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sys/fs/msdosfs/msdosfs_fat.c
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1 /* $NetBSD: msdosfs_fat.c,v 1.2 2003/10/22 03:51:12 briggs 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 #include <sys/cdefs.h> 51 __KERNEL_RCSID(0, "$NetBSD: msdosfs_fat.c,v 1.2 2003/10/22 03:51:12 briggs Exp $"); 52 53 /* 54 * kernel include files. 55 */ 56 #include <sys/param.h> 57 #include <sys/systm.h> 58 #include <sys/buf.h> 59 #include <sys/file.h> 60 #include <sys/namei.h> 61 #include <sys/mount.h> /* to define statfs structure */ 62 #include <sys/vnode.h> /* to define vattr structure */ 63 #include <sys/errno.h> 64 #include <sys/dirent.h> 65 66 /* 67 * msdosfs include files. 68 */ 69 #include <fs/msdosfs/bpb.h> 70 #include <fs/msdosfs/msdosfsmount.h> 71 #include <fs/msdosfs/direntry.h> 72 #include <fs/msdosfs/denode.h> 73 #include <fs/msdosfs/fat.h> 74 75 /* 76 * Fat cache stats. 77 */ 78 int fc_fileextends; /* # of file extends */ 79 int fc_lfcempty; /* # of time last file cluster cache entry 80 * was empty */ 81 int fc_bmapcalls; /* # of times pcbmap was called */ 82 83 #define LMMAX 20 84 int fc_lmdistance[LMMAX]; /* counters for how far off the last 85 * cluster mapped entry was. */ 86 int fc_largedistance; /* off by more than LMMAX */ 87 88 static void fatblock __P((struct msdosfsmount *, u_long, u_long *, u_long *, 89 u_long *)); 90 void updatefats __P((struct msdosfsmount *, struct buf *, u_long)); 91 static __inline void usemap_free __P((struct msdosfsmount *, u_long)); 92 static __inline void usemap_alloc __P((struct msdosfsmount *, u_long)); 93 static int fatchain __P((struct msdosfsmount *, u_long, u_long, u_long)); 94 int chainlength __P((struct msdosfsmount *, u_long, u_long)); 95 int chainalloc __P((struct msdosfsmount *, u_long, u_long, u_long, u_long *, 96 u_long *)); 97 98 static void 99 fatblock(pmp, ofs, bnp, sizep, bop) 100 struct msdosfsmount *pmp; 101 u_long ofs; 102 u_long *bnp; 103 u_long *sizep; 104 u_long *bop; 105 { 106 u_long bn, size; 107 108 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 109 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 110 * pmp->pm_BytesPerSec; 111 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 112 113 if (bnp) 114 *bnp = bn; 115 if (sizep) 116 *sizep = size; 117 if (bop) 118 *bop = ofs % pmp->pm_fatblocksize; 119 } 120 121 /* 122 * Map the logical cluster number of a file into a physical disk sector 123 * that is filesystem relative. 124 * 125 * dep - address of denode representing the file of interest 126 * findcn - file relative cluster whose filesystem relative cluster number 127 * and/or block number are/is to be found 128 * bnp - address of where to place the file system relative block number. 129 * If this pointer is null then don't return this quantity. 130 * cnp - address of where to place the file system relative cluster number. 131 * If this pointer is null then don't return this quantity. 132 * 133 * NOTE: Either bnp or cnp must be non-null. 134 * This function has one side effect. If the requested file relative cluster 135 * is beyond the end of file, then the actual number of clusters in the file 136 * is returned in *cnp. This is useful for determining how long a directory is. 137 * If cnp is null, nothing is returned. 138 */ 139 int 140 pcbmap(dep, findcn, bnp, cnp, sp) 141 struct denode *dep; 142 u_long findcn; /* file relative cluster to get */ 143 daddr_t *bnp; /* returned filesys relative blk number */ 144 u_long *cnp; /* returned cluster number */ 145 int *sp; /* returned block size */ 146 { 147 int error; 148 u_long i; 149 u_long cn; 150 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 151 u_long byteoffset; 152 u_long bn; 153 u_long bo; 154 struct buf *bp = NULL; 155 u_long bp_bn = -1; 156 struct msdosfsmount *pmp = dep->de_pmp; 157 u_long bsize; 158 159 fc_bmapcalls++; 160 161 /* 162 * If they don't give us someplace to return a value then don't 163 * bother doing anything. 164 */ 165 if (bnp == NULL && cnp == NULL && sp == NULL) 166 return (0); 167 168 cn = dep->de_StartCluster; 169 /* 170 * The "file" that makes up the root directory is contiguous, 171 * permanently allocated, of fixed size, and is not made up of 172 * clusters. If the cluster number is beyond the end of the root 173 * directory, then return the number of clusters in the file. 174 */ 175 if (cn == MSDOSFSROOT) { 176 if (dep->de_Attributes & ATTR_DIRECTORY) { 177 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 178 if (cnp) 179 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 180 return (E2BIG); 181 } 182 if (bnp) 183 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 184 if (cnp) 185 *cnp = MSDOSFSROOT; 186 if (sp) 187 *sp = min(pmp->pm_bpcluster, 188 dep->de_FileSize - de_cn2off(pmp, findcn)); 189 return (0); 190 } else { /* just an empty file */ 191 if (cnp) 192 *cnp = 0; 193 return (E2BIG); 194 } 195 } 196 197 /* 198 * All other files do I/O in cluster sized blocks 199 */ 200 if (sp) 201 *sp = pmp->pm_bpcluster; 202 203 /* 204 * Rummage around in the fat cache, maybe we can avoid tromping 205 * thru every fat entry for the file. And, keep track of how far 206 * off the cache was from where we wanted to be. 207 */ 208 i = 0; 209 fc_lookup(dep, findcn, &i, &cn); 210 if ((bn = findcn - i) >= LMMAX) 211 fc_largedistance++; 212 else 213 fc_lmdistance[bn]++; 214 215 /* 216 * Handle all other files or directories the normal way. 217 */ 218 for (; i < findcn; i++) { 219 /* 220 * Stop with all reserved clusters, not just with EOF. 221 */ 222 if (cn >= (CLUST_RSRVD & pmp->pm_fatmask)) 223 goto hiteof; 224 byteoffset = FATOFS(pmp, cn); 225 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 226 if (bn != bp_bn) { 227 if (bp) 228 brelse(bp); 229 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 230 if (error) { 231 brelse(bp); 232 return (error); 233 } 234 bp_bn = bn; 235 } 236 prevcn = cn; 237 if (bo >= bsize) { 238 if (bp) 239 brelse(bp); 240 return (EIO); 241 } 242 if (FAT32(pmp)) 243 cn = getulong(&bp->b_data[bo]); 244 else 245 cn = getushort(&bp->b_data[bo]); 246 if (FAT12(pmp) && (prevcn & 1)) 247 cn >>= 4; 248 cn &= pmp->pm_fatmask; 249 } 250 251 if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) { 252 if (bp) 253 brelse(bp); 254 if (bnp) 255 *bnp = cntobn(pmp, cn); 256 if (cnp) 257 *cnp = cn; 258 fc_setcache(dep, FC_LASTMAP, i, cn); 259 return (0); 260 } 261 262 hiteof:; 263 if (cnp) 264 *cnp = i; 265 if (bp) 266 brelse(bp); 267 /* update last file cluster entry in the fat cache */ 268 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 269 return (E2BIG); 270 } 271 272 /* 273 * Find the closest entry in the fat cache to the cluster we are looking 274 * for. 275 */ 276 void 277 fc_lookup(dep, findcn, frcnp, fsrcnp) 278 struct denode *dep; 279 u_long findcn; 280 u_long *frcnp; 281 u_long *fsrcnp; 282 { 283 int i; 284 u_long cn; 285 struct fatcache *closest = 0; 286 287 for (i = 0; i < FC_SIZE; i++) { 288 cn = dep->de_fc[i].fc_frcn; 289 if (cn != FCE_EMPTY && cn <= findcn) { 290 if (closest == 0 || cn > closest->fc_frcn) 291 closest = &dep->de_fc[i]; 292 } 293 } 294 if (closest) { 295 *frcnp = closest->fc_frcn; 296 *fsrcnp = closest->fc_fsrcn; 297 } 298 } 299 300 /* 301 * Purge the fat cache in denode dep of all entries relating to file 302 * relative cluster frcn and beyond. 303 */ 304 void 305 fc_purge(dep, frcn) 306 struct denode *dep; 307 u_int frcn; 308 { 309 int i; 310 struct fatcache *fcp; 311 312 fcp = dep->de_fc; 313 for (i = 0; i < FC_SIZE; i++, fcp++) { 314 if (fcp->fc_frcn >= frcn) 315 fcp->fc_frcn = FCE_EMPTY; 316 } 317 } 318 319 /* 320 * Update the fat. 321 * If mirroring the fat, update all copies, with the first copy as last. 322 * Else update only the current fat (ignoring the others). 323 * 324 * pmp - msdosfsmount structure for filesystem to update 325 * bp - addr of modified fat block 326 * fatbn - block number relative to begin of filesystem of the modified fat block. 327 */ 328 void 329 updatefats(pmp, bp, fatbn) 330 struct msdosfsmount *pmp; 331 struct buf *bp; 332 u_long fatbn; 333 { 334 int i; 335 struct buf *bpn; 336 337 #ifdef MSDOSFS_DEBUG 338 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", 339 pmp, bp, fatbn); 340 #endif 341 342 /* 343 * If we have an FSInfo block, update it. 344 */ 345 if (pmp->pm_fsinfo) { 346 u_long cn = pmp->pm_nxtfree; 347 348 if (pmp->pm_freeclustercount 349 && (pmp->pm_inusemap[cn / N_INUSEBITS] 350 & (1 << (cn % N_INUSEBITS)))) { 351 /* 352 * The cluster indicated in FSInfo isn't free 353 * any longer. Got get a new free one. 354 */ 355 for (cn = 0; cn < pmp->pm_maxcluster; cn++) 356 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 357 break; 358 pmp->pm_nxtfree = cn 359 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 360 ^ (u_int)-1) - 1; 361 } 362 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, 1024, NOCRED, &bpn) != 0) { 363 /* 364 * Ignore the error, but turn off FSInfo update for the future. 365 */ 366 pmp->pm_fsinfo = 0; 367 brelse(bpn); 368 } else { 369 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 370 371 putulong(fp->fsinfree, pmp->pm_freeclustercount); 372 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 373 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 374 bwrite(bpn); 375 else 376 bdwrite(bpn); 377 } 378 } 379 380 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 381 /* 382 * Now copy the block(s) of the modified fat to the other copies of 383 * the fat and write them out. This is faster than reading in the 384 * other fats and then writing them back out. This could tie up 385 * the fat for quite a while. Preventing others from accessing it. 386 * To prevent us from going after the fat quite so much we use 387 * delayed writes, unless they specfied "synchronous" when the 388 * filesystem was mounted. If synch is asked for then use 389 * bwrite()'s and really slow things down. 390 */ 391 for (i = 1; i < pmp->pm_FATs; i++) { 392 fatbn += pmp->pm_FATsecs; 393 /* getblk() never fails */ 394 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 395 memcpy(bpn->b_data, bp->b_data, bp->b_bcount); 396 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 397 bwrite(bpn); 398 else 399 bdwrite(bpn); 400 } 401 } 402 403 /* 404 * Write out the first (or current) fat last. 405 */ 406 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 407 bwrite(bp); 408 else 409 bdwrite(bp); 410 /* 411 * Maybe update fsinfo sector here? 412 */ 413 } 414 415 /* 416 * Updating entries in 12 bit fats is a pain in the butt. 417 * 418 * The following picture shows where nibbles go when moving from a 12 bit 419 * cluster number into the appropriate bytes in the FAT. 420 * 421 * byte m byte m+1 byte m+2 422 * +----+----+ +----+----+ +----+----+ 423 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 424 * +----+----+ +----+----+ +----+----+ 425 * 426 * +----+----+----+ +----+----+----+ 427 * | 3 0 1 | | 4 5 2 | 428 * +----+----+----+ +----+----+----+ 429 * cluster n cluster n+1 430 * 431 * Where n is even. m = n + (n >> 2) 432 * 433 */ 434 static __inline void 435 usemap_alloc(pmp, cn) 436 struct msdosfsmount *pmp; 437 u_long cn; 438 { 439 440 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 441 pmp->pm_freeclustercount--; 442 } 443 444 static __inline void 445 usemap_free(pmp, cn) 446 struct msdosfsmount *pmp; 447 u_long cn; 448 { 449 450 pmp->pm_freeclustercount++; 451 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 452 } 453 454 int 455 clusterfree(pmp, cluster, oldcnp) 456 struct msdosfsmount *pmp; 457 u_long cluster; 458 u_long *oldcnp; 459 { 460 int error; 461 u_long oldcn; 462 463 usemap_free(pmp, cluster); 464 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 465 if (error) { 466 usemap_alloc(pmp, cluster); 467 return (error); 468 } 469 /* 470 * If the cluster was successfully marked free, then update 471 * the count of free clusters, and turn off the "allocated" 472 * bit in the "in use" cluster bit map. 473 */ 474 if (oldcnp) 475 *oldcnp = oldcn; 476 return (0); 477 } 478 479 /* 480 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 481 * 482 * function - whether to get or set a fat entry 483 * pmp - address of the msdosfsmount structure for the filesystem 484 * whose fat is to be manipulated. 485 * cn - which cluster is of interest 486 * oldcontents - address of a word that is to receive the contents of the 487 * cluster'th entry if this is a get function 488 * newcontents - the new value to be written into the cluster'th element of 489 * the fat if this is a set function. 490 * 491 * This function can also be used to free a cluster by setting the fat entry 492 * for a cluster to 0. 493 * 494 * All copies of the fat are updated if this is a set function. NOTE: If 495 * fatentry() marks a cluster as free it does not update the inusemap in 496 * the msdosfsmount structure. This is left to the caller. 497 */ 498 int 499 fatentry(function, pmp, cn, oldcontents, newcontents) 500 int function; 501 struct msdosfsmount *pmp; 502 u_long cn; 503 u_long *oldcontents; 504 u_long newcontents; 505 { 506 int error; 507 u_long readcn; 508 u_long bn, bo, bsize, byteoffset; 509 struct buf *bp; 510 511 #ifdef MSDOSFS_DEBUG 512 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 513 function, pmp, cn, oldcontents, newcontents); 514 #endif 515 516 #ifdef DIAGNOSTIC 517 /* 518 * Be sure they asked us to do something. 519 */ 520 if ((function & (FAT_SET | FAT_GET)) == 0) { 521 printf("fatentry(): function code doesn't specify get or set\n"); 522 return (EINVAL); 523 } 524 525 /* 526 * If they asked us to return a cluster number but didn't tell us 527 * where to put it, give them an error. 528 */ 529 if ((function & FAT_GET) && oldcontents == NULL) { 530 printf("fatentry(): get function with no place to put result\n"); 531 return (EINVAL); 532 } 533 #endif 534 535 /* 536 * Be sure the requested cluster is in the filesystem. 537 */ 538 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 539 return (EINVAL); 540 541 byteoffset = FATOFS(pmp, cn); 542 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 543 if ((error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp)) != 0) { 544 brelse(bp); 545 return (error); 546 } 547 548 if (function & FAT_GET) { 549 if (FAT32(pmp)) 550 readcn = getulong(&bp->b_data[bo]); 551 else 552 readcn = getushort(&bp->b_data[bo]); 553 if (FAT12(pmp) & (cn & 1)) 554 readcn >>= 4; 555 readcn &= pmp->pm_fatmask; 556 *oldcontents = readcn; 557 } 558 if (function & FAT_SET) { 559 switch (pmp->pm_fatmask) { 560 case FAT12_MASK: 561 readcn = getushort(&bp->b_data[bo]); 562 if (cn & 1) { 563 readcn &= 0x000f; 564 readcn |= newcontents << 4; 565 } else { 566 readcn &= 0xf000; 567 readcn |= newcontents & 0xfff; 568 } 569 putushort(&bp->b_data[bo], readcn); 570 break; 571 case FAT16_MASK: 572 putushort(&bp->b_data[bo], newcontents); 573 break; 574 case FAT32_MASK: 575 /* 576 * According to spec we have to retain the 577 * high order bits of the fat entry. 578 */ 579 readcn = getulong(&bp->b_data[bo]); 580 readcn &= ~FAT32_MASK; 581 readcn |= newcontents & FAT32_MASK; 582 putulong(&bp->b_data[bo], readcn); 583 break; 584 } 585 updatefats(pmp, bp, bn); 586 bp = NULL; 587 pmp->pm_fmod = 1; 588 } 589 if (bp) 590 brelse(bp); 591 return (0); 592 } 593 594 /* 595 * Update a contiguous cluster chain 596 * 597 * pmp - mount point 598 * start - first cluster of chain 599 * count - number of clusters in chain 600 * fillwith - what to write into fat entry of last cluster 601 */ 602 static int 603 fatchain(pmp, start, count, fillwith) 604 struct msdosfsmount *pmp; 605 u_long start; 606 u_long count; 607 u_long fillwith; 608 { 609 int error; 610 u_long bn, bo, bsize, byteoffset, readcn, newc; 611 struct buf *bp; 612 613 #ifdef MSDOSFS_DEBUG 614 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 615 pmp, start, count, fillwith); 616 #endif 617 /* 618 * Be sure the clusters are in the filesystem. 619 */ 620 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 621 return (EINVAL); 622 623 while (count > 0) { 624 byteoffset = FATOFS(pmp, start); 625 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 626 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 627 if (error) { 628 brelse(bp); 629 return (error); 630 } 631 while (count > 0) { 632 start++; 633 newc = --count > 0 ? start : fillwith; 634 switch (pmp->pm_fatmask) { 635 case FAT12_MASK: 636 readcn = getushort(&bp->b_data[bo]); 637 if (start & 1) { 638 readcn &= 0xf000; 639 readcn |= newc & 0xfff; 640 } else { 641 readcn &= 0x000f; 642 readcn |= newc << 4; 643 } 644 putushort(&bp->b_data[bo], readcn); 645 bo++; 646 if (!(start & 1)) 647 bo++; 648 break; 649 case FAT16_MASK: 650 putushort(&bp->b_data[bo], newc); 651 bo += 2; 652 break; 653 case FAT32_MASK: 654 readcn = getulong(&bp->b_data[bo]); 655 readcn &= ~pmp->pm_fatmask; 656 readcn |= newc & pmp->pm_fatmask; 657 putulong(&bp->b_data[bo], readcn); 658 bo += 4; 659 break; 660 } 661 if (bo >= bsize) 662 break; 663 } 664 updatefats(pmp, bp, bn); 665 } 666 pmp->pm_fmod = 1; 667 return (0); 668 } 669 670 /* 671 * Check the length of a free cluster chain starting at start. 672 * 673 * pmp - mount point 674 * start - start of chain 675 * count - maximum interesting length 676 */ 677 int 678 chainlength(pmp, start, count) 679 struct msdosfsmount *pmp; 680 u_long start; 681 u_long count; 682 { 683 u_long idx, max_idx; 684 u_int map; 685 u_long len; 686 687 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 688 idx = start / N_INUSEBITS; 689 start %= N_INUSEBITS; 690 map = pmp->pm_inusemap[idx]; 691 map &= ~((1 << start) - 1); 692 if (map) { 693 len = ffs(map) - 1 - start; 694 return (len > count ? count : len); 695 } 696 len = N_INUSEBITS - start; 697 if (len >= count) 698 return (count); 699 while (++idx <= max_idx) { 700 if (len >= count) 701 break; 702 if ((map = pmp->pm_inusemap[idx]) != 0) { 703 len += ffs(map) - 1; 704 break; 705 } 706 len += N_INUSEBITS; 707 } 708 return (len > count ? count : len); 709 } 710 711 /* 712 * Allocate contigous free clusters. 713 * 714 * pmp - mount point. 715 * start - start of cluster chain. 716 * count - number of clusters to allocate. 717 * fillwith - put this value into the fat entry for the 718 * last allocated cluster. 719 * retcluster - put the first allocated cluster's number here. 720 * got - how many clusters were actually allocated. 721 */ 722 int 723 chainalloc(pmp, start, count, fillwith, retcluster, got) 724 struct msdosfsmount *pmp; 725 u_long start; 726 u_long count; 727 u_long fillwith; 728 u_long *retcluster; 729 u_long *got; 730 { 731 int error; 732 u_long cl, n; 733 734 for (cl = start, n = count; n-- > 0;) 735 usemap_alloc(pmp, cl++); 736 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 737 return (error); 738 #ifdef MSDOSFS_DEBUG 739 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 740 start, count); 741 #endif 742 if (retcluster) 743 *retcluster = start; 744 if (got) 745 *got = count; 746 return (0); 747 } 748 749 /* 750 * Allocate contiguous free clusters. 751 * 752 * pmp - mount point. 753 * start - preferred start of cluster chain. 754 * count - number of clusters requested. 755 * fillwith - put this value into the fat entry for the 756 * last allocated cluster. 757 * retcluster - put the first allocated cluster's number here. 758 * got - how many clusters were actually allocated. 759 */ 760 int 761 clusteralloc(pmp, start, count, retcluster, got) 762 struct msdosfsmount *pmp; 763 u_long start; 764 u_long count; 765 u_long *retcluster; 766 u_long *got; 767 { 768 u_long idx; 769 u_long len, newst, foundl, cn, l; 770 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 771 u_long fillwith = CLUST_EOFE; 772 u_int map; 773 774 #ifdef MSDOSFS_DEBUG 775 printf("clusteralloc(): find %lu clusters\n",count); 776 #endif 777 if (start) { 778 if ((len = chainlength(pmp, start, count)) >= count) 779 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 780 } else { 781 /* 782 * This is a new file, initialize start 783 */ 784 struct timeval tv; 785 786 microtime(&tv); 787 start = (tv.tv_usec >> 10) | tv.tv_usec; 788 len = 0; 789 } 790 791 /* 792 * Start at a (pseudo) random place to maximize cluster runs 793 * under multiple writers. 794 */ 795 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 796 foundl = 0; 797 798 for (cn = newst; cn <= pmp->pm_maxcluster;) { 799 idx = cn / N_INUSEBITS; 800 map = pmp->pm_inusemap[idx]; 801 map |= (1 << (cn % N_INUSEBITS)) - 1; 802 if (map != (u_int)-1) { 803 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 804 if ((l = chainlength(pmp, cn, count)) >= count) 805 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 806 if (l > foundl) { 807 foundcn = cn; 808 foundl = l; 809 } 810 cn += l + 1; 811 continue; 812 } 813 cn += N_INUSEBITS - cn % N_INUSEBITS; 814 } 815 for (cn = 0; cn < newst;) { 816 idx = cn / N_INUSEBITS; 817 map = pmp->pm_inusemap[idx]; 818 map |= (1 << (cn % N_INUSEBITS)) - 1; 819 if (map != (u_int)-1) { 820 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 821 if ((l = chainlength(pmp, cn, count)) >= count) 822 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 823 if (l > foundl) { 824 foundcn = cn; 825 foundl = l; 826 } 827 cn += l + 1; 828 continue; 829 } 830 cn += N_INUSEBITS - cn % N_INUSEBITS; 831 } 832 833 if (!foundl) 834 return (ENOSPC); 835 836 if (len) 837 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 838 else 839 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 840 } 841 842 843 /* 844 * Free a chain of clusters. 845 * 846 * pmp - address of the msdosfs mount structure for the filesystem 847 * containing the cluster chain to be freed. 848 * startcluster - number of the 1st cluster in the chain of clusters to be 849 * freed. 850 */ 851 int 852 freeclusterchain(pmp, cluster) 853 struct msdosfsmount *pmp; 854 u_long cluster; 855 { 856 int error; 857 struct buf *bp = NULL; 858 u_long bn, bo, bsize, byteoffset; 859 u_long readcn, lbn = -1; 860 861 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 862 byteoffset = FATOFS(pmp, cluster); 863 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 864 if (lbn != bn) { 865 if (bp) 866 updatefats(pmp, bp, lbn); 867 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 868 if (error) { 869 brelse(bp); 870 return (error); 871 } 872 lbn = bn; 873 } 874 usemap_free(pmp, cluster); 875 switch (pmp->pm_fatmask) { 876 case FAT12_MASK: 877 readcn = getushort(&bp->b_data[bo]); 878 if (cluster & 1) { 879 cluster = readcn >> 4; 880 readcn &= 0x000f; 881 readcn |= MSDOSFSFREE << 4; 882 } else { 883 cluster = readcn; 884 readcn &= 0xf000; 885 readcn |= MSDOSFSFREE & 0xfff; 886 } 887 putushort(&bp->b_data[bo], readcn); 888 break; 889 case FAT16_MASK: 890 cluster = getushort(&bp->b_data[bo]); 891 putushort(&bp->b_data[bo], MSDOSFSFREE); 892 break; 893 case FAT32_MASK: 894 cluster = getulong(&bp->b_data[bo]); 895 putulong(&bp->b_data[bo], 896 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 897 break; 898 } 899 cluster &= pmp->pm_fatmask; 900 } 901 if (bp) 902 updatefats(pmp, bp, bn); 903 return (0); 904 } 905 906 /* 907 * Read in fat blocks looking for free clusters. For every free cluster 908 * found turn off its corresponding bit in the pm_inusemap. 909 */ 910 int 911 fillinusemap(pmp) 912 struct msdosfsmount *pmp; 913 { 914 struct buf *bp = NULL; 915 u_long cn, readcn; 916 int error; 917 u_long bn, bo, bsize, byteoffset; 918 919 /* 920 * Mark all clusters in use, we mark the free ones in the fat scan 921 * loop further down. 922 */ 923 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 924 pmp->pm_inusemap[cn] = (u_int)-1; 925 926 /* 927 * Figure how many free clusters are in the filesystem by ripping 928 * through the fat counting the number of entries whose content is 929 * zero. These represent free clusters. 930 */ 931 pmp->pm_freeclustercount = 0; 932 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 933 byteoffset = FATOFS(pmp, cn); 934 bo = byteoffset % pmp->pm_fatblocksize; 935 if (!bo || !bp) { 936 /* Read new FAT block */ 937 if (bp) 938 brelse(bp); 939 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 940 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 941 if (error) { 942 brelse(bp); 943 return (error); 944 } 945 } 946 if (FAT32(pmp)) 947 readcn = getulong(&bp->b_data[bo]); 948 else 949 readcn = getushort(&bp->b_data[bo]); 950 if (FAT12(pmp) && (cn & 1)) 951 readcn >>= 4; 952 readcn &= pmp->pm_fatmask; 953 954 if (readcn == 0) 955 usemap_free(pmp, cn); 956 } 957 brelse(bp); 958 return (0); 959 } 960 961 /* 962 * Allocate a new cluster and chain it onto the end of the file. 963 * 964 * dep - the file to extend 965 * count - number of clusters to allocate 966 * bpp - where to return the address of the buf header for the first new 967 * file block 968 * ncp - where to put cluster number of the first newly allocated cluster 969 * If this pointer is 0, do not return the cluster number. 970 * flags - see fat.h 971 * 972 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 973 * the de_flag field of the denode and it does not change the de_FileSize 974 * field. This is left for the caller to do. 975 */ 976 977 int 978 extendfile(dep, count, bpp, ncp, flags) 979 struct denode *dep; 980 u_long count; 981 struct buf **bpp; 982 u_long *ncp; 983 int flags; 984 { 985 int error; 986 u_long frcn = 0, cn, got; 987 struct msdosfsmount *pmp = dep->de_pmp; 988 struct buf *bp; 989 990 /* 991 * Don't try to extend the root directory 992 */ 993 if (dep->de_StartCluster == MSDOSFSROOT 994 && (dep->de_Attributes & ATTR_DIRECTORY)) { 995 printf("extendfile(): attempt to extend root directory\n"); 996 return (ENOSPC); 997 } 998 999 /* 1000 * If the "file's last cluster" cache entry is empty, and the file 1001 * is not empty, then fill the cache entry by calling pcbmap(). 1002 */ 1003 fc_fileextends++; 1004 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1005 dep->de_StartCluster != 0) { 1006 fc_lfcempty++; 1007 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 1008 /* we expect it to return E2BIG */ 1009 if (error != E2BIG) 1010 return (error); 1011 } 1012 1013 while (count > 0) { 1014 1015 /* 1016 * Allocate a new cluster chain and cat onto the end of the 1017 * file. If the file is empty we make de_StartCluster point 1018 * to the new block. Note that de_StartCluster being 0 is 1019 * sufficient to be sure the file is empty since we exclude 1020 * attempts to extend the root directory above, and the root 1021 * dir is the only file with a startcluster of 0 that has 1022 * blocks allocated (sort of). 1023 */ 1024 1025 if (dep->de_StartCluster == 0) 1026 cn = 0; 1027 else 1028 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1029 error = clusteralloc(pmp, cn, count, &cn, &got); 1030 if (error) 1031 return (error); 1032 1033 count -= got; 1034 1035 /* 1036 * Give them the filesystem relative cluster number if they want 1037 * it. 1038 */ 1039 if (ncp) { 1040 *ncp = cn; 1041 ncp = NULL; 1042 } 1043 1044 if (dep->de_StartCluster == 0) { 1045 dep->de_StartCluster = cn; 1046 frcn = 0; 1047 } else { 1048 error = fatentry(FAT_SET, pmp, 1049 dep->de_fc[FC_LASTFC].fc_fsrcn, 1050 0, cn); 1051 if (error) { 1052 clusterfree(pmp, cn, NULL); 1053 return (error); 1054 } 1055 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1056 } 1057 1058 /* 1059 * Update the "last cluster of the file" entry in the 1060 * denode's fat cache. 1061 */ 1062 1063 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1064 if ((flags & DE_CLEAR) && 1065 (dep->de_Attributes & ATTR_DIRECTORY)) { 1066 while (got-- > 0) { 1067 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1068 pmp->pm_bpcluster, 0, 0); 1069 clrbuf(bp); 1070 if (bpp) { 1071 *bpp = bp; 1072 bpp = NULL; 1073 } else { 1074 bdwrite(bp); 1075 } 1076 } 1077 } 1078 } 1079 1080 return (0); 1081 }
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