1 /* $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $ */
2
3 /*-
4 * SPDX-License-Identifier: BSD-4-Clause
5 *
6 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
7 * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
8 * All rights reserved.
9 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by TooLs GmbH.
22 * 4. The name of TooLs GmbH may not be used to endorse or promote products
23 * derived from this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
29 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
30 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
31 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
32 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
33 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
34 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 */
36 /*-
37 * Written by Paul Popelka (paulp@uts.amdahl.com)
38 *
39 * You can do anything you want with this software, just don't say you wrote
40 * it, and don't remove this notice.
41 *
42 * This software is provided "as is".
43 *
44 * The author supplies this software to be publicly redistributed on the
45 * understanding that the author is not responsible for the correct
46 * functioning of this software in any circumstances and is not liable for
47 * any damages caused by this software.
48 *
49 * October 1992
50 */
51
52 #include <sys/param.h>
53 #include <sys/errno.h>
54
55 #include <assert.h>
56 #include <stdbool.h>
57 #include <stdio.h>
58 #include <string.h>
59 #include <strings.h>
60
61 #include <fs/msdosfs/bpb.h>
62 #include "msdos/denode.h"
63 #include <fs/msdosfs/fat.h>
64 #include <fs/msdosfs/msdosfsmount.h>
65
66 #include "makefs.h"
67 #include "msdos.h"
68
69 #define FULL_RUN ((u_int)0xffffffff)
70 #define SYNCHRONOUS_WRITES(pmp) 1
71
72 static int chainalloc(struct msdosfsmount *pmp, u_long start,
73 u_long count, u_long fillwith, u_long *retcluster,
74 u_long *got);
75 static int chainlength(struct msdosfsmount *pmp, u_long start,
76 u_long count);
77 static void fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp,
78 u_long *sizep, u_long *bop);
79 static int fatchain(struct msdosfsmount *pmp, u_long start, u_long count,
80 u_long fillwith);
81 static void fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp,
82 u_long *fsrcnp);
83 static void updatefats(struct msdosfsmount *pmp, struct m_buf *bp,
84 u_long fatbn);
85 static __inline void
86 usemap_alloc(struct msdosfsmount *pmp, u_long cn);
87 static __inline void
88 usemap_free(struct msdosfsmount *pmp, u_long cn);
89 static int clusteralloc1(struct msdosfsmount *pmp, u_long start,
90 u_long count, u_long fillwith, u_long *retcluster,
91 u_long *got);
92
93 static void
fatblock(struct msdosfsmount * pmp,u_long ofs,u_long * bnp,u_long * sizep,u_long * bop)94 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep,
95 u_long *bop)
96 {
97 u_long bn, size;
98
99 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
100 size = MIN(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
101 * DEV_BSIZE;
102 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
103
104 if (bnp)
105 *bnp = bn;
106 if (sizep)
107 *sizep = size;
108 if (bop)
109 *bop = ofs % pmp->pm_fatblocksize;
110 }
111
112 /*
113 * Map the logical cluster number of a file into a physical disk sector
114 * that is filesystem relative.
115 *
116 * dep - address of denode representing the file of interest
117 * findcn - file relative cluster whose filesystem relative cluster number
118 * and/or block number are/is to be found
119 * bnp - address of where to place the filesystem relative block number.
120 * If this pointer is null then don't return this quantity.
121 * cnp - address of where to place the filesystem relative cluster number.
122 * If this pointer is null then don't return this quantity.
123 * sp - pointer to returned block size
124 *
125 * NOTE: Either bnp or cnp must be non-null.
126 * This function has one side effect. If the requested file relative cluster
127 * is beyond the end of file, then the actual number of clusters in the file
128 * is returned in *cnp. This is useful for determining how long a directory is.
129 * If cnp is null, nothing is returned.
130 */
131 int
pcbmap(struct denode * dep,u_long findcn,daddr_t * bnp,u_long * cnp,int * sp)132 pcbmap(struct denode *dep, u_long findcn, daddr_t *bnp, u_long *cnp, int *sp)
133 {
134 int error;
135 u_long i;
136 u_long cn;
137 u_long prevcn = 0; /* XXX: prevcn could be used uninitialized */
138 u_long byteoffset;
139 u_long bn;
140 u_long bo;
141 struct m_buf *bp = NULL;
142 u_long bp_bn = -1;
143 struct msdosfsmount *pmp = dep->de_pmp;
144 u_long bsize;
145
146 assert(bnp != NULL || cnp != NULL || sp != NULL);
147
148 cn = dep->de_StartCluster;
149 /*
150 * The "file" that makes up the root directory is contiguous,
151 * permanently allocated, of fixed size, and is not made up of
152 * clusters. If the cluster number is beyond the end of the root
153 * directory, then return the number of clusters in the file.
154 */
155 if (cn == MSDOSFSROOT) {
156 if (dep->de_Attributes & ATTR_DIRECTORY) {
157 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
158 if (cnp)
159 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
160 return (E2BIG);
161 }
162 if (bnp)
163 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
164 if (cnp)
165 *cnp = MSDOSFSROOT;
166 if (sp)
167 *sp = MIN(pmp->pm_bpcluster,
168 dep->de_FileSize - de_cn2off(pmp, findcn));
169 return (0);
170 } else { /* just an empty file */
171 if (cnp)
172 *cnp = 0;
173 return (E2BIG);
174 }
175 }
176
177 /*
178 * All other files do I/O in cluster sized blocks
179 */
180 if (sp)
181 *sp = pmp->pm_bpcluster;
182
183 /*
184 * Rummage around in the FAT cache, maybe we can avoid tromping
185 * through every FAT entry for the file. And, keep track of how far
186 * off the cache was from where we wanted to be.
187 */
188 i = 0;
189 fc_lookup(dep, findcn, &i, &cn);
190
191 /*
192 * Handle all other files or directories the normal way.
193 */
194 for (; i < findcn; i++) {
195 /*
196 * Stop with all reserved clusters, not just with EOF.
197 */
198 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
199 goto hiteof;
200 byteoffset = FATOFS(pmp, cn);
201 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
202 if (bn != bp_bn) {
203 if (bp)
204 brelse(bp);
205 error = bread((void *)pmp->pm_devvp, bn, bsize,
206 NOCRED, &bp);
207 if (error) {
208 brelse(bp);
209 return (error);
210 }
211 bp_bn = bn;
212 }
213 prevcn = cn;
214 if (bo >= bsize) {
215 if (bp)
216 brelse(bp);
217 return (EIO);
218 }
219 if (FAT32(pmp))
220 cn = getulong(bp->b_data + bo);
221 else
222 cn = getushort(bp->b_data + bo);
223 if (FAT12(pmp) && (prevcn & 1))
224 cn >>= 4;
225 cn &= pmp->pm_fatmask;
226
227 /*
228 * Force the special cluster numbers
229 * to be the same for all cluster sizes
230 * to let the rest of msdosfs handle
231 * all cases the same.
232 */
233 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
234 cn |= ~pmp->pm_fatmask;
235 }
236
237 if (!MSDOSFSEOF(pmp, cn)) {
238 if (bp)
239 brelse(bp);
240 if (bnp)
241 *bnp = cntobn(pmp, cn);
242 if (cnp)
243 *cnp = cn;
244 fc_setcache(dep, FC_LASTMAP, i, cn);
245 return (0);
246 }
247
248 hiteof:
249 if (cnp)
250 *cnp = i;
251 if (bp)
252 brelse(bp);
253 /* update last file cluster entry in the FAT cache */
254 fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
255 return (E2BIG);
256 }
257
258 /*
259 * Find the closest entry in the FAT cache to the cluster we are looking
260 * for.
261 */
262 static void
fc_lookup(struct denode * dep,u_long findcn,u_long * frcnp,u_long * fsrcnp)263 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp)
264 {
265 int i;
266 u_long cn;
267 struct fatcache *closest = NULL;
268
269 for (i = 0; i < FC_SIZE; i++) {
270 cn = dep->de_fc[i].fc_frcn;
271 if (cn != FCE_EMPTY && cn <= findcn) {
272 if (closest == NULL || cn > closest->fc_frcn)
273 closest = &dep->de_fc[i];
274 }
275 }
276 if (closest) {
277 *frcnp = closest->fc_frcn;
278 *fsrcnp = closest->fc_fsrcn;
279 }
280 }
281
282 /*
283 * Purge the FAT cache in denode dep of all entries relating to file
284 * relative cluster frcn and beyond.
285 */
286 void
fc_purge(struct denode * dep,u_int frcn)287 fc_purge(struct denode *dep, u_int frcn)
288 {
289 int i;
290 struct fatcache *fcp;
291
292 fcp = dep->de_fc;
293 for (i = 0; i < FC_SIZE; i++, fcp++) {
294 if (fcp->fc_frcn >= frcn)
295 fcp->fc_frcn = FCE_EMPTY;
296 }
297 }
298
299 /*
300 * Update the FAT.
301 * If mirroring the FAT, update all copies, with the first copy as last.
302 * Else update only the current FAT (ignoring the others).
303 *
304 * pmp - msdosfsmount structure for filesystem to update
305 * bp - addr of modified FAT block
306 * fatbn - block number relative to begin of filesystem of the modified FAT block.
307 */
308 static void
updatefats(struct msdosfsmount * pmp,struct m_buf * bp,u_long fatbn)309 updatefats(struct msdosfsmount *pmp, struct m_buf *bp, u_long fatbn)
310 {
311 struct m_buf *bpn;
312 int cleanfat, i;
313
314 #ifdef MSDOSFS_DEBUG
315 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn);
316 #endif
317
318 if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
319 /*
320 * Now copy the block(s) of the modified FAT to the other copies of
321 * the FAT and write them out. This is faster than reading in the
322 * other FATs and then writing them back out. This could tie up
323 * the FAT for quite a while. Preventing others from accessing it.
324 * To prevent us from going after the FAT quite so much we use
325 * delayed writes, unless they specified "synchronous" when the
326 * filesystem was mounted. If synch is asked for then use
327 * bwrite()'s and really slow things down.
328 */
329 if (fatbn != pmp->pm_fatblk || FAT12(pmp))
330 cleanfat = 0;
331 else if (FAT16(pmp))
332 cleanfat = 16;
333 else
334 cleanfat = 32;
335 for (i = 1; i < pmp->pm_FATs; i++) {
336 fatbn += pmp->pm_FATsecs;
337 /* getblk() never fails */
338 bpn = getblk((void *)pmp->pm_devvp, fatbn,
339 bp->b_bcount, 0, 0, 0);
340 memcpy(bpn->b_data, bp->b_data, bp->b_bcount);
341 /* Force the clean bit on in the other copies. */
342 if (cleanfat == 16)
343 ((uint8_t *)bpn->b_data)[3] |= 0x80;
344 else if (cleanfat == 32)
345 ((uint8_t *)bpn->b_data)[7] |= 0x08;
346 if (SYNCHRONOUS_WRITES(pmp))
347 bwrite(bpn);
348 else
349 bdwrite(bpn);
350 }
351 }
352
353 /*
354 * Write out the first (or current) FAT last.
355 */
356 if (SYNCHRONOUS_WRITES(pmp))
357 bwrite(bp);
358 else
359 bdwrite(bp);
360 }
361
362 /*
363 * Updating entries in 12 bit FATs is a pain in the butt.
364 *
365 * The following picture shows where nibbles go when moving from a 12 bit
366 * cluster number into the appropriate bytes in the FAT.
367 *
368 * byte m byte m+1 byte m+2
369 * +----+----+ +----+----+ +----+----+
370 * | 0 1 | | 2 3 | | 4 5 | FAT bytes
371 * +----+----+ +----+----+ +----+----+
372 *
373 * +----+----+----+ +----+----+----+
374 * | 3 0 1 | | 4 5 2 |
375 * +----+----+----+ +----+----+----+
376 * cluster n cluster n+1
377 *
378 * Where n is even. m = n + (n >> 2)
379 *
380 */
381 static __inline void
usemap_alloc(struct msdosfsmount * pmp,u_long cn)382 usemap_alloc(struct msdosfsmount *pmp, u_long cn)
383 {
384
385 assert(cn <= pmp->pm_maxcluster);
386 assert((pmp->pm_flags & MSDOSFSMNT_RONLY) == 0);
387 assert((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
388 == 0);
389 assert(pmp->pm_freeclustercount > 0);
390
391 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS);
392 pmp->pm_freeclustercount--;
393 pmp->pm_flags |= MSDOSFS_FSIMOD;
394 }
395
396 static __inline void
usemap_free(struct msdosfsmount * pmp,u_long cn)397 usemap_free(struct msdosfsmount *pmp, u_long cn)
398 {
399
400 assert(cn <= pmp->pm_maxcluster);
401 assert((pmp->pm_flags & MSDOSFSMNT_RONLY) == 0);
402 assert((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
403 != 0);
404
405 pmp->pm_freeclustercount++;
406 pmp->pm_flags |= MSDOSFS_FSIMOD;
407 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1U << (cn % N_INUSEBITS));
408 }
409
410 void
clusterfree(struct msdosfsmount * pmp,u_long cluster)411 clusterfree(struct msdosfsmount *pmp, u_long cluster)
412 {
413 int error;
414 u_long oldcn;
415
416 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
417 if (error != 0)
418 return;
419 /*
420 * If the cluster was successfully marked free, then update
421 * the count of free clusters, and turn off the "allocated"
422 * bit in the "in use" cluster bit map.
423 */
424 usemap_free(pmp, cluster);
425 }
426
427 /*
428 * Get or Set or 'Get and Set' the cluster'th entry in the FAT.
429 *
430 * function - whether to get or set a FAT entry
431 * pmp - address of the msdosfsmount structure for the filesystem
432 * whose FAT is to be manipulated.
433 * cn - which cluster is of interest
434 * oldcontents - address of a word that is to receive the contents of the
435 * cluster'th entry if this is a get function
436 * newcontents - the new value to be written into the cluster'th element of
437 * the FAT if this is a set function.
438 *
439 * This function can also be used to free a cluster by setting the FAT entry
440 * for a cluster to 0.
441 *
442 * All copies of the FAT are updated if this is a set function. NOTE: If
443 * fatentry() marks a cluster as free it does not update the inusemap in
444 * the msdosfsmount structure. This is left to the caller.
445 */
446 int
fatentry(int function,struct msdosfsmount * pmp,u_long cn,u_long * oldcontents,u_long newcontents)447 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents,
448 u_long newcontents)
449 {
450 int error;
451 u_long readcn;
452 u_long bn, bo, bsize, byteoffset;
453 struct m_buf *bp;
454
455 #ifdef MSDOSFS_DEBUG
456 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n",
457 function, pmp, cn, oldcontents, newcontents);
458 #endif
459
460 #ifdef DIAGNOSTIC
461 /*
462 * Be sure they asked us to do something.
463 */
464 if ((function & (FAT_SET | FAT_GET)) == 0) {
465 #ifdef MSDOSFS_DEBUG
466 printf("fatentry(): function code doesn't specify get or set\n");
467 #endif
468 return (EINVAL);
469 }
470
471 /*
472 * If they asked us to return a cluster number but didn't tell us
473 * where to put it, give them an error.
474 */
475 if ((function & FAT_GET) && oldcontents == NULL) {
476 #ifdef MSDOSFS_DEBUG
477 printf("fatentry(): get function with no place to put result\n");
478 #endif
479 return (EINVAL);
480 }
481 #endif
482
483 /*
484 * Be sure the requested cluster is in the filesystem.
485 */
486 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
487 return (EINVAL);
488
489 byteoffset = FATOFS(pmp, cn);
490 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
491 error = bread((void *)pmp->pm_devvp, bn, bsize, NOCRED, &bp);
492 if (error) {
493 brelse(bp);
494 return (error);
495 }
496
497 if (function & FAT_GET) {
498 if (FAT32(pmp))
499 readcn = getulong(bp->b_data + bo);
500 else
501 readcn = getushort(bp->b_data + bo);
502 if (FAT12(pmp) & (cn & 1))
503 readcn >>= 4;
504 readcn &= pmp->pm_fatmask;
505 /* map reserved FAT entries to same values for all FATs */
506 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
507 readcn |= ~pmp->pm_fatmask;
508 *oldcontents = readcn;
509 }
510 if (function & FAT_SET) {
511 switch (pmp->pm_fatmask) {
512 case FAT12_MASK:
513 readcn = getushort(bp->b_data + bo);
514 if (cn & 1) {
515 readcn &= 0x000f;
516 readcn |= newcontents << 4;
517 } else {
518 readcn &= 0xf000;
519 readcn |= newcontents & 0xfff;
520 }
521 putushort(bp->b_data + bo, readcn);
522 break;
523 case FAT16_MASK:
524 putushort(bp->b_data + bo, newcontents);
525 break;
526 case FAT32_MASK:
527 /*
528 * According to spec we have to retain the
529 * high order bits of the FAT entry.
530 */
531 readcn = getulong(bp->b_data + bo);
532 readcn &= ~FAT32_MASK;
533 readcn |= newcontents & FAT32_MASK;
534 putulong(bp->b_data + bo, readcn);
535 break;
536 }
537 updatefats(pmp, bp, bn);
538 bp = NULL;
539 pmp->pm_fmod = 1;
540 }
541 if (bp)
542 brelse(bp);
543 return (0);
544 }
545
546 /*
547 * Update a contiguous cluster chain
548 *
549 * pmp - mount point
550 * start - first cluster of chain
551 * count - number of clusters in chain
552 * fillwith - what to write into FAT entry of last cluster
553 */
554 static int
fatchain(struct msdosfsmount * pmp,u_long start,u_long count,u_long fillwith)555 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith)
556 {
557 int error;
558 u_long bn, bo, bsize, byteoffset, readcn, newc;
559 struct m_buf *bp;
560
561 #ifdef MSDOSFS_DEBUG
562 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n",
563 pmp, start, count, fillwith);
564 #endif
565 /*
566 * Be sure the clusters are in the filesystem.
567 */
568 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
569 return (EINVAL);
570
571 while (count > 0) {
572 byteoffset = FATOFS(pmp, start);
573 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
574 error = bread((void *)pmp->pm_devvp, bn, bsize, NOCRED, &bp);
575 if (error) {
576 brelse(bp);
577 return (error);
578 }
579 while (count > 0) {
580 start++;
581 newc = --count > 0 ? start : fillwith;
582 switch (pmp->pm_fatmask) {
583 case FAT12_MASK:
584 readcn = getushort(bp->b_data + bo);
585 if (start & 1) {
586 readcn &= 0xf000;
587 readcn |= newc & 0xfff;
588 } else {
589 readcn &= 0x000f;
590 readcn |= newc << 4;
591 }
592 putushort(bp->b_data + bo, readcn);
593 bo++;
594 if (!(start & 1))
595 bo++;
596 break;
597 case FAT16_MASK:
598 putushort(bp->b_data + bo, newc);
599 bo += 2;
600 break;
601 case FAT32_MASK:
602 readcn = getulong(bp->b_data + bo);
603 readcn &= ~pmp->pm_fatmask;
604 readcn |= newc & pmp->pm_fatmask;
605 putulong(bp->b_data + bo, readcn);
606 bo += 4;
607 break;
608 }
609 if (bo >= bsize)
610 break;
611 }
612 updatefats(pmp, bp, bn);
613 }
614 pmp->pm_fmod = 1;
615 return (0);
616 }
617
618 /*
619 * Check the length of a free cluster chain starting at start.
620 *
621 * pmp - mount point
622 * start - start of chain
623 * count - maximum interesting length
624 */
625 static int
chainlength(struct msdosfsmount * pmp,u_long start,u_long count)626 chainlength(struct msdosfsmount *pmp, u_long start, u_long count)
627 {
628 u_long idx, max_idx;
629 u_int map;
630 u_long len;
631
632 if (start > pmp->pm_maxcluster)
633 return (0);
634 max_idx = pmp->pm_maxcluster / N_INUSEBITS;
635 idx = start / N_INUSEBITS;
636 start %= N_INUSEBITS;
637 map = pmp->pm_inusemap[idx];
638 map &= ~((1 << start) - 1);
639 if (map) {
640 len = ffs(map) - 1 - start;
641 len = MIN(len, count);
642 if (start + len > pmp->pm_maxcluster)
643 len = pmp->pm_maxcluster - start + 1;
644 return (len);
645 }
646 len = N_INUSEBITS - start;
647 if (len >= count) {
648 len = count;
649 if (start + len > pmp->pm_maxcluster)
650 len = pmp->pm_maxcluster - start + 1;
651 return (len);
652 }
653 while (++idx <= max_idx) {
654 if (len >= count)
655 break;
656 map = pmp->pm_inusemap[idx];
657 if (map) {
658 len += ffs(map) - 1;
659 break;
660 }
661 len += N_INUSEBITS;
662 }
663 len = MIN(len, count);
664 if (start + len > pmp->pm_maxcluster)
665 len = pmp->pm_maxcluster - start + 1;
666 return (len);
667 }
668
669 /*
670 * Allocate contiguous free clusters.
671 *
672 * pmp - mount point.
673 * start - start of cluster chain.
674 * count - number of clusters to allocate.
675 * fillwith - put this value into the FAT entry for the
676 * last allocated cluster.
677 * retcluster - put the first allocated cluster's number here.
678 * got - how many clusters were actually allocated.
679 */
680 static int
chainalloc(struct msdosfsmount * pmp,u_long start,u_long count,u_long fillwith,u_long * retcluster,u_long * got)681 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count,
682 u_long fillwith, u_long *retcluster, u_long *got)
683 {
684 int error;
685 u_long cl, n;
686
687 assert((pmp->pm_flags & MSDOSFSMNT_RONLY) == 0);
688
689 for (cl = start, n = count; n-- > 0;)
690 usemap_alloc(pmp, cl++);
691 pmp->pm_nxtfree = start + count;
692 if (pmp->pm_nxtfree > pmp->pm_maxcluster)
693 pmp->pm_nxtfree = CLUST_FIRST;
694 pmp->pm_flags |= MSDOSFS_FSIMOD;
695 error = fatchain(pmp, start, count, fillwith);
696 if (error != 0) {
697 for (cl = start, n = count; n-- > 0;)
698 usemap_free(pmp, cl++);
699 return (error);
700 }
701 #ifdef MSDOSFS_DEBUG
702 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n",
703 start, count);
704 #endif
705 if (retcluster)
706 *retcluster = start;
707 if (got)
708 *got = count;
709 return (0);
710 }
711
712 /*
713 * Allocate contiguous free clusters.
714 *
715 * pmp - mount point.
716 * start - preferred start of cluster chain.
717 * count - number of clusters requested.
718 * fillwith - put this value into the FAT entry for the
719 * last allocated cluster.
720 * retcluster - put the first allocated cluster's number here.
721 * got - how many clusters were actually allocated.
722 */
723 int
clusteralloc(struct msdosfsmount * pmp,u_long start,u_long count,u_long fillwith,u_long * retcluster,u_long * got)724 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count,
725 u_long fillwith, u_long *retcluster, u_long *got)
726 {
727 int error;
728
729 error = clusteralloc1(pmp, start, count, fillwith, retcluster, got);
730 return (error);
731 }
732
733 static int
clusteralloc1(struct msdosfsmount * pmp,u_long start,u_long count,u_long fillwith,u_long * retcluster,u_long * got)734 clusteralloc1(struct msdosfsmount *pmp, u_long start, u_long count,
735 u_long fillwith, u_long *retcluster, u_long *got)
736 {
737 u_long idx;
738 u_long len, newst, foundl, cn, l;
739 u_long foundcn = 0; /* XXX: foundcn could be used uninitialized */
740 u_int map;
741
742 MSDOSFS_DPRINTF(("clusteralloc(): find %lu clusters\n", count));
743
744 if (start) {
745 if ((len = chainlength(pmp, start, count)) >= count)
746 return (chainalloc(pmp, start, count, fillwith, retcluster, got));
747 } else
748 len = 0;
749
750 newst = pmp->pm_nxtfree;
751 foundl = 0;
752
753 for (cn = newst; cn <= pmp->pm_maxcluster;) {
754 idx = cn / N_INUSEBITS;
755 map = pmp->pm_inusemap[idx];
756 map |= (1U << (cn % N_INUSEBITS)) - 1;
757 if (map != FULL_RUN) {
758 cn = idx * N_INUSEBITS + ffs(map ^ FULL_RUN) - 1;
759 if ((l = chainlength(pmp, cn, count)) >= count)
760 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
761 if (l > foundl) {
762 foundcn = cn;
763 foundl = l;
764 }
765 cn += l + 1;
766 continue;
767 }
768 cn += N_INUSEBITS - cn % N_INUSEBITS;
769 }
770 for (cn = 0; cn < newst;) {
771 idx = cn / N_INUSEBITS;
772 map = pmp->pm_inusemap[idx];
773 map |= (1U << (cn % N_INUSEBITS)) - 1;
774 if (map != FULL_RUN) {
775 cn = idx * N_INUSEBITS + ffs(map ^ FULL_RUN) - 1;
776 if ((l = chainlength(pmp, cn, count)) >= count)
777 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
778 if (l > foundl) {
779 foundcn = cn;
780 foundl = l;
781 }
782 cn += l + 1;
783 continue;
784 }
785 cn += N_INUSEBITS - cn % N_INUSEBITS;
786 }
787
788 if (!foundl)
789 return (ENOSPC);
790
791 if (len)
792 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
793 else
794 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
795 }
796
797
798 /*
799 * Free a chain of clusters.
800 *
801 * pmp - address of the msdosfs mount structure for the filesystem
802 * containing the cluster chain to be freed.
803 * startcluster - number of the 1st cluster in the chain of clusters to be
804 * freed.
805 */
806 int
freeclusterchain(struct msdosfsmount * pmp,u_long cluster)807 freeclusterchain(struct msdosfsmount *pmp, u_long cluster)
808 {
809 int error;
810 struct m_buf *bp = NULL;
811 u_long bn, bo, bsize, byteoffset;
812 u_long readcn, lbn = -1;
813
814 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
815 byteoffset = FATOFS(pmp, cluster);
816 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
817 if (lbn != bn) {
818 if (bp)
819 updatefats(pmp, bp, lbn);
820 error = bread((void *)pmp->pm_devvp, bn, bsize,
821 NOCRED, &bp);
822 if (error) {
823 brelse(bp);
824 return (error);
825 }
826 lbn = bn;
827 }
828 usemap_free(pmp, cluster);
829 switch (pmp->pm_fatmask) {
830 case FAT12_MASK:
831 readcn = getushort(bp->b_data + bo);
832 if (cluster & 1) {
833 cluster = readcn >> 4;
834 readcn &= 0x000f;
835 readcn |= MSDOSFSFREE << 4;
836 } else {
837 cluster = readcn;
838 readcn &= 0xf000;
839 readcn |= MSDOSFSFREE & 0xfff;
840 }
841 putushort(bp->b_data + bo, readcn);
842 break;
843 case FAT16_MASK:
844 cluster = getushort(bp->b_data + bo);
845 putushort(bp->b_data + bo, MSDOSFSFREE);
846 break;
847 case FAT32_MASK:
848 cluster = getulong(bp->b_data + bo);
849 putulong(bp->b_data + bo,
850 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
851 break;
852 }
853 cluster &= pmp->pm_fatmask;
854 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
855 cluster |= pmp->pm_fatmask;
856 }
857 if (bp)
858 updatefats(pmp, bp, bn);
859 return (0);
860 }
861
862 /*
863 * Read in FAT blocks looking for free clusters. For every free cluster
864 * found turn off its corresponding bit in the pm_inusemap.
865 */
866 int
fillinusemap(struct msdosfsmount * pmp)867 fillinusemap(struct msdosfsmount *pmp)
868 {
869 struct m_buf *bp;
870 u_long bn, bo, bsize, byteoffset, cn, readcn;
871 int error;
872
873 bp = NULL;
874
875 /*
876 * Mark all clusters in use, we mark the free ones in the FAT scan
877 * loop further down.
878 */
879 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
880 pmp->pm_inusemap[cn] = FULL_RUN;
881
882 /*
883 * Figure how many free clusters are in the filesystem by ripping
884 * through the FAT counting the number of entries whose content is
885 * zero. These represent free clusters.
886 */
887 pmp->pm_freeclustercount = 0;
888 for (cn = 0; cn <= pmp->pm_maxcluster; cn++) {
889 byteoffset = FATOFS(pmp, cn);
890 bo = byteoffset % pmp->pm_fatblocksize;
891 if (bo == 0) {
892 /* Read new FAT block */
893 if (bp != NULL)
894 brelse(bp);
895 fatblock(pmp, byteoffset, &bn, &bsize, NULL);
896 error = bread((void *)pmp->pm_devvp, bn, bsize,
897 NOCRED, &bp);
898 if (error != 0)
899 return (error);
900 }
901 if (FAT32(pmp))
902 readcn = getulong(bp->b_data + bo);
903 else
904 readcn = getushort(bp->b_data + bo);
905 if (FAT12(pmp) && (cn & 1))
906 readcn >>= 4;
907 readcn &= pmp->pm_fatmask;
908
909 /*
910 * Check if the FAT ID matches the BPB's media descriptor and
911 * all other bits are set to 1.
912 */
913 if (cn == 0 && readcn != ((pmp->pm_fatmask & 0xffffff00) |
914 pmp->pm_bpb.bpbMedia)) {
915 #ifdef MSDOSFS_DEBUG
916 printf("mountmsdosfs(): Media descriptor in BPB"
917 "does not match FAT ID\n");
918 #endif
919 brelse(bp);
920 return (EINVAL);
921 } else if (readcn == CLUST_FREE)
922 usemap_free(pmp, cn);
923 }
924 if (bp != NULL)
925 brelse(bp);
926
927 for (cn = pmp->pm_maxcluster + 1; cn < (pmp->pm_maxcluster +
928 N_INUSEBITS) / N_INUSEBITS; cn++)
929 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS);
930
931 return (0);
932 }
933
934 /*
935 * Allocate a new cluster and chain it onto the end of the file.
936 *
937 * dep - the file to extend
938 * count - number of clusters to allocate
939 * bpp - where to return the address of the buf header for the first new
940 * file block
941 * ncp - where to put cluster number of the first newly allocated cluster
942 * If this pointer is 0, do not return the cluster number.
943 * flags - see fat.h
944 *
945 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
946 * the de_flag field of the denode and it does not change the de_FileSize
947 * field. This is left for the caller to do.
948 */
949 int
m_extendfile(struct denode * dep,u_long count,struct m_buf ** bpp,u_long * ncp,int flags)950 m_extendfile(struct denode *dep, u_long count, struct m_buf **bpp, u_long *ncp,
951 int flags)
952 {
953 int error;
954 u_long frcn;
955 u_long cn, got;
956 struct msdosfsmount *pmp = dep->de_pmp;
957 struct m_buf *bp;
958
959 /*
960 * Don't try to extend the root directory
961 */
962 if (dep->de_StartCluster == MSDOSFSROOT
963 && (dep->de_Attributes & ATTR_DIRECTORY)) {
964 #ifdef MSDOSFS_DEBUG
965 printf("extendfile(): attempt to extend root directory\n");
966 #endif
967 return (ENOSPC);
968 }
969
970 /*
971 * If the "file's last cluster" cache entry is empty, and the file
972 * is not empty, then fill the cache entry by calling pcbmap().
973 */
974 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
975 dep->de_StartCluster != 0) {
976 error = pcbmap(dep, 0xffff, 0, &cn, 0);
977 /* we expect it to return E2BIG */
978 if (error != E2BIG)
979 return (error);
980 }
981
982 dep->de_fc[FC_NEXTTOLASTFC].fc_frcn =
983 dep->de_fc[FC_LASTFC].fc_frcn;
984 dep->de_fc[FC_NEXTTOLASTFC].fc_fsrcn =
985 dep->de_fc[FC_LASTFC].fc_fsrcn;
986 while (count > 0) {
987 /*
988 * Allocate a new cluster chain and cat onto the end of the
989 * file. If the file is empty we make de_StartCluster point
990 * to the new block. Note that de_StartCluster being 0 is
991 * sufficient to be sure the file is empty since we exclude
992 * attempts to extend the root directory above, and the root
993 * dir is the only file with a startcluster of 0 that has
994 * blocks allocated (sort of).
995 */
996 if (dep->de_StartCluster == 0)
997 cn = 0;
998 else
999 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
1000 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got);
1001 if (error)
1002 return (error);
1003
1004 count -= got;
1005
1006 /*
1007 * Give them the filesystem relative cluster number if they want
1008 * it.
1009 */
1010 if (ncp) {
1011 *ncp = cn;
1012 ncp = NULL;
1013 }
1014
1015 if (dep->de_StartCluster == 0) {
1016 dep->de_StartCluster = cn;
1017 frcn = 0;
1018 } else {
1019 error = fatentry(FAT_SET, pmp,
1020 dep->de_fc[FC_LASTFC].fc_fsrcn,
1021 0, cn);
1022 if (error) {
1023 clusterfree(pmp, cn);
1024 return (error);
1025 }
1026 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
1027 }
1028
1029 /*
1030 * Update the "last cluster of the file" entry in the
1031 * denode's FAT cache.
1032 */
1033 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
1034
1035 if ((flags & DE_CLEAR) &&
1036 (dep->de_Attributes & ATTR_DIRECTORY)) {
1037 while (got-- > 0) {
1038 bp = getblk((void *)pmp->pm_devvp,
1039 cntobn(pmp, cn++),
1040 pmp->pm_bpcluster, 0, 0, 0);
1041 clrbuf(bp);
1042 if (bpp) {
1043 *bpp = bp;
1044 bpp = NULL;
1045 } else {
1046 bdwrite(bp);
1047 }
1048 }
1049 }
1050 }
1051
1052 return (0);
1053 }
1054