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sys/msdosfs/msdosfs_fat.c
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1 /* $OpenBSD: msdosfs_fat.c,v 1.34 2021/03/11 13:31:35 jsg Exp $ */ 2 /* $NetBSD: msdosfs_fat.c,v 1.26 1997/10/17 11:24:02 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/namei.h> 58 #include <sys/mount.h> /* to define statfs structure */ 59 #include <sys/vnode.h> /* to define vattr structure */ 60 #include <sys/lock.h> 61 #include <sys/errno.h> 62 #include <sys/dirent.h> 63 64 /* 65 * msdosfs include files. 66 */ 67 #include <msdosfs/bpb.h> 68 #include <msdosfs/msdosfsmount.h> 69 #include <msdosfs/direntry.h> 70 #include <msdosfs/denode.h> 71 #include <msdosfs/fat.h> 72 73 /* 74 * Fat cache stats. 75 */ 76 int fc_fileextends; /* # of file extends */ 77 int fc_lfcempty; /* # of time last file cluster cache entry 78 * was empty */ 79 int fc_bmapcalls; /* # of times pcbmap was called */ 80 81 #define LMMAX 20 82 int fc_lmdistance[LMMAX]; /* counters for how far off the last 83 * cluster mapped entry was. */ 84 int fc_largedistance; /* off by more than LMMAX */ 85 86 static void fatblock(struct msdosfsmount *, uint32_t, uint32_t *, uint32_t *, 87 uint32_t *); 88 void updatefats(struct msdosfsmount *, struct buf *, uint32_t); 89 static __inline void usemap_free(struct msdosfsmount *, uint32_t); 90 static __inline void usemap_alloc(struct msdosfsmount *, uint32_t); 91 static int fatchain(struct msdosfsmount *, uint32_t, uint32_t, uint32_t); 92 int chainlength(struct msdosfsmount *, uint32_t, uint32_t); 93 int chainalloc(struct msdosfsmount *, uint32_t, uint32_t, uint32_t, uint32_t *, 94 uint32_t *); 95 96 static void 97 fatblock(struct msdosfsmount *pmp, uint32_t ofs, uint32_t *bnp, uint32_t *sizep, 98 uint32_t *bop) 99 { 100 uint32_t bn, size; 101 102 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec; 103 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) * DEV_BSIZE; 104 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs; 105 106 if (bnp) 107 *bnp = bn; 108 if (sizep) 109 *sizep = size; 110 if (bop) 111 *bop = ofs % pmp->pm_fatblocksize; 112 } 113 114 /* 115 * Map the logical cluster number of a file into a physical disk sector 116 * that is filesystem relative. 117 * 118 * dep - address of denode representing the file of interest 119 * findcn - file relative cluster whose filesystem relative cluster number 120 * and/or block number are/is to be found 121 * bnp - address of where to place the file system relative block number. 122 * If this pointer is null then don't return this quantity. 123 * cnp - address of where to place the file system relative cluster number. 124 * If this pointer is null then don't return this quantity. 125 * sp - address of where to place the block size for the file/dir 126 * If this pointer is null then don't return this quantity. 127 * 128 * NOTE: Either bnp or cnp must be non-null. 129 * This function has one side effect. If the requested file relative cluster 130 * is beyond the end of file, then the actual number of clusters in the file 131 * is returned in *cnp. This is useful for determining how long a directory is. 132 * If cnp is null, nothing is returned. 133 */ 134 int 135 pcbmap(struct denode *dep, uint32_t findcn, daddr_t *bnp, uint32_t *cnp, 136 int *sp) 137 { 138 int error; 139 uint32_t i; 140 uint32_t cn; 141 uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */ 142 uint32_t byteoffset; 143 uint32_t bn; 144 uint32_t bo; 145 struct buf *bp = NULL; 146 uint32_t bp_bn = -1; 147 struct msdosfsmount *pmp = dep->de_pmp; 148 uint32_t bsize; 149 150 fc_bmapcalls++; 151 152 /* 153 * If they don't give us someplace to return a value then don't 154 * bother doing anything. 155 */ 156 if (bnp == NULL && cnp == NULL && sp == NULL) 157 return (0); 158 159 cn = dep->de_StartCluster; 160 /* 161 * The "file" that makes up the root directory is contiguous, 162 * permanently allocated, of fixed size, and is not made up of 163 * clusters. If the cluster number is beyond the end of the root 164 * directory, then return the number of clusters in the file. 165 */ 166 if (cn == MSDOSFSROOT) { 167 if (dep->de_Attributes & ATTR_DIRECTORY) { 168 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) { 169 if (cnp) 170 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize); 171 return (E2BIG); 172 } 173 if (bnp) 174 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn); 175 if (cnp) 176 *cnp = MSDOSFSROOT; 177 if (sp) 178 *sp = min(pmp->pm_bpcluster, 179 dep->de_FileSize - de_cn2off(pmp, findcn)); 180 return (0); 181 } else { /* just an empty file */ 182 if (cnp) 183 *cnp = 0; 184 return (E2BIG); 185 } 186 } 187 188 /* 189 * All other files do I/O in cluster sized blocks 190 */ 191 if (sp) 192 *sp = pmp->pm_bpcluster; 193 194 /* 195 * Rummage around in the fat cache, maybe we can avoid tromping 196 * thru every fat entry for the file. And, keep track of how far 197 * off the cache was from where we wanted to be. 198 */ 199 i = 0; 200 fc_lookup(dep, findcn, &i, &cn); 201 if ((bn = findcn - i) >= LMMAX) 202 fc_largedistance++; 203 else 204 fc_lmdistance[bn]++; 205 206 /* 207 * Handle all other files or directories the normal way. 208 */ 209 for (; i < findcn; i++) { 210 /* 211 * Stop with all reserved clusters, not just with EOF. 212 */ 213 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 214 goto hiteof; 215 byteoffset = FATOFS(pmp, cn); 216 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 217 if (bn != bp_bn) { 218 if (bp) 219 brelse(bp); 220 error = bread(pmp->pm_devvp, bn, bsize, &bp); 221 if (error) { 222 brelse(bp); 223 return (error); 224 } 225 bp_bn = bn; 226 } 227 prevcn = cn; 228 if (bo >= bsize) { 229 if (bp) 230 brelse(bp); 231 return (EIO); 232 } 233 if (FAT32(pmp)) 234 cn = getulong(&bp->b_data[bo]); 235 else 236 cn = getushort(&bp->b_data[bo]); 237 if (FAT12(pmp) && (prevcn & 1)) 238 cn >>= 4; 239 cn &= pmp->pm_fatmask; 240 241 /* 242 * Force the special cluster numbers 243 * to be the same for all cluster sizes 244 * to let the rest of msdosfs handle 245 * all cases the same. 246 */ 247 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD) 248 cn |= ~pmp->pm_fatmask; 249 } 250 251 if (!MSDOSFSEOF(pmp, cn)) { 252 if (bp) 253 brelse(bp); 254 if (bnp) 255 *bnp = cntobn(pmp, cn); 256 if (cnp) 257 *cnp = cn; 258 fc_setcache(dep, FC_LASTMAP, i, cn); 259 return (0); 260 } 261 262 hiteof: 263 if (cnp) 264 *cnp = i; 265 if (bp) 266 brelse(bp); 267 /* update last file cluster entry in the fat cache */ 268 fc_setcache(dep, FC_LASTFC, i - 1, prevcn); 269 return (E2BIG); 270 } 271 272 /* 273 * Find the closest entry in the fat cache to the cluster we are looking 274 * for. 275 */ 276 void 277 fc_lookup(struct denode *dep, uint32_t findcn, uint32_t *frcnp, uint32_t *fsrcnp) 278 { 279 int i; 280 uint32_t cn; 281 struct fatcache *closest = 0; 282 283 for (i = 0; i < FC_SIZE; i++) { 284 cn = dep->de_fc[i].fc_frcn; 285 if (cn != FCE_EMPTY && cn <= findcn) { 286 if (closest == 0 || cn > closest->fc_frcn) 287 closest = &dep->de_fc[i]; 288 } 289 } 290 if (closest) { 291 *frcnp = closest->fc_frcn; 292 *fsrcnp = closest->fc_fsrcn; 293 } 294 } 295 296 /* 297 * Purge the fat cache in denode dep of all entries relating to file 298 * relative cluster frcn and beyond. 299 */ 300 void 301 fc_purge(struct denode *dep, u_int frcn) 302 { 303 int i; 304 struct fatcache *fcp; 305 306 fcp = dep->de_fc; 307 for (i = 0; i < FC_SIZE; i++, fcp++) { 308 if (fcp->fc_frcn >= frcn) 309 fcp->fc_frcn = FCE_EMPTY; 310 } 311 } 312 313 /* 314 * Update the fat. 315 * If mirroring the fat, update all copies, with the first copy as last. 316 * Else update only the current fat (ignoring the others). 317 * 318 * pmp - msdosfsmount structure for filesystem to update 319 * bp - addr of modified fat block 320 * fatbn - block number relative to begin of filesystem of the modified fat block. 321 */ 322 void 323 updatefats(struct msdosfsmount *pmp, struct buf *bp, uint32_t fatbn) 324 { 325 int i; 326 struct buf *bpn; 327 328 #ifdef MSDOSFS_DEBUG 329 printf("updatefats(pmp %p, buf %p, fatbn %d)\n", pmp, bp, fatbn); 330 #endif 331 332 /* 333 * If we have an FSInfo block, update it. 334 */ 335 if (pmp->pm_fsinfo) { 336 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), 337 &bpn) != 0) { 338 /* 339 * Ignore the error, but turn off FSInfo update for the future. 340 */ 341 pmp->pm_fsinfo = 0; 342 brelse(bpn); 343 } else { 344 struct fsinfo *fp = (struct fsinfo *)bpn->b_data; 345 346 putulong(fp->fsinfree, pmp->pm_freeclustercount); 347 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 348 bwrite(bpn); 349 else 350 bdwrite(bpn); 351 } 352 } 353 354 if (pmp->pm_flags & MSDOSFS_FATMIRROR) { 355 /* 356 * Now copy the block(s) of the modified fat to the other copies of 357 * the fat and write them out. This is faster than reading in the 358 * other fats and then writing them back out. This could tie up 359 * the fat for quite a while. Preventing others from accessing it. 360 * To prevent us from going after the fat quite so much we use 361 * delayed writes, unless they specified "synchronous" when the 362 * filesystem was mounted. If synch is asked for then use 363 * bwrite()'s and really slow things down. 364 */ 365 for (i = 1; i < pmp->pm_FATs; i++) { 366 fatbn += pmp->pm_FATsecs; 367 /* getblk() never fails */ 368 bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 369 INFSLP); 370 bcopy(bp->b_data, bpn->b_data, bp->b_bcount); 371 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 372 bwrite(bpn); 373 else 374 bdwrite(bpn); 375 } 376 } 377 378 /* 379 * Write out the first (or current) fat last. 380 */ 381 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT) 382 bwrite(bp); 383 else 384 bdwrite(bp); 385 /* 386 * Maybe update fsinfo sector here? 387 */ 388 } 389 390 /* 391 * Updating entries in 12 bit fats is a pain in the butt. 392 * 393 * The following picture shows where nibbles go when moving from a 12 bit 394 * cluster number into the appropriate bytes in the FAT. 395 * 396 * byte m byte m+1 byte m+2 397 * +----+----+ +----+----+ +----+----+ 398 * | 0 1 | | 2 3 | | 4 5 | FAT bytes 399 * +----+----+ +----+----+ +----+----+ 400 * 401 * +----+----+----+ +----+----+----+ 402 * | 3 0 1 | | 4 5 2 | 403 * +----+----+----+ +----+----+----+ 404 * cluster n cluster n+1 405 * 406 * Where n is even. m = n + (n >> 2) 407 * 408 */ 409 static __inline void 410 usemap_alloc(struct msdosfsmount *pmp, uint32_t cn) 411 { 412 413 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS); 414 pmp->pm_freeclustercount--; 415 } 416 417 static __inline void 418 usemap_free(struct msdosfsmount *pmp, uint32_t cn) 419 { 420 421 pmp->pm_freeclustercount++; 422 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS)); 423 } 424 425 int 426 clusterfree(struct msdosfsmount *pmp, uint32_t cluster, uint32_t *oldcnp) 427 { 428 int error; 429 uint32_t oldcn; 430 431 usemap_free(pmp, cluster); 432 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE); 433 if (error) { 434 usemap_alloc(pmp, cluster); 435 return (error); 436 } 437 /* 438 * If the cluster was successfully marked free, then update 439 * the count of free clusters, and turn off the "allocated" 440 * bit in the "in use" cluster bit map. 441 */ 442 if (oldcnp) 443 *oldcnp = oldcn; 444 return (0); 445 } 446 447 /* 448 * Get or Set or 'Get and Set' the cluster'th entry in the fat. 449 * 450 * function - whether to get or set a fat entry 451 * pmp - address of the msdosfsmount structure for the filesystem 452 * whose fat is to be manipulated. 453 * cn - which cluster is of interest 454 * oldcontents - address of a word that is to receive the contents of the 455 * cluster'th entry if this is a get function 456 * newcontents - the new value to be written into the cluster'th element of 457 * the fat if this is a set function. 458 * 459 * This function can also be used to free a cluster by setting the fat entry 460 * for a cluster to 0. 461 * 462 * All copies of the fat are updated if this is a set function. NOTE: If 463 * fatentry() marks a cluster as free it does not update the inusemap in 464 * the msdosfsmount structure. This is left to the caller. 465 */ 466 int 467 fatentry(int function, struct msdosfsmount *pmp, uint32_t cn, uint32_t *oldcontents, 468 uint32_t newcontents) 469 { 470 int error; 471 uint32_t readcn; 472 uint32_t bn, bo, bsize, byteoffset; 473 struct buf *bp; 474 475 #ifdef MSDOSFS_DEBUG 476 printf("fatentry(func %d, pmp %p, clust %d, oldcon %p, " 477 "newcon %d)\n", function, pmp, cn, oldcontents, newcontents); 478 #endif 479 480 #ifdef DIAGNOSTIC 481 /* 482 * Be sure they asked us to do something. 483 */ 484 if ((function & (FAT_SET | FAT_GET)) == 0) { 485 printf("fatentry(): function code doesn't specify get or set\n"); 486 return (EINVAL); 487 } 488 489 /* 490 * If they asked us to return a cluster number but didn't tell us 491 * where to put it, give them an error. 492 */ 493 if ((function & FAT_GET) && oldcontents == NULL) { 494 printf("fatentry(): get function with no place to put result\n"); 495 return (EINVAL); 496 } 497 #endif 498 499 /* 500 * Be sure the requested cluster is in the filesystem. 501 */ 502 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster) 503 return (EINVAL); 504 505 byteoffset = FATOFS(pmp, cn); 506 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 507 if ((error = bread(pmp->pm_devvp, bn, bsize, &bp)) != 0) { 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, uint32_t start, uint32_t count, uint32_t fillwith) 571 { 572 int error; 573 uint32_t bn, bo, bsize, byteoffset, readcn, newc; 574 struct buf *bp; 575 576 #ifdef MSDOSFS_DEBUG 577 printf("fatchain(pmp %p, start %d, count %d, fillwith %d)\n", 578 pmp, start, count, fillwith); 579 #endif 580 /* 581 * Be sure the clusters are in the filesystem. 582 */ 583 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster) 584 return (EINVAL); 585 586 while (count > 0) { 587 byteoffset = FATOFS(pmp, start); 588 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 589 error = bread(pmp->pm_devvp, bn, bsize, &bp); 590 if (error) { 591 brelse(bp); 592 return (error); 593 } 594 while (count > 0) { 595 start++; 596 newc = --count > 0 ? start : fillwith; 597 switch (pmp->pm_fatmask) { 598 case FAT12_MASK: 599 readcn = getushort(&bp->b_data[bo]); 600 if (start & 1) { 601 readcn &= 0xf000; 602 readcn |= newc & 0xfff; 603 } else { 604 readcn &= 0x000f; 605 readcn |= newc << 4; 606 } 607 putushort(&bp->b_data[bo], readcn); 608 bo++; 609 if (!(start & 1)) 610 bo++; 611 break; 612 case FAT16_MASK: 613 putushort(&bp->b_data[bo], newc); 614 bo += 2; 615 break; 616 case FAT32_MASK: 617 readcn = getulong(&bp->b_data[bo]); 618 readcn &= ~pmp->pm_fatmask; 619 readcn |= newc & pmp->pm_fatmask; 620 putulong(&bp->b_data[bo], readcn); 621 bo += 4; 622 break; 623 } 624 if (bo >= bsize) 625 break; 626 } 627 updatefats(pmp, bp, bn); 628 } 629 pmp->pm_fmod = 1; 630 return (0); 631 } 632 633 /* 634 * Check the length of a free cluster chain starting at start. 635 * 636 * pmp - mount point 637 * start - start of chain 638 * count - maximum interesting length 639 */ 640 int 641 chainlength(struct msdosfsmount *pmp, uint32_t start, uint32_t count) 642 { 643 uint32_t idx, max_idx; 644 u_int map; 645 uint32_t len; 646 647 max_idx = pmp->pm_maxcluster / N_INUSEBITS; 648 idx = start / N_INUSEBITS; 649 start %= N_INUSEBITS; 650 map = pmp->pm_inusemap[idx]; 651 map &= ~((1 << start) - 1); 652 if (map) { 653 len = ffs(map) - 1 - start; 654 return (len > count ? count : len); 655 } 656 len = N_INUSEBITS - start; 657 if (len >= count) 658 return (count); 659 while (++idx <= max_idx) { 660 if (len >= count) 661 break; 662 if ((map = pmp->pm_inusemap[idx]) != 0) { 663 len += ffs(map) - 1; 664 break; 665 } 666 len += N_INUSEBITS; 667 } 668 return (len > count ? count : len); 669 } 670 671 /* 672 * Allocate contiguous 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 int 683 chainalloc(struct msdosfsmount *pmp, uint32_t start, uint32_t count, 684 uint32_t fillwith, uint32_t *retcluster, uint32_t *got) 685 { 686 int error; 687 uint32_t cl, n; 688 689 for (cl = start, n = count; n-- > 0;) 690 usemap_alloc(pmp, cl++); 691 if ((error = fatchain(pmp, start, count, fillwith)) != 0) 692 return (error); 693 #ifdef MSDOSFS_DEBUG 694 printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n", 695 start, count); 696 #endif 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, uint32_t start, uint32_t count, 717 uint32_t *retcluster, uint32_t *got) 718 { 719 uint32_t idx; 720 uint32_t len, newst, foundl, cn, l; 721 uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */ 722 uint32_t fillwith = CLUST_EOFE; 723 u_int map; 724 725 #ifdef MSDOSFS_DEBUG 726 printf("clusteralloc(): find %d clusters\n",count); 727 #endif 728 if (start) { 729 if ((len = chainlength(pmp, start, count)) >= count) 730 return (chainalloc(pmp, start, count, fillwith, retcluster, got)); 731 } else { 732 /* 733 * This is a new file, initialize start 734 */ 735 struct timeval tv; 736 737 microtime(&tv); 738 start = (tv.tv_usec >> 10) | tv.tv_usec; 739 len = 0; 740 } 741 742 /* 743 * Start at a (pseudo) random place to maximize cluster runs 744 * under multiple writers. 745 */ 746 newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1); 747 foundl = 0; 748 749 for (cn = newst; cn <= pmp->pm_maxcluster;) { 750 idx = cn / N_INUSEBITS; 751 map = pmp->pm_inusemap[idx]; 752 map |= (1 << (cn % N_INUSEBITS)) - 1; 753 if (map != (u_int)-1) { 754 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 755 if ((l = chainlength(pmp, cn, count)) >= count) 756 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 757 if (l > foundl) { 758 foundcn = cn; 759 foundl = l; 760 } 761 cn += l + 1; 762 continue; 763 } 764 cn += N_INUSEBITS - cn % N_INUSEBITS; 765 } 766 for (cn = 0; cn < newst;) { 767 idx = cn / N_INUSEBITS; 768 map = pmp->pm_inusemap[idx]; 769 map |= (1 << (cn % N_INUSEBITS)) - 1; 770 if (map != (u_int)-1) { 771 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1; 772 if ((l = chainlength(pmp, cn, count)) >= count) 773 return (chainalloc(pmp, cn, count, fillwith, retcluster, got)); 774 if (l > foundl) { 775 foundcn = cn; 776 foundl = l; 777 } 778 cn += l + 1; 779 continue; 780 } 781 cn += N_INUSEBITS - cn % N_INUSEBITS; 782 } 783 784 if (!foundl) 785 return (ENOSPC); 786 787 if (len) 788 return (chainalloc(pmp, start, len, fillwith, retcluster, got)); 789 else 790 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got)); 791 } 792 793 794 /* 795 * Free a chain of clusters. 796 * 797 * pmp - address of the msdosfs mount structure for the filesystem 798 * containing the cluster chain to be freed. 799 * startcluster - number of the 1st cluster in the chain of clusters to be 800 * freed. 801 */ 802 int 803 freeclusterchain(struct msdosfsmount *pmp, uint32_t cluster) 804 { 805 int error; 806 struct buf *bp = NULL; 807 uint32_t bn, bo, bsize, byteoffset; 808 uint32_t readcn, lbn = -1; 809 810 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) { 811 byteoffset = FATOFS(pmp, cluster); 812 fatblock(pmp, byteoffset, &bn, &bsize, &bo); 813 if (lbn != bn) { 814 if (bp) 815 updatefats(pmp, bp, lbn); 816 error = bread(pmp->pm_devvp, bn, bsize, &bp); 817 if (error) { 818 brelse(bp); 819 return (error); 820 } 821 lbn = bn; 822 } 823 usemap_free(pmp, cluster); 824 switch (pmp->pm_fatmask) { 825 case FAT12_MASK: 826 readcn = getushort(&bp->b_data[bo]); 827 if (cluster & 1) { 828 cluster = readcn >> 4; 829 readcn &= 0x000f; 830 readcn |= MSDOSFSFREE << 4; 831 } else { 832 cluster = readcn; 833 readcn &= 0xf000; 834 readcn |= MSDOSFSFREE & 0xfff; 835 } 836 putushort(&bp->b_data[bo], readcn); 837 break; 838 case FAT16_MASK: 839 cluster = getushort(&bp->b_data[bo]); 840 putushort(&bp->b_data[bo], MSDOSFSFREE); 841 break; 842 case FAT32_MASK: 843 cluster = getulong(&bp->b_data[bo]); 844 putulong(&bp->b_data[bo], 845 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK)); 846 break; 847 } 848 cluster &= pmp->pm_fatmask; 849 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD) 850 cluster |= pmp->pm_fatmask; 851 } 852 if (bp) 853 updatefats(pmp, bp, bn); 854 return (0); 855 } 856 857 /* 858 * Read in fat blocks looking for free clusters. For every free cluster 859 * found turn off its corresponding bit in the pm_inusemap. 860 */ 861 int 862 fillinusemap(struct msdosfsmount *pmp) 863 { 864 struct buf *bp = NULL; 865 uint32_t cn, readcn; 866 int error; 867 uint32_t bn, bo, bsize, byteoffset; 868 869 /* 870 * Mark all clusters in use, we mark the free ones in the fat scan 871 * loop further down. 872 */ 873 for (cn = 0; cn < howmany(pmp->pm_maxcluster + 1, N_INUSEBITS); cn++) 874 pmp->pm_inusemap[cn] = (u_int)-1; 875 876 /* 877 * Figure how many free clusters are in the filesystem by ripping 878 * through the fat counting the number of entries whose content is 879 * zero. These represent free clusters. 880 */ 881 pmp->pm_freeclustercount = 0; 882 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) { 883 byteoffset = FATOFS(pmp, cn); 884 bo = byteoffset % pmp->pm_fatblocksize; 885 if (!bo || !bp) { 886 /* Read new FAT block */ 887 if (bp) 888 brelse(bp); 889 fatblock(pmp, byteoffset, &bn, &bsize, NULL); 890 error = bread(pmp->pm_devvp, bn, bsize, &bp); 891 if (error) { 892 brelse(bp); 893 return (error); 894 } 895 } 896 if (FAT32(pmp)) 897 readcn = getulong(&bp->b_data[bo]); 898 else 899 readcn = getushort(&bp->b_data[bo]); 900 if (FAT12(pmp) && (cn & 1)) 901 readcn >>= 4; 902 readcn &= pmp->pm_fatmask; 903 904 if (readcn == 0) 905 usemap_free(pmp, cn); 906 } 907 brelse(bp); 908 return (0); 909 } 910 911 /* 912 * Allocate a new cluster and chain it onto the end of the file. 913 * 914 * dep - the file to extend 915 * count - number of clusters to allocate 916 * bpp - where to return the address of the buf header for the first new 917 * file block 918 * ncp - where to put cluster number of the first newly allocated cluster 919 * If this pointer is 0, do not return the cluster number. 920 * flags - see fat.h 921 * 922 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of 923 * the de_flag field of the denode and it does not change the de_FileSize 924 * field. This is left for the caller to do. 925 */ 926 int 927 extendfile(struct denode *dep, uint32_t count, struct buf **bpp, uint32_t *ncp, 928 int flags) 929 { 930 int error; 931 uint32_t frcn; 932 uint32_t cn, got; 933 struct msdosfsmount *pmp = dep->de_pmp; 934 struct buf *bp; 935 936 /* 937 * Don't try to extend the root directory 938 */ 939 if (dep->de_StartCluster == MSDOSFSROOT 940 && (dep->de_Attributes & ATTR_DIRECTORY)) { 941 printf("extendfile(): attempt to extend root directory\n"); 942 return (ENOSPC); 943 } 944 945 /* 946 * If the "file's last cluster" cache entry is empty, and the file 947 * is not empty, then fill the cache entry by calling pcbmap(). 948 */ 949 fc_fileextends++; 950 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY && 951 dep->de_StartCluster != 0) { 952 fc_lfcempty++; 953 error = pcbmap(dep, CLUST_END, 0, &cn, 0); 954 /* we expect it to return E2BIG */ 955 if (error != E2BIG) 956 return (error); 957 } 958 959 /* 960 * Preserve value for the last cluster before extending the file 961 * to speed up further lookups. 962 */ 963 fc_setcache(dep, FC_OLASTFC, dep->de_fc[FC_LASTFC].fc_frcn, 964 dep->de_fc[FC_LASTFC].fc_fsrcn); 965 966 while (count > 0) { 967 /* 968 * Allocate a new cluster chain and cat onto the end of the 969 * file. * If the file is empty we make de_StartCluster point 970 * to the new block. Note that de_StartCluster being 0 is 971 * sufficient to be sure the file is empty since we exclude 972 * attempts to extend the root directory above, and the root 973 * dir is the only file with a startcluster of 0 that has 974 * blocks allocated (sort of). 975 */ 976 if (dep->de_StartCluster == 0) 977 cn = 0; 978 else 979 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1; 980 error = clusteralloc(pmp, cn, count, &cn, &got); 981 if (error) 982 return (error); 983 984 count -= got; 985 986 /* 987 * Give them the filesystem relative cluster number if they want 988 * it. 989 */ 990 if (ncp) { 991 *ncp = cn; 992 ncp = NULL; 993 } 994 995 if (dep->de_StartCluster == 0) { 996 dep->de_StartCluster = cn; 997 frcn = 0; 998 } else { 999 error = fatentry(FAT_SET, pmp, 1000 dep->de_fc[FC_LASTFC].fc_fsrcn, 1001 0, cn); 1002 if (error) { 1003 clusterfree(pmp, cn, NULL); 1004 return (error); 1005 } 1006 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1; 1007 } 1008 1009 /* 1010 * Update the "last cluster of the file" entry in the denode's fat 1011 * cache. 1012 */ 1013 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1); 1014 1015 if (flags & DE_CLEAR) { 1016 while (got-- > 0) { 1017 /* 1018 * Get the buf header for the new block of the file. 1019 */ 1020 if (dep->de_Attributes & ATTR_DIRECTORY) 1021 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++), 1022 pmp->pm_bpcluster, 0, INFSLP); 1023 else { 1024 bp = getblk(DETOV(dep), frcn++, 1025 pmp->pm_bpcluster, 0, INFSLP); 1026 /* 1027 * Do the bmap now, as in msdosfs_write 1028 */ 1029 if (pcbmap(dep, bp->b_lblkno, &bp->b_blkno, 0, 0)) 1030 bp->b_blkno = -1; 1031 if (bp->b_blkno == -1) 1032 panic("extendfile: pcbmap"); 1033 } 1034 clrbuf(bp); 1035 if (bpp) { 1036 *bpp = bp; 1037 bpp = NULL; 1038 } else 1039 bdwrite(bp); 1040 } 1041 } 1042 } 1043 1044 return (0); 1045 }
Cache object: 28479507d97ccb83974079c1e87046aa
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