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sys/msdosfs/msdosfs_fat.c
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1 /* $FreeBSD$ */ 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 * DEV_BSIZE; 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, fsi_size(pmp), 368 NOCRED, &bpn) != 0) { 369 /* 370 * Ignore the error, but turn off FSInfo update for the future. 371 */ 372 pmp->pm_fsinfo = 0; 373 brelse(bpn); 374 } else { 375 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 376 377 putulong(fp->fsinfree, pmp->pm_freeclustercount); 378 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 379 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 380 bwrite(bpn); 381 else 382 bdwrite(bpn); 383 } 384 } 385 386 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 387 /* 388 * Now copy the block(s) of the modified fat to the other copies of 389 * the fat and write them out. This is faster than reading in the 390 * other fats and then writing them back out. This could tie up 391 * the fat for quite a while. Preventing others from accessing it. 392 * To prevent us from going after the fat quite so much we use 393 * delayed writes, unless they specfied "synchronous" when the 394 * filesystem was mounted. If synch is asked for then use 395 * bwrite()'s and really slow things down. 396 */ 397 for (i = 1; i < pmp->pm_FATs; i++) { 398 fatbn += pmp->pm_FATsecs; 399 /* getblk() never fails */ 400 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0); 401 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 402 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 403 bwrite(bpn); 404 else 405 bdwrite(bpn); 406 } 407 } 408 409 /* 410 * Write out the first (or current) fat last. 411 */ 412 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 413 bwrite(bp); 414 else 415 bdwrite(bp); 416 /* 417 * Maybe update fsinfo sector here? 418 */ 419 } 420 421 /* 422 * Updating entries in 12 bit fats is a pain in the butt. 423 * 424 * The following picture shows where nibbles go when moving from a 12 bit 425 * cluster number into the appropriate bytes in the FAT. 426 * 427 * byte m byte m+1 byte m+2 428 * +----+----+ +----+----+ +----+----+ 429 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 430 * +----+----+ +----+----+ +----+----+ 431 * 432 * +----+----+----+ +----+----+----+ 433 * | 3 0 1 | | 4 5 2 | 434 * +----+----+----+ +----+----+----+ 435 * cluster n cluster n+1 436 * 437 * Where n is even. m = n + (n >> 2) 438 * 439 */ 440 static __inline void 441 usemap_alloc(pmp, cn) 442 struct msdosfsmount *pmp; 443 u_long cn; 444 { 445 446 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 447 pmp->pm_freeclustercount--; 448 } 449 450 static __inline void 451 usemap_free(pmp, cn) 452 struct msdosfsmount *pmp; 453 u_long cn; 454 { 455 456 pmp->pm_freeclustercount++; 457 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 458 } 459 460 int 461 clusterfree(pmp, cluster, oldcnp) 462 struct msdosfsmount *pmp; 463 u_long cluster; 464 u_long *oldcnp; 465 { 466 int error; 467 u_long oldcn; 468 469 usemap_free(pmp, cluster); 470 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 471 if (error) { 472 usemap_alloc(pmp, cluster); 473 return (error); 474 } 475 /* 476 * If the cluster was successfully marked free, then update 477 * the count of free clusters, and turn off the "allocated" 478 * bit in the "in use" cluster bit map. 479 */ 480 if (oldcnp) 481 *oldcnp = oldcn; 482 return (0); 483 } 484 485 /* 486 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 487 * 488 * function - whether to get or set a fat entry 489 * pmp - address of the msdosfsmount structure for the filesystem 490 * whose fat is to be manipulated. 491 * cn - which cluster is of interest 492 * oldcontents - address of a word that is to receive the contents of the 493 * cluster'th entry if this is a get function 494 * newcontents - the new value to be written into the cluster'th element of 495 * the fat if this is a set function. 496 * 497 * This function can also be used to free a cluster by setting the fat entry 498 * for a cluster to 0. 499 * 500 * All copies of the fat are updated if this is a set function. NOTE: If 501 * fatentry() marks a cluster as free it does not update the inusemap in 502 * the msdosfsmount structure. This is left to the caller. 503 */ 504 int 505 fatentry(function, pmp, cn, oldcontents, newcontents) 506 int function; 507 struct msdosfsmount *pmp; 508 u_long cn; 509 u_long *oldcontents; 510 u_long newcontents; 511 { 512 int error; 513 u_long readcn; 514 u_long bn, bo, bsize, byteoffset; 515 struct buf *bp; 516 517 #ifdef MSDOSFS_DEBUG 518 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 519 function, pmp, cn, oldcontents, newcontents); 520 #endif 521 522 #ifdef DIAGNOSTIC 523 /* 524 * Be sure they asked us to do something. 525 */ 526 if ((function & (FAT_SET | FAT_GET)) == 0) { 527 printf("fatentry(): function code doesn't specify get or set\n"); 528 return (EINVAL); 529 } 530 531 /* 532 * If they asked us to return a cluster number but didn't tell us 533 * where to put it, give them an error. 534 */ 535 if ((function & FAT_GET) && oldcontents == NULL) { 536 printf("fatentry(): get function with no place to put result\n"); 537 return (EINVAL); 538 } 539 #endif 540 541 /* 542 * Be sure the requested cluster is in the filesystem. 543 */ 544 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 545 return (EINVAL); 546 547 byteoffset = FATOFS(pmp, cn); 548 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 549 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 550 if (error) { 551 brelse(bp); 552 return (error); 553 } 554 555 if (function & FAT_GET) { 556 if (FAT32(pmp)) 557 readcn = getulong(&bp->b_data[bo]); 558 else 559 readcn = getushort(&bp->b_data[bo]); 560 if (FAT12(pmp) & (cn & 1)) 561 readcn >>= 4; 562 readcn &= pmp->pm_fatmask; 563 /* map reserved fat entries to same values for all fats */ 564 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 565 readcn |= ~pmp->pm_fatmask; 566 *oldcontents = readcn; 567 } 568 if (function & FAT_SET) { 569 switch (pmp->pm_fatmask) { 570 case FAT12_MASK: 571 readcn = getushort(&bp->b_data[bo]); 572 if (cn & 1) { 573 readcn &= 0x000f; 574 readcn |= newcontents << 4; 575 } else { 576 readcn &= 0xf000; 577 readcn |= newcontents & 0xfff; 578 } 579 putushort(&bp->b_data[bo], readcn); 580 break; 581 case FAT16_MASK: 582 putushort(&bp->b_data[bo], newcontents); 583 break; 584 case FAT32_MASK: 585 /* 586 * According to spec we have to retain the 587 * high order bits of the fat entry. 588 */ 589 readcn = getulong(&bp->b_data[bo]); 590 readcn &= ~FAT32_MASK; 591 readcn |= newcontents & FAT32_MASK; 592 putulong(&bp->b_data[bo], readcn); 593 break; 594 } 595 updatefats(pmp, bp, bn); 596 bp = NULL; 597 pmp->pm_fmod = 1; 598 } 599 if (bp) 600 brelse(bp); 601 return (0); 602 } 603 604 /* 605 * Update a contiguous cluster chain 606 * 607 * pmp - mount point 608 * start - first cluster of chain 609 * count - number of clusters in chain 610 * fillwith - what to write into fat entry of last cluster 611 */ 612 static int 613 fatchain(pmp, start, count, fillwith) 614 struct msdosfsmount *pmp; 615 u_long start; 616 u_long count; 617 u_long fillwith; 618 { 619 int error; 620 u_long bn, bo, bsize, byteoffset, readcn, newc; 621 struct buf *bp; 622 623 #ifdef MSDOSFS_DEBUG 624 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 625 pmp, start, count, fillwith); 626 #endif 627 /* 628 * Be sure the clusters are in the filesystem. 629 */ 630 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 631 return (EINVAL); 632 633 while (count > 0) { 634 byteoffset = FATOFS(pmp, start); 635 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 636 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 637 if (error) { 638 brelse(bp); 639 return (error); 640 } 641 while (count > 0) { 642 start++; 643 newc = --count > 0 ? start : fillwith; 644 switch (pmp->pm_fatmask) { 645 case FAT12_MASK: 646 readcn = getushort(&bp->b_data[bo]); 647 if (start & 1) { 648 readcn &= 0xf000; 649 readcn |= newc & 0xfff; 650 } else { 651 readcn &= 0x000f; 652 readcn |= newc << 4; 653 } 654 putushort(&bp->b_data[bo], readcn); 655 bo++; 656 if (!(start & 1)) 657 bo++; 658 break; 659 case FAT16_MASK: 660 putushort(&bp->b_data[bo], newc); 661 bo += 2; 662 break; 663 case FAT32_MASK: 664 readcn = getulong(&bp->b_data[bo]); 665 readcn &= ~pmp->pm_fatmask; 666 readcn |= newc & pmp->pm_fatmask; 667 putulong(&bp->b_data[bo], readcn); 668 bo += 4; 669 break; 670 } 671 if (bo >= bsize) 672 break; 673 } 674 updatefats(pmp, bp, bn); 675 } 676 pmp->pm_fmod = 1; 677 return (0); 678 } 679 680 /* 681 * Check the length of a free cluster chain starting at start. 682 * 683 * pmp - mount point 684 * start - start of chain 685 * count - maximum interesting length 686 */ 687 static int 688 chainlength(pmp, start, count) 689 struct msdosfsmount *pmp; 690 u_long start; 691 u_long count; 692 { 693 u_long idx, max_idx; 694 u_int map; 695 u_long len; 696 697 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 698 idx = start / N_INUSEBITS; 699 start %= N_INUSEBITS; 700 map = pmp->pm_inusemap[idx]; 701 map &= ~((1 << start) - 1); 702 if (map) { 703 len = ffs(map) - 1 - start; 704 return (len > count ? count : len); 705 } 706 len = N_INUSEBITS - start; 707 if (len >= count) 708 return (count); 709 while (++idx <= max_idx) { 710 if (len >= count) 711 break; 712 map = pmp->pm_inusemap[idx]; 713 if (map) { 714 len += ffs(map) - 1; 715 break; 716 } 717 len += N_INUSEBITS; 718 } 719 return (len > count ? count : len); 720 } 721 722 /* 723 * Allocate contigous free clusters. 724 * 725 * pmp - mount point. 726 * start - start of cluster chain. 727 * count - number of clusters to allocate. 728 * fillwith - put this value into the fat entry for the 729 * last allocated cluster. 730 * retcluster - put the first allocated cluster's number here. 731 * got - how many clusters were actually allocated. 732 */ 733 static int 734 chainalloc(pmp, start, count, fillwith, retcluster, got) 735 struct msdosfsmount *pmp; 736 u_long start; 737 u_long count; 738 u_long fillwith; 739 u_long *retcluster; 740 u_long *got; 741 { 742 int error; 743 u_long cl, n; 744 745 for (cl = start, n = count; n-- > 0;) 746 usemap_alloc(pmp, cl++); 747 748 error = fatchain(pmp, start, count, fillwith); 749 if (error != 0) 750 return (error); 751 #ifdef MSDOSFS_DEBUG 752 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 753 start, count); 754 #endif 755 if (retcluster) 756 *retcluster = start; 757 if (got) 758 *got = count; 759 return (0); 760 } 761 762 /* 763 * Allocate contiguous free clusters. 764 * 765 * pmp - mount point. 766 * start - preferred start of cluster chain. 767 * count - number of clusters requested. 768 * fillwith - put this value into the fat entry for the 769 * last allocated cluster. 770 * retcluster - put the first allocated cluster's number here. 771 * got - how many clusters were actually allocated. 772 */ 773 int 774 clusteralloc(pmp, start, count, fillwith, retcluster, got) 775 struct msdosfsmount *pmp; 776 u_long start; 777 u_long count; 778 u_long fillwith; 779 u_long *retcluster; 780 u_long *got; 781 { 782 u_long idx; 783 u_long len, newst, foundl, cn, l; 784 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 785 u_int map; 786 787 #ifdef MSDOSFS_DEBUG 788 printf("clusteralloc(): find %lu clusters\n",count); 789 #endif 790 if (start) { 791 if ((len = chainlength(pmp, start, count)) >= count) 792 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 793 } else 794 len = 0; 795 796 /* 797 * Start at a (pseudo) random place to maximize cluster runs 798 * under multiple writers. 799 */ 800 newst = random() % (pmp->pm_maxcluster + 1); 801 foundl = 0; 802 803 for (cn = newst; cn <= pmp->pm_maxcluster;) { 804 idx = cn / N_INUSEBITS; 805 map = pmp->pm_inusemap[idx]; 806 map |= (1 << (cn % N_INUSEBITS)) - 1; 807 if (map != (u_int)-1) { 808 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 809 if ((l = chainlength(pmp, cn, count)) >= count) 810 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 811 if (l > foundl) { 812 foundcn = cn; 813 foundl = l; 814 } 815 cn += l + 1; 816 continue; 817 } 818 cn += N_INUSEBITS - cn % N_INUSEBITS; 819 } 820 for (cn = 0; cn < newst;) { 821 idx = cn / N_INUSEBITS; 822 map = pmp->pm_inusemap[idx]; 823 map |= (1 << (cn % N_INUSEBITS)) - 1; 824 if (map != (u_int)-1) { 825 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 826 if ((l = chainlength(pmp, cn, count)) >= count) 827 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 828 if (l > foundl) { 829 foundcn = cn; 830 foundl = l; 831 } 832 cn += l + 1; 833 continue; 834 } 835 cn += N_INUSEBITS - cn % N_INUSEBITS; 836 } 837 838 if (!foundl) 839 return (ENOSPC); 840 841 if (len) 842 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 843 else 844 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 845 } 846 847 848 /* 849 * Free a chain of clusters. 850 * 851 * pmp - address of the msdosfs mount structure for the filesystem 852 * containing the cluster chain to be freed. 853 * startcluster - number of the 1st cluster in the chain of clusters to be 854 * freed. 855 */ 856 int 857 freeclusterchain(pmp, cluster) 858 struct msdosfsmount *pmp; 859 u_long cluster; 860 { 861 int error; 862 struct buf *bp = NULL; 863 u_long bn, bo, bsize, byteoffset; 864 u_long readcn, lbn = -1; 865 866 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 867 byteoffset = FATOFS(pmp, cluster); 868 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 869 if (lbn != bn) { 870 if (bp) 871 updatefats(pmp, bp, lbn); 872 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 873 if (error) { 874 brelse(bp); 875 return (error); 876 } 877 lbn = bn; 878 } 879 usemap_free(pmp, cluster); 880 switch (pmp->pm_fatmask) { 881 case FAT12_MASK: 882 readcn = getushort(&bp->b_data[bo]); 883 if (cluster & 1) { 884 cluster = readcn >> 4; 885 readcn &= 0x000f; 886 readcn |= MSDOSFSFREE << 4; 887 } else { 888 cluster = readcn; 889 readcn &= 0xf000; 890 readcn |= MSDOSFSFREE & 0xfff; 891 } 892 putushort(&bp->b_data[bo], readcn); 893 break; 894 case FAT16_MASK: 895 cluster = getushort(&bp->b_data[bo]); 896 putushort(&bp->b_data[bo], MSDOSFSFREE); 897 break; 898 case FAT32_MASK: 899 cluster = getulong(&bp->b_data[bo]); 900 putulong(&bp->b_data[bo], 901 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 902 break; 903 } 904 cluster &= pmp->pm_fatmask; 905 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 906 cluster |= pmp->pm_fatmask; 907 } 908 if (bp) 909 updatefats(pmp, bp, bn); 910 return (0); 911 } 912 913 /* 914 * Read in fat blocks looking for free clusters. For every free cluster 915 * found turn off its corresponding bit in the pm_inusemap. 916 */ 917 int 918 fillinusemap(pmp) 919 struct msdosfsmount *pmp; 920 { 921 struct buf *bp = NULL; 922 u_long cn, readcn; 923 int error; 924 u_long bn, bo, bsize, byteoffset; 925 926 /* 927 * Mark all clusters in use, we mark the free ones in the fat scan 928 * loop further down. 929 */ 930 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 931 pmp->pm_inusemap[cn] = (u_int)-1; 932 933 /* 934 * Figure how many free clusters are in the filesystem by ripping 935 * through the fat counting the number of entries whose content is 936 * zero. These represent free clusters. 937 */ 938 pmp->pm_freeclustercount = 0; 939 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 940 byteoffset = FATOFS(pmp, cn); 941 bo = byteoffset % pmp->pm_fatblocksize; 942 if (!bo || !bp) { 943 /* Read new FAT block */ 944 if (bp) 945 brelse(bp); 946 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 947 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp); 948 if (error) { 949 brelse(bp); 950 return (error); 951 } 952 } 953 if (FAT32(pmp)) 954 readcn = getulong(&bp->b_data[bo]); 955 else 956 readcn = getushort(&bp->b_data[bo]); 957 if (FAT12(pmp) && (cn & 1)) 958 readcn >>= 4; 959 readcn &= pmp->pm_fatmask; 960 961 if (readcn == 0) 962 usemap_free(pmp, cn); 963 } 964 brelse(bp); 965 return (0); 966 } 967 968 /* 969 * Allocate a new cluster and chain it onto the end of the file. 970 * 971 * dep - the file to extend 972 * count - number of clusters to allocate 973 * bpp - where to return the address of the buf header for the first new 974 * file block 975 * ncp - where to put cluster number of the first newly allocated cluster 976 * If this pointer is 0, do not return the cluster number. 977 * flags - see fat.h 978 * 979 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 980 * the de_flag field of the denode and it does not change the de_FileSize 981 * field. This is left for the caller to do. 982 */ 983 int 984 extendfile(dep, count, bpp, ncp, flags) 985 struct denode *dep; 986 u_long count; 987 struct buf **bpp; 988 u_long *ncp; 989 int flags; 990 { 991 int error; 992 u_long frcn; 993 u_long cn, got; 994 struct msdosfsmount *pmp = dep->de_pmp; 995 struct buf *bp; 996 997 /* 998 * Don't try to extend the root directory 999 */ 1000 if (dep->de_StartCluster == MSDOSFSROOT 1001 && (dep->de_Attributes & ATTR_DIRECTORY)) { 1002 printf("extendfile(): attempt to extend root directory\n"); 1003 return (ENOSPC); 1004 } 1005 1006 /* 1007 * If the "file's last cluster" cache entry is empty, and the file 1008 * is not empty, then fill the cache entry by calling pcbmap(). 1009 */ 1010 fc_fileextends++; 1011 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 1012 dep->de_StartCluster != 0) { 1013 fc_lfcempty++; 1014 error = pcbmap(dep, 0xffff, 0, &cn, 0); 1015 /* we expect it to return E2BIG */ 1016 if (error != E2BIG) 1017 return (error); 1018 } 1019 1020 while (count > 0) { 1021 /* 1022 * Allocate a new cluster chain and cat onto the end of the 1023 * file. * If the file is empty we make de_StartCluster point 1024 * to the new block. Note that de_StartCluster being 0 is 1025 * sufficient to be sure the file is empty since we exclude 1026 * attempts to extend the root directory above, and the root 1027 * dir is the only file with a startcluster of 0 that has 1028 * blocks allocated (sort of). 1029 */ 1030 if (dep->de_StartCluster == 0) 1031 cn = 0; 1032 else 1033 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 1034 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 1035 if (error) 1036 return (error); 1037 1038 count -= got; 1039 1040 /* 1041 * Give them the filesystem relative cluster number if they want 1042 * it. 1043 */ 1044 if (ncp) { 1045 *ncp = cn; 1046 ncp = NULL; 1047 } 1048 1049 if (dep->de_StartCluster == 0) { 1050 dep->de_StartCluster = cn; 1051 frcn = 0; 1052 } else { 1053 error = fatentry(FAT_SET, pmp, 1054 dep->de_fc[FC_LASTFC].fc_fsrcn, 1055 0, cn); 1056 if (error) { 1057 clusterfree(pmp, cn, NULL); 1058 return (error); 1059 } 1060 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1061 } 1062 1063 /* 1064 * Update the "last cluster of the file" entry in the denode's fat 1065 * cache. 1066 */ 1067 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1068 1069 if (flags & DE_CLEAR) { 1070 while (got-- > 0) { 1071 /* 1072 * Get the buf header for the new block of the file. 1073 */ 1074 if (dep->de_Attributes & ATTR_DIRECTORY) 1075 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1076 pmp->pm_bpcluster, 0, 0); 1077 else { 1078 bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++), 1079 pmp->pm_bpcluster, 0, 0); 1080 /* 1081 * Do the bmap now, as in msdosfs_write 1082 */ 1083 if (pcbmap(dep, 1084 de_bn2cn(pmp, bp->b_lblkno), 1085 &bp->b_blkno, 0, 0)) 1086 bp->b_blkno = -1; 1087 if (bp->b_blkno == -1) 1088 panic("extendfile: pcbmap"); 1089 } 1090 clrbuf(bp); 1091 if (bpp) { 1092 *bpp = bp; 1093 bpp = NULL; 1094 } else 1095 bdwrite(bp); 1096 } 1097 } 1098 } 1099 1100 return (0); 1101 }
Cache object: b7692e994e2187979250d8b899bd6c0a
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