1 /* $NetBSD: msdosfs_fat.c,v 1.28 2013/01/28 00:17:18 christos Exp $ */ 2 3 /*- 4 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. 5 * Copyright (C) 1994, 1995, 1997 TooLs GmbH. 6 * All rights reserved. 7 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed by TooLs GmbH. 20 * 4. The name of TooLs GmbH may not be used to endorse or promote products 21 * derived from this software without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR 24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 27 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 28 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 29 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 30 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 31 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 32 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 */ 34 /* 35 * Written by Paul Popelka (paulp@uts.amdahl.com) 36 * 37 * You can do anything you want with this software, just don't say you wrote 38 * it, and don't remove this notice. 39 * 40 * This software is provided "as is". 41 * 42 * The author supplies this software to be publicly redistributed on the 43 * understanding that the author is not responsible for the correct 44 * functioning of this software in any circumstances and is not liable for 45 * any damages caused by this software. 46 * 47 * October 1992 48 */ 49 50 #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 1.28 2013/01/28 00:17:18 christos 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 <ffs/buf.h> 73 #endif 74 75 /* 76 * msdosfs include files. 77 */ 78 #include <fs/msdosfs/bpb.h> 79 #include <fs/msdosfs/msdosfsmount.h> 80 #include <fs/msdosfs/direntry.h> 81 #include <fs/msdosfs/denode.h> 82 #include <fs/msdosfs/fat.h> 83 84 /* 85 * Fat cache stats. 86 */ 87 int fc_fileextends; /* # of file extends */ 88 int fc_lfcempty; /* # of time last file cluster cache entry 89 * was empty */ 90 int fc_bmapcalls; /* # of times pcbmap was called */ 91 92 #define LMMAX 20 93 int fc_lmdistance[LMMAX]; /* counters for how far off the last 94 * cluster mapped entry was. */ 95 int fc_largedistance; /* off by more than LMMAX */ 96 int fc_wherefrom, fc_whereto, fc_lastclust; 97 int pm_fatblocksize; 98 99 #ifdef MSDOSFS_DEBUG 100 #define DPRINTF(a) printf a 101 #else 102 #define DPRINTF(a) 103 #endif 104 #ifdef MSDOSFS_DEBUG 105 void print_fat_stats(void); 106 107 void 108 print_fat_stats(void) 109 { 110 int i; 111 112 printf("fc_fileextends=%d fc_lfcempty=%d fc_bmapcalls=%d " 113 "fc_largedistance=%d [%d->%d=%d] fc_lastclust=%d pm_fatblocksize=%d\n", 114 fc_fileextends, fc_lfcempty, fc_bmapcalls, fc_largedistance, 115 fc_wherefrom, fc_whereto, fc_whereto-fc_wherefrom, 116 fc_lastclust, pm_fatblocksize); 117 118 fc_fileextends = fc_lfcempty = fc_bmapcalls = 0; 119 fc_wherefrom = fc_whereto = fc_lastclust = 0; 120 121 for (i = 0; i < LMMAX; i++) { 122 printf("%d:%d ", i, fc_lmdistance[i]); 123 fc_lmdistance[i] = 0; 124 } 125 126 printf("\n"); 127 } 128 #endif 129 130 static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *, 131 u_long *); 132 void updatefats(struct msdosfsmount *, struct buf *, u_long); 133 static inline void usemap_free(struct msdosfsmount *, u_long); 134 static inline void usemap_alloc(struct msdosfsmount *, u_long); 135 static int fatchain(struct msdosfsmount *, u_long, u_long, u_long); 136 int chainlength(struct msdosfsmount *, u_long, u_long); 137 int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *, 138 u_long *); 139 140 static void 141 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, u_long *bop) 142 { 143 u_long bn, size; 144 145 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 146 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 147 * pmp->pm_BytesPerSec; 148 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 149 150 DPRINTF(("%s(ofs=%lu bn=%lu, size=%lu, bo=%lu)\n", __func__, ofs, bn, 151 size, ofs % pmp->pm_fatblocksize)); 152 if (bnp) 153 *bnp = bn; 154 if (sizep) 155 *sizep = size; 156 if (bop) 157 *bop = ofs % pmp->pm_fatblocksize; 158 159 pm_fatblocksize = pmp->pm_fatblocksize; 160 } 161 162 /* 163 * Map the logical cluster number of a file into a physical disk sector 164 * that is filesystem relative. 165 * 166 * dep - address of denode representing the file of interest 167 * findcn - file relative cluster whose filesystem relative cluster number 168 * and/or block number are/is to be found 169 * bnp - address of where to place the file system relative block number. 170 * If this pointer is null then don't return this quantity. 171 * cnp - address of where to place the file system relative cluster number. 172 * If this pointer is null then don't return this quantity. 173 * 174 * NOTE: Either bnp or cnp must be non-null. 175 * This function has one side effect. If the requested file relative cluster 176 * is beyond the end of file, then the actual number of clusters in the file 177 * is returned in *cnp. This is useful for determining how long a directory is. 178 * If cnp is null, nothing is returned. 179 */ 180 int 181 pcbmap(struct denode *dep, u_long findcn, daddr_t *bnp, u_long *cnp, int *sp) 182 /* findcn: file relative cluster to get */ 183 /* bnp: returned filesys rel sector number */ 184 /* cnp: returned cluster number */ 185 /* sp: returned block size */ 186 { 187 int error; 188 u_long i; 189 u_long cn; 190 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 191 u_long byteoffset; 192 u_long bn; 193 u_long bo; 194 struct buf *bp = NULL; 195 u_long bp_bn = -1; 196 struct msdosfsmount *pmp = dep->de_pmp; 197 u_long bsize; 198 199 fc_bmapcalls++; 200 201 /* 202 * If they don't give us someplace to return a value then don't 203 * bother doing anything. 204 */ 205 if (bnp == NULL && cnp == NULL && sp == NULL) 206 return (0); 207 208 cn = dep->de_StartCluster; 209 DPRINTF(("%s(start cluster=%lu)\n", __func__, cn)); 210 /* 211 * The "file" that makes up the root directory is contiguous, 212 * permanently allocated, of fixed size, and is not made up of 213 * clusters. If the cluster number is beyond the end of the root 214 * directory, then return the number of clusters in the file. 215 */ 216 if (cn == MSDOSFSROOT) { 217 if (dep->de_Attributes & ATTR_DIRECTORY) { 218 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 219 if (cnp) 220 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 221 DPRINTF(("%s(root, %lu ETOOBIG)\n", __func__, 222 de_cn2off(pmp, findcn))); 223 return (E2BIG); 224 } 225 if (bnp) 226 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 227 if (cnp) 228 *cnp = MSDOSFSROOT; 229 if (sp) 230 *sp = min(pmp->pm_bpcluster, 231 dep->de_FileSize - de_cn2off(pmp, findcn)); 232 DPRINTF(("%s(root, bn=%lu, cn=%u)\n", __func__, 233 pmp->pm_rootdirblk + de_cn2bn(pmp, findcn), 234 MSDOSFSROOT)); 235 return (0); 236 } else { /* just an empty file */ 237 if (cnp) 238 *cnp = 0; 239 DPRINTF(("%s(root, empty ETOOBIG)\n", __func__)); 240 return (E2BIG); 241 } 242 } 243 244 /* 245 * All other files do I/O in cluster sized blocks 246 */ 247 if (sp) 248 *sp = pmp->pm_bpcluster; 249 250 /* 251 * Rummage around in the FAT cache, maybe we can avoid tromping 252 * thru every FAT entry for the file. And, keep track of how far 253 * off the cache was from where we wanted to be. 254 */ 255 i = 0; 256 fc_lookup(dep, findcn, &i, &cn); 257 DPRINTF(("%s(bpcluster=%lu i=%lu cn=%lu\n", __func__, pmp->pm_bpcluster, 258 i, cn)); 259 if ((bn = findcn - i) >= LMMAX) { 260 fc_largedistance++; 261 fc_wherefrom = i; 262 fc_whereto = findcn; 263 fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn; 264 } else 265 fc_lmdistance[bn]++; 266 267 /* 268 * Handle all other files or directories the normal way. 269 */ 270 for (; i < findcn; i++) { 271 /* 272 * Stop with all reserved clusters, not just with EOF. 273 */ 274 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask)) 275 goto hiteof; 276 byteoffset = FATOFS(pmp, cn); 277 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 278 if (bn != bp_bn) { 279 if (bp) 280 brelse(bp, 0); 281 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 282 NOCRED, 0, &bp); 283 if (error) { 284 DPRINTF(("%s(bread, %d)\n", __func__, error)); 285 return (error); 286 } 287 bp_bn = bn; 288 } 289 prevcn = cn; 290 if (bo >= bsize) { 291 if (bp) 292 brelse(bp, 0); 293 DPRINTF(("%s(block, %lu >= %lu)\n", __func__, bo, 294 bsize)); 295 return (EIO); 296 } 297 KASSERT(bp != NULL); 298 if (FAT32(pmp)) 299 cn = getulong((char *)bp->b_data + bo); 300 else 301 cn = getushort((char *)bp->b_data + bo); 302 if (FAT12(pmp) && (prevcn & 1)) 303 cn >>= 4; 304 DPRINTF(("%s(cn=%lu masked=%lu)\n", __func__, cn, 305 cn & pmp->pm_fatmask)); 306 cn &= pmp->pm_fatmask; 307 } 308 309 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) { 310 if (bp) 311 brelse(bp, 0); 312 if (bnp) 313 *bnp = cntobn(pmp, cn); 314 if (cnp) 315 *cnp = cn; 316 DPRINTF(("%s(bn=%lu, cn=%lu)\n", __func__, cntobn(pmp, cn), 317 cn)); 318 fc_setcache(dep, FC_LASTMAP, i, cn); 319 return (0); 320 } 321 322 hiteof:; 323 if (cnp) 324 *cnp = i; 325 if (bp) 326 brelse(bp, 0); 327 /* update last file cluster entry in the FAT cache */ 328 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 329 DPRINTF(("%s(eof, %lu)\n", __func__, i)); 330 return (E2BIG); 331 } 332 333 /* 334 * Find the closest entry in the FAT cache to the cluster we are looking 335 * for. 336 */ 337 void 338 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp) 339 { 340 int i; 341 u_long cn; 342 struct fatcache *closest = 0; 343 344 for (i = 0; i < FC_SIZE; i++) { 345 cn = dep->de_fc[i].fc_frcn; 346 if (cn != FCE_EMPTY && cn <= findcn) { 347 if (closest == 0 || cn > closest->fc_frcn) 348 closest = &dep->de_fc[i]; 349 } 350 } 351 if (closest) { 352 *frcnp = closest->fc_frcn; 353 *fsrcnp = closest->fc_fsrcn; 354 } 355 } 356 357 /* 358 * Purge the FAT cache in denode dep of all entries relating to file 359 * relative cluster frcn and beyond. 360 */ 361 void 362 fc_purge(struct denode *dep, u_int frcn) 363 { 364 int i; 365 struct fatcache *fcp; 366 367 fcp = dep->de_fc; 368 for (i = 0; i < FC_SIZE; i++, fcp++) { 369 if (fcp->fc_frcn >= frcn) 370 fcp->fc_frcn = FCE_EMPTY; 371 } 372 } 373 374 /* 375 * Update the FAT. 376 * If mirroring the FAT, update all copies, with the first copy as last. 377 * Else update only the current FAT (ignoring the others). 378 * 379 * pmp - msdosfsmount structure for filesystem to update 380 * bp - addr of modified FAT block 381 * fatbn - block number relative to begin of filesystem of the modified FAT block. 382 */ 383 void 384 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 385 { 386 int i; 387 struct buf *bpn; 388 389 DPRINTF(("%s(pmp %p, bp %p, fatbn %lu)\n", __func__, pmp, bp, fatbn)); 390 391 /* 392 * If we have an FSInfo block, update it. 393 */ 394 if (pmp->pm_fsinfo) { 395 u_long cn = pmp->pm_nxtfree; 396 397 if (pmp->pm_freeclustercount 398 && (pmp->pm_inusemap[cn / N_INUSEBITS] 399 & (1 << (cn % N_INUSEBITS)))) { 400 /* 401 * The cluster indicated in FSInfo isn't free 402 * any longer. Got get a new free one. 403 */ 404 for (cn = 0; cn < pmp->pm_maxcluster; cn++) 405 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 406 break; 407 pmp->pm_nxtfree = cn 408 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 409 ^ (u_int)-1) - 1; 410 } 411 /* 412 * XXX If the fsinfo block is stored on media with 413 * 2KB or larger sectors, is the fsinfo structure 414 * padded at the end or in the middle? 415 */ 416 if (bread(pmp->pm_devvp, de_bn2kb(pmp, pmp->pm_fsinfo), 417 pmp->pm_BytesPerSec, NOCRED, B_MODIFY, &bpn) != 0) { 418 /* 419 * Ignore the error, but turn off FSInfo update for the future. 420 */ 421 pmp->pm_fsinfo = 0; 422 } else { 423 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 424 425 putulong(fp->fsinfree, pmp->pm_freeclustercount); 426 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 427 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 428 bwrite(bpn); 429 else 430 bdwrite(bpn); 431 } 432 } 433 434 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 435 /* 436 * Now copy the block(s) of the modified FAT to the other copies of 437 * the FAT and write them out. This is faster than reading in the 438 * other FATs and then writing them back out. This could tie up 439 * the FAT for quite a while. Preventing others from accessing it. 440 * To prevent us from going after the FAT quite so much we use 441 * delayed writes, unless they specified "synchronous" when the 442 * filesystem was mounted. If synch is asked for then use 443 * bwrite()'s and really slow things down. 444 */ 445 for (i = 1; i < pmp->pm_FATs; i++) { 446 fatbn += pmp->pm_FATsecs; 447 /* getblk() never fails */ 448 bpn = getblk(pmp->pm_devvp, de_bn2kb(pmp, fatbn), 449 bp->b_bcount, 0, 0); 450 memcpy(bpn->b_data, bp->b_data, bp->b_bcount); 451 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 452 bwrite(bpn); 453 else 454 bdwrite(bpn); 455 } 456 } 457 458 /* 459 * Write out the first (or current) FAT last. 460 */ 461 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 462 bwrite(bp); 463 else 464 bdwrite(bp); 465 /* 466 * Maybe update fsinfo sector here? 467 */ 468 } 469 470 /* 471 * Updating entries in 12 bit FATs is a pain in the butt. 472 * 473 * The following picture shows where nibbles go when moving from a 12 bit 474 * cluster number into the appropriate bytes in the FAT. 475 * 476 * byte m byte m+1 byte m+2 477 * +----+----+ +----+----+ +----+----+ 478 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 479 * +----+----+ +----+----+ +----+----+ 480 * 481 * +----+----+----+ +----+----+----+ 482 * | 3 0 1 | | 4 5 2 | 483 * +----+----+----+ +----+----+----+ 484 * cluster n cluster n+1 485 * 486 * Where n is even. m = n + (n >> 2) 487 * 488 */ 489 static inline void 490 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 491 { 492 493 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 494 pmp->pm_freeclustercount--; 495 } 496 497 static inline void 498 usemap_free(struct msdosfsmount *pmp, u_long cn) 499 { 500 501 pmp->pm_freeclustercount++; 502 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 503 } 504 505 int 506 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 507 { 508 int error; 509 u_long oldcn; 510 511 usemap_free(pmp, cluster); 512 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 513 if (error) { 514 usemap_alloc(pmp, cluster); 515 return (error); 516 } 517 /* 518 * If the cluster was successfully marked free, then update 519 * the count of free clusters, and turn off the "allocated" 520 * bit in the "in use" cluster bit map. 521 */ 522 if (oldcnp) 523 *oldcnp = oldcn; 524 return (0); 525 } 526 527 /* 528 * Get or Set or 'Get and Set' the cluster'th entry in the FAT. 529 * 530 * function - whether to get or set a fat entry 531 * pmp - address of the msdosfsmount structure for the filesystem 532 * whose FAT is to be manipulated. 533 * cn - which cluster is of interest 534 * oldcontents - address of a word that is to receive the contents of the 535 * cluster'th entry if this is a get function 536 * newcontents - the new value to be written into the cluster'th element of 537 * the FAT if this is a set function. 538 * 539 * This function can also be used to free a cluster by setting the FAT entry 540 * for a cluster to 0. 541 * 542 * All copies of the FAT are updated if this is a set function. NOTE: If 543 * fatentry() marks a cluster as free it does not update the inusemap in 544 * the msdosfsmount structure. This is left to the caller. 545 */ 546 int 547 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, u_long newcontents) 548 { 549 int error; 550 u_long readcn; 551 u_long bn, bo, bsize, byteoffset; 552 struct buf *bp; 553 554 DPRINTF(("%s(func %d, pmp %p, clust %lu, oldcon %p, newcon " "%lx)\n", 555 __func__, function, pmp, cn, oldcontents, newcontents)); 556 557 #ifdef DIAGNOSTIC 558 /* 559 * Be sure they asked us to do something. 560 */ 561 if ((function & (FAT_SET | FAT_GET)) == 0) { 562 DPRINTF(("%s(): function code doesn't specify get or set\n", 563 __func__)); 564 return (EINVAL); 565 } 566 567 /* 568 * If they asked us to return a cluster number but didn't tell us 569 * where to put it, give them an error. 570 */ 571 if ((function & FAT_GET) && oldcontents == NULL) { 572 DPRINTF(("%s(): get function with no place to put result\n", 573 __func__)); 574 return (EINVAL); 575 } 576 #endif 577 578 /* 579 * Be sure the requested cluster is in the filesystem. 580 */ 581 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 582 return (EINVAL); 583 584 byteoffset = FATOFS(pmp, cn); 585 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 586 if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, NOCRED, 587 0, &bp)) != 0) { 588 return (error); 589 } 590 591 if (function & FAT_GET) { 592 if (FAT32(pmp)) 593 readcn = getulong((char *)bp->b_data + bo); 594 else 595 readcn = getushort((char *)bp->b_data + bo); 596 if (FAT12(pmp) & (cn & 1)) 597 readcn >>= 4; 598 readcn &= pmp->pm_fatmask; 599 *oldcontents = readcn; 600 } 601 if (function & FAT_SET) { 602 switch (pmp->pm_fatmask) { 603 case FAT12_MASK: 604 readcn = getushort((char *)bp->b_data + bo); 605 if (cn & 1) { 606 readcn &= 0x000f; 607 readcn |= newcontents << 4; 608 } else { 609 readcn &= 0xf000; 610 readcn |= newcontents & 0xfff; 611 } 612 putushort((char *)bp->b_data + bo, readcn); 613 break; 614 case FAT16_MASK: 615 putushort((char *)bp->b_data + bo, newcontents); 616 break; 617 case FAT32_MASK: 618 /* 619 * According to spec we have to retain the 620 * high order bits of the FAT entry. 621 */ 622 readcn = getulong((char *)bp->b_data + bo); 623 readcn &= ~FAT32_MASK; 624 readcn |= newcontents & FAT32_MASK; 625 putulong((char *)bp->b_data + bo, readcn); 626 break; 627 } 628 updatefats(pmp, bp, bn); 629 bp = NULL; 630 pmp->pm_fmod = 1; 631 } 632 if (bp) 633 brelse(bp, 0); 634 return (0); 635 } 636 637 /* 638 * Update a contiguous cluster chain 639 * 640 * pmp - mount point 641 * start - first cluster of chain 642 * count - number of clusters in chain 643 * fillwith - what to write into FAT entry of last cluster 644 */ 645 static int 646 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 647 { 648 int error; 649 u_long bn, bo, bsize, byteoffset, readcn, newc; 650 struct buf *bp; 651 652 DPRINTF(("%s(pmp %p, start %lu, count %lu, fillwith %lx)\n", __func__, 653 pmp, start, count, fillwith)); 654 /* 655 * Be sure the clusters are in the filesystem. 656 */ 657 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 658 return (EINVAL); 659 660 while (count > 0) { 661 byteoffset = FATOFS(pmp, start); 662 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 663 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, NOCRED, 664 B_MODIFY, &bp); 665 if (error) { 666 return (error); 667 } 668 while (count > 0) { 669 start++; 670 newc = --count > 0 ? start : fillwith; 671 switch (pmp->pm_fatmask) { 672 case FAT12_MASK: 673 readcn = getushort((char *)bp->b_data + bo); 674 if (start & 1) { 675 readcn &= 0xf000; 676 readcn |= newc & 0xfff; 677 } else { 678 readcn &= 0x000f; 679 readcn |= newc << 4; 680 } 681 putushort((char *)bp->b_data + bo, readcn); 682 bo++; 683 if (!(start & 1)) 684 bo++; 685 break; 686 case FAT16_MASK: 687 putushort((char *)bp->b_data + bo, newc); 688 bo += 2; 689 break; 690 case FAT32_MASK: 691 readcn = getulong((char *)bp->b_data + bo); 692 readcn &= ~pmp->pm_fatmask; 693 readcn |= newc & pmp->pm_fatmask; 694 putulong((char *)bp->b_data + bo, readcn); 695 bo += 4; 696 break; 697 } 698 if (bo >= bsize) 699 break; 700 } 701 updatefats(pmp, bp, bn); 702 } 703 pmp->pm_fmod = 1; 704 return (0); 705 } 706 707 /* 708 * Check the length of a free cluster chain starting at start. 709 * 710 * pmp - mount point 711 * start - start of chain 712 * count - maximum interesting length 713 */ 714 int 715 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 716 { 717 u_long idx, max_idx; 718 u_int map; 719 u_long len; 720 721 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 722 idx = start / N_INUSEBITS; 723 start %= N_INUSEBITS; 724 map = pmp->pm_inusemap[idx]; 725 map &= ~((1 << start) - 1); 726 if (map) { 727 len = ffs(map) - 1 - start; 728 return (len > count ? count : len); 729 } 730 len = N_INUSEBITS - start; 731 if (len >= count) 732 return (count); 733 while (++idx <= max_idx) { 734 if (len >= count) 735 break; 736 if ((map = pmp->pm_inusemap[idx]) != 0) { 737 len += ffs(map) - 1; 738 break; 739 } 740 len += N_INUSEBITS; 741 } 742 return (len > count ? count : len); 743 } 744 745 /* 746 * Allocate contigous free clusters. 747 * 748 * pmp - mount point. 749 * start - start of cluster chain. 750 * count - number of clusters to allocate. 751 * fillwith - put this value into the FAT entry for the 752 * last allocated cluster. 753 * retcluster - put the first allocated cluster's number here. 754 * got - how many clusters were actually allocated. 755 */ 756 int 757 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith, u_long *retcluster, u_long *got) 758 { 759 int error; 760 u_long cl, n; 761 762 for (cl = start, n = count; n-- > 0;) 763 usemap_alloc(pmp, cl++); 764 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 765 return (error); 766 767 DPRINTF(("%s(): allocated cluster chain at %lu (%lu clusters)\n", 768 __func__, start, count)); 769 if (retcluster) 770 *retcluster = start; 771 if (got) 772 *got = count; 773 return (0); 774 } 775 776 /* 777 * Allocate contiguous free clusters. 778 * 779 * pmp - mount point. 780 * start - preferred start of cluster chain. 781 * count - number of clusters requested. 782 * fillwith - put this value into the FAT entry for the 783 * last allocated cluster. 784 * retcluster - put the first allocated cluster's number here. 785 * got - how many clusters were actually allocated. 786 */ 787 int 788 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, u_long *retcluster, u_long *got) 789 { 790 u_long idx; 791 u_long len, newst, foundl, cn, l; 792 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 793 u_long fillwith = CLUST_EOFE; 794 u_int map; 795 796 DPRINTF(("%s(): find %lu clusters\n", __func__, count)); 797 if (start) { 798 if ((len = chainlength(pmp, start, count)) >= count) 799 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 800 } else { 801 /* 802 * This is a new file, initialize start 803 */ 804 struct timeval tv; 805 806 microtime(&tv); 807 start = (tv.tv_usec >> 10) | tv.tv_usec; 808 len = 0; 809 } 810 811 /* 812 * Start at a (pseudo) random place to maximize cluster runs 813 * under multiple writers. 814 */ 815 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 816 foundl = 0; 817 818 for (cn = newst; cn <= pmp->pm_maxcluster;) { 819 idx = cn / N_INUSEBITS; 820 map = pmp->pm_inusemap[idx]; 821 map |= (1 << (cn % N_INUSEBITS)) - 1; 822 if (map != (u_int)-1) { 823 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 824 if ((l = chainlength(pmp, cn, count)) >= count) 825 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 826 if (l > foundl) { 827 foundcn = cn; 828 foundl = l; 829 } 830 cn += l + 1; 831 continue; 832 } 833 cn += N_INUSEBITS - cn % N_INUSEBITS; 834 } 835 for (cn = 0; cn < newst;) { 836 idx = cn / N_INUSEBITS; 837 map = pmp->pm_inusemap[idx]; 838 map |= (1 << (cn % N_INUSEBITS)) - 1; 839 if (map != (u_int)-1) { 840 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 841 if ((l = chainlength(pmp, cn, count)) >= count) 842 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 843 if (l > foundl) { 844 foundcn = cn; 845 foundl = l; 846 } 847 cn += l + 1; 848 continue; 849 } 850 cn += N_INUSEBITS - cn % N_INUSEBITS; 851 } 852 853 if (!foundl) 854 return (ENOSPC); 855 856 if (len) 857 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 858 else 859 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 860 } 861 862 863 /* 864 * Free a chain of clusters. 865 * 866 * pmp - address of the msdosfs mount structure for the filesystem 867 * containing the cluster chain to be freed. 868 * startcluster - number of the 1st cluster in the chain of clusters to be 869 * freed. 870 */ 871 int 872 freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 873 { 874 int error; 875 struct buf *bp = NULL; 876 u_long bn, bo, bsize, byteoffset; 877 u_long readcn, lbn = -1; 878 879 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 880 byteoffset = FATOFS(pmp, cluster); 881 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 882 if (lbn != bn) { 883 if (bp) 884 updatefats(pmp, bp, lbn); 885 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 886 NOCRED, B_MODIFY, &bp); 887 if (error) { 888 return (error); 889 } 890 lbn = bn; 891 } 892 usemap_free(pmp, cluster); 893 KASSERT(bp != NULL); 894 switch (pmp->pm_fatmask) { 895 case FAT12_MASK: 896 readcn = getushort((char *)bp->b_data + bo); 897 if (cluster & 1) { 898 cluster = readcn >> 4; 899 readcn &= 0x000f; 900 readcn |= MSDOSFSFREE << 4; 901 } else { 902 cluster = readcn; 903 readcn &= 0xf000; 904 readcn |= MSDOSFSFREE & 0xfff; 905 } 906 putushort((char *)bp->b_data + bo, readcn); 907 break; 908 case FAT16_MASK: 909 cluster = getushort((char *)bp->b_data + bo); 910 putushort((char *)bp->b_data + bo, MSDOSFSFREE); 911 break; 912 case FAT32_MASK: 913 cluster = getulong((char *)bp->b_data + bo); 914 putulong((char *)bp->b_data + bo, 915 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 916 break; 917 } 918 cluster &= pmp->pm_fatmask; 919 } 920 if (bp) 921 updatefats(pmp, bp, bn); 922 return (0); 923 } 924 925 /* 926 * Read in FAT blocks looking for free clusters. For every free cluster 927 * found turn off its corresponding bit in the pm_inusemap. 928 */ 929 int 930 fillinusemap(struct msdosfsmount *pmp) 931 { 932 struct buf *bp = NULL; 933 u_long cn, readcn; 934 int error; 935 u_long bn, bo, bsize, byteoffset; 936 937 /* 938 * Mark all clusters in use, we mark the free ones in the FAT scan 939 * loop further down. 940 */ 941 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 942 pmp->pm_inusemap[cn] = (u_int)-1; 943 944 /* 945 * Figure how many free clusters are in the filesystem by ripping 946 * through the FAT counting the number of entries whose content is 947 * zero. These represent free clusters. 948 */ 949 pmp->pm_freeclustercount = 0; 950 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 951 byteoffset = FATOFS(pmp, cn); 952 bo = byteoffset % pmp->pm_fatblocksize; 953 if (!bo || !bp) { 954 /* Read new FAT block */ 955 if (bp) 956 brelse(bp, 0); 957 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 958 error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, 959 NOCRED, 0, &bp); 960 if (error) { 961 return (error); 962 } 963 } 964 if (FAT32(pmp)) 965 readcn = getulong((char *)bp->b_data + bo); 966 else 967 readcn = getushort((char *)bp->b_data + bo); 968 if (FAT12(pmp) && (cn & 1)) 969 readcn >>= 4; 970 readcn &= pmp->pm_fatmask; 971 972 if (readcn == 0) 973 usemap_free(pmp, cn); 974 } 975 if (bp) 976 brelse(bp, 0); 977 return (0); 978 } 979 980 /* 981 * Allocate a new cluster and chain it onto the end of the file. 982 * 983 * dep - the file to extend 984 * count - number of clusters to allocate 985 * bpp - where to return the address of the buf header for the first new 986 * file block 987 * ncp - where to put cluster number of the first newly allocated cluster 988 * If this pointer is 0, do not return the cluster number. 989 * flags - see fat.h 990 * 991 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 992 * the de_flag field of the denode and it does not change the de_FileSize 993 * field. This is left for the caller to do. 994 */ 995 996 int 997 extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, int flags) 998 { 999 int error; 1000 u_long frcn = 0, cn, got; 1001 struct msdosfsmount *pmp = dep->de_pmp; 1002 struct buf *bp; 1003 1004 /* 1005 * Don't try to extend the root directory 1006 */ 1007 if (dep->de_StartCluster == MSDOSFSROOT 1008 && (dep->de_Attributes & ATTR_DIRECTORY)) { 1009 DPRINTF(("%s(): attempt to extend root directory\n", __func__)); 1010 return (ENOSPC); 1011 } 1012 1013 /* 1014 * If the "file's last cluster" cache entry is empty, and the file 1015 * is not empty, then fill the cache entry by calling pcbmap(). 1016 */ 1017 fc_fileextends++; 1018 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1019 dep->de_StartCluster != 0) { 1020 fc_lfcempty++; 1021 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 1022 /* we expect it to return E2BIG */ 1023 if (error != E2BIG) 1024 return (error); 1025 } 1026 1027 fc_last_to_nexttolast(dep); 1028 1029 while (count > 0) { 1030 1031 /* 1032 * Allocate a new cluster chain and cat onto the end of the 1033 * file. If the file is empty we make de_StartCluster point 1034 * to the new block. Note that de_StartCluster being 0 is 1035 * sufficient to be sure the file is empty since we exclude 1036 * attempts to extend the root directory above, and the root 1037 * dir is the only file with a startcluster of 0 that has 1038 * blocks allocated (sort of). 1039 */ 1040 1041 if (dep->de_StartCluster == 0) 1042 cn = 0; 1043 else 1044 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1045 error = clusteralloc(pmp, cn, count, &cn, &got); 1046 if (error) 1047 return (error); 1048 1049 count -= got; 1050 1051 /* 1052 * Give them the filesystem relative cluster number if they want 1053 * it. 1054 */ 1055 if (ncp) { 1056 *ncp = cn; 1057 ncp = NULL; 1058 } 1059 1060 if (dep->de_StartCluster == 0) { 1061 dep->de_StartCluster = cn; 1062 frcn = 0; 1063 } else { 1064 error = fatentry(FAT_SET, pmp, 1065 dep->de_fc[FC_LASTFC].fc_fsrcn, 1066 0, cn); 1067 if (error) { 1068 clusterfree(pmp, cn, NULL); 1069 return (error); 1070 } 1071 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1072 } 1073 1074 /* 1075 * Update the "last cluster of the file" entry in the 1076 * denode's FAT cache. 1077 */ 1078 1079 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1080 if ((flags & DE_CLEAR) && 1081 (dep->de_Attributes & ATTR_DIRECTORY)) { 1082 while (got-- > 0) { 1083 bp = getblk(pmp->pm_devvp, 1084 de_bn2kb(pmp, cntobn(pmp, cn++)), 1085 pmp->pm_bpcluster, 0, 0); 1086 clrbuf(bp); 1087 if (bpp) { 1088 *bpp = bp; 1089 bpp = NULL; 1090 } else { 1091 bdwrite(bp); 1092 } 1093 } 1094 } 1095 } 1096 1097 return (0); 1098 } 1099