1 /* $Id: msdosfs_fat.c,v 1.4 1994/12/12 12:35:45 bde 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/file.h> 58 #include <sys/namei.h> 59 #include <sys/mount.h> /* to define statfs structure */ 60 #include <sys/vnode.h> /* to define vattr structure */ 61 #include <sys/errno.h> 62 63 /* 64 * msdosfs include files. 65 */ 66 #include <msdosfs/bpb.h> 67 #include <msdosfs/msdosfsmount.h> 68 #include <msdosfs/direntry.h> 69 #include <msdosfs/denode.h> 70 #include <msdosfs/fat.h> 71 72 /* 73 * Fat cache stats. 74 */ 75 int fc_fileextends; /* # of file extends */ 76 int fc_lfcempty; /* # of time last file cluster cache entry 77 * was empty */ 78 int fc_bmapcalls; /* # of times pcbmap was called */ 79 80 #define LMMAX 20 81 int fc_lmdistance[LMMAX]; /* counters for how far off the last 82 * cluster mapped entry was. */ 83 int fc_largedistance; /* off by more than LMMAX */ 84 85 /* Byte offset in FAT on filesystem pmp, cluster cn */ 86 #define FATOFS(pmp, cn) (FAT12(pmp) ? (cn) * 3 / 2 : (cn) * 2) 87 88 static void 89 fatblock(pmp, ofs, bnp, sizep, bop) 90 struct msdosfsmount *pmp; 91 u_long ofs; 92 u_long *bnp; 93 u_long *sizep; 94 u_long *bop; 95 { 96 u_long bn, size; 97 98 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 99 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 100 * pmp->pm_BytesPerSec; 101 bn += pmp->pm_fatblk; 102 if (bnp) 103 *bnp = bn; 104 if (sizep) 105 *sizep = size; 106 if (bop) 107 *bop = ofs % pmp->pm_fatblocksize; 108 } 109 110 /* 111 * Map the logical cluster number of a file into a physical disk sector 112 * that is filesystem relative. 113 * 114 * dep - address of denode representing the file of interest 115 * findcn - file relative cluster whose filesystem relative cluster number 116 * and/or block number are/is to be found 117 * bnp - address of where to place the file system relative block number. 118 * If this pointer is null then don't return this quantity. 119 * cnp - address of where to place the file system relative cluster number. 120 * If this pointer is null then don't return this quantity. 121 * 122 * NOTE: Either bnp or cnp must be non-null. 123 * This function has one side effect. If the requested file relative cluster 124 * is beyond the end of file, then the actual number of clusters in the file 125 * is returned in *cnp. This is useful for determining how long a directory is. 126 * If cnp is null, nothing is returned. 127 */ 128 int 129 pcbmap(dep, findcn, bnp, cnp) 130 struct denode *dep; 131 u_long findcn; /* file relative cluster to get */ 132 daddr_t *bnp; /* returned filesys relative blk number */ 133 u_long *cnp; /* returned cluster number */ 134 { 135 int error; 136 u_long i; 137 u_long cn; 138 u_long prevcn; 139 u_long byteoffset; 140 u_long bn; 141 u_long bo; 142 struct buf *bp = NULL; 143 u_long bp_bn = -1; 144 struct msdosfsmount *pmp = dep->de_pmp; 145 u_long bsize; 146 int fat12 = FAT12(pmp); /* 12 bit fat */ 147 148 fc_bmapcalls++; 149 150 /* 151 * If they don't give us someplace to return a value then don't 152 * bother doing anything. 153 */ 154 if (bnp == NULL && cnp == NULL) 155 return 0; 156 157 cn = dep->de_StartCluster; 158 /* 159 * The "file" that makes up the root directory is contiguous, 160 * permanently allocated, of fixed size, and is not made up of 161 * clusters. If the cluster number is beyond the end of the root 162 * directory, then return the number of clusters in the file. 163 */ 164 if (cn == MSDOSFSROOT) { 165 if (dep->de_Attributes & ATTR_DIRECTORY) { 166 if (findcn * pmp->pm_SectPerClust > pmp->pm_rootdirsize) { 167 if (cnp) 168 *cnp = pmp->pm_rootdirsize / pmp->pm_SectPerClust; 169 return E2BIG; 170 } 171 if (bnp) 172 *bnp = pmp->pm_rootdirblk + (findcn * pmp->pm_SectPerClust); 173 if (cnp) 174 *cnp = MSDOSFSROOT; 175 return 0; 176 } else { /* just an empty file */ 177 if (cnp) 178 *cnp = 0; 179 return E2BIG; 180 } 181 } 182 183 /* 184 * Rummage around in the fat cache, maybe we can avoid tromping 185 * thru every fat entry for the file. And, keep track of how far 186 * off the cache was from where we wanted to be. 187 */ 188 i = 0; 189 fc_lookup(dep, findcn, &i, &cn); 190 if ((bn = findcn - i) >= LMMAX) 191 fc_largedistance++; 192 else 193 fc_lmdistance[bn]++; 194 195 /* 196 * Handle all other files or directories the normal way. 197 */ 198 prevcn = 0; 199 for (; i < findcn; i++) { 200 if (MSDOSFSEOF(cn)) 201 goto hiteof; 202 byteoffset = FATOFS(pmp, cn); 203 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 204 if (bn != bp_bn) { 205 if (bp) 206 brelse(bp); 207 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 208 if (error) 209 return error; 210 bp_bn = bn; 211 } 212 prevcn = cn; 213 cn = getushort(&bp->b_data[bo]); 214 if (fat12) { 215 if (prevcn & 1) 216 cn >>= 4; 217 cn &= 0x0fff; 218 /* 219 * Force the special cluster numbers in the range 220 * 0x0ff0-0x0fff to be the same as for 16 bit 221 * cluster numbers to let the rest of msdosfs think 222 * it is always dealing with 16 bit fats. 223 */ 224 if ((cn & 0x0ff0) == 0x0ff0) 225 cn |= 0xf000; 226 } 227 } 228 229 if (!MSDOSFSEOF(cn)) { 230 if (bp) 231 brelse(bp); 232 if (bnp) 233 *bnp = cntobn(pmp, cn); 234 if (cnp) 235 *cnp = cn; 236 fc_setcache(dep, FC_LASTMAP, i, cn); 237 return 0; 238 } 239 240 hiteof:; 241 if (cnp) 242 *cnp = i; 243 if (bp) 244 brelse(bp); 245 /* update last file cluster entry in the fat cache */ 246 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 247 return E2BIG; 248 } 249 250 /* 251 * Find the closest entry in the fat cache to the cluster we are looking 252 * for. 253 */ 254 void 255 fc_lookup(dep, findcn, frcnp, fsrcnp) 256 struct denode *dep; 257 u_long findcn; 258 u_long *frcnp; 259 u_long *fsrcnp; 260 { 261 int i; 262 u_long cn; 263 struct fatcache *closest = 0; 264 265 for (i = 0; i < FC_SIZE; i++) { 266 cn = dep->de_fc[i].fc_frcn; 267 if (cn != FCE_EMPTY && cn <= findcn) { 268 if (closest == 0 || cn > closest->fc_frcn) 269 closest = &dep->de_fc[i]; 270 } 271 } 272 if (closest) { 273 *frcnp = closest->fc_frcn; 274 *fsrcnp = closest->fc_fsrcn; 275 } 276 } 277 278 /* 279 * Purge the fat cache in denode dep of all entries relating to file 280 * relative cluster frcn and beyond. 281 */ 282 void fc_purge(dep, frcn) 283 struct denode *dep; 284 u_int frcn; 285 { 286 int i; 287 struct fatcache *fcp; 288 289 fcp = dep->de_fc; 290 for (i = 0; i < FC_SIZE; i++, fcp++) { 291 if (fcp->fc_frcn >= frcn) 292 fcp->fc_frcn = FCE_EMPTY; 293 } 294 } 295 296 /* 297 * Update all copies of the fat. The first copy is updated last. 298 * 299 * pmp - msdosfsmount structure for filesystem to update 300 * bp - addr of modified fat block 301 * fatbn - block number relative to begin of filesystem of the modified fat block. 302 */ 303 void 304 updatefats(pmp, bp, fatbn) 305 struct msdosfsmount *pmp; 306 struct buf *bp; 307 u_long fatbn; 308 { 309 int i; 310 struct buf *bpn; 311 312 #ifdef MSDOSFS_DEBUG 313 printf("updatefats(pmp %p, bp %p, fatbn %ld)\n", pmp, bp, fatbn); 314 #endif 315 316 /* 317 * Now copy the block(s) of the modified fat to the other copies of 318 * the fat and write them out. This is faster than reading in the 319 * other fats and then writing them back out. This could tie up 320 * the fat for quite a while. Preventing others from accessing it. 321 * To prevent us from going after the fat quite so much we use 322 * delayed writes, unless they specfied "synchronous" when the 323 * filesystem was mounted. If synch is asked for then use 324 * bwrite()'s and really slow things down. 325 */ 326 for (i = 1; i < pmp->pm_FATs; i++) { 327 fatbn += pmp->pm_FATsecs; 328 /* getblk() never fails */ 329 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 330 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 331 if (pmp->pm_waitonfat) 332 bwrite(bpn); 333 else 334 bdwrite(bpn); 335 } 336 /* 337 * Write out the first fat last. 338 */ 339 if (pmp->pm_waitonfat) 340 bwrite(bp); 341 else 342 bdwrite(bp); 343 } 344 345 /* 346 * Updating entries in 12 bit fats is a pain in the butt. 347 * 348 * The following picture shows where nibbles go when moving from a 12 bit 349 * cluster number into the appropriate bytes in the FAT. 350 * 351 * byte m byte m+1 byte m+2 352 * +----+----+ +----+----+ +----+----+ 353 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 354 * +----+----+ +----+----+ +----+----+ 355 * 356 * +----+----+----+ +----+----+----+ 357 * | 3 0 1 | | 4 5 2 | 358 * +----+----+----+ +----+----+----+ 359 * cluster n cluster n+1 360 * 361 * Where n is even. m = n + (n >> 2) 362 * 363 */ 364 static inline void 365 usemap_alloc(pmp, cn) 366 struct msdosfsmount *pmp; 367 u_long cn; 368 { 369 pmp->pm_inusemap[cn / N_INUSEBITS] 370 |= 1 << (cn % N_INUSEBITS); 371 pmp->pm_freeclustercount--; 372 } 373 374 static inline void 375 usemap_free(pmp, cn) 376 struct msdosfsmount *pmp; 377 u_long cn; 378 { 379 pmp->pm_freeclustercount++; 380 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 381 } 382 383 int 384 clusterfree(pmp, cluster, oldcnp) 385 struct msdosfsmount *pmp; 386 u_long cluster; 387 u_long *oldcnp; 388 { 389 int error; 390 u_long oldcn; 391 392 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 393 if (error == 0) { 394 /* 395 * If the cluster was successfully marked free, then update 396 * the count of free clusters, and turn off the "allocated" 397 * bit in the "in use" cluster bit map. 398 */ 399 usemap_free(pmp, cluster); 400 if (oldcnp) 401 *oldcnp = oldcn; 402 } 403 return error; 404 } 405 406 /* 407 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 408 * 409 * function - whether to get or set a fat entry 410 * pmp - address of the msdosfsmount structure for the filesystem 411 * whose fat is to be manipulated. 412 * cn - which cluster is of interest 413 * oldcontents - address of a word that is to receive the contents of the 414 * cluster'th entry if this is a get function 415 * newcontents - the new value to be written into the cluster'th element of 416 * the fat if this is a set function. 417 * 418 * This function can also be used to free a cluster by setting the fat entry 419 * for a cluster to 0. 420 * 421 * All copies of the fat are updated if this is a set function. NOTE: If 422 * fatentry() marks a cluster as free it does not update the inusemap in 423 * the msdosfsmount structure. This is left to the caller. 424 */ 425 int 426 fatentry(function, pmp, cn, oldcontents, newcontents) 427 int function; 428 struct msdosfsmount *pmp; 429 u_long cn; 430 u_long *oldcontents; 431 u_long newcontents; 432 { 433 int error; 434 u_long readcn; 435 u_long bn, bo, bsize, byteoffset; 436 struct buf *bp; 437 438 /* 439 * printf("fatentry(func %d, pmp %08x, clust %d, oldcon %08x, newcon %d)\n", 440 * function, pmp, cluster, oldcontents, newcontents); 441 */ 442 443 #ifdef DIAGNOSTIC 444 /* 445 * Be sure they asked us to do something. 446 */ 447 if ((function & (FAT_SET | FAT_GET)) == 0) { 448 printf("fatentry(): function code doesn't specify get or set\n"); 449 return EINVAL; 450 } 451 452 /* 453 * If they asked us to return a cluster number but didn't tell us 454 * where to put it, give them an error. 455 */ 456 if ((function & FAT_GET) && oldcontents == NULL) { 457 printf("fatentry(): get function with no place to put result\n"); 458 return EINVAL; 459 } 460 #endif 461 462 /* 463 * Be sure the requested cluster is in the filesystem. 464 */ 465 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 466 return EINVAL; 467 468 byteoffset = FATOFS(pmp, cn); 469 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 470 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 471 if (error) 472 return error; 473 474 if (function & FAT_GET) { 475 readcn = getushort(&bp->b_data[bo]); 476 if (FAT12(pmp)) { 477 if (cn & 1) 478 readcn >>= 4; 479 readcn &= 0x0fff; 480 /* map certain 12 bit fat entries to 16 bit */ 481 if ((readcn & 0x0ff0) == 0x0ff0) 482 readcn |= 0xf000; 483 } 484 *oldcontents = readcn; 485 } 486 if (function & FAT_SET) { 487 if (FAT12(pmp)) { 488 readcn = getushort(&bp->b_data[bo]); 489 if (cn & 1) { 490 readcn &= 0x000f; 491 readcn |= newcontents << 4; 492 } else { 493 readcn &= 0xf000; 494 readcn |= newcontents & 0xfff; 495 } 496 putushort(&bp->b_data[bo], readcn); 497 } else 498 putushort(&bp->b_data[bo], newcontents); 499 updatefats(pmp, bp, bn); 500 bp = NULL; 501 pmp->pm_fmod = 1; 502 } 503 if (bp) 504 brelse(bp); 505 return 0; 506 } 507 508 /* 509 * Update a contiguous cluster chain 510 * 511 * pmp - mount point 512 * start - first cluster of chain 513 * count - number of clusters in chain 514 * fillwith - what to write into fat entry of last cluster 515 */ 516 static int 517 fatchain(pmp, start, count, fillwith) 518 struct msdosfsmount *pmp; 519 u_long start; 520 u_long count; 521 u_long fillwith; 522 { 523 int error; 524 u_long bn, bo, bsize, byteoffset, readcn, newc; 525 struct buf *bp; 526 527 #ifdef MSDOSFS_DEBUG 528 printf("fatchain(pmp %p, start %ld, count %ld, fillwith %ld)\n", 529 pmp, start, count, fillwith); 530 #endif 531 /* 532 * Be sure the clusters are in the filesystem. 533 */ 534 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 535 return EINVAL; 536 537 while (count > 0) { 538 byteoffset = FATOFS(pmp, start); 539 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 540 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 541 if (error) 542 return error; 543 while (count > 0) { 544 start++; 545 newc = --count > 0 ? start : fillwith; 546 if (FAT12(pmp)) { 547 readcn = getushort(&bp->b_data[bo]); 548 if (start & 1) { 549 readcn &= 0xf000; 550 readcn |= newc & 0xfff; 551 } else { 552 readcn &= 0x000f; 553 readcn |= newc << 4; 554 } 555 putushort(&bp->b_data[bo], readcn); 556 bo++; 557 if (!(start & 1)) 558 bo++; 559 } else { 560 putushort(&bp->b_data[bo], newc); 561 bo += 2; 562 } 563 if (bo >= bsize) 564 break; 565 } 566 updatefats(pmp, bp, bn); 567 } 568 pmp->pm_fmod = 1; 569 return 0; 570 } 571 572 /* 573 * Check the length of a free cluster chain starting at start. 574 * 575 * pmp - mount point 576 * start - start of chain 577 * count - maximum interesting length 578 */ 579 int 580 chainlength(pmp, start, count) 581 struct msdosfsmount *pmp; 582 u_long start; 583 u_long count; 584 { 585 u_long idx, max_idx; 586 u_int map; 587 u_long len; 588 589 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 590 idx = start / N_INUSEBITS; 591 start %= N_INUSEBITS; 592 map = pmp->pm_inusemap[idx]; 593 map &= ~((1 << start) - 1); 594 if (map) { 595 len = ffs(map) - 1 - start; 596 return len > count ? count : len; 597 } 598 len = N_INUSEBITS - start; 599 if (len >= count) 600 return count; 601 while (++idx <= max_idx) { 602 if (len >= count) 603 break; 604 map = pmp->pm_inusemap[idx]; 605 if (map) { 606 len += ffs(map) - 1; 607 break; 608 } 609 len += N_INUSEBITS; 610 } 611 return len > count ? count : len; 612 } 613 614 /* 615 * Allocate contigous free clusters. 616 * 617 * pmp - mount point. 618 * start - start of cluster chain. 619 * count - number of clusters to allocate. 620 * fillwith - put this value into the fat entry for the 621 * last allocated cluster. 622 * retcluster - put the first allocated cluster's number here. 623 * got - how many clusters were actually allocated. 624 */ 625 int 626 chainalloc(pmp, start, count, fillwith, retcluster, got) 627 struct msdosfsmount *pmp; 628 u_long start; 629 u_long count; 630 u_long fillwith; 631 u_long *retcluster; 632 u_long *got; 633 { 634 int error; 635 636 error = fatchain(pmp, start, count, fillwith); 637 if (error == 0) { 638 #ifdef MSDOSFS_DEBUG 639 printf("clusteralloc(): allocated cluster chain at %ld (%ld clusters)\n", 640 start, count); 641 #endif 642 if (retcluster) 643 *retcluster = start; 644 if (got) 645 *got = count; 646 while (count-- > 0) 647 usemap_alloc(pmp, start++); 648 } 649 return error; 650 } 651 652 /* 653 * Allocate contiguous free clusters. 654 * 655 * pmp - mount point. 656 * start - preferred start of cluster chain. 657 * count - number of clusters requested. 658 * fillwith - put this value into the fat entry for the 659 * last allocated cluster. 660 * retcluster - put the first allocated cluster's number here. 661 * got - how many clusters were actually allocated. 662 */ 663 int 664 clusteralloc(pmp, start, count, fillwith, retcluster, got) 665 struct msdosfsmount *pmp; 666 u_long start; 667 u_long count; 668 u_long fillwith; 669 u_long *retcluster; 670 u_long *got; 671 { 672 u_long idx; 673 u_long len, newst, foundcn, foundl, cn, l; 674 u_int map; 675 676 #ifdef MSDOSFS_DEBUG 677 printf("clusteralloc(): find %d clusters\n",count); 678 #endif 679 if (start) { 680 if ((len = chainlength(pmp, start, count)) >= count) 681 return chainalloc(pmp, start, count, fillwith, retcluster, got); 682 } else { 683 /* 684 * This is a new file, initialize start 685 */ 686 struct timeval tv; 687 688 microtime(&tv); 689 start = (tv.tv_usec >> 10)|tv.tv_usec; 690 len = 0; 691 } 692 693 /* 694 * Start at a (pseudo) random place to maximize cluster runs 695 * under multiple writers. 696 */ 697 foundcn = newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 698 foundl = 0; 699 700 for (cn = newst; cn <= pmp->pm_maxcluster;) { 701 idx = cn / N_INUSEBITS; 702 map = pmp->pm_inusemap[idx]; 703 map |= (1 << (cn % N_INUSEBITS)) - 1; 704 if (map != (u_int)-1) { 705 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 706 if ((l = chainlength(pmp, cn, count)) >= count) 707 return chainalloc(pmp, cn, count, fillwith, retcluster, got); 708 if (l > foundl) { 709 foundcn = cn; 710 foundl = l; 711 } 712 cn += l + 1; 713 continue; 714 } 715 cn += N_INUSEBITS - cn % N_INUSEBITS; 716 } 717 for (cn = 0; cn < newst;) { 718 idx = cn / N_INUSEBITS; 719 map = pmp->pm_inusemap[idx]; 720 map |= (1 << (cn % N_INUSEBITS)) - 1; 721 if (map != (u_int)-1) { 722 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 723 if ((l = chainlength(pmp, cn, count)) >= count) 724 return chainalloc(pmp, cn, count, fillwith, retcluster, got); 725 if (l > foundl) { 726 foundcn = cn; 727 foundl = l; 728 } 729 cn += l + 1; 730 continue; 731 } 732 cn += N_INUSEBITS - cn % N_INUSEBITS; 733 } 734 735 if (!foundl) 736 return ENOSPC; 737 738 if (len) 739 return chainalloc(pmp, start, len, fillwith, retcluster, got); 740 else 741 return chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got); 742 } 743 744 745 /* 746 * Free a chain of clusters. 747 * 748 * pmp - address of the msdosfs mount structure for the filesystem 749 * containing the cluster chain to be freed. 750 * startcluster - number of the 1st cluster in the chain of clusters to be 751 * freed. 752 */ 753 int 754 freeclusterchain(pmp, cluster) 755 struct msdosfsmount *pmp; 756 u_long cluster; 757 { 758 int error = 0; 759 struct buf *bp = NULL; 760 u_long bn, bo, bsize, byteoffset; 761 u_long readcn, lbn = -1; 762 763 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 764 byteoffset = FATOFS(pmp, cluster); 765 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 766 if (lbn != bn) { 767 if (bp) 768 updatefats(pmp, bp, lbn); 769 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 770 if (error) 771 return error; 772 lbn = bn; 773 } 774 usemap_free(pmp, cluster); 775 readcn = getushort(&bp->b_data[bo]); 776 if (FAT12(pmp)) { 777 if (cluster & 1) { 778 cluster = readcn >> 4; 779 readcn &= 0x000f; 780 readcn |= MSDOSFSFREE << 4; 781 } else { 782 cluster = readcn; 783 readcn &= 0xf000; 784 readcn |= MSDOSFSFREE & 0xfff; 785 } 786 putushort(&bp->b_data[bo], readcn); 787 cluster &= 0x0fff; 788 if ((cluster&0x0ff0) == 0x0ff0) 789 cluster |= 0xf000; 790 } else { 791 cluster = readcn; 792 putushort(&bp->b_data[bo], MSDOSFSFREE); 793 } 794 } 795 if (bp) 796 updatefats(pmp, bp, bn); 797 return error; 798 } 799 800 /* 801 * Read in fat blocks looking for free clusters. For every free cluster 802 * found turn off its corresponding bit in the pm_inusemap. 803 */ 804 int 805 fillinusemap(pmp) 806 struct msdosfsmount *pmp; 807 { 808 struct buf *bp = NULL; 809 u_long cn, readcn; 810 int error; 811 int fat12 = FAT12(pmp); 812 u_long bn, bo, bsize, byteoffset; 813 814 /* 815 * Mark all clusters in use, we mark the free ones in the fat scan 816 * loop further down. 817 */ 818 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 819 pmp->pm_inusemap[cn] = (u_int)-1; 820 821 /* 822 * Figure how many free clusters are in the filesystem by ripping 823 * through the fat counting the number of entries whose content is 824 * zero. These represent free clusters. 825 */ 826 pmp->pm_freeclustercount = 0; 827 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 828 byteoffset = FATOFS(pmp, cn); 829 bo = byteoffset % pmp->pm_fatblocksize; 830 if (!bo || !bp) { 831 /* Read new FAT block */ 832 if (bp) 833 brelse(bp); 834 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 835 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 836 if (error) 837 return error; 838 } 839 readcn = getushort(&bp->b_data[bo]); 840 if (fat12) { 841 if (cn & 1) 842 readcn >>= 4; 843 readcn &= 0x0fff; 844 } 845 846 if (readcn == 0) 847 usemap_free(pmp, cn); 848 } 849 brelse(bp); 850 return 0; 851 } 852 853 /* 854 * Allocate a new cluster and chain it onto the end of the file. 855 * 856 * dep - the file to extend 857 * count - number of clusters to allocate 858 * bpp - where to return the address of the buf header for the first new 859 * file block 860 * ncp - where to put cluster number of the first newly allocated cluster 861 * If this pointer is 0, do not return the cluster number. 862 * flags - see fat.h 863 * 864 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 865 * the de_flag field of the denode and it does not change the de_FileSize 866 * field. This is left for the caller to do. 867 */ 868 int 869 extendfile(dep, count, bpp, ncp, flags) 870 struct denode *dep; 871 u_long count; 872 struct buf **bpp; 873 u_long *ncp; 874 int flags; 875 { 876 int error = 0; 877 u_long frcn; 878 u_long cn, got; 879 struct msdosfsmount *pmp = dep->de_pmp; 880 struct buf *bp; 881 882 /* 883 * Don't try to extend the root directory 884 */ 885 if (DETOV(dep)->v_flag & VROOT) { 886 printf("extendfile(): attempt to extend root directory\n"); 887 return ENOSPC; 888 } 889 890 /* 891 * If the "file's last cluster" cache entry is empty, and the file 892 * is not empty, then fill the cache entry by calling pcbmap(). 893 */ 894 fc_fileextends++; 895 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 896 dep->de_StartCluster != 0) { 897 fc_lfcempty++; 898 error = pcbmap(dep, 0xffff, 0, &cn); 899 /* we expect it to return E2BIG */ 900 if (error != E2BIG) 901 return error; 902 error = 0; 903 } 904 905 while (count > 0) { 906 /* 907 * Allocate a new cluster chain and cat onto the end of the file. 908 * If the file is empty we make de_StartCluster point to the new 909 * block. Note that de_StartCluster being 0 is sufficient to be 910 * sure the file is empty since we exclude attempts to extend the 911 * root directory above, and the root dir is the only file with a 912 * startcluster of 0 that has blocks allocated (sort of). 913 */ 914 if (dep->de_StartCluster == 0) 915 cn = 0; 916 else 917 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 918 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 919 if (error) 920 return error; 921 922 count -= got; 923 924 /* 925 * Give them the filesystem relative cluster number if they want 926 * it. 927 */ 928 if (ncp) { 929 *ncp = cn; 930 ncp = NULL; 931 } 932 933 if (dep->de_StartCluster == 0) { 934 dep->de_StartCluster = cn; 935 frcn = 0; 936 } else { 937 error = fatentry(FAT_SET, pmp, dep->de_fc[FC_LASTFC].fc_fsrcn, 938 0, cn); 939 if (error) { 940 clusterfree(pmp, cn, NULL); 941 return error; 942 } 943 944 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 945 } 946 947 /* 948 * Update the "last cluster of the file" entry in the denode's fat 949 * cache. 950 */ 951 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 952 953 if (flags & DE_CLEAR) { 954 while (got-- > 0) { 955 /* 956 * Get the buf header for the new block of the file. 957 */ 958 if (dep->de_Attributes & ATTR_DIRECTORY) 959 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 960 pmp->pm_bpcluster, 0, 0); 961 else { 962 bp = getblk(DETOV(dep), frcn++, pmp->pm_bpcluster, 0, 0); 963 /* 964 * Do the bmap now, as in msdosfs_write 965 */ 966 if (pcbmap(dep, bp->b_lblkno, &bp->b_blkno, 0)) 967 bp->b_blkno = -1; 968 if (bp->b_blkno == -1) 969 panic("extendfile: pcbmap"); 970 } 971 clrbuf(bp); 972 if (bpp) { 973 *bpp = bp; 974 bpp = NULL; 975 } else { 976 bp->b_flags |= B_AGE; 977 bawrite(bp); 978 } 979 } 980 } 981 } 982 983 return 0; 984 } 985