1 /* $NetBSD: msdosfs_fat.c,v 1.1 2002/12/26 12:31:34 jdolecek 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 1.1 2002/12/26 12:31:34 jdolecek 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 statfs structure */ 62 #include <sys/vnode.h> /* to define vattr structure */ 63 #include <sys/errno.h> 64 #include <sys/dirent.h> 65 66 /* 67 * msdosfs include files. 68 */ 69 #include <fs/msdosfs/bpb.h> 70 #include <fs/msdosfs/msdosfsmount.h> 71 #include <fs/msdosfs/direntry.h> 72 #include <fs/msdosfs/denode.h> 73 #include <fs/msdosfs/fat.h> 74 75 /* 76 * Fat cache stats. 77 */ 78 int fc_fileextends; /* # of file extends */ 79 int fc_lfcempty; /* # of time last file cluster cache entry 80 * was empty */ 81 int fc_bmapcalls; /* # of times pcbmap was called */ 82 83 #define LMMAX 20 84 int fc_lmdistance[LMMAX]; /* counters for how far off the last 85 * cluster mapped entry was. */ 86 int fc_largedistance; /* off by more than LMMAX */ 87 88 static void fatblock __P((struct msdosfsmount *, u_long, u_long *, u_long *, 89 u_long *)); 90 void updatefats __P((struct msdosfsmount *, struct buf *, u_long)); 91 static __inline void usemap_free __P((struct msdosfsmount *, u_long)); 92 static __inline void usemap_alloc __P((struct msdosfsmount *, u_long)); 93 static int fatchain __P((struct msdosfsmount *, u_long, u_long, u_long)); 94 int chainlength __P((struct msdosfsmount *, u_long, u_long)); 95 int chainalloc __P((struct msdosfsmount *, u_long, u_long, u_long, u_long *, 96 u_long *)); 97 98 static void 99 fatblock(pmp, ofs, bnp, sizep, bop) 100 struct msdosfsmount *pmp; 101 u_long ofs; 102 u_long *bnp; 103 u_long *sizep; 104 u_long *bop; 105 { 106 u_long bn, size; 107 108 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 109 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 110 * pmp->pm_BytesPerSec; 111 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 112 113 if (bnp) 114 *bnp = bn; 115 if (sizep) 116 *sizep = size; 117 if (bop) 118 *bop = ofs % pmp->pm_fatblocksize; 119 } 120 121 /* 122 * Map the logical cluster number of a file into a physical disk sector 123 * that is filesystem relative. 124 * 125 * dep - address of denode representing the file of interest 126 * findcn - file relative cluster whose filesystem relative cluster number 127 * and/or block number are/is to be found 128 * bnp - address of where to place the file system relative block number. 129 * If this pointer is null then don't return this quantity. 130 * cnp - address of where to place the file system relative cluster number. 131 * If this pointer is null then don't return this quantity. 132 * 133 * NOTE: Either bnp or cnp must be non-null. 134 * This function has one side effect. If the requested file relative cluster 135 * is beyond the end of file, then the actual number of clusters in the file 136 * is returned in *cnp. This is useful for determining how long a directory is. 137 * If cnp is null, nothing is returned. 138 */ 139 int 140 pcbmap(dep, findcn, bnp, cnp, sp) 141 struct denode *dep; 142 u_long findcn; /* file relative cluster to get */ 143 daddr_t *bnp; /* returned filesys relative blk number */ 144 u_long *cnp; /* returned cluster number */ 145 int *sp; /* returned block size */ 146 { 147 int error; 148 u_long i; 149 u_long cn; 150 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 151 u_long byteoffset; 152 u_long bn; 153 u_long bo; 154 struct buf *bp = NULL; 155 u_long bp_bn = -1; 156 struct msdosfsmount *pmp = dep->de_pmp; 157 u_long bsize; 158 159 fc_bmapcalls++; 160 161 /* 162 * If they don't give us someplace to return a value then don't 163 * bother doing anything. 164 */ 165 if (bnp == NULL && cnp == NULL && sp == NULL) 166 return (0); 167 168 cn = dep->de_StartCluster; 169 /* 170 * The "file" that makes up the root directory is contiguous, 171 * permanently allocated, of fixed size, and is not made up of 172 * clusters. If the cluster number is beyond the end of the root 173 * directory, then return the number of clusters in the file. 174 */ 175 if (cn == MSDOSFSROOT) { 176 if (dep->de_Attributes & ATTR_DIRECTORY) { 177 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 178 if (cnp) 179 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 180 return (E2BIG); 181 } 182 if (bnp) 183 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 184 if (cnp) 185 *cnp = MSDOSFSROOT; 186 if (sp) 187 *sp = min(pmp->pm_bpcluster, 188 dep->de_FileSize - de_cn2off(pmp, findcn)); 189 return (0); 190 } else { /* just an empty file */ 191 if (cnp) 192 *cnp = 0; 193 return (E2BIG); 194 } 195 } 196 197 /* 198 * All other files do I/O in cluster sized blocks 199 */ 200 if (sp) 201 *sp = pmp->pm_bpcluster; 202 203 /* 204 * Rummage around in the fat cache, maybe we can avoid tromping 205 * thru every fat entry for the file. And, keep track of how far 206 * off the cache was from where we wanted to be. 207 */ 208 i = 0; 209 fc_lookup(dep, findcn, &i, &cn); 210 if ((bn = findcn - i) >= LMMAX) 211 fc_largedistance++; 212 else 213 fc_lmdistance[bn]++; 214 215 /* 216 * Handle all other files or directories the normal way. 217 */ 218 for (; i < findcn; i++) { 219 /* 220 * Stop with all reserved clusters, not just with EOF. 221 */ 222 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask)) 223 goto hiteof; 224 byteoffset = FATOFS(pmp, cn); 225 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 226 if (bn != bp_bn) { 227 if (bp) 228 brelse(bp); 229 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 230 if (error) { 231 brelse(bp); 232 return (error); 233 } 234 bp_bn = bn; 235 } 236 prevcn = cn; 237 if (FAT32(pmp)) 238 cn = getulong(&bp->b_data[bo]); 239 else 240 cn = getushort(&bp->b_data[bo]); 241 if (FAT12(pmp) && (prevcn & 1)) 242 cn >>= 4; 243 cn &= pmp->pm_fatmask; 244 } 245 246 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) { 247 if (bp) 248 brelse(bp); 249 if (bnp) 250 *bnp = cntobn(pmp, cn); 251 if (cnp) 252 *cnp = cn; 253 fc_setcache(dep, FC_LASTMAP, i, cn); 254 return (0); 255 } 256 257 hiteof:; 258 if (cnp) 259 *cnp = i; 260 if (bp) 261 brelse(bp); 262 /* update last file cluster entry in the fat cache */ 263 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 264 return (E2BIG); 265 } 266 267 /* 268 * Find the closest entry in the fat cache to the cluster we are looking 269 * for. 270 */ 271 void 272 fc_lookup(dep, findcn, frcnp, fsrcnp) 273 struct denode *dep; 274 u_long findcn; 275 u_long *frcnp; 276 u_long *fsrcnp; 277 { 278 int i; 279 u_long cn; 280 struct fatcache *closest = 0; 281 282 for (i = 0; i < FC_SIZE; i++) { 283 cn = dep->de_fc[i].fc_frcn; 284 if (cn != FCE_EMPTY && cn <= findcn) { 285 if (closest == 0 || cn > closest->fc_frcn) 286 closest = &dep->de_fc[i]; 287 } 288 } 289 if (closest) { 290 *frcnp = closest->fc_frcn; 291 *fsrcnp = closest->fc_fsrcn; 292 } 293 } 294 295 /* 296 * Purge the fat cache in denode dep of all entries relating to file 297 * relative cluster frcn and beyond. 298 */ 299 void 300 fc_purge(dep, frcn) 301 struct denode *dep; 302 u_int frcn; 303 { 304 int i; 305 struct fatcache *fcp; 306 307 fcp = dep->de_fc; 308 for (i = 0; i < FC_SIZE; i++, fcp++) { 309 if (fcp->fc_frcn >= frcn) 310 fcp->fc_frcn = FCE_EMPTY; 311 } 312 } 313 314 /* 315 * Update the fat. 316 * If mirroring the fat, update all copies, with the first copy as last. 317 * Else update only the current fat (ignoring the others). 318 * 319 * pmp - msdosfsmount structure for filesystem to update 320 * bp - addr of modified fat block 321 * fatbn - block number relative to begin of filesystem of the modified fat block. 322 */ 323 void 324 updatefats(pmp, bp, fatbn) 325 struct msdosfsmount *pmp; 326 struct buf *bp; 327 u_long fatbn; 328 { 329 int i; 330 struct buf *bpn; 331 332 #ifdef MSDOSFS_DEBUG 333 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", 334 pmp, bp, fatbn); 335 #endif 336 337 /* 338 * If we have an FSInfo block, update it. 339 */ 340 if (pmp->pm_fsinfo) { 341 u_long cn = pmp->pm_nxtfree; 342 343 if (pmp->pm_freeclustercount 344 && (pmp->pm_inusemap[cn / N_INUSEBITS] 345 & (1 << (cn % N_INUSEBITS)))) { 346 /* 347 * The cluster indicated in FSInfo isn't free 348 * any longer. Got get a new free one. 349 */ 350 for (cn = 0; cn < pmp->pm_maxcluster; cn++) 351 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 352 break; 353 pmp->pm_nxtfree = cn 354 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 355 ^ (u_int)-1) - 1; 356 } 357 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, 1024, NOCRED, &bpn) != 0) { 358 /* 359 * Ignore the error, but turn off FSInfo update for the future. 360 */ 361 pmp->pm_fsinfo = 0; 362 brelse(bpn); 363 } else { 364 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 365 366 putulong(fp->fsinfree, pmp->pm_freeclustercount); 367 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 368 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 369 bwrite(bpn); 370 else 371 bdwrite(bpn); 372 } 373 } 374 375 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 376 /* 377 * Now copy the block(s) of the modified fat to the other copies of 378 * the fat and write them out. This is faster than reading in the 379 * other fats and then writing them back out. This could tie up 380 * the fat for quite a while. Preventing others from accessing it. 381 * To prevent us from going after the fat quite so much we use 382 * delayed writes, unless they specfied "synchronous" when the 383 * filesystem was mounted. If synch is asked for then use 384 * bwrite()'s and really slow things down. 385 */ 386 for (i = 1; i < pmp->pm_FATs; i++) { 387 fatbn += pmp->pm_FATsecs; 388 /* getblk() never fails */ 389 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 390 memcpy(bpn->b_data, bp->b_data, bp->b_bcount); 391 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 392 bwrite(bpn); 393 else 394 bdwrite(bpn); 395 } 396 } 397 398 /* 399 * Write out the first (or current) fat last. 400 */ 401 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 402 bwrite(bp); 403 else 404 bdwrite(bp); 405 /* 406 * Maybe update fsinfo sector here? 407 */ 408 } 409 410 /* 411 * Updating entries in 12 bit fats is a pain in the butt. 412 * 413 * The following picture shows where nibbles go when moving from a 12 bit 414 * cluster number into the appropriate bytes in the FAT. 415 * 416 * byte m byte m+1 byte m+2 417 * +----+----+ +----+----+ +----+----+ 418 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 419 * +----+----+ +----+----+ +----+----+ 420 * 421 * +----+----+----+ +----+----+----+ 422 * | 3 0 1 | | 4 5 2 | 423 * +----+----+----+ +----+----+----+ 424 * cluster n cluster n+1 425 * 426 * Where n is even. m = n + (n >> 2) 427 * 428 */ 429 static __inline void 430 usemap_alloc(pmp, cn) 431 struct msdosfsmount *pmp; 432 u_long cn; 433 { 434 435 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 436 pmp->pm_freeclustercount--; 437 } 438 439 static __inline void 440 usemap_free(pmp, cn) 441 struct msdosfsmount *pmp; 442 u_long cn; 443 { 444 445 pmp->pm_freeclustercount++; 446 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 447 } 448 449 int 450 clusterfree(pmp, cluster, oldcnp) 451 struct msdosfsmount *pmp; 452 u_long cluster; 453 u_long *oldcnp; 454 { 455 int error; 456 u_long oldcn; 457 458 usemap_free(pmp, cluster); 459 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 460 if (error) { 461 usemap_alloc(pmp, cluster); 462 return (error); 463 } 464 /* 465 * If the cluster was successfully marked free, then update 466 * the count of free clusters, and turn off the "allocated" 467 * bit in the "in use" cluster bit map. 468 */ 469 if (oldcnp) 470 *oldcnp = oldcn; 471 return (0); 472 } 473 474 /* 475 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 476 * 477 * function - whether to get or set a fat entry 478 * pmp - address of the msdosfsmount structure for the filesystem 479 * whose fat is to be manipulated. 480 * cn - which cluster is of interest 481 * oldcontents - address of a word that is to receive the contents of the 482 * cluster'th entry if this is a get function 483 * newcontents - the new value to be written into the cluster'th element of 484 * the fat if this is a set function. 485 * 486 * This function can also be used to free a cluster by setting the fat entry 487 * for a cluster to 0. 488 * 489 * All copies of the fat are updated if this is a set function. NOTE: If 490 * fatentry() marks a cluster as free it does not update the inusemap in 491 * the msdosfsmount structure. This is left to the caller. 492 */ 493 int 494 fatentry(function, pmp, cn, oldcontents, newcontents) 495 int function; 496 struct msdosfsmount *pmp; 497 u_long cn; 498 u_long *oldcontents; 499 u_long newcontents; 500 { 501 int error; 502 u_long readcn; 503 u_long bn, bo, bsize, byteoffset; 504 struct buf *bp; 505 506 #ifdef MSDOSFS_DEBUG 507 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 508 function, pmp, cn, oldcontents, newcontents); 509 #endif 510 511 #ifdef DIAGNOSTIC 512 /* 513 * Be sure they asked us to do something. 514 */ 515 if ((function & (FAT_SET | FAT_GET)) == 0) { 516 printf("fatentry(): function code doesn't specify get or set\n"); 517 return (EINVAL); 518 } 519 520 /* 521 * If they asked us to return a cluster number but didn't tell us 522 * where to put it, give them an error. 523 */ 524 if ((function & FAT_GET) && oldcontents == NULL) { 525 printf("fatentry(): get function with no place to put result\n"); 526 return (EINVAL); 527 } 528 #endif 529 530 /* 531 * Be sure the requested cluster is in the filesystem. 532 */ 533 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 534 return (EINVAL); 535 536 byteoffset = FATOFS(pmp, cn); 537 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 538 if ((error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp)) != 0) { 539 brelse(bp); 540 return (error); 541 } 542 543 if (function & FAT_GET) { 544 if (FAT32(pmp)) 545 readcn = getulong(&bp->b_data[bo]); 546 else 547 readcn = getushort(&bp->b_data[bo]); 548 if (FAT12(pmp) & (cn & 1)) 549 readcn >>= 4; 550 readcn &= pmp->pm_fatmask; 551 *oldcontents = readcn; 552 } 553 if (function & FAT_SET) { 554 switch (pmp->pm_fatmask) { 555 case FAT12_MASK: 556 readcn = getushort(&bp->b_data[bo]); 557 if (cn & 1) { 558 readcn &= 0x000f; 559 readcn |= newcontents << 4; 560 } else { 561 readcn &= 0xf000; 562 readcn |= newcontents & 0xfff; 563 } 564 putushort(&bp->b_data[bo], readcn); 565 break; 566 case FAT16_MASK: 567 putushort(&bp->b_data[bo], newcontents); 568 break; 569 case FAT32_MASK: 570 /* 571 * According to spec we have to retain the 572 * high order bits of the fat entry. 573 */ 574 readcn = getulong(&bp->b_data[bo]); 575 readcn &= ~FAT32_MASK; 576 readcn |= newcontents & FAT32_MASK; 577 putulong(&bp->b_data[bo], readcn); 578 break; 579 } 580 updatefats(pmp, bp, bn); 581 bp = NULL; 582 pmp->pm_fmod = 1; 583 } 584 if (bp) 585 brelse(bp); 586 return (0); 587 } 588 589 /* 590 * Update a contiguous cluster chain 591 * 592 * pmp - mount point 593 * start - first cluster of chain 594 * count - number of clusters in chain 595 * fillwith - what to write into fat entry of last cluster 596 */ 597 static int 598 fatchain(pmp, start, count, fillwith) 599 struct msdosfsmount *pmp; 600 u_long start; 601 u_long count; 602 u_long fillwith; 603 { 604 int error; 605 u_long bn, bo, bsize, byteoffset, readcn, newc; 606 struct buf *bp; 607 608 #ifdef MSDOSFS_DEBUG 609 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 610 pmp, start, count, fillwith); 611 #endif 612 /* 613 * Be sure the clusters are in the filesystem. 614 */ 615 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 616 return (EINVAL); 617 618 while (count > 0) { 619 byteoffset = FATOFS(pmp, start); 620 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 621 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 622 if (error) { 623 brelse(bp); 624 return (error); 625 } 626 while (count > 0) { 627 start++; 628 newc = --count > 0 ? start : fillwith; 629 switch (pmp->pm_fatmask) { 630 case FAT12_MASK: 631 readcn = getushort(&bp->b_data[bo]); 632 if (start & 1) { 633 readcn &= 0xf000; 634 readcn |= newc & 0xfff; 635 } else { 636 readcn &= 0x000f; 637 readcn |= newc << 4; 638 } 639 putushort(&bp->b_data[bo], readcn); 640 bo++; 641 if (!(start & 1)) 642 bo++; 643 break; 644 case FAT16_MASK: 645 putushort(&bp->b_data[bo], newc); 646 bo += 2; 647 break; 648 case FAT32_MASK: 649 readcn = getulong(&bp->b_data[bo]); 650 readcn &= ~pmp->pm_fatmask; 651 readcn |= newc & pmp->pm_fatmask; 652 putulong(&bp->b_data[bo], readcn); 653 bo += 4; 654 break; 655 } 656 if (bo >= bsize) 657 break; 658 } 659 updatefats(pmp, bp, bn); 660 } 661 pmp->pm_fmod = 1; 662 return (0); 663 } 664 665 /* 666 * Check the length of a free cluster chain starting at start. 667 * 668 * pmp - mount point 669 * start - start of chain 670 * count - maximum interesting length 671 */ 672 int 673 chainlength(pmp, start, count) 674 struct msdosfsmount *pmp; 675 u_long start; 676 u_long count; 677 { 678 u_long idx, max_idx; 679 u_int map; 680 u_long len; 681 682 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 683 idx = start / N_INUSEBITS; 684 start %= N_INUSEBITS; 685 map = pmp->pm_inusemap[idx]; 686 map &= ~((1 << start) - 1); 687 if (map) { 688 len = ffs(map) - 1 - start; 689 return (len > count ? count : len); 690 } 691 len = N_INUSEBITS - start; 692 if (len >= count) 693 return (count); 694 while (++idx <= max_idx) { 695 if (len >= count) 696 break; 697 if ((map = pmp->pm_inusemap[idx]) != 0) { 698 len += ffs(map) - 1; 699 break; 700 } 701 len += N_INUSEBITS; 702 } 703 return (len > count ? count : len); 704 } 705 706 /* 707 * Allocate contigous free clusters. 708 * 709 * pmp - mount point. 710 * start - start of cluster chain. 711 * count - number of clusters to allocate. 712 * fillwith - put this value into the fat entry for the 713 * last allocated cluster. 714 * retcluster - put the first allocated cluster's number here. 715 * got - how many clusters were actually allocated. 716 */ 717 int 718 chainalloc(pmp, start, count, fillwith, retcluster, got) 719 struct msdosfsmount *pmp; 720 u_long start; 721 u_long count; 722 u_long fillwith; 723 u_long *retcluster; 724 u_long *got; 725 { 726 int error; 727 u_long cl, n; 728 729 for (cl = start, n = count; n-- > 0;) 730 usemap_alloc(pmp, cl++); 731 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 732 return (error); 733 #ifdef MSDOSFS_DEBUG 734 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 735 start, count); 736 #endif 737 if (retcluster) 738 *retcluster = start; 739 if (got) 740 *got = count; 741 return (0); 742 } 743 744 /* 745 * Allocate contiguous free clusters. 746 * 747 * pmp - mount point. 748 * start - preferred start of cluster chain. 749 * count - number of clusters requested. 750 * fillwith - put this value into the fat entry for the 751 * last allocated cluster. 752 * retcluster - put the first allocated cluster's number here. 753 * got - how many clusters were actually allocated. 754 */ 755 int 756 clusteralloc(pmp, start, count, retcluster, got) 757 struct msdosfsmount *pmp; 758 u_long start; 759 u_long count; 760 u_long *retcluster; 761 u_long *got; 762 { 763 u_long idx; 764 u_long len, newst, foundl, cn, l; 765 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 766 u_long fillwith = CLUST_EOFE; 767 u_int map; 768 769 #ifdef MSDOSFS_DEBUG 770 printf("clusteralloc(): find %lu clusters\n",count); 771 #endif 772 if (start) { 773 if ((len = chainlength(pmp, start, count)) >= count) 774 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 775 } else { 776 /* 777 * This is a new file, initialize start 778 */ 779 struct timeval tv; 780 781 microtime(&tv); 782 start = (tv.tv_usec >> 10) | tv.tv_usec; 783 len = 0; 784 } 785 786 /* 787 * Start at a (pseudo) random place to maximize cluster runs 788 * under multiple writers. 789 */ 790 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 791 foundl = 0; 792 793 for (cn = newst; cn <= pmp->pm_maxcluster;) { 794 idx = cn / N_INUSEBITS; 795 map = pmp->pm_inusemap[idx]; 796 map |= (1 << (cn % N_INUSEBITS)) - 1; 797 if (map != (u_int)-1) { 798 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 799 if ((l = chainlength(pmp, cn, count)) >= count) 800 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 801 if (l > foundl) { 802 foundcn = cn; 803 foundl = l; 804 } 805 cn += l + 1; 806 continue; 807 } 808 cn += N_INUSEBITS - cn % N_INUSEBITS; 809 } 810 for (cn = 0; cn < newst;) { 811 idx = cn / N_INUSEBITS; 812 map = pmp->pm_inusemap[idx]; 813 map |= (1 << (cn % N_INUSEBITS)) - 1; 814 if (map != (u_int)-1) { 815 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 816 if ((l = chainlength(pmp, cn, count)) >= count) 817 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 818 if (l > foundl) { 819 foundcn = cn; 820 foundl = l; 821 } 822 cn += l + 1; 823 continue; 824 } 825 cn += N_INUSEBITS - cn % N_INUSEBITS; 826 } 827 828 if (!foundl) 829 return (ENOSPC); 830 831 if (len) 832 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 833 else 834 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 835 } 836 837 838 /* 839 * Free a chain of clusters. 840 * 841 * pmp - address of the msdosfs mount structure for the filesystem 842 * containing the cluster chain to be freed. 843 * startcluster - number of the 1st cluster in the chain of clusters to be 844 * freed. 845 */ 846 int 847 freeclusterchain(pmp, cluster) 848 struct msdosfsmount *pmp; 849 u_long cluster; 850 { 851 int error; 852 struct buf *bp = NULL; 853 u_long bn, bo, bsize, byteoffset; 854 u_long readcn, lbn = -1; 855 856 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 857 byteoffset = FATOFS(pmp, cluster); 858 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 859 if (lbn != bn) { 860 if (bp) 861 updatefats(pmp, bp, lbn); 862 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 863 if (error) { 864 brelse(bp); 865 return (error); 866 } 867 lbn = bn; 868 } 869 usemap_free(pmp, cluster); 870 switch (pmp->pm_fatmask) { 871 case FAT12_MASK: 872 readcn = getushort(&bp->b_data[bo]); 873 if (cluster & 1) { 874 cluster = readcn >> 4; 875 readcn &= 0x000f; 876 readcn |= MSDOSFSFREE << 4; 877 } else { 878 cluster = readcn; 879 readcn &= 0xf000; 880 readcn |= MSDOSFSFREE & 0xfff; 881 } 882 putushort(&bp->b_data[bo], readcn); 883 break; 884 case FAT16_MASK: 885 cluster = getushort(&bp->b_data[bo]); 886 putushort(&bp->b_data[bo], MSDOSFSFREE); 887 break; 888 case FAT32_MASK: 889 cluster = getulong(&bp->b_data[bo]); 890 putulong(&bp->b_data[bo], 891 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 892 break; 893 } 894 cluster &= pmp->pm_fatmask; 895 } 896 if (bp) 897 updatefats(pmp, bp, bn); 898 return (0); 899 } 900 901 /* 902 * Read in fat blocks looking for free clusters. For every free cluster 903 * found turn off its corresponding bit in the pm_inusemap. 904 */ 905 int 906 fillinusemap(pmp) 907 struct msdosfsmount *pmp; 908 { 909 struct buf *bp = NULL; 910 u_long cn, readcn; 911 int error; 912 u_long bn, bo, bsize, byteoffset; 913 914 /* 915 * Mark all clusters in use, we mark the free ones in the fat scan 916 * loop further down. 917 */ 918 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 919 pmp->pm_inusemap[cn] = (u_int)-1; 920 921 /* 922 * Figure how many free clusters are in the filesystem by ripping 923 * through the fat counting the number of entries whose content is 924 * zero. These represent free clusters. 925 */ 926 pmp->pm_freeclustercount = 0; 927 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 928 byteoffset = FATOFS(pmp, cn); 929 bo = byteoffset % pmp->pm_fatblocksize; 930 if (!bo || !bp) { 931 /* Read new FAT block */ 932 if (bp) 933 brelse(bp); 934 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 935 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 936 if (error) { 937 brelse(bp); 938 return (error); 939 } 940 } 941 if (FAT32(pmp)) 942 readcn = getulong(&bp->b_data[bo]); 943 else 944 readcn = getushort(&bp->b_data[bo]); 945 if (FAT12(pmp) && (cn & 1)) 946 readcn >>= 4; 947 readcn &= pmp->pm_fatmask; 948 949 if (readcn == 0) 950 usemap_free(pmp, cn); 951 } 952 brelse(bp); 953 return (0); 954 } 955 956 /* 957 * Allocate a new cluster and chain it onto the end of the file. 958 * 959 * dep - the file to extend 960 * count - number of clusters to allocate 961 * bpp - where to return the address of the buf header for the first new 962 * file block 963 * ncp - where to put cluster number of the first newly allocated cluster 964 * If this pointer is 0, do not return the cluster number. 965 * flags - see fat.h 966 * 967 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 968 * the de_flag field of the denode and it does not change the de_FileSize 969 * field. This is left for the caller to do. 970 */ 971 972 int 973 extendfile(dep, count, bpp, ncp, flags) 974 struct denode *dep; 975 u_long count; 976 struct buf **bpp; 977 u_long *ncp; 978 int flags; 979 { 980 int error; 981 u_long frcn = 0, cn, got; 982 struct msdosfsmount *pmp = dep->de_pmp; 983 struct buf *bp; 984 985 /* 986 * Don't try to extend the root directory 987 */ 988 if (dep->de_StartCluster == MSDOSFSROOT 989 && (dep->de_Attributes & ATTR_DIRECTORY)) { 990 printf("extendfile(): attempt to extend root directory\n"); 991 return (ENOSPC); 992 } 993 994 /* 995 * If the "file's last cluster" cache entry is empty, and the file 996 * is not empty, then fill the cache entry by calling pcbmap(). 997 */ 998 fc_fileextends++; 999 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1000 dep->de_StartCluster != 0) { 1001 fc_lfcempty++; 1002 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 1003 /* we expect it to return E2BIG */ 1004 if (error != E2BIG) 1005 return (error); 1006 } 1007 1008 while (count > 0) { 1009 1010 /* 1011 * Allocate a new cluster chain and cat onto the end of the 1012 * file. If the file is empty we make de_StartCluster point 1013 * to the new block. Note that de_StartCluster being 0 is 1014 * sufficient to be sure the file is empty since we exclude 1015 * attempts to extend the root directory above, and the root 1016 * dir is the only file with a startcluster of 0 that has 1017 * blocks allocated (sort of). 1018 */ 1019 1020 if (dep->de_StartCluster == 0) 1021 cn = 0; 1022 else 1023 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1024 error = clusteralloc(pmp, cn, count, &cn, &got); 1025 if (error) 1026 return (error); 1027 1028 count -= got; 1029 1030 /* 1031 * Give them the filesystem relative cluster number if they want 1032 * it. 1033 */ 1034 if (ncp) { 1035 *ncp = cn; 1036 ncp = NULL; 1037 } 1038 1039 if (dep->de_StartCluster == 0) { 1040 dep->de_StartCluster = cn; 1041 frcn = 0; 1042 } else { 1043 error = fatentry(FAT_SET, pmp, 1044 dep->de_fc[FC_LASTFC].fc_fsrcn, 1045 0, cn); 1046 if (error) { 1047 clusterfree(pmp, cn, NULL); 1048 return (error); 1049 } 1050 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1051 } 1052 1053 /* 1054 * Update the "last cluster of the file" entry in the 1055 * denode's fat cache. 1056 */ 1057 1058 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1059 if ((flags & DE_CLEAR) && 1060 (dep->de_Attributes & ATTR_DIRECTORY)) { 1061 while (got-- > 0) { 1062 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1063 pmp->pm_bpcluster, 0, 0); 1064 clrbuf(bp); 1065 if (bpp) { 1066 *bpp = bp; 1067 bpp = NULL; 1068 } else { 1069 bdwrite(bp); 1070 } 1071 } 1072 } 1073 } 1074 1075 return (0); 1076 } 1077