1/* $OpenBSD: msdosfs_fat.c,v 1.36 2023/06/16 08:42:08 sf Exp $ */ 2/* $NetBSD: msdosfs_fat.c,v 1.26 1997/10/17 11:24:02 ws Exp $ */ 3 4/*- 5 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. 6 * Copyright (C) 1994, 1995, 1997 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/namei.h> 58#include <sys/mount.h> /* to define statfs structure */ 59#include <sys/vnode.h> /* to define vattr structure */ 60#include <sys/lock.h> 61#include <sys/errno.h> 62#include <sys/dirent.h> 63 64/* 65 * msdosfs include files. 66 */ 67#include <msdosfs/bpb.h> 68#include <msdosfs/msdosfsmount.h> 69#include <msdosfs/direntry.h> 70#include <msdosfs/denode.h> 71#include <msdosfs/fat.h> 72 73/* 74 * Fat cache stats. 75 */ 76int fc_fileextends; /* # of file extends */ 77int fc_lfcempty; /* # of time last file cluster cache entry 78 * was empty */ 79int fc_bmapcalls; /* # of times pcbmap was called */ 80 81#define LMMAX 20 82int fc_lmdistance[LMMAX]; /* counters for how far off the last 83 * cluster mapped entry was. */ 84int fc_largedistance; /* off by more than LMMAX */ 85 86static void fatblock(struct msdosfsmount *, uint32_t, uint32_t *, uint32_t *, 87 uint32_t *); 88void updatefats(struct msdosfsmount *, struct buf *, uint32_t); 89static __inline void usemap_free(struct msdosfsmount *, uint32_t); 90static __inline void usemap_alloc(struct msdosfsmount *, uint32_t); 91static int fatchain(struct msdosfsmount *, uint32_t, uint32_t, uint32_t); 92int chainlength(struct msdosfsmount *, uint32_t, uint32_t); 93int chainalloc(struct msdosfsmount *, uint32_t, uint32_t, uint32_t, uint32_t *, 94 uint32_t *); 95 96static void 97fatblock(struct msdosfsmount *pmp, uint32_t ofs, uint32_t *bnp, uint32_t *sizep, 98 uint32_t *bop) 99{ 100 uint32_t bn, size; 101 102 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 103 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) * DEV_BSIZE; 104 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 105 106 if (bnp) 107 *bnp = bn; 108 if (sizep) 109 *sizep = size; 110 if (bop) 111 *bop = ofs % pmp->pm_fatblocksize; 112} 113 114/* 115 * Map the logical cluster number of a file into a physical disk sector 116 * that is filesystem relative. 117 * 118 * dep - address of denode representing the file of interest 119 * findcn - file relative cluster whose filesystem relative cluster number 120 * and/or block number are/is to be found 121 * bnp - address of where to place the file system relative block number. 122 * If this pointer is null then don't return this quantity. 123 * cnp - address of where to place the file system relative cluster number. 124 * If this pointer is null then don't return this quantity. 125 * sp - address of where to place the block size for the file/dir 126 * If this pointer is null then don't return this quantity. 127 * 128 * NOTE: Either bnp or cnp must be non-null. 129 * This function has one side effect. If the requested file relative cluster 130 * is beyond the end of file, then the actual number of clusters in the file 131 * is returned in *cnp. This is useful for determining how long a directory is. 132 * If cnp is null, nothing is returned. 133 */ 134int 135pcbmap(struct denode *dep, uint32_t findcn, daddr_t *bnp, uint32_t *cnp, 136 int *sp) 137{ 138 int error; 139 uint32_t i; 140 uint32_t cn; 141 uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */ 142 uint32_t byteoffset; 143 uint32_t bn; 144 uint32_t bo; 145 struct buf *bp = NULL; 146 uint32_t bp_bn = -1; 147 struct msdosfsmount *pmp = dep->de_pmp; 148 uint32_t bsize; 149 150 fc_bmapcalls++; 151 152 /* 153 * If they don't give us someplace to return a value then don't 154 * bother doing anything. 155 */ 156 if (bnp == NULL && cnp == NULL && sp == NULL) 157 return (0); 158 159 cn = dep->de_StartCluster; 160 /* 161 * The "file" that makes up the root directory is contiguous, 162 * permanently allocated, of fixed size, and is not made up of 163 * clusters. If the cluster number is beyond the end of the root 164 * directory, then return the number of clusters in the file. 165 */ 166 if (cn == MSDOSFSROOT) { 167 if (dep->de_Attributes & ATTR_DIRECTORY) { 168 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 169 if (cnp) 170 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 171 return (E2BIG); 172 } 173 if (bnp) 174 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 175 if (cnp) 176 *cnp = MSDOSFSROOT; 177 if (sp) 178 *sp = min(pmp->pm_bpcluster, 179 dep->de_FileSize - de_cn2off(pmp, findcn)); 180 return (0); 181 } else { /* just an empty file */ 182 if (cnp) 183 *cnp = 0; 184 return (E2BIG); 185 } 186 } 187 188 /* 189 * All other files do I/O in cluster sized blocks 190 */ 191 if (sp) 192 *sp = pmp->pm_bpcluster; 193 194 /* 195 * Rummage around in the fat cache, maybe we can avoid tromping 196 * thru every fat entry for the file. And, keep track of how far 197 * off the cache was from where we wanted to be. 198 */ 199 i = 0; 200 fc_lookup(dep, findcn, &i, &cn); 201 if ((bn = findcn - i) >= LMMAX) 202 fc_largedistance++; 203 else 204 fc_lmdistance[bn]++; 205 206 /* 207 * Handle all other files or directories the normal way. 208 */ 209 for (; i < findcn; i++) { 210 /* 211 * Stop with all reserved clusters, not just with EOF. 212 */ 213 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 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, &bp); 221 if (error) { 222 brelse(bp); 223 return (error); 224 } 225 bp_bn = bn; 226 } 227 prevcn = cn; 228 if (bo >= bsize) { 229 if (bp) 230 brelse(bp); 231 return (EIO); 232 } 233 if (FAT32(pmp)) 234 cn = getulong(&bp->b_data[bo]); 235 else 236 cn = getushort(&bp->b_data[bo]); 237 if (FAT12(pmp) && (prevcn & 1)) 238 cn >>= 4; 239 cn &= pmp->pm_fatmask; 240 241 /* 242 * Force the special cluster numbers 243 * to be the same for all cluster sizes 244 * to let the rest of msdosfs handle 245 * all cases the same. 246 */ 247 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 248 cn |= ~pmp->pm_fatmask; 249 } 250 251 if (!MSDOSFSEOF(pmp, cn)) { 252 if (bp) 253 brelse(bp); 254 if (bnp) 255 *bnp = cntobn(pmp, cn); 256 if (cnp) 257 *cnp = cn; 258 fc_setcache(dep, FC_LASTMAP, i, cn); 259 return (0); 260 } 261 262hiteof: 263 if (cnp) 264 *cnp = i; 265 if (bp) 266 brelse(bp); 267 /* update last file cluster entry in the fat cache */ 268 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 269 return (E2BIG); 270} 271 272/* 273 * Find the closest entry in the fat cache to the cluster we are looking 274 * for. 275 */ 276void 277fc_lookup(struct denode *dep, uint32_t findcn, uint32_t *frcnp, uint32_t *fsrcnp) 278{ 279 int i; 280 uint32_t cn; 281 struct fatcache *closest = 0; 282 283 for (i = 0; i < FC_SIZE; i++) { 284 cn = dep->de_fc[i].fc_frcn; 285 if (cn != FCE_EMPTY && cn <= findcn) { 286 if (closest == 0 || cn > closest->fc_frcn) 287 closest = &dep->de_fc[i]; 288 } 289 } 290 if (closest) { 291 *frcnp = closest->fc_frcn; 292 *fsrcnp = closest->fc_fsrcn; 293 } 294} 295 296/* 297 * Purge the fat cache in denode dep of all entries relating to file 298 * relative cluster frcn and beyond. 299 */ 300void 301fc_purge(struct denode *dep, u_int frcn) 302{ 303 int i; 304 struct fatcache *fcp; 305 306 fcp = dep->de_fc; 307 for (i = 0; i < FC_SIZE; i++, fcp++) { 308 if (fcp->fc_frcn >= frcn) 309 fcp->fc_frcn = FCE_EMPTY; 310 } 311} 312 313/* 314 * Update the fat. 315 * If mirroring the fat, update all copies, with the first copy as last. 316 * Else update only the current fat (ignoring the others). 317 * 318 * pmp - msdosfsmount structure for filesystem to update 319 * bp - addr of modified fat block 320 * fatbn - block number relative to begin of filesystem of the modified fat block. 321 */ 322void 323updatefats(struct msdosfsmount *pmp, struct buf *bp, uint32_t fatbn) 324{ 325 int i; 326 struct buf *bpn; 327 328#ifdef MSDOSFS_DEBUG 329 printf("updatefats(pmp %p, buf %p, fatbn %d)\n", pmp, bp, fatbn); 330#endif 331 332 /* 333 * If we have an FSInfo block, update it. 334 */ 335 if (pmp->pm_fsinfo) { 336 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), 337 &bpn) != 0) { 338 /* 339 * Ignore the error, but turn off FSInfo update for the future. 340 */ 341 pmp->pm_fsinfo = 0; 342 brelse(bpn); 343 } else { 344 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 345 346 putulong(fp->fsinfree, pmp->pm_freeclustercount); 347 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 348 bwrite(bpn); 349 else 350 bdwrite(bpn); 351 } 352 } 353 354 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 355 /* 356 * Now copy the block(s) of the modified fat to the other copies of 357 * the fat and write them out. This is faster than reading in the 358 * other fats and then writing them back out. This could tie up 359 * the fat for quite a while. Preventing others from accessing it. 360 * To prevent us from going after the fat quite so much we use 361 * delayed writes, unless they specified "synchronous" when the 362 * filesystem was mounted. If synch is asked for then use 363 * bwrite()'s and really slow things down. 364 */ 365 for (i = 1; i < pmp->pm_FATs; i++) { 366 fatbn += pmp->pm_FATsecs; 367 /* getblk() never fails */ 368 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 369 INFSLP); 370 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 371 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 372 bwrite(bpn); 373 else 374 bdwrite(bpn); 375 } 376 } 377 378 /* 379 * Write out the first (or current) fat last. 380 */ 381 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 382 bwrite(bp); 383 else 384 bdwrite(bp); 385 /* 386 * Maybe update fsinfo sector here? 387 */ 388} 389 390/* 391 * Updating entries in 12 bit fats is a pain in the butt. 392 * 393 * The following picture shows where nibbles go when moving from a 12 bit 394 * cluster number into the appropriate bytes in the FAT. 395 * 396 * byte m byte m+1 byte m+2 397 * +----+----+ +----+----+ +----+----+ 398 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 399 * +----+----+ +----+----+ +----+----+ 400 * 401 * +----+----+----+ +----+----+----+ 402 * | 3 0 1 | | 4 5 2 | 403 * +----+----+----+ +----+----+----+ 404 * cluster n cluster n+1 405 * 406 * Where n is even. m = n + (n >> 2) 407 * 408 */ 409static __inline void 410usemap_alloc(struct msdosfsmount *pmp, uint32_t cn) 411{ 412 KASSERT(cn <= pmp->pm_maxcluster); 413 414 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS); 415 pmp->pm_freeclustercount--; 416} 417 418static __inline void 419usemap_free(struct msdosfsmount *pmp, uint32_t cn) 420{ 421 KASSERT(cn <= pmp->pm_maxcluster); 422 423 pmp->pm_freeclustercount++; 424 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1U << (cn % N_INUSEBITS)); 425} 426 427int 428clusterfree(struct msdosfsmount *pmp, uint32_t cluster, uint32_t *oldcnp) 429{ 430 int error; 431 uint32_t oldcn; 432 433 usemap_free(pmp, cluster); 434 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 435 if (error) { 436 usemap_alloc(pmp, cluster); 437 return (error); 438 } 439 /* 440 * If the cluster was successfully marked free, then update 441 * the count of free clusters, and turn off the "allocated" 442 * bit in the "in use" cluster bit map. 443 */ 444 if (oldcnp) 445 *oldcnp = oldcn; 446 return (0); 447} 448 449/* 450 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 451 * 452 * function - whether to get or set a fat entry 453 * pmp - address of the msdosfsmount structure for the filesystem 454 * whose fat is to be manipulated. 455 * cn - which cluster is of interest 456 * oldcontents - address of a word that is to receive the contents of the 457 * cluster'th entry if this is a get function 458 * newcontents - the new value to be written into the cluster'th element of 459 * the fat if this is a set function. 460 * 461 * This function can also be used to free a cluster by setting the fat entry 462 * for a cluster to 0. 463 * 464 * All copies of the fat are updated if this is a set function. NOTE: If 465 * fatentry() marks a cluster as free it does not update the inusemap in 466 * the msdosfsmount structure. This is left to the caller. 467 */ 468int 469fatentry(int function, struct msdosfsmount *pmp, uint32_t cn, uint32_t *oldcontents, 470 uint32_t newcontents) 471{ 472 int error; 473 uint32_t readcn; 474 uint32_t bn, bo, bsize, byteoffset; 475 struct buf *bp; 476 477#ifdef MSDOSFS_DEBUG 478 printf("fatentry(func %d, pmp %p, clust %d, oldcon %p, " 479 "newcon %d)\n", function, pmp, cn, oldcontents, newcontents); 480#endif 481 482#ifdef DIAGNOSTIC 483 /* 484 * Be sure they asked us to do something. 485 */ 486 if ((function & (FAT_SET | FAT_GET)) == 0) { 487 printf("fatentry(): function code doesn't specify get or set\n"); 488 return (EINVAL); 489 } 490 491 /* 492 * If they asked us to return a cluster number but didn't tell us 493 * where to put it, give them an error. 494 */ 495 if ((function & FAT_GET) && oldcontents == NULL) { 496 printf("fatentry(): get function with no place to put result\n"); 497 return (EINVAL); 498 } 499#endif 500 501 /* 502 * Be sure the requested cluster is in the filesystem. 503 */ 504 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 505 return (EINVAL); 506 507 byteoffset = FATOFS(pmp, cn); 508 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 509 if ((error = bread(pmp->pm_devvp, bn, bsize, &bp)) != 0) { 510 brelse(bp); 511 return (error); 512 } 513 514 if (function & FAT_GET) { 515 if (FAT32(pmp)) 516 readcn = getulong(&bp->b_data[bo]); 517 else 518 readcn = getushort(&bp->b_data[bo]); 519 if (FAT12(pmp) && (cn & 1)) 520 readcn >>= 4; 521 readcn &= pmp->pm_fatmask; 522 /* map reserved fat entries to same values for all fats */ 523 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 524 readcn |= ~pmp->pm_fatmask; 525 *oldcontents = readcn; 526 } 527 if (function & FAT_SET) { 528 switch (pmp->pm_fatmask) { 529 case FAT12_MASK: 530 readcn = getushort(&bp->b_data[bo]); 531 if (cn & 1) { 532 readcn &= 0x000f; 533 readcn |= newcontents << 4; 534 } else { 535 readcn &= 0xf000; 536 readcn |= newcontents & 0xfff; 537 } 538 putushort(&bp->b_data[bo], readcn); 539 break; 540 case FAT16_MASK: 541 putushort(&bp->b_data[bo], newcontents); 542 break; 543 case FAT32_MASK: 544 /* 545 * According to spec we have to retain the 546 * high order bits of the fat entry. 547 */ 548 readcn = getulong(&bp->b_data[bo]); 549 readcn &= ~FAT32_MASK; 550 readcn |= newcontents & FAT32_MASK; 551 putulong(&bp->b_data[bo], readcn); 552 break; 553 } 554 updatefats(pmp, bp, bn); 555 bp = NULL; 556 pmp->pm_fmod = 1; 557 } 558 if (bp) 559 brelse(bp); 560 return (0); 561} 562 563/* 564 * Update a contiguous cluster chain 565 * 566 * pmp - mount point 567 * start - first cluster of chain 568 * count - number of clusters in chain 569 * fillwith - what to write into fat entry of last cluster 570 */ 571static int 572fatchain(struct msdosfsmount *pmp, uint32_t start, uint32_t count, uint32_t fillwith) 573{ 574 int error; 575 uint32_t bn, bo, bsize, byteoffset, readcn, newc; 576 struct buf *bp; 577 578#ifdef MSDOSFS_DEBUG 579 printf("fatchain(pmp %p, start %d, count %d, fillwith %d)\n", 580 pmp, start, count, fillwith); 581#endif 582 /* 583 * Be sure the clusters are in the filesystem. 584 */ 585 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 586 return (EINVAL); 587 588 while (count > 0) { 589 byteoffset = FATOFS(pmp, start); 590 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 591 error = bread(pmp->pm_devvp, bn, bsize, &bp); 592 if (error) { 593 brelse(bp); 594 return (error); 595 } 596 while (count > 0) { 597 start++; 598 newc = --count > 0 ? start : fillwith; 599 switch (pmp->pm_fatmask) { 600 case FAT12_MASK: 601 readcn = getushort(&bp->b_data[bo]); 602 if (start & 1) { 603 readcn &= 0xf000; 604 readcn |= newc & 0xfff; 605 } else { 606 readcn &= 0x000f; 607 readcn |= newc << 4; 608 } 609 putushort(&bp->b_data[bo], readcn); 610 bo++; 611 if (!(start & 1)) 612 bo++; 613 break; 614 case FAT16_MASK: 615 putushort(&bp->b_data[bo], newc); 616 bo += 2; 617 break; 618 case FAT32_MASK: 619 readcn = getulong(&bp->b_data[bo]); 620 readcn &= ~pmp->pm_fatmask; 621 readcn |= newc & pmp->pm_fatmask; 622 putulong(&bp->b_data[bo], readcn); 623 bo += 4; 624 break; 625 } 626 if (bo >= bsize) 627 break; 628 } 629 updatefats(pmp, bp, bn); 630 } 631 pmp->pm_fmod = 1; 632 return (0); 633} 634 635/* 636 * Check the length of a free cluster chain starting at start. 637 * 638 * pmp - mount point 639 * start - start of chain 640 * count - maximum interesting length 641 */ 642int 643chainlength(struct msdosfsmount *pmp, uint32_t start, uint32_t count) 644{ 645 uint32_t idx, max_idx; 646 u_int map; 647 uint32_t len; 648 649 if (start > pmp->pm_maxcluster) 650 return (0); 651 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 652 idx = start / N_INUSEBITS; 653 start %= N_INUSEBITS; 654 map = pmp->pm_inusemap[idx]; 655 map &= ~((1U << start) - 1); 656 if (map) { 657 len = ffs(map) - 1 - start; 658 len = MIN(len, count); 659 len = MIN(len, pmp->pm_maxcluster - start + 1); 660 return (len); 661 } 662 len = N_INUSEBITS - start; 663 if (len >= count) { 664 len = MIN(count, pmp->pm_maxcluster - start + 1); 665 return (len); 666 } 667 while (++idx <= max_idx) { 668 if (len >= count) 669 break; 670 if ((map = pmp->pm_inusemap[idx]) != 0) { 671 len += ffs(map) - 1; 672 break; 673 } 674 len += N_INUSEBITS; 675 } 676 len = MIN(len, count); 677 len = MIN(len, pmp->pm_maxcluster - start + 1); 678 return (len); 679} 680 681/* 682 * Allocate contiguous free clusters. 683 * 684 * pmp - mount point. 685 * start - start of cluster chain. 686 * count - number of clusters to allocate. 687 * fillwith - put this value into the fat entry for the 688 * last allocated cluster. 689 * retcluster - put the first allocated cluster's number here. 690 * got - how many clusters were actually allocated. 691 */ 692int 693chainalloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count, 694 uint32_t fillwith, uint32_t *retcluster, uint32_t *got) 695{ 696 int error; 697 uint32_t cl, n; 698 699 for (cl = start, n = count; n-- > 0;) 700 usemap_alloc(pmp, cl++); 701 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 702 return (error); 703#ifdef MSDOSFS_DEBUG 704 printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n", 705 start, count); 706#endif 707 if (retcluster) 708 *retcluster = start; 709 if (got) 710 *got = count; 711 return (0); 712} 713 714/* 715 * Allocate contiguous free clusters. 716 * 717 * pmp - mount point. 718 * start - preferred start of cluster chain. 719 * count - number of clusters requested. 720 * fillwith - put this value into the fat entry for the 721 * last allocated cluster. 722 * retcluster - put the first allocated cluster's number here. 723 * got - how many clusters were actually allocated. 724 */ 725int 726clusteralloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count, 727 uint32_t *retcluster, uint32_t *got) 728{ 729 uint32_t idx; 730 uint32_t len, newst, foundl, cn, l; 731 uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */ 732 uint32_t fillwith = CLUST_EOFE; 733 u_int map; 734 735#ifdef MSDOSFS_DEBUG 736 printf("clusteralloc(): find %d clusters\n",count); 737#endif 738 if (start) { 739 if ((len = chainlength(pmp, start, count)) >= count) 740 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 741 } else { 742 /* 743 * This is a new file, initialize start 744 */ 745 struct timeval tv; 746 747 microtime(&tv); 748 start = (tv.tv_usec >> 10) | tv.tv_usec; 749 len = 0; 750 } 751 752 /* 753 * Start at a (pseudo) random place to maximize cluster runs 754 * under multiple writers. 755 */ 756 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 757 foundl = 0; 758 759 for (cn = newst; cn <= pmp->pm_maxcluster;) { 760 idx = cn / N_INUSEBITS; 761 map = pmp->pm_inusemap[idx]; 762 map |= (1U << (cn % N_INUSEBITS)) - 1; 763 if (map != (u_int)-1) { 764 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 765 if ((l = chainlength(pmp, cn, count)) >= count) 766 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 767 if (l > foundl) { 768 foundcn = cn; 769 foundl = l; 770 } 771 cn += l + 1; 772 continue; 773 } 774 cn += N_INUSEBITS - cn % N_INUSEBITS; 775 } 776 for (cn = 0; cn < newst;) { 777 idx = cn / N_INUSEBITS; 778 map = pmp->pm_inusemap[idx]; 779 map |= (1U << (cn % N_INUSEBITS)) - 1; 780 if (map != (u_int)-1) { 781 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 782 if ((l = chainlength(pmp, cn, count)) >= count) 783 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 784 if (l > foundl) { 785 foundcn = cn; 786 foundl = l; 787 } 788 cn += l + 1; 789 continue; 790 } 791 cn += N_INUSEBITS - cn % N_INUSEBITS; 792 } 793 794 if (!foundl) 795 return (ENOSPC); 796 797 if (len) 798 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 799 else 800 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 801} 802 803 804/* 805 * Free a chain of clusters. 806 * 807 * pmp - address of the msdosfs mount structure for the filesystem 808 * containing the cluster chain to be freed. 809 * startcluster - number of the 1st cluster in the chain of clusters to be 810 * freed. 811 */ 812int 813freeclusterchain(struct msdosfsmount *pmp, uint32_t cluster) 814{ 815 int error; 816 struct buf *bp = NULL; 817 uint32_t bn, bo, bsize, byteoffset; 818 uint32_t readcn, lbn = -1; 819 820 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 821 byteoffset = FATOFS(pmp, cluster); 822 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 823 if (lbn != bn) { 824 if (bp) 825 updatefats(pmp, bp, lbn); 826 error = bread(pmp->pm_devvp, bn, bsize, &bp); 827 if (error) { 828 brelse(bp); 829 return (error); 830 } 831 lbn = bn; 832 } 833 usemap_free(pmp, cluster); 834 switch (pmp->pm_fatmask) { 835 case FAT12_MASK: 836 readcn = getushort(&bp->b_data[bo]); 837 if (cluster & 1) { 838 cluster = readcn >> 4; 839 readcn &= 0x000f; 840 readcn |= MSDOSFSFREE << 4; 841 } else { 842 cluster = readcn; 843 readcn &= 0xf000; 844 readcn |= MSDOSFSFREE & 0xfff; 845 } 846 putushort(&bp->b_data[bo], readcn); 847 break; 848 case FAT16_MASK: 849 cluster = getushort(&bp->b_data[bo]); 850 putushort(&bp->b_data[bo], MSDOSFSFREE); 851 break; 852 case FAT32_MASK: 853 cluster = getulong(&bp->b_data[bo]); 854 putulong(&bp->b_data[bo], 855 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 856 break; 857 } 858 cluster &= pmp->pm_fatmask; 859 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 860 cluster |= pmp->pm_fatmask; 861 } 862 if (bp) 863 updatefats(pmp, bp, bn); 864 return (0); 865} 866 867/* 868 * Read in fat blocks looking for free clusters. For every free cluster 869 * found turn off its corresponding bit in the pm_inusemap. 870 */ 871int 872fillinusemap(struct msdosfsmount *pmp) 873{ 874 struct buf *bp = NULL; 875 uint32_t cn, readcn; 876 int error; 877 uint32_t bn, bo, bsize, byteoffset; 878 879 /* 880 * Mark all clusters in use, we mark the free ones in the fat scan 881 * loop further down. 882 */ 883 for (cn = 0; cn < howmany(pmp->pm_maxcluster + 1, N_INUSEBITS); cn++) 884 pmp->pm_inusemap[cn] = (u_int)-1; 885 886 /* 887 * Figure how many free clusters are in the filesystem by ripping 888 * through the fat counting the number of entries whose content is 889 * zero. These represent free clusters. 890 */ 891 pmp->pm_freeclustercount = 0; 892 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 893 byteoffset = FATOFS(pmp, cn); 894 bo = byteoffset % pmp->pm_fatblocksize; 895 if (!bo || !bp) { 896 /* Read new FAT block */ 897 if (bp) 898 brelse(bp); 899 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 900 error = bread(pmp->pm_devvp, bn, bsize, &bp); 901 if (error) { 902 brelse(bp); 903 return (error); 904 } 905 } 906 if (FAT32(pmp)) 907 readcn = getulong(&bp->b_data[bo]); 908 else 909 readcn = getushort(&bp->b_data[bo]); 910 if (FAT12(pmp) && (cn & 1)) 911 readcn >>= 4; 912 readcn &= pmp->pm_fatmask; 913 914 if (readcn == 0) 915 usemap_free(pmp, cn); 916 } 917 brelse(bp); 918 return (0); 919} 920 921/* 922 * Allocate a new cluster and chain it onto the end of the file. 923 * 924 * dep - the file to extend 925 * count - number of clusters to allocate 926 * bpp - where to return the address of the buf header for the first new 927 * file block 928 * ncp - where to put cluster number of the first newly allocated cluster 929 * If this pointer is 0, do not return the cluster number. 930 * flags - see fat.h 931 * 932 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 933 * the de_flag field of the denode and it does not change the de_FileSize 934 * field. This is left for the caller to do. 935 */ 936int 937extendfile(struct denode *dep, uint32_t count, struct buf **bpp, uint32_t *ncp, 938 int flags) 939{ 940 int error; 941 uint32_t frcn; 942 uint32_t cn, got; 943 struct msdosfsmount *pmp = dep->de_pmp; 944 struct buf *bp; 945 946 /* 947 * Don't try to extend the root directory 948 */ 949 if (dep->de_StartCluster == MSDOSFSROOT 950 && (dep->de_Attributes & ATTR_DIRECTORY)) { 951 printf("extendfile(): attempt to extend root directory\n"); 952 return (ENOSPC); 953 } 954 955 /* 956 * If the "file's last cluster" cache entry is empty, and the file 957 * is not empty, then fill the cache entry by calling pcbmap(). 958 */ 959 fc_fileextends++; 960 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 961 dep->de_StartCluster != 0) { 962 fc_lfcempty++; 963 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 964 /* we expect it to return E2BIG */ 965 if (error != E2BIG) 966 return (error); 967 } 968 969 /* 970 * Preserve value for the last cluster before extending the file 971 * to speed up further lookups. 972 */ 973 fc_setcache(dep, FC_OLASTFC, dep->de_fc[FC_LASTFC].fc_frcn, 974 dep->de_fc[FC_LASTFC].fc_fsrcn); 975 976 while (count > 0) { 977 /* 978 * Allocate a new cluster chain and cat onto the end of the 979 * file. * If the file is empty we make de_StartCluster point 980 * to the new block. Note that de_StartCluster being 0 is 981 * sufficient to be sure the file is empty since we exclude 982 * attempts to extend the root directory above, and the root 983 * dir is the only file with a startcluster of 0 that has 984 * blocks allocated (sort of). 985 */ 986 if (dep->de_StartCluster == 0) 987 cn = 0; 988 else 989 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 990 error = clusteralloc(pmp, cn, count, &cn, &got); 991 if (error) 992 return (error); 993 994 count -= got; 995 996 /* 997 * Give them the filesystem relative cluster number if they want 998 * it. 999 */ 1000 if (ncp) { 1001 *ncp = cn; 1002 ncp = NULL; 1003 } 1004 1005 if (dep->de_StartCluster == 0) { 1006 dep->de_StartCluster = cn; 1007 frcn = 0; 1008 } else { 1009 error = fatentry(FAT_SET, pmp, 1010 dep->de_fc[FC_LASTFC].fc_fsrcn, 1011 0, cn); 1012 if (error) { 1013 clusterfree(pmp, cn, NULL); 1014 return (error); 1015 } 1016 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1017 } 1018 1019 /* 1020 * Update the "last cluster of the file" entry in the denode's fat 1021 * cache. 1022 */ 1023 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1024 1025 if (flags & DE_CLEAR) { 1026 while (got-- > 0) { 1027 /* 1028 * Get the buf header for the new block of the file. 1029 */ 1030 if (dep->de_Attributes & ATTR_DIRECTORY) 1031 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1032 pmp->pm_bpcluster, 0, INFSLP); 1033 else { 1034 bp = getblk(DETOV(dep), frcn++, 1035 pmp->pm_bpcluster, 0, INFSLP); 1036 /* 1037 * Do the bmap now, as in msdosfs_write 1038 */ 1039 if (pcbmap(dep, bp->b_lblkno, &bp->b_blkno, 0, 0)) 1040 bp->b_blkno = -1; 1041 if (bp->b_blkno == -1) 1042 panic("extendfile: pcbmap"); 1043 } 1044 clrbuf(bp); 1045 if (bpp) { 1046 *bpp = bp; 1047 bpp = NULL; 1048 } else 1049 bdwrite(bp); 1050 } 1051 } 1052 } 1053 1054 return (0); 1055} 1056