1 /* $NetBSD: msdosfs_fat.c,v 1.10 2006/05/14 21:31:52 elad 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 1.10 2006/05/14 21:31:52 elad 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 89 static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *, 90 u_long *); 91 void updatefats(struct msdosfsmount *, struct buf *, u_long); 92 static inline void usemap_free(struct msdosfsmount *, u_long); 93 static inline void usemap_alloc(struct msdosfsmount *, u_long); 94 static int fatchain(struct msdosfsmount *, u_long, u_long, u_long); 95 int chainlength(struct msdosfsmount *, u_long, u_long); 96 int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *, 97 u_long *); 98 99 static void 100 fatblock(pmp, ofs, bnp, sizep, bop) 101 struct msdosfsmount *pmp; 102 u_long ofs; 103 u_long *bnp; 104 u_long *sizep; 105 u_long *bop; 106 { 107 u_long bn, size; 108 109 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 110 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 111 * pmp->pm_BytesPerSec; 112 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 113 114 if (bnp) 115 *bnp = bn; 116 if (sizep) 117 *sizep = size; 118 if (bop) 119 *bop = ofs % pmp->pm_fatblocksize; 120 } 121 122 /* 123 * Map the logical cluster number of a file into a physical disk sector 124 * that is filesystem relative. 125 * 126 * dep - address of denode representing the file of interest 127 * findcn - file relative cluster whose filesystem relative cluster number 128 * and/or block number are/is to be found 129 * bnp - address of where to place the file system relative block number. 130 * If this pointer is null then don't return this quantity. 131 * cnp - address of where to place the file system relative cluster number. 132 * If this pointer is null then don't return this quantity. 133 * 134 * NOTE: Either bnp or cnp must be non-null. 135 * This function has one side effect. If the requested file relative cluster 136 * is beyond the end of file, then the actual number of clusters in the file 137 * is returned in *cnp. This is useful for determining how long a directory is. 138 * If cnp is null, nothing is returned. 139 */ 140 int 141 pcbmap(dep, findcn, bnp, cnp, sp) 142 struct denode *dep; 143 u_long findcn; /* file relative cluster to get */ 144 daddr_t *bnp; /* returned filesys relative blk number */ 145 u_long *cnp; /* returned cluster number */ 146 int *sp; /* returned block size */ 147 { 148 int error; 149 u_long i; 150 u_long cn; 151 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 152 u_long byteoffset; 153 u_long bn; 154 u_long bo; 155 struct buf *bp = NULL; 156 u_long bp_bn = -1; 157 struct msdosfsmount *pmp = dep->de_pmp; 158 u_long bsize; 159 160 fc_bmapcalls++; 161 162 /* 163 * If they don't give us someplace to return a value then don't 164 * bother doing anything. 165 */ 166 if (bnp == NULL && cnp == NULL && sp == NULL) 167 return (0); 168 169 cn = dep->de_StartCluster; 170 /* 171 * The "file" that makes up the root directory is contiguous, 172 * permanently allocated, of fixed size, and is not made up of 173 * clusters. If the cluster number is beyond the end of the root 174 * directory, then return the number of clusters in the file. 175 */ 176 if (cn == MSDOSFSROOT) { 177 if (dep->de_Attributes & ATTR_DIRECTORY) { 178 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 179 if (cnp) 180 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 181 return (E2BIG); 182 } 183 if (bnp) 184 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 185 if (cnp) 186 *cnp = MSDOSFSROOT; 187 if (sp) 188 *sp = min(pmp->pm_bpcluster, 189 dep->de_FileSize - de_cn2off(pmp, findcn)); 190 return (0); 191 } else { /* just an empty file */ 192 if (cnp) 193 *cnp = 0; 194 return (E2BIG); 195 } 196 } 197 198 /* 199 * All other files do I/O in cluster sized blocks 200 */ 201 if (sp) 202 *sp = pmp->pm_bpcluster; 203 204 /* 205 * Rummage around in the fat cache, maybe we can avoid tromping 206 * thru every fat entry for the file. And, keep track of how far 207 * off the cache was from where we wanted to be. 208 */ 209 i = 0; 210 fc_lookup(dep, findcn, &i, &cn); 211 if ((bn = findcn - i) >= LMMAX) 212 fc_largedistance++; 213 else 214 fc_lmdistance[bn]++; 215 216 /* 217 * Handle all other files or directories the normal way. 218 */ 219 for (; i < findcn; i++) { 220 /* 221 * Stop with all reserved clusters, not just with EOF. 222 */ 223 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask)) 224 goto hiteof; 225 byteoffset = FATOFS(pmp, cn); 226 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 227 if (bn != bp_bn) { 228 if (bp) 229 brelse(bp); 230 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 231 if (error) { 232 brelse(bp); 233 return (error); 234 } 235 bp_bn = bn; 236 } 237 prevcn = cn; 238 if (bo >= bsize) { 239 if (bp) 240 brelse(bp); 241 return (EIO); 242 } 243 KASSERT(bp != NULL); 244 if (FAT32(pmp)) 245 cn = getulong(&bp->b_data[bo]); 246 else 247 cn = getushort(&bp->b_data[bo]); 248 if (FAT12(pmp) && (prevcn & 1)) 249 cn >>= 4; 250 cn &= pmp->pm_fatmask; 251 } 252 253 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) { 254 if (bp) 255 brelse(bp); 256 if (bnp) 257 *bnp = cntobn(pmp, cn); 258 if (cnp) 259 *cnp = cn; 260 fc_setcache(dep, FC_LASTMAP, i, cn); 261 return (0); 262 } 263 264 hiteof:; 265 if (cnp) 266 *cnp = i; 267 if (bp) 268 brelse(bp); 269 /* update last file cluster entry in the fat cache */ 270 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 271 return (E2BIG); 272 } 273 274 /* 275 * Find the closest entry in the fat cache to the cluster we are looking 276 * for. 277 */ 278 void 279 fc_lookup(dep, findcn, frcnp, fsrcnp) 280 struct denode *dep; 281 u_long findcn; 282 u_long *frcnp; 283 u_long *fsrcnp; 284 { 285 int i; 286 u_long cn; 287 struct fatcache *closest = 0; 288 289 for (i = 0; i < FC_SIZE; i++) { 290 cn = dep->de_fc[i].fc_frcn; 291 if (cn != FCE_EMPTY && cn <= findcn) { 292 if (closest == 0 || cn > closest->fc_frcn) 293 closest = &dep->de_fc[i]; 294 } 295 } 296 if (closest) { 297 *frcnp = closest->fc_frcn; 298 *fsrcnp = closest->fc_fsrcn; 299 } 300 } 301 302 /* 303 * Purge the fat cache in denode dep of all entries relating to file 304 * relative cluster frcn and beyond. 305 */ 306 void 307 fc_purge(dep, frcn) 308 struct denode *dep; 309 u_int frcn; 310 { 311 int i; 312 struct fatcache *fcp; 313 314 fcp = dep->de_fc; 315 for (i = 0; i < FC_SIZE; i++, fcp++) { 316 if (fcp->fc_frcn >= frcn) 317 fcp->fc_frcn = FCE_EMPTY; 318 } 319 } 320 321 /* 322 * Update the fat. 323 * If mirroring the fat, update all copies, with the first copy as last. 324 * Else update only the current fat (ignoring the others). 325 * 326 * pmp - msdosfsmount structure for filesystem to update 327 * bp - addr of modified fat block 328 * fatbn - block number relative to begin of filesystem of the modified fat block. 329 */ 330 void 331 updatefats(pmp, bp, fatbn) 332 struct msdosfsmount *pmp; 333 struct buf *bp; 334 u_long fatbn; 335 { 336 int i; 337 struct buf *bpn; 338 339 #ifdef MSDOSFS_DEBUG 340 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", 341 pmp, bp, fatbn); 342 #endif 343 344 /* 345 * If we have an FSInfo block, update it. 346 */ 347 if (pmp->pm_fsinfo) { 348 u_long cn = pmp->pm_nxtfree; 349 350 if (pmp->pm_freeclustercount 351 && (pmp->pm_inusemap[cn / N_INUSEBITS] 352 & (1 << (cn % N_INUSEBITS)))) { 353 /* 354 * The cluster indicated in FSInfo isn't free 355 * any longer. Got get a new free one. 356 */ 357 for (cn = 0; cn < pmp->pm_maxcluster; cn++) 358 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 359 break; 360 pmp->pm_nxtfree = cn 361 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 362 ^ (u_int)-1) - 1; 363 } 364 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, 1024, NOCRED, &bpn) != 0) { 365 /* 366 * Ignore the error, but turn off FSInfo update for the future. 367 */ 368 pmp->pm_fsinfo = 0; 369 brelse(bpn); 370 } else { 371 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 372 373 putulong(fp->fsinfree, pmp->pm_freeclustercount); 374 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 375 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 376 bwrite(bpn); 377 else 378 bdwrite(bpn); 379 } 380 } 381 382 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 383 /* 384 * Now copy the block(s) of the modified fat to the other copies of 385 * the fat and write them out. This is faster than reading in the 386 * other fats and then writing them back out. This could tie up 387 * the fat for quite a while. Preventing others from accessing it. 388 * To prevent us from going after the fat quite so much we use 389 * delayed writes, unless they specfied "synchronous" when the 390 * filesystem was mounted. If synch is asked for then use 391 * bwrite()'s and really slow things down. 392 */ 393 for (i = 1; i < pmp->pm_FATs; i++) { 394 fatbn += pmp->pm_FATsecs; 395 /* getblk() never fails */ 396 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 397 memcpy(bpn->b_data, bp->b_data, bp->b_bcount); 398 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 399 bwrite(bpn); 400 else 401 bdwrite(bpn); 402 } 403 } 404 405 /* 406 * Write out the first (or current) fat last. 407 */ 408 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 409 bwrite(bp); 410 else 411 bdwrite(bp); 412 /* 413 * Maybe update fsinfo sector here? 414 */ 415 } 416 417 /* 418 * Updating entries in 12 bit fats is a pain in the butt. 419 * 420 * The following picture shows where nibbles go when moving from a 12 bit 421 * cluster number into the appropriate bytes in the FAT. 422 * 423 * byte m byte m+1 byte m+2 424 * +----+----+ +----+----+ +----+----+ 425 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 426 * +----+----+ +----+----+ +----+----+ 427 * 428 * +----+----+----+ +----+----+----+ 429 * | 3 0 1 | | 4 5 2 | 430 * +----+----+----+ +----+----+----+ 431 * cluster n cluster n+1 432 * 433 * Where n is even. m = n + (n >> 2) 434 * 435 */ 436 static inline void 437 usemap_alloc(pmp, cn) 438 struct msdosfsmount *pmp; 439 u_long cn; 440 { 441 442 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 443 pmp->pm_freeclustercount--; 444 } 445 446 static inline void 447 usemap_free(pmp, cn) 448 struct msdosfsmount *pmp; 449 u_long cn; 450 { 451 452 pmp->pm_freeclustercount++; 453 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 454 } 455 456 int 457 clusterfree(pmp, cluster, oldcnp) 458 struct msdosfsmount *pmp; 459 u_long cluster; 460 u_long *oldcnp; 461 { 462 int error; 463 u_long oldcn; 464 465 usemap_free(pmp, cluster); 466 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 467 if (error) { 468 usemap_alloc(pmp, cluster); 469 return (error); 470 } 471 /* 472 * If the cluster was successfully marked free, then update 473 * the count of free clusters, and turn off the "allocated" 474 * bit in the "in use" cluster bit map. 475 */ 476 if (oldcnp) 477 *oldcnp = oldcn; 478 return (0); 479 } 480 481 /* 482 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 483 * 484 * function - whether to get or set a fat entry 485 * pmp - address of the msdosfsmount structure for the filesystem 486 * whose fat is to be manipulated. 487 * cn - which cluster is of interest 488 * oldcontents - address of a word that is to receive the contents of the 489 * cluster'th entry if this is a get function 490 * newcontents - the new value to be written into the cluster'th element of 491 * the fat if this is a set function. 492 * 493 * This function can also be used to free a cluster by setting the fat entry 494 * for a cluster to 0. 495 * 496 * All copies of the fat are updated if this is a set function. NOTE: If 497 * fatentry() marks a cluster as free it does not update the inusemap in 498 * the msdosfsmount structure. This is left to the caller. 499 */ 500 int 501 fatentry(function, pmp, cn, oldcontents, newcontents) 502 int function; 503 struct msdosfsmount *pmp; 504 u_long cn; 505 u_long *oldcontents; 506 u_long newcontents; 507 { 508 int error; 509 u_long readcn; 510 u_long bn, bo, bsize, byteoffset; 511 struct buf *bp; 512 513 #ifdef MSDOSFS_DEBUG 514 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 515 function, pmp, cn, oldcontents, newcontents); 516 #endif 517 518 #ifdef DIAGNOSTIC 519 /* 520 * Be sure they asked us to do something. 521 */ 522 if ((function & (FAT_SET | FAT_GET)) == 0) { 523 printf("fatentry(): function code doesn't specify get or set\n"); 524 return (EINVAL); 525 } 526 527 /* 528 * If they asked us to return a cluster number but didn't tell us 529 * where to put it, give them an error. 530 */ 531 if ((function & FAT_GET) && oldcontents == NULL) { 532 printf("fatentry(): get function with no place to put result\n"); 533 return (EINVAL); 534 } 535 #endif 536 537 /* 538 * Be sure the requested cluster is in the filesystem. 539 */ 540 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 541 return (EINVAL); 542 543 byteoffset = FATOFS(pmp, cn); 544 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 545 if ((error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp)) != 0) { 546 brelse(bp); 547 return (error); 548 } 549 550 if (function & FAT_GET) { 551 if (FAT32(pmp)) 552 readcn = getulong(&bp->b_data[bo]); 553 else 554 readcn = getushort(&bp->b_data[bo]); 555 if (FAT12(pmp) & (cn & 1)) 556 readcn >>= 4; 557 readcn &= pmp->pm_fatmask; 558 *oldcontents = readcn; 559 } 560 if (function & FAT_SET) { 561 switch (pmp->pm_fatmask) { 562 case FAT12_MASK: 563 readcn = getushort(&bp->b_data[bo]); 564 if (cn & 1) { 565 readcn &= 0x000f; 566 readcn |= newcontents << 4; 567 } else { 568 readcn &= 0xf000; 569 readcn |= newcontents & 0xfff; 570 } 571 putushort(&bp->b_data[bo], readcn); 572 break; 573 case FAT16_MASK: 574 putushort(&bp->b_data[bo], newcontents); 575 break; 576 case FAT32_MASK: 577 /* 578 * According to spec we have to retain the 579 * high order bits of the fat entry. 580 */ 581 readcn = getulong(&bp->b_data[bo]); 582 readcn &= ~FAT32_MASK; 583 readcn |= newcontents & FAT32_MASK; 584 putulong(&bp->b_data[bo], readcn); 585 break; 586 } 587 updatefats(pmp, bp, bn); 588 bp = NULL; 589 pmp->pm_fmod = 1; 590 } 591 if (bp) 592 brelse(bp); 593 return (0); 594 } 595 596 /* 597 * Update a contiguous cluster chain 598 * 599 * pmp - mount point 600 * start - first cluster of chain 601 * count - number of clusters in chain 602 * fillwith - what to write into fat entry of last cluster 603 */ 604 static int 605 fatchain(pmp, start, count, fillwith) 606 struct msdosfsmount *pmp; 607 u_long start; 608 u_long count; 609 u_long fillwith; 610 { 611 int error; 612 u_long bn, bo, bsize, byteoffset, readcn, newc; 613 struct buf *bp; 614 615 #ifdef MSDOSFS_DEBUG 616 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 617 pmp, start, count, fillwith); 618 #endif 619 /* 620 * Be sure the clusters are in the filesystem. 621 */ 622 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 623 return (EINVAL); 624 625 while (count > 0) { 626 byteoffset = FATOFS(pmp, start); 627 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 628 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 629 if (error) { 630 brelse(bp); 631 return (error); 632 } 633 while (count > 0) { 634 start++; 635 newc = --count > 0 ? start : fillwith; 636 switch (pmp->pm_fatmask) { 637 case FAT12_MASK: 638 readcn = getushort(&bp->b_data[bo]); 639 if (start & 1) { 640 readcn &= 0xf000; 641 readcn |= newc & 0xfff; 642 } else { 643 readcn &= 0x000f; 644 readcn |= newc << 4; 645 } 646 putushort(&bp->b_data[bo], readcn); 647 bo++; 648 if (!(start & 1)) 649 bo++; 650 break; 651 case FAT16_MASK: 652 putushort(&bp->b_data[bo], newc); 653 bo += 2; 654 break; 655 case FAT32_MASK: 656 readcn = getulong(&bp->b_data[bo]); 657 readcn &= ~pmp->pm_fatmask; 658 readcn |= newc & pmp->pm_fatmask; 659 putulong(&bp->b_data[bo], readcn); 660 bo += 4; 661 break; 662 } 663 if (bo >= bsize) 664 break; 665 } 666 updatefats(pmp, bp, bn); 667 } 668 pmp->pm_fmod = 1; 669 return (0); 670 } 671 672 /* 673 * Check the length of a free cluster chain starting at start. 674 * 675 * pmp - mount point 676 * start - start of chain 677 * count - maximum interesting length 678 */ 679 int 680 chainlength(pmp, start, count) 681 struct msdosfsmount *pmp; 682 u_long start; 683 u_long count; 684 { 685 u_long idx, max_idx; 686 u_int map; 687 u_long len; 688 689 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 690 idx = start / N_INUSEBITS; 691 start %= N_INUSEBITS; 692 map = pmp->pm_inusemap[idx]; 693 map &= ~((1 << start) - 1); 694 if (map) { 695 len = ffs(map) - 1 - start; 696 return (len > count ? count : len); 697 } 698 len = N_INUSEBITS - start; 699 if (len >= count) 700 return (count); 701 while (++idx <= max_idx) { 702 if (len >= count) 703 break; 704 if ((map = pmp->pm_inusemap[idx]) != 0) { 705 len += ffs(map) - 1; 706 break; 707 } 708 len += N_INUSEBITS; 709 } 710 return (len > count ? count : len); 711 } 712 713 /* 714 * Allocate contigous free clusters. 715 * 716 * pmp - mount point. 717 * start - start of cluster chain. 718 * count - number of clusters to allocate. 719 * fillwith - put this value into the fat entry for the 720 * last allocated cluster. 721 * retcluster - put the first allocated cluster's number here. 722 * got - how many clusters were actually allocated. 723 */ 724 int 725 chainalloc(pmp, start, count, fillwith, retcluster, got) 726 struct msdosfsmount *pmp; 727 u_long start; 728 u_long count; 729 u_long fillwith; 730 u_long *retcluster; 731 u_long *got; 732 { 733 int error; 734 u_long cl, n; 735 736 for (cl = start, n = count; n-- > 0;) 737 usemap_alloc(pmp, cl++); 738 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 739 return (error); 740 #ifdef MSDOSFS_DEBUG 741 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 742 start, count); 743 #endif 744 if (retcluster) 745 *retcluster = start; 746 if (got) 747 *got = count; 748 return (0); 749 } 750 751 /* 752 * Allocate contiguous free clusters. 753 * 754 * pmp - mount point. 755 * start - preferred start of cluster chain. 756 * count - number of clusters requested. 757 * fillwith - put this value into the fat entry for the 758 * last allocated cluster. 759 * retcluster - put the first allocated cluster's number here. 760 * got - how many clusters were actually allocated. 761 */ 762 int 763 clusteralloc(pmp, start, count, retcluster, got) 764 struct msdosfsmount *pmp; 765 u_long start; 766 u_long count; 767 u_long *retcluster; 768 u_long *got; 769 { 770 u_long idx; 771 u_long len, newst, foundl, cn, l; 772 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 773 u_long fillwith = CLUST_EOFE; 774 u_int map; 775 776 #ifdef MSDOSFS_DEBUG 777 printf("clusteralloc(): find %lu clusters\n",count); 778 #endif 779 if (start) { 780 if ((len = chainlength(pmp, start, count)) >= count) 781 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 782 } else { 783 /* 784 * This is a new file, initialize start 785 */ 786 struct timeval tv; 787 788 microtime(&tv); 789 start = (tv.tv_usec >> 10) | tv.tv_usec; 790 len = 0; 791 } 792 793 /* 794 * Start at a (pseudo) random place to maximize cluster runs 795 * under multiple writers. 796 */ 797 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 798 foundl = 0; 799 800 for (cn = newst; cn <= pmp->pm_maxcluster;) { 801 idx = cn / N_INUSEBITS; 802 map = pmp->pm_inusemap[idx]; 803 map |= (1 << (cn % N_INUSEBITS)) - 1; 804 if (map != (u_int)-1) { 805 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 806 if ((l = chainlength(pmp, cn, count)) >= count) 807 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 808 if (l > foundl) { 809 foundcn = cn; 810 foundl = l; 811 } 812 cn += l + 1; 813 continue; 814 } 815 cn += N_INUSEBITS - cn % N_INUSEBITS; 816 } 817 for (cn = 0; cn < newst;) { 818 idx = cn / N_INUSEBITS; 819 map = pmp->pm_inusemap[idx]; 820 map |= (1 << (cn % N_INUSEBITS)) - 1; 821 if (map != (u_int)-1) { 822 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 823 if ((l = chainlength(pmp, cn, count)) >= count) 824 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 825 if (l > foundl) { 826 foundcn = cn; 827 foundl = l; 828 } 829 cn += l + 1; 830 continue; 831 } 832 cn += N_INUSEBITS - cn % N_INUSEBITS; 833 } 834 835 if (!foundl) 836 return (ENOSPC); 837 838 if (len) 839 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 840 else 841 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 842 } 843 844 845 /* 846 * Free a chain of clusters. 847 * 848 * pmp - address of the msdosfs mount structure for the filesystem 849 * containing the cluster chain to be freed. 850 * startcluster - number of the 1st cluster in the chain of clusters to be 851 * freed. 852 */ 853 int 854 freeclusterchain(pmp, cluster) 855 struct msdosfsmount *pmp; 856 u_long cluster; 857 { 858 int error; 859 struct buf *bp = NULL; 860 u_long bn, bo, bsize, byteoffset; 861 u_long readcn, lbn = -1; 862 863 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 864 byteoffset = FATOFS(pmp, cluster); 865 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 866 if (lbn != bn) { 867 if (bp) 868 updatefats(pmp, bp, lbn); 869 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 870 if (error) { 871 brelse(bp); 872 return (error); 873 } 874 lbn = bn; 875 } 876 usemap_free(pmp, cluster); 877 KASSERT(bp != NULL); 878 switch (pmp->pm_fatmask) { 879 case FAT12_MASK: 880 readcn = getushort(&bp->b_data[bo]); 881 if (cluster & 1) { 882 cluster = readcn >> 4; 883 readcn &= 0x000f; 884 readcn |= MSDOSFSFREE << 4; 885 } else { 886 cluster = readcn; 887 readcn &= 0xf000; 888 readcn |= MSDOSFSFREE & 0xfff; 889 } 890 putushort(&bp->b_data[bo], readcn); 891 break; 892 case FAT16_MASK: 893 cluster = getushort(&bp->b_data[bo]); 894 putushort(&bp->b_data[bo], MSDOSFSFREE); 895 break; 896 case FAT32_MASK: 897 cluster = getulong(&bp->b_data[bo]); 898 putulong(&bp->b_data[bo], 899 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 900 break; 901 } 902 cluster &= pmp->pm_fatmask; 903 } 904 if (bp) 905 updatefats(pmp, bp, bn); 906 return (0); 907 } 908 909 /* 910 * Read in fat blocks looking for free clusters. For every free cluster 911 * found turn off its corresponding bit in the pm_inusemap. 912 */ 913 int 914 fillinusemap(pmp) 915 struct msdosfsmount *pmp; 916 { 917 struct buf *bp = NULL; 918 u_long cn, readcn; 919 int error; 920 u_long bn, bo, bsize, byteoffset; 921 922 /* 923 * Mark all clusters in use, we mark the free ones in the fat scan 924 * loop further down. 925 */ 926 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 927 pmp->pm_inusemap[cn] = (u_int)-1; 928 929 /* 930 * Figure how many free clusters are in the filesystem by ripping 931 * through the fat counting the number of entries whose content is 932 * zero. These represent free clusters. 933 */ 934 pmp->pm_freeclustercount = 0; 935 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 936 byteoffset = FATOFS(pmp, cn); 937 bo = byteoffset % pmp->pm_fatblocksize; 938 if (!bo || !bp) { 939 /* Read new FAT block */ 940 if (bp) 941 brelse(bp); 942 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 943 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 944 if (error) { 945 brelse(bp); 946 return (error); 947 } 948 } 949 if (FAT32(pmp)) 950 readcn = getulong(&bp->b_data[bo]); 951 else 952 readcn = getushort(&bp->b_data[bo]); 953 if (FAT12(pmp) && (cn & 1)) 954 readcn >>= 4; 955 readcn &= pmp->pm_fatmask; 956 957 if (readcn == 0) 958 usemap_free(pmp, cn); 959 } 960 brelse(bp); 961 return (0); 962 } 963 964 /* 965 * Allocate a new cluster and chain it onto the end of the file. 966 * 967 * dep - the file to extend 968 * count - number of clusters to allocate 969 * bpp - where to return the address of the buf header for the first new 970 * file block 971 * ncp - where to put cluster number of the first newly allocated cluster 972 * If this pointer is 0, do not return the cluster number. 973 * flags - see fat.h 974 * 975 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 976 * the de_flag field of the denode and it does not change the de_FileSize 977 * field. This is left for the caller to do. 978 */ 979 980 int 981 extendfile(dep, count, bpp, ncp, flags) 982 struct denode *dep; 983 u_long count; 984 struct buf **bpp; 985 u_long *ncp; 986 int flags; 987 { 988 int error; 989 u_long frcn = 0, cn, got; 990 struct msdosfsmount *pmp = dep->de_pmp; 991 struct buf *bp; 992 993 /* 994 * Don't try to extend the root directory 995 */ 996 if (dep->de_StartCluster == MSDOSFSROOT 997 && (dep->de_Attributes & ATTR_DIRECTORY)) { 998 printf("extendfile(): attempt to extend root directory\n"); 999 return (ENOSPC); 1000 } 1001 1002 /* 1003 * If the "file's last cluster" cache entry is empty, and the file 1004 * is not empty, then fill the cache entry by calling pcbmap(). 1005 */ 1006 fc_fileextends++; 1007 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1008 dep->de_StartCluster != 0) { 1009 fc_lfcempty++; 1010 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 1011 /* we expect it to return E2BIG */ 1012 if (error != E2BIG) 1013 return (error); 1014 } 1015 1016 while (count > 0) { 1017 1018 /* 1019 * Allocate a new cluster chain and cat onto the end of the 1020 * file. If the file is empty we make de_StartCluster point 1021 * to the new block. Note that de_StartCluster being 0 is 1022 * sufficient to be sure the file is empty since we exclude 1023 * attempts to extend the root directory above, and the root 1024 * dir is the only file with a startcluster of 0 that has 1025 * blocks allocated (sort of). 1026 */ 1027 1028 if (dep->de_StartCluster == 0) 1029 cn = 0; 1030 else 1031 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1032 error = clusteralloc(pmp, cn, count, &cn, &got); 1033 if (error) 1034 return (error); 1035 1036 count -= got; 1037 1038 /* 1039 * Give them the filesystem relative cluster number if they want 1040 * it. 1041 */ 1042 if (ncp) { 1043 *ncp = cn; 1044 ncp = NULL; 1045 } 1046 1047 if (dep->de_StartCluster == 0) { 1048 dep->de_StartCluster = cn; 1049 frcn = 0; 1050 } else { 1051 error = fatentry(FAT_SET, pmp, 1052 dep->de_fc[FC_LASTFC].fc_fsrcn, 1053 0, cn); 1054 if (error) { 1055 clusterfree(pmp, cn, NULL); 1056 return (error); 1057 } 1058 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1059 } 1060 1061 /* 1062 * Update the "last cluster of the file" entry in the 1063 * denode's fat cache. 1064 */ 1065 1066 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1067 if ((flags & DE_CLEAR) && 1068 (dep->de_Attributes & ATTR_DIRECTORY)) { 1069 while (got-- > 0) { 1070 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1071 pmp->pm_bpcluster, 0, 0); 1072 clrbuf(bp); 1073 if (bpp) { 1074 *bpp = bp; 1075 bpp = NULL; 1076 } else { 1077 bdwrite(bp); 1078 } 1079 } 1080 } 1081 } 1082 1083 return (0); 1084 } 1085