bsize;
299 
300 	getblk(&asblk, 1 * sblock.e2fs.e2fs_bpg + sblock.e2fs.e2fs_first_dblock,
301 		(long)SBSIZE);
302 	if (asblk.b_errs)
303 		return (0);
304 	if (bflag) {
305 		havesb = 1;
306 		return (1);
307 	}
308 
309 	/*
310 	 * Set all possible fields that could differ, then do check
311 	 * of whole super block against an alternate super block.
312 	 * When an alternate super-block is specified this check is skipped.
313 	 */
314 	asblk.b_un.b_fs->e2fs_rbcount = sblk.b_un.b_fs->e2fs_rbcount;
315 	asblk.b_un.b_fs->e2fs_fbcount = sblk.b_un.b_fs->e2fs_fbcount;
316 	asblk.b_un.b_fs->e2fs_ficount = sblk.b_un.b_fs->e2fs_ficount;
317 	asblk.b_un.b_fs->e2fs_mtime = sblk.b_un.b_fs->e2fs_mtime;
318 	asblk.b_un.b_fs->e2fs_wtime = sblk.b_un.b_fs->e2fs_wtime;
319 	asblk.b_un.b_fs->e2fs_mnt_count = sblk.b_un.b_fs->e2fs_mnt_count;
320 	asblk.b_un.b_fs->e2fs_max_mnt_count = sblk.b_un.b_fs->e2fs_max_mnt_count;
321 	asblk.b_un.b_fs->e2fs_state = sblk.b_un.b_fs->e2fs_state;
322 	asblk.b_un.b_fs->e2fs_beh = sblk.b_un.b_fs->e2fs_beh;
323 	asblk.b_un.b_fs->e2fs_lastfsck = sblk.b_un.b_fs->e2fs_lastfsck;
324 	asblk.b_un.b_fs->e2fs_fsckintv = sblk.b_un.b_fs->e2fs_fsckintv;
325 	asblk.b_un.b_fs->e2fs_ruid = sblk.b_un.b_fs->e2fs_ruid;
326 	asblk.b_un.b_fs->e2fs_rgid = sblk.b_un.b_fs->e2fs_rgid;
327 	asblk.b_un.b_fs->e2fs_block_group_nr =
328 	    sblk.b_un.b_fs->e2fs_block_group_nr;
329 	asblk.b_un.b_fs->e2fs_features_rocompat &= ~EXT2F_ROCOMPAT_LARGEFILE;
330 	asblk.b_un.b_fs->e2fs_features_rocompat |=
331 	    sblk.b_un.b_fs->e2fs_features_rocompat & EXT2F_ROCOMPAT_LARGEFILE;
332 	if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
333 	    ((sblock.e2fs.e2fs_features_incompat & ~EXT2F_INCOMPAT_SUPP) ||
334 	    (sblock.e2fs.e2fs_features_rocompat & ~EXT2F_ROCOMPAT_SUPP))) {
335 		if (debug) {
336 			printf("compat 0x%08x, incompat 0x%08x, compat_ro "
337 			    "0x%08x\n",
338 			    sblock.e2fs.e2fs_features_compat,
339 			    sblock.e2fs.e2fs_features_incompat,
340 			    sblock.e2fs.e2fs_features_rocompat);
341 		}
342 		badsb(listerr,"INCOMPATIBLE FEATURE BITS IN SUPER BLOCK");
343 		return 0;
344 	}
345 	if (memcmp(sblk.b_un.b_fs, asblk.b_un.b_fs, SBSIZE)) {
346 		if (debug) {
347 			u_int32_t *nlp, *olp, *endlp;
348 
349 			printf("superblock mismatches\n");
350 			nlp = (u_int32_t *)asblk.b_un.b_fs;
351 			olp = (u_int32_t *)sblk.b_un.b_fs;
352 			endlp = olp + (SBSIZE / sizeof *olp);
353 			for ( ; olp < endlp; olp++, nlp++) {
354 				if (*olp == *nlp)
355 					continue;
356 				printf("offset %ld, original %ld, alternate %ld\n",
357 					(long)(olp - (u_int32_t *)sblk.b_un.b_fs),
358 					(long)fs2h32(*olp),
359 					(long)fs2h32(*nlp));
360 			}
361 		}
362 		badsb(listerr,
363 		"VALUES IN SUPER BLOCK DISAGREE WITH THOSE IN FIRST ALTERNATE");
364 		return (0);
365 	}
366 	havesb = 1;
367 	return (1);
368 }
369 
370 void
371 copyback_sb(struct bufarea *bp)
372 {
373 	/* Copy the in-memory superblock back to buffer */
374 	bp->b_un.b_fs->e2fs_icount = fs2h32(sblock.e2fs.e2fs_icount);
375 	bp->b_un.b_fs->e2fs_bcount = fs2h32(sblock.e2fs.e2fs_bcount);
376 	bp->b_un.b_fs->e2fs_rbcount = fs2h32(sblock.e2fs.e2fs_rbcount);
377 	bp->b_un.b_fs->e2fs_fbcount = fs2h32(sblock.e2fs.e2fs_fbcount);
378 	bp->b_un.b_fs->e2fs_ficount = fs2h32(sblock.e2fs.e2fs_ficount);
379 	bp->b_un.b_fs->e2fs_first_dblock =
380 					fs2h32(sblock.e2fs.e2fs_first_dblock);
381 	bp->b_un.b_fs->e2fs_log_bsize = fs2h32(sblock.e2fs.e2fs_log_bsize);
382 	bp->b_un.b_fs->e2fs_fsize = fs2h32(sblock.e2fs.e2fs_fsize);
383 	bp->b_un.b_fs->e2fs_bpg = fs2h32(sblock.e2fs.e2fs_bpg);
384 	bp->b_un.b_fs->e2fs_fpg = fs2h32(sblock.e2fs.e2fs_fpg);
385 	bp->b_un.b_fs->e2fs_ipg = fs2h32(sblock.e2fs.e2fs_ipg);
386 	bp->b_un.b_fs->e2fs_mtime = fs2h32(sblock.e2fs.e2fs_mtime);
387 	bp->b_un.b_fs->e2fs_wtime = fs2h32(sblock.e2fs.e2fs_wtime);
388 	bp->b_un.b_fs->e2fs_lastfsck = fs2h32(sblock.e2fs.e2fs_lastfsck);
389 	bp->b_un.b_fs->e2fs_fsckintv = fs2h32(sblock.e2fs.e2fs_fsckintv);
390 	bp->b_un.b_fs->e2fs_creator = fs2h32(sblock.e2fs.e2fs_creator);
391 	bp->b_un.b_fs->e2fs_rev = fs2h32(sblock.e2fs.e2fs_rev);
392 	bp->b_un.b_fs->e2fs_mnt_count = fs2h16(sblock.e2fs.e2fs_mnt_count);
393 	bp->b_un.b_fs->e2fs_max_mnt_count =
394 					fs2h16(sblock.e2fs.e2fs_max_mnt_count);
395 	bp->b_un.b_fs->e2fs_magic = fs2h16(sblock.e2fs.e2fs_magic);
396 	bp->b_un.b_fs->e2fs_state = fs2h16(sblock.e2fs.e2fs_state);
397 	bp->b_un.b_fs->e2fs_beh = fs2h16(sblock.e2fs.e2fs_beh);
398 	bp->b_un.b_fs->e2fs_ruid = fs2h16(sblock.e2fs.e2fs_ruid);
399 	bp->b_un.b_fs->e2fs_rgid = fs2h16(sblock.e2fs.e2fs_rgid);
400 }
401 
402 void
403 badsb(int listerr, char *s)
404 {
405 
406 	if (!listerr)
407 		return;
408 	if (preen)
409 		printf("%s: ", cdevname());
410 	pfatal("BAD SUPER BLOCK: %s\n", s);
411 }
412 
413 /*
414  * Calculate a prototype superblock based on information in the disk label.
415  * When done the cgsblock macro can be calculated and the fs_ncg field
416  * can be used. Do NOT attempt to use other macros without verifying that
417  * their needed information is available!
418  */
419 
420 int
421 calcsb(char *dev, int devfd, struct m_ext2fs *fs)
422 {
423 	struct disklabel *lp;
424 	struct partition *pp;
425 	char *cp;
426 
427 	cp = strchr(dev, '\0') - 1;
428 	if ((cp == (char *)-1 || (*cp < 'a' || *cp > 'h')) && !isdigit(*cp)) {
429 		pfatal("%s: CANNOT FIGURE OUT FILE SYSTEM PARTITION\n", dev);
430 		return (0);
431 	}
432 	lp = getdisklabel(dev, devfd);
433 	if (isdigit(*cp))
434 		pp = &lp->d_partitions[0];
435 	else
436 		pp = &lp->d_partitions[*cp - 'a'];
437 	if (pp->p_fstype != FS_EXT2FS) {
438 		pfatal("%s: NOT LABELED AS A EXT2 FILE SYSTEM (%s)\n",
439 			dev, pp->p_fstype < FSMAXTYPES ?
440 			fstypenames[pp->p_fstype] : "unknown");
441 		return (0);
442 	}
443 	memset(fs, 0, sizeof(struct m_ext2fs));
444 	fs->e2fs_bsize = DISKLABELV1_FFS_FSIZE(pp->p_fragblock); /* XXX */
445 	fs->e2fs.e2fs_log_bsize = fs->e2fs_bsize / 1024;
446 	fs->e2fs.e2fs_bcount = (pp->p_size * DEV_BSIZE) / fs->e2fs_bsize;
447 	fs->e2fs.e2fs_first_dblock = (fs->e2fs.e2fs_log_bsize == 0) ? 1 : 0;
448 	fs->e2fs.e2fs_bpg = fs->e2fs_bsize * NBBY;
449 	fs->e2fs_bshift = LOG_MINBSIZE + fs->e2fs.e2fs_log_bsize;
450 	fs->e2fs_qbmask = fs->e2fs_bsize - 1;
451 	fs->e2fs_bmask = ~fs->e2fs_qbmask;
452 	fs->e2fs_ncg =
453 		howmany(fs->e2fs.e2fs_bcount - fs->e2fs.e2fs_first_dblock,
454 		fs->e2fs.e2fs_bpg);
455 	fs->e2fs_fsbtodb = fs->e2fs.e2fs_log_bsize + 1;
456 	fs->e2fs_ngdb = howmany(fs->e2fs_ncg,
457 		fs->e2fs_bsize / sizeof(struct ext2_gd));
458 
459 	return (1);
460 }
461 
462 static struct disklabel *
463 getdisklabel(char *s, int fd)
464 {
465 	static struct disklabel lab;
466 
467 	if (ioctl(fd, DIOCGDINFO, (char *)&lab) < 0) {
468 		if (s == NULL)
469 			return ((struct disklabel *)NULL);
470 		pwarn("ioctl (GCINFO): %s\n", strerror(errno));
471 		errexit("%s: can't read disk label\n", s);
472 	}
473 	return (&lab);
474 }
475 
476 daddr_t
477 cgoverhead(int c)
478 {
479 	int overh;
480 	overh =	1 /* block bitmap */ +
481 		1 /* inode bitmap */ +
482 		sblock.e2fs_itpg;
483 	if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
484 	    sblock.e2fs.e2fs_features_rocompat & EXT2F_ROCOMPAT_SPARSESUPER) {
485 		if (cg_has_sb(c) == 0)
486 			return overh;
487 	}
488 	overh += 1 + sblock.e2fs_ngdb;
489 	return overh;
490 }
491