xref: /netbsd-src/sys/ufs/ext2fs/ext2fs_alloc.c (revision aaf4ece63a859a04e37cf3a7229b5fab0157cc06)
1 /*	$NetBSD: ext2fs_alloc.c,v 1.28 2005/12/11 12:25:25 christos Exp $	*/
2 
3 /*
4  * Copyright (c) 1982, 1986, 1989, 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. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  *	@(#)ffs_alloc.c	8.11 (Berkeley) 10/27/94
32  *  Modified for ext2fs by Manuel Bouyer.
33  */
34 
35 /*
36  * Copyright (c) 1997 Manuel Bouyer.
37  *
38  * Redistribution and use in source and binary forms, with or without
39  * modification, are permitted provided that the following conditions
40  * are met:
41  * 1. Redistributions of source code must retain the above copyright
42  *    notice, this list of conditions and the following disclaimer.
43  * 2. Redistributions in binary form must reproduce the above copyright
44  *    notice, this list of conditions and the following disclaimer in the
45  *    documentation and/or other materials provided with the distribution.
46  * 3. All advertising materials mentioning features or use of this software
47  *    must display the following acknowledgement:
48  *	This product includes software developed by Manuel Bouyer.
49  * 4. The name of the author may not be used to endorse or promote products
50  *    derived from this software without specific prior written permission.
51  *
52  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
53  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
54  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
55  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
56  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
57  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
58  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
59  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
60  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
61  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
62  *
63  *	@(#)ffs_alloc.c	8.11 (Berkeley) 10/27/94
64  *  Modified for ext2fs by Manuel Bouyer.
65  */
66 
67 #include <sys/cdefs.h>
68 __KERNEL_RCSID(0, "$NetBSD: ext2fs_alloc.c,v 1.28 2005/12/11 12:25:25 christos Exp $");
69 
70 #include <sys/param.h>
71 #include <sys/systm.h>
72 #include <sys/buf.h>
73 #include <sys/proc.h>
74 #include <sys/vnode.h>
75 #include <sys/mount.h>
76 #include <sys/kernel.h>
77 #include <sys/syslog.h>
78 
79 #include <ufs/ufs/inode.h>
80 #include <ufs/ufs/ufs_extern.h>
81 #include <ufs/ufs/ufsmount.h>
82 
83 #include <ufs/ext2fs/ext2fs.h>
84 #include <ufs/ext2fs/ext2fs_extern.h>
85 
86 u_long ext2gennumber;
87 
88 static daddr_t	ext2fs_alloccg(struct inode *, int, daddr_t, int);
89 static u_long	ext2fs_dirpref(struct m_ext2fs *);
90 static void	ext2fs_fserr(struct m_ext2fs *, u_int, const char *);
91 static u_long	ext2fs_hashalloc(struct inode *, int, long, int,
92 				   daddr_t (*)(struct inode *, int, daddr_t,
93 						   int));
94 static daddr_t	ext2fs_nodealloccg(struct inode *, int, daddr_t, int);
95 static daddr_t	ext2fs_mapsearch(struct m_ext2fs *, char *, daddr_t);
96 
97 /*
98  * Allocate a block in the file system.
99  *
100  * A preference may be optionally specified. If a preference is given
101  * the following hierarchy is used to allocate a block:
102  *   1) allocate the requested block.
103  *   2) allocate a rotationally optimal block in the same cylinder.
104  *   3) allocate a block in the same cylinder group.
105  *   4) quadradically rehash into other cylinder groups, until an
106  *	  available block is located.
107  * If no block preference is given the following hierarchy is used
108  * to allocate a block:
109  *   1) allocate a block in the cylinder group that contains the
110  *	  inode for the file.
111  *   2) quadradically rehash into other cylinder groups, until an
112  *	  available block is located.
113  */
114 int
115 ext2fs_alloc(struct inode *ip, daddr_t lbn, daddr_t bpref, struct ucred *cred,
116 		daddr_t *bnp)
117 {
118 	struct m_ext2fs *fs;
119 	daddr_t bno;
120 	int cg;
121 
122 	*bnp = 0;
123 	fs = ip->i_e2fs;
124 #ifdef DIAGNOSTIC
125 	if (cred == NOCRED)
126 		panic("ext2fs_alloc: missing credential");
127 #endif /* DIAGNOSTIC */
128 	if (fs->e2fs.e2fs_fbcount == 0)
129 		goto nospace;
130 	if (cred->cr_uid != 0 && freespace(fs) <= 0)
131 		goto nospace;
132 	if (bpref >= fs->e2fs.e2fs_bcount)
133 		bpref = 0;
134 	if (bpref == 0)
135 		cg = ino_to_cg(fs, ip->i_number);
136 	else
137 		cg = dtog(fs, bpref);
138 	bno = (daddr_t)ext2fs_hashalloc(ip, cg, bpref, fs->e2fs_bsize,
139 						 ext2fs_alloccg);
140 	if (bno > 0) {
141 		ip->i_e2fs_nblock += btodb(fs->e2fs_bsize);
142 		ip->i_flag |= IN_CHANGE | IN_UPDATE;
143 		*bnp = bno;
144 		return (0);
145 	}
146 nospace:
147 	ext2fs_fserr(fs, cred->cr_uid, "file system full");
148 	uprintf("\n%s: write failed, file system is full\n", fs->e2fs_fsmnt);
149 	return (ENOSPC);
150 }
151 
152 /*
153  * Allocate an inode in the file system.
154  *
155  * If allocating a directory, use ext2fs_dirpref to select the inode.
156  * If allocating in a directory, the following hierarchy is followed:
157  *   1) allocate the preferred inode.
158  *   2) allocate an inode in the same cylinder group.
159  *   3) quadradically rehash into other cylinder groups, until an
160  *	  available inode is located.
161  * If no inode preference is given the following hierarchy is used
162  * to allocate an inode:
163  *   1) allocate an inode in cylinder group 0.
164  *   2) quadradically rehash into other cylinder groups, until an
165  *	  available inode is located.
166  */
167 int
168 ext2fs_valloc(struct vnode *pvp, int mode, struct ucred *cred,
169     struct vnode **vpp)
170 {
171 	struct inode *pip;
172 	struct m_ext2fs *fs;
173 	struct inode *ip;
174 	ino_t ino, ipref;
175 	int cg, error;
176 
177 	*vpp = NULL;
178 	pip = VTOI(pvp);
179 	fs = pip->i_e2fs;
180 	if (fs->e2fs.e2fs_ficount == 0)
181 		goto noinodes;
182 
183 	if ((mode & IFMT) == IFDIR)
184 		cg = ext2fs_dirpref(fs);
185 	else
186 		cg = ino_to_cg(fs, pip->i_number);
187 	ipref = cg * fs->e2fs.e2fs_ipg + 1;
188 	ino = (ino_t)ext2fs_hashalloc(pip, cg, (long)ipref, mode, ext2fs_nodealloccg);
189 	if (ino == 0)
190 		goto noinodes;
191 	error = VFS_VGET(pvp->v_mount, ino, vpp);
192 	if (error) {
193 		ext2fs_vfree(pvp, ino, mode);
194 		return (error);
195 	}
196 	ip = VTOI(*vpp);
197 	if (ip->i_e2fs_mode && ip->i_e2fs_nlink != 0) {
198 		printf("mode = 0%o, nlinks %d, inum = %llu, fs = %s\n",
199 		    ip->i_e2fs_mode, ip->i_e2fs_nlink,
200 		    (unsigned long long)ip->i_number, fs->e2fs_fsmnt);
201 		panic("ext2fs_valloc: dup alloc");
202 	}
203 
204 	memset(ip->i_din.e2fs_din, 0, sizeof(struct ext2fs_dinode));
205 
206 	/*
207 	 * Set up a new generation number for this inode.
208 	 */
209 	if (++ext2gennumber < (u_long)time.tv_sec)
210 		ext2gennumber = time.tv_sec;
211 	ip->i_e2fs_gen = ext2gennumber;
212 	return (0);
213 noinodes:
214 	ext2fs_fserr(fs, cred->cr_uid, "out of inodes");
215 	uprintf("\n%s: create/symlink failed, no inodes free\n", fs->e2fs_fsmnt);
216 	return (ENOSPC);
217 }
218 
219 /*
220  * Find a cylinder to place a directory.
221  *
222  * The policy implemented by this algorithm is to select from
223  * among those cylinder groups with above the average number of
224  * free inodes, the one with the smallest number of directories.
225  */
226 static u_long
227 ext2fs_dirpref(struct m_ext2fs *fs)
228 {
229 	int cg, maxspace, mincg, avgifree;
230 
231 	avgifree = fs->e2fs.e2fs_ficount / fs->e2fs_ncg;
232 	maxspace = 0;
233 	mincg = -1;
234 	for (cg = 0; cg < fs->e2fs_ncg; cg++)
235 		if ( fs->e2fs_gd[cg].ext2bgd_nifree >= avgifree) {
236 			if (mincg == -1 || fs->e2fs_gd[cg].ext2bgd_nbfree > maxspace) {
237 				mincg = cg;
238 				maxspace = fs->e2fs_gd[cg].ext2bgd_nbfree;
239 			}
240 		}
241 	return mincg;
242 }
243 
244 /*
245  * Select the desired position for the next block in a file.  The file is
246  * logically divided into sections. The first section is composed of the
247  * direct blocks. Each additional section contains fs_maxbpg blocks.
248  *
249  * If no blocks have been allocated in the first section, the policy is to
250  * request a block in the same cylinder group as the inode that describes
251  * the file. Otherwise, the policy is to try to allocate the blocks
252  * contigously. The two fields of the ext2 inode extension (see
253  * ufs/ufs/inode.h) help this.
254  */
255 daddr_t
256 ext2fs_blkpref(struct inode *ip, daddr_t lbn, int indx,
257 		int32_t *bap /* XXX ondisk32 */)
258 {
259 	struct m_ext2fs *fs;
260 	int cg, i;
261 
262 	fs = ip->i_e2fs;
263 	/*
264 	 * if we are doing contigous lbn allocation, try to alloc blocks
265 	 * contigously on disk
266 	 */
267 
268 	if ( ip->i_e2fs_last_blk && lbn == ip->i_e2fs_last_lblk + 1) {
269 		return ip->i_e2fs_last_blk + 1;
270 	}
271 
272 	/*
273 	 * bap, if provided, gives us a list of blocks to which we want to
274 	 * stay close
275 	 */
276 
277 	if (bap) {
278 		for (i = indx; i >= 0 ; i--) {
279 			if (bap[i]) {
280 				return fs2h32(bap[i]) + 1;
281 			}
282 		}
283 	}
284 
285 	/* fall back to the first block of the cylinder containing the inode */
286 
287 	cg = ino_to_cg(fs, ip->i_number);
288 	return fs->e2fs.e2fs_bpg * cg + fs->e2fs.e2fs_first_dblock + 1;
289 }
290 
291 /*
292  * Implement the cylinder overflow algorithm.
293  *
294  * The policy implemented by this algorithm is:
295  *   1) allocate the block in its requested cylinder group.
296  *   2) quadradically rehash on the cylinder group number.
297  *   3) brute force search for a free block.
298  */
299 static u_long
300 ext2fs_hashalloc(struct inode *ip, int cg, long pref, int size,
301 		daddr_t (*allocator)(struct inode *, int, daddr_t, int))
302 {
303 	struct m_ext2fs *fs;
304 	long result;
305 	int i, icg = cg;
306 
307 	fs = ip->i_e2fs;
308 	/*
309 	 * 1: preferred cylinder group
310 	 */
311 	result = (*allocator)(ip, cg, pref, size);
312 	if (result)
313 		return (result);
314 	/*
315 	 * 2: quadratic rehash
316 	 */
317 	for (i = 1; i < fs->e2fs_ncg; i *= 2) {
318 		cg += i;
319 		if (cg >= fs->e2fs_ncg)
320 			cg -= fs->e2fs_ncg;
321 		result = (*allocator)(ip, cg, 0, size);
322 		if (result)
323 			return (result);
324 	}
325 	/*
326 	 * 3: brute force search
327 	 * Note that we start at i == 2, since 0 was checked initially,
328 	 * and 1 is always checked in the quadratic rehash.
329 	 */
330 	cg = (icg + 2) % fs->e2fs_ncg;
331 	for (i = 2; i < fs->e2fs_ncg; i++) {
332 		result = (*allocator)(ip, cg, 0, size);
333 		if (result)
334 			return (result);
335 		cg++;
336 		if (cg == fs->e2fs_ncg)
337 			cg = 0;
338 	}
339 	return (0);
340 }
341 
342 /*
343  * Determine whether a block can be allocated.
344  *
345  * Check to see if a block of the appropriate size is available,
346  * and if it is, allocate it.
347  */
348 
349 static daddr_t
350 ext2fs_alloccg(struct inode *ip, int cg, daddr_t bpref, int size)
351 {
352 	struct m_ext2fs *fs;
353 	char *bbp;
354 	struct buf *bp;
355 	/* XXX ondisk32 */
356 	int error, bno, start, end, loc;
357 
358 	fs = ip->i_e2fs;
359 	if (fs->e2fs_gd[cg].ext2bgd_nbfree == 0)
360 		return (0);
361 	error = bread(ip->i_devvp, fsbtodb(fs,
362 		fs->e2fs_gd[cg].ext2bgd_b_bitmap),
363 		(int)fs->e2fs_bsize, NOCRED, &bp);
364 	if (error) {
365 		brelse(bp);
366 		return (0);
367 	}
368 	bbp = (char *)bp->b_data;
369 
370 	if (dtog(fs, bpref) != cg)
371 		bpref = 0;
372 	if (bpref != 0) {
373 		bpref = dtogd(fs, bpref);
374 		/*
375 		 * if the requested block is available, use it
376 		 */
377 		if (isclr(bbp, bpref)) {
378 			bno = bpref;
379 			goto gotit;
380 		}
381 	}
382 	/*
383 	 * no blocks in the requested cylinder, so take next
384 	 * available one in this cylinder group.
385 	 * first try to get 8 contigous blocks, then fall back to a single
386 	 * block.
387 	 */
388 	if (bpref)
389 		start = dtogd(fs, bpref) / NBBY;
390 	else
391 		start = 0;
392 	end = howmany(fs->e2fs.e2fs_fpg, NBBY) - start;
393 	for (loc = start; loc < end; loc++) {
394 		if (bbp[loc] == 0) {
395 			bno = loc * NBBY;
396 			goto gotit;
397 		}
398 	}
399 	for (loc = 0; loc < start; loc++) {
400 		if (bbp[loc] == 0) {
401 			bno = loc * NBBY;
402 			goto gotit;
403 		}
404 	}
405 
406 	bno = ext2fs_mapsearch(fs, bbp, bpref);
407 	if (bno < 0)
408 		return (0);
409 gotit:
410 #ifdef DIAGNOSTIC
411 	if (isset(bbp, (daddr_t)bno)) {
412 		printf("ext2fs_alloccgblk: cg=%d bno=%d fs=%s\n",
413 			cg, bno, fs->e2fs_fsmnt);
414 		panic("ext2fs_alloccg: dup alloc");
415 	}
416 #endif
417 	setbit(bbp, (daddr_t)bno);
418 	fs->e2fs.e2fs_fbcount--;
419 	fs->e2fs_gd[cg].ext2bgd_nbfree--;
420 	fs->e2fs_fmod = 1;
421 	bdwrite(bp);
422 	return (cg * fs->e2fs.e2fs_fpg + fs->e2fs.e2fs_first_dblock + bno);
423 }
424 
425 /*
426  * Determine whether an inode can be allocated.
427  *
428  * Check to see if an inode is available, and if it is,
429  * allocate it using the following policy:
430  *   1) allocate the requested inode.
431  *   2) allocate the next available inode after the requested
432  *	  inode in the specified cylinder group.
433  */
434 static daddr_t
435 ext2fs_nodealloccg(struct inode *ip, int cg, daddr_t ipref, int mode)
436 {
437 	struct m_ext2fs *fs;
438 	char *ibp;
439 	struct buf *bp;
440 	int error, start, len, loc, map, i;
441 
442 	ipref--; /* to avoid a lot of (ipref -1) */
443 	fs = ip->i_e2fs;
444 	if (fs->e2fs_gd[cg].ext2bgd_nifree == 0)
445 		return (0);
446 	error = bread(ip->i_devvp, fsbtodb(fs,
447 		fs->e2fs_gd[cg].ext2bgd_i_bitmap),
448 		(int)fs->e2fs_bsize, NOCRED, &bp);
449 	if (error) {
450 		brelse(bp);
451 		return (0);
452 	}
453 	ibp = (char *)bp->b_data;
454 	if (ipref) {
455 		ipref %= fs->e2fs.e2fs_ipg;
456 		if (isclr(ibp, ipref))
457 			goto gotit;
458 	}
459 	start = ipref / NBBY;
460 	len = howmany(fs->e2fs.e2fs_ipg - ipref, NBBY);
461 	loc = skpc(0xff, len, &ibp[start]);
462 	if (loc == 0) {
463 		len = start + 1;
464 		start = 0;
465 		loc = skpc(0xff, len, &ibp[0]);
466 		if (loc == 0) {
467 			printf("cg = %d, ipref = %lld, fs = %s\n",
468 				cg, (long long)ipref, fs->e2fs_fsmnt);
469 			panic("ext2fs_nodealloccg: map corrupted");
470 			/* NOTREACHED */
471 		}
472 	}
473 	i = start + len - loc;
474 	map = ibp[i];
475 	ipref = i * NBBY;
476 	for (i = 1; i < (1 << NBBY); i <<= 1, ipref++) {
477 		if ((map & i) == 0) {
478 			goto gotit;
479 		}
480 	}
481 	printf("fs = %s\n", fs->e2fs_fsmnt);
482 	panic("ext2fs_nodealloccg: block not in map");
483 	/* NOTREACHED */
484 gotit:
485 	setbit(ibp, ipref);
486 	fs->e2fs.e2fs_ficount--;
487 	fs->e2fs_gd[cg].ext2bgd_nifree--;
488 	fs->e2fs_fmod = 1;
489 	if ((mode & IFMT) == IFDIR) {
490 		fs->e2fs_gd[cg].ext2bgd_ndirs++;
491 	}
492 	bdwrite(bp);
493 	return (cg * fs->e2fs.e2fs_ipg + ipref +1);
494 }
495 
496 /*
497  * Free a block.
498  *
499  * The specified block is placed back in the
500  * free map.
501  */
502 void
503 ext2fs_blkfree(struct inode *ip, daddr_t bno)
504 {
505 	struct m_ext2fs *fs;
506 	char *bbp;
507 	struct buf *bp;
508 	int error, cg;
509 
510 	fs = ip->i_e2fs;
511 	cg = dtog(fs, bno);
512 	if ((u_int)bno >= fs->e2fs.e2fs_bcount) {
513 		printf("bad block %lld, ino %llu\n", (long long)bno,
514 		    (unsigned long long)ip->i_number);
515 		ext2fs_fserr(fs, ip->i_e2fs_uid, "bad block");
516 		return;
517 	}
518 	error = bread(ip->i_devvp,
519 		fsbtodb(fs, fs->e2fs_gd[cg].ext2bgd_b_bitmap),
520 		(int)fs->e2fs_bsize, NOCRED, &bp);
521 	if (error) {
522 		brelse(bp);
523 		return;
524 	}
525 	bbp = (char *)bp->b_data;
526 	bno = dtogd(fs, bno);
527 	if (isclr(bbp, bno)) {
528 		printf("dev = 0x%x, block = %lld, fs = %s\n",
529 			ip->i_dev, (long long)bno, fs->e2fs_fsmnt);
530 		panic("blkfree: freeing free block");
531 	}
532 	clrbit(bbp, bno);
533 	fs->e2fs.e2fs_fbcount++;
534 	fs->e2fs_gd[cg].ext2bgd_nbfree++;
535 
536 	fs->e2fs_fmod = 1;
537 	bdwrite(bp);
538 }
539 
540 /*
541  * Free an inode.
542  *
543  * The specified inode is placed back in the free map.
544  */
545 int
546 ext2fs_vfree(struct vnode *pvp, ino_t ino, int mode)
547 {
548 	struct m_ext2fs *fs;
549 	char *ibp;
550 	struct inode *pip;
551 	struct buf *bp;
552 	int error, cg;
553 
554 	pip = VTOI(pvp);
555 	fs = pip->i_e2fs;
556 	if ((u_int)ino >= fs->e2fs.e2fs_icount || (u_int)ino < EXT2_FIRSTINO)
557 		panic("ifree: range: dev = 0x%x, ino = %llu, fs = %s",
558 			pip->i_dev, (unsigned long long)ino, fs->e2fs_fsmnt);
559 	cg = ino_to_cg(fs, ino);
560 	error = bread(pip->i_devvp,
561 		fsbtodb(fs, fs->e2fs_gd[cg].ext2bgd_i_bitmap),
562 		(int)fs->e2fs_bsize, NOCRED, &bp);
563 	if (error) {
564 		brelse(bp);
565 		return (0);
566 	}
567 	ibp = (char *)bp->b_data;
568 	ino = (ino - 1) % fs->e2fs.e2fs_ipg;
569 	if (isclr(ibp, ino)) {
570 		printf("dev = 0x%x, ino = %llu, fs = %s\n",
571 		    pip->i_dev, (unsigned long long)ino, fs->e2fs_fsmnt);
572 		if (fs->e2fs_ronly == 0)
573 			panic("ifree: freeing free inode");
574 	}
575 	clrbit(ibp, ino);
576 	fs->e2fs.e2fs_ficount++;
577 	fs->e2fs_gd[cg].ext2bgd_nifree++;
578 	if ((mode & IFMT) == IFDIR) {
579 		fs->e2fs_gd[cg].ext2bgd_ndirs--;
580 	}
581 	fs->e2fs_fmod = 1;
582 	bdwrite(bp);
583 	return (0);
584 }
585 
586 /*
587  * Find a block in the specified cylinder group.
588  *
589  * It is a panic if a request is made to find a block if none are
590  * available.
591  */
592 
593 static daddr_t
594 ext2fs_mapsearch(struct m_ext2fs *fs, char *bbp, daddr_t bpref)
595 {
596 	daddr_t bno;
597 	int start, len, loc, i, map;
598 
599 	/*
600 	 * find the fragment by searching through the free block
601 	 * map for an appropriate bit pattern
602 	 */
603 	if (bpref)
604 		start = dtogd(fs, bpref) / NBBY;
605 	else
606 		start = 0;
607 	len = howmany(fs->e2fs.e2fs_fpg, NBBY) - start;
608 	loc = skpc(0xff, len, &bbp[start]);
609 	if (loc == 0) {
610 		len = start + 1;
611 		start = 0;
612 		loc = skpc(0xff, len, &bbp[start]);
613 		if (loc == 0) {
614 			printf("start = %d, len = %d, fs = %s\n",
615 				start, len, fs->e2fs_fsmnt);
616 			panic("ext2fs_alloccg: map corrupted");
617 			/* NOTREACHED */
618 		}
619 	}
620 	i = start + len - loc;
621 	map = bbp[i];
622 	bno = i * NBBY;
623 	for (i = 1; i < (1 << NBBY); i <<= 1, bno++) {
624 		if ((map & i) == 0)
625 			return (bno);
626 	}
627 	printf("fs = %s\n", fs->e2fs_fsmnt);
628 	panic("ext2fs_mapsearch: block not in map");
629 	/* NOTREACHED */
630 }
631 
632 /*
633  * Fserr prints the name of a file system with an error diagnostic.
634  *
635  * The form of the error message is:
636  *	fs: error message
637  */
638 static void
639 ext2fs_fserr(struct m_ext2fs *fs, u_int uid, const char *cp)
640 {
641 
642 	log(LOG_ERR, "uid %d on %s: %s\n", uid, fs->e2fs_fsmnt, cp);
643 }
644