1 /* $NetBSD: msdosfs_fat.c,v 1.37 2024/05/13 00:24:19 msaitoh 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 (at) 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 (at) 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 #if HAVE_NBTOOL_CONFIG_H 51 #include "nbtool_config.h" 52 #endif 53 54 #include <sys/cdefs.h> 55 __KERNEL_RCSID(0, "$NetBSD: msdosfs_fat.c,v 1.37 2024/05/13 00:24:19 msaitoh Exp $"); 56 57 /* 58 * kernel include files. 59 */ 60 #include <sys/param.h> 61 #include <sys/file.h> 62 #ifdef _KERNEL 63 #include <sys/mount.h> /* to define statvfs structure */ 64 #include <sys/errno.h> 65 #include <sys/systm.h> 66 #include <sys/kauth.h> 67 #include <sys/dirent.h> 68 #include <sys/namei.h> 69 #include <sys/buf.h> 70 #include <sys/vnode.h> /* to define vattr structure */ 71 #else 72 #include <strings.h> 73 #include <ffs/buf.h> 74 #endif 75 76 /* 77 * msdosfs include files. 78 */ 79 #include <fs/msdosfs/bpb.h> 80 #include <fs/msdosfs/msdosfsmount.h> 81 #include <fs/msdosfs/direntry.h> 82 #include <fs/msdosfs/denode.h> 83 #include <fs/msdosfs/fat.h> 84 85 /* 86 * Fat cache stats. 87 */ 88 int fc_fileextends; /* # of file extends */ 89 int fc_lfcempty; /* # of time last file cluster cache entry 90 * was empty */ 91 int fc_bmapcalls; /* # of times pcbmap was called */ 92 93 #define LMMAX 20 94 int fc_lmdistance[LMMAX]; /* counters for how far off the last 95 * cluster mapped entry was. */ 96 int fc_largedistance; /* off by more than LMMAX */ 97 int fc_wherefrom, fc_whereto, fc_lastclust; 98 int pm_fatblocksize; 99 100 #ifdef MSDOSFS_DEBUG 101 #define DPRINTF(a) printf a 102 #else 103 #define DPRINTF(a) 104 #endif 105 #ifdef MSDOSFS_DEBUG 106 void print_fat_stats(void); 107 108 void 109 print_fat_stats(void) 110 { 111 int i; 112 113 printf("fc_fileextends=%d fc_lfcempty=%d fc_bmapcalls=%d " 114 "fc_largedistance=%d [%d->%d=%d] fc_lastclust=%d pm_fatblocksize=%d\n", 115 fc_fileextends, fc_lfcempty, fc_bmapcalls, fc_largedistance, 116 fc_wherefrom, fc_whereto, fc_whereto-fc_wherefrom, 117 fc_lastclust, pm_fatblocksize); 118 119 fc_fileextends = fc_lfcempty = fc_bmapcalls = 0; 120 fc_wherefrom = fc_whereto = fc_lastclust = 0; 121 122 for (i = 0; i < LMMAX; i++) { 123 printf("%d:%d ", i, fc_lmdistance[i]); 124 fc_lmdistance[i] = 0; 125 } 126 127 printf("\n"); 128 } 129 #endif 130 131 static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *, 132 u_long *); 133 void updatefats(struct msdosfsmount *, struct buf *, u_long); 134 static inline void usemap_free(struct msdosfsmount *, u_long); 135 static inline void usemap_alloc(struct msdosfsmount *, u_long); 136 static int fatchain(struct msdosfsmount *, u_long, u_long, u_long); 137 int chainlength(struct msdosfsmount *, u_long, u_long); 138 int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *, 139 u_long *); 140 141 static void 142 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, u_long *bop) 143 { 144 u_long bn, size; 145 146 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 147 size = uimin(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 148 * pmp->pm_BytesPerSec; 149 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 150 151 DPRINTF(("%s(ofs=%lu bn=%lu, size=%lu, bo=%lu)\n", __func__, ofs, bn, 152 size, ofs % pmp->pm_fatblocksize)); 153 if (bnp) 154 *bnp = bn; 155 if (sizep) 156 *sizep = size; 157 if (bop) 158 *bop = ofs % pmp->pm_fatblocksize; 159 160 pm_fatblocksize = pmp->pm_fatblocksize; 161 } 162 163 /* 164 * Map the logical cluster number of a file into a physical disk sector 165 * that is filesystem relative. 166 * 167 * dep - address of denode representing the file of interest 168 * findcn - file relative cluster whose filesystem relative cluster number 169 * and/or block number are/is to be found 170 * bnp - address of where to place the file system relative block number. 171 * If this pointer is null then don't return this quantity. 172 * cnp - address of where to place the file system relative cluster number. 173 * If this pointer is null then don't return this quantity. 174 * 175 * NOTE: Either bnp or cnp must be non-null. 176 * This function has one side effect. If the requested file relative cluster 177 * is beyond the end of file, then the actual number of clusters in the file 178 * is returned in *cnp. This is useful for determining how long a directory is. 179 * If cnp is null, nothing is returned. 180 */ 181 int 182 msdosfs_pcbmap(struct denode *dep, 183 u_long findcn, /* file relative cluster to get */ 184 daddr_t *bnp, /* returned filesys rel sector number */ 185 u_long *cnp, /* returned cluster number */ 186 int *sp) /* returned block size */ 187 { 188 int error; 189 u_long i; 190 u_long cn; 191 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 192 u_long byteoffset; 193 u_long bn; 194 u_long bo; 195 struct buf *bp = NULL; 196 u_long bp_bn = -1; 197 struct msdosfsmount *pmp = dep->de_pmp; 198 u_long bsize; 199 200 fc_bmapcalls++; 201 202 /* 203 * If they don't give us someplace to return a value then don't 204 * bother doing anything. 205 */ 206 if (bnp == NULL && cnp == NULL && sp == NULL) 207 return (0); 208 209 cn = dep->de_StartCluster; 210 DPRINTF(("%s(start cluster=%lu)\n", __func__, cn)); 211 /* 212 * The "file" that makes up the root directory is contiguous, 213 * permanently allocated, of fixed size, and is not made up of 214 * clusters. If the cluster number is beyond the end of the root 215 * directory, then return the number of clusters in the file. 216 */ 217 if (cn == MSDOSFSROOT) { 218 if (dep->de_Attributes & ATTR_DIRECTORY) { 219 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 220 if (cnp) 221 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 222 DPRINTF(("%s(root, %lu ETOOBIG)\n", __func__, 223 de_cn2off(pmp, findcn))); 224 return (E2BIG); 225 } 226 if (bnp) 227 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 228 if (cnp) 229 *cnp = MSDOSFSROOT; 230 if (sp) 231 *sp = uimin(pmp->pm_bpcluster, 232 dep->de_FileSize - de_cn2off(pmp, findcn)); 233 DPRINTF(("%s(root, bn=%lu, cn=%u)\n", __func__, 234 pmp->pm_rootdirblk + de_cn2bn(pmp, findcn), 235 MSDOSFSROOT)); 236 return (0); 237 } else { /* just an empty file */ 238 if (cnp) 239 *cnp = 0; 240 DPRINTF(("%s(root, empty ETOOBIG)\n", __func__)); 241 return (E2BIG); 242 } 243 } 244 245 /* 246 * All other files do I/O in cluster sized blocks 247 */ 248 if (sp) 249 *sp = pmp->pm_bpcluster; 250 251 /* 252 * Rummage around in the FAT cache, maybe we can avoid tromping 253 * thru every FAT entry for the file. And, keep track of how far 254 * off the cache was from where we wanted to be. 255 */ 256 i = 0; 257 msdosfs_fc_lookup(dep, findcn, &i, &cn); 258 DPRINTF(("%s(bpcluster=%lu i=%lu cn=%lu\n", __func__, pmp->pm_bpcluster, 259 i, cn)); 260 if ((bn = findcn - i) >= LMMAX) { 261 fc_largedistance++; 262 fc_wherefrom = i; 263 fc_whereto = findcn; 264 fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn; 265 } else 266 fc_lmdistance[bn]++; 267 268 /* 269 * Handle all other files or directories the normal way. 270 */ 271 for (; i < findcn; i++) { 272 /* 273 * Stop with all reserved clusters, not just with EOF. 274 */ 275 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask)) 276 goto hiteof; 277 278 /* 279 * Also stop when cluster is not in the filesystem 280 */ 281 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) { 282 DPRINTF(("%s(cn, %lu not in %lu..%lu)\n", __func__, 283 cn, (u_long)CLUST_FIRST, pmp->pm_maxcluster)); 284 if (bp) 285 brelse(bp, 0); 286 return (EINVAL); 287 } 288 289 byteoffset = FATOFS(pmp, cn); 290 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 291 if (bn != bp_bn) { 292 if (bp) 293 brelse(bp, 0); 294 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 295 0, &bp); 296 if (error) { 297 DPRINTF(("%s(bread, %d)\n", __func__, error)); 298 return (error); 299 } 300 bp_bn = bn; 301 } 302 prevcn = cn; 303 if (bo >= bsize) { 304 if (bp) 305 brelse(bp, 0); 306 DPRINTF(("%s(block, %lu >= %lu)\n", __func__, bo, 307 bsize)); 308 return (EIO); 309 } 310 KASSERT(bp != NULL); 311 if (FAT32(pmp)) 312 cn = getulong((char *)bp->b_data + bo); 313 else 314 cn = getushort((char *)bp->b_data + bo); 315 if (FAT12(pmp) && (prevcn & 1)) 316 cn >>= 4; 317 DPRINTF(("%s(cn=%lu masked=%lu)\n", __func__, cn, 318 cn & pmp->pm_fatmask)); 319 cn &= pmp->pm_fatmask; 320 } 321 322 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) { 323 if (bp) 324 brelse(bp, 0); 325 if (bnp) 326 *bnp = cntobn(pmp, cn); 327 if (cnp) 328 *cnp = cn; 329 DPRINTF(("%s(bn=%lu, cn=%lu)\n", __func__, cntobn(pmp, cn), 330 cn)); 331 fc_setcache(dep, FC_LASTMAP, i, cn); 332 return (0); 333 } 334 335 hiteof:; 336 if (cnp) 337 *cnp = i; 338 if (bp) 339 brelse(bp, 0); 340 /* update last file cluster entry in the FAT cache */ 341 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 342 DPRINTF(("%s(eof, %lu)\n", __func__, i)); 343 return (E2BIG); 344 } 345 346 /* 347 * Find the closest entry in the FAT cache to the cluster we are looking 348 * for. 349 */ 350 void 351 msdosfs_fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, 352 u_long *fsrcnp) 353 { 354 int i; 355 u_long cn; 356 struct fatcache *closest = 0; 357 358 for (i = 0; i < FC_SIZE; i++) { 359 cn = dep->de_fc[i].fc_frcn; 360 if (cn != FCE_EMPTY && cn <= findcn) { 361 if (closest == 0 || cn > closest->fc_frcn) 362 closest = &dep->de_fc[i]; 363 } 364 } 365 if (closest) { 366 *frcnp = closest->fc_frcn; 367 *fsrcnp = closest->fc_fsrcn; 368 } 369 } 370 371 /* 372 * Purge the FAT cache in denode dep of all entries relating to file 373 * relative cluster frcn and beyond. 374 */ 375 void 376 msdosfs_fc_purge(struct denode *dep, u_int frcn) 377 { 378 int i; 379 struct fatcache *fcp; 380 381 fcp = dep->de_fc; 382 for (i = 0; i < FC_SIZE; i++, fcp++) { 383 if (fcp->fc_frcn >= frcn) 384 fcp->fc_frcn = FCE_EMPTY; 385 } 386 } 387 388 /* 389 * Update the FAT. 390 * If mirroring the FAT, update all copies, with the first copy as last. 391 * Else update only the current FAT (ignoring the others). 392 * 393 * pmp - msdosfsmount structure for filesystem to update 394 * bp - addr of modified FAT block 395 * fatbn - block number relative to begin of filesystem of the modified FAT block. 396 */ 397 void 398 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 399 { 400 int i, error; 401 struct buf *bpn; 402 403 DPRINTF(("%s(pmp %p, bp %p, fatbn %lu)\n", __func__, pmp, bp, fatbn)); 404 405 /* 406 * If we have an FSInfo block, update it. 407 */ 408 if (pmp->pm_fsinfo) { 409 u_long cn = pmp->pm_nxtfree; 410 411 if (pmp->pm_freeclustercount 412 && (pmp->pm_inusemap[cn / N_INUSEBITS] 413 & (1U << (cn % N_INUSEBITS)))) { 414 /* 415 * The cluster indicated in FSInfo isn't free 416 * any longer. Got get a new free one. 417 */ 418 for (cn = 0; cn < pmp->pm_maxcluster; cn++) 419 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 420 break; 421 pmp->pm_nxtfree = cn 422 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 423 ^ (u_int)-1) - 1; 424 } 425 /* 426 * XXX If the fsinfo block is stored on media with 427 * 2KB or larger sectors, is the fsinfo structure 428 * padded at the end or in the middle? 429 */ 430 if (bread(pmp->pm_devvp, de_bn2kb(pmp, pmp->pm_fsinfo), 431 pmp->pm_BytesPerSec, B_MODIFY, &bpn) != 0) { 432 /* 433 * Ignore the error, but turn off FSInfo update for the future. 434 */ 435 pmp->pm_fsinfo = 0; 436 } else { 437 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 438 439 putulong(fp->fsinfree, pmp->pm_freeclustercount); 440 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 441 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 442 bwrite(bpn); 443 else 444 bdwrite(bpn); 445 } 446 } 447 448 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 449 /* 450 * Now copy the block(s) of the modified FAT to the other copies of 451 * the FAT and write them out. This is faster than reading in the 452 * other FATs and then writing them back out. This could tie up 453 * the FAT for quite a while. Preventing others from accessing it. 454 * To prevent us from going after the FAT quite so much we use 455 * delayed writes, unless they specified "synchronous" when the 456 * filesystem was mounted. If synch is asked for then use 457 * bwrite()'s and really slow things down. 458 */ 459 for (i = 1; i < pmp->pm_FATs; i++) { 460 fatbn += pmp->pm_FATsecs; 461 /* getblk() never fails */ 462 bpn = getblk(pmp->pm_devvp, de_bn2kb(pmp, fatbn), 463 bp->b_bcount, 0, 0); 464 memcpy(bpn->b_data, bp->b_data, bp->b_bcount); 465 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) { 466 error = bwrite(bpn); 467 if (error) 468 printf("%s: copy FAT %d (error=%d)\n", 469 __func__, i, error); 470 } else 471 bdwrite(bpn); 472 } 473 } 474 475 /* 476 * Write out the first (or current) FAT last. 477 */ 478 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) { 479 error = bwrite(bp); 480 if (error) 481 printf("%s: write FAT (error=%d)\n", 482 __func__, error); 483 } else 484 bdwrite(bp); 485 /* 486 * Maybe update fsinfo sector here? 487 */ 488 } 489 490 /* 491 * Updating entries in 12 bit FATs is a pain in the butt. 492 * 493 * The following picture shows where nibbles go when moving from a 12 bit 494 * cluster number into the appropriate bytes in the FAT. 495 * 496 * byte m byte m+1 byte m+2 497 * +----+----+ +----+----+ +----+----+ 498 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 499 * +----+----+ +----+----+ +----+----+ 500 * 501 * +----+----+----+ +----+----+----+ 502 * | 3 0 1 | | 4 5 2 | 503 * +----+----+----+ +----+----+----+ 504 * cluster n cluster n+1 505 * 506 * Where n is even. m = n + (n >> 2) 507 * 508 */ 509 static inline void 510 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 511 { 512 513 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS); 514 pmp->pm_freeclustercount--; 515 } 516 517 static inline void 518 usemap_free(struct msdosfsmount *pmp, u_long cn) 519 { 520 521 pmp->pm_freeclustercount++; 522 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1U << (cn % N_INUSEBITS)); 523 } 524 525 int 526 msdosfs_clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 527 { 528 int error; 529 u_long oldcn; 530 531 usemap_free(pmp, cluster); 532 error = msdosfs_fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, 533 MSDOSFSFREE); 534 if (error) { 535 usemap_alloc(pmp, cluster); 536 return (error); 537 } 538 /* 539 * If the cluster was successfully marked free, then update 540 * the count of free clusters, and turn off the "allocated" 541 * bit in the "in use" cluster bit map. 542 */ 543 if (oldcnp) 544 *oldcnp = oldcn; 545 return (0); 546 } 547 548 /* 549 * Get or Set or 'Get and Set' the cluster'th entry in the FAT. 550 * 551 * function - whether to get or set a fat entry 552 * pmp - address of the msdosfsmount structure for the filesystem 553 * whose FAT is to be manipulated. 554 * cn - which cluster is of interest 555 * oldcontents - address of a word that is to receive the contents of the 556 * cluster'th entry if this is a get function 557 * newcontents - the new value to be written into the cluster'th element of 558 * the FAT if this is a set function. 559 * 560 * This function can also be used to free a cluster by setting the FAT entry 561 * for a cluster to 0. 562 * 563 * All copies of the FAT are updated if this is a set function. NOTE: If 564 * fatentry() marks a cluster as free it does not update the inusemap in 565 * the msdosfsmount structure. This is left to the caller. 566 */ 567 int 568 msdosfs_fatentry(int function, struct msdosfsmount *pmp, u_long cn, 569 u_long *oldcontents, u_long newcontents) 570 { 571 int error; 572 u_long readcn; 573 u_long bn, bo, bsize, byteoffset; 574 struct buf *bp; 575 576 DPRINTF(("%s(func %d, pmp %p, clust %lu, oldcon %p, newcon " "%lx)\n", 577 __func__, function, pmp, cn, oldcontents, newcontents)); 578 579 #ifdef DIAGNOSTIC 580 /* 581 * Be sure they asked us to do something. 582 */ 583 if ((function & (FAT_SET | FAT_GET)) == 0) { 584 DPRINTF(("%s(): function code doesn't specify get or set\n", 585 __func__)); 586 return (EINVAL); 587 } 588 589 /* 590 * If they asked us to return a cluster number but didn't tell us 591 * where to put it, give them an error. 592 */ 593 if ((function & FAT_GET) && oldcontents == NULL) { 594 DPRINTF(("%s(): get function with no place to put result\n", 595 __func__)); 596 return (EINVAL); 597 } 598 #endif 599 600 /* 601 * Be sure the requested cluster is in the filesystem. 602 */ 603 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 604 return (EINVAL); 605 606 byteoffset = FATOFS(pmp, cn); 607 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 608 if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 609 0, &bp)) != 0) { 610 return (error); 611 } 612 613 if (function & FAT_GET) { 614 if (FAT32(pmp)) 615 readcn = getulong((char *)bp->b_data + bo); 616 else 617 readcn = getushort((char *)bp->b_data + bo); 618 if (FAT12(pmp) & (cn & 1)) 619 readcn >>= 4; 620 readcn &= pmp->pm_fatmask; 621 *oldcontents = readcn; 622 } 623 if (function & FAT_SET) { 624 switch (pmp->pm_fatmask) { 625 case FAT12_MASK: 626 readcn = getushort((char *)bp->b_data + bo); 627 if (cn & 1) { 628 readcn &= 0x000f; 629 readcn |= newcontents << 4; 630 } else { 631 readcn &= 0xf000; 632 readcn |= newcontents & 0xfff; 633 } 634 putushort((char *)bp->b_data + bo, readcn); 635 break; 636 case FAT16_MASK: 637 putushort((char *)bp->b_data + bo, newcontents); 638 break; 639 case FAT32_MASK: 640 /* 641 * According to spec we have to retain the 642 * high order bits of the FAT entry. 643 */ 644 readcn = getulong((char *)bp->b_data + bo); 645 readcn &= ~FAT32_MASK; 646 readcn |= newcontents & FAT32_MASK; 647 putulong((char *)bp->b_data + bo, readcn); 648 break; 649 } 650 updatefats(pmp, bp, bn); 651 bp = NULL; 652 pmp->pm_fmod = 1; 653 } 654 if (bp) 655 brelse(bp, 0); 656 return (0); 657 } 658 659 /* 660 * Update a contiguous cluster chain 661 * 662 * pmp - mount point 663 * start - first cluster of chain 664 * count - number of clusters in chain 665 * fillwith - what to write into FAT entry of last cluster 666 */ 667 static int 668 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 669 { 670 int error; 671 u_long bn, bo, bsize, byteoffset, readcn, newc; 672 struct buf *bp; 673 674 DPRINTF(("%s(pmp %p, start %lu, count %lu, fillwith %lx)\n", __func__, 675 pmp, start, count, fillwith)); 676 /* 677 * Be sure the clusters are in the filesystem. 678 */ 679 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 680 return (EINVAL); 681 682 while (count > 0) { 683 byteoffset = FATOFS(pmp, start); 684 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 685 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 686 B_MODIFY, &bp); 687 if (error) { 688 return (error); 689 } 690 while (count > 0) { 691 start++; 692 newc = --count > 0 ? start : fillwith; 693 switch (pmp->pm_fatmask) { 694 case FAT12_MASK: 695 readcn = getushort((char *)bp->b_data + bo); 696 if (start & 1) { 697 readcn &= 0xf000; 698 readcn |= newc & 0xfff; 699 } else { 700 readcn &= 0x000f; 701 readcn |= newc << 4; 702 } 703 putushort((char *)bp->b_data + bo, readcn); 704 bo++; 705 if (!(start & 1)) 706 bo++; 707 break; 708 case FAT16_MASK: 709 putushort((char *)bp->b_data + bo, newc); 710 bo += 2; 711 break; 712 case FAT32_MASK: 713 readcn = getulong((char *)bp->b_data + bo); 714 readcn &= ~pmp->pm_fatmask; 715 readcn |= newc & pmp->pm_fatmask; 716 putulong((char *)bp->b_data + bo, readcn); 717 bo += 4; 718 break; 719 } 720 if (bo >= bsize) 721 break; 722 } 723 updatefats(pmp, bp, bn); 724 } 725 pmp->pm_fmod = 1; 726 return (0); 727 } 728 729 /* 730 * Check the length of a free cluster chain starting at start. 731 * 732 * pmp - mount point 733 * start - start of chain 734 * count - maximum interesting length 735 */ 736 int 737 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 738 { 739 u_long idx, max_idx; 740 u_int map; 741 u_long len; 742 743 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 744 idx = start / N_INUSEBITS; 745 start %= N_INUSEBITS; 746 map = pmp->pm_inusemap[idx]; 747 map &= ~((1U << start) - 1); 748 if (map) { 749 len = ffs(map) - 1 - start; 750 return (len > count ? count : len); 751 } 752 len = N_INUSEBITS - start; 753 if (len >= count) 754 return (count); 755 while (++idx <= max_idx) { 756 if (len >= count) 757 break; 758 if ((map = pmp->pm_inusemap[idx]) != 0) { 759 len += ffs(map) - 1; 760 break; 761 } 762 len += N_INUSEBITS; 763 } 764 return (len > count ? count : len); 765 } 766 767 /* 768 * Allocate contiguous free clusters. 769 * 770 * pmp - mount point. 771 * start - start of cluster chain. 772 * count - number of clusters to allocate. 773 * fillwith - put this value into the FAT entry for the 774 * last allocated cluster. 775 * retcluster - put the first allocated cluster's number here. 776 * got - how many clusters were actually allocated. 777 */ 778 int 779 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith, u_long *retcluster, u_long *got) 780 { 781 int error; 782 u_long cl, n; 783 784 for (cl = start, n = count; n-- > 0;) 785 usemap_alloc(pmp, cl++); 786 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 787 return (error); 788 789 DPRINTF(("%s(): allocated cluster chain at %lu (%lu clusters)\n", 790 __func__, start, count)); 791 if (retcluster) 792 *retcluster = start; 793 if (got) 794 *got = count; 795 return (0); 796 } 797 798 /* 799 * Allocate contiguous free clusters. 800 * 801 * pmp - mount point. 802 * start - preferred start of cluster chain. 803 * count - number of clusters requested. 804 * fillwith - put this value into the FAT entry for the 805 * last allocated cluster. 806 * retcluster - put the first allocated cluster's number here. 807 * got - how many clusters were actually allocated. 808 */ 809 int 810 msdosfs_clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, 811 u_long *retcluster, u_long *got) 812 { 813 u_long idx; 814 u_long len, newst, foundl, cn, l; 815 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 816 u_long fillwith = CLUST_EOFE; 817 u_int map; 818 819 DPRINTF(("%s(): find %lu clusters\n", __func__, count)); 820 if (start) { 821 if ((len = chainlength(pmp, start, count)) >= count) 822 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 823 } else { 824 /* 825 * This is a new file, initialize start 826 */ 827 struct timeval tv; 828 829 microtime(&tv); 830 start = (tv.tv_usec >> 10) | tv.tv_usec; 831 len = 0; 832 } 833 834 /* 835 * Start at a (pseudo) random place to maximize cluster runs 836 * under multiple writers. 837 */ 838 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 839 foundl = 0; 840 841 for (cn = newst; cn <= pmp->pm_maxcluster;) { 842 idx = cn / N_INUSEBITS; 843 map = pmp->pm_inusemap[idx]; 844 map |= (1U << (cn % N_INUSEBITS)) - 1; 845 if (map != (u_int)-1) { 846 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 847 if ((l = chainlength(pmp, cn, count)) >= count) 848 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 849 if (l > foundl) { 850 foundcn = cn; 851 foundl = l; 852 } 853 cn += l + 1; 854 continue; 855 } 856 cn += N_INUSEBITS - cn % N_INUSEBITS; 857 } 858 for (cn = 0; cn < newst;) { 859 idx = cn / N_INUSEBITS; 860 map = pmp->pm_inusemap[idx]; 861 map |= (1U << (cn % N_INUSEBITS)) - 1; 862 if (map != (u_int)-1) { 863 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 864 if ((l = chainlength(pmp, cn, count)) >= count) 865 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 866 if (l > foundl) { 867 foundcn = cn; 868 foundl = l; 869 } 870 cn += l + 1; 871 continue; 872 } 873 cn += N_INUSEBITS - cn % N_INUSEBITS; 874 } 875 876 if (!foundl) 877 return (ENOSPC); 878 879 if (len) 880 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 881 else 882 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 883 } 884 885 886 /* 887 * Free a chain of clusters. 888 * 889 * pmp - address of the msdosfs mount structure for the filesystem 890 * containing the cluster chain to be freed. 891 * startcluster - number of the 1st cluster in the chain of clusters to be 892 * freed. 893 */ 894 int 895 msdosfs_freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 896 { 897 int error; 898 struct buf *bp = NULL; 899 u_long bn, bo, bsize, byteoffset; 900 u_long readcn, lbn = -1; 901 902 bn = 0; /* XXXgcc */ 903 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 904 byteoffset = FATOFS(pmp, cluster); 905 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 906 if (lbn != bn) { 907 if (bp) 908 updatefats(pmp, bp, lbn); 909 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 910 B_MODIFY, &bp); 911 if (error) { 912 return (error); 913 } 914 lbn = bn; 915 } 916 usemap_free(pmp, cluster); 917 KASSERT(bp != NULL); 918 switch (pmp->pm_fatmask) { 919 case FAT12_MASK: 920 readcn = getushort((char *)bp->b_data + bo); 921 if (cluster & 1) { 922 cluster = readcn >> 4; 923 readcn &= 0x000f; 924 readcn |= MSDOSFSFREE << 4; 925 } else { 926 cluster = readcn; 927 readcn &= 0xf000; 928 readcn |= MSDOSFSFREE & 0xfff; 929 } 930 putushort((char *)bp->b_data + bo, readcn); 931 break; 932 case FAT16_MASK: 933 cluster = getushort((char *)bp->b_data + bo); 934 putushort((char *)bp->b_data + bo, MSDOSFSFREE); 935 break; 936 case FAT32_MASK: 937 cluster = getulong((char *)bp->b_data + bo); 938 putulong((char *)bp->b_data + bo, 939 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 940 break; 941 } 942 cluster &= pmp->pm_fatmask; 943 } 944 if (bp) 945 updatefats(pmp, bp, bn); 946 return (0); 947 } 948 949 /* 950 * Read in FAT blocks looking for free clusters. For every free cluster 951 * found turn off its corresponding bit in the pm_inusemap. 952 */ 953 int 954 msdosfs_fillinusemap(struct msdosfsmount *pmp) 955 { 956 struct buf *bp = NULL; 957 u_long cn, readcn; 958 int error; 959 u_long bn, bo, bsize, byteoffset; 960 961 /* 962 * Mark all clusters in use, we mark the free ones in the FAT scan 963 * loop further down. 964 */ 965 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 966 pmp->pm_inusemap[cn] = (u_int)-1; 967 968 /* 969 * Figure how many free clusters are in the filesystem by ripping 970 * through the FAT counting the number of entries whose content is 971 * zero. These represent free clusters. 972 */ 973 pmp->pm_freeclustercount = 0; 974 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 975 byteoffset = FATOFS(pmp, cn); 976 bo = byteoffset % pmp->pm_fatblocksize; 977 if (!bo || !bp) { 978 /* Read new FAT block */ 979 if (bp) 980 brelse(bp, 0); 981 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 982 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 983 0, &bp); 984 if (error) { 985 return (error); 986 } 987 } 988 if (FAT32(pmp)) 989 readcn = getulong((char *)bp->b_data + bo); 990 else 991 readcn = getushort((char *)bp->b_data + bo); 992 if (FAT12(pmp) && (cn & 1)) 993 readcn >>= 4; 994 readcn &= pmp->pm_fatmask; 995 996 if (readcn == 0) 997 usemap_free(pmp, cn); 998 } 999 if (bp) 1000 brelse(bp, 0); 1001 return (0); 1002 } 1003 1004 /* 1005 * Allocate a new cluster and chain it onto the end of the file. 1006 * 1007 * dep - the file to extend 1008 * count - number of clusters to allocate 1009 * bpp - where to return the address of the buf header for the first new 1010 * file block 1011 * ncp - where to put cluster number of the first newly allocated cluster 1012 * If this pointer is 0, do not return the cluster number. 1013 * flags - see fat.h 1014 * 1015 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 1016 * the de_flag field of the denode and it does not change the de_FileSize 1017 * field. This is left for the caller to do. 1018 */ 1019 1020 int 1021 msdosfs_extendfile(struct denode *dep, u_long count, struct buf **bpp, 1022 u_long *ncp, int flags) 1023 { 1024 int error; 1025 u_long frcn = 0, cn, got; 1026 struct msdosfsmount *pmp = dep->de_pmp; 1027 struct buf *bp; 1028 1029 /* 1030 * Don't try to extend the root directory 1031 */ 1032 if (dep->de_StartCluster == MSDOSFSROOT 1033 && (dep->de_Attributes & ATTR_DIRECTORY)) { 1034 DPRINTF(("%s(): attempt to extend root directory\n", __func__)); 1035 return (ENOSPC); 1036 } 1037 1038 /* 1039 * If the "file's last cluster" cache entry is empty, and the file 1040 * is not empty, then fill the cache entry by calling pcbmap(). 1041 */ 1042 fc_fileextends++; 1043 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1044 dep->de_StartCluster != 0) { 1045 fc_lfcempty++; 1046 error = msdosfs_pcbmap(dep, CLUST_END, 0, &cn, 0); 1047 /* we expect it to return E2BIG */ 1048 if (error != E2BIG) 1049 return (error); 1050 } 1051 1052 fc_last_to_nexttolast(dep); 1053 1054 while (count > 0) { 1055 1056 /* 1057 * Allocate a new cluster chain and cat onto the end of the 1058 * file. If the file is empty we make de_StartCluster point 1059 * to the new block. Note that de_StartCluster being 0 is 1060 * sufficient to be sure the file is empty since we exclude 1061 * attempts to extend the root directory above, and the root 1062 * dir is the only file with a startcluster of 0 that has 1063 * blocks allocated (sort of). 1064 */ 1065 1066 if (dep->de_StartCluster == 0) 1067 cn = 0; 1068 else 1069 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1070 error = msdosfs_clusteralloc(pmp, cn, count, &cn, &got); 1071 if (error) 1072 return (error); 1073 1074 count -= got; 1075 1076 /* 1077 * Give them the filesystem relative cluster number if they want 1078 * it. 1079 */ 1080 if (ncp) { 1081 *ncp = cn; 1082 ncp = NULL; 1083 } 1084 1085 if (dep->de_StartCluster == 0) { 1086 dep->de_StartCluster = cn; 1087 frcn = 0; 1088 } else { 1089 error = msdosfs_fatentry(FAT_SET, pmp, 1090 dep->de_fc[FC_LASTFC].fc_fsrcn, 1091 0, cn); 1092 if (error) { 1093 msdosfs_clusterfree(pmp, cn, NULL); 1094 return (error); 1095 } 1096 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1097 } 1098 1099 /* 1100 * Update the "last cluster of the file" entry in the 1101 * denode's FAT cache. 1102 */ 1103 1104 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1105 if ((flags & DE_CLEAR) && 1106 (dep->de_Attributes & ATTR_DIRECTORY)) { 1107 while (got-- > 0) { 1108 bp = getblk(pmp->pm_devvp, 1109 de_bn2kb(pmp, cntobn(pmp, cn++)), 1110 pmp->pm_bpcluster, 0, 0); 1111 clrbuf(bp); 1112 if (bpp) { 1113 *bpp = bp; 1114 bpp = NULL; 1115 } else { 1116 bdwrite(bp); 1117 } 1118 } 1119 } 1120 } 1121 1122 return (0); 1123 } 1124
Indexes created Mon Sep 22 05:09:51 GMT 2025