1 /* $NetBSD: msdosfs_fat.c,v 1.19 2010/01/26 20:25:52 joerg 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 #include <sys/cdefs.h> 51 __KERNEL_RCSID(0, "$NetBSD: msdosfs_fat.c,v 1.19 2010/01/26 20:25:52 joerg Exp $"); 52 53 /* 54 * kernel include files. 55 */ 56 #include <sys/param.h> 57 #include <sys/systm.h> 58 #include <sys/buf.h> 59 #include <sys/file.h> 60 #include <sys/namei.h> 61 #include <sys/mount.h> /* to define statvfs structure */ 62 #include <sys/vnode.h> /* to define vattr structure */ 63 #include <sys/errno.h> 64 #include <sys/dirent.h> 65 #include <sys/kauth.h> 66 67 /* 68 * msdosfs include files. 69 */ 70 #include <fs/msdosfs/bpb.h> 71 #include <fs/msdosfs/msdosfsmount.h> 72 #include <fs/msdosfs/direntry.h> 73 #include <fs/msdosfs/denode.h> 74 #include <fs/msdosfs/fat.h> 75 76 /* 77 * Fat cache stats. 78 */ 79 int fc_fileextends; /* # of file extends */ 80 int fc_lfcempty; /* # of time last file cluster cache entry 81 * was empty */ 82 int fc_bmapcalls; /* # of times pcbmap was called */ 83 84 #define LMMAX 20 85 int fc_lmdistance[LMMAX]; /* counters for how far off the last 86 * cluster mapped entry was. */ 87 int fc_largedistance; /* off by more than LMMAX */ 88 int fc_wherefrom, fc_whereto, fc_lastclust; 89 int pm_fatblocksize; 90 91 #ifdef MSDOSFS_DEBUG 92 void print_fat_stats(void); 93 94 void 95 print_fat_stats(void) 96 { 97 int i; 98 99 printf("fc_fileextends=%d fc_lfcempty=%d fc_bmapcalls=%d " 100 "fc_largedistance=%d [%d->%d=%d] fc_lastclust=%d pm_fatblocksize=%d\n", 101 fc_fileextends, fc_lfcempty, fc_bmapcalls, fc_largedistance, 102 fc_wherefrom, fc_whereto, fc_whereto-fc_wherefrom, 103 fc_lastclust, pm_fatblocksize); 104 105 fc_fileextends = fc_lfcempty = fc_bmapcalls = 0; 106 fc_wherefrom = fc_whereto = fc_lastclust = 0; 107 108 for (i = 0; i < LMMAX; i++) { 109 printf("%d:%d ", i, fc_lmdistance[i]); 110 fc_lmdistance[i] = 0; 111 } 112 113 printf("\n"); 114 } 115 #endif 116 117 static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *, 118 u_long *); 119 void updatefats(struct msdosfsmount *, struct buf *, u_long); 120 static inline void usemap_free(struct msdosfsmount *, u_long); 121 static inline void usemap_alloc(struct msdosfsmount *, u_long); 122 static int fatchain(struct msdosfsmount *, u_long, u_long, u_long); 123 int chainlength(struct msdosfsmount *, u_long, u_long); 124 int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *, 125 u_long *); 126 127 static void 128 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, u_long *bop) 129 { 130 u_long bn, size; 131 132 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 133 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 134 * pmp->pm_BytesPerSec; 135 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 136 137 if (bnp) 138 *bnp = bn; 139 if (sizep) 140 *sizep = size; 141 if (bop) 142 *bop = ofs % pmp->pm_fatblocksize; 143 144 pm_fatblocksize = pmp->pm_fatblocksize; 145 } 146 147 /* 148 * Map the logical cluster number of a file into a physical disk sector 149 * that is filesystem relative. 150 * 151 * dep - address of denode representing the file of interest 152 * findcn - file relative cluster whose filesystem relative cluster number 153 * and/or block number are/is to be found 154 * bnp - address of where to place the file system relative block number. 155 * If this pointer is null then don't return this quantity. 156 * cnp - address of where to place the file system relative cluster number. 157 * If this pointer is null then don't return this quantity. 158 * 159 * NOTE: Either bnp or cnp must be non-null. 160 * This function has one side effect. If the requested file relative cluster 161 * is beyond the end of file, then the actual number of clusters in the file 162 * is returned in *cnp. This is useful for determining how long a directory is. 163 * If cnp is null, nothing is returned. 164 */ 165 int 166 pcbmap(struct denode *dep, u_long findcn, daddr_t *bnp, u_long *cnp, int *sp) 167 /* findcn: file relative cluster to get */ 168 /* bnp: returned filesys rel sector number */ 169 /* cnp: returned cluster number */ 170 /* sp: returned block size */ 171 { 172 int error; 173 u_long i; 174 u_long cn; 175 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 176 u_long byteoffset; 177 u_long bn; 178 u_long bo; 179 struct buf *bp = NULL; 180 u_long bp_bn = -1; 181 struct msdosfsmount *pmp = dep->de_pmp; 182 u_long bsize; 183 184 fc_bmapcalls++; 185 186 /* 187 * If they don't give us someplace to return a value then don't 188 * bother doing anything. 189 */ 190 if (bnp == NULL && cnp == NULL && sp == NULL) 191 return (0); 192 193 cn = dep->de_StartCluster; 194 /* 195 * The "file" that makes up the root directory is contiguous, 196 * permanently allocated, of fixed size, and is not made up of 197 * clusters. If the cluster number is beyond the end of the root 198 * directory, then return the number of clusters in the file. 199 */ 200 if (cn == MSDOSFSROOT) { 201 if (dep->de_Attributes & ATTR_DIRECTORY) { 202 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 203 if (cnp) 204 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 205 return (E2BIG); 206 } 207 if (bnp) 208 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 209 if (cnp) 210 *cnp = MSDOSFSROOT; 211 if (sp) 212 *sp = min(pmp->pm_bpcluster, 213 dep->de_FileSize - de_cn2off(pmp, findcn)); 214 return (0); 215 } else { /* just an empty file */ 216 if (cnp) 217 *cnp = 0; 218 return (E2BIG); 219 } 220 } 221 222 /* 223 * All other files do I/O in cluster sized blocks 224 */ 225 if (sp) 226 *sp = pmp->pm_bpcluster; 227 228 /* 229 * Rummage around in the fat cache, maybe we can avoid tromping 230 * thru every fat entry for the file. And, keep track of how far 231 * off the cache was from where we wanted to be. 232 */ 233 i = 0; 234 fc_lookup(dep, findcn, &i, &cn); 235 if ((bn = findcn - i) >= LMMAX) { 236 fc_largedistance++; 237 fc_wherefrom = i; 238 fc_whereto = findcn; 239 fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn; 240 } else 241 fc_lmdistance[bn]++; 242 243 /* 244 * Handle all other files or directories the normal way. 245 */ 246 for (; i < findcn; i++) { 247 /* 248 * Stop with all reserved clusters, not just with EOF. 249 */ 250 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask)) 251 goto hiteof; 252 byteoffset = FATOFS(pmp, cn); 253 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 254 if (bn != bp_bn) { 255 if (bp) 256 brelse(bp, 0); 257 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 258 NOCRED, 0, &bp); 259 if (error) { 260 brelse(bp, 0); 261 return (error); 262 } 263 bp_bn = bn; 264 } 265 prevcn = cn; 266 if (bo >= bsize) { 267 if (bp) 268 brelse(bp, 0); 269 return (EIO); 270 } 271 KASSERT(bp != NULL); 272 if (FAT32(pmp)) 273 cn = getulong((char *)bp->b_data + bo); 274 else 275 cn = getushort((char *)bp->b_data + bo); 276 if (FAT12(pmp) && (prevcn & 1)) 277 cn >>= 4; 278 cn &= pmp->pm_fatmask; 279 } 280 281 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) { 282 if (bp) 283 brelse(bp, 0); 284 if (bnp) 285 *bnp = cntobn(pmp, cn); 286 if (cnp) 287 *cnp = cn; 288 fc_setcache(dep, FC_LASTMAP, i, cn); 289 return (0); 290 } 291 292 hiteof:; 293 if (cnp) 294 *cnp = i; 295 if (bp) 296 brelse(bp, 0); 297 /* update last file cluster entry in the fat cache */ 298 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 299 return (E2BIG); 300 } 301 302 /* 303 * Find the closest entry in the fat cache to the cluster we are looking 304 * for. 305 */ 306 void 307 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp) 308 { 309 int i; 310 u_long cn; 311 struct fatcache *closest = 0; 312 313 for (i = 0; i < FC_SIZE; i++) { 314 cn = dep->de_fc[i].fc_frcn; 315 if (cn != FCE_EMPTY && cn <= findcn) { 316 if (closest == 0 || cn > closest->fc_frcn) 317 closest = &dep->de_fc[i]; 318 } 319 } 320 if (closest) { 321 *frcnp = closest->fc_frcn; 322 *fsrcnp = closest->fc_fsrcn; 323 } 324 } 325 326 /* 327 * Purge the fat cache in denode dep of all entries relating to file 328 * relative cluster frcn and beyond. 329 */ 330 void 331 fc_purge(struct denode *dep, u_int frcn) 332 { 333 int i; 334 struct fatcache *fcp; 335 336 fcp = dep->de_fc; 337 for (i = 0; i < FC_SIZE; i++, fcp++) { 338 if (fcp->fc_frcn >= frcn) 339 fcp->fc_frcn = FCE_EMPTY; 340 } 341 } 342 343 /* 344 * Update the fat. 345 * If mirroring the fat, update all copies, with the first copy as last. 346 * Else update only the current fat (ignoring the others). 347 * 348 * pmp - msdosfsmount structure for filesystem to update 349 * bp - addr of modified fat block 350 * fatbn - block number relative to begin of filesystem of the modified fat block. 351 */ 352 void 353 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 354 { 355 int i; 356 struct buf *bpn; 357 358 #ifdef MSDOSFS_DEBUG 359 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", 360 pmp, bp, fatbn); 361 #endif 362 363 /* 364 * If we have an FSInfo block, update it. 365 */ 366 if (pmp->pm_fsinfo) { 367 u_long cn = pmp->pm_nxtfree; 368 369 if (pmp->pm_freeclustercount 370 && (pmp->pm_inusemap[cn / N_INUSEBITS] 371 & (1 << (cn % N_INUSEBITS)))) { 372 /* 373 * The cluster indicated in FSInfo isn't free 374 * any longer. Got get a new free one. 375 */ 376 for (cn = 0; cn < pmp->pm_maxcluster; cn++) 377 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 378 break; 379 pmp->pm_nxtfree = cn 380 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 381 ^ (u_int)-1) - 1; 382 } 383 /* 384 * XXX If the fsinfo block is stored on media with 385 * 2KB or larger sectors, is the fsinfo structure 386 * padded at the end or in the middle? 387 */ 388 if (bread(pmp->pm_devvp, de_bn2kb(pmp, pmp->pm_fsinfo), 389 pmp->pm_BytesPerSec, NOCRED, B_MODIFY, &bpn) != 0) { 390 /* 391 * Ignore the error, but turn off FSInfo update for the future. 392 */ 393 pmp->pm_fsinfo = 0; 394 brelse(bpn, 0); 395 } else { 396 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 397 398 putulong(fp->fsinfree, pmp->pm_freeclustercount); 399 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 400 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 401 bwrite(bpn); 402 else 403 bdwrite(bpn); 404 } 405 } 406 407 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 408 /* 409 * Now copy the block(s) of the modified fat to the other copies of 410 * the fat and write them out. This is faster than reading in the 411 * other fats and then writing them back out. This could tie up 412 * the fat for quite a while. Preventing others from accessing it. 413 * To prevent us from going after the fat quite so much we use 414 * delayed writes, unless they specified "synchronous" when the 415 * filesystem was mounted. If synch is asked for then use 416 * bwrite()'s and really slow things down. 417 */ 418 for (i = 1; i < pmp->pm_FATs; i++) { 419 fatbn += pmp->pm_FATsecs; 420 /* getblk() never fails */ 421 bpn = getblk(pmp->pm_devvp, de_bn2kb(pmp, fatbn), 422 bp->b_bcount, 0, 0); 423 memcpy(bpn->b_data, bp->b_data, bp->b_bcount); 424 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 425 bwrite(bpn); 426 else 427 bdwrite(bpn); 428 } 429 } 430 431 /* 432 * Write out the first (or current) fat last. 433 */ 434 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 435 bwrite(bp); 436 else 437 bdwrite(bp); 438 /* 439 * Maybe update fsinfo sector here? 440 */ 441 } 442 443 /* 444 * Updating entries in 12 bit fats is a pain in the butt. 445 * 446 * The following picture shows where nibbles go when moving from a 12 bit 447 * cluster number into the appropriate bytes in the FAT. 448 * 449 * byte m byte m+1 byte m+2 450 * +----+----+ +----+----+ +----+----+ 451 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 452 * +----+----+ +----+----+ +----+----+ 453 * 454 * +----+----+----+ +----+----+----+ 455 * | 3 0 1 | | 4 5 2 | 456 * +----+----+----+ +----+----+----+ 457 * cluster n cluster n+1 458 * 459 * Where n is even. m = n + (n >> 2) 460 * 461 */ 462 static inline void 463 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 464 { 465 466 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 467 pmp->pm_freeclustercount--; 468 } 469 470 static inline void 471 usemap_free(struct msdosfsmount *pmp, u_long cn) 472 { 473 474 pmp->pm_freeclustercount++; 475 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 476 } 477 478 int 479 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 480 { 481 int error; 482 u_long oldcn; 483 484 usemap_free(pmp, cluster); 485 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 486 if (error) { 487 usemap_alloc(pmp, cluster); 488 return (error); 489 } 490 /* 491 * If the cluster was successfully marked free, then update 492 * the count of free clusters, and turn off the "allocated" 493 * bit in the "in use" cluster bit map. 494 */ 495 if (oldcnp) 496 *oldcnp = oldcn; 497 return (0); 498 } 499 500 /* 501 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 502 * 503 * function - whether to get or set a fat entry 504 * pmp - address of the msdosfsmount structure for the filesystem 505 * whose fat is to be manipulated. 506 * cn - which cluster is of interest 507 * oldcontents - address of a word that is to receive the contents of the 508 * cluster'th entry if this is a get function 509 * newcontents - the new value to be written into the cluster'th element of 510 * the fat if this is a set function. 511 * 512 * This function can also be used to free a cluster by setting the fat entry 513 * for a cluster to 0. 514 * 515 * All copies of the fat are updated if this is a set function. NOTE: If 516 * fatentry() marks a cluster as free it does not update the inusemap in 517 * the msdosfsmount structure. This is left to the caller. 518 */ 519 int 520 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, u_long newcontents) 521 { 522 int error; 523 u_long readcn; 524 u_long bn, bo, bsize, byteoffset; 525 struct buf *bp; 526 527 #ifdef MSDOSFS_DEBUG 528 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 529 function, pmp, cn, oldcontents, newcontents); 530 #endif 531 532 #ifdef DIAGNOSTIC 533 /* 534 * Be sure they asked us to do something. 535 */ 536 if ((function & (FAT_SET | FAT_GET)) == 0) { 537 printf("fatentry(): function code doesn't specify get or set\n"); 538 return (EINVAL); 539 } 540 541 /* 542 * If they asked us to return a cluster number but didn't tell us 543 * where to put it, give them an error. 544 */ 545 if ((function & FAT_GET) && oldcontents == NULL) { 546 printf("fatentry(): get function with no place to put result\n"); 547 return (EINVAL); 548 } 549 #endif 550 551 /* 552 * Be sure the requested cluster is in the filesystem. 553 */ 554 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 555 return (EINVAL); 556 557 byteoffset = FATOFS(pmp, cn); 558 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 559 if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, NOCRED, 560 0, &bp)) != 0) { 561 brelse(bp, 0); 562 return (error); 563 } 564 565 if (function & FAT_GET) { 566 if (FAT32(pmp)) 567 readcn = getulong((char *)bp->b_data + bo); 568 else 569 readcn = getushort((char *)bp->b_data + bo); 570 if (FAT12(pmp) & (cn & 1)) 571 readcn >>= 4; 572 readcn &= pmp->pm_fatmask; 573 *oldcontents = readcn; 574 } 575 if (function & FAT_SET) { 576 switch (pmp->pm_fatmask) { 577 case FAT12_MASK: 578 readcn = getushort((char *)bp->b_data + bo); 579 if (cn & 1) { 580 readcn &= 0x000f; 581 readcn |= newcontents << 4; 582 } else { 583 readcn &= 0xf000; 584 readcn |= newcontents & 0xfff; 585 } 586 putushort((char *)bp->b_data + bo, readcn); 587 break; 588 case FAT16_MASK: 589 putushort((char *)bp->b_data + bo, newcontents); 590 break; 591 case FAT32_MASK: 592 /* 593 * According to spec we have to retain the 594 * high order bits of the fat entry. 595 */ 596 readcn = getulong((char *)bp->b_data + bo); 597 readcn &= ~FAT32_MASK; 598 readcn |= newcontents & FAT32_MASK; 599 putulong((char *)bp->b_data + bo, readcn); 600 break; 601 } 602 updatefats(pmp, bp, bn); 603 bp = NULL; 604 pmp->pm_fmod = 1; 605 } 606 if (bp) 607 brelse(bp, 0); 608 return (0); 609 } 610 611 /* 612 * Update a contiguous cluster chain 613 * 614 * pmp - mount point 615 * start - first cluster of chain 616 * count - number of clusters in chain 617 * fillwith - what to write into fat entry of last cluster 618 */ 619 static int 620 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 621 { 622 int error; 623 u_long bn, bo, bsize, byteoffset, readcn, newc; 624 struct buf *bp; 625 626 #ifdef MSDOSFS_DEBUG 627 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 628 pmp, start, count, fillwith); 629 #endif 630 /* 631 * Be sure the clusters are in the filesystem. 632 */ 633 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 634 return (EINVAL); 635 636 while (count > 0) { 637 byteoffset = FATOFS(pmp, start); 638 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 639 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, NOCRED, 640 B_MODIFY, &bp); 641 if (error) { 642 brelse(bp, 0); 643 return (error); 644 } 645 while (count > 0) { 646 start++; 647 newc = --count > 0 ? start : fillwith; 648 switch (pmp->pm_fatmask) { 649 case FAT12_MASK: 650 readcn = getushort((char *)bp->b_data + bo); 651 if (start & 1) { 652 readcn &= 0xf000; 653 readcn |= newc & 0xfff; 654 } else { 655 readcn &= 0x000f; 656 readcn |= newc << 4; 657 } 658 putushort((char *)bp->b_data + bo, readcn); 659 bo++; 660 if (!(start & 1)) 661 bo++; 662 break; 663 case FAT16_MASK: 664 putushort((char *)bp->b_data + bo, newc); 665 bo += 2; 666 break; 667 case FAT32_MASK: 668 readcn = getulong((char *)bp->b_data + bo); 669 readcn &= ~pmp->pm_fatmask; 670 readcn |= newc & pmp->pm_fatmask; 671 putulong((char *)bp->b_data + bo, readcn); 672 bo += 4; 673 break; 674 } 675 if (bo >= bsize) 676 break; 677 } 678 updatefats(pmp, bp, bn); 679 } 680 pmp->pm_fmod = 1; 681 return (0); 682 } 683 684 /* 685 * Check the length of a free cluster chain starting at start. 686 * 687 * pmp - mount point 688 * start - start of chain 689 * count - maximum interesting length 690 */ 691 int 692 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 693 { 694 u_long idx, max_idx; 695 u_int map; 696 u_long len; 697 698 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 699 idx = start / N_INUSEBITS; 700 start %= N_INUSEBITS; 701 map = pmp->pm_inusemap[idx]; 702 map &= ~((1 << start) - 1); 703 if (map) { 704 len = ffs(map) - 1 - start; 705 return (len > count ? count : len); 706 } 707 len = N_INUSEBITS - start; 708 if (len >= count) 709 return (count); 710 while (++idx <= max_idx) { 711 if (len >= count) 712 break; 713 if ((map = pmp->pm_inusemap[idx]) != 0) { 714 len += ffs(map) - 1; 715 break; 716 } 717 len += N_INUSEBITS; 718 } 719 return (len > count ? count : len); 720 } 721 722 /* 723 * Allocate contigous free clusters. 724 * 725 * pmp - mount point. 726 * start - start of cluster chain. 727 * count - number of clusters to allocate. 728 * fillwith - put this value into the fat entry for the 729 * last allocated cluster. 730 * retcluster - put the first allocated cluster's number here. 731 * got - how many clusters were actually allocated. 732 */ 733 int 734 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith, u_long *retcluster, u_long *got) 735 { 736 int error; 737 u_long cl, n; 738 739 for (cl = start, n = count; n-- > 0;) 740 usemap_alloc(pmp, cl++); 741 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 742 return (error); 743 #ifdef MSDOSFS_DEBUG 744 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 745 start, count); 746 #endif 747 if (retcluster) 748 *retcluster = start; 749 if (got) 750 *got = count; 751 return (0); 752 } 753 754 /* 755 * Allocate contiguous free clusters. 756 * 757 * pmp - mount point. 758 * start - preferred start of cluster chain. 759 * count - number of clusters requested. 760 * fillwith - put this value into the fat entry for the 761 * last allocated cluster. 762 * retcluster - put the first allocated cluster's number here. 763 * got - how many clusters were actually allocated. 764 */ 765 int 766 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long *retcluster, u_long *got) 767 { 768 u_long idx; 769 u_long len, newst, foundl, cn, l; 770 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 771 u_long fillwith = CLUST_EOFE; 772 u_int map; 773 774 #ifdef MSDOSFS_DEBUG 775 printf("clusteralloc(): find %lu clusters\n",count); 776 #endif 777 if (start) { 778 if ((len = chainlength(pmp, start, count)) >= count) 779 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 780 } else { 781 /* 782 * This is a new file, initialize start 783 */ 784 struct timeval tv; 785 786 microtime(&tv); 787 start = (tv.tv_usec >> 10) | tv.tv_usec; 788 len = 0; 789 } 790 791 /* 792 * Start at a (pseudo) random place to maximize cluster runs 793 * under multiple writers. 794 */ 795 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 796 foundl = 0; 797 798 for (cn = newst; cn <= pmp->pm_maxcluster;) { 799 idx = cn / N_INUSEBITS; 800 map = pmp->pm_inusemap[idx]; 801 map |= (1 << (cn % N_INUSEBITS)) - 1; 802 if (map != (u_int)-1) { 803 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 804 if ((l = chainlength(pmp, cn, count)) >= count) 805 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 806 if (l > foundl) { 807 foundcn = cn; 808 foundl = l; 809 } 810 cn += l + 1; 811 continue; 812 } 813 cn += N_INUSEBITS - cn % N_INUSEBITS; 814 } 815 for (cn = 0; cn < newst;) { 816 idx = cn / N_INUSEBITS; 817 map = pmp->pm_inusemap[idx]; 818 map |= (1 << (cn % N_INUSEBITS)) - 1; 819 if (map != (u_int)-1) { 820 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 821 if ((l = chainlength(pmp, cn, count)) >= count) 822 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 823 if (l > foundl) { 824 foundcn = cn; 825 foundl = l; 826 } 827 cn += l + 1; 828 continue; 829 } 830 cn += N_INUSEBITS - cn % N_INUSEBITS; 831 } 832 833 if (!foundl) 834 return (ENOSPC); 835 836 if (len) 837 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 838 else 839 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 840 } 841 842 843 /* 844 * Free a chain of clusters. 845 * 846 * pmp - address of the msdosfs mount structure for the filesystem 847 * containing the cluster chain to be freed. 848 * startcluster - number of the 1st cluster in the chain of clusters to be 849 * freed. 850 */ 851 int 852 freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 853 { 854 int error; 855 struct buf *bp = NULL; 856 u_long bn, bo, bsize, byteoffset; 857 u_long readcn, lbn = -1; 858 859 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 860 byteoffset = FATOFS(pmp, cluster); 861 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 862 if (lbn != bn) { 863 if (bp) 864 updatefats(pmp, bp, lbn); 865 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 866 NOCRED, B_MODIFY, &bp); 867 if (error) { 868 brelse(bp, 0); 869 return (error); 870 } 871 lbn = bn; 872 } 873 usemap_free(pmp, cluster); 874 KASSERT(bp != NULL); 875 switch (pmp->pm_fatmask) { 876 case FAT12_MASK: 877 readcn = getushort((char *)bp->b_data + bo); 878 if (cluster & 1) { 879 cluster = readcn >> 4; 880 readcn &= 0x000f; 881 readcn |= MSDOSFSFREE << 4; 882 } else { 883 cluster = readcn; 884 readcn &= 0xf000; 885 readcn |= MSDOSFSFREE & 0xfff; 886 } 887 putushort((char *)bp->b_data + bo, readcn); 888 break; 889 case FAT16_MASK: 890 cluster = getushort((char *)bp->b_data + bo); 891 putushort((char *)bp->b_data + bo, MSDOSFSFREE); 892 break; 893 case FAT32_MASK: 894 cluster = getulong((char *)bp->b_data + bo); 895 putulong((char *)bp->b_data + bo, 896 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 897 break; 898 } 899 cluster &= pmp->pm_fatmask; 900 } 901 if (bp) 902 updatefats(pmp, bp, bn); 903 return (0); 904 } 905 906 /* 907 * Read in fat blocks looking for free clusters. For every free cluster 908 * found turn off its corresponding bit in the pm_inusemap. 909 */ 910 int 911 fillinusemap(struct msdosfsmount *pmp) 912 { 913 struct buf *bp = NULL; 914 u_long cn, readcn; 915 int error; 916 u_long bn, bo, bsize, byteoffset; 917 918 /* 919 * Mark all clusters in use, we mark the free ones in the fat scan 920 * loop further down. 921 */ 922 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 923 pmp->pm_inusemap[cn] = (u_int)-1; 924 925 /* 926 * Figure how many free clusters are in the filesystem by ripping 927 * through the fat counting the number of entries whose content is 928 * zero. These represent free clusters. 929 */ 930 pmp->pm_freeclustercount = 0; 931 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 932 byteoffset = FATOFS(pmp, cn); 933 bo = byteoffset % pmp->pm_fatblocksize; 934 if (!bo || !bp) { 935 /* Read new FAT block */ 936 if (bp) 937 brelse(bp, 0); 938 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 939 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 940 NOCRED, 0, &bp); 941 if (error) { 942 brelse(bp, 0); 943 return (error); 944 } 945 } 946 if (FAT32(pmp)) 947 readcn = getulong((char *)bp->b_data + bo); 948 else 949 readcn = getushort((char *)bp->b_data + bo); 950 if (FAT12(pmp) && (cn & 1)) 951 readcn >>= 4; 952 readcn &= pmp->pm_fatmask; 953 954 if (readcn == 0) 955 usemap_free(pmp, cn); 956 } 957 if (bp) 958 brelse(bp, 0); 959 return (0); 960 } 961 962 /* 963 * Allocate a new cluster and chain it onto the end of the file. 964 * 965 * dep - the file to extend 966 * count - number of clusters to allocate 967 * bpp - where to return the address of the buf header for the first new 968 * file block 969 * ncp - where to put cluster number of the first newly allocated cluster 970 * If this pointer is 0, do not return the cluster number. 971 * flags - see fat.h 972 * 973 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 974 * the de_flag field of the denode and it does not change the de_FileSize 975 * field. This is left for the caller to do. 976 */ 977 978 int 979 extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, int flags) 980 { 981 int error; 982 u_long frcn = 0, cn, got; 983 struct msdosfsmount *pmp = dep->de_pmp; 984 struct buf *bp; 985 986 /* 987 * Don't try to extend the root directory 988 */ 989 if (dep->de_StartCluster == MSDOSFSROOT 990 && (dep->de_Attributes & ATTR_DIRECTORY)) { 991 printf("extendfile(): attempt to extend root directory\n"); 992 return (ENOSPC); 993 } 994 995 /* 996 * If the "file's last cluster" cache entry is empty, and the file 997 * is not empty, then fill the cache entry by calling pcbmap(). 998 */ 999 fc_fileextends++; 1000 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1001 dep->de_StartCluster != 0) { 1002 fc_lfcempty++; 1003 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 1004 /* we expect it to return E2BIG */ 1005 if (error != E2BIG) 1006 return (error); 1007 } 1008 1009 fc_last_to_nexttolast(dep); 1010 1011 while (count > 0) { 1012 1013 /* 1014 * Allocate a new cluster chain and cat onto the end of the 1015 * file. If the file is empty we make de_StartCluster point 1016 * to the new block. Note that de_StartCluster being 0 is 1017 * sufficient to be sure the file is empty since we exclude 1018 * attempts to extend the root directory above, and the root 1019 * dir is the only file with a startcluster of 0 that has 1020 * blocks allocated (sort of). 1021 */ 1022 1023 if (dep->de_StartCluster == 0) 1024 cn = 0; 1025 else 1026 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1027 error = clusteralloc(pmp, cn, count, &cn, &got); 1028 if (error) 1029 return (error); 1030 1031 count -= got; 1032 1033 /* 1034 * Give them the filesystem relative cluster number if they want 1035 * it. 1036 */ 1037 if (ncp) { 1038 *ncp = cn; 1039 ncp = NULL; 1040 } 1041 1042 if (dep->de_StartCluster == 0) { 1043 dep->de_StartCluster = cn; 1044 frcn = 0; 1045 } else { 1046 error = fatentry(FAT_SET, pmp, 1047 dep->de_fc[FC_LASTFC].fc_fsrcn, 1048 0, cn); 1049 if (error) { 1050 clusterfree(pmp, cn, NULL); 1051 return (error); 1052 } 1053 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1054 } 1055 1056 /* 1057 * Update the "last cluster of the file" entry in the 1058 * denode's fat cache. 1059 */ 1060 1061 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1062 if ((flags & DE_CLEAR) && 1063 (dep->de_Attributes & ATTR_DIRECTORY)) { 1064 while (got-- > 0) { 1065 bp = getblk(pmp->pm_devvp, 1066 de_bn2kb(pmp, cntobn(pmp, cn++)), 1067 pmp->pm_bpcluster, 0, 0); 1068 clrbuf(bp); 1069 if (bpp) { 1070 *bpp = bp; 1071 bpp = NULL; 1072 } else { 1073 bdwrite(bp); 1074 } 1075 } 1076 } 1077 } 1078 1079 return (0); 1080 } 1081