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sys/msdosfs/msdosfs_fat.c
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1 /* $FreeBSD: src/sys/msdosfs/msdosfs_fat.c,v 1.10.4.3 1999/09/05 08:17:19 peter Exp $ */ 2 /* $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $ */ 3 4 /*- 5 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. 6 * Copyright (C) 1994, 1995, 1997 TooLs GmbH. 7 * All rights reserved. 8 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by TooLs GmbH. 21 * 4. The name of TooLs GmbH may not be used to endorse or promote products 22 * derived from this software without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR 25 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 26 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 27 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 29 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 30 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 31 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 32 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 33 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34 */ 35 /* 36 * Written by Paul Popelka (paulp@uts.amdahl.com) 37 * 38 * You can do anything you want with this software, just don't say you wrote 39 * it, and don't remove this notice. 40 * 41 * This software is provided "as is". 42 * 43 * The author supplies this software to be publicly redistributed on the 44 * understanding that the author is not responsible for the correct 45 * functioning of this software in any circumstances and is not liable for 46 * any damages caused by this software. 47 * 48 * October 1992 49 */ 50 51 /* 52 * kernel include files. 53 */ 54 #include <sys/param.h> 55 #include <sys/systm.h> 56 #include <sys/buf.h> 57 #include <sys/mount.h> /* to define statfs structure */ 58 #include <sys/vnode.h> /* to define vattr structure */ 59 60 /* 61 * msdosfs include files. 62 */ 63 #include <msdosfs/bpb.h> 64 #include <msdosfs/msdosfsmount.h> 65 #include <msdosfs/direntry.h> 66 #include <msdosfs/denode.h> 67 #include <msdosfs/fat.h> 68 69 /* 70 * Fat cache stats. 71 */ 72 static int fc_fileextends; /* # of file extends */ 73 static int fc_lfcempty; /* # of time last file cluster cache entry 74 * was empty */ 75 static int fc_bmapcalls; /* # of times pcbmap was called */ 76 77 #define LMMAX 20 78 static int fc_lmdistance[LMMAX];/* counters for how far off the last 79 * cluster mapped entry was. */ 80 static int fc_largedistance; /* off by more than LMMAX */ 81 82 static int chainalloc __P((struct msdosfsmount *pmp, u_long start, 83 u_long count, u_long fillwith, 84 u_long *retcluster, u_long *got)); 85 static int chainlength __P((struct msdosfsmount *pmp, u_long start, 86 u_long count)); 87 static void fatblock __P((struct msdosfsmount *pmp, u_long ofs, 88 u_long *bnp, u_long *sizep, u_long *bop)); 89 static int fatchain __P((struct msdosfsmount *pmp, u_long start, 90 u_long count, u_long fillwith)); 91 static void fc_lookup __P((struct denode *dep, u_long findcn, 92 u_long *frcnp, u_long *fsrcnp)); 93 static void updatefats __P((struct msdosfsmount *pmp, struct buf *bp, 94 u_long fatbn)); 95 static __inline void 96 usemap_alloc __P((struct msdosfsmount *pmp, u_long cn)); 97 static __inline void 98 usemap_free __P((struct msdosfsmount *pmp, u_long cn)); 99 100 static void 101 fatblock(pmp, ofs, bnp, sizep, bop) 102 struct msdosfsmount *pmp; 103 u_long ofs; 104 u_long *bnp; 105 u_long *sizep; 106 u_long *bop; 107 { 108 u_long bn, size; 109 110 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 111 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 112 * pmp->pm_BytesPerSec; 113 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 114 115 if (bnp) 116 *bnp = bn; 117 if (sizep) 118 *sizep = size; 119 if (bop) 120 *bop = ofs % pmp->pm_fatblocksize; 121 } 122 123 /* 124 * Map the logical cluster number of a file into a physical disk sector 125 * that is filesystem relative. 126 * 127 * dep - address of denode representing the file of interest 128 * findcn - file relative cluster whose filesystem relative cluster number 129 * and/or block number are/is to be found 130 * bnp - address of where to place the file system relative block number. 131 * If this pointer is null then don't return this quantity. 132 * cnp - address of where to place the file system relative cluster number. 133 * If this pointer is null then don't return this quantity. 134 * 135 * NOTE: Either bnp or cnp must be non-null. 136 * This function has one side effect. If the requested file relative cluster 137 * is beyond the end of file, then the actual number of clusters in the file 138 * is returned in *cnp. This is useful for determining how long a directory is. 139 * If cnp is null, nothing is returned. 140 */ 141 int 142 pcbmap(dep, findcn, bnp, cnp, sp) 143 struct denode *dep; 144 u_long findcn; /* file relative cluster to get */ 145 daddr_t *bnp; /* returned filesys relative blk number */ 146 u_long *cnp; /* returned cluster number */ 147 int *sp; /* returned block size */ 148 { 149 int error; 150 u_long i; 151 u_long cn; 152 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 153 u_long byteoffset; 154 u_long bn; 155 u_long bo; 156 struct buf *bp = NULL; 157 u_long bp_bn = -1; 158 struct msdosfsmount *pmp = dep->de_pmp; 159 u_long bsize; 160 161 fc_bmapcalls++; 162 163 /* 164 * If they don't give us someplace to return a value then don't 165 * bother doing anything. 166 */ 167 if (bnp == NULL && cnp == NULL && sp == NULL) 168 return (0); 169 170 cn = dep->de_StartCluster; 171 /* 172 * The "file" that makes up the root directory is contiguous, 173 * permanently allocated, of fixed size, and is not made up of 174 * clusters. If the cluster number is beyond the end of the root 175 * directory, then return the number of clusters in the file. 176 */ 177 if (cn == MSDOSFSROOT) { 178 if (dep->de_Attributes & ATTR_DIRECTORY) { 179 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 180 if (cnp) 181 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 182 return (E2BIG); 183 } 184 if (bnp) 185 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 186 if (cnp) 187 *cnp = MSDOSFSROOT; 188 if (sp) 189 *sp = min(pmp->pm_bpcluster, 190 dep->de_FileSize - de_cn2off(pmp, findcn)); 191 return (0); 192 } else { /* just an empty file */ 193 if (cnp) 194 *cnp = 0; 195 return (E2BIG); 196 } 197 } 198 199 /* 200 * All other files do I/O in cluster sized blocks 201 */ 202 if (sp) 203 *sp = pmp->pm_bpcluster; 204 205 /* 206 * Rummage around in the fat cache, maybe we can avoid tromping 207 * thru every fat entry for the file. And, keep track of how far 208 * off the cache was from where we wanted to be. 209 */ 210 i = 0; 211 fc_lookup(dep, findcn, &i, &cn); 212 if ((bn = findcn - i) >= LMMAX) 213 fc_largedistance++; 214 else 215 fc_lmdistance[bn]++; 216 217 /* 218 * Handle all other files or directories the normal way. 219 */ 220 for (; i < findcn; i++) { 221 /* 222 * Stop with all reserved clusters, not just with EOF. 223 */ 224 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 225 goto hiteof; 226 byteoffset = FATOFS(pmp, cn); 227 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 228 if (bn != bp_bn) { 229 if (bp) 230 brelse(bp); 231 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 232 if (error) { 233 brelse(bp); 234 return (error); 235 } 236 bp_bn = bn; 237 } 238 prevcn = cn; 239 if (FAT32(pmp)) 240 cn = getulong(&bp->b_data[bo]); 241 else 242 cn = getushort(&bp->b_data[bo]); 243 if (FAT12(pmp) && (prevcn & 1)) 244 cn >>= 4; 245 cn &= pmp->pm_fatmask; 246 247 /* 248 * Force the special cluster numbers 249 * to be the same for all cluster sizes 250 * to let the rest of msdosfs handle 251 * all cases the same. 252 */ 253 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 254 cn |= ~pmp->pm_fatmask; 255 } 256 257 if (!MSDOSFSEOF(pmp, cn)) { 258 if (bp) 259 brelse(bp); 260 if (bnp) 261 *bnp = cntobn(pmp, cn); 262 if (cnp) 263 *cnp = cn; 264 fc_setcache(dep, FC_LASTMAP, i, cn); 265 return (0); 266 } 267 268 hiteof:; 269 if (cnp) 270 *cnp = i; 271 if (bp) 272 brelse(bp); 273 /* update last file cluster entry in the fat cache */ 274 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 275 return (E2BIG); 276 } 277 278 /* 279 * Find the closest entry in the fat cache to the cluster we are looking 280 * for. 281 */ 282 static void 283 fc_lookup(dep, findcn, frcnp, fsrcnp) 284 struct denode *dep; 285 u_long findcn; 286 u_long *frcnp; 287 u_long *fsrcnp; 288 { 289 int i; 290 u_long cn; 291 struct fatcache *closest = 0; 292 293 for (i = 0; i < FC_SIZE; i++) { 294 cn = dep->de_fc[i].fc_frcn; 295 if (cn != FCE_EMPTY && cn <= findcn) { 296 if (closest == 0 || cn > closest->fc_frcn) 297 closest = &dep->de_fc[i]; 298 } 299 } 300 if (closest) { 301 *frcnp = closest->fc_frcn; 302 *fsrcnp = closest->fc_fsrcn; 303 } 304 } 305 306 /* 307 * Purge the fat cache in denode dep of all entries relating to file 308 * relative cluster frcn and beyond. 309 */ 310 void 311 fc_purge(dep, frcn) 312 struct denode *dep; 313 u_int frcn; 314 { 315 int i; 316 struct fatcache *fcp; 317 318 fcp = dep->de_fc; 319 for (i = 0; i < FC_SIZE; i++, fcp++) { 320 if (fcp->fc_frcn >= frcn) 321 fcp->fc_frcn = FCE_EMPTY; 322 } 323 } 324 325 /* 326 * Update the fat. 327 * If mirroring the fat, update all copies, with the first copy as last. 328 * Else update only the current fat (ignoring the others). 329 * 330 * pmp - msdosfsmount structure for filesystem to update 331 * bp - addr of modified fat block 332 * fatbn - block number relative to begin of filesystem of the modified fat block. 333 */ 334 static void 335 updatefats(pmp, bp, fatbn) 336 struct msdosfsmount *pmp; 337 struct buf *bp; 338 u_long fatbn; 339 { 340 int i; 341 struct buf *bpn; 342 343 #ifdef MSDOSFS_DEBUG 344 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn); 345 #endif 346 347 /* 348 * If we have an FSInfo block, update it. 349 */ 350 if (pmp->pm_fsinfo) { 351 u_long cn = pmp->pm_nxtfree; 352 353 if (pmp->pm_freeclustercount 354 && (pmp->pm_inusemap[cn / N_INUSEBITS] 355 & (1 << (cn % N_INUSEBITS)))) { 356 /* 357 * The cluster indicated in FSInfo isn't free 358 * any longer. Got get a new free one. 359 */ 360 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS) 361 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 362 break; 363 pmp->pm_nxtfree = cn 364 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 365 ^ (u_int)-1) - 1; 366 } 367 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, 1024, NOCRED, &bpn) != 0) { 368 /* 369 * Ignore the error, but turn off FSInfo update for the future. 370 */ 371 pmp->pm_fsinfo = 0; 372 brelse(bpn); 373 } else { 374 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 375 376 putulong(fp->fsinfree, pmp->pm_freeclustercount); 377 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 378 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 379 bwrite(bpn); 380 else 381 bdwrite(bpn); 382 } 383 } 384 385 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 386 /* 387 * Now copy the block(s) of the modified fat to the other copies of 388 * the fat and write them out. This is faster than reading in the 389 * other fats and then writing them back out. This could tie up 390 * the fat for quite a while. Preventing others from accessing it. 391 * To prevent us from going after the fat quite so much we use 392 * delayed writes, unless they specfied "synchronous" when the 393 * filesystem was mounted. If synch is asked for then use 394 * bwrite()'s and really slow things down. 395 */ 396 for (i = 1; i < pmp->pm_FATs; i++) { 397 fatbn += pmp->pm_FATsecs; 398 /* getblk() never fails */ 399 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 400 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 401 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 402 bwrite(bpn); 403 else 404 bdwrite(bpn); 405 } 406 } 407 408 /* 409 * Write out the first (or current) fat last. 410 */ 411 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 412 bwrite(bp); 413 else 414 bdwrite(bp); 415 /* 416 * Maybe update fsinfo sector here? 417 */ 418 } 419 420 /* 421 * Updating entries in 12 bit fats is a pain in the butt. 422 * 423 * The following picture shows where nibbles go when moving from a 12 bit 424 * cluster number into the appropriate bytes in the FAT. 425 * 426 * byte m byte m+1 byte m+2 427 * +----+----+ +----+----+ +----+----+ 428 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 429 * +----+----+ +----+----+ +----+----+ 430 * 431 * +----+----+----+ +----+----+----+ 432 * | 3 0 1 | | 4 5 2 | 433 * +----+----+----+ +----+----+----+ 434 * cluster n cluster n+1 435 * 436 * Where n is even. m = n + (n >> 2) 437 * 438 */ 439 static __inline void 440 usemap_alloc(pmp, cn) 441 struct msdosfsmount *pmp; 442 u_long cn; 443 { 444 445 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 446 pmp->pm_freeclustercount--; 447 } 448 449 static __inline void 450 usemap_free(pmp, cn) 451 struct msdosfsmount *pmp; 452 u_long cn; 453 { 454 455 pmp->pm_freeclustercount++; 456 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 457 } 458 459 int 460 clusterfree(pmp, cluster, oldcnp) 461 struct msdosfsmount *pmp; 462 u_long cluster; 463 u_long *oldcnp; 464 { 465 int error; 466 u_long oldcn; 467 468 usemap_free(pmp, cluster); 469 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 470 if (error) { 471 usemap_alloc(pmp, cluster); 472 return (error); 473 } 474 /* 475 * If the cluster was successfully marked free, then update 476 * the count of free clusters, and turn off the "allocated" 477 * bit in the "in use" cluster bit map. 478 */ 479 if (oldcnp) 480 *oldcnp = oldcn; 481 return (0); 482 } 483 484 /* 485 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 486 * 487 * function - whether to get or set a fat entry 488 * pmp - address of the msdosfsmount structure for the filesystem 489 * whose fat is to be manipulated. 490 * cn - which cluster is of interest 491 * oldcontents - address of a word that is to receive the contents of the 492 * cluster'th entry if this is a get function 493 * newcontents - the new value to be written into the cluster'th element of 494 * the fat if this is a set function. 495 * 496 * This function can also be used to free a cluster by setting the fat entry 497 * for a cluster to 0. 498 * 499 * All copies of the fat are updated if this is a set function. NOTE: If 500 * fatentry() marks a cluster as free it does not update the inusemap in 501 * the msdosfsmount structure. This is left to the caller. 502 */ 503 int 504 fatentry(function, pmp, cn, oldcontents, newcontents) 505 int function; 506 struct msdosfsmount *pmp; 507 u_long cn; 508 u_long *oldcontents; 509 u_long newcontents; 510 { 511 int error; 512 u_long readcn; 513 u_long bn, bo, bsize, byteoffset; 514 struct buf *bp; 515 516 #ifdef MSDOSFS_DEBUG 517 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 518 function, pmp, cn, oldcontents, newcontents); 519 #endif 520 521 #ifdef DIAGNOSTIC 522 /* 523 * Be sure they asked us to do something. 524 */ 525 if ((function & (FAT_SET | FAT_GET)) == 0) { 526 printf("fatentry(): function code doesn't specify get or set\n"); 527 return (EINVAL); 528 } 529 530 /* 531 * If they asked us to return a cluster number but didn't tell us 532 * where to put it, give them an error. 533 */ 534 if ((function & FAT_GET) && oldcontents == NULL) { 535 printf("fatentry(): get function with no place to put result\n"); 536 return (EINVAL); 537 } 538 #endif 539 540 /* 541 * Be sure the requested cluster is in the filesystem. 542 */ 543 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 544 return (EINVAL); 545 546 byteoffset = FATOFS(pmp, cn); 547 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 548 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 549 if (error) { 550 brelse(bp); 551 return (error); 552 } 553 554 if (function & FAT_GET) { 555 if (FAT32(pmp)) 556 readcn = getulong(&bp->b_data[bo]); 557 else 558 readcn = getushort(&bp->b_data[bo]); 559 if (FAT12(pmp) & (cn & 1)) 560 readcn >>= 4; 561 readcn &= pmp->pm_fatmask; 562 /* map reserved fat entries to same values for all fats */ 563 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 564 readcn |= ~pmp->pm_fatmask; 565 *oldcontents = readcn; 566 } 567 if (function & FAT_SET) { 568 switch (pmp->pm_fatmask) { 569 case FAT12_MASK: 570 readcn = getushort(&bp->b_data[bo]); 571 if (cn & 1) { 572 readcn &= 0x000f; 573 readcn |= newcontents << 4; 574 } else { 575 readcn &= 0xf000; 576 readcn |= newcontents & 0xfff; 577 } 578 putushort(&bp->b_data[bo], readcn); 579 break; 580 case FAT16_MASK: 581 putushort(&bp->b_data[bo], newcontents); 582 break; 583 case FAT32_MASK: 584 /* 585 * According to spec we have to retain the 586 * high order bits of the fat entry. 587 */ 588 readcn = getulong(&bp->b_data[bo]); 589 readcn &= ~FAT32_MASK; 590 readcn |= newcontents & FAT32_MASK; 591 putulong(&bp->b_data[bo], readcn); 592 break; 593 } 594 updatefats(pmp, bp, bn); 595 bp = NULL; 596 pmp->pm_fmod = 1; 597 } 598 if (bp) 599 brelse(bp); 600 return (0); 601 } 602 603 /* 604 * Update a contiguous cluster chain 605 * 606 * pmp - mount point 607 * start - first cluster of chain 608 * count - number of clusters in chain 609 * fillwith - what to write into fat entry of last cluster 610 */ 611 static int 612 fatchain(pmp, start, count, fillwith) 613 struct msdosfsmount *pmp; 614 u_long start; 615 u_long count; 616 u_long fillwith; 617 { 618 int error; 619 u_long bn, bo, bsize, byteoffset, readcn, newc; 620 struct buf *bp; 621 622 #ifdef MSDOSFS_DEBUG 623 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 624 pmp, start, count, fillwith); 625 #endif 626 /* 627 * Be sure the clusters are in the filesystem. 628 */ 629 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 630 return (EINVAL); 631 632 while (count > 0) { 633 byteoffset = FATOFS(pmp, start); 634 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 635 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 636 if (error) { 637 brelse(bp); 638 return (error); 639 } 640 while (count > 0) { 641 start++; 642 newc = --count > 0 ? start : fillwith; 643 switch (pmp->pm_fatmask) { 644 case FAT12_MASK: 645 readcn = getushort(&bp->b_data[bo]); 646 if (start & 1) { 647 readcn &= 0xf000; 648 readcn |= newc & 0xfff; 649 } else { 650 readcn &= 0x000f; 651 readcn |= newc << 4; 652 } 653 putushort(&bp->b_data[bo], readcn); 654 bo++; 655 if (!(start & 1)) 656 bo++; 657 break; 658 case FAT16_MASK: 659 putushort(&bp->b_data[bo], newc); 660 bo += 2; 661 break; 662 case FAT32_MASK: 663 readcn = getulong(&bp->b_data[bo]); 664 readcn &= ~pmp->pm_fatmask; 665 readcn |= newc & pmp->pm_fatmask; 666 putulong(&bp->b_data[bo], readcn); 667 bo += 4; 668 break; 669 } 670 if (bo >= bsize) 671 break; 672 } 673 updatefats(pmp, bp, bn); 674 } 675 pmp->pm_fmod = 1; 676 return (0); 677 } 678 679 /* 680 * Check the length of a free cluster chain starting at start. 681 * 682 * pmp - mount point 683 * start - start of chain 684 * count - maximum interesting length 685 */ 686 static int 687 chainlength(pmp, start, count) 688 struct msdosfsmount *pmp; 689 u_long start; 690 u_long count; 691 { 692 u_long idx, max_idx; 693 u_int map; 694 u_long len; 695 696 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 697 idx = start / N_INUSEBITS; 698 start %= N_INUSEBITS; 699 map = pmp->pm_inusemap[idx]; 700 map &= ~((1 << start) - 1); 701 if (map) { 702 len = ffs(map) - 1 - start; 703 return (len > count ? count : len); 704 } 705 len = N_INUSEBITS - start; 706 if (len >= count) 707 return (count); 708 while (++idx <= max_idx) { 709 if (len >= count) 710 break; 711 map = pmp->pm_inusemap[idx]; 712 if (map) { 713 len += ffs(map) - 1; 714 break; 715 } 716 len += N_INUSEBITS; 717 } 718 return (len > count ? count : len); 719 } 720 721 /* 722 * Allocate contigous free clusters. 723 * 724 * pmp - mount point. 725 * start - start of cluster chain. 726 * count - number of clusters to allocate. 727 * fillwith - put this value into the fat entry for the 728 * last allocated cluster. 729 * retcluster - put the first allocated cluster's number here. 730 * got - how many clusters were actually allocated. 731 */ 732 static int 733 chainalloc(pmp, start, count, fillwith, retcluster, got) 734 struct msdosfsmount *pmp; 735 u_long start; 736 u_long count; 737 u_long fillwith; 738 u_long *retcluster; 739 u_long *got; 740 { 741 int error; 742 u_long cl, n; 743 744 for (cl = start, n = count; n-- > 0;) 745 usemap_alloc(pmp, cl++); 746 747 error = fatchain(pmp, start, count, fillwith); 748 if (error != 0) 749 return (error); 750 #ifdef MSDOSFS_DEBUG 751 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 752 start, count); 753 #endif 754 if (retcluster) 755 *retcluster = start; 756 if (got) 757 *got = count; 758 return (0); 759 } 760 761 /* 762 * Allocate contiguous free clusters. 763 * 764 * pmp - mount point. 765 * start - preferred start of cluster chain. 766 * count - number of clusters requested. 767 * fillwith - put this value into the fat entry for the 768 * last allocated cluster. 769 * retcluster - put the first allocated cluster's number here. 770 * got - how many clusters were actually allocated. 771 */ 772 int 773 clusteralloc(pmp, start, count, fillwith, retcluster, got) 774 struct msdosfsmount *pmp; 775 u_long start; 776 u_long count; 777 u_long fillwith; 778 u_long *retcluster; 779 u_long *got; 780 { 781 u_long idx; 782 u_long len, newst, foundl, cn, l; 783 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 784 u_int map; 785 786 #ifdef MSDOSFS_DEBUG 787 printf("clusteralloc(): find %lu clusters\n",count); 788 #endif 789 if (start) { 790 if ((len = chainlength(pmp, start, count)) >= count) 791 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 792 } else 793 len = 0; 794 795 /* 796 * Start at a (pseudo) random place to maximize cluster runs 797 * under multiple writers. 798 */ 799 newst = random() % (pmp->pm_maxcluster + 1); 800 foundl = 0; 801 802 for (cn = newst; cn <= pmp->pm_maxcluster;) { 803 idx = cn / N_INUSEBITS; 804 map = pmp->pm_inusemap[idx]; 805 map |= (1 << (cn % N_INUSEBITS)) - 1; 806 if (map != (u_int)-1) { 807 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 808 if ((l = chainlength(pmp, cn, count)) >= count) 809 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 810 if (l > foundl) { 811 foundcn = cn; 812 foundl = l; 813 } 814 cn += l + 1; 815 continue; 816 } 817 cn += N_INUSEBITS - cn % N_INUSEBITS; 818 } 819 for (cn = 0; cn < newst;) { 820 idx = cn / N_INUSEBITS; 821 map = pmp->pm_inusemap[idx]; 822 map |= (1 << (cn % N_INUSEBITS)) - 1; 823 if (map != (u_int)-1) { 824 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 825 if ((l = chainlength(pmp, cn, count)) >= count) 826 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 827 if (l > foundl) { 828 foundcn = cn; 829 foundl = l; 830 } 831 cn += l + 1; 832 continue; 833 } 834 cn += N_INUSEBITS - cn % N_INUSEBITS; 835 } 836 837 if (!foundl) 838 return (ENOSPC); 839 840 if (len) 841 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 842 else 843 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 844 } 845 846 847 /* 848 * Free a chain of clusters. 849 * 850 * pmp - address of the msdosfs mount structure for the filesystem 851 * containing the cluster chain to be freed. 852 * startcluster - number of the 1st cluster in the chain of clusters to be 853 * freed. 854 */ 855 int 856 freeclusterchain(pmp, cluster) 857 struct msdosfsmount *pmp; 858 u_long cluster; 859 { 860 int error; 861 struct buf *bp = NULL; 862 u_long bn, bo, bsize, byteoffset; 863 u_long readcn, lbn = -1; 864 865 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 866 byteoffset = FATOFS(pmp, cluster); 867 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 868 if (lbn != bn) { 869 if (bp) 870 updatefats(pmp, bp, lbn); 871 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 872 if (error) { 873 brelse(bp); 874 return (error); 875 } 876 lbn = bn; 877 } 878 usemap_free(pmp, cluster); 879 switch (pmp->pm_fatmask) { 880 case FAT12_MASK: 881 readcn = getushort(&bp->b_data[bo]); 882 if (cluster & 1) { 883 cluster = readcn >> 4; 884 readcn &= 0x000f; 885 readcn |= MSDOSFSFREE << 4; 886 } else { 887 cluster = readcn; 888 readcn &= 0xf000; 889 readcn |= MSDOSFSFREE & 0xfff; 890 } 891 putushort(&bp->b_data[bo], readcn); 892 break; 893 case FAT16_MASK: 894 cluster = getushort(&bp->b_data[bo]); 895 putushort(&bp->b_data[bo], MSDOSFSFREE); 896 break; 897 case FAT32_MASK: 898 cluster = getulong(&bp->b_data[bo]); 899 putulong(&bp->b_data[bo], 900 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 901 break; 902 } 903 cluster &= pmp->pm_fatmask; 904 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 905 cluster |= pmp->pm_fatmask; 906 } 907 if (bp) 908 updatefats(pmp, bp, bn); 909 return (0); 910 } 911 912 /* 913 * Read in fat blocks looking for free clusters. For every free cluster 914 * found turn off its corresponding bit in the pm_inusemap. 915 */ 916 int 917 fillinusemap(pmp) 918 struct msdosfsmount *pmp; 919 { 920 struct buf *bp = NULL; 921 u_long cn, readcn; 922 int error; 923 u_long bn, bo, bsize, byteoffset; 924 925 /* 926 * Mark all clusters in use, we mark the free ones in the fat scan 927 * loop further down. 928 */ 929 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 930 pmp->pm_inusemap[cn] = (u_int)-1; 931 932 /* 933 * Figure how many free clusters are in the filesystem by ripping 934 * through the fat counting the number of entries whose content is 935 * zero. These represent free clusters. 936 */ 937 pmp->pm_freeclustercount = 0; 938 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 939 byteoffset = FATOFS(pmp, cn); 940 bo = byteoffset % pmp->pm_fatblocksize; 941 if (!bo || !bp) { 942 /* Read new FAT block */ 943 if (bp) 944 brelse(bp); 945 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 946 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 947 if (error) { 948 brelse(bp); 949 return (error); 950 } 951 } 952 if (FAT32(pmp)) 953 readcn = getulong(&bp->b_data[bo]); 954 else 955 readcn = getushort(&bp->b_data[bo]); 956 if (FAT12(pmp) && (cn & 1)) 957 readcn >>= 4; 958 readcn &= pmp->pm_fatmask; 959 960 if (readcn == 0) 961 usemap_free(pmp, cn); 962 } 963 brelse(bp); 964 return (0); 965 } 966 967 /* 968 * Allocate a new cluster and chain it onto the end of the file. 969 * 970 * dep - the file to extend 971 * count - number of clusters to allocate 972 * bpp - where to return the address of the buf header for the first new 973 * file block 974 * ncp - where to put cluster number of the first newly allocated cluster 975 * If this pointer is 0, do not return the cluster number. 976 * flags - see fat.h 977 * 978 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 979 * the de_flag field of the denode and it does not change the de_FileSize 980 * field. This is left for the caller to do. 981 */ 982 int 983 extendfile(dep, count, bpp, ncp, flags) 984 struct denode *dep; 985 u_long count; 986 struct buf **bpp; 987 u_long *ncp; 988 int flags; 989 { 990 int error; 991 u_long frcn; 992 u_long cn, got; 993 struct msdosfsmount *pmp = dep->de_pmp; 994 struct buf *bp; 995 996 /* 997 * Don't try to extend the root directory 998 */ 999 if (dep->de_StartCluster == MSDOSFSROOT 1000 && (dep->de_Attributes & ATTR_DIRECTORY)) { 1001 printf("extendfile(): attempt to extend root directory\n"); 1002 return (ENOSPC); 1003 } 1004 1005 /* 1006 * If the "file's last cluster" cache entry is empty, and the file 1007 * is not empty, then fill the cache entry by calling pcbmap(). 1008 */ 1009 fc_fileextends++; 1010 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1011 dep->de_StartCluster != 0) { 1012 fc_lfcempty++; 1013 error = pcbmap(dep, 0xffff, 0, &cn, 0); 1014 /* we expect it to return E2BIG */ 1015 if (error != E2BIG) 1016 return (error); 1017 } 1018 1019 while (count > 0) { 1020 /* 1021 * Allocate a new cluster chain and cat onto the end of the 1022 * file. * If the file is empty we make de_StartCluster point 1023 * to the new block. Note that de_StartCluster being 0 is 1024 * sufficient to be sure the file is empty since we exclude 1025 * attempts to extend the root directory above, and the root 1026 * dir is the only file with a startcluster of 0 that has 1027 * blocks allocated (sort of). 1028 */ 1029 if (dep->de_StartCluster == 0) 1030 cn = 0; 1031 else 1032 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1033 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 1034 if (error) 1035 return (error); 1036 1037 count -= got; 1038 1039 /* 1040 * Give them the filesystem relative cluster number if they want 1041 * it. 1042 */ 1043 if (ncp) { 1044 *ncp = cn; 1045 ncp = NULL; 1046 } 1047 1048 if (dep->de_StartCluster == 0) { 1049 dep->de_StartCluster = cn; 1050 frcn = 0; 1051 } else { 1052 error = fatentry(FAT_SET, pmp, 1053 dep->de_fc[FC_LASTFC].fc_fsrcn, 1054 0, cn); 1055 if (error) { 1056 clusterfree(pmp, cn, NULL); 1057 return (error); 1058 } 1059 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1060 } 1061 1062 /* 1063 * Update the "last cluster of the file" entry in the denode's fat 1064 * cache. 1065 */ 1066 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1067 1068 if (flags & DE_CLEAR) { 1069 while (got-- > 0) { 1070 /* 1071 * Get the buf header for the new block of the file. 1072 */ 1073 if (dep->de_Attributes & ATTR_DIRECTORY) 1074 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1075 pmp->pm_bpcluster, 0, 0); 1076 else { 1077 bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++), 1078 pmp->pm_bpcluster, 0, 0); 1079 /* 1080 * Do the bmap now, as in msdosfs_write 1081 */ 1082 if (pcbmap(dep, 1083 de_bn2cn(pmp, bp->b_lblkno), 1084 &bp->b_blkno, 0, 0)) 1085 bp->b_blkno = -1; 1086 if (bp->b_blkno == -1) 1087 panic("extendfile: pcbmap"); 1088 } 1089 clrbuf(bp); 1090 if (bpp) { 1091 *bpp = bp; 1092 bpp = NULL; 1093 } else 1094 bdwrite(bp); 1095 } 1096 } 1097 } 1098 1099 return (0); 1100 }
Cache object: 5b03d3b58d159761b94dad775e7c9414
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