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