1 /* $FreeBSD: src/sys/msdosfs/msdosfs_fat.c,v 1.23 2000/01/27 14:43:06 nyan Exp $ */ 2 /* $DragonFly: src/sys/vfs/msdosfs/msdosfs_fat.c,v 1.6 2004/04/17 00:30:17 cpressey Exp $ */ 3 /* $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $ */ 4 5 /*- 6 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. 7 * Copyright (C) 1994, 1995, 1997 TooLs GmbH. 8 * All rights reserved. 9 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by TooLs GmbH. 22 * 4. The name of TooLs GmbH may not be used to endorse or promote products 23 * derived from this software without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR 26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 29 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 30 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 31 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 32 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 33 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 34 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35 */ 36 /* 37 * Written by Paul Popelka (paulp@uts.amdahl.com) 38 * 39 * You can do anything you want with this software, just don't say you wrote 40 * it, and don't remove this notice. 41 * 42 * This software is provided "as is". 43 * 44 * The author supplies this software to be publicly redistributed on the 45 * understanding that the author is not responsible for the correct 46 * functioning of this software in any circumstances and is not liable for 47 * any damages caused by this software. 48 * 49 * October 1992 50 */ 51 52 /* 53 * kernel include files. 54 */ 55 #include <sys/param.h> 56 #include <sys/systm.h> 57 #include <sys/buf.h> 58 #include <sys/mount.h> /* to define statfs structure */ 59 #include <sys/vnode.h> /* to define vattr structure */ 60 61 /* 62 * msdosfs include files. 63 */ 64 #include "bpb.h" 65 #include "msdosfsmount.h" 66 #include "direntry.h" 67 #include "denode.h" 68 #include "fat.h" 69 70 /* 71 * Fat cache stats. 72 */ 73 static int fc_fileextends; /* # of file extends */ 74 static int fc_lfcempty; /* # of time last file cluster cache entry 75 * was empty */ 76 static int fc_bmapcalls; /* # of times pcbmap was called */ 77 78 #define LMMAX 20 79 static int fc_lmdistance[LMMAX];/* counters for how far off the last 80 * cluster mapped entry was. */ 81 static int fc_largedistance; /* off by more than LMMAX */ 82 83 static int chainalloc (struct msdosfsmount *pmp, u_long start, 84 u_long count, u_long fillwith, 85 u_long *retcluster, u_long *got); 86 static int chainlength (struct msdosfsmount *pmp, u_long start, 87 u_long count); 88 static void fatblock (struct msdosfsmount *pmp, u_long ofs, 89 u_long *bnp, u_long *sizep, u_long *bop); 90 static int fatchain (struct msdosfsmount *pmp, u_long start, 91 u_long count, u_long fillwith); 92 static void fc_lookup (struct denode *dep, u_long findcn, 93 u_long *frcnp, u_long *fsrcnp); 94 static void updatefats (struct msdosfsmount *pmp, struct buf *bp, 95 u_long fatbn); 96 static __inline void 97 usemap_alloc (struct msdosfsmount *pmp, u_long cn); 98 static __inline void 99 usemap_free (struct msdosfsmount *pmp, u_long cn); 100 101 static void 102 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, 103 u_long *bop) 104 { 105 u_long bn, size; 106 107 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 108 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 109 * DEV_BSIZE; 110 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 111 112 if (bnp) 113 *bnp = bn; 114 if (sizep) 115 *sizep = size; 116 if (bop) 117 *bop = ofs % pmp->pm_fatblocksize; 118 } 119 120 /* 121 * Map the logical cluster number of a file into a physical disk sector 122 * that is filesystem relative. 123 * 124 * dep - address of denode representing the file of interest 125 * findcn - file relative cluster whose filesystem relative cluster number 126 * and/or block number are/is to be found 127 * bnp - address of where to place the file system relative block number. 128 * If this pointer is null then don't return this quantity. 129 * cnp - address of where to place the file system relative cluster number. 130 * If this pointer is null then don't return this quantity. 131 * 132 * NOTE: Either bnp or cnp must be non-null. 133 * This function has one side effect. If the requested file relative cluster 134 * is beyond the end of file, then the actual number of clusters in the file 135 * is returned in *cnp. This is useful for determining how long a directory is. 136 * If cnp is null, nothing is returned. 137 */ 138 int 139 pcbmap(struct denode *dep, 140 u_long findcn, /* file relative cluster to get */ 141 daddr_t *bnp, /* returned filesys relative blk number */ 142 u_long *cnp, /* returned cluster number */ 143 int *sp) /* returned block size */ 144 { 145 int error; 146 u_long i; 147 u_long cn; 148 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 149 u_long byteoffset; 150 u_long bn; 151 u_long bo; 152 struct buf *bp = NULL; 153 u_long bp_bn = -1; 154 struct msdosfsmount *pmp = dep->de_pmp; 155 u_long bsize; 156 157 fc_bmapcalls++; 158 159 /* 160 * If they don't give us someplace to return a value then don't 161 * bother doing anything. 162 */ 163 if (bnp == NULL && cnp == NULL && sp == NULL) 164 return (0); 165 166 cn = dep->de_StartCluster; 167 /* 168 * The "file" that makes up the root directory is contiguous, 169 * permanently allocated, of fixed size, and is not made up of 170 * clusters. If the cluster number is beyond the end of the root 171 * directory, then return the number of clusters in the file. 172 */ 173 if (cn == MSDOSFSROOT) { 174 if (dep->de_Attributes & ATTR_DIRECTORY) { 175 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 176 if (cnp) 177 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 178 return (E2BIG); 179 } 180 if (bnp) 181 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 182 if (cnp) 183 *cnp = MSDOSFSROOT; 184 if (sp) 185 *sp = min(pmp->pm_bpcluster, 186 dep->de_FileSize - de_cn2off(pmp, findcn)); 187 return (0); 188 } else { /* just an empty file */ 189 if (cnp) 190 *cnp = 0; 191 return (E2BIG); 192 } 193 } 194 195 /* 196 * All other files do I/O in cluster sized blocks 197 */ 198 if (sp) 199 *sp = pmp->pm_bpcluster; 200 201 /* 202 * Rummage around in the fat cache, maybe we can avoid tromping 203 * thru every fat entry for the file. And, keep track of how far 204 * off the cache was from where we wanted to be. 205 */ 206 i = 0; 207 fc_lookup(dep, findcn, &i, &cn); 208 if ((bn = findcn - i) >= LMMAX) 209 fc_largedistance++; 210 else 211 fc_lmdistance[bn]++; 212 213 /* 214 * Handle all other files or directories the normal way. 215 */ 216 for (; i < findcn; i++) { 217 /* 218 * Stop with all reserved clusters, not just with EOF. 219 */ 220 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 221 goto hiteof; 222 byteoffset = FATOFS(pmp, cn); 223 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 224 if (bn != bp_bn) { 225 if (bp) 226 brelse(bp); 227 error = bread(pmp->pm_devvp, bn, bsize, &bp); 228 if (error) { 229 brelse(bp); 230 return (error); 231 } 232 bp_bn = bn; 233 } 234 prevcn = cn; 235 if (FAT32(pmp)) 236 cn = getulong(&bp->b_data[bo]); 237 else 238 cn = getushort(&bp->b_data[bo]); 239 if (FAT12(pmp) && (prevcn & 1)) 240 cn >>= 4; 241 cn &= pmp->pm_fatmask; 242 243 /* 244 * Force the special cluster numbers 245 * to be the same for all cluster sizes 246 * to let the rest of msdosfs handle 247 * all cases the same. 248 */ 249 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 250 cn |= ~pmp->pm_fatmask; 251 } 252 253 if (!MSDOSFSEOF(pmp, cn)) { 254 if (bp) 255 brelse(bp); 256 if (bnp) 257 *bnp = cntobn(pmp, cn); 258 if (cnp) 259 *cnp = cn; 260 fc_setcache(dep, FC_LASTMAP, i, cn); 261 return (0); 262 } 263 264 hiteof:; 265 if (cnp) 266 *cnp = i; 267 if (bp) 268 brelse(bp); 269 /* update last file cluster entry in the fat cache */ 270 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 271 return (E2BIG); 272 } 273 274 /* 275 * Find the closest entry in the fat cache to the cluster we are looking 276 * for. 277 */ 278 static void 279 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp) 280 { 281 int i; 282 u_long cn; 283 struct fatcache *closest = 0; 284 285 for (i = 0; i < FC_SIZE; i++) { 286 cn = dep->de_fc[i].fc_frcn; 287 if (cn != FCE_EMPTY && cn <= findcn) { 288 if (closest == 0 || cn > closest->fc_frcn) 289 closest = &dep->de_fc[i]; 290 } 291 } 292 if (closest) { 293 *frcnp = closest->fc_frcn; 294 *fsrcnp = closest->fc_fsrcn; 295 } 296 } 297 298 /* 299 * Purge the fat cache in denode dep of all entries relating to file 300 * relative cluster frcn and beyond. 301 */ 302 void 303 fc_purge(struct denode *dep, u_int frcn) 304 { 305 int i; 306 struct fatcache *fcp; 307 308 fcp = dep->de_fc; 309 for (i = 0; i < FC_SIZE; i++, fcp++) { 310 if (fcp->fc_frcn >= frcn) 311 fcp->fc_frcn = FCE_EMPTY; 312 } 313 } 314 315 /* 316 * Update the fat. 317 * If mirroring the fat, update all copies, with the first copy as last. 318 * Else update only the current fat (ignoring the others). 319 * 320 * pmp - msdosfsmount structure for filesystem to update 321 * bp - addr of modified fat block 322 * fatbn - block number relative to begin of filesystem of the modified fat block. 323 */ 324 static void 325 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 326 { 327 int i; 328 struct buf *bpn; 329 330 #ifdef MSDOSFS_DEBUG 331 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn); 332 #endif 333 334 /* 335 * If we have an FSInfo block, update it. 336 */ 337 if (pmp->pm_fsinfo) { 338 u_long cn = pmp->pm_nxtfree; 339 340 if (pmp->pm_freeclustercount 341 && (pmp->pm_inusemap[cn / N_INUSEBITS] 342 & (1 << (cn % N_INUSEBITS)))) { 343 /* 344 * The cluster indicated in FSInfo isn't free 345 * any longer. Got get a new free one. 346 */ 347 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS) 348 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 349 break; 350 pmp->pm_nxtfree = cn 351 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 352 ^ (u_int)-1) - 1; 353 } 354 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), &bpn) != 0) { 355 /* 356 * Ignore the error, but turn off FSInfo update for the future. 357 */ 358 pmp->pm_fsinfo = 0; 359 brelse(bpn); 360 } else { 361 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 362 363 putulong(fp->fsinfree, pmp->pm_freeclustercount); 364 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 365 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 366 bwrite(bpn); 367 else 368 bdwrite(bpn); 369 } 370 } 371 372 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 373 /* 374 * Now copy the block(s) of the modified fat to the other copies of 375 * the fat and write them out. This is faster than reading in the 376 * other fats and then writing them back out. This could tie up 377 * the fat for quite a while. Preventing others from accessing it. 378 * To prevent us from going after the fat quite so much we use 379 * delayed writes, unless they specfied "synchronous" when the 380 * filesystem was mounted. If synch is asked for then use 381 * bwrite()'s and really slow things down. 382 */ 383 for (i = 1; i < pmp->pm_FATs; i++) { 384 fatbn += pmp->pm_FATsecs; 385 /* getblk() never fails */ 386 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 387 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 388 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 389 bwrite(bpn); 390 else 391 bdwrite(bpn); 392 } 393 } 394 395 /* 396 * Write out the first (or current) fat last. 397 */ 398 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 399 bwrite(bp); 400 else 401 bdwrite(bp); 402 /* 403 * Maybe update fsinfo sector here? 404 */ 405 } 406 407 /* 408 * Updating entries in 12 bit fats is a pain in the butt. 409 * 410 * The following picture shows where nibbles go when moving from a 12 bit 411 * cluster number into the appropriate bytes in the FAT. 412 * 413 * byte m byte m+1 byte m+2 414 * +----+----+ +----+----+ +----+----+ 415 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 416 * +----+----+ +----+----+ +----+----+ 417 * 418 * +----+----+----+ +----+----+----+ 419 * | 3 0 1 | | 4 5 2 | 420 * +----+----+----+ +----+----+----+ 421 * cluster n cluster n+1 422 * 423 * Where n is even. m = n + (n >> 2) 424 * 425 */ 426 static __inline void 427 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 428 { 429 430 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 431 pmp->pm_freeclustercount--; 432 } 433 434 static __inline void 435 usemap_free(struct msdosfsmount *pmp, u_long cn) 436 { 437 438 pmp->pm_freeclustercount++; 439 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 440 } 441 442 int 443 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 444 { 445 int error; 446 u_long oldcn; 447 448 usemap_free(pmp, cluster); 449 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 450 if (error) { 451 usemap_alloc(pmp, cluster); 452 return (error); 453 } 454 /* 455 * If the cluster was successfully marked free, then update 456 * the count of free clusters, and turn off the "allocated" 457 * bit in the "in use" cluster bit map. 458 */ 459 if (oldcnp) 460 *oldcnp = oldcn; 461 return (0); 462 } 463 464 /* 465 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 466 * 467 * function - whether to get or set a fat entry 468 * pmp - address of the msdosfsmount structure for the filesystem 469 * whose fat is to be manipulated. 470 * cn - which cluster is of interest 471 * oldcontents - address of a word that is to receive the contents of the 472 * cluster'th entry if this is a get function 473 * newcontents - the new value to be written into the cluster'th element of 474 * the fat if this is a set function. 475 * 476 * This function can also be used to free a cluster by setting the fat entry 477 * for a cluster to 0. 478 * 479 * All copies of the fat are updated if this is a set function. NOTE: If 480 * fatentry() marks a cluster as free it does not update the inusemap in 481 * the msdosfsmount structure. This is left to the caller. 482 */ 483 int 484 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, 485 u_long newcontents) 486 { 487 int error; 488 u_long readcn; 489 u_long bn, bo, bsize, byteoffset; 490 struct buf *bp; 491 492 #ifdef MSDOSFS_DEBUG 493 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 494 function, pmp, cn, oldcontents, newcontents); 495 #endif 496 497 #ifdef DIAGNOSTIC 498 /* 499 * Be sure they asked us to do something. 500 */ 501 if ((function & (FAT_SET | FAT_GET)) == 0) { 502 printf("fatentry(): function code doesn't specify get or set\n"); 503 return (EINVAL); 504 } 505 506 /* 507 * If they asked us to return a cluster number but didn't tell us 508 * where to put it, give them an error. 509 */ 510 if ((function & FAT_GET) && oldcontents == NULL) { 511 printf("fatentry(): get function with no place to put result\n"); 512 return (EINVAL); 513 } 514 #endif 515 516 /* 517 * Be sure the requested cluster is in the filesystem. 518 */ 519 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 520 return (EINVAL); 521 522 byteoffset = FATOFS(pmp, cn); 523 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 524 error = bread(pmp->pm_devvp, bn, bsize, &bp); 525 if (error) { 526 brelse(bp); 527 return (error); 528 } 529 530 if (function & FAT_GET) { 531 if (FAT32(pmp)) 532 readcn = getulong(&bp->b_data[bo]); 533 else 534 readcn = getushort(&bp->b_data[bo]); 535 if (FAT12(pmp) & (cn & 1)) 536 readcn >>= 4; 537 readcn &= pmp->pm_fatmask; 538 /* map reserved fat entries to same values for all fats */ 539 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 540 readcn |= ~pmp->pm_fatmask; 541 *oldcontents = readcn; 542 } 543 if (function & FAT_SET) { 544 switch (pmp->pm_fatmask) { 545 case FAT12_MASK: 546 readcn = getushort(&bp->b_data[bo]); 547 if (cn & 1) { 548 readcn &= 0x000f; 549 readcn |= newcontents << 4; 550 } else { 551 readcn &= 0xf000; 552 readcn |= newcontents & 0xfff; 553 } 554 putushort(&bp->b_data[bo], readcn); 555 break; 556 case FAT16_MASK: 557 putushort(&bp->b_data[bo], newcontents); 558 break; 559 case FAT32_MASK: 560 /* 561 * According to spec we have to retain the 562 * high order bits of the fat entry. 563 */ 564 readcn = getulong(&bp->b_data[bo]); 565 readcn &= ~FAT32_MASK; 566 readcn |= newcontents & FAT32_MASK; 567 putulong(&bp->b_data[bo], readcn); 568 break; 569 } 570 updatefats(pmp, bp, bn); 571 bp = NULL; 572 pmp->pm_fmod = 1; 573 } 574 if (bp) 575 brelse(bp); 576 return (0); 577 } 578 579 /* 580 * Update a contiguous cluster chain 581 * 582 * pmp - mount point 583 * start - first cluster of chain 584 * count - number of clusters in chain 585 * fillwith - what to write into fat entry of last cluster 586 */ 587 static int 588 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 589 { 590 int error; 591 u_long bn, bo, bsize, byteoffset, readcn, newc; 592 struct buf *bp; 593 594 #ifdef MSDOSFS_DEBUG 595 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 596 pmp, start, count, fillwith); 597 #endif 598 /* 599 * Be sure the clusters are in the filesystem. 600 */ 601 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 602 return (EINVAL); 603 604 while (count > 0) { 605 byteoffset = FATOFS(pmp, start); 606 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 607 error = bread(pmp->pm_devvp, bn, bsize, &bp); 608 if (error) { 609 brelse(bp); 610 return (error); 611 } 612 while (count > 0) { 613 start++; 614 newc = --count > 0 ? start : fillwith; 615 switch (pmp->pm_fatmask) { 616 case FAT12_MASK: 617 readcn = getushort(&bp->b_data[bo]); 618 if (start & 1) { 619 readcn &= 0xf000; 620 readcn |= newc & 0xfff; 621 } else { 622 readcn &= 0x000f; 623 readcn |= newc << 4; 624 } 625 putushort(&bp->b_data[bo], readcn); 626 bo++; 627 if (!(start & 1)) 628 bo++; 629 break; 630 case FAT16_MASK: 631 putushort(&bp->b_data[bo], newc); 632 bo += 2; 633 break; 634 case FAT32_MASK: 635 readcn = getulong(&bp->b_data[bo]); 636 readcn &= ~pmp->pm_fatmask; 637 readcn |= newc & pmp->pm_fatmask; 638 putulong(&bp->b_data[bo], readcn); 639 bo += 4; 640 break; 641 } 642 if (bo >= bsize) 643 break; 644 } 645 updatefats(pmp, bp, bn); 646 } 647 pmp->pm_fmod = 1; 648 return (0); 649 } 650 651 /* 652 * Check the length of a free cluster chain starting at start. 653 * 654 * pmp - mount point 655 * start - start of chain 656 * count - maximum interesting length 657 */ 658 static int 659 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 660 { 661 u_long idx, max_idx; 662 u_int map; 663 u_long len; 664 665 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 666 idx = start / N_INUSEBITS; 667 start %= N_INUSEBITS; 668 map = pmp->pm_inusemap[idx]; 669 map &= ~((1 << start) - 1); 670 if (map) { 671 len = ffs(map) - 1 - start; 672 return (len > count ? count : len); 673 } 674 len = N_INUSEBITS - start; 675 if (len >= count) 676 return (count); 677 while (++idx <= max_idx) { 678 if (len >= count) 679 break; 680 map = pmp->pm_inusemap[idx]; 681 if (map) { 682 len += ffs(map) - 1; 683 break; 684 } 685 len += N_INUSEBITS; 686 } 687 return (len > count ? count : len); 688 } 689 690 /* 691 * Allocate contigous free clusters. 692 * 693 * pmp - mount point. 694 * start - start of cluster chain. 695 * count - number of clusters to allocate. 696 * fillwith - put this value into the fat entry for the 697 * last allocated cluster. 698 * retcluster - put the first allocated cluster's number here. 699 * got - how many clusters were actually allocated. 700 */ 701 static int 702 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, 703 u_long fillwith, u_long *retcluster, u_long *got) 704 { 705 int error; 706 u_long cl, n; 707 708 for (cl = start, n = count; n-- > 0;) 709 usemap_alloc(pmp, cl++); 710 711 error = fatchain(pmp, start, count, fillwith); 712 if (error != 0) 713 return (error); 714 #ifdef MSDOSFS_DEBUG 715 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 716 start, count); 717 #endif 718 if (retcluster) 719 *retcluster = start; 720 if (got) 721 *got = count; 722 return (0); 723 } 724 725 /* 726 * Allocate contiguous free clusters. 727 * 728 * pmp - mount point. 729 * start - preferred start of cluster chain. 730 * count - number of clusters requested. 731 * fillwith - put this value into the fat entry for the 732 * last allocated cluster. 733 * retcluster - put the first allocated cluster's number here. 734 * got - how many clusters were actually allocated. 735 */ 736 int 737 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, 738 u_long fillwith, u_long *retcluster, u_long *got) 739 { 740 u_long idx; 741 u_long len, newst, foundl, cn, l; 742 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 743 u_int map; 744 745 #ifdef MSDOSFS_DEBUG 746 printf("clusteralloc(): find %lu clusters\n",count); 747 #endif 748 if (start) { 749 if ((len = chainlength(pmp, start, count)) >= count) 750 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 751 } else 752 len = 0; 753 754 /* 755 * Start at a (pseudo) random place to maximize cluster runs 756 * under multiple writers. 757 */ 758 newst = random() % (pmp->pm_maxcluster + 1); 759 foundl = 0; 760 761 for (cn = newst; cn <= pmp->pm_maxcluster;) { 762 idx = cn / N_INUSEBITS; 763 map = pmp->pm_inusemap[idx]; 764 map |= (1 << (cn % N_INUSEBITS)) - 1; 765 if (map != (u_int)-1) { 766 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 767 if ((l = chainlength(pmp, cn, count)) >= count) 768 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 769 if (l > foundl) { 770 foundcn = cn; 771 foundl = l; 772 } 773 cn += l + 1; 774 continue; 775 } 776 cn += N_INUSEBITS - cn % N_INUSEBITS; 777 } 778 for (cn = 0; cn < newst;) { 779 idx = cn / N_INUSEBITS; 780 map = pmp->pm_inusemap[idx]; 781 map |= (1 << (cn % N_INUSEBITS)) - 1; 782 if (map != (u_int)-1) { 783 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 784 if ((l = chainlength(pmp, cn, count)) >= count) 785 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 786 if (l > foundl) { 787 foundcn = cn; 788 foundl = l; 789 } 790 cn += l + 1; 791 continue; 792 } 793 cn += N_INUSEBITS - cn % N_INUSEBITS; 794 } 795 796 if (!foundl) 797 return (ENOSPC); 798 799 if (len) 800 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 801 else 802 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 803 } 804 805 806 /* 807 * Free a chain of clusters. 808 * 809 * pmp - address of the msdosfs mount structure for the filesystem 810 * containing the cluster chain to be freed. 811 * startcluster - number of the 1st cluster in the chain of clusters to be 812 * freed. 813 */ 814 int 815 freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 816 { 817 int error; 818 struct buf *bp = NULL; 819 u_long bn, bo, bsize, byteoffset; 820 u_long readcn, lbn = -1; 821 822 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 823 byteoffset = FATOFS(pmp, cluster); 824 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 825 if (lbn != bn) { 826 if (bp) 827 updatefats(pmp, bp, lbn); 828 error = bread(pmp->pm_devvp, bn, bsize, &bp); 829 if (error) { 830 brelse(bp); 831 return (error); 832 } 833 lbn = bn; 834 } 835 usemap_free(pmp, cluster); 836 switch (pmp->pm_fatmask) { 837 case FAT12_MASK: 838 readcn = getushort(&bp->b_data[bo]); 839 if (cluster & 1) { 840 cluster = readcn >> 4; 841 readcn &= 0x000f; 842 readcn |= MSDOSFSFREE << 4; 843 } else { 844 cluster = readcn; 845 readcn &= 0xf000; 846 readcn |= MSDOSFSFREE & 0xfff; 847 } 848 putushort(&bp->b_data[bo], readcn); 849 break; 850 case FAT16_MASK: 851 cluster = getushort(&bp->b_data[bo]); 852 putushort(&bp->b_data[bo], MSDOSFSFREE); 853 break; 854 case FAT32_MASK: 855 cluster = getulong(&bp->b_data[bo]); 856 putulong(&bp->b_data[bo], 857 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 858 break; 859 } 860 cluster &= pmp->pm_fatmask; 861 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 862 cluster |= pmp->pm_fatmask; 863 } 864 if (bp) 865 updatefats(pmp, bp, bn); 866 return (0); 867 } 868 869 /* 870 * Read in fat blocks looking for free clusters. For every free cluster 871 * found turn off its corresponding bit in the pm_inusemap. 872 */ 873 int 874 fillinusemap(struct msdosfsmount *pmp) 875 { 876 struct buf *bp = NULL; 877 u_long cn, readcn; 878 int error; 879 u_long bn, bo, bsize, byteoffset; 880 881 /* 882 * Mark all clusters in use, we mark the free ones in the fat scan 883 * loop further down. 884 */ 885 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 886 pmp->pm_inusemap[cn] = (u_int)-1; 887 888 /* 889 * Figure how many free clusters are in the filesystem by ripping 890 * through the fat counting the number of entries whose content is 891 * zero. These represent free clusters. 892 */ 893 pmp->pm_freeclustercount = 0; 894 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 895 byteoffset = FATOFS(pmp, cn); 896 bo = byteoffset % pmp->pm_fatblocksize; 897 if (!bo || !bp) { 898 /* Read new FAT block */ 899 if (bp) 900 brelse(bp); 901 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 902 error = bread(pmp->pm_devvp, bn, bsize, &bp); 903 if (error) { 904 brelse(bp); 905 return (error); 906 } 907 } 908 if (FAT32(pmp)) 909 readcn = getulong(&bp->b_data[bo]); 910 else 911 readcn = getushort(&bp->b_data[bo]); 912 if (FAT12(pmp) && (cn & 1)) 913 readcn >>= 4; 914 readcn &= pmp->pm_fatmask; 915 916 if (readcn == 0) 917 usemap_free(pmp, cn); 918 } 919 brelse(bp); 920 return (0); 921 } 922 923 /* 924 * Allocate a new cluster and chain it onto the end of the file. 925 * 926 * dep - the file to extend 927 * count - number of clusters to allocate 928 * bpp - where to return the address of the buf header for the first new 929 * file block 930 * ncp - where to put cluster number of the first newly allocated cluster 931 * If this pointer is 0, do not return the cluster number. 932 * flags - see fat.h 933 * 934 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 935 * the de_flag field of the denode and it does not change the de_FileSize 936 * field. This is left for the caller to do. 937 */ 938 int 939 extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, 940 int flags) 941 { 942 int error; 943 u_long frcn; 944 u_long cn, got; 945 struct msdosfsmount *pmp = dep->de_pmp; 946 struct buf *bp; 947 948 /* 949 * Don't try to extend the root directory 950 */ 951 if (dep->de_StartCluster == MSDOSFSROOT 952 && (dep->de_Attributes & ATTR_DIRECTORY)) { 953 printf("extendfile(): attempt to extend root directory\n"); 954 return (ENOSPC); 955 } 956 957 /* 958 * If the "file's last cluster" cache entry is empty, and the file 959 * is not empty, then fill the cache entry by calling pcbmap(). 960 */ 961 fc_fileextends++; 962 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 963 dep->de_StartCluster != 0) { 964 fc_lfcempty++; 965 error = pcbmap(dep, 0xffff, 0, &cn, 0); 966 /* we expect it to return E2BIG */ 967 if (error != E2BIG) 968 return (error); 969 } 970 971 while (count > 0) { 972 /* 973 * Allocate a new cluster chain and cat onto the end of the 974 * file. * If the file is empty we make de_StartCluster point 975 * to the new block. Note that de_StartCluster being 0 is 976 * sufficient to be sure the file is empty since we exclude 977 * attempts to extend the root directory above, and the root 978 * dir is the only file with a startcluster of 0 that has 979 * blocks allocated (sort of). 980 */ 981 if (dep->de_StartCluster == 0) 982 cn = 0; 983 else 984 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 985 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 986 if (error) 987 return (error); 988 989 count -= got; 990 991 /* 992 * Give them the filesystem relative cluster number if they want 993 * it. 994 */ 995 if (ncp) { 996 *ncp = cn; 997 ncp = NULL; 998 } 999 1000 if (dep->de_StartCluster == 0) { 1001 dep->de_StartCluster = cn; 1002 frcn = 0; 1003 } else { 1004 error = fatentry(FAT_SET, pmp, 1005 dep->de_fc[FC_LASTFC].fc_fsrcn, 1006 0, cn); 1007 if (error) { 1008 clusterfree(pmp, cn, NULL); 1009 return (error); 1010 } 1011 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1012 } 1013 1014 /* 1015 * Update the "last cluster of the file" entry in the denode's fat 1016 * cache. 1017 */ 1018 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1019 1020 if (flags & DE_CLEAR) { 1021 while (got-- > 0) { 1022 /* 1023 * Get the buf header for the new block of the file. 1024 */ 1025 if (dep->de_Attributes & ATTR_DIRECTORY) 1026 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1027 pmp->pm_bpcluster, 0, 0); 1028 else { 1029 bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++), 1030 pmp->pm_bpcluster, 0, 0); 1031 /* 1032 * Do the bmap now, as in msdosfs_write 1033 */ 1034 if (pcbmap(dep, 1035 de_bn2cn(pmp, bp->b_lblkno), 1036 &bp->b_blkno, 0, 0)) 1037 bp->b_blkno = -1; 1038 if (bp->b_blkno == -1) 1039 panic("extendfile: pcbmap"); 1040 } 1041 clrbuf(bp); 1042 if (bpp) { 1043 *bpp = bp; 1044 bpp = NULL; 1045 } else 1046 bdwrite(bp); 1047 } 1048 } 1049 } 1050 1051 return (0); 1052 } 1053