xref: /netbsd-src/sbin/dump/traverse.c (revision fdecd6a253f999ae92b139670d9e15cc9df4497c)
1 /*	$NetBSD: traverse.c,v 1.17 1997/06/05 11:13:27 lukem Exp $	*/
2 
3 /*-
4  * Copyright (c) 1980, 1988, 1991, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by the University of
18  *	California, Berkeley and its contributors.
19  * 4. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  */
35 
36 #ifndef lint
37 #if 0
38 static char sccsid[] = "@(#)traverse.c	8.2 (Berkeley) 9/23/93";
39 #else
40 static char rcsid[] = "$NetBSD: traverse.c,v 1.17 1997/06/05 11:13:27 lukem Exp $";
41 #endif
42 #endif /* not lint */
43 
44 #include <sys/param.h>
45 #include <sys/time.h>
46 #include <sys/stat.h>
47 #ifdef sunos
48 #include <sys/vnode.h>
49 
50 #include <ufs/fs.h>
51 #include <ufs/fsdir.h>
52 #include <ufs/inode.h>
53 #else
54 #include <ufs/ffs/fs.h>
55 #include <ufs/ufs/dir.h>
56 #include <ufs/ufs/dinode.h>
57 #endif
58 
59 #include <protocols/dumprestore.h>
60 
61 #include <ctype.h>
62 #include <errno.h>
63 #include <fts.h>
64 #include <stdio.h>
65 #ifdef __STDC__
66 #include <string.h>
67 #include <unistd.h>
68 #endif
69 
70 #include "dump.h"
71 
72 #define	HASDUMPEDFILE	0x1
73 #define	HASSUBDIRS	0x2
74 
75 #ifdef	FS_44INODEFMT
76 typedef	quad_t fsizeT;
77 #else
78 typedef	int32_t fsizeT;
79 #endif
80 
81 static	int dirindir __P((ino_t ino, daddr_t blkno, int level, long *size));
82 static	void dmpindir __P((ino_t ino, daddr_t blk, int level, fsizeT *size));
83 static	int searchdir __P((ino_t ino, daddr_t blkno, long size, long filesize));
84 
85 /*
86  * This is an estimation of the number of TP_BSIZE blocks in the file.
87  * It estimates the number of blocks in files with holes by assuming
88  * that all of the blocks accounted for by di_blocks are data blocks
89  * (when some of the blocks are usually used for indirect pointers);
90  * hence the estimate may be high.
91  */
92 long
93 blockest(dp)
94 	struct dinode *dp;
95 {
96 	long blkest, sizeest;
97 
98 	/*
99 	 * dp->di_size is the size of the file in bytes.
100 	 * dp->di_blocks stores the number of sectors actually in the file.
101 	 * If there are more sectors than the size would indicate, this just
102 	 *	means that there are indirect blocks in the file or unused
103 	 *	sectors in the last file block; we can safely ignore these
104 	 *	(blkest = sizeest below).
105 	 * If the file is bigger than the number of sectors would indicate,
106 	 *	then the file has holes in it.	In this case we must use the
107 	 *	block count to estimate the number of data blocks used, but
108 	 *	we use the actual size for estimating the number of indirect
109 	 *	dump blocks (sizeest vs. blkest in the indirect block
110 	 *	calculation).
111 	 */
112 	blkest = howmany(dbtob(dp->di_blocks), TP_BSIZE);
113 	sizeest = howmany(dp->di_size, TP_BSIZE);
114 	if (blkest > sizeest)
115 		blkest = sizeest;
116 	if (dp->di_size > sblock->fs_bsize * NDADDR) {
117 		/* calculate the number of indirect blocks on the dump tape */
118 		blkest +=
119 			howmany(sizeest - NDADDR * sblock->fs_bsize / TP_BSIZE,
120 			TP_NINDIR);
121 	}
122 	return (blkest + 1);
123 }
124 
125 /* Auxiliary macro to pick up files changed since previous dump. */
126 #define	CHANGEDSINCE(dp, t) \
127 	((dp)->di_mtime >= (t) || (dp)->di_ctime >= (t))
128 
129 /* The WANTTODUMP macro decides whether a file should be dumped. */
130 #ifdef UF_NODUMP
131 #define	WANTTODUMP(dp) \
132 	(CHANGEDSINCE(dp, spcl.c_ddate) && \
133 	 (nonodump || ((dp)->di_flags & UF_NODUMP) != UF_NODUMP))
134 #else
135 #define	WANTTODUMP(dp) CHANGEDSINCE(dp, spcl.c_ddate)
136 #endif
137 
138 /*
139  * Determine if given inode should be dumped
140  */
141 void
142 mapfileino(ino, tapesize, dirskipped)
143 	ino_t ino;
144 	long *tapesize;
145 	int *dirskipped;
146 {
147 	int mode;
148 	struct dinode *dp;
149 
150 	dp = getino(ino);
151 	if ((mode = (dp->di_mode & IFMT)) == 0)
152 		return;
153 	SETINO(ino, usedinomap);
154 	if (mode == IFDIR)
155 		SETINO(ino, dumpdirmap);
156 	if (WANTTODUMP(dp)) {
157 		SETINO(ino, dumpinomap);
158 		if (mode != IFREG && mode != IFDIR && mode != IFLNK)
159 			*tapesize += 1;
160 		else
161 			*tapesize += blockest(dp);
162 		return;
163 	}
164 	if (mode == IFDIR)
165 		*dirskipped = 1;
166 }
167 
168 /*
169  * Dump pass 1.
170  *
171  * Walk the inode list for a filesystem to find all allocated inodes
172  * that have been modified since the previous dump time. Also, find all
173  * the directories in the filesystem.
174  */
175 int
176 mapfiles(maxino, tapesize, disk, dirv)
177 	ino_t maxino;
178 	long *tapesize;
179 	char *disk;
180 	char * const *dirv;
181 {
182 	int anydirskipped = 0;
183 
184 	if (dirv != NULL) {
185 		char	 curdir[MAXPATHLEN];
186 		FTS	*dirh;
187 		FTSENT	*entry;
188 		int	 d;
189 
190 		if (getcwd(curdir, sizeof(curdir)) == NULL) {
191 			msg("Can't determine cwd: %s\n", strerror(errno));
192 			dumpabort(0);
193 		}
194 		if ((dirh = fts_open(dirv, FTS_PHYSICAL|FTS_SEEDOT|FTS_XDEV,
195 		    		    (int (*)())NULL)) == NULL) {
196 			msg("fts_open failed: %s\n", strerror(errno));
197 			dumpabort(0);
198 		}
199 		while ((entry = fts_read(dirh)) != NULL) {
200 			switch (entry->fts_info) {
201 			case FTS_DNR:		/* an error */
202 			case FTS_ERR:
203 			case FTS_NS:
204 				msg("Can't fts_read %s: %s\n", entry->fts_path,
205 				    strerror(errno));
206 			case FTS_DP:		/* already seen dir */
207 				continue;
208 			}
209 			mapfileino(entry->fts_statp->st_ino, tapesize,
210 			    &anydirskipped);
211 		}
212 		(void)fts_close(dirh);
213 
214 		/*
215 		 * Add any parent directories
216 		 */
217 		for (d = 0 ; dirv[d] != NULL ; d++) {
218 			char path[MAXPATHLEN];
219 
220 			if (dirv[d][0] != '/')
221 				(void)snprintf(path, sizeof(path), "%s/%s",
222 				    curdir, dirv[d]);
223 			else
224 				(void)snprintf(path, sizeof(path), "%s",
225 				    dirv[d]);
226 			while (strcmp(path, disk) != 0) {
227 				char *p;
228 				struct stat sb;
229 
230 				if (*path == '\0')
231 					break;
232 				if ((p = strrchr(path, '/')) == NULL)
233 					break;
234 				if (p == path)
235 					break;
236 				*p = '\0';
237 				if (stat(path, &sb) == -1) {
238 					msg("Can't stat %s: %s\n", path,
239 					    strerror(errno));
240 					break;
241 				}
242 				mapfileino(sb.st_ino, tapesize, &anydirskipped);
243 			}
244 		}
245 
246 		/*
247 		 * Ensure that the root inode actually appears in the
248 		 * file list for a subdir
249 		 */
250 		mapfileino(ROOTINO, tapesize, &anydirskipped);
251 	} else {
252 		ino_t ino;
253 
254 		for (ino = ROOTINO; ino < maxino; ino++) {
255 			mapfileino(ino, tapesize, &anydirskipped);
256 		}
257 	}
258 	/*
259 	 * Restore gets very upset if the root is not dumped,
260 	 * so ensure that it always is dumped.
261 	 */
262 	SETINO(ROOTINO, dumpinomap);
263 	return (anydirskipped);
264 }
265 
266 /*
267  * Dump pass 2.
268  *
269  * Scan each directory on the filesystem to see if it has any modified
270  * files in it. If it does, and has not already been added to the dump
271  * list (because it was itself modified), then add it. If a directory
272  * has not been modified itself, contains no modified files and has no
273  * subdirectories, then it can be deleted from the dump list and from
274  * the list of directories. By deleting it from the list of directories,
275  * its parent may now qualify for the same treatment on this or a later
276  * pass using this algorithm.
277  */
278 int
279 mapdirs(maxino, tapesize)
280 	ino_t maxino;
281 	long *tapesize;
282 {
283 	struct	dinode *dp;
284 	int i, isdir;
285 	char *map;
286 	ino_t ino;
287 	long filesize;
288 	int ret, change = 0;
289 
290 	isdir = 0;		/* XXX just to get gcc to shut up */
291 	for (map = dumpdirmap, ino = 1; ino < maxino; ino++) {
292 		if (((ino - 1) % NBBY) == 0)	/* map is offset by 1 */
293 			isdir = *map++;
294 		else
295 			isdir >>= 1;
296 		if ((isdir & 1) == 0 || TSTINO(ino, dumpinomap))
297 			continue;
298 		dp = getino(ino);
299 		filesize = dp->di_size;
300 		for (ret = 0, i = 0; filesize > 0 && i < NDADDR; i++) {
301 			if (dp->di_db[i] != 0)
302 				ret |= searchdir(ino, dp->di_db[i],
303 					(long)dblksize(sblock, dp, i),
304 					filesize);
305 			if (ret & HASDUMPEDFILE)
306 				filesize = 0;
307 			else
308 				filesize -= sblock->fs_bsize;
309 		}
310 		for (i = 0; filesize > 0 && i < NIADDR; i++) {
311 			if (dp->di_ib[i] == 0)
312 				continue;
313 			ret |= dirindir(ino, dp->di_ib[i], i, &filesize);
314 		}
315 		if (ret & HASDUMPEDFILE) {
316 			SETINO(ino, dumpinomap);
317 			*tapesize += blockest(dp);
318 			change = 1;
319 			continue;
320 		}
321 		if ((ret & HASSUBDIRS) == 0) {
322 			if (!TSTINO(ino, dumpinomap)) {
323 				CLRINO(ino, dumpdirmap);
324 				change = 1;
325 			}
326 		}
327 	}
328 	return (change);
329 }
330 
331 /*
332  * Read indirect blocks, and pass the data blocks to be searched
333  * as directories. Quit as soon as any entry is found that will
334  * require the directory to be dumped.
335  */
336 static int
337 dirindir(ino, blkno, ind_level, filesize)
338 	ino_t ino;
339 	daddr_t blkno;
340 	int ind_level;
341 	long *filesize;
342 {
343 	int ret = 0;
344 	int i;
345 	daddr_t	idblk[MAXNINDIR];
346 
347 	bread(fsbtodb(sblock, blkno), (char *)idblk, (int)sblock->fs_bsize);
348 	if (ind_level <= 0) {
349 		for (i = 0; *filesize > 0 && i < NINDIR(sblock); i++) {
350 			blkno = idblk[i];
351 			if (blkno != 0)
352 				ret |= searchdir(ino, blkno, sblock->fs_bsize,
353 					*filesize);
354 			if (ret & HASDUMPEDFILE)
355 				*filesize = 0;
356 			else
357 				*filesize -= sblock->fs_bsize;
358 		}
359 		return (ret);
360 	}
361 	ind_level--;
362 	for (i = 0; *filesize > 0 && i < NINDIR(sblock); i++) {
363 		blkno = idblk[i];
364 		if (blkno != 0)
365 			ret |= dirindir(ino, blkno, ind_level, filesize);
366 	}
367 	return (ret);
368 }
369 
370 /*
371  * Scan a disk block containing directory information looking to see if
372  * any of the entries are on the dump list and to see if the directory
373  * contains any subdirectories.
374  */
375 static int
376 searchdir(ino, blkno, size, filesize)
377 	ino_t ino;
378 	daddr_t blkno;
379 	long size;
380 	long filesize;
381 {
382 	struct direct *dp;
383 	long loc, ret = 0;
384 	char dblk[MAXBSIZE];
385 
386 	bread(fsbtodb(sblock, blkno), dblk, (int)size);
387 	if (filesize < size)
388 		size = filesize;
389 	for (loc = 0; loc < size; ) {
390 		dp = (struct direct *)(dblk + loc);
391 		if (dp->d_reclen == 0) {
392 			msg("corrupted directory, inumber %d\n", ino);
393 			break;
394 		}
395 		loc += dp->d_reclen;
396 		if (dp->d_ino == 0)
397 			continue;
398 		if (dp->d_name[0] == '.') {
399 			if (dp->d_name[1] == '\0')
400 				continue;
401 			if (dp->d_name[1] == '.' && dp->d_name[2] == '\0')
402 				continue;
403 		}
404 		if (TSTINO(dp->d_ino, dumpinomap)) {
405 			ret |= HASDUMPEDFILE;
406 			if (ret & HASSUBDIRS)
407 				break;
408 		}
409 		if (TSTINO(dp->d_ino, dumpdirmap)) {
410 			ret |= HASSUBDIRS;
411 			if (ret & HASDUMPEDFILE)
412 				break;
413 		}
414 	}
415 	return (ret);
416 }
417 
418 /*
419  * Dump passes 3 and 4.
420  *
421  * Dump the contents of an inode to tape.
422  */
423 void
424 dumpino(dp, ino)
425 	struct dinode *dp;
426 	ino_t ino;
427 {
428 	int ind_level, cnt;
429 	fsizeT size;
430 	char buf[TP_BSIZE];
431 
432 	if (newtape) {
433 		newtape = 0;
434 		dumpmap(dumpinomap, TS_BITS, ino);
435 	}
436 	CLRINO(ino, dumpinomap);
437 	spcl.c_dinode = *dp;
438 	spcl.c_type = TS_INODE;
439 	spcl.c_count = 0;
440 	switch (dp->di_mode & IFMT) {
441 
442 	case 0:
443 		/*
444 		 * Freed inode.
445 		 */
446 		return;
447 
448 	case IFLNK:
449 		/*
450 		 * Check for short symbolic link.
451 		 */
452 		if (dp->di_size > 0 &&
453 #ifdef FS_44INODEFMT
454 		    (dp->di_size < sblock->fs_maxsymlinklen ||
455 		     (sblock->fs_maxsymlinklen == 0 && dp->di_blocks == 0))) {
456 #else
457 		    dp->di_blocks == 0) {
458 #endif
459 			spcl.c_addr[0] = 1;
460 			spcl.c_count = 1;
461 			writeheader(ino);
462 			memcpy(buf, dp->di_shortlink, (u_long)dp->di_size);
463 			buf[dp->di_size] = '\0';
464 			writerec(buf, 0);
465 			return;
466 		}
467 		/* fall through */
468 
469 	case IFDIR:
470 	case IFREG:
471 		if (dp->di_size > 0)
472 			break;
473 		/* fall through */
474 
475 	case IFIFO:
476 	case IFSOCK:
477 	case IFCHR:
478 	case IFBLK:
479 		writeheader(ino);
480 		return;
481 
482 	default:
483 		msg("Warning: undefined file type 0%o\n", dp->di_mode & IFMT);
484 		return;
485 	}
486 	if (dp->di_size > NDADDR * sblock->fs_bsize)
487 		cnt = NDADDR * sblock->fs_frag;
488 	else
489 		cnt = howmany(dp->di_size, sblock->fs_fsize);
490 	blksout(&dp->di_db[0], cnt, ino);
491 	if ((size = dp->di_size - NDADDR * sblock->fs_bsize) <= 0)
492 		return;
493 	for (ind_level = 0; ind_level < NIADDR; ind_level++) {
494 		dmpindir(ino, dp->di_ib[ind_level], ind_level, &size);
495 		if (size <= 0)
496 			return;
497 	}
498 }
499 
500 /*
501  * Read indirect blocks, and pass the data blocks to be dumped.
502  */
503 static void
504 dmpindir(ino, blk, ind_level, size)
505 	ino_t ino;
506 	daddr_t blk;
507 	int ind_level;
508 	fsizeT *size;
509 {
510 	int i, cnt;
511 	daddr_t idblk[MAXNINDIR];
512 
513 	if (blk != 0)
514 		bread(fsbtodb(sblock, blk), (char *)idblk, (int) sblock->fs_bsize);
515 	else
516 		memset(idblk, 0, (int)sblock->fs_bsize);
517 	if (ind_level <= 0) {
518 		if (*size < NINDIR(sblock) * sblock->fs_bsize)
519 			cnt = howmany(*size, sblock->fs_fsize);
520 		else
521 			cnt = NINDIR(sblock) * sblock->fs_frag;
522 		*size -= NINDIR(sblock) * sblock->fs_bsize;
523 		blksout(&idblk[0], cnt, ino);
524 		return;
525 	}
526 	ind_level--;
527 	for (i = 0; i < NINDIR(sblock); i++) {
528 		dmpindir(ino, idblk[i], ind_level, size);
529 		if (*size <= 0)
530 			return;
531 	}
532 }
533 
534 /*
535  * Collect up the data into tape record sized buffers and output them.
536  */
537 void
538 blksout(blkp, frags, ino)
539 	daddr_t *blkp;
540 	int frags;
541 	ino_t ino;
542 {
543 	daddr_t *bp;
544 	int i, j, count, blks, tbperdb;
545 
546 	blks = howmany(frags * sblock->fs_fsize, TP_BSIZE);
547 	tbperdb = sblock->fs_bsize >> tp_bshift;
548 	for (i = 0; i < blks; i += TP_NINDIR) {
549 		if (i + TP_NINDIR > blks)
550 			count = blks;
551 		else
552 			count = i + TP_NINDIR;
553 		for (j = i; j < count; j++)
554 			if (blkp[j / tbperdb] != 0)
555 				spcl.c_addr[j - i] = 1;
556 			else
557 				spcl.c_addr[j - i] = 0;
558 		spcl.c_count = count - i;
559 		writeheader(ino);
560 		bp = &blkp[i / tbperdb];
561 		for (j = i; j < count; j += tbperdb, bp++)
562 			if (*bp != 0)
563 				if (j + tbperdb <= count)
564 					dumpblock(*bp, (int)sblock->fs_bsize);
565 				else
566 					dumpblock(*bp, (count - j) * TP_BSIZE);
567 		spcl.c_type = TS_ADDR;
568 	}
569 }
570 
571 /*
572  * Dump a map to the tape.
573  */
574 void
575 dumpmap(map, type, ino)
576 	char *map;
577 	int type;
578 	ino_t ino;
579 {
580 	int i;
581 	char *cp;
582 
583 	spcl.c_type = type;
584 	spcl.c_count = howmany(mapsize * sizeof(char), TP_BSIZE);
585 	writeheader(ino);
586 	for (i = 0, cp = map; i < spcl.c_count; i++, cp += TP_BSIZE)
587 		writerec(cp, 0);
588 }
589 
590 /*
591  * Write a header record to the dump tape.
592  */
593 void
594 writeheader(ino)
595 	ino_t ino;
596 {
597 	int32_t sum, cnt, *lp;
598 
599 	spcl.c_inumber = ino;
600 	spcl.c_magic = NFS_MAGIC;
601 	spcl.c_checksum = 0;
602 	lp = (int32_t *)&spcl;
603 	sum = 0;
604 	cnt = sizeof(union u_spcl) / (4 * sizeof(int32_t));
605 	while (--cnt >= 0) {
606 		sum += *lp++;
607 		sum += *lp++;
608 		sum += *lp++;
609 		sum += *lp++;
610 	}
611 	spcl.c_checksum = CHECKSUM - sum;
612 	writerec((char *)&spcl, 1);
613 }
614 
615 struct dinode *
616 getino(inum)
617 	ino_t inum;
618 {
619 	static daddr_t minino, maxino;
620 	static struct dinode inoblock[MAXINOPB];
621 
622 	curino = inum;
623 	if (inum >= minino && inum < maxino)
624 		return (&inoblock[inum - minino]);
625 	bread(fsbtodb(sblock, ino_to_fsba(sblock, inum)), (char *)inoblock,
626 	    (int)sblock->fs_bsize);
627 	minino = inum - (inum % INOPB(sblock));
628 	maxino = minino + INOPB(sblock);
629 	return (&inoblock[inum - minino]);
630 }
631 
632 /*
633  * Read a chunk of data from the disk.
634  * Try to recover from hard errors by reading in sector sized pieces.
635  * Error recovery is attempted at most BREADEMAX times before seeking
636  * consent from the operator to continue.
637  */
638 int	breaderrors = 0;
639 #define	BREADEMAX 32
640 
641 void
642 bread(blkno, buf, size)
643 	daddr_t blkno;
644 	char *buf;
645 	int size;
646 {
647 	int cnt, i;
648 	extern int errno;
649 
650 loop:
651 	if (lseek(diskfd, ((off_t)blkno << dev_bshift), 0) < 0)
652 		msg("bread: lseek fails\n");
653 	if ((cnt = read(diskfd, buf, size)) == size)
654 		return;
655 	if (blkno + (size / dev_bsize) > fsbtodb(sblock, sblock->fs_size)) {
656 		/*
657 		 * Trying to read the final fragment.
658 		 *
659 		 * NB - dump only works in TP_BSIZE blocks, hence
660 		 * rounds `dev_bsize' fragments up to TP_BSIZE pieces.
661 		 * It should be smarter about not actually trying to
662 		 * read more than it can get, but for the time being
663 		 * we punt and scale back the read only when it gets
664 		 * us into trouble. (mkm 9/25/83)
665 		 */
666 		size -= dev_bsize;
667 		goto loop;
668 	}
669 	if (cnt == -1)
670 		msg("read error from %s: %s: [block %d]: count=%d\n",
671 			disk, strerror(errno), blkno, size);
672 	else
673 		msg("short read error from %s: [block %d]: count=%d, got=%d\n",
674 			disk, blkno, size, cnt);
675 	if (++breaderrors > BREADEMAX) {
676 		msg("More than %d block read errors from %d\n",
677 			BREADEMAX, disk);
678 		broadcast("DUMP IS AILING!\n");
679 		msg("This is an unrecoverable error.\n");
680 		if (!query("Do you want to attempt to continue?")){
681 			dumpabort(0);
682 			/*NOTREACHED*/
683 		} else
684 			breaderrors = 0;
685 	}
686 	/*
687 	 * Zero buffer, then try to read each sector of buffer separately.
688 	 */
689 	memset(buf, 0, size);
690 	for (i = 0; i < size; i += dev_bsize, buf += dev_bsize, blkno++) {
691 		if (lseek(diskfd, ((off_t)blkno << dev_bshift), 0) < 0)
692 			msg("bread: lseek2 fails!\n");
693 		if ((cnt = read(diskfd, buf, (int)dev_bsize)) == dev_bsize)
694 			continue;
695 		if (cnt == -1) {
696 			msg("read error from %s: %s: [sector %d]: count=%d\n",
697 				disk, strerror(errno), blkno, dev_bsize);
698 			continue;
699 		}
700 		msg("short read error from %s: [sector %d]: count=%d, got=%d\n",
701 			disk, blkno, dev_bsize, cnt);
702 	}
703 }
704