1 /* $FreeBSD: src/sys/msdosfs/msdosfs_fat.c,v 1.23 2000/01/27 14:43:06 nyan Exp $ */ 2 /* $DragonFly: src/sys/vfs/msdosfs/msdosfs_fat.c,v 1.11 2006/12/23 00:41:29 swildner Exp $ */ 3 /* $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $ */ 4 5 /*- 6 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. 7 * Copyright (C) 1994, 1995, 1997 TooLs GmbH. 8 * All rights reserved. 9 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by TooLs GmbH. 22 * 4. The name of TooLs GmbH may not be used to endorse or promote products 23 * derived from this software without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR 26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 29 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 30 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 31 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 32 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 33 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 34 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35 */ 36 /* 37 * Written by Paul Popelka (paulp@uts.amdahl.com) 38 * 39 * You can do anything you want with this software, just don't say you wrote 40 * it, and don't remove this notice. 41 * 42 * This software is provided "as is". 43 * 44 * The author supplies this software to be publicly redistributed on the 45 * understanding that the author is not responsible for the correct 46 * functioning of this software in any circumstances and is not liable for 47 * any damages caused by this software. 48 * 49 * October 1992 50 */ 51 52 /* 53 * kernel include files. 54 */ 55 #include <sys/param.h> 56 #include <sys/systm.h> 57 #include <sys/buf.h> 58 #include <sys/mount.h> /* to define statfs structure */ 59 #include <sys/vnode.h> /* to define vattr structure */ 60 61 /* 62 * msdosfs include files. 63 */ 64 #include "bpb.h" 65 #include "msdosfsmount.h" 66 #include "direntry.h" 67 #include "denode.h" 68 #include "fat.h" 69 70 /* 71 * Fat cache stats. 72 */ 73 static int fc_fileextends; /* # of file extends */ 74 static int fc_lfcempty; /* # of time last file cluster cache entry 75 * was empty */ 76 static int fc_bmapcalls; /* # of times pcbmap was called */ 77 78 #define LMMAX 20 79 static int fc_lmdistance[LMMAX];/* counters for how far off the last 80 * cluster mapped entry was. */ 81 static int fc_largedistance; /* off by more than LMMAX */ 82 83 static int chainalloc (struct msdosfsmount *pmp, u_long start, 84 u_long count, u_long fillwith, 85 u_long *retcluster, u_long *got); 86 static int chainlength (struct msdosfsmount *pmp, u_long start, 87 u_long count); 88 static void fatblock (struct msdosfsmount *pmp, u_long ofs, 89 u_long *bnp, u_long *sizep, u_long *bop); 90 static int fatchain (struct msdosfsmount *pmp, u_long start, 91 u_long count, u_long fillwith); 92 static void fc_lookup (struct denode *dep, u_long findcn, 93 u_long *frcnp, u_long *fsrcnp); 94 static void updatefats (struct msdosfsmount *pmp, struct buf *bp, 95 u_long fatbn); 96 static __inline void 97 usemap_alloc (struct msdosfsmount *pmp, u_long cn); 98 static __inline void 99 usemap_free (struct msdosfsmount *pmp, u_long cn); 100 101 static void 102 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, 103 u_long *bop) 104 { 105 u_long bn, size; 106 107 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 108 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 109 * DEV_BSIZE; 110 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 111 112 if (bnp) 113 *bnp = bn; 114 if (sizep) 115 *sizep = size; 116 if (bop) 117 *bop = ofs % pmp->pm_fatblocksize; 118 } 119 120 /* 121 * Map the logical cluster number of a file into a physical disk sector 122 * that is filesystem relative. 123 * 124 * dep - address of denode representing the file of interest 125 * findcn - file relative cluster whose filesystem relative cluster number 126 * and/or block number are/is to be found 127 * bnp - address of where to place the file system relative block number. 128 * If this pointer is null then don't return this quantity. 129 * cnp - address of where to place the file system relative cluster number. 130 * If this pointer is null then don't return this quantity. 131 * 132 * NOTE: Either bnp or cnp must be non-null. 133 * This function has one side effect. If the requested file relative cluster 134 * is beyond the end of file, then the actual number of clusters in the file 135 * is returned in *cnp. This is useful for determining how long a directory is. 136 * If cnp is null, nothing is returned. 137 */ 138 int 139 pcbmap(struct denode *dep, 140 u_long findcn, /* file relative cluster to get */ 141 daddr_t *bnp, /* returned filesys relative blk number */ 142 u_long *cnp, /* returned cluster number */ 143 int *sp) /* returned block size */ 144 { 145 int error; 146 u_long i; 147 u_long cn; 148 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 149 u_long byteoffset; 150 u_long bn; 151 u_long bo; 152 struct buf *bp = NULL; 153 u_long bp_bn = -1; 154 struct msdosfsmount *pmp = dep->de_pmp; 155 u_long bsize; 156 157 fc_bmapcalls++; 158 159 /* 160 * If they don't give us someplace to return a value then don't 161 * bother doing anything. 162 */ 163 if (bnp == NULL && cnp == NULL && sp == NULL) 164 return (0); 165 166 cn = dep->de_StartCluster; 167 /* 168 * The "file" that makes up the root directory is contiguous, 169 * permanently allocated, of fixed size, and is not made up of 170 * clusters. If the cluster number is beyond the end of the root 171 * directory, then return the number of clusters in the file. 172 */ 173 if (cn == MSDOSFSROOT) { 174 if (dep->de_Attributes & ATTR_DIRECTORY) { 175 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 176 if (cnp) 177 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 178 return (E2BIG); 179 } 180 if (bnp) 181 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 182 if (cnp) 183 *cnp = MSDOSFSROOT; 184 if (sp) 185 *sp = min(pmp->pm_bpcluster, 186 dep->de_FileSize - de_cn2off(pmp, findcn)); 187 return (0); 188 } else { /* just an empty file */ 189 if (cnp) 190 *cnp = 0; 191 return (E2BIG); 192 } 193 } 194 195 /* 196 * All other files do I/O in cluster sized blocks 197 */ 198 if (sp) 199 *sp = pmp->pm_bpcluster; 200 201 /* 202 * Rummage around in the fat cache, maybe we can avoid tromping 203 * thru every fat entry for the file. And, keep track of how far 204 * off the cache was from where we wanted to be. 205 */ 206 i = 0; 207 fc_lookup(dep, findcn, &i, &cn); 208 if ((bn = findcn - i) >= LMMAX) 209 fc_largedistance++; 210 else 211 fc_lmdistance[bn]++; 212 213 /* 214 * Handle all other files or directories the normal way. 215 */ 216 for (; i < findcn; i++) { 217 /* 218 * Stop with all reserved clusters, not just with EOF. 219 */ 220 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 221 goto hiteof; 222 byteoffset = FATOFS(pmp, cn); 223 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 224 if (bn != bp_bn) { 225 if (bp) 226 brelse(bp); 227 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 228 if (error) { 229 brelse(bp); 230 return (error); 231 } 232 bp_bn = bn; 233 } 234 prevcn = cn; 235 if (FAT32(pmp)) 236 cn = getulong(&bp->b_data[bo]); 237 else 238 cn = getushort(&bp->b_data[bo]); 239 if (FAT12(pmp) && (prevcn & 1)) 240 cn >>= 4; 241 cn &= pmp->pm_fatmask; 242 243 /* 244 * Force the special cluster numbers 245 * to be the same for all cluster sizes 246 * to let the rest of msdosfs handle 247 * all cases the same. 248 */ 249 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 250 cn |= ~pmp->pm_fatmask; 251 } 252 253 if (!MSDOSFSEOF(pmp, cn)) { 254 if (bp) 255 brelse(bp); 256 if (bnp) 257 *bnp = xcntobn(pmp, cn); 258 if (cnp) 259 *cnp = cn; 260 fc_setcache(dep, FC_LASTMAP, i, cn); 261 return (0); 262 } 263 264 hiteof:; 265 if (cnp) 266 *cnp = i; 267 if (bp) 268 brelse(bp); 269 /* update last file cluster entry in the fat cache */ 270 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 271 return (E2BIG); 272 } 273 274 /* 275 * Find the closest entry in the fat cache to the cluster we are looking 276 * for. 277 */ 278 static void 279 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp) 280 { 281 int i; 282 u_long cn; 283 struct fatcache *closest = 0; 284 285 for (i = 0; i < FC_SIZE; i++) { 286 cn = dep->de_fc[i].fc_frcn; 287 if (cn != FCE_EMPTY && cn <= findcn) { 288 if (closest == 0 || cn > closest->fc_frcn) 289 closest = &dep->de_fc[i]; 290 } 291 } 292 if (closest) { 293 *frcnp = closest->fc_frcn; 294 *fsrcnp = closest->fc_fsrcn; 295 } 296 } 297 298 /* 299 * Purge the fat cache in denode dep of all entries relating to file 300 * relative cluster frcn and beyond. 301 */ 302 void 303 fc_purge(struct denode *dep, u_int frcn) 304 { 305 int i; 306 struct fatcache *fcp; 307 308 fcp = dep->de_fc; 309 for (i = 0; i < FC_SIZE; i++, fcp++) { 310 if (fcp->fc_frcn >= frcn) 311 fcp->fc_frcn = FCE_EMPTY; 312 } 313 } 314 315 /* 316 * Update the fat. 317 * If mirroring the fat, update all copies, with the first copy as last. 318 * Else update only the current fat (ignoring the others). 319 * 320 * pmp - msdosfsmount structure for filesystem to update 321 * bp - addr of modified fat block 322 * fatbn - block number relative to begin of filesystem of the modified fat block. 323 */ 324 static void 325 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 326 { 327 int i; 328 struct buf *bpn; 329 330 #ifdef MSDOSFS_DEBUG 331 kprintf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn); 332 #endif 333 334 /* 335 * If we have an FSInfo block, update it. 336 */ 337 if (pmp->pm_fsinfo) { 338 u_long cn = pmp->pm_nxtfree; 339 340 if (pmp->pm_freeclustercount 341 && (pmp->pm_inusemap[cn / N_INUSEBITS] 342 & (1 << (cn % N_INUSEBITS)))) { 343 /* 344 * The cluster indicated in FSInfo isn't free 345 * any longer. Got get a new free one. 346 */ 347 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS) 348 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 349 break; 350 pmp->pm_nxtfree = cn 351 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 352 ^ (u_int)-1) - 1; 353 } 354 if (bread(pmp->pm_devvp, de_bntodoff(pmp, pmp->pm_fsinfo), fsi_size(pmp), &bpn) != 0) { 355 /* 356 * Ignore the error, but turn off FSInfo update for the future. 357 */ 358 pmp->pm_fsinfo = 0; 359 brelse(bpn); 360 } else { 361 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 362 363 putulong(fp->fsinfree, pmp->pm_freeclustercount); 364 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 365 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 366 bwrite(bpn); 367 else 368 bdwrite(bpn); 369 } 370 } 371 372 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 373 /* 374 * Now copy the block(s) of the modified fat to the other copies of 375 * the fat and write them out. This is faster than reading in the 376 * other fats and then writing them back out. This could tie up 377 * the fat for quite a while. Preventing others from accessing it. 378 * To prevent us from going after the fat quite so much we use 379 * delayed writes, unless they specfied "synchronous" when the 380 * filesystem was mounted. If synch is asked for then use 381 * bwrite()'s and really slow things down. 382 */ 383 for (i = 1; i < pmp->pm_FATs; i++) { 384 fatbn += pmp->pm_FATsecs; 385 /* getblk() never fails */ 386 bpn = getblk(pmp->pm_devvp, de_bntodoff(pmp, fatbn), 387 bp->b_bcount, 0, 0); 388 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 389 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 390 bwrite(bpn); 391 else 392 bdwrite(bpn); 393 } 394 } 395 396 /* 397 * Write out the first (or current) fat last. 398 */ 399 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 400 bwrite(bp); 401 else 402 bdwrite(bp); 403 /* 404 * Maybe update fsinfo sector here? 405 */ 406 } 407 408 /* 409 * Updating entries in 12 bit fats is a pain in the butt. 410 * 411 * The following picture shows where nibbles go when moving from a 12 bit 412 * cluster number into the appropriate bytes in the FAT. 413 * 414 * byte m byte m+1 byte m+2 415 * +----+----+ +----+----+ +----+----+ 416 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 417 * +----+----+ +----+----+ +----+----+ 418 * 419 * +----+----+----+ +----+----+----+ 420 * | 3 0 1 | | 4 5 2 | 421 * +----+----+----+ +----+----+----+ 422 * cluster n cluster n+1 423 * 424 * Where n is even. m = n + (n >> 2) 425 * 426 */ 427 static __inline void 428 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 429 { 430 431 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 432 pmp->pm_freeclustercount--; 433 } 434 435 static __inline void 436 usemap_free(struct msdosfsmount *pmp, u_long cn) 437 { 438 439 pmp->pm_freeclustercount++; 440 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 441 } 442 443 int 444 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 445 { 446 int error; 447 u_long oldcn; 448 449 usemap_free(pmp, cluster); 450 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 451 if (error) { 452 usemap_alloc(pmp, cluster); 453 return (error); 454 } 455 /* 456 * If the cluster was successfully marked free, then update 457 * the count of free clusters, and turn off the "allocated" 458 * bit in the "in use" cluster bit map. 459 */ 460 if (oldcnp) 461 *oldcnp = oldcn; 462 return (0); 463 } 464 465 /* 466 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 467 * 468 * function - whether to get or set a fat entry 469 * pmp - address of the msdosfsmount structure for the filesystem 470 * whose fat is to be manipulated. 471 * cn - which cluster is of interest 472 * oldcontents - address of a word that is to receive the contents of the 473 * cluster'th entry if this is a get function 474 * newcontents - the new value to be written into the cluster'th element of 475 * the fat if this is a set function. 476 * 477 * This function can also be used to free a cluster by setting the fat entry 478 * for a cluster to 0. 479 * 480 * All copies of the fat are updated if this is a set function. NOTE: If 481 * fatentry() marks a cluster as free it does not update the inusemap in 482 * the msdosfsmount structure. This is left to the caller. 483 */ 484 int 485 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, 486 u_long newcontents) 487 { 488 int error; 489 u_long readcn; 490 u_long bn, bo, bsize, byteoffset; 491 struct buf *bp; 492 493 #ifdef MSDOSFS_DEBUG 494 kprintf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 495 function, pmp, cn, oldcontents, newcontents); 496 #endif 497 498 #ifdef DIAGNOSTIC 499 /* 500 * Be sure they asked us to do something. 501 */ 502 if ((function & (FAT_SET | FAT_GET)) == 0) { 503 kprintf("fatentry(): function code doesn't specify get or set\n"); 504 return (EINVAL); 505 } 506 507 /* 508 * If they asked us to return a cluster number but didn't tell us 509 * where to put it, give them an error. 510 */ 511 if ((function & FAT_GET) && oldcontents == NULL) { 512 kprintf("fatentry(): get function with no place to put result\n"); 513 return (EINVAL); 514 } 515 #endif 516 517 /* 518 * Be sure the requested cluster is in the filesystem. 519 */ 520 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 521 return (EINVAL); 522 523 byteoffset = FATOFS(pmp, cn); 524 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 525 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 526 if (error) { 527 brelse(bp); 528 return (error); 529 } 530 531 if (function & FAT_GET) { 532 if (FAT32(pmp)) 533 readcn = getulong(&bp->b_data[bo]); 534 else 535 readcn = getushort(&bp->b_data[bo]); 536 if (FAT12(pmp) & (cn & 1)) 537 readcn >>= 4; 538 readcn &= pmp->pm_fatmask; 539 /* map reserved fat entries to same values for all fats */ 540 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 541 readcn |= ~pmp->pm_fatmask; 542 *oldcontents = readcn; 543 } 544 if (function & FAT_SET) { 545 switch (pmp->pm_fatmask) { 546 case FAT12_MASK: 547 readcn = getushort(&bp->b_data[bo]); 548 if (cn & 1) { 549 readcn &= 0x000f; 550 readcn |= newcontents << 4; 551 } else { 552 readcn &= 0xf000; 553 readcn |= newcontents & 0xfff; 554 } 555 putushort(&bp->b_data[bo], readcn); 556 break; 557 case FAT16_MASK: 558 putushort(&bp->b_data[bo], newcontents); 559 break; 560 case FAT32_MASK: 561 /* 562 * According to spec we have to retain the 563 * high order bits of the fat entry. 564 */ 565 readcn = getulong(&bp->b_data[bo]); 566 readcn &= ~FAT32_MASK; 567 readcn |= newcontents & FAT32_MASK; 568 putulong(&bp->b_data[bo], readcn); 569 break; 570 } 571 updatefats(pmp, bp, bn); 572 bp = NULL; 573 pmp->pm_fmod = 1; 574 } 575 if (bp) 576 brelse(bp); 577 return (0); 578 } 579 580 /* 581 * Update a contiguous cluster chain 582 * 583 * pmp - mount point 584 * start - first cluster of chain 585 * count - number of clusters in chain 586 * fillwith - what to write into fat entry of last cluster 587 */ 588 static int 589 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 590 { 591 int error; 592 u_long bn, bo, bsize, byteoffset, readcn, newc; 593 struct buf *bp; 594 595 #ifdef MSDOSFS_DEBUG 596 kprintf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 597 pmp, start, count, fillwith); 598 #endif 599 /* 600 * Be sure the clusters are in the filesystem. 601 */ 602 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 603 return (EINVAL); 604 605 while (count > 0) { 606 byteoffset = FATOFS(pmp, start); 607 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 608 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 609 if (error) { 610 brelse(bp); 611 return (error); 612 } 613 while (count > 0) { 614 start++; 615 newc = --count > 0 ? start : fillwith; 616 switch (pmp->pm_fatmask) { 617 case FAT12_MASK: 618 readcn = getushort(&bp->b_data[bo]); 619 if (start & 1) { 620 readcn &= 0xf000; 621 readcn |= newc & 0xfff; 622 } else { 623 readcn &= 0x000f; 624 readcn |= newc << 4; 625 } 626 putushort(&bp->b_data[bo], readcn); 627 bo++; 628 if (!(start & 1)) 629 bo++; 630 break; 631 case FAT16_MASK: 632 putushort(&bp->b_data[bo], newc); 633 bo += 2; 634 break; 635 case FAT32_MASK: 636 readcn = getulong(&bp->b_data[bo]); 637 readcn &= ~pmp->pm_fatmask; 638 readcn |= newc & pmp->pm_fatmask; 639 putulong(&bp->b_data[bo], readcn); 640 bo += 4; 641 break; 642 } 643 if (bo >= bsize) 644 break; 645 } 646 updatefats(pmp, bp, bn); 647 } 648 pmp->pm_fmod = 1; 649 return (0); 650 } 651 652 /* 653 * Check the length of a free cluster chain starting at start. 654 * 655 * pmp - mount point 656 * start - start of chain 657 * count - maximum interesting length 658 */ 659 static int 660 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 661 { 662 u_long idx, max_idx; 663 u_int map; 664 u_long len; 665 666 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 667 idx = start / N_INUSEBITS; 668 start %= N_INUSEBITS; 669 map = pmp->pm_inusemap[idx]; 670 map &= ~((1 << start) - 1); 671 if (map) { 672 len = ffs(map) - 1 - start; 673 return (len > count ? count : len); 674 } 675 len = N_INUSEBITS - start; 676 if (len >= count) 677 return (count); 678 while (++idx <= max_idx) { 679 if (len >= count) 680 break; 681 map = pmp->pm_inusemap[idx]; 682 if (map) { 683 len += ffs(map) - 1; 684 break; 685 } 686 len += N_INUSEBITS; 687 } 688 return (len > count ? count : len); 689 } 690 691 /* 692 * Allocate contigous free clusters. 693 * 694 * pmp - mount point. 695 * start - start of cluster chain. 696 * count - number of clusters to allocate. 697 * fillwith - put this value into the fat entry for the 698 * last allocated cluster. 699 * retcluster - put the first allocated cluster's number here. 700 * got - how many clusters were actually allocated. 701 */ 702 static int 703 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, 704 u_long fillwith, u_long *retcluster, u_long *got) 705 { 706 int error; 707 u_long cl, n; 708 709 for (cl = start, n = count; n-- > 0;) 710 usemap_alloc(pmp, cl++); 711 712 error = fatchain(pmp, start, count, fillwith); 713 if (error != 0) 714 return (error); 715 #ifdef MSDOSFS_DEBUG 716 kprintf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 717 start, count); 718 #endif 719 if (retcluster) 720 *retcluster = start; 721 if (got) 722 *got = count; 723 return (0); 724 } 725 726 /* 727 * Allocate contiguous free clusters. 728 * 729 * pmp - mount point. 730 * start - preferred start of cluster chain. 731 * count - number of clusters requested. 732 * fillwith - put this value into the fat entry for the 733 * last allocated cluster. 734 * retcluster - put the first allocated cluster's number here. 735 * got - how many clusters were actually allocated. 736 */ 737 int 738 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, 739 u_long fillwith, u_long *retcluster, u_long *got) 740 { 741 u_long idx; 742 u_long len, newst, foundl, cn, l; 743 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 744 u_int map; 745 746 #ifdef MSDOSFS_DEBUG 747 kprintf("clusteralloc(): find %lu clusters\n",count); 748 #endif 749 if (start) { 750 if ((len = chainlength(pmp, start, count)) >= count) 751 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 752 } else 753 len = 0; 754 755 /* 756 * Start at a (pseudo) random place to maximize cluster runs 757 * under multiple writers. 758 */ 759 newst = krandom() % (pmp->pm_maxcluster + 1); 760 foundl = 0; 761 762 for (cn = newst; cn <= pmp->pm_maxcluster;) { 763 idx = cn / N_INUSEBITS; 764 map = pmp->pm_inusemap[idx]; 765 map |= (1 << (cn % N_INUSEBITS)) - 1; 766 if (map != (u_int)-1) { 767 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 768 if ((l = chainlength(pmp, cn, count)) >= count) 769 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 770 if (l > foundl) { 771 foundcn = cn; 772 foundl = l; 773 } 774 cn += l + 1; 775 continue; 776 } 777 cn += N_INUSEBITS - cn % N_INUSEBITS; 778 } 779 for (cn = 0; cn < newst;) { 780 idx = cn / N_INUSEBITS; 781 map = pmp->pm_inusemap[idx]; 782 map |= (1 << (cn % N_INUSEBITS)) - 1; 783 if (map != (u_int)-1) { 784 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 785 if ((l = chainlength(pmp, cn, count)) >= count) 786 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 787 if (l > foundl) { 788 foundcn = cn; 789 foundl = l; 790 } 791 cn += l + 1; 792 continue; 793 } 794 cn += N_INUSEBITS - cn % N_INUSEBITS; 795 } 796 797 if (!foundl) 798 return (ENOSPC); 799 800 if (len) 801 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 802 else 803 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 804 } 805 806 807 /* 808 * Free a chain of clusters. 809 * 810 * pmp - address of the msdosfs mount structure for the filesystem 811 * containing the cluster chain to be freed. 812 * startcluster - number of the 1st cluster in the chain of clusters to be 813 * freed. 814 */ 815 int 816 freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 817 { 818 int error; 819 struct buf *bp = NULL; 820 u_long bn, bo, bsize, byteoffset; 821 u_long readcn, lbn = -1; 822 823 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 824 byteoffset = FATOFS(pmp, cluster); 825 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 826 if (lbn != bn) { 827 if (bp) 828 updatefats(pmp, bp, lbn); 829 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 830 if (error) { 831 brelse(bp); 832 return (error); 833 } 834 lbn = bn; 835 } 836 usemap_free(pmp, cluster); 837 switch (pmp->pm_fatmask) { 838 case FAT12_MASK: 839 readcn = getushort(&bp->b_data[bo]); 840 if (cluster & 1) { 841 cluster = readcn >> 4; 842 readcn &= 0x000f; 843 readcn |= MSDOSFSFREE << 4; 844 } else { 845 cluster = readcn; 846 readcn &= 0xf000; 847 readcn |= MSDOSFSFREE & 0xfff; 848 } 849 putushort(&bp->b_data[bo], readcn); 850 break; 851 case FAT16_MASK: 852 cluster = getushort(&bp->b_data[bo]); 853 putushort(&bp->b_data[bo], MSDOSFSFREE); 854 break; 855 case FAT32_MASK: 856 cluster = getulong(&bp->b_data[bo]); 857 putulong(&bp->b_data[bo], 858 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 859 break; 860 } 861 cluster &= pmp->pm_fatmask; 862 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 863 cluster |= pmp->pm_fatmask; 864 } 865 if (bp) 866 updatefats(pmp, bp, bn); 867 return (0); 868 } 869 870 /* 871 * Read in fat blocks looking for free clusters. For every free cluster 872 * found turn off its corresponding bit in the pm_inusemap. 873 */ 874 int 875 fillinusemap(struct msdosfsmount *pmp) 876 { 877 struct buf *bp = NULL; 878 u_long cn, readcn; 879 int error; 880 u_long bn, bo, bsize, byteoffset; 881 882 /* 883 * Mark all clusters in use, we mark the free ones in the fat scan 884 * loop further down. 885 */ 886 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 887 pmp->pm_inusemap[cn] = (u_int)-1; 888 889 /* 890 * Figure how many free clusters are in the filesystem by ripping 891 * through the fat counting the number of entries whose content is 892 * zero. These represent free clusters. 893 */ 894 pmp->pm_freeclustercount = 0; 895 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 896 byteoffset = FATOFS(pmp, cn); 897 bo = byteoffset % pmp->pm_fatblocksize; 898 if (!bo || !bp) { 899 /* Read new FAT block */ 900 if (bp) 901 brelse(bp); 902 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 903 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 904 if (error) { 905 brelse(bp); 906 return (error); 907 } 908 } 909 if (FAT32(pmp)) 910 readcn = getulong(&bp->b_data[bo]); 911 else 912 readcn = getushort(&bp->b_data[bo]); 913 if (FAT12(pmp) && (cn & 1)) 914 readcn >>= 4; 915 readcn &= pmp->pm_fatmask; 916 917 if (readcn == 0) 918 usemap_free(pmp, cn); 919 } 920 brelse(bp); 921 return (0); 922 } 923 924 /* 925 * Allocate a new cluster and chain it onto the end of the file. 926 * 927 * dep - the file to extend 928 * count - number of clusters to allocate 929 * bpp - where to return the address of the buf header for the first new 930 * file block 931 * ncp - where to put cluster number of the first newly allocated cluster 932 * If this pointer is 0, do not return the cluster number. 933 * flags - see fat.h 934 * 935 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 936 * the de_flag field of the denode and it does not change the de_FileSize 937 * field. This is left for the caller to do. 938 */ 939 int 940 extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, 941 int flags) 942 { 943 int error; 944 u_long frcn; 945 u_long cn, got; 946 struct msdosfsmount *pmp = dep->de_pmp; 947 struct buf *bp; 948 949 /* 950 * Don't try to extend the root directory 951 */ 952 if (dep->de_StartCluster == MSDOSFSROOT 953 && (dep->de_Attributes & ATTR_DIRECTORY)) { 954 kprintf("extendfile(): attempt to extend root directory\n"); 955 return (ENOSPC); 956 } 957 958 /* 959 * If the "file's last cluster" cache entry is empty, and the file 960 * is not empty, then fill the cache entry by calling pcbmap(). 961 */ 962 fc_fileextends++; 963 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 964 dep->de_StartCluster != 0) { 965 fc_lfcempty++; 966 error = pcbmap(dep, 0xffff, NULL, &cn, NULL); 967 /* we expect it to return E2BIG */ 968 if (error != E2BIG) 969 return (error); 970 } 971 972 while (count > 0) { 973 /* 974 * Allocate a new cluster chain and cat onto the end of the 975 * file. * If the file is empty we make de_StartCluster point 976 * to the new block. Note that de_StartCluster being 0 is 977 * sufficient to be sure the file is empty since we exclude 978 * attempts to extend the root directory above, and the root 979 * dir is the only file with a startcluster of 0 that has 980 * blocks allocated (sort of). 981 */ 982 if (dep->de_StartCluster == 0) 983 cn = 0; 984 else 985 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 986 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 987 if (error) 988 return (error); 989 990 count -= got; 991 992 /* 993 * Give them the filesystem relative cluster number if they want 994 * it. 995 */ 996 if (ncp) { 997 *ncp = cn; 998 ncp = NULL; 999 } 1000 1001 if (dep->de_StartCluster == 0) { 1002 dep->de_StartCluster = cn; 1003 frcn = 0; 1004 } else { 1005 error = fatentry(FAT_SET, pmp, 1006 dep->de_fc[FC_LASTFC].fc_fsrcn, 1007 0, cn); 1008 if (error) { 1009 clusterfree(pmp, cn, NULL); 1010 return (error); 1011 } 1012 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1013 } 1014 1015 /* 1016 * Update the "last cluster of the file" entry in the 1017 * denode's fat cache. 1018 */ 1019 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1020 1021 if (flags & DE_CLEAR) { 1022 while (got-- > 0) { 1023 /* 1024 * Get the buf header for the new block of the file. 1025 */ 1026 if (dep->de_Attributes & ATTR_DIRECTORY) { 1027 bp = getblk(pmp->pm_devvp, 1028 xcntodoff(pmp, cn), 1029 pmp->pm_bpcluster, 0, 0); 1030 ++cn; 1031 } else { 1032 daddr_t dblkno; 1033 1034 bp = getblk(DETOV(dep), 1035 de_cn2doff(pmp, frcn), 1036 pmp->pm_bpcluster, 0, 0); 1037 ++frcn; 1038 /* 1039 * Do the bmap now, as in msdosfs_write 1040 */ 1041 if (pcbmap(dep, 1042 de_bn2cn(pmp, de_off2bn(pmp, bp->b_bio1.bio_offset)), 1043 &dblkno, NULL, NULL)) { 1044 bp->b_bio2.bio_offset = NOOFFSET; 1045 } else { 1046 bp->b_bio2.bio_offset = de_bntodoff(pmp, dblkno); 1047 } 1048 if (bp->b_bio2.bio_offset == NOOFFSET) 1049 panic("extendfile: pcbmap"); 1050 } 1051 clrbuf(bp); 1052 if (bpp) { 1053 *bpp = bp; 1054 bpp = NULL; 1055 } else 1056 bdwrite(bp); 1057 } 1058 } 1059 } 1060 1061 return (0); 1062 } 1063