1 /* $FreeBSD: src/sys/msdosfs/msdosfs_fat.c,v 1.23 2000/01/27 14:43:06 nyan Exp $ */ 2 /* $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $ */ 3 4 /*- 5 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank. 6 * Copyright (C) 1994, 1995, 1997 TooLs GmbH. 7 * All rights reserved. 8 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below). 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by TooLs GmbH. 21 * 4. The name of TooLs GmbH may not be used to endorse or promote products 22 * derived from this software without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR 25 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 26 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 27 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 29 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 30 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 31 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 32 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 33 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 34 */ 35 /* 36 * Written by Paul Popelka (paulp@uts.amdahl.com) 37 * 38 * You can do anything you want with this software, just don't say you wrote 39 * it, and don't remove this notice. 40 * 41 * This software is provided "as is". 42 * 43 * The author supplies this software to be publicly redistributed on the 44 * understanding that the author is not responsible for the correct 45 * functioning of this software in any circumstances and is not liable for 46 * any damages caused by this software. 47 * 48 * October 1992 49 */ 50 51 /* 52 * kernel include files. 53 */ 54 #include <sys/param.h> 55 #include <sys/systm.h> 56 #include <sys/buf.h> 57 #include <sys/mount.h> /* to define statfs structure */ 58 #include <sys/vnode.h> /* to define vattr structure */ 59 60 #include <sys/buf2.h> 61 62 /* 63 * msdosfs include files. 64 */ 65 #include "bpb.h" 66 #include "msdosfsmount.h" 67 #include "direntry.h" 68 #include "denode.h" 69 #include "fat.h" 70 71 /* 72 * Fat cache stats. 73 */ 74 static int fc_fileextends; /* # of file extends */ 75 static int fc_lfcempty; /* # of time last file cluster cache entry 76 * was empty */ 77 static int fc_bmapcalls; /* # of times pcbmap was called */ 78 79 #define LMMAX 20 80 static int fc_lmdistance[LMMAX];/* counters for how far off the last 81 * cluster mapped entry was. */ 82 static int fc_largedistance; /* off by more than LMMAX */ 83 84 static int chainalloc (struct msdosfsmount *pmp, u_long start, 85 u_long count, u_long fillwith, 86 u_long *retcluster, u_long *got); 87 static int chainlength (struct msdosfsmount *pmp, u_long start, 88 u_long count); 89 static void fatblock (struct msdosfsmount *pmp, u_long ofs, 90 u_long *bnp, u_long *sizep, u_long *bop); 91 static int fatchain (struct msdosfsmount *pmp, u_long start, 92 u_long count, u_long fillwith); 93 static void fc_lookup (struct denode *dep, u_long findcn, 94 u_long *frcnp, u_long *fsrcnp); 95 static void updatefats (struct msdosfsmount *pmp, struct buf *bp, 96 u_long fatbn); 97 static __inline void 98 usemap_alloc (struct msdosfsmount *pmp, u_long cn); 99 static __inline void 100 usemap_free (struct msdosfsmount *pmp, u_long cn); 101 102 static void 103 fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp, u_long *sizep, 104 u_long *bop) 105 { 106 u_long bn, size; 107 108 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 109 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) 110 * DEV_BSIZE; 111 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 112 113 if (bnp) 114 *bnp = bn; 115 if (sizep) 116 *sizep = size; 117 if (bop) 118 *bop = ofs % pmp->pm_fatblocksize; 119 } 120 121 /* 122 * Map the logical cluster number of a file into a physical disk sector 123 * that is filesystem relative. 124 * 125 * dep - address of denode representing the file of interest 126 * findcn - file relative cluster whose filesystem relative cluster number 127 * and/or block number are/is to be found 128 * bnp - address of where to place the file system relative block number. 129 * If this pointer is null then don't return this quantity. 130 * cnp - address of where to place the file system relative cluster number. 131 * If this pointer is null then don't return this quantity. 132 * 133 * NOTE: Either bnp or cnp must be non-null. 134 * This function has one side effect. If the requested file relative cluster 135 * is beyond the end of file, then the actual number of clusters in the file 136 * is returned in *cnp. This is useful for determining how long a directory is. 137 * If cnp is null, nothing is returned. 138 */ 139 int 140 pcbmap(struct denode *dep, 141 u_long findcn, /* file relative cluster to get */ 142 daddr_t *bnp, /* returned filesys relative blk number */ 143 u_long *cnp, /* returned cluster number */ 144 int *sp) /* returned block size */ 145 { 146 int error; 147 u_long i; 148 u_long cn; 149 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */ 150 u_long byteoffset; 151 u_long bn; 152 u_long bo; 153 struct buf *bp = NULL; 154 u_long bp_bn = -1; 155 struct msdosfsmount *pmp = dep->de_pmp; 156 u_long bsize; 157 158 fc_bmapcalls++; 159 160 /* 161 * If they don't give us someplace to return a value then don't 162 * bother doing anything. 163 */ 164 if (bnp == NULL && cnp == NULL && sp == NULL) 165 return (0); 166 167 cn = dep->de_StartCluster; 168 /* 169 * The "file" that makes up the root directory is contiguous, 170 * permanently allocated, of fixed size, and is not made up of 171 * clusters. If the cluster number is beyond the end of the root 172 * directory, then return the number of clusters in the file. 173 */ 174 if (cn == MSDOSFSROOT) { 175 if (dep->de_Attributes & ATTR_DIRECTORY) { 176 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 177 if (cnp) 178 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 179 return (E2BIG); 180 } 181 if (bnp) 182 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 183 if (cnp) 184 *cnp = MSDOSFSROOT; 185 if (sp) 186 *sp = min(pmp->pm_bpcluster, 187 dep->de_FileSize - de_cn2off(pmp, findcn)); 188 return (0); 189 } else { /* just an empty file */ 190 if (cnp) 191 *cnp = 0; 192 return (E2BIG); 193 } 194 } 195 196 /* 197 * All other files do I/O in cluster sized blocks 198 */ 199 if (sp) 200 *sp = pmp->pm_bpcluster; 201 202 /* 203 * Rummage around in the fat cache, maybe we can avoid tromping 204 * thru every fat entry for the file. And, keep track of how far 205 * off the cache was from where we wanted to be. 206 */ 207 i = 0; 208 fc_lookup(dep, findcn, &i, &cn); 209 if ((bn = findcn - i) >= LMMAX) 210 fc_largedistance++; 211 else 212 fc_lmdistance[bn]++; 213 214 /* 215 * Handle all other files or directories the normal way. 216 */ 217 for (; i < findcn; i++) { 218 /* 219 * Stop with all reserved clusters, not just with EOF. 220 */ 221 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 222 goto hiteof; 223 byteoffset = FATOFS(pmp, cn); 224 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 225 if (bn != bp_bn) { 226 if (bp) 227 brelse(bp); 228 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 229 if (error) { 230 brelse(bp); 231 return (error); 232 } 233 bp_bn = bn; 234 } 235 prevcn = cn; 236 if (FAT32(pmp)) 237 cn = getulong(&bp->b_data[bo]); 238 else 239 cn = getushort(&bp->b_data[bo]); 240 if (FAT12(pmp) && (prevcn & 1)) 241 cn >>= 4; 242 cn &= pmp->pm_fatmask; 243 244 /* 245 * Force the special cluster numbers 246 * to be the same for all cluster sizes 247 * to let the rest of msdosfs handle 248 * all cases the same. 249 */ 250 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 251 cn |= ~pmp->pm_fatmask; 252 } 253 254 if (!MSDOSFSEOF(pmp, cn)) { 255 if (bp) 256 brelse(bp); 257 if (bnp) 258 *bnp = xcntobn(pmp, cn); 259 if (cnp) 260 *cnp = cn; 261 fc_setcache(dep, FC_LASTMAP, i, cn); 262 return (0); 263 } 264 265 hiteof:; 266 if (cnp) 267 *cnp = i; 268 if (bp) 269 brelse(bp); 270 /* update last file cluster entry in the fat cache */ 271 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 272 return (E2BIG); 273 } 274 275 /* 276 * Find the closest entry in the fat cache to the cluster we are looking 277 * for. 278 */ 279 static void 280 fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp, u_long *fsrcnp) 281 { 282 int i; 283 u_long cn; 284 struct fatcache *closest = NULL; 285 286 for (i = 0; i < FC_SIZE; i++) { 287 cn = dep->de_fc[i].fc_frcn; 288 if (cn != FCE_EMPTY && cn <= findcn) { 289 if (closest == NULL || cn > closest->fc_frcn) 290 closest = &dep->de_fc[i]; 291 } 292 } 293 if (closest) { 294 *frcnp = closest->fc_frcn; 295 *fsrcnp = closest->fc_fsrcn; 296 } 297 } 298 299 /* 300 * Purge the fat cache in denode dep of all entries relating to file 301 * relative cluster frcn and beyond. 302 */ 303 void 304 fc_purge(struct denode *dep, u_int frcn) 305 { 306 int i; 307 struct fatcache *fcp; 308 309 fcp = dep->de_fc; 310 for (i = 0; i < FC_SIZE; i++, fcp++) { 311 if (fcp->fc_frcn >= frcn) 312 fcp->fc_frcn = FCE_EMPTY; 313 } 314 } 315 316 /* 317 * Update the fat. 318 * If mirroring the fat, update all copies, with the first copy as last. 319 * Else update only the current fat (ignoring the others). 320 * 321 * pmp - msdosfsmount structure for filesystem to update 322 * bp - addr of modified fat block 323 * fatbn - block number relative to begin of filesystem of the modified fat block. 324 */ 325 static void 326 updatefats(struct msdosfsmount *pmp, struct buf *bp, u_long fatbn) 327 { 328 int i; 329 struct buf *bpn; 330 331 #ifdef MSDOSFS_DEBUG 332 kprintf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn); 333 #endif 334 335 /* 336 * If we have an FSInfo block, update it. 337 */ 338 if (pmp->pm_fsinfo) { 339 u_long cn = pmp->pm_nxtfree; 340 341 if (pmp->pm_freeclustercount 342 && (pmp->pm_inusemap[cn / N_INUSEBITS] 343 & (1 << (cn % N_INUSEBITS)))) { 344 /* 345 * The cluster indicated in FSInfo isn't free 346 * any longer. Got get a new free one. 347 */ 348 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS) 349 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1) 350 break; 351 pmp->pm_nxtfree = cn 352 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS] 353 ^ (u_int)-1) - 1; 354 } 355 if (bread(pmp->pm_devvp, de_bntodoff(pmp, pmp->pm_fsinfo), fsi_size(pmp), &bpn) != 0) { 356 /* 357 * Ignore the error, but turn off FSInfo update for the future. 358 */ 359 pmp->pm_fsinfo = 0; 360 brelse(bpn); 361 } else { 362 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 363 364 putulong(fp->fsinfree, pmp->pm_freeclustercount); 365 putulong(fp->fsinxtfree, pmp->pm_nxtfree); 366 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 367 bwrite(bpn); 368 else 369 bdwrite(bpn); 370 } 371 } 372 373 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 374 /* 375 * Now copy the block(s) of the modified fat to the other copies of 376 * the fat and write them out. This is faster than reading in the 377 * other fats and then writing them back out. This could tie up 378 * the fat for quite a while. Preventing others from accessing it. 379 * To prevent us from going after the fat quite so much we use 380 * delayed writes, unless they specfied "synchronous" when the 381 * filesystem was mounted. If synch is asked for then use 382 * bwrite()'s and really slow things down. 383 */ 384 for (i = 1; i < pmp->pm_FATs; i++) { 385 fatbn += pmp->pm_FATsecs; 386 /* getblk() never fails */ 387 bpn = getblk(pmp->pm_devvp, de_bntodoff(pmp, fatbn), 388 bp->b_bcount, 0, 0); 389 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 390 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 391 bwrite(bpn); 392 else 393 bdwrite(bpn); 394 } 395 } 396 397 /* 398 * Write out the first (or current) fat last. 399 */ 400 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 401 bwrite(bp); 402 else 403 bdwrite(bp); 404 /* 405 * Maybe update fsinfo sector here? 406 */ 407 } 408 409 /* 410 * Updating entries in 12 bit fats is a pain in the butt. 411 * 412 * The following picture shows where nibbles go when moving from a 12 bit 413 * cluster number into the appropriate bytes in the FAT. 414 * 415 * byte m byte m+1 byte m+2 416 * +----+----+ +----+----+ +----+----+ 417 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 418 * +----+----+ +----+----+ +----+----+ 419 * 420 * +----+----+----+ +----+----+----+ 421 * | 3 0 1 | | 4 5 2 | 422 * +----+----+----+ +----+----+----+ 423 * cluster n cluster n+1 424 * 425 * Where n is even. m = n + (n >> 2) 426 * 427 */ 428 static __inline void 429 usemap_alloc(struct msdosfsmount *pmp, u_long cn) 430 { 431 432 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 433 pmp->pm_freeclustercount--; 434 } 435 436 static __inline void 437 usemap_free(struct msdosfsmount *pmp, u_long cn) 438 { 439 440 pmp->pm_freeclustercount++; 441 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 442 } 443 444 int 445 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp) 446 { 447 int error; 448 u_long oldcn; 449 450 usemap_free(pmp, cluster); 451 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 452 if (error) { 453 usemap_alloc(pmp, cluster); 454 return (error); 455 } 456 /* 457 * If the cluster was successfully marked free, then update 458 * the count of free clusters, and turn off the "allocated" 459 * bit in the "in use" cluster bit map. 460 */ 461 if (oldcnp) 462 *oldcnp = oldcn; 463 return (0); 464 } 465 466 /* 467 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 468 * 469 * function - whether to get or set a fat entry 470 * pmp - address of the msdosfsmount structure for the filesystem 471 * whose fat is to be manipulated. 472 * cn - which cluster is of interest 473 * oldcontents - address of a word that is to receive the contents of the 474 * cluster'th entry if this is a get function 475 * newcontents - the new value to be written into the cluster'th element of 476 * the fat if this is a set function. 477 * 478 * This function can also be used to free a cluster by setting the fat entry 479 * for a cluster to 0. 480 * 481 * All copies of the fat are updated if this is a set function. NOTE: If 482 * fatentry() marks a cluster as free it does not update the inusemap in 483 * the msdosfsmount structure. This is left to the caller. 484 */ 485 int 486 fatentry(int function, struct msdosfsmount *pmp, u_long cn, u_long *oldcontents, 487 u_long newcontents) 488 { 489 int error; 490 u_long readcn; 491 u_long bn, bo, bsize, byteoffset; 492 struct buf *bp; 493 494 #ifdef MSDOSFS_DEBUG 495 kprintf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n", 496 function, pmp, cn, oldcontents, newcontents); 497 #endif 498 499 #ifdef DIAGNOSTIC 500 /* 501 * Be sure they asked us to do something. 502 */ 503 if ((function & (FAT_SET | FAT_GET)) == 0) { 504 kprintf("fatentry(): function code doesn't specify get or set\n"); 505 return (EINVAL); 506 } 507 508 /* 509 * If they asked us to return a cluster number but didn't tell us 510 * where to put it, give them an error. 511 */ 512 if ((function & FAT_GET) && oldcontents == NULL) { 513 kprintf("fatentry(): get function with no place to put result\n"); 514 return (EINVAL); 515 } 516 #endif 517 518 /* 519 * Be sure the requested cluster is in the filesystem. 520 */ 521 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 522 return (EINVAL); 523 524 byteoffset = FATOFS(pmp, cn); 525 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 526 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 527 if (error) { 528 brelse(bp); 529 return (error); 530 } 531 532 if (function & FAT_GET) { 533 if (FAT32(pmp)) 534 readcn = getulong(&bp->b_data[bo]); 535 else 536 readcn = getushort(&bp->b_data[bo]); 537 if (FAT12(pmp) & (cn & 1)) 538 readcn >>= 4; 539 readcn &= pmp->pm_fatmask; 540 /* map reserved fat entries to same values for all fats */ 541 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 542 readcn |= ~pmp->pm_fatmask; 543 *oldcontents = readcn; 544 } 545 if (function & FAT_SET) { 546 switch (pmp->pm_fatmask) { 547 case FAT12_MASK: 548 readcn = getushort(&bp->b_data[bo]); 549 if (cn & 1) { 550 readcn &= 0x000f; 551 readcn |= newcontents << 4; 552 } else { 553 readcn &= 0xf000; 554 readcn |= newcontents & 0xfff; 555 } 556 putushort(&bp->b_data[bo], readcn); 557 break; 558 case FAT16_MASK: 559 putushort(&bp->b_data[bo], newcontents); 560 break; 561 case FAT32_MASK: 562 /* 563 * According to spec we have to retain the 564 * high order bits of the fat entry. 565 */ 566 readcn = getulong(&bp->b_data[bo]); 567 readcn &= ~FAT32_MASK; 568 readcn |= newcontents & FAT32_MASK; 569 putulong(&bp->b_data[bo], readcn); 570 break; 571 } 572 updatefats(pmp, bp, bn); 573 bp = NULL; 574 pmp->pm_fmod = 1; 575 } 576 if (bp) 577 brelse(bp); 578 return (0); 579 } 580 581 /* 582 * Update a contiguous cluster chain 583 * 584 * pmp - mount point 585 * start - first cluster of chain 586 * count - number of clusters in chain 587 * fillwith - what to write into fat entry of last cluster 588 */ 589 static int 590 fatchain(struct msdosfsmount *pmp, u_long start, u_long count, u_long fillwith) 591 { 592 int error; 593 u_long bn, bo, bsize, byteoffset, readcn, newc; 594 struct buf *bp; 595 596 #ifdef MSDOSFS_DEBUG 597 kprintf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n", 598 pmp, start, count, fillwith); 599 #endif 600 /* 601 * Be sure the clusters are in the filesystem. 602 */ 603 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 604 return (EINVAL); 605 606 while (count > 0) { 607 byteoffset = FATOFS(pmp, start); 608 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 609 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 610 if (error) { 611 brelse(bp); 612 return (error); 613 } 614 while (count > 0) { 615 start++; 616 newc = --count > 0 ? start : fillwith; 617 switch (pmp->pm_fatmask) { 618 case FAT12_MASK: 619 readcn = getushort(&bp->b_data[bo]); 620 if (start & 1) { 621 readcn &= 0xf000; 622 readcn |= newc & 0xfff; 623 } else { 624 readcn &= 0x000f; 625 readcn |= newc << 4; 626 } 627 putushort(&bp->b_data[bo], readcn); 628 bo++; 629 if (!(start & 1)) 630 bo++; 631 break; 632 case FAT16_MASK: 633 putushort(&bp->b_data[bo], newc); 634 bo += 2; 635 break; 636 case FAT32_MASK: 637 readcn = getulong(&bp->b_data[bo]); 638 readcn &= ~pmp->pm_fatmask; 639 readcn |= newc & pmp->pm_fatmask; 640 putulong(&bp->b_data[bo], readcn); 641 bo += 4; 642 break; 643 } 644 if (bo >= bsize) 645 break; 646 } 647 updatefats(pmp, bp, bn); 648 } 649 pmp->pm_fmod = 1; 650 return (0); 651 } 652 653 /* 654 * Check the length of a free cluster chain starting at start. 655 * 656 * pmp - mount point 657 * start - start of chain 658 * count - maximum interesting length 659 */ 660 static int 661 chainlength(struct msdosfsmount *pmp, u_long start, u_long count) 662 { 663 u_long idx, max_idx; 664 u_int map; 665 u_long len; 666 667 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 668 idx = start / N_INUSEBITS; 669 start %= N_INUSEBITS; 670 map = pmp->pm_inusemap[idx]; 671 map &= ~((1 << start) - 1); 672 if (map) { 673 len = ffs(map) - 1 - start; 674 return (len > count ? count : len); 675 } 676 len = N_INUSEBITS - start; 677 if (len >= count) 678 return (count); 679 while (++idx <= max_idx) { 680 if (len >= count) 681 break; 682 map = pmp->pm_inusemap[idx]; 683 if (map) { 684 len += ffs(map) - 1; 685 break; 686 } 687 len += N_INUSEBITS; 688 } 689 return (len > count ? count : len); 690 } 691 692 /* 693 * Allocate contigous free clusters. 694 * 695 * pmp - mount point. 696 * start - start of cluster chain. 697 * count - number of clusters to allocate. 698 * fillwith - put this value into the fat entry for the 699 * last allocated cluster. 700 * retcluster - put the first allocated cluster's number here. 701 * got - how many clusters were actually allocated. 702 */ 703 static int 704 chainalloc(struct msdosfsmount *pmp, u_long start, u_long count, 705 u_long fillwith, u_long *retcluster, u_long *got) 706 { 707 int error; 708 u_long cl, n; 709 710 for (cl = start, n = count; n-- > 0;) 711 usemap_alloc(pmp, cl++); 712 713 error = fatchain(pmp, start, count, fillwith); 714 if (error != 0) 715 return (error); 716 #ifdef MSDOSFS_DEBUG 717 kprintf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n", 718 start, count); 719 #endif 720 if (retcluster) 721 *retcluster = start; 722 if (got) 723 *got = count; 724 return (0); 725 } 726 727 /* 728 * Allocate contiguous free clusters. 729 * 730 * pmp - mount point. 731 * start - preferred start of cluster chain. 732 * count - number of clusters requested. 733 * fillwith - put this value into the fat entry for the 734 * last allocated cluster. 735 * retcluster - put the first allocated cluster's number here. 736 * got - how many clusters were actually allocated. 737 */ 738 int 739 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count, 740 u_long fillwith, u_long *retcluster, u_long *got) 741 { 742 u_long idx; 743 u_long len, newst, foundl, cn, l; 744 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */ 745 u_int map; 746 747 #ifdef MSDOSFS_DEBUG 748 kprintf("clusteralloc(): find %lu clusters\n",count); 749 #endif 750 if (start) { 751 if ((len = chainlength(pmp, start, count)) >= count) 752 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 753 } else 754 len = 0; 755 756 /* 757 * Start at a (pseudo) random place to maximize cluster runs 758 * under multiple writers. 759 */ 760 newst = krandom() % (pmp->pm_maxcluster + 1); 761 foundl = 0; 762 763 for (cn = newst; cn <= pmp->pm_maxcluster;) { 764 idx = cn / N_INUSEBITS; 765 map = pmp->pm_inusemap[idx]; 766 map |= (1 << (cn % N_INUSEBITS)) - 1; 767 if (map != (u_int)-1) { 768 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 769 if ((l = chainlength(pmp, cn, count)) >= count) 770 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 771 if (l > foundl) { 772 foundcn = cn; 773 foundl = l; 774 } 775 cn += l + 1; 776 continue; 777 } 778 cn += N_INUSEBITS - cn % N_INUSEBITS; 779 } 780 for (cn = 0; cn < newst;) { 781 idx = cn / N_INUSEBITS; 782 map = pmp->pm_inusemap[idx]; 783 map |= (1 << (cn % N_INUSEBITS)) - 1; 784 if (map != (u_int)-1) { 785 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 786 if ((l = chainlength(pmp, cn, count)) >= count) 787 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 788 if (l > foundl) { 789 foundcn = cn; 790 foundl = l; 791 } 792 cn += l + 1; 793 continue; 794 } 795 cn += N_INUSEBITS - cn % N_INUSEBITS; 796 } 797 798 if (!foundl) 799 return (ENOSPC); 800 801 if (len) 802 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 803 else 804 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 805 } 806 807 808 /* 809 * Free a chain of clusters. 810 * 811 * pmp - address of the msdosfs mount structure for the filesystem 812 * containing the cluster chain to be freed. 813 * startcluster - number of the 1st cluster in the chain of clusters to be 814 * freed. 815 */ 816 int 817 freeclusterchain(struct msdosfsmount *pmp, u_long cluster) 818 { 819 int error; 820 struct buf *bp = NULL; 821 u_long bn, bo, bsize, byteoffset; 822 u_long readcn, lbn = -1; 823 824 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 825 byteoffset = FATOFS(pmp, cluster); 826 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 827 if (lbn != bn) { 828 if (bp) 829 updatefats(pmp, bp, lbn); 830 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 831 if (error) { 832 brelse(bp); 833 return (error); 834 } 835 lbn = bn; 836 } 837 usemap_free(pmp, cluster); 838 switch (pmp->pm_fatmask) { 839 case FAT12_MASK: 840 readcn = getushort(&bp->b_data[bo]); 841 if (cluster & 1) { 842 cluster = readcn >> 4; 843 readcn &= 0x000f; 844 readcn |= MSDOSFSFREE << 4; 845 } else { 846 cluster = readcn; 847 readcn &= 0xf000; 848 readcn |= MSDOSFSFREE & 0xfff; 849 } 850 putushort(&bp->b_data[bo], readcn); 851 break; 852 case FAT16_MASK: 853 cluster = getushort(&bp->b_data[bo]); 854 putushort(&bp->b_data[bo], MSDOSFSFREE); 855 break; 856 case FAT32_MASK: 857 cluster = getulong(&bp->b_data[bo]); 858 putulong(&bp->b_data[bo], 859 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 860 break; 861 } 862 cluster &= pmp->pm_fatmask; 863 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 864 cluster |= pmp->pm_fatmask; 865 } 866 if (bp) 867 updatefats(pmp, bp, bn); 868 return (0); 869 } 870 871 /* 872 * Read in fat blocks looking for free clusters. For every free cluster 873 * found turn off its corresponding bit in the pm_inusemap. 874 */ 875 int 876 fillinusemap(struct msdosfsmount *pmp) 877 { 878 struct buf *bp = NULL; 879 u_long cn, readcn; 880 int error; 881 u_long bn, bo, bsize, byteoffset; 882 883 /* 884 * Mark all clusters in use, we mark the free ones in the fat scan 885 * loop further down. 886 */ 887 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++) 888 pmp->pm_inusemap[cn] = (u_int)-1; 889 890 /* 891 * Figure how many free clusters are in the filesystem by ripping 892 * through the fat counting the number of entries whose content is 893 * zero. These represent free clusters. 894 */ 895 pmp->pm_freeclustercount = 0; 896 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 897 byteoffset = FATOFS(pmp, cn); 898 bo = byteoffset % pmp->pm_fatblocksize; 899 if (!bo || !bp) { 900 /* Read new FAT block */ 901 if (bp) 902 brelse(bp); 903 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 904 error = bread(pmp->pm_devvp, de_bntodoff(pmp, bn), bsize, &bp); 905 if (error) { 906 brelse(bp); 907 return (error); 908 } 909 } 910 if (FAT32(pmp)) 911 readcn = getulong(&bp->b_data[bo]); 912 else 913 readcn = getushort(&bp->b_data[bo]); 914 if (FAT12(pmp) && (cn & 1)) 915 readcn >>= 4; 916 readcn &= pmp->pm_fatmask; 917 918 if (readcn == 0) 919 usemap_free(pmp, cn); 920 } 921 brelse(bp); 922 return (0); 923 } 924 925 /* 926 * Allocate a new cluster and chain it onto the end of the file. 927 * 928 * dep - the file to extend 929 * count - number of clusters to allocate 930 * bpp - where to return the address of the buf header for the first new 931 * file block 932 * ncp - where to put cluster number of the first newly allocated cluster 933 * If this pointer is 0, do not return the cluster number. 934 * flags - see fat.h 935 * 936 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 937 * the de_flag field of the denode and it does not change the de_FileSize 938 * field. This is left for the caller to do. 939 */ 940 int 941 extendfile(struct denode *dep, u_long count, struct buf **bpp, u_long *ncp, 942 int flags) 943 { 944 int error; 945 u_long frcn; 946 u_long cn, got; 947 struct msdosfsmount *pmp = dep->de_pmp; 948 struct buf *bp; 949 950 /* 951 * Don't try to extend the root directory 952 */ 953 if (dep->de_StartCluster == MSDOSFSROOT 954 && (dep->de_Attributes & ATTR_DIRECTORY)) { 955 kprintf("extendfile(): attempt to extend root directory\n"); 956 return (ENOSPC); 957 } 958 959 /* 960 * If the "file's last cluster" cache entry is empty, and the file 961 * is not empty, then fill the cache entry by calling pcbmap(). 962 */ 963 fc_fileextends++; 964 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 965 dep->de_StartCluster != 0) { 966 fc_lfcempty++; 967 error = pcbmap(dep, 0xffff, NULL, &cn, NULL); 968 /* we expect it to return E2BIG */ 969 if (error != E2BIG) 970 return (error); 971 } 972 973 while (count > 0) { 974 /* 975 * Allocate a new cluster chain and cat onto the end of the 976 * file. * If the file is empty we make de_StartCluster point 977 * to the new block. Note that de_StartCluster being 0 is 978 * sufficient to be sure the file is empty since we exclude 979 * attempts to extend the root directory above, and the root 980 * dir is the only file with a startcluster of 0 that has 981 * blocks allocated (sort of). 982 */ 983 if (dep->de_StartCluster == 0) 984 cn = 0; 985 else 986 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 987 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got); 988 if (error) 989 return (error); 990 991 count -= got; 992 993 /* 994 * Give them the filesystem relative cluster number if they want 995 * it. 996 */ 997 if (ncp) { 998 *ncp = cn; 999 ncp = NULL; 1000 } 1001 1002 if (dep->de_StartCluster == 0) { 1003 dep->de_StartCluster = cn; 1004 frcn = 0; 1005 } else { 1006 error = fatentry(FAT_SET, pmp, 1007 dep->de_fc[FC_LASTFC].fc_fsrcn, 1008 0, cn); 1009 if (error) { 1010 clusterfree(pmp, cn, NULL); 1011 return (error); 1012 } 1013 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1014 } 1015 1016 /* 1017 * Update the "last cluster of the file" entry in the 1018 * denode's fat cache. 1019 */ 1020 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1021 1022 if (flags & DE_CLEAR) { 1023 while (got-- > 0) { 1024 /* 1025 * Get the buf header for the new block of the file. 1026 */ 1027 if (dep->de_Attributes & ATTR_DIRECTORY) { 1028 bp = getblk(pmp->pm_devvp, 1029 xcntodoff(pmp, cn), 1030 pmp->pm_bpcluster, 0, 0); 1031 ++cn; 1032 } else { 1033 daddr_t dblkno; 1034 1035 bp = getblk(DETOV(dep), 1036 de_cn2doff(pmp, frcn), 1037 pmp->pm_bpcluster, 0, 0); 1038 ++frcn; 1039 /* 1040 * Do the bmap now, as in msdosfs_write 1041 */ 1042 if (pcbmap(dep, 1043 de_bn2cn(pmp, de_off2bn(pmp, bp->b_bio1.bio_offset)), 1044 &dblkno, NULL, NULL)) { 1045 bp->b_bio2.bio_offset = NOOFFSET; 1046 } else { 1047 bp->b_bio2.bio_offset = de_bntodoff(pmp, dblkno); 1048 } 1049 if (bp->b_bio2.bio_offset == NOOFFSET) 1050 panic("extendfile: pcbmap"); 1051 } 1052 clrbuf(bp); 1053 if (bpp) { 1054 *bpp = bp; 1055 bpp = NULL; 1056 } else 1057 bdwrite(bp); 1058 } 1059 } 1060 } 1061 1062 return (0); 1063 } 1064