1 /** $MirOS: src/sys/msdosfs/msdosfs_fat.c,v 1.3 2005/07/03 21:19:02 tg Exp $ */
2 /* $OpenBSD: msdosfs_fat.c,v 1.17 2004/05/16 19:00:51 tedu Exp $ */
3 /* $NetBSD: msdosfs_fat.c,v 1.26 1997/10/17 11:24:02 ws Exp $ */
4
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 /*
53 * kernel include files.
54 */
55 #include <sys/param.h>
56 #include <sys/systm.h>
57 #include <sys/buf.h>
58 #include <sys/file.h>
59 #include <sys/namei.h>
60 #include <sys/mount.h> /* to define statfs structure */
61 #include <sys/vnode.h> /* to define vattr structure */
62 #include <sys/errno.h>
63 #include <sys/dirent.h>
64
65 /*
66 * msdosfs include files.
67 */
68 #include <msdosfs/bpb.h>
69 #include <msdosfs/msdosfsmount.h>
70 #include <msdosfs/direntry.h>
71 #include <msdosfs/denode.h>
72 #include <msdosfs/fat.h>
73
74 /*
75 * Fat cache stats.
76 */
77 int fc_fileextends; /* # of file extends */
78 int fc_lfcempty; /* # of time last file cluster cache entry
79 * was empty */
80 int fc_bmapcalls; /* # of times pcbmap was called */
81
82 #define LMMAX 20
83 int fc_lmdistance[LMMAX]; /* counters for how far off the last
84 * cluster mapped entry was. */
85 int fc_largedistance; /* off by more than LMMAX */
86
87 static void fatblock(struct msdosfsmount *, uint32_t, uint32_t *, uint32_t *,
88 uint32_t *);
89 void updatefats(struct msdosfsmount *, struct buf *, uint32_t);
90 static __inline void usemap_free(struct msdosfsmount *, uint32_t);
91 static __inline void usemap_alloc(struct msdosfsmount *, uint32_t);
92 static int fatchain(struct msdosfsmount *, uint32_t, uint32_t, uint32_t);
93 int chainlength(struct msdosfsmount *, uint32_t, uint32_t);
94 int chainalloc(struct msdosfsmount *, uint32_t, uint32_t, uint32_t, uint32_t *,
95 uint32_t *);
96
97 static void
fatblock(pmp,ofs,bnp,sizep,bop)98 fatblock(pmp, ofs, bnp, sizep, bop)
99 struct msdosfsmount *pmp;
100 uint32_t ofs;
101 uint32_t *bnp;
102 uint32_t *sizep;
103 uint32_t *bop;
104 {
105 uint32_t bn, size;
106
107 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
108 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
109 * pmp->pm_BytesPerSec;
110 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
111
112 if (bnp)
113 *bnp = bn;
114 if (sizep)
115 *sizep = size;
116 if (bop)
117 *bop = ofs % pmp->pm_fatblocksize;
118 }
119
120 /*
121 * Map the logical cluster number of a file into a physical disk sector
122 * that is filesystem relative.
123 *
124 * dep - address of denode representing the file of interest
125 * findcn - file relative cluster whose filesystem relative cluster number
126 * and/or block number are/is to be found
127 * bnp - address of where to place the file system relative block number.
128 * If this pointer is null then don't return this quantity.
129 * cnp - address of where to place the file system relative cluster number.
130 * If this pointer is null then don't return this quantity.
131 *
132 * NOTE: Either bnp or cnp must be non-null.
133 * This function has one side effect. If the requested file relative cluster
134 * is beyond the end of file, then the actual number of clusters in the file
135 * is returned in *cnp. This is useful for determining how long a directory is.
136 * If cnp is null, nothing is returned.
137 */
138 int
pcbmap(dep,findcn,bnp,cnp,sp)139 pcbmap(dep, findcn, bnp, cnp, sp)
140 struct denode *dep;
141 uint32_t findcn; /* file relative cluster to get */
142 daddr_t *bnp; /* returned filesys relative blk number */
143 uint32_t *cnp; /* returned cluster number */
144 int *sp; /* returned block size */
145 {
146 int error;
147 uint32_t i;
148 uint32_t cn;
149 uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */
150 uint32_t byteoffset;
151 uint32_t bn;
152 uint32_t bo;
153 struct buf *bp = NULL;
154 uint32_t bp_bn = -1;
155 struct msdosfsmount *pmp = dep->de_pmp;
156 uint32_t bsize;
157
158 fc_bmapcalls++;
159
160 /*
161 * If they don't give us someplace to return a value then don't
162 * bother doing anything.
163 */
164 if (bnp == NULL && cnp == NULL && sp == NULL)
165 return (0);
166
167 cn = dep->de_StartCluster;
168 /*
169 * The "file" that makes up the root directory is contiguous,
170 * permanently allocated, of fixed size, and is not made up of
171 * clusters. If the cluster number is beyond the end of the root
172 * directory, then return the number of clusters in the file.
173 */
174 if (cn == MSDOSFSROOT) {
175 if (dep->de_Attributes & ATTR_DIRECTORY) {
176 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
177 if (cnp)
178 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
179 return (E2BIG);
180 }
181 if (bnp)
182 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
183 if (cnp)
184 *cnp = MSDOSFSROOT;
185 if (sp)
186 *sp = min(pmp->pm_bpcluster,
187 dep->de_FileSize - de_cn2off(pmp, findcn));
188 return (0);
189 } else { /* just an empty file */
190 if (cnp)
191 *cnp = 0;
192 return (E2BIG);
193 }
194 }
195
196 /*
197 * All other files do I/O in cluster sized blocks
198 */
199 if (sp)
200 *sp = pmp->pm_bpcluster;
201
202 /*
203 * Rummage around in the fat cache, maybe we can avoid tromping
204 * thru every fat entry for the file. And, keep track of how far
205 * off the cache was from where we wanted to be.
206 */
207 i = 0;
208 fc_lookup(dep, findcn, &i, &cn);
209 if ((bn = findcn - i) >= LMMAX)
210 fc_largedistance++;
211 else
212 fc_lmdistance[bn]++;
213
214 /*
215 * Handle all other files or directories the normal way.
216 */
217 for (; i < findcn; i++) {
218 /*
219 * Stop with all reserved clusters, not just with EOF.
220 */
221 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
222 goto hiteof;
223 byteoffset = FATOFS(pmp, cn);
224 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
225 if (bn != bp_bn) {
226 if (bp)
227 brelse(bp);
228 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
229 if (error) {
230 brelse(bp);
231 return (error);
232 }
233 bp_bn = bn;
234 }
235 prevcn = cn;
236 if (bo >= bsize) {
237 if (bp)
238 brelse(bp);
239 return (EIO);
240 }
241 if (FAT32(pmp))
242 cn = getulong(&bp->b_data[bo]);
243 else
244 cn = getushort(&bp->b_data[bo]);
245 if (FAT12(pmp) && (prevcn & 1))
246 cn >>= 4;
247 cn &= pmp->pm_fatmask;
248
249 /*
250 * Force the special cluster numbers
251 * to be the same for all cluster sizes
252 * to let the rest of msdosfs handle
253 * all cases the same.
254 */
255 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
256 cn |= ~pmp->pm_fatmask;
257 }
258
259 if (!MSDOSFSEOF(pmp, cn)) {
260 if (bp)
261 brelse(bp);
262 if (bnp)
263 *bnp = cntobn(pmp, cn);
264 if (cnp)
265 *cnp = cn;
266 fc_setcache(dep, FC_LASTMAP, i, cn);
267 return (0);
268 }
269
270 hiteof:;
271 if (cnp)
272 *cnp = i;
273 if (bp)
274 brelse(bp);
275 /* update last file cluster entry in the fat cache */
276 fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
277 return (E2BIG);
278 }
279
280 /*
281 * Find the closest entry in the fat cache to the cluster we are looking
282 * for.
283 */
284 void
fc_lookup(dep,findcn,frcnp,fsrcnp)285 fc_lookup(dep, findcn, frcnp, fsrcnp)
286 struct denode *dep;
287 uint32_t findcn;
288 uint32_t *frcnp;
289 uint32_t *fsrcnp;
290 {
291 int i;
292 uint32_t cn;
293 struct fatcache *closest = 0;
294
295 for (i = 0; i < FC_SIZE; i++) {
296 cn = dep->de_fc[i].fc_frcn;
297 if (cn != FCE_EMPTY && cn <= findcn) {
298 if (closest == 0 || cn > closest->fc_frcn)
299 closest = &dep->de_fc[i];
300 }
301 }
302 if (closest) {
303 *frcnp = closest->fc_frcn;
304 *fsrcnp = closest->fc_fsrcn;
305 }
306 }
307
308 /*
309 * Purge the fat cache in denode dep of all entries relating to file
310 * relative cluster frcn and beyond.
311 */
312 void
fc_purge(dep,frcn)313 fc_purge(dep, frcn)
314 struct denode *dep;
315 u_int frcn;
316 {
317 int i;
318 struct fatcache *fcp;
319
320 fcp = dep->de_fc;
321 for (i = 0; i < FC_SIZE; i++, fcp++) {
322 if (fcp->fc_frcn >= frcn)
323 fcp->fc_frcn = FCE_EMPTY;
324 }
325 }
326
327 /*
328 * Update the fat.
329 * If mirroring the fat, update all copies, with the first copy as last.
330 * Else update only the current fat (ignoring the others).
331 *
332 * pmp - msdosfsmount structure for filesystem to update
333 * bp - addr of modified fat block
334 * fatbn - block number relative to begin of filesystem of the modified fat block.
335 */
336 void
updatefats(pmp,bp,fatbn)337 updatefats(pmp, bp, fatbn)
338 struct msdosfsmount *pmp;
339 struct buf *bp;
340 uint32_t fatbn;
341 {
342 int i;
343 struct buf *bpn;
344
345 #ifdef MSDOSFS_DEBUG
346 printf("updatefats(pmp %08, buf %x, fatbn %ld)\n", pmp, bp, fatbn);
347 #endif
348
349 /*
350 * If we have an FSInfo block, update it.
351 */
352 if (pmp->pm_fsinfo) {
353 uint32_t cn = pmp->pm_nxtfree;
354
355 if (pmp->pm_freeclustercount
356 && (pmp->pm_inusemap[cn / N_INUSEBITS]
357 & (1 << (cn % N_INUSEBITS)))) {
358 /*
359 * The cluster indicated in FSInfo isn't free
360 * any longer. Got get a new free one.
361 */
362 for (cn = 0; cn < pmp->pm_maxcluster; cn++)
363 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
364 break;
365 pmp->pm_nxtfree = cn
366 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
367 ^ (u_int)-1) - 1;
368 }
369 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, 1024, NOCRED, &bpn) != 0) {
370 /*
371 * Ignore the error, but turn off FSInfo update for the future.
372 */
373 pmp->pm_fsinfo = 0;
374 brelse(bpn);
375 } else {
376 struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
377
378 putulong(fp->fsinfree, pmp->pm_freeclustercount);
379 putulong(fp->fsinxtfree, pmp->pm_nxtfree);
380 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
381 bwrite(bpn);
382 else
383 bdwrite(bpn);
384 }
385 }
386
387 if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
388 /*
389 * Now copy the block(s) of the modified fat to the other copies of
390 * the fat and write them out. This is faster than reading in the
391 * other fats and then writing them back out. This could tie up
392 * the fat for quite a while. Preventing others from accessing it.
393 * To prevent us from going after the fat quite so much we use
394 * delayed writes, unless they specfied "synchronous" when the
395 * filesystem was mounted. If synch is asked for then use
396 * bwrite()'s and really slow things down.
397 */
398 for (i = 1; i < pmp->pm_FATs; i++) {
399 fatbn += pmp->pm_FATsecs;
400 /* getblk() never fails */
401 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0);
402 bcopy(bp->b_data, bpn->b_data, bp->b_bcount);
403 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
404 bwrite(bpn);
405 else
406 bdwrite(bpn);
407 }
408 }
409
410 /*
411 * Write out the first (or current) fat last.
412 */
413 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
414 bwrite(bp);
415 else
416 bdwrite(bp);
417 /*
418 * Maybe update fsinfo sector here?
419 */
420 }
421
422 /*
423 * Updating entries in 12 bit fats is a pain in the butt.
424 *
425 * The following picture shows where nibbles go when moving from a 12 bit
426 * cluster number into the appropriate bytes in the FAT.
427 *
428 * byte m byte m+1 byte m+2
429 * +----+----+ +----+----+ +----+----+
430 * | 0 1 | | 2 3 | | 4 5 | FAT bytes
431 * +----+----+ +----+----+ +----+----+
432 *
433 * +----+----+----+ +----+----+----+
434 * | 3 0 1 | | 4 5 2 |
435 * +----+----+----+ +----+----+----+
436 * cluster n cluster n+1
437 *
438 * Where n is even. m = n + (n >> 2)
439 *
440 */
441 static __inline void
usemap_alloc(pmp,cn)442 usemap_alloc(pmp, cn)
443 struct msdosfsmount *pmp;
444 uint32_t cn;
445 {
446
447 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
448 pmp->pm_freeclustercount--;
449 }
450
451 static __inline void
usemap_free(pmp,cn)452 usemap_free(pmp, cn)
453 struct msdosfsmount *pmp;
454 uint32_t cn;
455 {
456
457 pmp->pm_freeclustercount++;
458 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
459 }
460
461 int
clusterfree(pmp,cluster,oldcnp)462 clusterfree(pmp, cluster, oldcnp)
463 struct msdosfsmount *pmp;
464 uint32_t cluster;
465 uint32_t *oldcnp;
466 {
467 int error;
468 uint32_t oldcn;
469
470 usemap_free(pmp, cluster);
471 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
472 if (error) {
473 usemap_alloc(pmp, cluster);
474 return (error);
475 }
476 /*
477 * If the cluster was successfully marked free, then update
478 * the count of free clusters, and turn off the "allocated"
479 * bit in the "in use" cluster bit map.
480 */
481 if (oldcnp)
482 *oldcnp = oldcn;
483 return (0);
484 }
485
486 /*
487 * Get or Set or 'Get and Set' the cluster'th entry in the fat.
488 *
489 * function - whether to get or set a fat entry
490 * pmp - address of the msdosfsmount structure for the filesystem
491 * whose fat is to be manipulated.
492 * cn - which cluster is of interest
493 * oldcontents - address of a word that is to receive the contents of the
494 * cluster'th entry if this is a get function
495 * newcontents - the new value to be written into the cluster'th element of
496 * the fat if this is a set function.
497 *
498 * This function can also be used to free a cluster by setting the fat entry
499 * for a cluster to 0.
500 *
501 * All copies of the fat are updated if this is a set function. NOTE: If
502 * fatentry() marks a cluster as free it does not update the inusemap in
503 * the msdosfsmount structure. This is left to the caller.
504 */
505 int
fatentry(function,pmp,cn,oldcontents,newcontents)506 fatentry(function, pmp, cn, oldcontents, newcontents)
507 int function;
508 struct msdosfsmount *pmp;
509 uint32_t cn;
510 uint32_t *oldcontents;
511 uint32_t newcontents;
512 {
513 int error;
514 uint32_t readcn;
515 uint32_t bn, bo, bsize, byteoffset;
516 struct buf *bp;
517
518 #ifdef MSDOSFS_DEBUG
519 printf("fatentry(func %d, pmp %08x, clust %d, oldcon %08x, newcon %d)\n",
520 function, pmp, cn, oldcontents, newcontents);
521 #endif
522
523 #ifdef DIAGNOSTIC
524 /*
525 * Be sure they asked us to do something.
526 */
527 if ((function & (FAT_SET | FAT_GET)) == 0) {
528 printf("fatentry(): function code doesn't specify get or set\n");
529 return (EINVAL);
530 }
531
532 /*
533 * If they asked us to return a cluster number but didn't tell us
534 * where to put it, give them an error.
535 */
536 if ((function & FAT_GET) && oldcontents == NULL) {
537 printf("fatentry(): get function with no place to put result\n");
538 return (EINVAL);
539 }
540 #endif
541
542 /*
543 * Be sure the requested cluster is in the filesystem.
544 */
545 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
546 return (EINVAL);
547
548 byteoffset = FATOFS(pmp, cn);
549 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
550 if ((error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp)) != 0) {
551 brelse(bp);
552 return (error);
553 }
554
555 if (function & FAT_GET) {
556 if (FAT32(pmp))
557 readcn = getulong(&bp->b_data[bo]);
558 else
559 readcn = getushort(&bp->b_data[bo]);
560 if (FAT12(pmp) && (cn & 1))
561 readcn >>= 4;
562 readcn &= pmp->pm_fatmask;
563 /* map reserved fat entries to same values for all fats */
564 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
565 readcn |= ~pmp->pm_fatmask;
566 *oldcontents = readcn;
567 }
568 if (function & FAT_SET) {
569 switch (pmp->pm_fatmask) {
570 case FAT12_MASK:
571 readcn = getushort(&bp->b_data[bo]);
572 if (cn & 1) {
573 readcn &= 0x000f;
574 readcn |= newcontents << 4;
575 } else {
576 readcn &= 0xf000;
577 readcn |= newcontents & 0xfff;
578 }
579 putushort(&bp->b_data[bo], readcn);
580 break;
581 case FAT16_MASK:
582 putushort(&bp->b_data[bo], newcontents);
583 break;
584 case FAT32_MASK:
585 /*
586 * According to spec we have to retain the
587 * high order bits of the fat entry.
588 */
589 readcn = getulong(&bp->b_data[bo]);
590 readcn &= ~FAT32_MASK;
591 readcn |= newcontents & FAT32_MASK;
592 putulong(&bp->b_data[bo], readcn);
593 break;
594 }
595 updatefats(pmp, bp, bn);
596 bp = NULL;
597 pmp->pm_fmod = 1;
598 }
599 if (bp)
600 brelse(bp);
601 return (0);
602 }
603
604 /*
605 * Update a contiguous cluster chain
606 *
607 * pmp - mount point
608 * start - first cluster of chain
609 * count - number of clusters in chain
610 * fillwith - what to write into fat entry of last cluster
611 */
612 static int
fatchain(pmp,start,count,fillwith)613 fatchain(pmp, start, count, fillwith)
614 struct msdosfsmount *pmp;
615 uint32_t start;
616 uint32_t count;
617 uint32_t fillwith;
618 {
619 int error;
620 uint32_t bn, bo, bsize, byteoffset, readcn, newc;
621 struct buf *bp;
622
623 #ifdef MSDOSFS_DEBUG
624 printf("fatchain(pmp %08x, start %d, count %d, fillwith %d)\n",
625 pmp, start, count, fillwith);
626 #endif
627 /*
628 * Be sure the clusters are in the filesystem.
629 */
630 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
631 return (EINVAL);
632
633 while (count > 0) {
634 byteoffset = FATOFS(pmp, start);
635 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
636 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
637 if (error) {
638 brelse(bp);
639 return (error);
640 }
641 while (count > 0) {
642 start++;
643 newc = --count > 0 ? start : fillwith;
644 switch (pmp->pm_fatmask) {
645 case FAT12_MASK:
646 readcn = getushort(&bp->b_data[bo]);
647 if (start & 1) {
648 readcn &= 0xf000;
649 readcn |= newc & 0xfff;
650 } else {
651 readcn &= 0x000f;
652 readcn |= newc << 4;
653 }
654 putushort(&bp->b_data[bo], readcn);
655 bo++;
656 if (!(start & 1))
657 bo++;
658 break;
659 case FAT16_MASK:
660 putushort(&bp->b_data[bo], newc);
661 bo += 2;
662 break;
663 case FAT32_MASK:
664 readcn = getulong(&bp->b_data[bo]);
665 readcn &= ~pmp->pm_fatmask;
666 readcn |= newc & pmp->pm_fatmask;
667 putulong(&bp->b_data[bo], readcn);
668 bo += 4;
669 break;
670 }
671 if (bo >= bsize)
672 break;
673 }
674 updatefats(pmp, bp, bn);
675 }
676 pmp->pm_fmod = 1;
677 return (0);
678 }
679
680 /*
681 * Check the length of a free cluster chain starting at start.
682 *
683 * pmp - mount point
684 * start - start of chain
685 * count - maximum interesting length
686 */
687 int
chainlength(pmp,start,count)688 chainlength(pmp, start, count)
689 struct msdosfsmount *pmp;
690 uint32_t start;
691 uint32_t count;
692 {
693 uint32_t idx, max_idx;
694 u_int map;
695 uint32_t len;
696
697 max_idx = pmp->pm_maxcluster / N_INUSEBITS;
698 idx = start / N_INUSEBITS;
699 start %= N_INUSEBITS;
700 map = pmp->pm_inusemap[idx];
701 map &= ~((1 << start) - 1);
702 if (map) {
703 len = ffs(map) - 1 - start;
704 return (len > count ? count : len);
705 }
706 len = N_INUSEBITS - start;
707 if (len >= count)
708 return (count);
709 while (++idx <= max_idx) {
710 if (len >= count)
711 break;
712 if ((map = pmp->pm_inusemap[idx]) != 0) {
713 len += ffs(map) - 1;
714 break;
715 }
716 len += N_INUSEBITS;
717 }
718 return (len > count ? count : len);
719 }
720
721 /*
722 * Allocate contigous free clusters.
723 *
724 * pmp - mount point.
725 * start - start of cluster chain.
726 * count - number of clusters to allocate.
727 * fillwith - put this value into the fat entry for the
728 * last allocated cluster.
729 * retcluster - put the first allocated cluster's number here.
730 * got - how many clusters were actually allocated.
731 */
732 int
chainalloc(pmp,start,count,fillwith,retcluster,got)733 chainalloc(pmp, start, count, fillwith, retcluster, got)
734 struct msdosfsmount *pmp;
735 uint32_t start;
736 uint32_t count;
737 uint32_t fillwith;
738 uint32_t *retcluster;
739 uint32_t *got;
740 {
741 int error;
742 uint32_t cl, n;
743
744 for (cl = start, n = count; n-- > 0;)
745 usemap_alloc(pmp, cl++);
746 if ((error = fatchain(pmp, start, count, fillwith)) != 0)
747 return (error);
748 #ifdef MSDOSFS_DEBUG
749 printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n",
750 start, count);
751 #endif
752 if (retcluster)
753 *retcluster = start;
754 if (got)
755 *got = count;
756 return (0);
757 }
758
759 /*
760 * Allocate contiguous free clusters.
761 *
762 * pmp - mount point.
763 * start - preferred start of cluster chain.
764 * count - number of clusters requested.
765 * fillwith - put this value into the fat entry for the
766 * last allocated cluster.
767 * retcluster - put the first allocated cluster's number here.
768 * got - how many clusters were actually allocated.
769 */
770 int
clusteralloc(pmp,start,count,fillwith,retcluster,got)771 clusteralloc(pmp, start, count, fillwith, retcluster, got)
772 struct msdosfsmount *pmp;
773 uint32_t start;
774 uint32_t count;
775 uint32_t fillwith;
776 uint32_t *retcluster;
777 uint32_t *got;
778 {
779 uint32_t idx;
780 uint32_t len, newst, foundl, cn, l;
781 uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */
782 u_int map;
783
784 #ifdef MSDOSFS_DEBUG
785 printf("clusteralloc(): find %d clusters\n",count);
786 #endif
787 if (start) {
788 if ((len = chainlength(pmp, start, count)) >= count)
789 return (chainalloc(pmp, start, count, fillwith, retcluster, got));
790 } else {
791 /*
792 * This is a new file, initialize start
793 */
794 struct timeval tv;
795
796 microtime(&tv);
797 start = (tv.tv_usec >> 10) | tv.tv_usec;
798 len = 0;
799 }
800
801 /*
802 * Start at a (pseudo) random place to maximize cluster runs
803 * under multiple writers.
804 */
805 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
806 foundl = 0;
807
808 for (cn = newst; cn <= pmp->pm_maxcluster;) {
809 idx = cn / N_INUSEBITS;
810 map = pmp->pm_inusemap[idx];
811 map |= (1 << (cn % N_INUSEBITS)) - 1;
812 if (map != (u_int)-1) {
813 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
814 if ((l = chainlength(pmp, cn, count)) >= count)
815 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
816 if (l > foundl) {
817 foundcn = cn;
818 foundl = l;
819 }
820 cn += l + 1;
821 continue;
822 }
823 cn += N_INUSEBITS - cn % N_INUSEBITS;
824 }
825 for (cn = 0; cn < newst;) {
826 idx = cn / N_INUSEBITS;
827 map = pmp->pm_inusemap[idx];
828 map |= (1 << (cn % N_INUSEBITS)) - 1;
829 if (map != (u_int)-1) {
830 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
831 if ((l = chainlength(pmp, cn, count)) >= count)
832 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
833 if (l > foundl) {
834 foundcn = cn;
835 foundl = l;
836 }
837 cn += l + 1;
838 continue;
839 }
840 cn += N_INUSEBITS - cn % N_INUSEBITS;
841 }
842
843 if (!foundl)
844 return (ENOSPC);
845
846 if (len)
847 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
848 else
849 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
850 }
851
852
853 /*
854 * Free a chain of clusters.
855 *
856 * pmp - address of the msdosfs mount structure for the filesystem
857 * containing the cluster chain to be freed.
858 * startcluster - number of the 1st cluster in the chain of clusters to be
859 * freed.
860 */
861 int
freeclusterchain(pmp,cluster)862 freeclusterchain(pmp, cluster)
863 struct msdosfsmount *pmp;
864 uint32_t cluster;
865 {
866 int error;
867 struct buf *bp = NULL;
868 uint32_t bn, bo, bsize, byteoffset;
869 uint32_t readcn, lbn = -1;
870
871 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
872 byteoffset = FATOFS(pmp, cluster);
873 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
874 if (lbn != bn) {
875 if (bp)
876 updatefats(pmp, bp, lbn);
877 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
878 if (error) {
879 brelse(bp);
880 return (error);
881 }
882 lbn = bn;
883 }
884 usemap_free(pmp, cluster);
885 switch (pmp->pm_fatmask) {
886 case FAT12_MASK:
887 readcn = getushort(&bp->b_data[bo]);
888 if (cluster & 1) {
889 cluster = readcn >> 4;
890 readcn &= 0x000f;
891 readcn |= MSDOSFSFREE << 4;
892 } else {
893 cluster = readcn;
894 readcn &= 0xf000;
895 readcn |= MSDOSFSFREE & 0xfff;
896 }
897 putushort(&bp->b_data[bo], readcn);
898 break;
899 case FAT16_MASK:
900 cluster = getushort(&bp->b_data[bo]);
901 putushort(&bp->b_data[bo], MSDOSFSFREE);
902 break;
903 case FAT32_MASK:
904 cluster = getulong(&bp->b_data[bo]);
905 putulong(&bp->b_data[bo],
906 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
907 break;
908 }
909 cluster &= pmp->pm_fatmask;
910 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
911 cluster |= pmp->pm_fatmask;
912 }
913 if (bp)
914 updatefats(pmp, bp, bn);
915 return (0);
916 }
917
918 /*
919 * Read in fat blocks looking for free clusters. For every free cluster
920 * found turn off its corresponding bit in the pm_inusemap.
921 */
922 int
fillinusemap(pmp)923 fillinusemap(pmp)
924 struct msdosfsmount *pmp;
925 {
926 struct buf *bp = NULL;
927 uint32_t cn, readcn;
928 int error;
929 uint32_t bn, bo, bsize, byteoffset;
930
931 /*
932 * Mark all clusters in use, we mark the free ones in the fat scan
933 * loop further down.
934 */
935 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
936 pmp->pm_inusemap[cn] = (u_int)-1;
937
938 /*
939 * Figure how many free clusters are in the filesystem by ripping
940 * through the fat counting the number of entries whose content is
941 * zero. These represent free clusters.
942 */
943 pmp->pm_freeclustercount = 0;
944 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
945 byteoffset = FATOFS(pmp, cn);
946 bo = byteoffset % pmp->pm_fatblocksize;
947 if (!bo || !bp) {
948 /* Read new FAT block */
949 if (bp)
950 brelse(bp);
951 fatblock(pmp, byteoffset, &bn, &bsize, NULL);
952 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
953 if (error) {
954 brelse(bp);
955 return (error);
956 }
957 }
958 if (FAT32(pmp))
959 readcn = getulong(&bp->b_data[bo]);
960 else
961 readcn = getushort(&bp->b_data[bo]);
962 if (FAT12(pmp) && (cn & 1))
963 readcn >>= 4;
964 readcn &= pmp->pm_fatmask;
965
966 if (readcn == 0)
967 usemap_free(pmp, cn);
968 }
969 brelse(bp);
970 return (0);
971 }
972
973 /*
974 * Allocate a new cluster and chain it onto the end of the file.
975 *
976 * dep - the file to extend
977 * count - number of clusters to allocate
978 * bpp - where to return the address of the buf header for the first new
979 * file block
980 * ncp - where to put cluster number of the first newly allocated cluster
981 * If this pointer is 0, do not return the cluster number.
982 * flags - see fat.h
983 *
984 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
985 * the de_flag field of the denode and it does not change the de_FileSize
986 * field. This is left for the caller to do.
987 */
988 int
extendfile(dep,count,bpp,ncp,flags)989 extendfile(dep, count, bpp, ncp, flags)
990 struct denode *dep;
991 uint32_t count;
992 struct buf **bpp;
993 uint32_t *ncp;
994 int flags;
995 {
996 int error;
997 uint32_t frcn;
998 uint32_t cn, got;
999 struct msdosfsmount *pmp = dep->de_pmp;
1000 struct buf *bp;
1001
1002 /*
1003 * Don't try to extend the root directory
1004 */
1005 if (dep->de_StartCluster == MSDOSFSROOT
1006 && (dep->de_Attributes & ATTR_DIRECTORY)) {
1007 printf("extendfile(): attempt to extend root directory\n");
1008 return (ENOSPC);
1009 }
1010
1011 /*
1012 * If the "file's last cluster" cache entry is empty, and the file
1013 * is not empty, then fill the cache entry by calling pcbmap().
1014 */
1015 fc_fileextends++;
1016 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
1017 dep->de_StartCluster != 0) {
1018 fc_lfcempty++;
1019 error = pcbmap(dep, 0xffff, 0, &cn, 0);
1020 /* we expect it to return E2BIG */
1021 if (error != E2BIG)
1022 return (error);
1023 }
1024
1025 while (count > 0) {
1026 /*
1027 * Allocate a new cluster chain and cat onto the end of the
1028 * file. * If the file is empty we make de_StartCluster point
1029 * to the new block. Note that de_StartCluster being 0 is
1030 * sufficient to be sure the file is empty since we exclude
1031 * attempts to extend the root directory above, and the root
1032 * dir is the only file with a startcluster of 0 that has
1033 * blocks allocated (sort of).
1034 */
1035 if (dep->de_StartCluster == 0)
1036 cn = 0;
1037 else
1038 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
1039 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got);
1040 if (error)
1041 return (error);
1042
1043 count -= got;
1044
1045 /*
1046 * Give them the filesystem relative cluster number if they want
1047 * it.
1048 */
1049 if (ncp) {
1050 *ncp = cn;
1051 ncp = NULL;
1052 }
1053
1054 if (dep->de_StartCluster == 0) {
1055 dep->de_StartCluster = cn;
1056 frcn = 0;
1057 } else {
1058 error = fatentry(FAT_SET, pmp,
1059 dep->de_fc[FC_LASTFC].fc_fsrcn,
1060 0, cn);
1061 if (error) {
1062 clusterfree(pmp, cn, NULL);
1063 return (error);
1064 }
1065 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
1066 }
1067
1068 /*
1069 * Update the "last cluster of the file" entry in the denode's fat
1070 * cache.
1071 */
1072 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
1073
1074 if (flags & DE_CLEAR) {
1075 while (got-- > 0) {
1076 /*
1077 * Get the buf header for the new block of the file.
1078 */
1079 if (dep->de_Attributes & ATTR_DIRECTORY)
1080 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++),
1081 pmp->pm_bpcluster, 0, 0);
1082 else {
1083 bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++),
1084 pmp->pm_bpcluster, 0, 0);
1085 /*
1086 * Do the bmap now, as in msdosfs_write
1087 */
1088 if (pcbmap(dep,
1089 de_bn2cn(pmp, bp->b_lblkno),
1090 &bp->b_blkno, 0, 0))
1091 bp->b_blkno = -1;
1092 if (bp->b_blkno == -1)
1093 panic("extendfile: pcbmap");
1094 }
1095 clrbuf(bp);
1096 if (bpp) {
1097 *bpp = bp;
1098 bpp = NULL;
1099 } else
1100 bdwrite(bp);
1101 }
1102 }
1103 }
1104
1105 return (0);
1106 }
1107