1/* $NetBSD: msdosfs_fat.c,v 1.31 2016/05/07 16:43:02 mlelstv Exp $ */
2
3/*-
4 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
5 * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
6 * All rights reserved.
7 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
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 TooLs GmbH.
20 * 4. The name of TooLs GmbH may not be used to endorse or promote products
21 * derived from this software without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
26 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
27 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
28 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
29 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
30 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
31 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
32 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
33 */
34/*
35 * Written by Paul Popelka (paulp@uts.amdahl.com)
36 *
37 * You can do anything you want with this software, just don't say you wrote
38 * it, and don't remove this notice.
39 *
40 * This software is provided "as is".
41 *
42 * The author supplies this software to be publicly redistributed on the
43 * understanding that the author is not responsible for the correct
44 * functioning of this software in any circumstances and is not liable for
45 * any damages caused by this software.
46 *
47 * October 1992
48 */
49
50#if HAVE_NBTOOL_CONFIG_H
51#include "nbtool_config.h"
52#endif
53
54#include <sys/cdefs.h>
55__KERNEL_RCSID(0, "$NetBSD: msdosfs_fat.c,v 1.31 2016/05/07 16:43:02 mlelstv Exp $");
56
57/*
58 * kernel include files.
59 */
60#include <sys/param.h>
61#include <sys/file.h>
62#ifdef _KERNEL
63#include <sys/mount.h> /* to define statvfs structure */
64#include <sys/errno.h>
65#include <sys/systm.h>
66#include <sys/kauth.h>
67#include <sys/dirent.h>
68#include <sys/namei.h>
69#include <sys/buf.h>
70#include <sys/vnode.h> /* to define vattr structure */
71#else
72#include <ffs/buf.h>
73#endif
74
75/*
76 * msdosfs include files.
77 */
78#include <fs/msdosfs/bpb.h>
79#include <fs/msdosfs/msdosfsmount.h>
80#include <fs/msdosfs/direntry.h>
81#include <fs/msdosfs/denode.h>
82#include <fs/msdosfs/fat.h>
83
84/*
85 * Fat cache stats.
86 */
87int fc_fileextends; /* # of file extends */
88int fc_lfcempty; /* # of time last file cluster cache entry
89 * was empty */
90int fc_bmapcalls; /* # of times pcbmap was called */
91
92#define LMMAX 20
93int fc_lmdistance[LMMAX]; /* counters for how far off the last
94 * cluster mapped entry was. */
95int fc_largedistance; /* off by more than LMMAX */
96int fc_wherefrom, fc_whereto, fc_lastclust;
97int pm_fatblocksize;
98
99#ifdef MSDOSFS_DEBUG
100#define DPRINTF(a) printf a
101#else
102#define DPRINTF(a)
103#endif
104#ifdef MSDOSFS_DEBUG
105void print_fat_stats(void);
106
107void
108print_fat_stats(void)
109{
110 int i;
111
112 printf("fc_fileextends=%d fc_lfcempty=%d fc_bmapcalls=%d "
113 "fc_largedistance=%d [%d->%d=%d] fc_lastclust=%d pm_fatblocksize=%d\n",
114 fc_fileextends, fc_lfcempty, fc_bmapcalls, fc_largedistance,
115 fc_wherefrom, fc_whereto, fc_whereto-fc_wherefrom,
116 fc_lastclust, pm_fatblocksize);
117
118 fc_fileextends = fc_lfcempty = fc_bmapcalls = 0;
119 fc_wherefrom = fc_whereto = fc_lastclust = 0;
120
121 for (i = 0; i < LMMAX; i++) {
122 printf("%d:%d ", i, fc_lmdistance[i]);
123 fc_lmdistance[i] = 0;
124 }
125
126 printf("\n");
127}
128#endif
129
130static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *,
131 u_long *);
132void updatefats(struct msdosfsmount *, struct buf *, u_long);
133static inline void usemap_free(struct msdosfsmount *, u_long);
134static inline void usemap_alloc(struct msdosfsmount *, u_long);
135static int fatchain(struct msdosfsmount *, u_long, u_long, u_long);
136int chainlength(struct msdosfsmount *, u_long, u_long);
137int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *,
138 u_long *);
139
140static void
141fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, u_long *bop)
142{
143 u_long bn, size;
144
145 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
146 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
147 * pmp->pm_BytesPerSec;
148 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
149
150 DPRINTF(("%s(ofs=%lu bn=%lu, size=%lu, bo=%lu)\n", __func__, ofs, bn,
151 size, ofs % pmp->pm_fatblocksize));
152 if (bnp)
153 *bnp = bn;
154 if (sizep)
155 *sizep = size;
156 if (bop)
157 *bop = ofs % pmp->pm_fatblocksize;
158
159 pm_fatblocksize = pmp->pm_fatblocksize;
160}
161
162/*
163 * Map the logical cluster number of a file into a physical disk sector
164 * that is filesystem relative.
165 *
166 * dep - address of denode representing the file of interest
167 * findcn - file relative cluster whose filesystem relative cluster number
168 * and/or block number are/is to be found
169 * bnp - address of where to place the file system relative block number.
170 * If this pointer is null then don't return this quantity.
171 * cnp - address of where to place the file system relative cluster number.
172 * If this pointer is null then don't return this quantity.
173 *
174 * NOTE: Either bnp or cnp must be non-null.
175 * This function has one side effect. If the requested file relative cluster
176 * is beyond the end of file, then the actual number of clusters in the file
177 * is returned in *cnp. This is useful for determining how long a directory is.
178 * If cnp is null, nothing is returned.
179 */
180int
181pcbmap(struct denode *dep, u_long findcn, daddr_t *bnp, u_long *cnp, int *sp)
182 /* findcn: file relative cluster to get */
183 /* bnp: returned filesys rel sector number */
184 /* cnp: returned cluster number */
185 /* sp: returned block size */
186{
187 int error;
188 u_long i;
189 u_long cn;
190 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */
191 u_long byteoffset;
192 u_long bn;
193 u_long bo;
194 struct buf *bp = NULL;
195 u_long bp_bn = -1;
196 struct msdosfsmount *pmp = dep->de_pmp;
197 u_long bsize;
198
199 fc_bmapcalls++;
200
201 /*
202 * If they don't give us someplace to return a value then don't
203 * bother doing anything.
204 */
205 if (bnp == NULL && cnp == NULL && sp == NULL)
206 return (0);
207
208 cn = dep->de_StartCluster;
209 DPRINTF(("%s(start cluster=%lu)\n", __func__, cn));
210 /*
211 * The "file" that makes up the root directory is contiguous,
212 * permanently allocated, of fixed size, and is not made up of
213 * clusters. If the cluster number is beyond the end of the root
214 * directory, then return the number of clusters in the file.
215 */
216 if (cn == MSDOSFSROOT) {
217 if (dep->de_Attributes & ATTR_DIRECTORY) {
218 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
219 if (cnp)
220 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
221 DPRINTF(("%s(root, %lu ETOOBIG)\n", __func__,
222 de_cn2off(pmp, findcn)));
223 return (E2BIG);
224 }
225 if (bnp)
226 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
227 if (cnp)
228 *cnp = MSDOSFSROOT;
229 if (sp)
230 *sp = min(pmp->pm_bpcluster,
231 dep->de_FileSize - de_cn2off(pmp, findcn));
232 DPRINTF(("%s(root, bn=%lu, cn=%u)\n", __func__,
233 pmp->pm_rootdirblk + de_cn2bn(pmp, findcn),
234 MSDOSFSROOT));
235 return (0);
236 } else { /* just an empty file */
237 if (cnp)
238 *cnp = 0;
239 DPRINTF(("%s(root, empty ETOOBIG)\n", __func__));
240 return (E2BIG);
241 }
242 }
243
244 /*
245 * All other files do I/O in cluster sized blocks
246 */
247 if (sp)
248 *sp = pmp->pm_bpcluster;
249
250 /*
251 * Rummage around in the FAT cache, maybe we can avoid tromping
252 * thru every FAT entry for the file. And, keep track of how far
253 * off the cache was from where we wanted to be.
254 */
255 i = 0;
256 fc_lookup(dep, findcn, &i, &cn);
257 DPRINTF(("%s(bpcluster=%lu i=%lu cn=%lu\n", __func__, pmp->pm_bpcluster,
258 i, cn));
259 if ((bn = findcn - i) >= LMMAX) {
260 fc_largedistance++;
261 fc_wherefrom = i;
262 fc_whereto = findcn;
263 fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn;
264 } else
265 fc_lmdistance[bn]++;
266
267 /*
268 * Handle all other files or directories the normal way.
269 */
270 for (; i < findcn; i++) {
271 /*
272 * Stop with all reserved clusters, not just with EOF.
273 */
274 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask))
275 goto hiteof;
276
277 /*
278 * Also stop when cluster is not in the filesystem
279 */
280 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) {
281 DPRINTF(("%s(cn, %lu not in %lu..%lu)\n", __func__,
282 cn, (u_long)CLUST_FIRST, pmp->pm_maxcluster));
283 if (bp)
284 brelse(bp, 0);
285 return (EINVAL);
286 }
287
288 byteoffset = FATOFS(pmp, cn);
289 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
290 if (bn != bp_bn) {
291 if (bp)
292 brelse(bp, 0);
293 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
294 0, &bp);
295 if (error) {
296 DPRINTF(("%s(bread, %d)\n", __func__, error));
297 return (error);
298 }
299 bp_bn = bn;
300 }
301 prevcn = cn;
302 if (bo >= bsize) {
303 if (bp)
304 brelse(bp, 0);
305 DPRINTF(("%s(block, %lu >= %lu)\n", __func__, bo,
306 bsize));
307 return (EIO);
308 }
309 KASSERT(bp != NULL);
310 if (FAT32(pmp))
311 cn = getulong((char *)bp->b_data + bo);
312 else
313 cn = getushort((char *)bp->b_data + bo);
314 if (FAT12(pmp) && (prevcn & 1))
315 cn >>= 4;
316 DPRINTF(("%s(cn=%lu masked=%lu)\n", __func__, cn,
317 cn & pmp->pm_fatmask));
318 cn &= pmp->pm_fatmask;
319 }
320
321 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) {
322 if (bp)
323 brelse(bp, 0);
324 if (bnp)
325 *bnp = cntobn(pmp, cn);
326 if (cnp)
327 *cnp = cn;
328 DPRINTF(("%s(bn=%lu, cn=%lu)\n", __func__, cntobn(pmp, cn),
329 cn));
330 fc_setcache(dep, FC_LASTMAP, i, cn);
331 return (0);
332 }
333
334hiteof:;
335 if (cnp)
336 *cnp = i;
337 if (bp)
338 brelse(bp, 0);
339 /* update last file cluster entry in the FAT cache */
340 fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
341 DPRINTF(("%s(eof, %lu)\n", __func__, i));
342 return (E2BIG);
343}
344
345/*
346 * Find the closest entry in the FAT cache to the cluster we are looking
347 * for.
348 */
349void
350fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp)
351{
352 int i;
353 u_long cn;
354 struct fatcache *closest = 0;
355
356 for (i = 0; i < FC_SIZE; i++) {
357 cn = dep->de_fc[i].fc_frcn;
358 if (cn != FCE_EMPTY && cn <= findcn) {
359 if (closest == 0 || cn > closest->fc_frcn)
360 closest = &dep->de_fc[i];
361 }
362 }
363 if (closest) {
364 *frcnp = closest->fc_frcn;
365 *fsrcnp = closest->fc_fsrcn;
366 }
367}
368
369/*
370 * Purge the FAT cache in denode dep of all entries relating to file
371 * relative cluster frcn and beyond.
372 */
373void
374fc_purge(struct denode *dep, u_int frcn)
375{
376 int i;
377 struct fatcache *fcp;
378
379 fcp = dep->de_fc;
380 for (i = 0; i < FC_SIZE; i++, fcp++) {
381 if (fcp->fc_frcn >= frcn)
382 fcp->fc_frcn = FCE_EMPTY;
383 }
384}
385
386/*
387 * Update the FAT.
388 * If mirroring the FAT, update all copies, with the first copy as last.
389 * Else update only the current FAT (ignoring the others).
390 *
391 * pmp - msdosfsmount structure for filesystem to update
392 * bp - addr of modified FAT block
393 * fatbn - block number relative to begin of filesystem of the modified FAT block.
394 */
395void
396updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn)
397{
398 int i, error;
399 struct buf *bpn;
400
401 DPRINTF(("%s(pmp %p, bp %p, fatbn %lu)\n", __func__, pmp, bp, fatbn));
402
403 /*
404 * If we have an FSInfo block, update it.
405 */
406 if (pmp->pm_fsinfo) {
407 u_long cn = pmp->pm_nxtfree;
408
409 if (pmp->pm_freeclustercount
410 && (pmp->pm_inusemap[cn / N_INUSEBITS]
411 & (1 << (cn % N_INUSEBITS)))) {
412 /*
413 * The cluster indicated in FSInfo isn't free
414 * any longer. Got get a new free one.
415 */
416 for (cn = 0; cn < pmp->pm_maxcluster; cn++)
417 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
418 break;
419 pmp->pm_nxtfree = cn
420 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
421 ^ (u_int)-1) - 1;
422 }
423 /*
424 * XXX If the fsinfo block is stored on media with
425 * 2KB or larger sectors, is the fsinfo structure
426 * padded at the end or in the middle?
427 */
428 if (bread(pmp->pm_devvp, de_bn2kb(pmp, pmp->pm_fsinfo),
429 pmp->pm_BytesPerSec, B_MODIFY, &bpn) != 0) {
430 /*
431 * Ignore the error, but turn off FSInfo update for the future.
432 */
433 pmp->pm_fsinfo = 0;
434 } else {
435 struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
436
437 putulong(fp->fsinfree, pmp->pm_freeclustercount);
438 putulong(fp->fsinxtfree, pmp->pm_nxtfree);
439 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
440 bwrite(bpn);
441 else
442 bdwrite(bpn);
443 }
444 }
445
446 if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
447 /*
448 * Now copy the block(s) of the modified FAT to the other copies of
449 * the FAT and write them out. This is faster than reading in the
450 * other FATs and then writing them back out. This could tie up
451 * the FAT for quite a while. Preventing others from accessing it.
452 * To prevent us from going after the FAT quite so much we use
453 * delayed writes, unless they specified "synchronous" when the
454 * filesystem was mounted. If synch is asked for then use
455 * bwrite()'s and really slow things down.
456 */
457 for (i = 1; i < pmp->pm_FATs; i++) {
458 fatbn += pmp->pm_FATsecs;
459 /* getblk() never fails */
460 bpn = getblk(pmp->pm_devvp, de_bn2kb(pmp, fatbn),
461 bp->b_bcount, 0, 0);
462 memcpy(bpn->b_data, bp->b_data, bp->b_bcount);
463 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) {
464 error = bwrite(bpn);
465 if (error)
466 printf("%s: copy FAT %d (error=%d)\n",
467 __func__, i, error);
468 } else
469 bdwrite(bpn);
470 }
471 }
472
473 /*
474 * Write out the first (or current) FAT last.
475 */
476 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) {
477 error = bwrite(bp);
478 if (error)
479 printf("%s: write FAT (error=%d)\n",
480 __func__, error);
481 } else
482 bdwrite(bp);
483 /*
484 * Maybe update fsinfo sector here?
485 */
486}
487
488/*
489 * Updating entries in 12 bit FATs is a pain in the butt.
490 *
491 * The following picture shows where nibbles go when moving from a 12 bit
492 * cluster number into the appropriate bytes in the FAT.
493 *
494 * byte m byte m+1 byte m+2
495 * +----+----+ +----+----+ +----+----+
496 * | 0 1 | | 2 3 | | 4 5 | FAT bytes
497 * +----+----+ +----+----+ +----+----+
498 *
499 * +----+----+----+ +----+----+----+
500 * | 3 0 1 | | 4 5 2 |
501 * +----+----+----+ +----+----+----+
502 * cluster n cluster n+1
503 *
504 * Where n is even. m = n + (n >> 2)
505 *
506 */
507static inline void
508usemap_alloc(struct msdosfsmount *pmp, u_long cn)
509{
510
511 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
512 pmp->pm_freeclustercount--;
513}
514
515static inline void
516usemap_free(struct msdosfsmount *pmp, u_long cn)
517{
518
519 pmp->pm_freeclustercount++;
520 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
521}
522
523int
524clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp)
525{
526 int error;
527 u_long oldcn;
528
529 usemap_free(pmp, cluster);
530 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
531 if (error) {
532 usemap_alloc(pmp, cluster);
533 return (error);
534 }
535 /*
536 * If the cluster was successfully marked free, then update
537 * the count of free clusters, and turn off the "allocated"
538 * bit in the "in use" cluster bit map.
539 */
540 if (oldcnp)
541 *oldcnp = oldcn;
542 return (0);
543}
544
545/*
546 * Get or Set or 'Get and Set' the cluster'th entry in the FAT.
547 *
548 * function - whether to get or set a fat entry
549 * pmp - address of the msdosfsmount structure for the filesystem
550 * whose FAT is to be manipulated.
551 * cn - which cluster is of interest
552 * oldcontents - address of a word that is to receive the contents of the
553 * cluster'th entry if this is a get function
554 * newcontents - the new value to be written into the cluster'th element of
555 * the FAT if this is a set function.
556 *
557 * This function can also be used to free a cluster by setting the FAT entry
558 * for a cluster to 0.
559 *
560 * All copies of the FAT are updated if this is a set function. NOTE: If
561 * fatentry() marks a cluster as free it does not update the inusemap in
562 * the msdosfsmount structure. This is left to the caller.
563 */
564int
565fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, u_long newcontents)
566{
567 int error;
568 u_long readcn;
569 u_long bn, bo, bsize, byteoffset;
570 struct buf *bp;
571
572 DPRINTF(("%s(func %d, pmp %p, clust %lu, oldcon %p, newcon " "%lx)\n",
573 __func__, function, pmp, cn, oldcontents, newcontents));
574
575#ifdef DIAGNOSTIC
576 /*
577 * Be sure they asked us to do something.
578 */
579 if ((function & (FAT_SET | FAT_GET)) == 0) {
580 DPRINTF(("%s(): function code doesn't specify get or set\n",
581 __func__));
582 return (EINVAL);
583 }
584
585 /*
586 * If they asked us to return a cluster number but didn't tell us
587 * where to put it, give them an error.
588 */
589 if ((function & FAT_GET) && oldcontents == NULL) {
590 DPRINTF(("%s(): get function with no place to put result\n",
591 __func__));
592 return (EINVAL);
593 }
594#endif
595
596 /*
597 * Be sure the requested cluster is in the filesystem.
598 */
599 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
600 return (EINVAL);
601
602 byteoffset = FATOFS(pmp, cn);
603 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
604 if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
605 0, &bp)) != 0) {
606 return (error);
607 }
608
609 if (function & FAT_GET) {
610 if (FAT32(pmp))
611 readcn = getulong((char *)bp->b_data + bo);
612 else
613 readcn = getushort((char *)bp->b_data + bo);
614 if (FAT12(pmp) & (cn & 1))
615 readcn >>= 4;
616 readcn &= pmp->pm_fatmask;
617 *oldcontents = readcn;
618 }
619 if (function & FAT_SET) {
620 switch (pmp->pm_fatmask) {
621 case FAT12_MASK:
622 readcn = getushort((char *)bp->b_data + bo);
623 if (cn & 1) {
624 readcn &= 0x000f;
625 readcn |= newcontents << 4;
626 } else {
627 readcn &= 0xf000;
628 readcn |= newcontents & 0xfff;
629 }
630 putushort((char *)bp->b_data + bo, readcn);
631 break;
632 case FAT16_MASK:
633 putushort((char *)bp->b_data + bo, newcontents);
634 break;
635 case FAT32_MASK:
636 /*
637 * According to spec we have to retain the
638 * high order bits of the FAT entry.
639 */
640 readcn = getulong((char *)bp->b_data + bo);
641 readcn &= ~FAT32_MASK;
642 readcn |= newcontents & FAT32_MASK;
643 putulong((char *)bp->b_data + bo, readcn);
644 break;
645 }
646 updatefats(pmp, bp, bn);
647 bp = NULL;
648 pmp->pm_fmod = 1;
649 }
650 if (bp)
651 brelse(bp, 0);
652 return (0);
653}
654
655/*
656 * Update a contiguous cluster chain
657 *
658 * pmp - mount point
659 * start - first cluster of chain
660 * count - number of clusters in chain
661 * fillwith - what to write into FAT entry of last cluster
662 */
663static int
664fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith)
665{
666 int error;
667 u_long bn, bo, bsize, byteoffset, readcn, newc;
668 struct buf *bp;
669
670 DPRINTF(("%s(pmp %p, start %lu, count %lu, fillwith %lx)\n", __func__,
671 pmp, start, count, fillwith));
672 /*
673 * Be sure the clusters are in the filesystem.
674 */
675 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
676 return (EINVAL);
677
678 while (count > 0) {
679 byteoffset = FATOFS(pmp, start);
680 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
681 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
682 B_MODIFY, &bp);
683 if (error) {
684 return (error);
685 }
686 while (count > 0) {
687 start++;
688 newc = --count > 0 ? start : fillwith;
689 switch (pmp->pm_fatmask) {
690 case FAT12_MASK:
691 readcn = getushort((char *)bp->b_data + bo);
692 if (start & 1) {
693 readcn &= 0xf000;
694 readcn |= newc & 0xfff;
695 } else {
696 readcn &= 0x000f;
697 readcn |= newc << 4;
698 }
699 putushort((char *)bp->b_data + bo, readcn);
700 bo++;
701 if (!(start & 1))
702 bo++;
703 break;
704 case FAT16_MASK:
705 putushort((char *)bp->b_data + bo, newc);
706 bo += 2;
707 break;
708 case FAT32_MASK:
709 readcn = getulong((char *)bp->b_data + bo);
710 readcn &= ~pmp->pm_fatmask;
711 readcn |= newc & pmp->pm_fatmask;
712 putulong((char *)bp->b_data + bo, readcn);
713 bo += 4;
714 break;
715 }
716 if (bo >= bsize)
717 break;
718 }
719 updatefats(pmp, bp, bn);
720 }
721 pmp->pm_fmod = 1;
722 return (0);
723}
724
725/*
726 * Check the length of a free cluster chain starting at start.
727 *
728 * pmp - mount point
729 * start - start of chain
730 * count - maximum interesting length
731 */
732int
733chainlength(struct msdosfsmount *pmp, u_long start, u_long count)
734{
735 u_long idx, max_idx;
736 u_int map;
737 u_long len;
738
739 max_idx = pmp->pm_maxcluster / N_INUSEBITS;
740 idx = start / N_INUSEBITS;
741 start %= N_INUSEBITS;
742 map = pmp->pm_inusemap[idx];
743 map &= ~((1 << start) - 1);
744 if (map) {
745 len = ffs(map) - 1 - start;
746 return (len > count ? count : len);
747 }
748 len = N_INUSEBITS - start;
749 if (len >= count)
750 return (count);
751 while (++idx <= max_idx) {
752 if (len >= count)
753 break;
754 if ((map = pmp->pm_inusemap[idx]) != 0) {
755 len += ffs(map) - 1;
756 break;
757 }
758 len += N_INUSEBITS;
759 }
760 return (len > count ? count : len);
761}
762
763/*
764 * Allocate contigous free clusters.
765 *
766 * pmp - mount point.
767 * start - start of cluster chain.
768 * count - number of clusters to allocate.
769 * fillwith - put this value into the FAT entry for the
770 * last allocated cluster.
771 * retcluster - put the first allocated cluster's number here.
772 * got - how many clusters were actually allocated.
773 */
774int
775chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith, u_long *retcluster, u_long *got)
776{
777 int error;
778 u_long cl, n;
779
780 for (cl = start, n = count; n-- > 0;)
781 usemap_alloc(pmp, cl++);
782 if ((error = fatchain(pmp, start, count, fillwith)) != 0)
783 return (error);
784
785 DPRINTF(("%s(): allocated cluster chain at %lu (%lu clusters)\n",
786 __func__, start, count));
787 if (retcluster)
788 *retcluster = start;
789 if (got)
790 *got = count;
791 return (0);
792}
793
794/*
795 * Allocate contiguous free clusters.
796 *
797 * pmp - mount point.
798 * start - preferred start of cluster chain.
799 * count - number of clusters requested.
800 * fillwith - put this value into the FAT entry for the
801 * last allocated cluster.
802 * retcluster - put the first allocated cluster's number here.
803 * got - how many clusters were actually allocated.
804 */
805int
806clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long *retcluster, u_long *got)
807{
808 u_long idx;
809 u_long len, newst, foundl, cn, l;
810 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */
811 u_long fillwith = CLUST_EOFE;
812 u_int map;
813
814 DPRINTF(("%s(): find %lu clusters\n", __func__, count));
815 if (start) {
816 if ((len = chainlength(pmp, start, count)) >= count)
817 return (chainalloc(pmp, start, count, fillwith, retcluster, got));
818 } else {
819 /*
820 * This is a new file, initialize start
821 */
822 struct timeval tv;
823
824 microtime(&tv);
825 start = (tv.tv_usec >> 10) | tv.tv_usec;
826 len = 0;
827 }
828
829 /*
830 * Start at a (pseudo) random place to maximize cluster runs
831 * under multiple writers.
832 */
833 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
834 foundl = 0;
835
836 for (cn = newst; cn <= pmp->pm_maxcluster;) {
837 idx = cn / N_INUSEBITS;
838 map = pmp->pm_inusemap[idx];
839 map |= (1 << (cn % N_INUSEBITS)) - 1;
840 if (map != (u_int)-1) {
841 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
842 if ((l = chainlength(pmp, cn, count)) >= count)
843 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
844 if (l > foundl) {
845 foundcn = cn;
846 foundl = l;
847 }
848 cn += l + 1;
849 continue;
850 }
851 cn += N_INUSEBITS - cn % N_INUSEBITS;
852 }
853 for (cn = 0; cn < newst;) {
854 idx = cn / N_INUSEBITS;
855 map = pmp->pm_inusemap[idx];
856 map |= (1 << (cn % N_INUSEBITS)) - 1;
857 if (map != (u_int)-1) {
858 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
859 if ((l = chainlength(pmp, cn, count)) >= count)
860 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
861 if (l > foundl) {
862 foundcn = cn;
863 foundl = l;
864 }
865 cn += l + 1;
866 continue;
867 }
868 cn += N_INUSEBITS - cn % N_INUSEBITS;
869 }
870
871 if (!foundl)
872 return (ENOSPC);
873
874 if (len)
875 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
876 else
877 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
878}
879
880
881/*
882 * Free a chain of clusters.
883 *
884 * pmp - address of the msdosfs mount structure for the filesystem
885 * containing the cluster chain to be freed.
886 * startcluster - number of the 1st cluster in the chain of clusters to be
887 * freed.
888 */
889int
890freeclusterchain(struct msdosfsmount *pmp, u_long cluster)
891{
892 int error;
893 struct buf *bp = NULL;
894 u_long bn, bo, bsize, byteoffset;
895 u_long readcn, lbn = -1;
896
897 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
898 byteoffset = FATOFS(pmp, cluster);
899 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
900 if (lbn != bn) {
901 if (bp)
902 updatefats(pmp, bp, lbn);
903 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
904 B_MODIFY, &bp);
905 if (error) {
906 return (error);
907 }
908 lbn = bn;
909 }
910 usemap_free(pmp, cluster);
911 KASSERT(bp != NULL);
912 switch (pmp->pm_fatmask) {
913 case FAT12_MASK:
914 readcn = getushort((char *)bp->b_data + bo);
915 if (cluster & 1) {
916 cluster = readcn >> 4;
917 readcn &= 0x000f;
918 readcn |= MSDOSFSFREE << 4;
919 } else {
920 cluster = readcn;
921 readcn &= 0xf000;
922 readcn |= MSDOSFSFREE & 0xfff;
923 }
924 putushort((char *)bp->b_data + bo, readcn);
925 break;
926 case FAT16_MASK:
927 cluster = getushort((char *)bp->b_data + bo);
928 putushort((char *)bp->b_data + bo, MSDOSFSFREE);
929 break;
930 case FAT32_MASK:
931 cluster = getulong((char *)bp->b_data + bo);
932 putulong((char *)bp->b_data + bo,
933 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
934 break;
935 }
936 cluster &= pmp->pm_fatmask;
937 }
938 if (bp)
939 updatefats(pmp, bp, bn);
940 return (0);
941}
942
943/*
944 * Read in FAT blocks looking for free clusters. For every free cluster
945 * found turn off its corresponding bit in the pm_inusemap.
946 */
947int
948fillinusemap(struct msdosfsmount *pmp)
949{
950 struct buf *bp = NULL;
951 u_long cn, readcn;
952 int error;
953 u_long bn, bo, bsize, byteoffset;
954
955 /*
956 * Mark all clusters in use, we mark the free ones in the FAT scan
957 * loop further down.
958 */
959 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
960 pmp->pm_inusemap[cn] = (u_int)-1;
961
962 /*
963 * Figure how many free clusters are in the filesystem by ripping
964 * through the FAT counting the number of entries whose content is
965 * zero. These represent free clusters.
966 */
967 pmp->pm_freeclustercount = 0;
968 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
969 byteoffset = FATOFS(pmp, cn);
970 bo = byteoffset % pmp->pm_fatblocksize;
971 if (!bo || !bp) {
972 /* Read new FAT block */
973 if (bp)
974 brelse(bp, 0);
975 fatblock(pmp, byteoffset, &bn, &bsize, NULL);
976 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
977 0, &bp);
978 if (error) {
979 return (error);
980 }
981 }
982 if (FAT32(pmp))
983 readcn = getulong((char *)bp->b_data + bo);
984 else
985 readcn = getushort((char *)bp->b_data + bo);
986 if (FAT12(pmp) && (cn & 1))
987 readcn >>= 4;
988 readcn &= pmp->pm_fatmask;
989
990 if (readcn == 0)
991 usemap_free(pmp, cn);
992 }
993 if (bp)
994 brelse(bp, 0);
995 return (0);
996}
997
998/*
999 * Allocate a new cluster and chain it onto the end of the file.
1000 *
1001 * dep - the file to extend
1002 * count - number of clusters to allocate
1003 * bpp - where to return the address of the buf header for the first new
1004 * file block
1005 * ncp - where to put cluster number of the first newly allocated cluster
1006 * If this pointer is 0, do not return the cluster number.
1007 * flags - see fat.h
1008 *
1009 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
1010 * the de_flag field of the denode and it does not change the de_FileSize
1011 * field. This is left for the caller to do.
1012 */
1013
1014int
1015extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, int flags)
1016{
1017 int error;
1018 u_long frcn = 0, cn, got;
1019 struct msdosfsmount *pmp = dep->de_pmp;
1020 struct buf *bp;
1021
1022 /*
1023 * Don't try to extend the root directory
1024 */
1025 if (dep->de_StartCluster == MSDOSFSROOT
1026 && (dep->de_Attributes & ATTR_DIRECTORY)) {
1027 DPRINTF(("%s(): attempt to extend root directory\n", __func__));
1028 return (ENOSPC);
1029 }
1030
1031 /*
1032 * If the "file's last cluster" cache entry is empty, and the file
1033 * is not empty, then fill the cache entry by calling pcbmap().
1034 */
1035 fc_fileextends++;
1036 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
1037 dep->de_StartCluster != 0) {
1038 fc_lfcempty++;
1039 error = pcbmap(dep, CLUST_END, 0, &cn, 0);
1040 /* we expect it to return E2BIG */
1041 if (error != E2BIG)
1042 return (error);
1043 }
1044
1045 fc_last_to_nexttolast(dep);
1046
1047 while (count > 0) {
1048
1049 /*
1050 * Allocate a new cluster chain and cat onto the end of the
1051 * file. If the file is empty we make de_StartCluster point
1052 * to the new block. Note that de_StartCluster being 0 is
1053 * sufficient to be sure the file is empty since we exclude
1054 * attempts to extend the root directory above, and the root
1055 * dir is the only file with a startcluster of 0 that has
1056 * blocks allocated (sort of).
1057 */
1058
1059 if (dep->de_StartCluster == 0)
1060 cn = 0;
1061 else
1062 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
1063 error = clusteralloc(pmp, cn, count, &cn, &got);
1064 if (error)
1065 return (error);
1066
1067 count -= got;
1068
1069 /*
1070 * Give them the filesystem relative cluster number if they want
1071 * it.
1072 */
1073 if (ncp) {
1074 *ncp = cn;
1075 ncp = NULL;
1076 }
1077
1078 if (dep->de_StartCluster == 0) {
1079 dep->de_StartCluster = cn;
1080 frcn = 0;
1081 } else {
1082 error = fatentry(FAT_SET, pmp,
1083 dep->de_fc[FC_LASTFC].fc_fsrcn,
1084 0, cn);
1085 if (error) {
1086 clusterfree(pmp, cn, NULL);
1087 return (error);
1088 }
1089 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
1090 }
1091
1092 /*
1093 * Update the "last cluster of the file" entry in the
1094 * denode's FAT cache.
1095 */
1096
1097 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
1098 if ((flags & DE_CLEAR) &&
1099 (dep->de_Attributes & ATTR_DIRECTORY)) {
1100 while (got-- > 0) {
1101 bp = getblk(pmp->pm_devvp,
1102 de_bn2kb(pmp, cntobn(pmp, cn++)),
1103 pmp->pm_bpcluster, 0, 0);
1104 clrbuf(bp);
1105 if (bpp) {
1106 *bpp = bp;
1107 bpp = NULL;
1108 } else {
1109 bdwrite(bp);
1110 }
1111 }
1112 }
1113 }
1114
1115 return (0);
1116}
1117