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 #include <sys/buf2.h> 62 63 /* 64 * msdosfs include files. 65 */ 66 #include "bpb.h" 67 #include "msdosfsmount.h" 68 #include "direntry.h" 69 #include "denode.h" 70 #include "fat.h" 71 72 /* 73 * Fat cache stats. 74 */ 75 static int fc_fileextends; /* # of file extends */ 76 static int fc_lfcempty; /* # of time last file cluster cache entry 77 * was empty */ 78 static int fc_bmapcalls; /* # of times pcbmap was called */ 79 80 #define LMMAX 20 81 static int fc_lmdistance[LMMAX];/* counters for how far off the last 82 * cluster mapped entry was. */ 83 static int fc_largedistance; /* off by more than LMMAX */ 84 85 static int chainalloc (struct msdosfsmount *pmp, u_long start, 86 u_long count, u_long fillwith, 87 u_long *retcluster, u_long *got); 88 static int chainlength (struct msdosfsmount *pmp, u_long start, 89 u_long count); 90 static void fatblock (struct msdosfsmount *pmp, u_long ofs, 91 u_long *bnp, u_long *sizep, u_long *bop); 92 static int fatchain (struct msdosfsmount *pmp, u_long start, 93 u_long count, u_long fillwith); 94 static void fc_lookup (struct denode *dep, u_long findcn, 95 u_long *frcnp, u_long *fsrcnp); 96 static void updatefats (struct msdosfsmount *pmp, struct buf *bp, 97 u_long fatbn); 98 static __inline void 99 usemap_alloc (struct msdosfsmount *pmp, u_long cn); 100 static __inline void 101 usemap_free (struct msdosfsmount *pmp, u_long cn); 102 103 static void 104 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, 105 u_long *bop) 106 { 107 u_long bn, size; 108 109 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 110 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 111 * DEV_BSIZE; 112 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 113 114 if (bnp) 115 *bnp = bn; 116 if (sizep) 117 *sizep = size; 118 if (bop) 119 *bop = ofs % pmp->pm_fatblocksize; 120 } 121 122 /* 123 * Map the logical cluster number of a file into a physical disk sector 124 * that is filesystem relative. 125 * 126 * dep - address of denode representing the file of interest 127 * findcn - file relative cluster whose filesystem relative cluster number 128 * and/or block number are/is to be found 129 * bnp - address of where to place the file system relative block number. 130 * If this pointer is null then don't return this quantity. 131 * cnp - address of where to place the file system relative cluster number. 132 * If this pointer is null then don't return this quantity. 133 * 134 * NOTE: Either bnp or cnp must be non-null. 135 * This function has one side effect. If the requested file relative cluster 136 * is beyond the end of file, then the actual number of clusters in the file 137 * is returned in *cnp. This is useful for determining how long a directory is. 138 * If cnp is null, nothing is returned. 139 */ 140 int 141 pcbmap(struct denode *dep, 142 u_long findcn, /* file relative cluster to get */ 143 daddr_t *bnp, /* returned filesys relative blk number */ 144 u_long *cnp, /* returned cluster number */ 145 int *sp) /* returned block size */ 146 { 147 int error; 148 u_long i; 149 u_long cn; 150 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 151 u_long byteoffset; 152 u_long bn; 153 u_long bo; 154 struct buf *bp = NULL; 155 u_long bp_bn = -1; 156 struct msdosfsmount *pmp = dep->de_pmp; 157 u_long bsize; 158 159 fc_bmapcalls++; 160 161 /* 162 * If they don't give us someplace to return a value then don't 163 * bother doing anything. 164 */ 165 if (bnp == NULL && cnp == NULL && sp == NULL) 166 return (0); 167 168 cn = dep->de_StartCluster; 169 /* 170 * The "file" that makes up the root directory is contiguous, 171 * permanently allocated, of fixed size, and is not made up of 172 * clusters. If the cluster number is beyond the end of the root 173 * directory, then return the number of clusters in the file. 174 */ 175 if (cn == MSDOSFSROOT) { 176 if (dep->de_Attributes & ATTR_DIRECTORY) { 177 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 178 if (cnp) 179 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 180 return (E2BIG); 181 } 182 if (bnp) 183 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 184 if (cnp) 185 *cnp = MSDOSFSROOT; 186 if (sp) 187 *sp = min(pmp->pm_bpcluster, 188 dep->de_FileSize - de_cn2off(pmp, findcn)); 189 return (0); 190 } else { /* just an empty file */ 191 if (cnp) 192 *cnp = 0; 193 return (E2BIG); 194 } 195 } 196 197 /* 198 * All other files do I/O in cluster sized blocks 199 */ 200 if (sp) 201 *sp = pmp->pm_bpcluster; 202 203 /* 204 * Rummage around in the fat cache, maybe we can avoid tromping 205 * thru every fat entry for the file. And, keep track of how far 206 * off the cache was from where we wanted to be. 207 */ 208 i = 0; 209 fc_lookup(dep, findcn, &i, &cn); 210 if ((bn = findcn - i) >= LMMAX) 211 fc_largedistance++; 212 else 213 fc_lmdistance[bn]++; 214 215 /* 216 * Handle all other files or directories the normal way. 217 */ 218 for (; i < findcn; i++) { 219 /* 220 * Stop with all reserved clusters, not just with EOF. 221 */ 222 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 223 goto hiteof; 224 byteoffset = FATOFS(pmp, cn); 225 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 226 if (bn != bp_bn) { 227 if (bp) 228 brelse(bp); 229 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 230 if (error) { 231 brelse(bp); 232 return (error); 233 } 234 bp_bn = bn; 235 } 236 prevcn = cn; 237 if (FAT32(pmp)) 238 cn = getulong(&bp->b_data[bo]); 239 else 240 cn = getushort(&bp->b_data[bo]); 241 if (FAT12(pmp) && (prevcn & 1)) 242 cn >>= 4; 243 cn &= pmp->pm_fatmask; 244 245 /* 246 * Force the special cluster numbers 247 * to be the same for all cluster sizes 248 * to let the rest of msdosfs handle 249 * all cases the same. 250 */ 251 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 252 cn |= ~pmp->pm_fatmask; 253 } 254 255 if (!MSDOSFSEOF(pmp, cn)) { 256 if (bp) 257 brelse(bp); 258 if (bnp) 259 *bnp = xcntobn(pmp, cn); 260 if (cnp) 261 *cnp = cn; 262 fc_setcache(dep, FC_LASTMAP, i, cn); 263 return (0); 264 } 265 266 hiteof:; 267 if (cnp) 268 *cnp = i; 269 if (bp) 270 brelse(bp); 271 /* update last file cluster entry in the fat cache */ 272 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 273 return (E2BIG); 274 } 275 276 /* 277 * Find the closest entry in the fat cache to the cluster we are looking 278 * for. 279 */ 280 static void 281 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp) 282 { 283 int i; 284 u_long cn; 285 struct fatcache *closest = 0; 286 287 for (i = 0; i < FC_SIZE; i++) { 288 cn = dep->de_fc[i].fc_frcn; 289 if (cn != FCE_EMPTY && cn <= findcn) { 290 if (closest == 0 || cn > closest->fc_frcn) 291 closest = &dep->de_fc[i]; 292 } 293 } 294 if (closest) { 295 *frcnp = closest->fc_frcn; 296 *fsrcnp = closest->fc_fsrcn; 297 } 298 } 299 300 /* 301 * Purge the fat cache in denode dep of all entries relating to file 302 * relative cluster frcn and beyond. 303 */ 304 void 305 fc_purge(struct denode *dep, u_int frcn) 306 { 307 int i; 308 struct fatcache *fcp; 309 310 fcp = dep->de_fc; 311 for (i = 0; i < FC_SIZE; i++, fcp++) { 312 if (fcp->fc_frcn >= frcn) 313 fcp->fc_frcn = FCE_EMPTY; 314 } 315 } 316 317 /* 318 * Update the fat. 319 * If mirroring the fat, update all copies, with the first copy as last. 320 * Else update only the current fat (ignoring the others). 321 * 322 * pmp - msdosfsmount structure for filesystem to update 323 * bp - addr of modified fat block 324 * fatbn - block number relative to begin of filesystem of the modified fat block. 325 */ 326 static void 327 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 328 { 329 int i; 330 struct buf *bpn; 331 332 #ifdef MSDOSFS_DEBUG 333 kprintf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn); 334 #endif 335 336 /* 337 * If we have an FSInfo block, update it. 338 */ 339 if (pmp->pm_fsinfo) { 340 u_long cn = pmp->pm_nxtfree; 341 342 if (pmp->pm_freeclustercount 343 && (pmp->pm_inusemap[cn / N_INUSEBITS] 344 & (1 << (cn % N_INUSEBITS)))) { 345 /* 346 * The cluster indicated in FSInfo isn't free 347 * any longer. Got get a new free one. 348 */ 349 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS) 350 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 351 break; 352 pmp->pm_nxtfree = cn 353 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 354 ^ (u_int)-1) - 1; 355 } 356 if (bread(pmp->pm_devvp, de_bntodoff(pmp, pmp->pm_fsinfo), fsi_size(pmp), &bpn) != 0) { 357 /* 358 * Ignore the error, but turn off FSInfo update for the future. 359 */ 360 pmp->pm_fsinfo = 0; 361 brelse(bpn); 362 } else { 363 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 364 365 putulong(fp->fsinfree, pmp->pm_freeclustercount); 366 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 367 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 368 bwrite(bpn); 369 else 370 bdwrite(bpn); 371 } 372 } 373 374 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 375 /* 376 * Now copy the block(s) of the modified fat to the other copies of 377 * the fat and write them out. This is faster than reading in the 378 * other fats and then writing them back out. This could tie up 379 * the fat for quite a while. Preventing others from accessing it. 380 * To prevent us from going after the fat quite so much we use 381 * delayed writes, unless they specfied "synchronous" when the 382 * filesystem was mounted. If synch is asked for then use 383 * bwrite()'s and really slow things down. 384 */ 385 for (i = 1; i < pmp->pm_FATs; i++) { 386 fatbn += pmp->pm_FATsecs; 387 /* getblk() never fails */ 388 bpn = getblk(pmp->pm_devvp, de_bntodoff(pmp, fatbn), 389 bp->b_bcount, 0, 0); 390 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 391 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 392 bwrite(bpn); 393 else 394 bdwrite(bpn); 395 } 396 } 397 398 /* 399 * Write out the first (or current) fat last. 400 */ 401 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 402 bwrite(bp); 403 else 404 bdwrite(bp); 405 /* 406 * Maybe update fsinfo sector here? 407 */ 408 } 409 410 /* 411 * Updating entries in 12 bit fats is a pain in the butt. 412 * 413 * The following picture shows where nibbles go when moving from a 12 bit 414 * cluster number into the appropriate bytes in the FAT. 415 * 416 * byte m byte m+1 byte m+2 417 * +----+----+ +----+----+ +----+----+ 418 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 419 * +----+----+ +----+----+ +----+----+ 420 * 421 * +----+----+----+ +----+----+----+ 422 * | 3 0 1 | | 4 5 2 | 423 * +----+----+----+ +----+----+----+ 424 * cluster n cluster n+1 425 * 426 * Where n is even. m = n + (n >> 2) 427 * 428 */ 429 static __inline void 430 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 431 { 432 433 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 434 pmp->pm_freeclustercount--; 435 } 436 437 static __inline void 438 usemap_free(struct msdosfsmount *pmp, u_long cn) 439 { 440 441 pmp->pm_freeclustercount++; 442 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 443 } 444 445 int 446 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 447 { 448 int error; 449 u_long oldcn; 450 451 usemap_free(pmp, cluster); 452 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 453 if (error) { 454 usemap_alloc(pmp, cluster); 455 return (error); 456 } 457 /* 458 * If the cluster was successfully marked free, then update 459 * the count of free clusters, and turn off the "allocated" 460 * bit in the "in use" cluster bit map. 461 */ 462 if (oldcnp) 463 *oldcnp = oldcn; 464 return (0); 465 } 466 467 /* 468 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 469 * 470 * function - whether to get or set a fat entry 471 * pmp - address of the msdosfsmount structure for the filesystem 472 * whose fat is to be manipulated. 473 * cn - which cluster is of interest 474 * oldcontents - address of a word that is to receive the contents of the 475 * cluster'th entry if this is a get function 476 * newcontents - the new value to be written into the cluster'th element of 477 * the fat if this is a set function. 478 * 479 * This function can also be used to free a cluster by setting the fat entry 480 * for a cluster to 0. 481 * 482 * All copies of the fat are updated if this is a set function. NOTE: If 483 * fatentry() marks a cluster as free it does not update the inusemap in 484 * the msdosfsmount structure. This is left to the caller. 485 */ 486 int 487 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, 488 u_long newcontents) 489 { 490 int error; 491 u_long readcn; 492 u_long bn, bo, bsize, byteoffset; 493 struct buf *bp; 494 495 #ifdef MSDOSFS_DEBUG 496 kprintf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 497 function, pmp, cn, oldcontents, newcontents); 498 #endif 499 500 #ifdef DIAGNOSTIC 501 /* 502 * Be sure they asked us to do something. 503 */ 504 if ((function & (FAT_SET | FAT_GET)) == 0) { 505 kprintf("fatentry(): function code doesn't specify get or set\n"); 506 return (EINVAL); 507 } 508 509 /* 510 * If they asked us to return a cluster number but didn't tell us 511 * where to put it, give them an error. 512 */ 513 if ((function & FAT_GET) && oldcontents == NULL) { 514 kprintf("fatentry(): get function with no place to put result\n"); 515 return (EINVAL); 516 } 517 #endif 518 519 /* 520 * Be sure the requested cluster is in the filesystem. 521 */ 522 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 523 return (EINVAL); 524 525 byteoffset = FATOFS(pmp, cn); 526 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 527 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 528 if (error) { 529 brelse(bp); 530 return (error); 531 } 532 533 if (function & FAT_GET) { 534 if (FAT32(pmp)) 535 readcn = getulong(&bp->b_data[bo]); 536 else 537 readcn = getushort(&bp->b_data[bo]); 538 if (FAT12(pmp) & (cn & 1)) 539 readcn >>= 4; 540 readcn &= pmp->pm_fatmask; 541 /* map reserved fat entries to same values for all fats */ 542 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 543 readcn |= ~pmp->pm_fatmask; 544 *oldcontents = readcn; 545 } 546 if (function & FAT_SET) { 547 switch (pmp->pm_fatmask) { 548 case FAT12_MASK: 549 readcn = getushort(&bp->b_data[bo]); 550 if (cn & 1) { 551 readcn &= 0x000f; 552 readcn |= newcontents << 4; 553 } else { 554 readcn &= 0xf000; 555 readcn |= newcontents & 0xfff; 556 } 557 putushort(&bp->b_data[bo], readcn); 558 break; 559 case FAT16_MASK: 560 putushort(&bp->b_data[bo], newcontents); 561 break; 562 case FAT32_MASK: 563 /* 564 * According to spec we have to retain the 565 * high order bits of the fat entry. 566 */ 567 readcn = getulong(&bp->b_data[bo]); 568 readcn &= ~FAT32_MASK; 569 readcn |= newcontents & FAT32_MASK; 570 putulong(&bp->b_data[bo], readcn); 571 break; 572 } 573 updatefats(pmp, bp, bn); 574 bp = NULL; 575 pmp->pm_fmod = 1; 576 } 577 if (bp) 578 brelse(bp); 579 return (0); 580 } 581 582 /* 583 * Update a contiguous cluster chain 584 * 585 * pmp - mount point 586 * start - first cluster of chain 587 * count - number of clusters in chain 588 * fillwith - what to write into fat entry of last cluster 589 */ 590 static int 591 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 592 { 593 int error; 594 u_long bn, bo, bsize, byteoffset, readcn, newc; 595 struct buf *bp; 596 597 #ifdef MSDOSFS_DEBUG 598 kprintf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 599 pmp, start, count, fillwith); 600 #endif 601 /* 602 * Be sure the clusters are in the filesystem. 603 */ 604 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 605 return (EINVAL); 606 607 while (count > 0) { 608 byteoffset = FATOFS(pmp, start); 609 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 610 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 611 if (error) { 612 brelse(bp); 613 return (error); 614 } 615 while (count > 0) { 616 start++; 617 newc = --count > 0 ? start : fillwith; 618 switch (pmp->pm_fatmask) { 619 case FAT12_MASK: 620 readcn = getushort(&bp->b_data[bo]); 621 if (start & 1) { 622 readcn &= 0xf000; 623 readcn |= newc & 0xfff; 624 } else { 625 readcn &= 0x000f; 626 readcn |= newc << 4; 627 } 628 putushort(&bp->b_data[bo], readcn); 629 bo++; 630 if (!(start & 1)) 631 bo++; 632 break; 633 case FAT16_MASK: 634 putushort(&bp->b_data[bo], newc); 635 bo += 2; 636 break; 637 case FAT32_MASK: 638 readcn = getulong(&bp->b_data[bo]); 639 readcn &= ~pmp->pm_fatmask; 640 readcn |= newc & pmp->pm_fatmask; 641 putulong(&bp->b_data[bo], readcn); 642 bo += 4; 643 break; 644 } 645 if (bo >= bsize) 646 break; 647 } 648 updatefats(pmp, bp, bn); 649 } 650 pmp->pm_fmod = 1; 651 return (0); 652 } 653 654 /* 655 * Check the length of a free cluster chain starting at start. 656 * 657 * pmp - mount point 658 * start - start of chain 659 * count - maximum interesting length 660 */ 661 static int 662 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 663 { 664 u_long idx, max_idx; 665 u_int map; 666 u_long len; 667 668 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 669 idx = start / N_INUSEBITS; 670 start %= N_INUSEBITS; 671 map = pmp->pm_inusemap[idx]; 672 map &= ~((1 << start) - 1); 673 if (map) { 674 len = ffs(map) - 1 - start; 675 return (len > count ? count : len); 676 } 677 len = N_INUSEBITS - start; 678 if (len >= count) 679 return (count); 680 while (++idx <= max_idx) { 681 if (len >= count) 682 break; 683 map = pmp->pm_inusemap[idx]; 684 if (map) { 685 len += ffs(map) - 1; 686 break; 687 } 688 len += N_INUSEBITS; 689 } 690 return (len > count ? count : len); 691 } 692 693 /* 694 * Allocate contigous free clusters. 695 * 696 * pmp - mount point. 697 * start - start of cluster chain. 698 * count - number of clusters to allocate. 699 * fillwith - put this value into the fat entry for the 700 * last allocated cluster. 701 * retcluster - put the first allocated cluster's number here. 702 * got - how many clusters were actually allocated. 703 */ 704 static int 705 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, 706 u_long fillwith, u_long *retcluster, u_long *got) 707 { 708 int error; 709 u_long cl, n; 710 711 for (cl = start, n = count; n-- > 0;) 712 usemap_alloc(pmp, cl++); 713 714 error = fatchain(pmp, start, count, fillwith); 715 if (error != 0) 716 return (error); 717 #ifdef MSDOSFS_DEBUG 718 kprintf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 719 start, count); 720 #endif 721 if (retcluster) 722 *retcluster = start; 723 if (got) 724 *got = count; 725 return (0); 726 } 727 728 /* 729 * Allocate contiguous free clusters. 730 * 731 * pmp - mount point. 732 * start - preferred start of cluster chain. 733 * count - number of clusters requested. 734 * fillwith - put this value into the fat entry for the 735 * last allocated cluster. 736 * retcluster - put the first allocated cluster's number here. 737 * got - how many clusters were actually allocated. 738 */ 739 int 740 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, 741 u_long fillwith, u_long *retcluster, u_long *got) 742 { 743 u_long idx; 744 u_long len, newst, foundl, cn, l; 745 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 746 u_int map; 747 748 #ifdef MSDOSFS_DEBUG 749 kprintf("clusteralloc(): find %lu clusters\n",count); 750 #endif 751 if (start) { 752 if ((len = chainlength(pmp, start, count)) >= count) 753 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 754 } else 755 len = 0; 756 757 /* 758 * Start at a (pseudo) random place to maximize cluster runs 759 * under multiple writers. 760 */ 761 newst = krandom() % (pmp->pm_maxcluster + 1); 762 foundl = 0; 763 764 for (cn = newst; cn <= pmp->pm_maxcluster;) { 765 idx = cn / N_INUSEBITS; 766 map = pmp->pm_inusemap[idx]; 767 map |= (1 << (cn % N_INUSEBITS)) - 1; 768 if (map != (u_int)-1) { 769 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 770 if ((l = chainlength(pmp, cn, count)) >= count) 771 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 772 if (l > foundl) { 773 foundcn = cn; 774 foundl = l; 775 } 776 cn += l + 1; 777 continue; 778 } 779 cn += N_INUSEBITS - cn % N_INUSEBITS; 780 } 781 for (cn = 0; cn < newst;) { 782 idx = cn / N_INUSEBITS; 783 map = pmp->pm_inusemap[idx]; 784 map |= (1 << (cn % N_INUSEBITS)) - 1; 785 if (map != (u_int)-1) { 786 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 787 if ((l = chainlength(pmp, cn, count)) >= count) 788 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 789 if (l > foundl) { 790 foundcn = cn; 791 foundl = l; 792 } 793 cn += l + 1; 794 continue; 795 } 796 cn += N_INUSEBITS - cn % N_INUSEBITS; 797 } 798 799 if (!foundl) 800 return (ENOSPC); 801 802 if (len) 803 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 804 else 805 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 806 } 807 808 809 /* 810 * Free a chain of clusters. 811 * 812 * pmp - address of the msdosfs mount structure for the filesystem 813 * containing the cluster chain to be freed. 814 * startcluster - number of the 1st cluster in the chain of clusters to be 815 * freed. 816 */ 817 int 818 freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 819 { 820 int error; 821 struct buf *bp = NULL; 822 u_long bn, bo, bsize, byteoffset; 823 u_long readcn, lbn = -1; 824 825 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 826 byteoffset = FATOFS(pmp, cluster); 827 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 828 if (lbn != bn) { 829 if (bp) 830 updatefats(pmp, bp, lbn); 831 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 832 if (error) { 833 brelse(bp); 834 return (error); 835 } 836 lbn = bn; 837 } 838 usemap_free(pmp, cluster); 839 switch (pmp->pm_fatmask) { 840 case FAT12_MASK: 841 readcn = getushort(&bp->b_data[bo]); 842 if (cluster & 1) { 843 cluster = readcn >> 4; 844 readcn &= 0x000f; 845 readcn |= MSDOSFSFREE << 4; 846 } else { 847 cluster = readcn; 848 readcn &= 0xf000; 849 readcn |= MSDOSFSFREE & 0xfff; 850 } 851 putushort(&bp->b_data[bo], readcn); 852 break; 853 case FAT16_MASK: 854 cluster = getushort(&bp->b_data[bo]); 855 putushort(&bp->b_data[bo], MSDOSFSFREE); 856 break; 857 case FAT32_MASK: 858 cluster = getulong(&bp->b_data[bo]); 859 putulong(&bp->b_data[bo], 860 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 861 break; 862 } 863 cluster &= pmp->pm_fatmask; 864 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 865 cluster |= pmp->pm_fatmask; 866 } 867 if (bp) 868 updatefats(pmp, bp, bn); 869 return (0); 870 } 871 872 /* 873 * Read in fat blocks looking for free clusters. For every free cluster 874 * found turn off its corresponding bit in the pm_inusemap. 875 */ 876 int 877 fillinusemap(struct msdosfsmount *pmp) 878 { 879 struct buf *bp = NULL; 880 u_long cn, readcn; 881 int error; 882 u_long bn, bo, bsize, byteoffset; 883 884 /* 885 * Mark all clusters in use, we mark the free ones in the fat scan 886 * loop further down. 887 */ 888 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 889 pmp->pm_inusemap[cn] = (u_int)-1; 890 891 /* 892 * Figure how many free clusters are in the filesystem by ripping 893 * through the fat counting the number of entries whose content is 894 * zero. These represent free clusters. 895 */ 896 pmp->pm_freeclustercount = 0; 897 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 898 byteoffset = FATOFS(pmp, cn); 899 bo = byteoffset % pmp->pm_fatblocksize; 900 if (!bo || !bp) { 901 /* Read new FAT block */ 902 if (bp) 903 brelse(bp); 904 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 905 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 906 if (error) { 907 brelse(bp); 908 return (error); 909 } 910 } 911 if (FAT32(pmp)) 912 readcn = getulong(&bp->b_data[bo]); 913 else 914 readcn = getushort(&bp->b_data[bo]); 915 if (FAT12(pmp) && (cn & 1)) 916 readcn >>= 4; 917 readcn &= pmp->pm_fatmask; 918 919 if (readcn == 0) 920 usemap_free(pmp, cn); 921 } 922 brelse(bp); 923 return (0); 924 } 925 926 /* 927 * Allocate a new cluster and chain it onto the end of the file. 928 * 929 * dep - the file to extend 930 * count - number of clusters to allocate 931 * bpp - where to return the address of the buf header for the first new 932 * file block 933 * ncp - where to put cluster number of the first newly allocated cluster 934 * If this pointer is 0, do not return the cluster number. 935 * flags - see fat.h 936 * 937 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 938 * the de_flag field of the denode and it does not change the de_FileSize 939 * field. This is left for the caller to do. 940 */ 941 int 942 extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, 943 int flags) 944 { 945 int error; 946 u_long frcn; 947 u_long cn, got; 948 struct msdosfsmount *pmp = dep->de_pmp; 949 struct buf *bp; 950 951 /* 952 * Don't try to extend the root directory 953 */ 954 if (dep->de_StartCluster == MSDOSFSROOT 955 && (dep->de_Attributes & ATTR_DIRECTORY)) { 956 kprintf("extendfile(): attempt to extend root directory\n"); 957 return (ENOSPC); 958 } 959 960 /* 961 * If the "file's last cluster" cache entry is empty, and the file 962 * is not empty, then fill the cache entry by calling pcbmap(). 963 */ 964 fc_fileextends++; 965 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 966 dep->de_StartCluster != 0) { 967 fc_lfcempty++; 968 error = pcbmap(dep, 0xffff, NULL, &cn, NULL); 969 /* we expect it to return E2BIG */ 970 if (error != E2BIG) 971 return (error); 972 } 973 974 while (count > 0) { 975 /* 976 * Allocate a new cluster chain and cat onto the end of the 977 * file. * If the file is empty we make de_StartCluster point 978 * to the new block. Note that de_StartCluster being 0 is 979 * sufficient to be sure the file is empty since we exclude 980 * attempts to extend the root directory above, and the root 981 * dir is the only file with a startcluster of 0 that has 982 * blocks allocated (sort of). 983 */ 984 if (dep->de_StartCluster == 0) 985 cn = 0; 986 else 987 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 988 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 989 if (error) 990 return (error); 991 992 count -= got; 993 994 /* 995 * Give them the filesystem relative cluster number if they want 996 * it. 997 */ 998 if (ncp) { 999 *ncp = cn; 1000 ncp = NULL; 1001 } 1002 1003 if (dep->de_StartCluster == 0) { 1004 dep->de_StartCluster = cn; 1005 frcn = 0; 1006 } else { 1007 error = fatentry(FAT_SET, pmp, 1008 dep->de_fc[FC_LASTFC].fc_fsrcn, 1009 0, cn); 1010 if (error) { 1011 clusterfree(pmp, cn, NULL); 1012 return (error); 1013 } 1014 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1015 } 1016 1017 /* 1018 * Update the "last cluster of the file" entry in the 1019 * denode's fat cache. 1020 */ 1021 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1022 1023 if (flags & DE_CLEAR) { 1024 while (got-- > 0) { 1025 /* 1026 * Get the buf header for the new block of the file. 1027 */ 1028 if (dep->de_Attributes & ATTR_DIRECTORY) { 1029 bp = getblk(pmp->pm_devvp, 1030 xcntodoff(pmp, cn), 1031 pmp->pm_bpcluster, 0, 0); 1032 ++cn; 1033 } else { 1034 daddr_t dblkno; 1035 1036 bp = getblk(DETOV(dep), 1037 de_cn2doff(pmp, frcn), 1038 pmp->pm_bpcluster, 0, 0); 1039 ++frcn; 1040 /* 1041 * Do the bmap now, as in msdosfs_write 1042 */ 1043 if (pcbmap(dep, 1044 de_bn2cn(pmp, de_off2bn(pmp, bp->b_bio1.bio_offset)), 1045 &dblkno, NULL, NULL)) { 1046 bp->b_bio2.bio_offset = NOOFFSET; 1047 } else { 1048 bp->b_bio2.bio_offset = de_bntodoff(pmp, dblkno); 1049 } 1050 if (bp->b_bio2.bio_offset == NOOFFSET) 1051 panic("extendfile: pcbmap"); 1052 } 1053 clrbuf(bp); 1054 if (bpp) { 1055 *bpp = bp; 1056 bpp = NULL; 1057 } else 1058 bdwrite(bp); 1059 } 1060 } 1061 } 1062 1063 return (0); 1064 } 1065