msdosfs_fat.c revision 33181
1/* $Id: msdosfs_fat.c,v 1.15 1998/02/06 12:13:46 eivind Exp $ */ 2/* $NetBSD: msdosfs_fat.c,v 1.12 1994/08/21 18:44:04 ws Exp $ */ 3 4/*- 5 * Copyright (C) 1994 Wolfgang Solfrank. 6 * Copyright (C) 1994 TooLs GmbH. 7 * All rights reserved. 8 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by TooLs GmbH. 21 * 4. The name of TooLs GmbH may not be used to endorse or promote products 22 * derived from this software without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR 25 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 26 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 27 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 29 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 30 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 31 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 32 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 33 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34 */ 35/* 36 * Written by Paul Popelka (paulp@uts.amdahl.com) 37 * 38 * You can do anything you want with this software, just don't say you wrote 39 * it, and don't remove this notice. 40 * 41 * This software is provided "as is". 42 * 43 * The author supplies this software to be publicly redistributed on the 44 * understanding that the author is not responsible for the correct 45 * functioning of this software in any circumstances and is not liable for 46 * any damages caused by this software. 47 * 48 * October 1992 49 */ 50 51/* 52 * kernel include files. 53 */ 54#include <sys/param.h> 55#include <sys/systm.h> 56#include <sys/buf.h> 57#include <sys/mount.h> /* to define statfs structure */ 58#include <sys/vnode.h> /* to define vattr structure */ 59 60/* 61 * msdosfs include files. 62 */ 63#include <msdosfs/bpb.h> 64#include <msdosfs/msdosfsmount.h> 65#include <msdosfs/direntry.h> 66#include <msdosfs/denode.h> 67#include <msdosfs/fat.h> 68 69/* 70 * Fat cache stats. 71 */ 72static int fc_fileextends; /* # of file extends */ 73static int fc_lfcempty; /* # of time last file cluster cache entry 74 * was empty */ 75static int fc_bmapcalls; /* # of times pcbmap was called */ 76 77#define LMMAX 20 78static int fc_lmdistance[LMMAX];/* counters for how far off the last 79 * cluster mapped entry was. */ 80static int fc_largedistance; /* off by more than LMMAX */ 81 82/* Byte offset in FAT on filesystem pmp, cluster cn */ 83#define FATOFS(pmp, cn) (FAT12(pmp) ? (cn) * 3 / 2 : (cn) * 2) 84 85static int chainalloc __P((struct msdosfsmount *pmp, u_long start, 86 u_long count, u_long fillwith, 87 u_long *retcluster, u_long *got)); 88static int chainlength __P((struct msdosfsmount *pmp, u_long start, 89 u_long count)); 90static void fatblock __P((struct msdosfsmount *pmp, u_long ofs, 91 u_long *bnp, u_long *sizep, u_long *bop)); 92static int fatchain __P((struct msdosfsmount *pmp, u_long start, 93 u_long count, u_long fillwith)); 94static void fc_lookup __P((struct denode *dep, u_long findcn, 95 u_long *frcnp, u_long *fsrcnp)); 96static void updatefats __P((struct msdosfsmount *pmp, struct buf *bp, 97 u_long fatbn)); 98static void usemap_alloc __P((struct msdosfsmount *pmp, u_long cn)); 99static void usemap_free __P((struct msdosfsmount *pmp, u_long cn)); 100 101static void 102fatblock(pmp, ofs, bnp, sizep, bop) 103 struct msdosfsmount *pmp; 104 u_long ofs; 105 u_long *bnp; 106 u_long *sizep; 107 u_long *bop; 108{ 109 u_long bn, size; 110 111 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 112 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 113 * pmp->pm_BytesPerSec; 114 bn += pmp->pm_fatblk; 115 if (bnp) 116 *bnp = bn; 117 if (sizep) 118 *sizep = size; 119 if (bop) 120 *bop = ofs % pmp->pm_fatblocksize; 121} 122 123/* 124 * Map the logical cluster number of a file into a physical disk sector 125 * that is filesystem relative. 126 * 127 * dep - address of denode representing the file of interest 128 * findcn - file relative cluster whose filesystem relative cluster number 129 * and/or block number are/is to be found 130 * bnp - address of where to place the file system relative block number. 131 * If this pointer is null then don't return this quantity. 132 * cnp - address of where to place the file system relative cluster number. 133 * If this pointer is null then don't return this quantity. 134 * 135 * NOTE: Either bnp or cnp must be non-null. 136 * This function has one side effect. If the requested file relative cluster 137 * is beyond the end of file, then the actual number of clusters in the file 138 * is returned in *cnp. This is useful for determining how long a directory is. 139 * If cnp is null, nothing is returned. 140 */ 141int 142pcbmap(dep, findcn, bnp, cnp) 143 struct denode *dep; 144 u_long findcn; /* file relative cluster to get */ 145 daddr_t *bnp; /* returned filesys relative blk number */ 146 u_long *cnp; /* returned cluster number */ 147{ 148 int error; 149 u_long i; 150 u_long cn; 151 u_long prevcn; 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 int fat12 = FAT12(pmp); /* 12 bit fat */ 160 161 fc_bmapcalls++; 162 163 /* 164 * If they don't give us someplace to return a value then don't 165 * bother doing anything. 166 */ 167 if (bnp == NULL && cnp == NULL) 168 return 0; 169 170 cn = dep->de_StartCluster; 171 /* 172 * The "file" that makes up the root directory is contiguous, 173 * permanently allocated, of fixed size, and is not made up of 174 * clusters. If the cluster number is beyond the end of the root 175 * directory, then return the number of clusters in the file. 176 */ 177 if (cn == MSDOSFSROOT) { 178 if (dep->de_Attributes & ATTR_DIRECTORY) { 179 if (findcn * pmp->pm_SectPerClust >= pmp->pm_rootdirsize) { 180 if (cnp) 181 *cnp = pmp->pm_rootdirsize / pmp->pm_SectPerClust; 182 return E2BIG; 183 } 184 if (bnp) 185 *bnp = pmp->pm_rootdirblk + (findcn * pmp->pm_SectPerClust); 186 if (cnp) 187 *cnp = MSDOSFSROOT; 188 return 0; 189 } else { /* just an empty file */ 190 if (cnp) 191 *cnp = 0; 192 return E2BIG; 193 } 194 } 195 196 /* 197 * Rummage around in the fat cache, maybe we can avoid tromping 198 * thru every fat entry for the file. And, keep track of how far 199 * off the cache was from where we wanted to be. 200 */ 201 i = 0; 202 fc_lookup(dep, findcn, &i, &cn); 203 if ((bn = findcn - i) >= LMMAX) 204 fc_largedistance++; 205 else 206 fc_lmdistance[bn]++; 207 208 /* 209 * Handle all other files or directories the normal way. 210 */ 211 prevcn = 0; 212 for (; i < findcn; i++) { 213 if (MSDOSFSEOF(cn)) 214 goto hiteof; 215 byteoffset = FATOFS(pmp, cn); 216 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 217 if (bn != bp_bn) { 218 if (bp) 219 brelse(bp); 220 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 221 if (error) 222 return error; 223 bp_bn = bn; 224 } 225 prevcn = cn; 226 cn = getushort(&bp->b_data[bo]); 227 if (fat12) { 228 if (prevcn & 1) 229 cn >>= 4; 230 cn &= 0x0fff; 231 /* 232 * Force the special cluster numbers in the range 233 * 0x0ff0-0x0fff to be the same as for 16 bit 234 * cluster numbers to let the rest of msdosfs think 235 * it is always dealing with 16 bit fats. 236 */ 237 if ((cn & 0x0ff0) == 0x0ff0) 238 cn |= 0xf000; 239 } 240 } 241 242 if (!MSDOSFSEOF(cn)) { 243 if (bp) 244 brelse(bp); 245 if (bnp) 246 *bnp = cntobn(pmp, cn); 247 if (cnp) 248 *cnp = cn; 249 fc_setcache(dep, FC_LASTMAP, i, cn); 250 return 0; 251 } 252 253hiteof:; 254 if (cnp) 255 *cnp = i; 256 if (bp) 257 brelse(bp); 258 /* update last file cluster entry in the fat cache */ 259 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 260 return E2BIG; 261} 262 263/* 264 * Find the closest entry in the fat cache to the cluster we are looking 265 * for. 266 */ 267static void 268fc_lookup(dep, findcn, frcnp, fsrcnp) 269 struct denode *dep; 270 u_long findcn; 271 u_long *frcnp; 272 u_long *fsrcnp; 273{ 274 int i; 275 u_long cn; 276 struct fatcache *closest = 0; 277 278 for (i = 0; i < FC_SIZE; i++) { 279 cn = dep->de_fc[i].fc_frcn; 280 if (cn != FCE_EMPTY && cn <= findcn) { 281 if (closest == 0 || cn > closest->fc_frcn) 282 closest = &dep->de_fc[i]; 283 } 284 } 285 if (closest) { 286 *frcnp = closest->fc_frcn; 287 *fsrcnp = closest->fc_fsrcn; 288 } 289} 290 291/* 292 * Purge the fat cache in denode dep of all entries relating to file 293 * relative cluster frcn and beyond. 294 */ 295void fc_purge(dep, frcn) 296 struct denode *dep; 297 u_int frcn; 298{ 299 int i; 300 struct fatcache *fcp; 301 302 fcp = dep->de_fc; 303 for (i = 0; i < FC_SIZE; i++, fcp++) { 304 if (fcp->fc_frcn >= frcn) 305 fcp->fc_frcn = FCE_EMPTY; 306 } 307} 308 309/* 310 * Update all copies of the fat. The first copy is updated last. 311 * 312 * pmp - msdosfsmount structure for filesystem to update 313 * bp - addr of modified fat block 314 * fatbn - block number relative to begin of filesystem of the modified fat block. 315 */ 316static void 317updatefats(pmp, bp, fatbn) 318 struct msdosfsmount *pmp; 319 struct buf *bp; 320 u_long fatbn; 321{ 322 int i; 323 struct buf *bpn; 324 325#ifdef MSDOSFS_DEBUG 326 printf("updatefats(pmp %p, bp %p, fatbn %ld)\n", pmp, bp, fatbn); 327#endif 328 329 /* 330 * Now copy the block(s) of the modified fat to the other copies of 331 * the fat and write them out. This is faster than reading in the 332 * other fats and then writing them back out. This could tie up 333 * the fat for quite a while. Preventing others from accessing it. 334 * To prevent us from going after the fat quite so much we use 335 * delayed writes, unless they specfied "synchronous" when the 336 * filesystem was mounted. If synch is asked for then use 337 * bwrite()'s and really slow things down. 338 */ 339 for (i = 1; i < pmp->pm_FATs; i++) { 340 fatbn += pmp->pm_FATsecs; 341 /* getblk() never fails */ 342 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 343 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 344 if (pmp->pm_waitonfat) 345 bwrite(bpn); 346 else 347 bdwrite(bpn); 348 } 349 /* 350 * Write out the first fat last. 351 */ 352 if (pmp->pm_waitonfat) 353 bwrite(bp); 354 else 355 bdwrite(bp); 356} 357 358/* 359 * Updating entries in 12 bit fats is a pain in the butt. 360 * 361 * The following picture shows where nibbles go when moving from a 12 bit 362 * cluster number into the appropriate bytes in the FAT. 363 * 364 * byte m byte m+1 byte m+2 365 * +----+----+ +----+----+ +----+----+ 366 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 367 * +----+----+ +----+----+ +----+----+ 368 * 369 * +----+----+----+ +----+----+----+ 370 * | 3 0 1 | | 4 5 2 | 371 * +----+----+----+ +----+----+----+ 372 * cluster n cluster n+1 373 * 374 * Where n is even. m = n + (n >> 2) 375 * 376 */ 377static inline void 378usemap_alloc(pmp, cn) 379 struct msdosfsmount *pmp; 380 u_long cn; 381{ 382 pmp->pm_inusemap[cn / N_INUSEBITS] 383 |= 1 << (cn % N_INUSEBITS); 384 pmp->pm_freeclustercount--; 385} 386 387static inline void 388usemap_free(pmp, cn) 389 struct msdosfsmount *pmp; 390 u_long cn; 391{ 392 pmp->pm_freeclustercount++; 393 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 394} 395 396int 397clusterfree(pmp, cluster, oldcnp) 398 struct msdosfsmount *pmp; 399 u_long cluster; 400 u_long *oldcnp; 401{ 402 int error; 403 u_long oldcn; 404 405 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 406 if (error == 0) { 407 /* 408 * If the cluster was successfully marked free, then update 409 * the count of free clusters, and turn off the "allocated" 410 * bit in the "in use" cluster bit map. 411 */ 412 usemap_free(pmp, cluster); 413 if (oldcnp) 414 *oldcnp = oldcn; 415 } 416 return error; 417} 418 419/* 420 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 421 * 422 * function - whether to get or set a fat entry 423 * pmp - address of the msdosfsmount structure for the filesystem 424 * whose fat is to be manipulated. 425 * cn - which cluster is of interest 426 * oldcontents - address of a word that is to receive the contents of the 427 * cluster'th entry if this is a get function 428 * newcontents - the new value to be written into the cluster'th element of 429 * the fat if this is a set function. 430 * 431 * This function can also be used to free a cluster by setting the fat entry 432 * for a cluster to 0. 433 * 434 * All copies of the fat are updated if this is a set function. NOTE: If 435 * fatentry() marks a cluster as free it does not update the inusemap in 436 * the msdosfsmount structure. This is left to the caller. 437 */ 438int 439fatentry(function, pmp, cn, oldcontents, newcontents) 440 int function; 441 struct msdosfsmount *pmp; 442 u_long cn; 443 u_long *oldcontents; 444 u_long newcontents; 445{ 446 int error; 447 u_long readcn; 448 u_long bn, bo, bsize, byteoffset; 449 struct buf *bp; 450 451 /* 452 * printf("fatentry(func %d, pmp %08x, clust %d, oldcon %08x, newcon %d)\n", 453 * function, pmp, cluster, oldcontents, newcontents); 454 */ 455 456#ifdef DIAGNOSTIC 457 /* 458 * Be sure they asked us to do something. 459 */ 460 if ((function & (FAT_SET | FAT_GET)) == 0) { 461 printf("fatentry(): function code doesn't specify get or set\n"); 462 return EINVAL; 463 } 464 465 /* 466 * If they asked us to return a cluster number but didn't tell us 467 * where to put it, give them an error. 468 */ 469 if ((function & FAT_GET) && oldcontents == NULL) { 470 printf("fatentry(): get function with no place to put result\n"); 471 return EINVAL; 472 } 473#endif 474 475 /* 476 * Be sure the requested cluster is in the filesystem. 477 */ 478 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 479 return EINVAL; 480 481 byteoffset = FATOFS(pmp, cn); 482 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 483 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 484 if (error) 485 return error; 486 487 if (function & FAT_GET) { 488 readcn = getushort(&bp->b_data[bo]); 489 if (FAT12(pmp)) { 490 if (cn & 1) 491 readcn >>= 4; 492 readcn &= 0x0fff; 493 /* map certain 12 bit fat entries to 16 bit */ 494 if ((readcn & 0x0ff0) == 0x0ff0) 495 readcn |= 0xf000; 496 } 497 *oldcontents = readcn; 498 } 499 if (function & FAT_SET) { 500 if (FAT12(pmp)) { 501 readcn = getushort(&bp->b_data[bo]); 502 if (cn & 1) { 503 readcn &= 0x000f; 504 readcn |= newcontents << 4; 505 } else { 506 readcn &= 0xf000; 507 readcn |= newcontents & 0xfff; 508 } 509 putushort(&bp->b_data[bo], readcn); 510 } else 511 putushort(&bp->b_data[bo], newcontents); 512 updatefats(pmp, bp, bn); 513 bp = NULL; 514 pmp->pm_fmod = 1; 515 } 516 if (bp) 517 brelse(bp); 518 return 0; 519} 520 521/* 522 * Update a contiguous cluster chain 523 * 524 * pmp - mount point 525 * start - first cluster of chain 526 * count - number of clusters in chain 527 * fillwith - what to write into fat entry of last cluster 528 */ 529static int 530fatchain(pmp, start, count, fillwith) 531 struct msdosfsmount *pmp; 532 u_long start; 533 u_long count; 534 u_long fillwith; 535{ 536 int error; 537 u_long bn, bo, bsize, byteoffset, readcn, newc; 538 struct buf *bp; 539 540#ifdef MSDOSFS_DEBUG 541 printf("fatchain(pmp %p, start %ld, count %ld, fillwith %ld)\n", 542 pmp, start, count, fillwith); 543#endif 544 /* 545 * Be sure the clusters are in the filesystem. 546 */ 547 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 548 return EINVAL; 549 550 while (count > 0) { 551 byteoffset = FATOFS(pmp, start); 552 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 553 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 554 if (error) 555 return error; 556 while (count > 0) { 557 start++; 558 newc = --count > 0 ? start : fillwith; 559 if (FAT12(pmp)) { 560 readcn = getushort(&bp->b_data[bo]); 561 if (start & 1) { 562 readcn &= 0xf000; 563 readcn |= newc & 0xfff; 564 } else { 565 readcn &= 0x000f; 566 readcn |= newc << 4; 567 } 568 putushort(&bp->b_data[bo], readcn); 569 bo++; 570 if (!(start & 1)) 571 bo++; 572 } else { 573 putushort(&bp->b_data[bo], newc); 574 bo += 2; 575 } 576 if (bo >= bsize) 577 break; 578 } 579 updatefats(pmp, bp, bn); 580 } 581 pmp->pm_fmod = 1; 582 return 0; 583} 584 585/* 586 * Check the length of a free cluster chain starting at start. 587 * 588 * pmp - mount point 589 * start - start of chain 590 * count - maximum interesting length 591 */ 592static int 593chainlength(pmp, start, count) 594 struct msdosfsmount *pmp; 595 u_long start; 596 u_long count; 597{ 598 u_long idx, max_idx; 599 u_int map; 600 u_long len; 601 602 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 603 idx = start / N_INUSEBITS; 604 start %= N_INUSEBITS; 605 map = pmp->pm_inusemap[idx]; 606 map &= ~((1 << start) - 1); 607 if (map) { 608 len = ffs(map) - 1 - start; 609 return len > count ? count : len; 610 } 611 len = N_INUSEBITS - start; 612 if (len >= count) 613 return count; 614 while (++idx <= max_idx) { 615 if (len >= count) 616 break; 617 map = pmp->pm_inusemap[idx]; 618 if (map) { 619 len += ffs(map) - 1; 620 break; 621 } 622 len += N_INUSEBITS; 623 } 624 return len > count ? count : len; 625} 626 627/* 628 * Allocate contigous free clusters. 629 * 630 * pmp - mount point. 631 * start - start of cluster chain. 632 * count - number of clusters to allocate. 633 * fillwith - put this value into the fat entry for the 634 * last allocated cluster. 635 * retcluster - put the first allocated cluster's number here. 636 * got - how many clusters were actually allocated. 637 */ 638static int 639chainalloc(pmp, start, count, fillwith, retcluster, got) 640 struct msdosfsmount *pmp; 641 u_long start; 642 u_long count; 643 u_long fillwith; 644 u_long *retcluster; 645 u_long *got; 646{ 647 int error; 648 649 error = fatchain(pmp, start, count, fillwith); 650 if (error == 0) { 651#ifdef MSDOSFS_DEBUG 652 printf("clusteralloc(): allocated cluster chain at %ld (%ld clusters)\n", 653 start, count); 654#endif 655 if (retcluster) 656 *retcluster = start; 657 if (got) 658 *got = count; 659 while (count-- > 0) 660 usemap_alloc(pmp, start++); 661 } 662 return error; 663} 664 665/* 666 * Allocate contiguous free clusters. 667 * 668 * pmp - mount point. 669 * start - preferred start of cluster chain. 670 * count - number of clusters requested. 671 * fillwith - put this value into the fat entry for the 672 * last allocated cluster. 673 * retcluster - put the first allocated cluster's number here. 674 * got - how many clusters were actually allocated. 675 */ 676int 677clusteralloc(pmp, start, count, fillwith, retcluster, got) 678 struct msdosfsmount *pmp; 679 u_long start; 680 u_long count; 681 u_long fillwith; 682 u_long *retcluster; 683 u_long *got; 684{ 685 u_long idx; 686 u_long len, newst, foundcn, foundl, cn, l; 687 u_int map; 688 689#ifdef MSDOSFS_DEBUG 690 printf("clusteralloc(): find %d clusters\n",count); 691#endif 692 if (start) { 693 if ((len = chainlength(pmp, start, count)) >= count) 694 return chainalloc(pmp, start, count, fillwith, retcluster, got); 695 } else { 696 /* 697 * This is a new file, initialize start 698 */ 699 struct timeval tv; 700 701 microtime(&tv); 702 start = (tv.tv_usec >> 10)|tv.tv_usec; 703 len = 0; 704 } 705 706 /* 707 * Start at a (pseudo) random place to maximize cluster runs 708 * under multiple writers. 709 */ 710 foundcn = newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 711 foundl = 0; 712 713 for (cn = newst; cn <= pmp->pm_maxcluster;) { 714 idx = cn / N_INUSEBITS; 715 map = pmp->pm_inusemap[idx]; 716 map |= (1 << (cn % N_INUSEBITS)) - 1; 717 if (map != (u_int)-1) { 718 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 719 if ((l = chainlength(pmp, cn, count)) >= count) 720 return chainalloc(pmp, cn, count, fillwith, retcluster, got); 721 if (l > foundl) { 722 foundcn = cn; 723 foundl = l; 724 } 725 cn += l + 1; 726 continue; 727 } 728 cn += N_INUSEBITS - cn % N_INUSEBITS; 729 } 730 for (cn = 0; cn < newst;) { 731 idx = cn / N_INUSEBITS; 732 map = pmp->pm_inusemap[idx]; 733 map |= (1 << (cn % N_INUSEBITS)) - 1; 734 if (map != (u_int)-1) { 735 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 736 if ((l = chainlength(pmp, cn, count)) >= count) 737 return chainalloc(pmp, cn, count, fillwith, retcluster, got); 738 if (l > foundl) { 739 foundcn = cn; 740 foundl = l; 741 } 742 cn += l + 1; 743 continue; 744 } 745 cn += N_INUSEBITS - cn % N_INUSEBITS; 746 } 747 748 if (!foundl) 749 return ENOSPC; 750 751 if (len) 752 return chainalloc(pmp, start, len, fillwith, retcluster, got); 753 else 754 return chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got); 755} 756 757 758/* 759 * Free a chain of clusters. 760 * 761 * pmp - address of the msdosfs mount structure for the filesystem 762 * containing the cluster chain to be freed. 763 * startcluster - number of the 1st cluster in the chain of clusters to be 764 * freed. 765 */ 766int 767freeclusterchain(pmp, cluster) 768 struct msdosfsmount *pmp; 769 u_long cluster; 770{ 771 int error = 0; 772 struct buf *bp = NULL; 773 u_long bn, bo, bsize, byteoffset; 774 u_long readcn, lbn = -1; 775 776 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 777 byteoffset = FATOFS(pmp, cluster); 778 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 779 if (lbn != bn) { 780 if (bp) 781 updatefats(pmp, bp, lbn); 782 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 783 if (error) 784 return error; 785 lbn = bn; 786 } 787 usemap_free(pmp, cluster); 788 readcn = getushort(&bp->b_data[bo]); 789 if (FAT12(pmp)) { 790 if (cluster & 1) { 791 cluster = readcn >> 4; 792 readcn &= 0x000f; 793 readcn |= MSDOSFSFREE << 4; 794 } else { 795 cluster = readcn; 796 readcn &= 0xf000; 797 readcn |= MSDOSFSFREE & 0xfff; 798 } 799 putushort(&bp->b_data[bo], readcn); 800 cluster &= 0x0fff; 801 if ((cluster&0x0ff0) == 0x0ff0) 802 cluster |= 0xf000; 803 } else { 804 cluster = readcn; 805 putushort(&bp->b_data[bo], MSDOSFSFREE); 806 } 807 } 808 if (bp) 809 updatefats(pmp, bp, bn); 810 return error; 811} 812 813/* 814 * Read in fat blocks looking for free clusters. For every free cluster 815 * found turn off its corresponding bit in the pm_inusemap. 816 */ 817int 818fillinusemap(pmp) 819 struct msdosfsmount *pmp; 820{ 821 struct buf *bp = NULL; 822 u_long cn, readcn; 823 int error; 824 int fat12 = FAT12(pmp); 825 u_long bn, bo, bsize, byteoffset; 826 827 /* 828 * Mark all clusters in use, we mark the free ones in the fat scan 829 * loop further down. 830 */ 831 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 832 pmp->pm_inusemap[cn] = (u_int)-1; 833 834 /* 835 * Figure how many free clusters are in the filesystem by ripping 836 * through the fat counting the number of entries whose content is 837 * zero. These represent free clusters. 838 */ 839 pmp->pm_freeclustercount = 0; 840 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 841 byteoffset = FATOFS(pmp, cn); 842 bo = byteoffset % pmp->pm_fatblocksize; 843 if (!bo || !bp) { 844 /* Read new FAT block */ 845 if (bp) 846 brelse(bp); 847 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 848 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 849 if (error) 850 return error; 851 } 852 readcn = getushort(&bp->b_data[bo]); 853 if (fat12) { 854 if (cn & 1) 855 readcn >>= 4; 856 readcn &= 0x0fff; 857 } 858 859 if (readcn == 0) 860 usemap_free(pmp, cn); 861 } 862 brelse(bp); 863 return 0; 864} 865 866/* 867 * Allocate a new cluster and chain it onto the end of the file. 868 * 869 * dep - the file to extend 870 * count - number of clusters to allocate 871 * bpp - where to return the address of the buf header for the first new 872 * file block 873 * ncp - where to put cluster number of the first newly allocated cluster 874 * If this pointer is 0, do not return the cluster number. 875 * flags - see fat.h 876 * 877 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 878 * the de_flag field of the denode and it does not change the de_FileSize 879 * field. This is left for the caller to do. 880 */ 881int 882extendfile(dep, count, bpp, ncp, flags) 883 struct denode *dep; 884 u_long count; 885 struct buf **bpp; 886 u_long *ncp; 887 int flags; 888{ 889 int error = 0; 890 u_long frcn; 891 u_long cn, got; 892 struct msdosfsmount *pmp = dep->de_pmp; 893 struct buf *bp; 894 895 /* 896 * Don't try to extend the root directory 897 */ 898 if (DETOV(dep)->v_flag & VROOT) { 899 printf("extendfile(): attempt to extend root directory\n"); 900 return ENOSPC; 901 } 902 903 /* 904 * If the "file's last cluster" cache entry is empty, and the file 905 * is not empty, then fill the cache entry by calling pcbmap(). 906 */ 907 fc_fileextends++; 908 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 909 dep->de_StartCluster != 0) { 910 fc_lfcempty++; 911 error = pcbmap(dep, 0xffff, 0, &cn); 912 /* we expect it to return E2BIG */ 913 if (error != E2BIG) 914 return error; 915 error = 0; 916 } 917 918 while (count > 0) { 919 /* 920 * Allocate a new cluster chain and cat onto the end of the file. 921 * If the file is empty we make de_StartCluster point to the new 922 * block. Note that de_StartCluster being 0 is sufficient to be 923 * sure the file is empty since we exclude attempts to extend the 924 * root directory above, and the root dir is the only file with a 925 * startcluster of 0 that has blocks allocated (sort of). 926 */ 927 if (dep->de_StartCluster == 0) 928 cn = 0; 929 else 930 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 931 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 932 if (error) 933 return error; 934 935 count -= got; 936 937 /* 938 * Give them the filesystem relative cluster number if they want 939 * it. 940 */ 941 if (ncp) { 942 *ncp = cn; 943 ncp = NULL; 944 } 945 946 if (dep->de_StartCluster == 0) { 947 dep->de_StartCluster = cn; 948 frcn = 0; 949 } else { 950 error = fatentry(FAT_SET, pmp, dep->de_fc[FC_LASTFC].fc_fsrcn, 951 0, cn); 952 if (error) { 953 clusterfree(pmp, cn, NULL); 954 return error; 955 } 956 957 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 958 } 959 960 /* 961 * Update the "last cluster of the file" entry in the denode's fat 962 * cache. 963 */ 964 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 965 966 if (flags & DE_CLEAR) { 967 while (got-- > 0) { 968 /* 969 * Get the buf header for the new block of the file. 970 */ 971 if (dep->de_Attributes & ATTR_DIRECTORY) 972 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 973 pmp->pm_bpcluster, 0, 0); 974 else { 975 bp = getblk(DETOV(dep), frcn++, pmp->pm_bpcluster, 0, 0); 976 /* 977 * Do the bmap now, as in msdosfs_write 978 */ 979 if (pcbmap(dep, bp->b_lblkno, &bp->b_blkno, 0)) 980 bp->b_blkno = -1; 981 if (bp->b_blkno == -1) 982 panic("extendfile: pcbmap"); 983 } 984 clrbuf(bp); 985 if (bpp) { 986 *bpp = bp; 987 bpp = NULL; 988 } else { 989 bp->b_flags |= B_AGE; 990 bawrite(bp); 991 } 992 } 993 } 994 } 995 996 return 0; 997} 998