/
msdosfs_fat.c
1105 lines (1031 loc) · 28 KB
/
msdosfs_fat.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/* $OpenBSD: msdosfs_fat.c,v 1.18 2006/10/03 19:49:06 pedro Exp $ */
/* $NetBSD: msdosfs_fat.c,v 1.26 1997/10/17 11:24:02 ws Exp $ */
/*-
* Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
* Copyright (C) 1994, 1995, 1997 TooLs GmbH.
* All rights reserved.
* Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by TooLs GmbH.
* 4. The name of TooLs GmbH may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Written by Paul Popelka (paulp@uts.amdahl.com)
*
* You can do anything you want with this software, just don't say you wrote
* it, and don't remove this notice.
*
* This software is provided "as is".
*
* The author supplies this software to be publicly redistributed on the
* understanding that the author is not responsible for the correct
* functioning of this software in any circumstances and is not liable for
* any damages caused by this software.
*
* October 1992
*/
/*
* kernel include files.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/namei.h>
#include <sys/mount.h> /* to define statfs structure */
#include <sys/vnode.h> /* to define vattr structure */
#include <sys/errno.h>
#include <sys/dirent.h>
/*
* msdosfs include files.
*/
#include <msdosfs/bpb.h>
#include <msdosfs/msdosfsmount.h>
#include <msdosfs/direntry.h>
#include <msdosfs/denode.h>
#include <msdosfs/fat.h>
/*
* Fat cache stats.
*/
int fc_fileextends; /* # of file extends */
int fc_lfcempty; /* # of time last file cluster cache entry
* was empty */
int fc_bmapcalls; /* # of times pcbmap was called */
#define LMMAX 20
int fc_lmdistance[LMMAX]; /* counters for how far off the last
* cluster mapped entry was. */
int fc_largedistance; /* off by more than LMMAX */
static void fatblock(struct msdosfsmount *, uint32_t, uint32_t *, uint32_t *,
uint32_t *);
void updatefats(struct msdosfsmount *, struct buf *, uint32_t);
static __inline void usemap_free(struct msdosfsmount *, uint32_t);
static __inline void usemap_alloc(struct msdosfsmount *, uint32_t);
static int fatchain(struct msdosfsmount *, uint32_t, uint32_t, uint32_t);
int chainlength(struct msdosfsmount *, uint32_t, uint32_t);
int chainalloc(struct msdosfsmount *, uint32_t, uint32_t, uint32_t, uint32_t *,
uint32_t *);
static void
fatblock(pmp, ofs, bnp, sizep, bop)
struct msdosfsmount *pmp;
uint32_t ofs;
uint32_t *bnp;
uint32_t *sizep;
uint32_t *bop;
{
uint32_t bn, size;
bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) * DEV_BSIZE;
bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
if (bnp)
*bnp = bn;
if (sizep)
*sizep = size;
if (bop)
*bop = ofs % pmp->pm_fatblocksize;
}
/*
* Map the logical cluster number of a file into a physical disk sector
* that is filesystem relative.
*
* dep - address of denode representing the file of interest
* findcn - file relative cluster whose filesystem relative cluster number
* and/or block number are/is to be found
* bnp - address of where to place the file system relative block number.
* If this pointer is null then don't return this quantity.
* cnp - address of where to place the file system relative cluster number.
* If this pointer is null then don't return this quantity.
*
* NOTE: Either bnp or cnp must be non-null.
* This function has one side effect. If the requested file relative cluster
* is beyond the end of file, then the actual number of clusters in the file
* is returned in *cnp. This is useful for determining how long a directory is.
* If cnp is null, nothing is returned.
*/
int
pcbmap(dep, findcn, bnp, cnp, sp)
struct denode *dep;
uint32_t findcn; /* file relative cluster to get */
daddr64_t *bnp; /* returned filesys relative blk number */
uint32_t *cnp; /* returned cluster number */
int *sp; /* returned block size */
{
int error;
uint32_t i;
uint32_t cn;
uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */
uint32_t byteoffset;
uint32_t bn;
uint32_t bo;
struct buf *bp = NULL;
uint32_t bp_bn = -1;
struct msdosfsmount *pmp = dep->de_pmp;
uint32_t bsize;
fc_bmapcalls++;
/*
* If they don't give us someplace to return a value then don't
* bother doing anything.
*/
if (bnp == NULL && cnp == NULL && sp == NULL)
return (0);
cn = dep->de_StartCluster;
/*
* The "file" that makes up the root directory is contiguous,
* permanently allocated, of fixed size, and is not made up of
* clusters. If the cluster number is beyond the end of the root
* directory, then return the number of clusters in the file.
*/
if (cn == MSDOSFSROOT) {
if (dep->de_Attributes & ATTR_DIRECTORY) {
if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
if (cnp)
*cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
return (E2BIG);
}
if (bnp)
*bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
if (cnp)
*cnp = MSDOSFSROOT;
if (sp)
*sp = min(pmp->pm_bpcluster,
dep->de_FileSize - de_cn2off(pmp, findcn));
return (0);
} else { /* just an empty file */
if (cnp)
*cnp = 0;
return (E2BIG);
}
}
/*
* All other files do I/O in cluster sized blocks
*/
if (sp)
*sp = pmp->pm_bpcluster;
/*
* Rummage around in the fat cache, maybe we can avoid tromping
* thru every fat entry for the file. And, keep track of how far
* off the cache was from where we wanted to be.
*/
i = 0;
fc_lookup(dep, findcn, &i, &cn);
if ((bn = findcn - i) >= LMMAX)
fc_largedistance++;
else
fc_lmdistance[bn]++;
/*
* Handle all other files or directories the normal way.
*/
for (; i < findcn; i++) {
/*
* Stop with all reserved clusters, not just with EOF.
*/
if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
goto hiteof;
byteoffset = FATOFS(pmp, cn);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
if (bn != bp_bn) {
if (bp)
brelse(bp);
error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
bp_bn = bn;
}
prevcn = cn;
if (bo >= bsize) {
if (bp)
brelse(bp);
return (EIO);
}
if (FAT32(pmp))
cn = getulong(&bp->b_data[bo]);
else
cn = getushort(&bp->b_data[bo]);
if (FAT12(pmp) && (prevcn & 1))
cn >>= 4;
cn &= pmp->pm_fatmask;
/*
* Force the special cluster numbers
* to be the same for all cluster sizes
* to let the rest of msdosfs handle
* all cases the same.
*/
if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
cn |= ~pmp->pm_fatmask;
}
if (!MSDOSFSEOF(pmp, cn)) {
if (bp)
brelse(bp);
if (bnp)
*bnp = cntobn(pmp, cn);
if (cnp)
*cnp = cn;
fc_setcache(dep, FC_LASTMAP, i, cn);
return (0);
}
hiteof:;
if (cnp)
*cnp = i;
if (bp)
brelse(bp);
/* update last file cluster entry in the fat cache */
fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
return (E2BIG);
}
/*
* Find the closest entry in the fat cache to the cluster we are looking
* for.
*/
void
fc_lookup(dep, findcn, frcnp, fsrcnp)
struct denode *dep;
uint32_t findcn;
uint32_t *frcnp;
uint32_t *fsrcnp;
{
int i;
uint32_t cn;
struct fatcache *closest = 0;
for (i = 0; i < FC_SIZE; i++) {
cn = dep->de_fc[i].fc_frcn;
if (cn != FCE_EMPTY && cn <= findcn) {
if (closest == 0 || cn > closest->fc_frcn)
closest = &dep->de_fc[i];
}
}
if (closest) {
*frcnp = closest->fc_frcn;
*fsrcnp = closest->fc_fsrcn;
}
}
/*
* Purge the fat cache in denode dep of all entries relating to file
* relative cluster frcn and beyond.
*/
void
fc_purge(dep, frcn)
struct denode *dep;
u_int frcn;
{
int i;
struct fatcache *fcp;
fcp = dep->de_fc;
for (i = 0; i < FC_SIZE; i++, fcp++) {
if (fcp->fc_frcn >= frcn)
fcp->fc_frcn = FCE_EMPTY;
}
}
/*
* Update the fat.
* If mirroring the fat, update all copies, with the first copy as last.
* Else update only the current fat (ignoring the others).
*
* pmp - msdosfsmount structure for filesystem to update
* bp - addr of modified fat block
* fatbn - block number relative to begin of filesystem of the modified fat block.
*/
void
updatefats(pmp, bp, fatbn)
struct msdosfsmount *pmp;
struct buf *bp;
uint32_t fatbn;
{
int i;
struct buf *bpn;
#ifdef MSDOSFS_DEBUG
printf("updatefats(pmp %08, buf %x, fatbn %ld)\n", pmp, bp, fatbn);
#endif
/*
* If we have an FSInfo block, update it.
*/
if (pmp->pm_fsinfo) {
uint32_t cn = pmp->pm_nxtfree;
if (pmp->pm_freeclustercount
&& (pmp->pm_inusemap[cn / N_INUSEBITS]
& (1 << (cn % N_INUSEBITS)))) {
/*
* The cluster indicated in FSInfo isn't free
* any longer. Got get a new free one.
*/
for (cn = 0; cn < pmp->pm_maxcluster; cn++)
if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
break;
pmp->pm_nxtfree = cn
+ ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
^ (u_int)-1) - 1;
}
if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), NOCRED,
&bpn) != 0) {
/*
* Ignore the error, but turn off FSInfo update for the future.
*/
pmp->pm_fsinfo = 0;
brelse(bpn);
} else {
struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
putulong(fp->fsinfree, pmp->pm_freeclustercount);
putulong(fp->fsinxtfree, pmp->pm_nxtfree);
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bpn);
else
bdwrite(bpn);
}
}
if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
/*
* Now copy the block(s) of the modified fat to the other copies of
* the fat and write them out. This is faster than reading in the
* other fats and then writing them back out. This could tie up
* the fat for quite a while. Preventing others from accessing it.
* To prevent us from going after the fat quite so much we use
* delayed writes, unless they specfied "synchronous" when the
* filesystem was mounted. If synch is asked for then use
* bwrite()'s and really slow things down.
*/
for (i = 1; i < pmp->pm_FATs; i++) {
fatbn += pmp->pm_FATsecs;
/* getblk() never fails */
bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0);
bcopy(bp->b_data, bpn->b_data, bp->b_bcount);
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bpn);
else
bdwrite(bpn);
}
}
/*
* Write out the first (or current) fat last.
*/
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bp);
else
bdwrite(bp);
/*
* Maybe update fsinfo sector here?
*/
}
/*
* Updating entries in 12 bit fats is a pain in the butt.
*
* The following picture shows where nibbles go when moving from a 12 bit
* cluster number into the appropriate bytes in the FAT.
*
* byte m byte m+1 byte m+2
* +----+----+ +----+----+ +----+----+
* | 0 1 | | 2 3 | | 4 5 | FAT bytes
* +----+----+ +----+----+ +----+----+
*
* +----+----+----+ +----+----+----+
* | 3 0 1 | | 4 5 2 |
* +----+----+----+ +----+----+----+
* cluster n cluster n+1
*
* Where n is even. m = n + (n >> 2)
*
*/
static __inline void
usemap_alloc(pmp, cn)
struct msdosfsmount *pmp;
uint32_t cn;
{
pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
pmp->pm_freeclustercount--;
}
static __inline void
usemap_free(pmp, cn)
struct msdosfsmount *pmp;
uint32_t cn;
{
pmp->pm_freeclustercount++;
pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
}
int
clusterfree(pmp, cluster, oldcnp)
struct msdosfsmount *pmp;
uint32_t cluster;
uint32_t *oldcnp;
{
int error;
uint32_t oldcn;
usemap_free(pmp, cluster);
error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
if (error) {
usemap_alloc(pmp, cluster);
return (error);
}
/*
* If the cluster was successfully marked free, then update
* the count of free clusters, and turn off the "allocated"
* bit in the "in use" cluster bit map.
*/
if (oldcnp)
*oldcnp = oldcn;
return (0);
}
/*
* Get or Set or 'Get and Set' the cluster'th entry in the fat.
*
* function - whether to get or set a fat entry
* pmp - address of the msdosfsmount structure for the filesystem
* whose fat is to be manipulated.
* cn - which cluster is of interest
* oldcontents - address of a word that is to receive the contents of the
* cluster'th entry if this is a get function
* newcontents - the new value to be written into the cluster'th element of
* the fat if this is a set function.
*
* This function can also be used to free a cluster by setting the fat entry
* for a cluster to 0.
*
* All copies of the fat are updated if this is a set function. NOTE: If
* fatentry() marks a cluster as free it does not update the inusemap in
* the msdosfsmount structure. This is left to the caller.
*/
int
fatentry(function, pmp, cn, oldcontents, newcontents)
int function;
struct msdosfsmount *pmp;
uint32_t cn;
uint32_t *oldcontents;
uint32_t newcontents;
{
int error;
uint32_t readcn;
uint32_t bn, bo, bsize, byteoffset;
struct buf *bp;
#ifdef MSDOSFS_DEBUG
printf("fatentry(func %d, pmp %08x, clust %d, oldcon %08x, newcon %d)\n",
function, pmp, cn, oldcontents, newcontents);
#endif
#ifdef DIAGNOSTIC
/*
* Be sure they asked us to do something.
*/
if ((function & (FAT_SET | FAT_GET)) == 0) {
printf("fatentry(): function code doesn't specify get or set\n");
return (EINVAL);
}
/*
* If they asked us to return a cluster number but didn't tell us
* where to put it, give them an error.
*/
if ((function & FAT_GET) && oldcontents == NULL) {
printf("fatentry(): get function with no place to put result\n");
return (EINVAL);
}
#endif
/*
* Be sure the requested cluster is in the filesystem.
*/
if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
return (EINVAL);
byteoffset = FATOFS(pmp, cn);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
if ((error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp)) != 0) {
brelse(bp);
return (error);
}
if (function & FAT_GET) {
if (FAT32(pmp))
readcn = getulong(&bp->b_data[bo]);
else
readcn = getushort(&bp->b_data[bo]);
if (FAT12(pmp) && (cn & 1))
readcn >>= 4;
readcn &= pmp->pm_fatmask;
/* map reserved fat entries to same values for all fats */
if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
readcn |= ~pmp->pm_fatmask;
*oldcontents = readcn;
}
if (function & FAT_SET) {
switch (pmp->pm_fatmask) {
case FAT12_MASK:
readcn = getushort(&bp->b_data[bo]);
if (cn & 1) {
readcn &= 0x000f;
readcn |= newcontents << 4;
} else {
readcn &= 0xf000;
readcn |= newcontents & 0xfff;
}
putushort(&bp->b_data[bo], readcn);
break;
case FAT16_MASK:
putushort(&bp->b_data[bo], newcontents);
break;
case FAT32_MASK:
/*
* According to spec we have to retain the
* high order bits of the fat entry.
*/
readcn = getulong(&bp->b_data[bo]);
readcn &= ~FAT32_MASK;
readcn |= newcontents & FAT32_MASK;
putulong(&bp->b_data[bo], readcn);
break;
}
updatefats(pmp, bp, bn);
bp = NULL;
pmp->pm_fmod = 1;
}
if (bp)
brelse(bp);
return (0);
}
/*
* Update a contiguous cluster chain
*
* pmp - mount point
* start - first cluster of chain
* count - number of clusters in chain
* fillwith - what to write into fat entry of last cluster
*/
static int
fatchain(pmp, start, count, fillwith)
struct msdosfsmount *pmp;
uint32_t start;
uint32_t count;
uint32_t fillwith;
{
int error;
uint32_t bn, bo, bsize, byteoffset, readcn, newc;
struct buf *bp;
#ifdef MSDOSFS_DEBUG
printf("fatchain(pmp %08x, start %d, count %d, fillwith %d)\n",
pmp, start, count, fillwith);
#endif
/*
* Be sure the clusters are in the filesystem.
*/
if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
return (EINVAL);
while (count > 0) {
byteoffset = FATOFS(pmp, start);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
while (count > 0) {
start++;
newc = --count > 0 ? start : fillwith;
switch (pmp->pm_fatmask) {
case FAT12_MASK:
readcn = getushort(&bp->b_data[bo]);
if (start & 1) {
readcn &= 0xf000;
readcn |= newc & 0xfff;
} else {
readcn &= 0x000f;
readcn |= newc << 4;
}
putushort(&bp->b_data[bo], readcn);
bo++;
if (!(start & 1))
bo++;
break;
case FAT16_MASK:
putushort(&bp->b_data[bo], newc);
bo += 2;
break;
case FAT32_MASK:
readcn = getulong(&bp->b_data[bo]);
readcn &= ~pmp->pm_fatmask;
readcn |= newc & pmp->pm_fatmask;
putulong(&bp->b_data[bo], readcn);
bo += 4;
break;
}
if (bo >= bsize)
break;
}
updatefats(pmp, bp, bn);
}
pmp->pm_fmod = 1;
return (0);
}
/*
* Check the length of a free cluster chain starting at start.
*
* pmp - mount point
* start - start of chain
* count - maximum interesting length
*/
int
chainlength(pmp, start, count)
struct msdosfsmount *pmp;
uint32_t start;
uint32_t count;
{
uint32_t idx, max_idx;
u_int map;
uint32_t len;
max_idx = pmp->pm_maxcluster / N_INUSEBITS;
idx = start / N_INUSEBITS;
start %= N_INUSEBITS;
map = pmp->pm_inusemap[idx];
map &= ~((1 << start) - 1);
if (map) {
len = ffs(map) - 1 - start;
return (len > count ? count : len);
}
len = N_INUSEBITS - start;
if (len >= count)
return (count);
while (++idx <= max_idx) {
if (len >= count)
break;
if ((map = pmp->pm_inusemap[idx]) != 0) {
len += ffs(map) - 1;
break;
}
len += N_INUSEBITS;
}
return (len > count ? count : len);
}
/*
* Allocate contigous free clusters.
*
* pmp - mount point.
* start - start of cluster chain.
* count - number of clusters to allocate.
* fillwith - put this value into the fat entry for the
* last allocated cluster.
* retcluster - put the first allocated cluster's number here.
* got - how many clusters were actually allocated.
*/
int
chainalloc(pmp, start, count, fillwith, retcluster, got)
struct msdosfsmount *pmp;
uint32_t start;
uint32_t count;
uint32_t fillwith;
uint32_t *retcluster;
uint32_t *got;
{
int error;
uint32_t cl, n;
for (cl = start, n = count; n-- > 0;)
usemap_alloc(pmp, cl++);
if ((error = fatchain(pmp, start, count, fillwith)) != 0)
return (error);
#ifdef MSDOSFS_DEBUG
printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n",
start, count);
#endif
if (retcluster)
*retcluster = start;
if (got)
*got = count;
return (0);
}
/*
* Allocate contiguous free clusters.
*
* pmp - mount point.
* start - preferred start of cluster chain.
* count - number of clusters requested.
* fillwith - put this value into the fat entry for the
* last allocated cluster.
* retcluster - put the first allocated cluster's number here.
* got - how many clusters were actually allocated.
*/
int
clusteralloc(pmp, start, count, fillwith, retcluster, got)
struct msdosfsmount *pmp;
uint32_t start;
uint32_t count;
uint32_t fillwith;
uint32_t *retcluster;
uint32_t *got;
{
uint32_t idx;
uint32_t len, newst, foundl, cn, l;
uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */
u_int map;
#ifdef MSDOSFS_DEBUG
printf("clusteralloc(): find %d clusters\n",count);
#endif
if (start) {
if ((len = chainlength(pmp, start, count)) >= count)
return (chainalloc(pmp, start, count, fillwith, retcluster, got));
} else {
/*
* This is a new file, initialize start
*/
struct timeval tv;
microtime(&tv);
start = (tv.tv_usec >> 10) | tv.tv_usec;
len = 0;
}
/*
* Start at a (pseudo) random place to maximize cluster runs
* under multiple writers.
*/
newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
foundl = 0;
for (cn = newst; cn <= pmp->pm_maxcluster;) {
idx = cn / N_INUSEBITS;
map = pmp->pm_inusemap[idx];
map |= (1 << (cn % N_INUSEBITS)) - 1;
if (map != (u_int)-1) {
cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
if ((l = chainlength(pmp, cn, count)) >= count)
return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
if (l > foundl) {
foundcn = cn;
foundl = l;
}
cn += l + 1;
continue;
}
cn += N_INUSEBITS - cn % N_INUSEBITS;
}
for (cn = 0; cn < newst;) {
idx = cn / N_INUSEBITS;
map = pmp->pm_inusemap[idx];
map |= (1 << (cn % N_INUSEBITS)) - 1;
if (map != (u_int)-1) {
cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
if ((l = chainlength(pmp, cn, count)) >= count)
return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
if (l > foundl) {
foundcn = cn;
foundl = l;
}
cn += l + 1;
continue;
}
cn += N_INUSEBITS - cn % N_INUSEBITS;
}
if (!foundl)
return (ENOSPC);
if (len)
return (chainalloc(pmp, start, len, fillwith, retcluster, got));
else
return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
}
/*
* Free a chain of clusters.
*
* pmp - address of the msdosfs mount structure for the filesystem
* containing the cluster chain to be freed.
* startcluster - number of the 1st cluster in the chain of clusters to be
* freed.
*/
int
freeclusterchain(pmp, cluster)
struct msdosfsmount *pmp;
uint32_t cluster;
{
int error;
struct buf *bp = NULL;
uint32_t bn, bo, bsize, byteoffset;
uint32_t readcn, lbn = -1;
while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
byteoffset = FATOFS(pmp, cluster);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
if (lbn != bn) {
if (bp)
updatefats(pmp, bp, lbn);
error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
lbn = bn;
}
usemap_free(pmp, cluster);
switch (pmp->pm_fatmask) {
case FAT12_MASK:
readcn = getushort(&bp->b_data[bo]);
if (cluster & 1) {
cluster = readcn >> 4;
readcn &= 0x000f;
readcn |= MSDOSFSFREE << 4;
} else {
cluster = readcn;
readcn &= 0xf000;
readcn |= MSDOSFSFREE & 0xfff;
}
putushort(&bp->b_data[bo], readcn);
break;
case FAT16_MASK:
cluster = getushort(&bp->b_data[bo]);
putushort(&bp->b_data[bo], MSDOSFSFREE);
break;
case FAT32_MASK:
cluster = getulong(&bp->b_data[bo]);
putulong(&bp->b_data[bo],
(MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
break;
}
cluster &= pmp->pm_fatmask;
if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
cluster |= pmp->pm_fatmask;
}
if (bp)
updatefats(pmp, bp, bn);
return (0);
}
/*
* Read in fat blocks looking for free clusters. For every free cluster
* found turn off its corresponding bit in the pm_inusemap.
*/
int
fillinusemap(pmp)
struct msdosfsmount *pmp;
{
struct buf *bp = NULL;
uint32_t cn, readcn;
int error;
uint32_t bn, bo, bsize, byteoffset;
/*
* Mark all clusters in use, we mark the free ones in the fat scan
* loop further down.
*/
for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
pmp->pm_inusemap[cn] = (u_int)-1;
/*
* Figure how many free clusters are in the filesystem by ripping
* through the fat counting the number of entries whose content is
* zero. These represent free clusters.
*/
pmp->pm_freeclustercount = 0;
for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
byteoffset = FATOFS(pmp, cn);
bo = byteoffset % pmp->pm_fatblocksize;
if (!bo || !bp) {
/* Read new FAT block */
if (bp)
brelse(bp);
fatblock(pmp, byteoffset, &bn, &bsize, NULL);
error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
}
if (FAT32(pmp))
readcn = getulong(&bp->b_data[bo]);
else
readcn = getushort(&bp->b_data[bo]);
if (FAT12(pmp) && (cn & 1))
readcn >>= 4;
readcn &= pmp->pm_fatmask;
if (readcn == 0)
usemap_free(pmp, cn);
}
brelse(bp);
return (0);
}
/*
* Allocate a new cluster and chain it onto the end of the file.
*
* dep - the file to extend
* count - number of clusters to allocate
* bpp - where to return the address of the buf header for the first new
* file block
* ncp - where to put cluster number of the first newly allocated cluster
* If this pointer is 0, do not return the cluster number.
* flags - see fat.h
*
* NOTE: This function is not responsible for turning on the DE_UPDATE bit of
* the de_flag field of the denode and it does not change the de_FileSize
* field. This is left for the caller to do.
*/
int
extendfile(dep, count, bpp, ncp, flags)
struct denode *dep;
uint32_t count;
struct buf **bpp;
uint32_t *ncp;
int flags;
{
int error;
uint32_t frcn;
uint32_t cn, got;
struct msdosfsmount *pmp = dep->de_pmp;
struct buf *bp;