1 /* $NetBSD: msdosfs_fat.c,v 1.37 2024/05/13 00:24:19 msaitoh 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 1.37 2024/05/13 00:24:19 msaitoh 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 <strings.h>
73 #include <ffs/buf.h>
74 #endif
75
76 /*
77 * msdosfs include files.
78 */
79 #include <fs/msdosfs/bpb.h>
80 #include <fs/msdosfs/msdosfsmount.h>
81 #include <fs/msdosfs/direntry.h>
82 #include <fs/msdosfs/denode.h>
83 #include <fs/msdosfs/fat.h>
84
85 /*
86 * Fat cache stats.
87 */
88 int fc_fileextends; /* # of file extends */
89 int fc_lfcempty; /* # of time last file cluster cache entry
90 * was empty */
91 int fc_bmapcalls; /* # of times pcbmap was called */
92
93 #define LMMAX 20
94 int fc_lmdistance[LMMAX]; /* counters for how far off the last
95 * cluster mapped entry was. */
96 int fc_largedistance; /* off by more than LMMAX */
97 int fc_wherefrom, fc_whereto, fc_lastclust;
98 int pm_fatblocksize;
99
100 #ifdef MSDOSFS_DEBUG
101 #define DPRINTF(a) printf a
102 #else
103 #define DPRINTF(a)
104 #endif
105 #ifdef MSDOSFS_DEBUG
106 void print_fat_stats(void);
107
108 void
print_fat_stats(void)109 print_fat_stats(void)
110 {
111 int i;
112
113 printf("fc_fileextends=%d fc_lfcempty=%d fc_bmapcalls=%d "
114 "fc_largedistance=%d [%d->%d=%d] fc_lastclust=%d pm_fatblocksize=%d\n",
115 fc_fileextends, fc_lfcempty, fc_bmapcalls, fc_largedistance,
116 fc_wherefrom, fc_whereto, fc_whereto-fc_wherefrom,
117 fc_lastclust, pm_fatblocksize);
118
119 fc_fileextends = fc_lfcempty = fc_bmapcalls = 0;
120 fc_wherefrom = fc_whereto = fc_lastclust = 0;
121
122 for (i = 0; i < LMMAX; i++) {
123 printf("%d:%d ", i, fc_lmdistance[i]);
124 fc_lmdistance[i] = 0;
125 }
126
127 printf("\n");
128 }
129 #endif
130
131 static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *,
132 u_long *);
133 void updatefats(struct msdosfsmount *, struct buf *, u_long);
134 static inline void usemap_free(struct msdosfsmount *, u_long);
135 static inline void usemap_alloc(struct msdosfsmount *, u_long);
136 static int fatchain(struct msdosfsmount *, u_long, u_long, u_long);
137 int chainlength(struct msdosfsmount *, u_long, u_long);
138 int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *,
139 u_long *);
140
141 static void
fatblock(struct msdosfsmount * pmp,u_long ofs,u_long * bnp,u_long * sizep,u_long * bop)142 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, u_long *bop)
143 {
144 u_long bn, size;
145
146 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
147 size = uimin(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
148 * pmp->pm_BytesPerSec;
149 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
150
151 DPRINTF(("%s(ofs=%lu bn=%lu, size=%lu, bo=%lu)\n", __func__, ofs, bn,
152 size, ofs % pmp->pm_fatblocksize));
153 if (bnp)
154 *bnp = bn;
155 if (sizep)
156 *sizep = size;
157 if (bop)
158 *bop = ofs % pmp->pm_fatblocksize;
159
160 pm_fatblocksize = pmp->pm_fatblocksize;
161 }
162
163 /*
164 * Map the logical cluster number of a file into a physical disk sector
165 * that is filesystem relative.
166 *
167 * dep - address of denode representing the file of interest
168 * findcn - file relative cluster whose filesystem relative cluster number
169 * and/or block number are/is to be found
170 * bnp - address of where to place the file system relative block number.
171 * If this pointer is null then don't return this quantity.
172 * cnp - address of where to place the file system relative cluster number.
173 * If this pointer is null then don't return this quantity.
174 *
175 * NOTE: Either bnp or cnp must be non-null.
176 * This function has one side effect. If the requested file relative cluster
177 * is beyond the end of file, then the actual number of clusters in the file
178 * is returned in *cnp. This is useful for determining how long a directory is.
179 * If cnp is null, nothing is returned.
180 */
181 int
msdosfs_pcbmap(struct denode * dep,u_long findcn,daddr_t * bnp,u_long * cnp,int * sp)182 msdosfs_pcbmap(struct denode *dep,
183 u_long findcn, /* file relative cluster to get */
184 daddr_t *bnp, /* returned filesys rel sector number */
185 u_long *cnp, /* returned cluster number */
186 int *sp) /* returned block size */
187 {
188 int error;
189 u_long i;
190 u_long cn;
191 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */
192 u_long byteoffset;
193 u_long bn;
194 u_long bo;
195 struct buf *bp = NULL;
196 u_long bp_bn = -1;
197 struct msdosfsmount *pmp = dep->de_pmp;
198 u_long bsize;
199
200 fc_bmapcalls++;
201
202 /*
203 * If they don't give us someplace to return a value then don't
204 * bother doing anything.
205 */
206 if (bnp == NULL && cnp == NULL && sp == NULL)
207 return (0);
208
209 cn = dep->de_StartCluster;
210 DPRINTF(("%s(start cluster=%lu)\n", __func__, cn));
211 /*
212 * The "file" that makes up the root directory is contiguous,
213 * permanently allocated, of fixed size, and is not made up of
214 * clusters. If the cluster number is beyond the end of the root
215 * directory, then return the number of clusters in the file.
216 */
217 if (cn == MSDOSFSROOT) {
218 if (dep->de_Attributes & ATTR_DIRECTORY) {
219 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
220 if (cnp)
221 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
222 DPRINTF(("%s(root, %lu ETOOBIG)\n", __func__,
223 de_cn2off(pmp, findcn)));
224 return (E2BIG);
225 }
226 if (bnp)
227 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
228 if (cnp)
229 *cnp = MSDOSFSROOT;
230 if (sp)
231 *sp = uimin(pmp->pm_bpcluster,
232 dep->de_FileSize - de_cn2off(pmp, findcn));
233 DPRINTF(("%s(root, bn=%lu, cn=%u)\n", __func__,
234 pmp->pm_rootdirblk + de_cn2bn(pmp, findcn),
235 MSDOSFSROOT));
236 return (0);
237 } else { /* just an empty file */
238 if (cnp)
239 *cnp = 0;
240 DPRINTF(("%s(root, empty ETOOBIG)\n", __func__));
241 return (E2BIG);
242 }
243 }
244
245 /*
246 * All other files do I/O in cluster sized blocks
247 */
248 if (sp)
249 *sp = pmp->pm_bpcluster;
250
251 /*
252 * Rummage around in the FAT cache, maybe we can avoid tromping
253 * thru every FAT entry for the file. And, keep track of how far
254 * off the cache was from where we wanted to be.
255 */
256 i = 0;
257 msdosfs_fc_lookup(dep, findcn, &i, &cn);
258 DPRINTF(("%s(bpcluster=%lu i=%lu cn=%lu\n", __func__, pmp->pm_bpcluster,
259 i, cn));
260 if ((bn = findcn - i) >= LMMAX) {
261 fc_largedistance++;
262 fc_wherefrom = i;
263 fc_whereto = findcn;
264 fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn;
265 } else
266 fc_lmdistance[bn]++;
267
268 /*
269 * Handle all other files or directories the normal way.
270 */
271 for (; i < findcn; i++) {
272 /*
273 * Stop with all reserved clusters, not just with EOF.
274 */
275 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask))
276 goto hiteof;
277
278 /*
279 * Also stop when cluster is not in the filesystem
280 */
281 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) {
282 DPRINTF(("%s(cn, %lu not in %lu..%lu)\n", __func__,
283 cn, (u_long)CLUST_FIRST, pmp->pm_maxcluster));
284 if (bp)
285 brelse(bp, 0);
286 return (EINVAL);
287 }
288
289 byteoffset = FATOFS(pmp, cn);
290 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
291 if (bn != bp_bn) {
292 if (bp)
293 brelse(bp, 0);
294 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
295 0, &bp);
296 if (error) {
297 DPRINTF(("%s(bread, %d)\n", __func__, error));
298 return (error);
299 }
300 bp_bn = bn;
301 }
302 prevcn = cn;
303 if (bo >= bsize) {
304 if (bp)
305 brelse(bp, 0);
306 DPRINTF(("%s(block, %lu >= %lu)\n", __func__, bo,
307 bsize));
308 return (EIO);
309 }
310 KASSERT(bp != NULL);
311 if (FAT32(pmp))
312 cn = getulong((char *)bp->b_data + bo);
313 else
314 cn = getushort((char *)bp->b_data + bo);
315 if (FAT12(pmp) && (prevcn & 1))
316 cn >>= 4;
317 DPRINTF(("%s(cn=%lu masked=%lu)\n", __func__, cn,
318 cn & pmp->pm_fatmask));
319 cn &= pmp->pm_fatmask;
320 }
321
322 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) {
323 if (bp)
324 brelse(bp, 0);
325 if (bnp)
326 *bnp = cntobn(pmp, cn);
327 if (cnp)
328 *cnp = cn;
329 DPRINTF(("%s(bn=%lu, cn=%lu)\n", __func__, cntobn(pmp, cn),
330 cn));
331 fc_setcache(dep, FC_LASTMAP, i, cn);
332 return (0);
333 }
334
335 hiteof:;
336 if (cnp)
337 *cnp = i;
338 if (bp)
339 brelse(bp, 0);
340 /* update last file cluster entry in the FAT cache */
341 fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
342 DPRINTF(("%s(eof, %lu)\n", __func__, i));
343 return (E2BIG);
344 }
345
346 /*
347 * Find the closest entry in the FAT cache to the cluster we are looking
348 * for.
349 */
350 void
msdosfs_fc_lookup(struct denode * dep,u_long findcn,u_long * frcnp,u_long * fsrcnp)351 msdosfs_fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp,
352 u_long *fsrcnp)
353 {
354 int i;
355 u_long cn;
356 struct fatcache *closest = 0;
357
358 for (i = 0; i < FC_SIZE; i++) {
359 cn = dep->de_fc[i].fc_frcn;
360 if (cn != FCE_EMPTY && cn <= findcn) {
361 if (closest == 0 || cn > closest->fc_frcn)
362 closest = &dep->de_fc[i];
363 }
364 }
365 if (closest) {
366 *frcnp = closest->fc_frcn;
367 *fsrcnp = closest->fc_fsrcn;
368 }
369 }
370
371 /*
372 * Purge the FAT cache in denode dep of all entries relating to file
373 * relative cluster frcn and beyond.
374 */
375 void
msdosfs_fc_purge(struct denode * dep,u_int frcn)376 msdosfs_fc_purge(struct denode *dep, u_int frcn)
377 {
378 int i;
379 struct fatcache *fcp;
380
381 fcp = dep->de_fc;
382 for (i = 0; i < FC_SIZE; i++, fcp++) {
383 if (fcp->fc_frcn >= frcn)
384 fcp->fc_frcn = FCE_EMPTY;
385 }
386 }
387
388 /*
389 * Update the FAT.
390 * If mirroring the FAT, update all copies, with the first copy as last.
391 * Else update only the current FAT (ignoring the others).
392 *
393 * pmp - msdosfsmount structure for filesystem to update
394 * bp - addr of modified FAT block
395 * fatbn - block number relative to begin of filesystem of the modified FAT block.
396 */
397 void
updatefats(struct msdosfsmount * pmp,struct buf * bp,u_long fatbn)398 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn)
399 {
400 int i, error;
401 struct buf *bpn;
402
403 DPRINTF(("%s(pmp %p, bp %p, fatbn %lu)\n", __func__, pmp, bp, fatbn));
404
405 /*
406 * If we have an FSInfo block, update it.
407 */
408 if (pmp->pm_fsinfo) {
409 u_long cn = pmp->pm_nxtfree;
410
411 if (pmp->pm_freeclustercount
412 && (pmp->pm_inusemap[cn / N_INUSEBITS]
413 & (1U << (cn % N_INUSEBITS)))) {
414 /*
415 * The cluster indicated in FSInfo isn't free
416 * any longer. Got get a new free one.
417 */
418 for (cn = 0; cn < pmp->pm_maxcluster; cn++)
419 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
420 break;
421 pmp->pm_nxtfree = cn
422 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
423 ^ (u_int)-1) - 1;
424 }
425 /*
426 * XXX If the fsinfo block is stored on media with
427 * 2KB or larger sectors, is the fsinfo structure
428 * padded at the end or in the middle?
429 */
430 if (bread(pmp->pm_devvp, de_bn2kb(pmp, pmp->pm_fsinfo),
431 pmp->pm_BytesPerSec, B_MODIFY, &bpn) != 0) {
432 /*
433 * Ignore the error, but turn off FSInfo update for the future.
434 */
435 pmp->pm_fsinfo = 0;
436 } else {
437 struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
438
439 putulong(fp->fsinfree, pmp->pm_freeclustercount);
440 putulong(fp->fsinxtfree, pmp->pm_nxtfree);
441 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
442 bwrite(bpn);
443 else
444 bdwrite(bpn);
445 }
446 }
447
448 if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
449 /*
450 * Now copy the block(s) of the modified FAT to the other copies of
451 * the FAT and write them out. This is faster than reading in the
452 * other FATs and then writing them back out. This could tie up
453 * the FAT for quite a while. Preventing others from accessing it.
454 * To prevent us from going after the FAT quite so much we use
455 * delayed writes, unless they specified "synchronous" when the
456 * filesystem was mounted. If synch is asked for then use
457 * bwrite()'s and really slow things down.
458 */
459 for (i = 1; i < pmp->pm_FATs; i++) {
460 fatbn += pmp->pm_FATsecs;
461 /* getblk() never fails */
462 bpn = getblk(pmp->pm_devvp, de_bn2kb(pmp, fatbn),
463 bp->b_bcount, 0, 0);
464 memcpy(bpn->b_data, bp->b_data, bp->b_bcount);
465 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) {
466 error = bwrite(bpn);
467 if (error)
468 printf("%s: copy FAT %d (error=%d)\n",
469 __func__, i, error);
470 } else
471 bdwrite(bpn);
472 }
473 }
474
475 /*
476 * Write out the first (or current) FAT last.
477 */
478 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) {
479 error = bwrite(bp);
480 if (error)
481 printf("%s: write FAT (error=%d)\n",
482 __func__, error);
483 } else
484 bdwrite(bp);
485 /*
486 * Maybe update fsinfo sector here?
487 */
488 }
489
490 /*
491 * Updating entries in 12 bit FATs is a pain in the butt.
492 *
493 * The following picture shows where nibbles go when moving from a 12 bit
494 * cluster number into the appropriate bytes in the FAT.
495 *
496 * byte m byte m+1 byte m+2
497 * +----+----+ +----+----+ +----+----+
498 * | 0 1 | | 2 3 | | 4 5 | FAT bytes
499 * +----+----+ +----+----+ +----+----+
500 *
501 * +----+----+----+ +----+----+----+
502 * | 3 0 1 | | 4 5 2 |
503 * +----+----+----+ +----+----+----+
504 * cluster n cluster n+1
505 *
506 * Where n is even. m = n + (n >> 2)
507 *
508 */
509 static inline void
usemap_alloc(struct msdosfsmount * pmp,u_long cn)510 usemap_alloc(struct msdosfsmount *pmp, u_long cn)
511 {
512
513 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS);
514 pmp->pm_freeclustercount--;
515 }
516
517 static inline void
usemap_free(struct msdosfsmount * pmp,u_long cn)518 usemap_free(struct msdosfsmount *pmp, u_long cn)
519 {
520
521 pmp->pm_freeclustercount++;
522 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1U << (cn % N_INUSEBITS));
523 }
524
525 int
msdosfs_clusterfree(struct msdosfsmount * pmp,u_long cluster,u_long * oldcnp)526 msdosfs_clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp)
527 {
528 int error;
529 u_long oldcn;
530
531 usemap_free(pmp, cluster);
532 error = msdosfs_fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn,
533 MSDOSFSFREE);
534 if (error) {
535 usemap_alloc(pmp, cluster);
536 return (error);
537 }
538 /*
539 * If the cluster was successfully marked free, then update
540 * the count of free clusters, and turn off the "allocated"
541 * bit in the "in use" cluster bit map.
542 */
543 if (oldcnp)
544 *oldcnp = oldcn;
545 return (0);
546 }
547
548 /*
549 * Get or Set or 'Get and Set' the cluster'th entry in the FAT.
550 *
551 * function - whether to get or set a fat entry
552 * pmp - address of the msdosfsmount structure for the filesystem
553 * whose FAT is to be manipulated.
554 * cn - which cluster is of interest
555 * oldcontents - address of a word that is to receive the contents of the
556 * cluster'th entry if this is a get function
557 * newcontents - the new value to be written into the cluster'th element of
558 * the FAT if this is a set function.
559 *
560 * This function can also be used to free a cluster by setting the FAT entry
561 * for a cluster to 0.
562 *
563 * All copies of the FAT are updated if this is a set function. NOTE: If
564 * fatentry() marks a cluster as free it does not update the inusemap in
565 * the msdosfsmount structure. This is left to the caller.
566 */
567 int
msdosfs_fatentry(int function,struct msdosfsmount * pmp,u_long cn,u_long * oldcontents,u_long newcontents)568 msdosfs_fatentry(int function, struct msdosfsmount *pmp, u_long cn,
569 u_long *oldcontents, u_long newcontents)
570 {
571 int error;
572 u_long readcn;
573 u_long bn, bo, bsize, byteoffset;
574 struct buf *bp;
575
576 DPRINTF(("%s(func %d, pmp %p, clust %lu, oldcon %p, newcon " "%lx)\n",
577 __func__, function, pmp, cn, oldcontents, newcontents));
578
579 #ifdef DIAGNOSTIC
580 /*
581 * Be sure they asked us to do something.
582 */
583 if ((function & (FAT_SET | FAT_GET)) == 0) {
584 DPRINTF(("%s(): function code doesn't specify get or set\n",
585 __func__));
586 return (EINVAL);
587 }
588
589 /*
590 * If they asked us to return a cluster number but didn't tell us
591 * where to put it, give them an error.
592 */
593 if ((function & FAT_GET) && oldcontents == NULL) {
594 DPRINTF(("%s(): get function with no place to put result\n",
595 __func__));
596 return (EINVAL);
597 }
598 #endif
599
600 /*
601 * Be sure the requested cluster is in the filesystem.
602 */
603 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
604 return (EINVAL);
605
606 byteoffset = FATOFS(pmp, cn);
607 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
608 if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
609 0, &bp)) != 0) {
610 return (error);
611 }
612
613 if (function & FAT_GET) {
614 if (FAT32(pmp))
615 readcn = getulong((char *)bp->b_data + bo);
616 else
617 readcn = getushort((char *)bp->b_data + bo);
618 if (FAT12(pmp) & (cn & 1))
619 readcn >>= 4;
620 readcn &= pmp->pm_fatmask;
621 *oldcontents = readcn;
622 }
623 if (function & FAT_SET) {
624 switch (pmp->pm_fatmask) {
625 case FAT12_MASK:
626 readcn = getushort((char *)bp->b_data + bo);
627 if (cn & 1) {
628 readcn &= 0x000f;
629 readcn |= newcontents << 4;
630 } else {
631 readcn &= 0xf000;
632 readcn |= newcontents & 0xfff;
633 }
634 putushort((char *)bp->b_data + bo, readcn);
635 break;
636 case FAT16_MASK:
637 putushort((char *)bp->b_data + bo, newcontents);
638 break;
639 case FAT32_MASK:
640 /*
641 * According to spec we have to retain the
642 * high order bits of the FAT entry.
643 */
644 readcn = getulong((char *)bp->b_data + bo);
645 readcn &= ~FAT32_MASK;
646 readcn |= newcontents & FAT32_MASK;
647 putulong((char *)bp->b_data + bo, readcn);
648 break;
649 }
650 updatefats(pmp, bp, bn);
651 bp = NULL;
652 pmp->pm_fmod = 1;
653 }
654 if (bp)
655 brelse(bp, 0);
656 return (0);
657 }
658
659 /*
660 * Update a contiguous cluster chain
661 *
662 * pmp - mount point
663 * start - first cluster of chain
664 * count - number of clusters in chain
665 * fillwith - what to write into FAT entry of last cluster
666 */
667 static int
fatchain(struct msdosfsmount * pmp,u_long start,u_long count,u_long fillwith)668 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith)
669 {
670 int error;
671 u_long bn, bo, bsize, byteoffset, readcn, newc;
672 struct buf *bp;
673
674 DPRINTF(("%s(pmp %p, start %lu, count %lu, fillwith %lx)\n", __func__,
675 pmp, start, count, fillwith));
676 /*
677 * Be sure the clusters are in the filesystem.
678 */
679 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
680 return (EINVAL);
681
682 while (count > 0) {
683 byteoffset = FATOFS(pmp, start);
684 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
685 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
686 B_MODIFY, &bp);
687 if (error) {
688 return (error);
689 }
690 while (count > 0) {
691 start++;
692 newc = --count > 0 ? start : fillwith;
693 switch (pmp->pm_fatmask) {
694 case FAT12_MASK:
695 readcn = getushort((char *)bp->b_data + bo);
696 if (start & 1) {
697 readcn &= 0xf000;
698 readcn |= newc & 0xfff;
699 } else {
700 readcn &= 0x000f;
701 readcn |= newc << 4;
702 }
703 putushort((char *)bp->b_data + bo, readcn);
704 bo++;
705 if (!(start & 1))
706 bo++;
707 break;
708 case FAT16_MASK:
709 putushort((char *)bp->b_data + bo, newc);
710 bo += 2;
711 break;
712 case FAT32_MASK:
713 readcn = getulong((char *)bp->b_data + bo);
714 readcn &= ~pmp->pm_fatmask;
715 readcn |= newc & pmp->pm_fatmask;
716 putulong((char *)bp->b_data + bo, readcn);
717 bo += 4;
718 break;
719 }
720 if (bo >= bsize)
721 break;
722 }
723 updatefats(pmp, bp, bn);
724 }
725 pmp->pm_fmod = 1;
726 return (0);
727 }
728
729 /*
730 * Check the length of a free cluster chain starting at start.
731 *
732 * pmp - mount point
733 * start - start of chain
734 * count - maximum interesting length
735 */
736 int
chainlength(struct msdosfsmount * pmp,u_long start,u_long count)737 chainlength(struct msdosfsmount *pmp, u_long start, u_long count)
738 {
739 u_long idx, max_idx;
740 u_int map;
741 u_long len;
742
743 max_idx = pmp->pm_maxcluster / N_INUSEBITS;
744 idx = start / N_INUSEBITS;
745 start %= N_INUSEBITS;
746 map = pmp->pm_inusemap[idx];
747 map &= ~((1U << start) - 1);
748 if (map) {
749 len = ffs(map) - 1 - start;
750 return (len > count ? count : len);
751 }
752 len = N_INUSEBITS - start;
753 if (len >= count)
754 return (count);
755 while (++idx <= max_idx) {
756 if (len >= count)
757 break;
758 if ((map = pmp->pm_inusemap[idx]) != 0) {
759 len += ffs(map) - 1;
760 break;
761 }
762 len += N_INUSEBITS;
763 }
764 return (len > count ? count : len);
765 }
766
767 /*
768 * Allocate contiguous free clusters.
769 *
770 * pmp - mount point.
771 * start - start of cluster chain.
772 * count - number of clusters to allocate.
773 * fillwith - put this value into the FAT entry for the
774 * last allocated cluster.
775 * retcluster - put the first allocated cluster's number here.
776 * got - how many clusters were actually allocated.
777 */
778 int
chainalloc(struct msdosfsmount * pmp,u_long start,u_long count,u_long fillwith,u_long * retcluster,u_long * got)779 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith, u_long *retcluster, u_long *got)
780 {
781 int error;
782 u_long cl, n;
783
784 for (cl = start, n = count; n-- > 0;)
785 usemap_alloc(pmp, cl++);
786 if ((error = fatchain(pmp, start, count, fillwith)) != 0)
787 return (error);
788
789 DPRINTF(("%s(): allocated cluster chain at %lu (%lu clusters)\n",
790 __func__, start, count));
791 if (retcluster)
792 *retcluster = start;
793 if (got)
794 *got = count;
795 return (0);
796 }
797
798 /*
799 * Allocate contiguous free clusters.
800 *
801 * pmp - mount point.
802 * start - preferred start of cluster chain.
803 * count - number of clusters requested.
804 * fillwith - put this value into the FAT entry for the
805 * last allocated cluster.
806 * retcluster - put the first allocated cluster's number here.
807 * got - how many clusters were actually allocated.
808 */
809 int
msdosfs_clusteralloc(struct msdosfsmount * pmp,u_long start,u_long count,u_long * retcluster,u_long * got)810 msdosfs_clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count,
811 u_long *retcluster, u_long *got)
812 {
813 u_long idx;
814 u_long len, newst, foundl, cn, l;
815 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */
816 u_long fillwith = CLUST_EOFE;
817 u_int map;
818
819 DPRINTF(("%s(): find %lu clusters\n", __func__, count));
820 if (start) {
821 if ((len = chainlength(pmp, start, count)) >= count)
822 return (chainalloc(pmp, start, count, fillwith, retcluster, got));
823 } else {
824 /*
825 * This is a new file, initialize start
826 */
827 struct timeval tv;
828
829 microtime(&tv);
830 start = (tv.tv_usec >> 10) | tv.tv_usec;
831 len = 0;
832 }
833
834 /*
835 * Start at a (pseudo) random place to maximize cluster runs
836 * under multiple writers.
837 */
838 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
839 foundl = 0;
840
841 for (cn = newst; cn <= pmp->pm_maxcluster;) {
842 idx = cn / N_INUSEBITS;
843 map = pmp->pm_inusemap[idx];
844 map |= (1U << (cn % N_INUSEBITS)) - 1;
845 if (map != (u_int)-1) {
846 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
847 if ((l = chainlength(pmp, cn, count)) >= count)
848 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
849 if (l > foundl) {
850 foundcn = cn;
851 foundl = l;
852 }
853 cn += l + 1;
854 continue;
855 }
856 cn += N_INUSEBITS - cn % N_INUSEBITS;
857 }
858 for (cn = 0; cn < newst;) {
859 idx = cn / N_INUSEBITS;
860 map = pmp->pm_inusemap[idx];
861 map |= (1U << (cn % N_INUSEBITS)) - 1;
862 if (map != (u_int)-1) {
863 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
864 if ((l = chainlength(pmp, cn, count)) >= count)
865 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
866 if (l > foundl) {
867 foundcn = cn;
868 foundl = l;
869 }
870 cn += l + 1;
871 continue;
872 }
873 cn += N_INUSEBITS - cn % N_INUSEBITS;
874 }
875
876 if (!foundl)
877 return (ENOSPC);
878
879 if (len)
880 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
881 else
882 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
883 }
884
885
886 /*
887 * Free a chain of clusters.
888 *
889 * pmp - address of the msdosfs mount structure for the filesystem
890 * containing the cluster chain to be freed.
891 * startcluster - number of the 1st cluster in the chain of clusters to be
892 * freed.
893 */
894 int
msdosfs_freeclusterchain(struct msdosfsmount * pmp,u_long cluster)895 msdosfs_freeclusterchain(struct msdosfsmount *pmp, u_long cluster)
896 {
897 int error;
898 struct buf *bp = NULL;
899 u_long bn, bo, bsize, byteoffset;
900 u_long readcn, lbn = -1;
901
902 bn = 0; /* XXXgcc */
903 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
904 byteoffset = FATOFS(pmp, cluster);
905 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
906 if (lbn != bn) {
907 if (bp)
908 updatefats(pmp, bp, lbn);
909 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
910 B_MODIFY, &bp);
911 if (error) {
912 return (error);
913 }
914 lbn = bn;
915 }
916 usemap_free(pmp, cluster);
917 KASSERT(bp != NULL);
918 switch (pmp->pm_fatmask) {
919 case FAT12_MASK:
920 readcn = getushort((char *)bp->b_data + bo);
921 if (cluster & 1) {
922 cluster = readcn >> 4;
923 readcn &= 0x000f;
924 readcn |= MSDOSFSFREE << 4;
925 } else {
926 cluster = readcn;
927 readcn &= 0xf000;
928 readcn |= MSDOSFSFREE & 0xfff;
929 }
930 putushort((char *)bp->b_data + bo, readcn);
931 break;
932 case FAT16_MASK:
933 cluster = getushort((char *)bp->b_data + bo);
934 putushort((char *)bp->b_data + bo, MSDOSFSFREE);
935 break;
936 case FAT32_MASK:
937 cluster = getulong((char *)bp->b_data + bo);
938 putulong((char *)bp->b_data + bo,
939 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
940 break;
941 }
942 cluster &= pmp->pm_fatmask;
943 }
944 if (bp)
945 updatefats(pmp, bp, bn);
946 return (0);
947 }
948
949 /*
950 * Read in FAT blocks looking for free clusters. For every free cluster
951 * found turn off its corresponding bit in the pm_inusemap.
952 */
953 int
msdosfs_fillinusemap(struct msdosfsmount * pmp)954 msdosfs_fillinusemap(struct msdosfsmount *pmp)
955 {
956 struct buf *bp = NULL;
957 u_long cn, readcn;
958 int error;
959 u_long bn, bo, bsize, byteoffset;
960
961 /*
962 * Mark all clusters in use, we mark the free ones in the FAT scan
963 * loop further down.
964 */
965 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
966 pmp->pm_inusemap[cn] = (u_int)-1;
967
968 /*
969 * Figure how many free clusters are in the filesystem by ripping
970 * through the FAT counting the number of entries whose content is
971 * zero. These represent free clusters.
972 */
973 pmp->pm_freeclustercount = 0;
974 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
975 byteoffset = FATOFS(pmp, cn);
976 bo = byteoffset % pmp->pm_fatblocksize;
977 if (!bo || !bp) {
978 /* Read new FAT block */
979 if (bp)
980 brelse(bp, 0);
981 fatblock(pmp, byteoffset, &bn, &bsize, NULL);
982 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
983 0, &bp);
984 if (error) {
985 return (error);
986 }
987 }
988 if (FAT32(pmp))
989 readcn = getulong((char *)bp->b_data + bo);
990 else
991 readcn = getushort((char *)bp->b_data + bo);
992 if (FAT12(pmp) && (cn & 1))
993 readcn >>= 4;
994 readcn &= pmp->pm_fatmask;
995
996 if (readcn == 0)
997 usemap_free(pmp, cn);
998 }
999 if (bp)
1000 brelse(bp, 0);
1001 return (0);
1002 }
1003
1004 /*
1005 * Allocate a new cluster and chain it onto the end of the file.
1006 *
1007 * dep - the file to extend
1008 * count - number of clusters to allocate
1009 * bpp - where to return the address of the buf header for the first new
1010 * file block
1011 * ncp - where to put cluster number of the first newly allocated cluster
1012 * If this pointer is 0, do not return the cluster number.
1013 * flags - see fat.h
1014 *
1015 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
1016 * the de_flag field of the denode and it does not change the de_FileSize
1017 * field. This is left for the caller to do.
1018 */
1019
1020 int
msdosfs_extendfile(struct denode * dep,u_long count,struct buf ** bpp,u_long * ncp,int flags)1021 msdosfs_extendfile(struct denode *dep, u_long count, struct buf **bpp,
1022 u_long *ncp, int flags)
1023 {
1024 int error;
1025 u_long frcn = 0, cn, got;
1026 struct msdosfsmount *pmp = dep->de_pmp;
1027 struct buf *bp;
1028
1029 /*
1030 * Don't try to extend the root directory
1031 */
1032 if (dep->de_StartCluster == MSDOSFSROOT
1033 && (dep->de_Attributes & ATTR_DIRECTORY)) {
1034 DPRINTF(("%s(): attempt to extend root directory\n", __func__));
1035 return (ENOSPC);
1036 }
1037
1038 /*
1039 * If the "file's last cluster" cache entry is empty, and the file
1040 * is not empty, then fill the cache entry by calling pcbmap().
1041 */
1042 fc_fileextends++;
1043 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
1044 dep->de_StartCluster != 0) {
1045 fc_lfcempty++;
1046 error = msdosfs_pcbmap(dep, CLUST_END, 0, &cn, 0);
1047 /* we expect it to return E2BIG */
1048 if (error != E2BIG)
1049 return (error);
1050 }
1051
1052 fc_last_to_nexttolast(dep);
1053
1054 while (count > 0) {
1055
1056 /*
1057 * Allocate a new cluster chain and cat onto the end of the
1058 * file. If the file is empty we make de_StartCluster point
1059 * to the new block. Note that de_StartCluster being 0 is
1060 * sufficient to be sure the file is empty since we exclude
1061 * attempts to extend the root directory above, and the root
1062 * dir is the only file with a startcluster of 0 that has
1063 * blocks allocated (sort of).
1064 */
1065
1066 if (dep->de_StartCluster == 0)
1067 cn = 0;
1068 else
1069 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
1070 error = msdosfs_clusteralloc(pmp, cn, count, &cn, &got);
1071 if (error)
1072 return (error);
1073
1074 count -= got;
1075
1076 /*
1077 * Give them the filesystem relative cluster number if they want
1078 * it.
1079 */
1080 if (ncp) {
1081 *ncp = cn;
1082 ncp = NULL;
1083 }
1084
1085 if (dep->de_StartCluster == 0) {
1086 dep->de_StartCluster = cn;
1087 frcn = 0;
1088 } else {
1089 error = msdosfs_fatentry(FAT_SET, pmp,
1090 dep->de_fc[FC_LASTFC].fc_fsrcn,
1091 0, cn);
1092 if (error) {
1093 msdosfs_clusterfree(pmp, cn, NULL);
1094 return (error);
1095 }
1096 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
1097 }
1098
1099 /*
1100 * Update the "last cluster of the file" entry in the
1101 * denode's FAT cache.
1102 */
1103
1104 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
1105 if ((flags & DE_CLEAR) &&
1106 (dep->de_Attributes & ATTR_DIRECTORY)) {
1107 while (got-- > 0) {
1108 bp = getblk(pmp->pm_devvp,
1109 de_bn2kb(pmp, cntobn(pmp, cn++)),
1110 pmp->pm_bpcluster, 0, 0);
1111 clrbuf(bp);
1112 if (bpp) {
1113 *bpp = bp;
1114 bpp = NULL;
1115 } else {
1116 bdwrite(bp);
1117 }
1118 }
1119 }
1120 }
1121
1122 return (0);
1123 }
1124