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sys/fs/msdosfs/msdosfs_fat.c
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1 /* $FreeBSD: releng/5.0/sys/fs/msdosfs/msdosfs_fat.c 96755 2002-05-16 21:28:32Z trhodes $ */ 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/bio.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 <fs/msdosfs/bpb.h> 65 #include <fs/msdosfs/msdosfsmount.h> 66 #include <fs/msdosfs/direntry.h> 67 #include <fs/msdosfs/denode.h> 68 #include <fs/msdosfs/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, u_long *retcluster, 85 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, u_long *bnp, 89 u_long *sizep, u_long *bop); 90 static int fatchain(struct msdosfsmount *pmp, u_long start, u_long count, 91 u_long fillwith); 92 static void fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, 93 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(pmp, ofs, bnp, sizep, bop) 103 struct msdosfsmount *pmp; 104 u_long ofs; 105 u_long *bnp; 106 u_long *sizep; 107 u_long *bop; 108 { 109 u_long bn, size; 110 111 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 112 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 113 * DEV_BSIZE; 114 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 115 116 if (bnp) 117 *bnp = bn; 118 if (sizep) 119 *sizep = size; 120 if (bop) 121 *bop = ofs % pmp->pm_fatblocksize; 122 } 123 124 /* 125 * Map the logical cluster number of a file into a physical disk sector 126 * that is filesystem relative. 127 * 128 * dep - address of denode representing the file of interest 129 * findcn - file relative cluster whose filesystem relative cluster number 130 * and/or block number are/is to be found 131 * bnp - address of where to place the filesystem relative block number. 132 * If this pointer is null then don't return this quantity. 133 * cnp - address of where to place the filesystem relative cluster number. 134 * If this pointer is null then don't return this quantity. 135 * 136 * NOTE: Either bnp or cnp must be non-null. 137 * This function has one side effect. If the requested file relative cluster 138 * is beyond the end of file, then the actual number of clusters in the file 139 * is returned in *cnp. This is useful for determining how long a directory is. 140 * If cnp is null, nothing is returned. 141 */ 142 int 143 pcbmap(dep, findcn, bnp, cnp, sp) 144 struct denode *dep; 145 u_long findcn; /* file relative cluster to get */ 146 daddr_t *bnp; /* returned filesys relative blk number */ 147 u_long *cnp; /* returned cluster number */ 148 int *sp; /* returned block size */ 149 { 150 int error; 151 u_long i; 152 u_long cn; 153 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 154 u_long byteoffset; 155 u_long bn; 156 u_long bo; 157 struct buf *bp = NULL; 158 u_long bp_bn = -1; 159 struct msdosfsmount *pmp = dep->de_pmp; 160 u_long bsize; 161 162 fc_bmapcalls++; 163 164 /* 165 * If they don't give us someplace to return a value then don't 166 * bother doing anything. 167 */ 168 if (bnp == NULL && cnp == NULL && sp == NULL) 169 return (0); 170 171 cn = dep->de_StartCluster; 172 /* 173 * The "file" that makes up the root directory is contiguous, 174 * permanently allocated, of fixed size, and is not made up of 175 * clusters. If the cluster number is beyond the end of the root 176 * directory, then return the number of clusters in the file. 177 */ 178 if (cn == MSDOSFSROOT) { 179 if (dep->de_Attributes & ATTR_DIRECTORY) { 180 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 181 if (cnp) 182 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 183 return (E2BIG); 184 } 185 if (bnp) 186 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 187 if (cnp) 188 *cnp = MSDOSFSROOT; 189 if (sp) 190 *sp = min(pmp->pm_bpcluster, 191 dep->de_FileSize - de_cn2off(pmp, findcn)); 192 return (0); 193 } else { /* just an empty file */ 194 if (cnp) 195 *cnp = 0; 196 return (E2BIG); 197 } 198 } 199 200 /* 201 * All other files do I/O in cluster sized blocks 202 */ 203 if (sp) 204 *sp = pmp->pm_bpcluster; 205 206 /* 207 * Rummage around in the fat cache, maybe we can avoid tromping 208 * thru every fat entry for the file. And, keep track of how far 209 * off the cache was from where we wanted to be. 210 */ 211 i = 0; 212 fc_lookup(dep, findcn, &i, &cn); 213 if ((bn = findcn - i) >= LMMAX) 214 fc_largedistance++; 215 else 216 fc_lmdistance[bn]++; 217 218 /* 219 * Handle all other files or directories the normal way. 220 */ 221 for (; i < findcn; i++) { 222 /* 223 * Stop with all reserved clusters, not just with EOF. 224 */ 225 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 226 goto hiteof; 227 byteoffset = FATOFS(pmp, cn); 228 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 229 if (bn != bp_bn) { 230 if (bp) 231 brelse(bp); 232 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 233 if (error) { 234 brelse(bp); 235 return (error); 236 } 237 bp_bn = bn; 238 } 239 prevcn = cn; 240 if (FAT32(pmp)) 241 cn = getulong(&bp->b_data[bo]); 242 else 243 cn = getushort(&bp->b_data[bo]); 244 if (FAT12(pmp) && (prevcn & 1)) 245 cn >>= 4; 246 cn &= pmp->pm_fatmask; 247 248 /* 249 * Force the special cluster numbers 250 * to be the same for all cluster sizes 251 * to let the rest of msdosfs handle 252 * all cases the same. 253 */ 254 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 255 cn |= ~pmp->pm_fatmask; 256 } 257 258 if (!MSDOSFSEOF(pmp, cn)) { 259 if (bp) 260 brelse(bp); 261 if (bnp) 262 *bnp = cntobn(pmp, cn); 263 if (cnp) 264 *cnp = cn; 265 fc_setcache(dep, FC_LASTMAP, i, cn); 266 return (0); 267 } 268 269 hiteof:; 270 if (cnp) 271 *cnp = i; 272 if (bp) 273 brelse(bp); 274 /* update last file cluster entry in the fat cache */ 275 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 276 return (E2BIG); 277 } 278 279 /* 280 * Find the closest entry in the fat cache to the cluster we are looking 281 * for. 282 */ 283 static void 284 fc_lookup(dep, findcn, frcnp, fsrcnp) 285 struct denode *dep; 286 u_long findcn; 287 u_long *frcnp; 288 u_long *fsrcnp; 289 { 290 int i; 291 u_long cn; 292 struct fatcache *closest = 0; 293 294 for (i = 0; i < FC_SIZE; i++) { 295 cn = dep->de_fc[i].fc_frcn; 296 if (cn != FCE_EMPTY && cn <= findcn) { 297 if (closest == 0 || cn > closest->fc_frcn) 298 closest = &dep->de_fc[i]; 299 } 300 } 301 if (closest) { 302 *frcnp = closest->fc_frcn; 303 *fsrcnp = closest->fc_fsrcn; 304 } 305 } 306 307 /* 308 * Purge the fat cache in denode dep of all entries relating to file 309 * relative cluster frcn and beyond. 310 */ 311 void 312 fc_purge(dep, frcn) 313 struct denode *dep; 314 u_int frcn; 315 { 316 int i; 317 struct fatcache *fcp; 318 319 fcp = dep->de_fc; 320 for (i = 0; i < FC_SIZE; i++, fcp++) { 321 if (fcp->fc_frcn >= frcn) 322 fcp->fc_frcn = FCE_EMPTY; 323 } 324 } 325 326 /* 327 * Update the fat. 328 * If mirroring the fat, update all copies, with the first copy as last. 329 * Else update only the current fat (ignoring the others). 330 * 331 * pmp - msdosfsmount structure for filesystem to update 332 * bp - addr of modified fat block 333 * fatbn - block number relative to begin of filesystem of the modified fat block. 334 */ 335 static void 336 updatefats(pmp, bp, fatbn) 337 struct msdosfsmount *pmp; 338 struct buf *bp; 339 u_long fatbn; 340 { 341 int i; 342 struct buf *bpn; 343 344 #ifdef MSDOSFS_DEBUG 345 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn); 346 #endif 347 348 /* 349 * If we have an FSInfo block, update it. 350 */ 351 if (pmp->pm_fsinfo) { 352 u_long cn = pmp->pm_nxtfree; 353 354 if (pmp->pm_freeclustercount 355 && (pmp->pm_inusemap[cn / N_INUSEBITS] 356 & (1 << (cn % N_INUSEBITS)))) { 357 /* 358 * The cluster indicated in FSInfo isn't free 359 * any longer. Got get a new free one. 360 */ 361 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS) 362 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 363 break; 364 pmp->pm_nxtfree = cn 365 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 366 ^ (u_int)-1) - 1; 367 } 368 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), 369 NOCRED, &bpn) != 0) { 370 /* 371 * Ignore the error, but turn off FSInfo update for the future. 372 */ 373 pmp->pm_fsinfo = 0; 374 brelse(bpn); 375 } else { 376 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 377 378 putulong(fp->fsinfree, pmp->pm_freeclustercount); 379 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 380 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 381 bwrite(bpn); 382 else 383 bdwrite(bpn); 384 } 385 } 386 387 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 388 /* 389 * Now copy the block(s) of the modified fat to the other copies of 390 * the fat and write them out. This is faster than reading in the 391 * other fats and then writing them back out. This could tie up 392 * the fat for quite a while. Preventing others from accessing it. 393 * To prevent us from going after the fat quite so much we use 394 * delayed writes, unless they specfied "synchronous" when the 395 * filesystem was mounted. If synch is asked for then use 396 * bwrite()'s and really slow things down. 397 */ 398 for (i = 1; i < pmp->pm_FATs; i++) { 399 fatbn += pmp->pm_FATsecs; 400 /* getblk() never fails */ 401 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 402 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 403 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 404 bwrite(bpn); 405 else 406 bdwrite(bpn); 407 } 408 } 409 410 /* 411 * Write out the first (or current) fat last. 412 */ 413 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 414 bwrite(bp); 415 else 416 bdwrite(bp); 417 /* 418 * Maybe update fsinfo sector here? 419 */ 420 } 421 422 /* 423 * Updating entries in 12 bit fats is a pain in the butt. 424 * 425 * The following picture shows where nibbles go when moving from a 12 bit 426 * cluster number into the appropriate bytes in the FAT. 427 * 428 * byte m byte m+1 byte m+2 429 * +----+----+ +----+----+ +----+----+ 430 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 431 * +----+----+ +----+----+ +----+----+ 432 * 433 * +----+----+----+ +----+----+----+ 434 * | 3 0 1 | | 4 5 2 | 435 * +----+----+----+ +----+----+----+ 436 * cluster n cluster n+1 437 * 438 * Where n is even. m = n + (n >> 2) 439 * 440 */ 441 static __inline void 442 usemap_alloc(pmp, cn) 443 struct msdosfsmount *pmp; 444 u_long cn; 445 { 446 447 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 448 pmp->pm_freeclustercount--; 449 } 450 451 static __inline void 452 usemap_free(pmp, cn) 453 struct msdosfsmount *pmp; 454 u_long cn; 455 { 456 457 pmp->pm_freeclustercount++; 458 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 459 } 460 461 int 462 clusterfree(pmp, cluster, oldcnp) 463 struct msdosfsmount *pmp; 464 u_long cluster; 465 u_long *oldcnp; 466 { 467 int error; 468 u_long oldcn; 469 470 usemap_free(pmp, cluster); 471 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 472 if (error) { 473 usemap_alloc(pmp, cluster); 474 return (error); 475 } 476 /* 477 * If the cluster was successfully marked free, then update 478 * the count of free clusters, and turn off the "allocated" 479 * bit in the "in use" cluster bit map. 480 */ 481 if (oldcnp) 482 *oldcnp = oldcn; 483 return (0); 484 } 485 486 /* 487 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 488 * 489 * function - whether to get or set a fat entry 490 * pmp - address of the msdosfsmount structure for the filesystem 491 * whose fat is to be manipulated. 492 * cn - which cluster is of interest 493 * oldcontents - address of a word that is to receive the contents of the 494 * cluster'th entry if this is a get function 495 * newcontents - the new value to be written into the cluster'th element of 496 * the fat if this is a set function. 497 * 498 * This function can also be used to free a cluster by setting the fat entry 499 * for a cluster to 0. 500 * 501 * All copies of the fat are updated if this is a set function. NOTE: If 502 * fatentry() marks a cluster as free it does not update the inusemap in 503 * the msdosfsmount structure. This is left to the caller. 504 */ 505 int 506 fatentry(function, pmp, cn, oldcontents, newcontents) 507 int function; 508 struct msdosfsmount *pmp; 509 u_long cn; 510 u_long *oldcontents; 511 u_long newcontents; 512 { 513 int error; 514 u_long readcn; 515 u_long bn, bo, bsize, byteoffset; 516 struct buf *bp; 517 518 #ifdef MSDOSFS_DEBUG 519 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 520 function, pmp, cn, oldcontents, newcontents); 521 #endif 522 523 #ifdef DIAGNOSTIC 524 /* 525 * Be sure they asked us to do something. 526 */ 527 if ((function & (FAT_SET | FAT_GET)) == 0) { 528 printf("fatentry(): function code doesn't specify get or set\n"); 529 return (EINVAL); 530 } 531 532 /* 533 * If they asked us to return a cluster number but didn't tell us 534 * where to put it, give them an error. 535 */ 536 if ((function & FAT_GET) && oldcontents == NULL) { 537 printf("fatentry(): get function with no place to put result\n"); 538 return (EINVAL); 539 } 540 #endif 541 542 /* 543 * Be sure the requested cluster is in the filesystem. 544 */ 545 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 546 return (EINVAL); 547 548 byteoffset = FATOFS(pmp, cn); 549 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 550 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 551 if (error) { 552 brelse(bp); 553 return (error); 554 } 555 556 if (function & FAT_GET) { 557 if (FAT32(pmp)) 558 readcn = getulong(&bp->b_data[bo]); 559 else 560 readcn = getushort(&bp->b_data[bo]); 561 if (FAT12(pmp) & (cn & 1)) 562 readcn >>= 4; 563 readcn &= pmp->pm_fatmask; 564 /* map reserved fat entries to same values for all fats */ 565 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 566 readcn |= ~pmp->pm_fatmask; 567 *oldcontents = readcn; 568 } 569 if (function & FAT_SET) { 570 switch (pmp->pm_fatmask) { 571 case FAT12_MASK: 572 readcn = getushort(&bp->b_data[bo]); 573 if (cn & 1) { 574 readcn &= 0x000f; 575 readcn |= newcontents << 4; 576 } else { 577 readcn &= 0xf000; 578 readcn |= newcontents & 0xfff; 579 } 580 putushort(&bp->b_data[bo], readcn); 581 break; 582 case FAT16_MASK: 583 putushort(&bp->b_data[bo], newcontents); 584 break; 585 case FAT32_MASK: 586 /* 587 * According to spec we have to retain the 588 * high order bits of the fat entry. 589 */ 590 readcn = getulong(&bp->b_data[bo]); 591 readcn &= ~FAT32_MASK; 592 readcn |= newcontents & FAT32_MASK; 593 putulong(&bp->b_data[bo], readcn); 594 break; 595 } 596 updatefats(pmp, bp, bn); 597 bp = NULL; 598 pmp->pm_fmod = 1; 599 } 600 if (bp) 601 brelse(bp); 602 return (0); 603 } 604 605 /* 606 * Update a contiguous cluster chain 607 * 608 * pmp - mount point 609 * start - first cluster of chain 610 * count - number of clusters in chain 611 * fillwith - what to write into fat entry of last cluster 612 */ 613 static int 614 fatchain(pmp, start, count, fillwith) 615 struct msdosfsmount *pmp; 616 u_long start; 617 u_long count; 618 u_long fillwith; 619 { 620 int error; 621 u_long bn, bo, bsize, byteoffset, readcn, newc; 622 struct buf *bp; 623 624 #ifdef MSDOSFS_DEBUG 625 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 626 pmp, start, count, fillwith); 627 #endif 628 /* 629 * Be sure the clusters are in the filesystem. 630 */ 631 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 632 return (EINVAL); 633 634 while (count > 0) { 635 byteoffset = FATOFS(pmp, start); 636 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 637 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 638 if (error) { 639 brelse(bp); 640 return (error); 641 } 642 while (count > 0) { 643 start++; 644 newc = --count > 0 ? start : fillwith; 645 switch (pmp->pm_fatmask) { 646 case FAT12_MASK: 647 readcn = getushort(&bp->b_data[bo]); 648 if (start & 1) { 649 readcn &= 0xf000; 650 readcn |= newc & 0xfff; 651 } else { 652 readcn &= 0x000f; 653 readcn |= newc << 4; 654 } 655 putushort(&bp->b_data[bo], readcn); 656 bo++; 657 if (!(start & 1)) 658 bo++; 659 break; 660 case FAT16_MASK: 661 putushort(&bp->b_data[bo], newc); 662 bo += 2; 663 break; 664 case FAT32_MASK: 665 readcn = getulong(&bp->b_data[bo]); 666 readcn &= ~pmp->pm_fatmask; 667 readcn |= newc & pmp->pm_fatmask; 668 putulong(&bp->b_data[bo], readcn); 669 bo += 4; 670 break; 671 } 672 if (bo >= bsize) 673 break; 674 } 675 updatefats(pmp, bp, bn); 676 } 677 pmp->pm_fmod = 1; 678 return (0); 679 } 680 681 /* 682 * Check the length of a free cluster chain starting at start. 683 * 684 * pmp - mount point 685 * start - start of chain 686 * count - maximum interesting length 687 */ 688 static int 689 chainlength(pmp, start, count) 690 struct msdosfsmount *pmp; 691 u_long start; 692 u_long count; 693 { 694 u_long idx, max_idx; 695 u_int map; 696 u_long len; 697 698 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 699 idx = start / N_INUSEBITS; 700 start %= N_INUSEBITS; 701 map = pmp->pm_inusemap[idx]; 702 map &= ~((1 << start) - 1); 703 if (map) { 704 len = ffs(map) - 1 - start; 705 return (len > count ? count : len); 706 } 707 len = N_INUSEBITS - start; 708 if (len >= count) 709 return (count); 710 while (++idx <= max_idx) { 711 if (len >= count) 712 break; 713 map = pmp->pm_inusemap[idx]; 714 if (map) { 715 len += ffs(map) - 1; 716 break; 717 } 718 len += N_INUSEBITS; 719 } 720 return (len > count ? count : len); 721 } 722 723 /* 724 * Allocate contigous free clusters. 725 * 726 * pmp - mount point. 727 * start - start of cluster chain. 728 * count - number of clusters to allocate. 729 * fillwith - put this value into the fat entry for the 730 * last allocated cluster. 731 * retcluster - put the first allocated cluster's number here. 732 * got - how many clusters were actually allocated. 733 */ 734 static int 735 chainalloc(pmp, start, count, fillwith, retcluster, got) 736 struct msdosfsmount *pmp; 737 u_long start; 738 u_long count; 739 u_long fillwith; 740 u_long *retcluster; 741 u_long *got; 742 { 743 int error; 744 u_long cl, n; 745 746 for (cl = start, n = count; n-- > 0;) 747 usemap_alloc(pmp, cl++); 748 749 error = fatchain(pmp, start, count, fillwith); 750 if (error != 0) 751 return (error); 752 #ifdef MSDOSFS_DEBUG 753 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 754 start, count); 755 #endif 756 if (retcluster) 757 *retcluster = start; 758 if (got) 759 *got = count; 760 return (0); 761 } 762 763 /* 764 * Allocate contiguous free clusters. 765 * 766 * pmp - mount point. 767 * start - preferred start of cluster chain. 768 * count - number of clusters requested. 769 * fillwith - put this value into the fat entry for the 770 * last allocated cluster. 771 * retcluster - put the first allocated cluster's number here. 772 * got - how many clusters were actually allocated. 773 */ 774 int 775 clusteralloc(pmp, start, count, fillwith, retcluster, got) 776 struct msdosfsmount *pmp; 777 u_long start; 778 u_long count; 779 u_long fillwith; 780 u_long *retcluster; 781 u_long *got; 782 { 783 u_long idx; 784 u_long len, newst, foundl, cn, l; 785 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 786 u_int map; 787 788 #ifdef MSDOSFS_DEBUG 789 printf("clusteralloc(): find %lu clusters\n",count); 790 #endif 791 if (start) { 792 if ((len = chainlength(pmp, start, count)) >= count) 793 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 794 } else 795 len = 0; 796 797 /* 798 * Start at a (pseudo) random place to maximize cluster runs 799 * under multiple writers. 800 */ 801 newst = random() % (pmp->pm_maxcluster + 1); 802 foundl = 0; 803 804 for (cn = newst; cn <= pmp->pm_maxcluster;) { 805 idx = cn / N_INUSEBITS; 806 map = pmp->pm_inusemap[idx]; 807 map |= (1 << (cn % N_INUSEBITS)) - 1; 808 if (map != (u_int)-1) { 809 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 810 if ((l = chainlength(pmp, cn, count)) >= count) 811 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 812 if (l > foundl) { 813 foundcn = cn; 814 foundl = l; 815 } 816 cn += l + 1; 817 continue; 818 } 819 cn += N_INUSEBITS - cn % N_INUSEBITS; 820 } 821 for (cn = 0; cn < newst;) { 822 idx = cn / N_INUSEBITS; 823 map = pmp->pm_inusemap[idx]; 824 map |= (1 << (cn % N_INUSEBITS)) - 1; 825 if (map != (u_int)-1) { 826 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 827 if ((l = chainlength(pmp, cn, count)) >= count) 828 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 829 if (l > foundl) { 830 foundcn = cn; 831 foundl = l; 832 } 833 cn += l + 1; 834 continue; 835 } 836 cn += N_INUSEBITS - cn % N_INUSEBITS; 837 } 838 839 if (!foundl) 840 return (ENOSPC); 841 842 if (len) 843 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 844 else 845 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 846 } 847 848 849 /* 850 * Free a chain of clusters. 851 * 852 * pmp - address of the msdosfs mount structure for the filesystem 853 * containing the cluster chain to be freed. 854 * startcluster - number of the 1st cluster in the chain of clusters to be 855 * freed. 856 */ 857 int 858 freeclusterchain(pmp, cluster) 859 struct msdosfsmount *pmp; 860 u_long cluster; 861 { 862 int error; 863 struct buf *bp = NULL; 864 u_long bn, bo, bsize, byteoffset; 865 u_long readcn, lbn = -1; 866 867 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 868 byteoffset = FATOFS(pmp, cluster); 869 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 870 if (lbn != bn) { 871 if (bp) 872 updatefats(pmp, bp, lbn); 873 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 874 if (error) { 875 brelse(bp); 876 return (error); 877 } 878 lbn = bn; 879 } 880 usemap_free(pmp, cluster); 881 switch (pmp->pm_fatmask) { 882 case FAT12_MASK: 883 readcn = getushort(&bp->b_data[bo]); 884 if (cluster & 1) { 885 cluster = readcn >> 4; 886 readcn &= 0x000f; 887 readcn |= MSDOSFSFREE << 4; 888 } else { 889 cluster = readcn; 890 readcn &= 0xf000; 891 readcn |= MSDOSFSFREE & 0xfff; 892 } 893 putushort(&bp->b_data[bo], readcn); 894 break; 895 case FAT16_MASK: 896 cluster = getushort(&bp->b_data[bo]); 897 putushort(&bp->b_data[bo], MSDOSFSFREE); 898 break; 899 case FAT32_MASK: 900 cluster = getulong(&bp->b_data[bo]); 901 putulong(&bp->b_data[bo], 902 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 903 break; 904 } 905 cluster &= pmp->pm_fatmask; 906 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 907 cluster |= pmp->pm_fatmask; 908 } 909 if (bp) 910 updatefats(pmp, bp, bn); 911 return (0); 912 } 913 914 /* 915 * Read in fat blocks looking for free clusters. For every free cluster 916 * found turn off its corresponding bit in the pm_inusemap. 917 */ 918 int 919 fillinusemap(pmp) 920 struct msdosfsmount *pmp; 921 { 922 struct buf *bp = NULL; 923 u_long cn, readcn; 924 int error; 925 u_long bn, bo, bsize, byteoffset; 926 927 /* 928 * Mark all clusters in use, we mark the free ones in the fat scan 929 * loop further down. 930 */ 931 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 932 pmp->pm_inusemap[cn] = (u_int)-1; 933 934 /* 935 * Figure how many free clusters are in the filesystem by ripping 936 * through the fat counting the number of entries whose content is 937 * zero. These represent free clusters. 938 */ 939 pmp->pm_freeclustercount = 0; 940 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 941 byteoffset = FATOFS(pmp, cn); 942 bo = byteoffset % pmp->pm_fatblocksize; 943 if (!bo || !bp) { 944 /* Read new FAT block */ 945 if (bp) 946 brelse(bp); 947 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 948 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 949 if (error) { 950 brelse(bp); 951 return (error); 952 } 953 } 954 if (FAT32(pmp)) 955 readcn = getulong(&bp->b_data[bo]); 956 else 957 readcn = getushort(&bp->b_data[bo]); 958 if (FAT12(pmp) && (cn & 1)) 959 readcn >>= 4; 960 readcn &= pmp->pm_fatmask; 961 962 if (readcn == 0) 963 usemap_free(pmp, cn); 964 } 965 brelse(bp); 966 return (0); 967 } 968 969 /* 970 * Allocate a new cluster and chain it onto the end of the file. 971 * 972 * dep - the file to extend 973 * count - number of clusters to allocate 974 * bpp - where to return the address of the buf header for the first new 975 * file block 976 * ncp - where to put cluster number of the first newly allocated cluster 977 * If this pointer is 0, do not return the cluster number. 978 * flags - see fat.h 979 * 980 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 981 * the de_flag field of the denode and it does not change the de_FileSize 982 * field. This is left for the caller to do. 983 */ 984 int 985 extendfile(dep, count, bpp, ncp, flags) 986 struct denode *dep; 987 u_long count; 988 struct buf **bpp; 989 u_long *ncp; 990 int flags; 991 { 992 int error; 993 u_long frcn; 994 u_long cn, got; 995 struct msdosfsmount *pmp = dep->de_pmp; 996 struct buf *bp; 997 daddr_t blkno; 998 999 /* 1000 * Don't try to extend the root directory 1001 */ 1002 if (dep->de_StartCluster == MSDOSFSROOT 1003 && (dep->de_Attributes & ATTR_DIRECTORY)) { 1004 printf("extendfile(): attempt to extend root directory\n"); 1005 return (ENOSPC); 1006 } 1007 1008 /* 1009 * If the "file's last cluster" cache entry is empty, and the file 1010 * is not empty, then fill the cache entry by calling pcbmap(). 1011 */ 1012 fc_fileextends++; 1013 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1014 dep->de_StartCluster != 0) { 1015 fc_lfcempty++; 1016 error = pcbmap(dep, 0xffff, 0, &cn, 0); 1017 /* we expect it to return E2BIG */ 1018 if (error != E2BIG) 1019 return (error); 1020 } 1021 1022 while (count > 0) { 1023 /* 1024 * Allocate a new cluster chain and cat onto the end of the 1025 * file. * If the file is empty we make de_StartCluster point 1026 * to the new block. Note that de_StartCluster being 0 is 1027 * sufficient to be sure the file is empty since we exclude 1028 * attempts to extend the root directory above, and the root 1029 * dir is the only file with a startcluster of 0 that has 1030 * blocks allocated (sort of). 1031 */ 1032 if (dep->de_StartCluster == 0) 1033 cn = 0; 1034 else 1035 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1036 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 1037 if (error) 1038 return (error); 1039 1040 count -= got; 1041 1042 /* 1043 * Give them the filesystem relative cluster number if they want 1044 * it. 1045 */ 1046 if (ncp) { 1047 *ncp = cn; 1048 ncp = NULL; 1049 } 1050 1051 if (dep->de_StartCluster == 0) { 1052 dep->de_StartCluster = cn; 1053 frcn = 0; 1054 } else { 1055 error = fatentry(FAT_SET, pmp, 1056 dep->de_fc[FC_LASTFC].fc_fsrcn, 1057 0, cn); 1058 if (error) { 1059 clusterfree(pmp, cn, NULL); 1060 return (error); 1061 } 1062 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1063 } 1064 1065 /* 1066 * Update the "last cluster of the file" entry in the denode's fat 1067 * cache. 1068 */ 1069 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1070 1071 if (flags & DE_CLEAR) { 1072 while (got-- > 0) { 1073 /* 1074 * Get the buf header for the new block of the file. 1075 */ 1076 if (dep->de_Attributes & ATTR_DIRECTORY) 1077 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1078 pmp->pm_bpcluster, 0, 0); 1079 else { 1080 bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++), 1081 pmp->pm_bpcluster, 0, 0); 1082 /* 1083 * Do the bmap now, as in msdosfs_write 1084 */ 1085 if (pcbmap(dep, 1086 de_bn2cn(pmp, bp->b_lblkno), 1087 &blkno, 0, 0)) 1088 bp->b_blkno = -1; 1089 if (bp->b_blkno == -1) 1090 panic("extendfile: pcbmap"); 1091 else 1092 bp->b_blkno = blkno; 1093 } 1094 clrbuf(bp); 1095 if (bpp) { 1096 *bpp = bp; 1097 bpp = NULL; 1098 } else 1099 bdwrite(bp); 1100 } 1101 } 1102 } 1103 1104 return (0); 1105 }
Cache object: 8b10aeab3307cbbf6f909f7cac80b9a3
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