Annotation of sys/msdosfs/msdosfs_fat.c, Revision 1.1
1.1 ! nbrk 1: /* $OpenBSD: msdosfs_fat.c,v 1.19 2006/12/16 12:44:05 krw 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/file.h>
! 58: #include <sys/namei.h>
! 59: #include <sys/mount.h> /* to define statfs structure */
! 60: #include <sys/vnode.h> /* to define vattr structure */
! 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(pmp, ofs, bnp, sizep, bop)
! 98: struct msdosfsmount *pmp;
! 99: uint32_t ofs;
! 100: uint32_t *bnp;
! 101: uint32_t *sizep;
! 102: uint32_t *bop;
! 103: {
! 104: uint32_t bn, size;
! 105:
! 106: bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
! 107: size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn) * DEV_BSIZE;
! 108: bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
! 109:
! 110: if (bnp)
! 111: *bnp = bn;
! 112: if (sizep)
! 113: *sizep = size;
! 114: if (bop)
! 115: *bop = ofs % pmp->pm_fatblocksize;
! 116: }
! 117:
! 118: /*
! 119: * Map the logical cluster number of a file into a physical disk sector
! 120: * that is filesystem relative.
! 121: *
! 122: * dep - address of denode representing the file of interest
! 123: * findcn - file relative cluster whose filesystem relative cluster number
! 124: * and/or block number are/is to be found
! 125: * bnp - address of where to place the file system relative block number.
! 126: * If this pointer is null then don't return this quantity.
! 127: * cnp - address of where to place the file system relative cluster number.
! 128: * If this pointer is null then don't return this quantity.
! 129: *
! 130: * NOTE: Either bnp or cnp must be non-null.
! 131: * This function has one side effect. If the requested file relative cluster
! 132: * is beyond the end of file, then the actual number of clusters in the file
! 133: * is returned in *cnp. This is useful for determining how long a directory is.
! 134: * If cnp is null, nothing is returned.
! 135: */
! 136: int
! 137: pcbmap(dep, findcn, bnp, cnp, sp)
! 138: struct denode *dep;
! 139: uint32_t findcn; /* file relative cluster to get */
! 140: daddr64_t *bnp; /* returned filesys relative blk number */
! 141: uint32_t *cnp; /* returned cluster number */
! 142: int *sp; /* returned block size */
! 143: {
! 144: int error;
! 145: uint32_t i;
! 146: uint32_t cn;
! 147: uint32_t prevcn = 0; /* XXX: prevcn could be used uninitialized */
! 148: uint32_t byteoffset;
! 149: uint32_t bn;
! 150: uint32_t bo;
! 151: struct buf *bp = NULL;
! 152: uint32_t bp_bn = -1;
! 153: struct msdosfsmount *pmp = dep->de_pmp;
! 154: uint32_t bsize;
! 155:
! 156: fc_bmapcalls++;
! 157:
! 158: /*
! 159: * If they don't give us someplace to return a value then don't
! 160: * bother doing anything.
! 161: */
! 162: if (bnp == NULL && cnp == NULL && sp == NULL)
! 163: return (0);
! 164:
! 165: cn = dep->de_StartCluster;
! 166: /*
! 167: * The "file" that makes up the root directory is contiguous,
! 168: * permanently allocated, of fixed size, and is not made up of
! 169: * clusters. If the cluster number is beyond the end of the root
! 170: * directory, then return the number of clusters in the file.
! 171: */
! 172: if (cn == MSDOSFSROOT) {
! 173: if (dep->de_Attributes & ATTR_DIRECTORY) {
! 174: if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
! 175: if (cnp)
! 176: *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
! 177: return (E2BIG);
! 178: }
! 179: if (bnp)
! 180: *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
! 181: if (cnp)
! 182: *cnp = MSDOSFSROOT;
! 183: if (sp)
! 184: *sp = min(pmp->pm_bpcluster,
! 185: dep->de_FileSize - de_cn2off(pmp, findcn));
! 186: return (0);
! 187: } else { /* just an empty file */
! 188: if (cnp)
! 189: *cnp = 0;
! 190: return (E2BIG);
! 191: }
! 192: }
! 193:
! 194: /*
! 195: * All other files do I/O in cluster sized blocks
! 196: */
! 197: if (sp)
! 198: *sp = pmp->pm_bpcluster;
! 199:
! 200: /*
! 201: * Rummage around in the fat cache, maybe we can avoid tromping
! 202: * thru every fat entry for the file. And, keep track of how far
! 203: * off the cache was from where we wanted to be.
! 204: */
! 205: i = 0;
! 206: fc_lookup(dep, findcn, &i, &cn);
! 207: if ((bn = findcn - i) >= LMMAX)
! 208: fc_largedistance++;
! 209: else
! 210: fc_lmdistance[bn]++;
! 211:
! 212: /*
! 213: * Handle all other files or directories the normal way.
! 214: */
! 215: for (; i < findcn; i++) {
! 216: /*
! 217: * Stop with all reserved clusters, not just with EOF.
! 218: */
! 219: if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
! 220: goto hiteof;
! 221: byteoffset = FATOFS(pmp, cn);
! 222: fatblock(pmp, byteoffset, &bn, &bsize, &bo);
! 223: if (bn != bp_bn) {
! 224: if (bp)
! 225: brelse(bp);
! 226: error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
! 227: if (error) {
! 228: brelse(bp);
! 229: return (error);
! 230: }
! 231: bp_bn = bn;
! 232: }
! 233: prevcn = cn;
! 234: if (bo >= bsize) {
! 235: if (bp)
! 236: brelse(bp);
! 237: return (EIO);
! 238: }
! 239: if (FAT32(pmp))
! 240: cn = getulong(&bp->b_data[bo]);
! 241: else
! 242: cn = getushort(&bp->b_data[bo]);
! 243: if (FAT12(pmp) && (prevcn & 1))
! 244: cn >>= 4;
! 245: cn &= pmp->pm_fatmask;
! 246:
! 247: /*
! 248: * Force the special cluster numbers
! 249: * to be the same for all cluster sizes
! 250: * to let the rest of msdosfs handle
! 251: * all cases the same.
! 252: */
! 253: if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
! 254: cn |= ~pmp->pm_fatmask;
! 255: }
! 256:
! 257: if (!MSDOSFSEOF(pmp, cn)) {
! 258: if (bp)
! 259: brelse(bp);
! 260: if (bnp)
! 261: *bnp = cntobn(pmp, cn);
! 262: if (cnp)
! 263: *cnp = cn;
! 264: fc_setcache(dep, FC_LASTMAP, i, cn);
! 265: return (0);
! 266: }
! 267:
! 268: hiteof:;
! 269: if (cnp)
! 270: *cnp = i;
! 271: if (bp)
! 272: brelse(bp);
! 273: /* update last file cluster entry in the fat cache */
! 274: fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
! 275: return (E2BIG);
! 276: }
! 277:
! 278: /*
! 279: * Find the closest entry in the fat cache to the cluster we are looking
! 280: * for.
! 281: */
! 282: void
! 283: fc_lookup(dep, findcn, frcnp, fsrcnp)
! 284: struct denode *dep;
! 285: uint32_t findcn;
! 286: uint32_t *frcnp;
! 287: uint32_t *fsrcnp;
! 288: {
! 289: int i;
! 290: uint32_t cn;
! 291: struct fatcache *closest = 0;
! 292:
! 293: for (i = 0; i < FC_SIZE; i++) {
! 294: cn = dep->de_fc[i].fc_frcn;
! 295: if (cn != FCE_EMPTY && cn <= findcn) {
! 296: if (closest == 0 || cn > closest->fc_frcn)
! 297: closest = &dep->de_fc[i];
! 298: }
! 299: }
! 300: if (closest) {
! 301: *frcnp = closest->fc_frcn;
! 302: *fsrcnp = closest->fc_fsrcn;
! 303: }
! 304: }
! 305:
! 306: /*
! 307: * Purge the fat cache in denode dep of all entries relating to file
! 308: * relative cluster frcn and beyond.
! 309: */
! 310: void
! 311: fc_purge(dep, frcn)
! 312: struct denode *dep;
! 313: u_int frcn;
! 314: {
! 315: int i;
! 316: struct fatcache *fcp;
! 317:
! 318: fcp = dep->de_fc;
! 319: for (i = 0; i < FC_SIZE; i++, fcp++) {
! 320: if (fcp->fc_frcn >= frcn)
! 321: fcp->fc_frcn = FCE_EMPTY;
! 322: }
! 323: }
! 324:
! 325: /*
! 326: * Update the fat.
! 327: * If mirroring the fat, update all copies, with the first copy as last.
! 328: * Else update only the current fat (ignoring the others).
! 329: *
! 330: * pmp - msdosfsmount structure for filesystem to update
! 331: * bp - addr of modified fat block
! 332: * fatbn - block number relative to begin of filesystem of the modified fat block.
! 333: */
! 334: void
! 335: updatefats(pmp, bp, fatbn)
! 336: struct msdosfsmount *pmp;
! 337: struct buf *bp;
! 338: uint32_t fatbn;
! 339: {
! 340: int i;
! 341: struct buf *bpn;
! 342:
! 343: #ifdef MSDOSFS_DEBUG
! 344: printf("updatefats(pmp %08, buf %x, fatbn %ld)\n", pmp, bp, fatbn);
! 345: #endif
! 346:
! 347: /*
! 348: * If we have an FSInfo block, update it.
! 349: */
! 350: if (pmp->pm_fsinfo) {
! 351: uint32_t cn = pmp->pm_nxtfree;
! 352:
! 353: if (pmp->pm_freeclustercount
! 354: && (pmp->pm_inusemap[cn / N_INUSEBITS]
! 355: & (1 << (cn % N_INUSEBITS)))) {
! 356: /*
! 357: * The cluster indicated in FSInfo isn't free
! 358: * any longer. Got get a new free one.
! 359: */
! 360: for (cn = 0; cn < pmp->pm_maxcluster; cn++)
! 361: if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
! 362: break;
! 363: pmp->pm_nxtfree = cn
! 364: + ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
! 365: ^ (u_int)-1) - 1;
! 366: }
! 367: if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), NOCRED,
! 368: &bpn) != 0) {
! 369: /*
! 370: * Ignore the error, but turn off FSInfo update for the future.
! 371: */
! 372: pmp->pm_fsinfo = 0;
! 373: brelse(bpn);
! 374: } else {
! 375: struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
! 376:
! 377: putulong(fp->fsinfree, pmp->pm_freeclustercount);
! 378: putulong(fp->fsinxtfree, pmp->pm_nxtfree);
! 379: if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
! 380: bwrite(bpn);
! 381: else
! 382: bdwrite(bpn);
! 383: }
! 384: }
! 385:
! 386: if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
! 387: /*
! 388: * Now copy the block(s) of the modified fat to the other copies of
! 389: * the fat and write them out. This is faster than reading in the
! 390: * other fats and then writing them back out. This could tie up
! 391: * the fat for quite a while. Preventing others from accessing it.
! 392: * To prevent us from going after the fat quite so much we use
! 393: * delayed writes, unless they specfied "synchronous" when the
! 394: * filesystem was mounted. If synch is asked for then use
! 395: * bwrite()'s and really slow things down.
! 396: */
! 397: for (i = 1; i < pmp->pm_FATs; i++) {
! 398: fatbn += pmp->pm_FATsecs;
! 399: /* getblk() never fails */
! 400: bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount, 0, 0);
! 401: bcopy(bp->b_data, bpn->b_data, bp->b_bcount);
! 402: if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
! 403: bwrite(bpn);
! 404: else
! 405: bdwrite(bpn);
! 406: }
! 407: }
! 408:
! 409: /*
! 410: * Write out the first (or current) fat last.
! 411: */
! 412: if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
! 413: bwrite(bp);
! 414: else
! 415: bdwrite(bp);
! 416: /*
! 417: * Maybe update fsinfo sector here?
! 418: */
! 419: }
! 420:
! 421: /*
! 422: * Updating entries in 12 bit fats is a pain in the butt.
! 423: *
! 424: * The following picture shows where nibbles go when moving from a 12 bit
! 425: * cluster number into the appropriate bytes in the FAT.
! 426: *
! 427: * byte m byte m+1 byte m+2
! 428: * +----+----+ +----+----+ +----+----+
! 429: * | 0 1 | | 2 3 | | 4 5 | FAT bytes
! 430: * +----+----+ +----+----+ +----+----+
! 431: *
! 432: * +----+----+----+ +----+----+----+
! 433: * | 3 0 1 | | 4 5 2 |
! 434: * +----+----+----+ +----+----+----+
! 435: * cluster n cluster n+1
! 436: *
! 437: * Where n is even. m = n + (n >> 2)
! 438: *
! 439: */
! 440: static __inline void
! 441: usemap_alloc(pmp, cn)
! 442: struct msdosfsmount *pmp;
! 443: uint32_t cn;
! 444: {
! 445:
! 446: pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
! 447: pmp->pm_freeclustercount--;
! 448: }
! 449:
! 450: static __inline void
! 451: usemap_free(pmp, cn)
! 452: struct msdosfsmount *pmp;
! 453: uint32_t cn;
! 454: {
! 455:
! 456: pmp->pm_freeclustercount++;
! 457: pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
! 458: }
! 459:
! 460: int
! 461: clusterfree(pmp, cluster, oldcnp)
! 462: struct msdosfsmount *pmp;
! 463: uint32_t cluster;
! 464: uint32_t *oldcnp;
! 465: {
! 466: int error;
! 467: uint32_t oldcn;
! 468:
! 469: usemap_free(pmp, cluster);
! 470: error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
! 471: if (error) {
! 472: usemap_alloc(pmp, cluster);
! 473: return (error);
! 474: }
! 475: /*
! 476: * If the cluster was successfully marked free, then update
! 477: * the count of free clusters, and turn off the "allocated"
! 478: * bit in the "in use" cluster bit map.
! 479: */
! 480: if (oldcnp)
! 481: *oldcnp = oldcn;
! 482: return (0);
! 483: }
! 484:
! 485: /*
! 486: * Get or Set or 'Get and Set' the cluster'th entry in the fat.
! 487: *
! 488: * function - whether to get or set a fat entry
! 489: * pmp - address of the msdosfsmount structure for the filesystem
! 490: * whose fat is to be manipulated.
! 491: * cn - which cluster is of interest
! 492: * oldcontents - address of a word that is to receive the contents of the
! 493: * cluster'th entry if this is a get function
! 494: * newcontents - the new value to be written into the cluster'th element of
! 495: * the fat if this is a set function.
! 496: *
! 497: * This function can also be used to free a cluster by setting the fat entry
! 498: * for a cluster to 0.
! 499: *
! 500: * All copies of the fat are updated if this is a set function. NOTE: If
! 501: * fatentry() marks a cluster as free it does not update the inusemap in
! 502: * the msdosfsmount structure. This is left to the caller.
! 503: */
! 504: int
! 505: fatentry(function, pmp, cn, oldcontents, newcontents)
! 506: int function;
! 507: struct msdosfsmount *pmp;
! 508: uint32_t cn;
! 509: uint32_t *oldcontents;
! 510: uint32_t newcontents;
! 511: {
! 512: int error;
! 513: uint32_t readcn;
! 514: uint32_t bn, bo, bsize, byteoffset;
! 515: struct buf *bp;
! 516:
! 517: #ifdef MSDOSFS_DEBUG
! 518: printf("fatentry(func %d, pmp %08x, clust %d, oldcon %08x, newcon %d)\n",
! 519: function, pmp, cn, oldcontents, newcontents);
! 520: #endif
! 521:
! 522: #ifdef DIAGNOSTIC
! 523: /*
! 524: * Be sure they asked us to do something.
! 525: */
! 526: if ((function & (FAT_SET | FAT_GET)) == 0) {
! 527: printf("fatentry(): function code doesn't specify get or set\n");
! 528: return (EINVAL);
! 529: }
! 530:
! 531: /*
! 532: * If they asked us to return a cluster number but didn't tell us
! 533: * where to put it, give them an error.
! 534: */
! 535: if ((function & FAT_GET) && oldcontents == NULL) {
! 536: printf("fatentry(): get function with no place to put result\n");
! 537: return (EINVAL);
! 538: }
! 539: #endif
! 540:
! 541: /*
! 542: * Be sure the requested cluster is in the filesystem.
! 543: */
! 544: if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
! 545: return (EINVAL);
! 546:
! 547: byteoffset = FATOFS(pmp, cn);
! 548: fatblock(pmp, byteoffset, &bn, &bsize, &bo);
! 549: if ((error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp)) != 0) {
! 550: brelse(bp);
! 551: return (error);
! 552: }
! 553:
! 554: if (function & FAT_GET) {
! 555: if (FAT32(pmp))
! 556: readcn = getulong(&bp->b_data[bo]);
! 557: else
! 558: readcn = getushort(&bp->b_data[bo]);
! 559: if (FAT12(pmp) && (cn & 1))
! 560: readcn >>= 4;
! 561: readcn &= pmp->pm_fatmask;
! 562: /* map reserved fat entries to same values for all fats */
! 563: if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
! 564: readcn |= ~pmp->pm_fatmask;
! 565: *oldcontents = readcn;
! 566: }
! 567: if (function & FAT_SET) {
! 568: switch (pmp->pm_fatmask) {
! 569: case FAT12_MASK:
! 570: readcn = getushort(&bp->b_data[bo]);
! 571: if (cn & 1) {
! 572: readcn &= 0x000f;
! 573: readcn |= newcontents << 4;
! 574: } else {
! 575: readcn &= 0xf000;
! 576: readcn |= newcontents & 0xfff;
! 577: }
! 578: putushort(&bp->b_data[bo], readcn);
! 579: break;
! 580: case FAT16_MASK:
! 581: putushort(&bp->b_data[bo], newcontents);
! 582: break;
! 583: case FAT32_MASK:
! 584: /*
! 585: * According to spec we have to retain the
! 586: * high order bits of the fat entry.
! 587: */
! 588: readcn = getulong(&bp->b_data[bo]);
! 589: readcn &= ~FAT32_MASK;
! 590: readcn |= newcontents & FAT32_MASK;
! 591: putulong(&bp->b_data[bo], readcn);
! 592: break;
! 593: }
! 594: updatefats(pmp, bp, bn);
! 595: bp = NULL;
! 596: pmp->pm_fmod = 1;
! 597: }
! 598: if (bp)
! 599: brelse(bp);
! 600: return (0);
! 601: }
! 602:
! 603: /*
! 604: * Update a contiguous cluster chain
! 605: *
! 606: * pmp - mount point
! 607: * start - first cluster of chain
! 608: * count - number of clusters in chain
! 609: * fillwith - what to write into fat entry of last cluster
! 610: */
! 611: static int
! 612: fatchain(pmp, start, count, fillwith)
! 613: struct msdosfsmount *pmp;
! 614: uint32_t start;
! 615: uint32_t count;
! 616: uint32_t fillwith;
! 617: {
! 618: int error;
! 619: uint32_t bn, bo, bsize, byteoffset, readcn, newc;
! 620: struct buf *bp;
! 621:
! 622: #ifdef MSDOSFS_DEBUG
! 623: printf("fatchain(pmp %08x, start %d, count %d, fillwith %d)\n",
! 624: pmp, start, count, fillwith);
! 625: #endif
! 626: /*
! 627: * Be sure the clusters are in the filesystem.
! 628: */
! 629: if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
! 630: return (EINVAL);
! 631:
! 632: while (count > 0) {
! 633: byteoffset = FATOFS(pmp, start);
! 634: fatblock(pmp, byteoffset, &bn, &bsize, &bo);
! 635: error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
! 636: if (error) {
! 637: brelse(bp);
! 638: return (error);
! 639: }
! 640: while (count > 0) {
! 641: start++;
! 642: newc = --count > 0 ? start : fillwith;
! 643: switch (pmp->pm_fatmask) {
! 644: case FAT12_MASK:
! 645: readcn = getushort(&bp->b_data[bo]);
! 646: if (start & 1) {
! 647: readcn &= 0xf000;
! 648: readcn |= newc & 0xfff;
! 649: } else {
! 650: readcn &= 0x000f;
! 651: readcn |= newc << 4;
! 652: }
! 653: putushort(&bp->b_data[bo], readcn);
! 654: bo++;
! 655: if (!(start & 1))
! 656: bo++;
! 657: break;
! 658: case FAT16_MASK:
! 659: putushort(&bp->b_data[bo], newc);
! 660: bo += 2;
! 661: break;
! 662: case FAT32_MASK:
! 663: readcn = getulong(&bp->b_data[bo]);
! 664: readcn &= ~pmp->pm_fatmask;
! 665: readcn |= newc & pmp->pm_fatmask;
! 666: putulong(&bp->b_data[bo], readcn);
! 667: bo += 4;
! 668: break;
! 669: }
! 670: if (bo >= bsize)
! 671: break;
! 672: }
! 673: updatefats(pmp, bp, bn);
! 674: }
! 675: pmp->pm_fmod = 1;
! 676: return (0);
! 677: }
! 678:
! 679: /*
! 680: * Check the length of a free cluster chain starting at start.
! 681: *
! 682: * pmp - mount point
! 683: * start - start of chain
! 684: * count - maximum interesting length
! 685: */
! 686: int
! 687: chainlength(pmp, start, count)
! 688: struct msdosfsmount *pmp;
! 689: uint32_t start;
! 690: uint32_t count;
! 691: {
! 692: uint32_t idx, max_idx;
! 693: u_int map;
! 694: uint32_t len;
! 695:
! 696: max_idx = pmp->pm_maxcluster / N_INUSEBITS;
! 697: idx = start / N_INUSEBITS;
! 698: start %= N_INUSEBITS;
! 699: map = pmp->pm_inusemap[idx];
! 700: map &= ~((1 << start) - 1);
! 701: if (map) {
! 702: len = ffs(map) - 1 - start;
! 703: return (len > count ? count : len);
! 704: }
! 705: len = N_INUSEBITS - start;
! 706: if (len >= count)
! 707: return (count);
! 708: while (++idx <= max_idx) {
! 709: if (len >= count)
! 710: break;
! 711: if ((map = pmp->pm_inusemap[idx]) != 0) {
! 712: len += ffs(map) - 1;
! 713: break;
! 714: }
! 715: len += N_INUSEBITS;
! 716: }
! 717: return (len > count ? count : len);
! 718: }
! 719:
! 720: /*
! 721: * Allocate contigous free clusters.
! 722: *
! 723: * pmp - mount point.
! 724: * start - start of cluster chain.
! 725: * count - number of clusters to allocate.
! 726: * fillwith - put this value into the fat entry for the
! 727: * last allocated cluster.
! 728: * retcluster - put the first allocated cluster's number here.
! 729: * got - how many clusters were actually allocated.
! 730: */
! 731: int
! 732: chainalloc(pmp, start, count, fillwith, retcluster, got)
! 733: struct msdosfsmount *pmp;
! 734: uint32_t start;
! 735: uint32_t count;
! 736: uint32_t fillwith;
! 737: uint32_t *retcluster;
! 738: uint32_t *got;
! 739: {
! 740: int error;
! 741: uint32_t cl, n;
! 742:
! 743: for (cl = start, n = count; n-- > 0;)
! 744: usemap_alloc(pmp, cl++);
! 745: if ((error = fatchain(pmp, start, count, fillwith)) != 0)
! 746: return (error);
! 747: #ifdef MSDOSFS_DEBUG
! 748: printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n",
! 749: start, count);
! 750: #endif
! 751: if (retcluster)
! 752: *retcluster = start;
! 753: if (got)
! 754: *got = count;
! 755: return (0);
! 756: }
! 757:
! 758: /*
! 759: * Allocate contiguous free clusters.
! 760: *
! 761: * pmp - mount point.
! 762: * start - preferred start of cluster chain.
! 763: * count - number of clusters requested.
! 764: * fillwith - put this value into the fat entry for the
! 765: * last allocated cluster.
! 766: * retcluster - put the first allocated cluster's number here.
! 767: * got - how many clusters were actually allocated.
! 768: */
! 769: int
! 770: clusteralloc(pmp, start, count, fillwith, retcluster, got)
! 771: struct msdosfsmount *pmp;
! 772: uint32_t start;
! 773: uint32_t count;
! 774: uint32_t fillwith;
! 775: uint32_t *retcluster;
! 776: uint32_t *got;
! 777: {
! 778: uint32_t idx;
! 779: uint32_t len, newst, foundl, cn, l;
! 780: uint32_t foundcn = 0; /* XXX: foundcn could be used uninitialized */
! 781: u_int map;
! 782:
! 783: #ifdef MSDOSFS_DEBUG
! 784: printf("clusteralloc(): find %d clusters\n",count);
! 785: #endif
! 786: if (start) {
! 787: if ((len = chainlength(pmp, start, count)) >= count)
! 788: return (chainalloc(pmp, start, count, fillwith, retcluster, got));
! 789: } else {
! 790: /*
! 791: * This is a new file, initialize start
! 792: */
! 793: struct timeval tv;
! 794:
! 795: microtime(&tv);
! 796: start = (tv.tv_usec >> 10) | tv.tv_usec;
! 797: len = 0;
! 798: }
! 799:
! 800: /*
! 801: * Start at a (pseudo) random place to maximize cluster runs
! 802: * under multiple writers.
! 803: */
! 804: newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
! 805: foundl = 0;
! 806:
! 807: for (cn = newst; cn <= pmp->pm_maxcluster;) {
! 808: idx = cn / N_INUSEBITS;
! 809: map = pmp->pm_inusemap[idx];
! 810: map |= (1 << (cn % N_INUSEBITS)) - 1;
! 811: if (map != (u_int)-1) {
! 812: cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
! 813: if ((l = chainlength(pmp, cn, count)) >= count)
! 814: return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
! 815: if (l > foundl) {
! 816: foundcn = cn;
! 817: foundl = l;
! 818: }
! 819: cn += l + 1;
! 820: continue;
! 821: }
! 822: cn += N_INUSEBITS - cn % N_INUSEBITS;
! 823: }
! 824: for (cn = 0; cn < newst;) {
! 825: idx = cn / N_INUSEBITS;
! 826: map = pmp->pm_inusemap[idx];
! 827: map |= (1 << (cn % N_INUSEBITS)) - 1;
! 828: if (map != (u_int)-1) {
! 829: cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
! 830: if ((l = chainlength(pmp, cn, count)) >= count)
! 831: return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
! 832: if (l > foundl) {
! 833: foundcn = cn;
! 834: foundl = l;
! 835: }
! 836: cn += l + 1;
! 837: continue;
! 838: }
! 839: cn += N_INUSEBITS - cn % N_INUSEBITS;
! 840: }
! 841:
! 842: if (!foundl)
! 843: return (ENOSPC);
! 844:
! 845: if (len)
! 846: return (chainalloc(pmp, start, len, fillwith, retcluster, got));
! 847: else
! 848: return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
! 849: }
! 850:
! 851:
! 852: /*
! 853: * Free a chain of clusters.
! 854: *
! 855: * pmp - address of the msdosfs mount structure for the filesystem
! 856: * containing the cluster chain to be freed.
! 857: * startcluster - number of the 1st cluster in the chain of clusters to be
! 858: * freed.
! 859: */
! 860: int
! 861: freeclusterchain(pmp, cluster)
! 862: struct msdosfsmount *pmp;
! 863: uint32_t cluster;
! 864: {
! 865: int error;
! 866: struct buf *bp = NULL;
! 867: uint32_t bn, bo, bsize, byteoffset;
! 868: uint32_t readcn, lbn = -1;
! 869:
! 870: while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
! 871: byteoffset = FATOFS(pmp, cluster);
! 872: fatblock(pmp, byteoffset, &bn, &bsize, &bo);
! 873: if (lbn != bn) {
! 874: if (bp)
! 875: updatefats(pmp, bp, lbn);
! 876: error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
! 877: if (error) {
! 878: brelse(bp);
! 879: return (error);
! 880: }
! 881: lbn = bn;
! 882: }
! 883: usemap_free(pmp, cluster);
! 884: switch (pmp->pm_fatmask) {
! 885: case FAT12_MASK:
! 886: readcn = getushort(&bp->b_data[bo]);
! 887: if (cluster & 1) {
! 888: cluster = readcn >> 4;
! 889: readcn &= 0x000f;
! 890: readcn |= MSDOSFSFREE << 4;
! 891: } else {
! 892: cluster = readcn;
! 893: readcn &= 0xf000;
! 894: readcn |= MSDOSFSFREE & 0xfff;
! 895: }
! 896: putushort(&bp->b_data[bo], readcn);
! 897: break;
! 898: case FAT16_MASK:
! 899: cluster = getushort(&bp->b_data[bo]);
! 900: putushort(&bp->b_data[bo], MSDOSFSFREE);
! 901: break;
! 902: case FAT32_MASK:
! 903: cluster = getulong(&bp->b_data[bo]);
! 904: putulong(&bp->b_data[bo],
! 905: (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
! 906: break;
! 907: }
! 908: cluster &= pmp->pm_fatmask;
! 909: if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
! 910: cluster |= pmp->pm_fatmask;
! 911: }
! 912: if (bp)
! 913: updatefats(pmp, bp, bn);
! 914: return (0);
! 915: }
! 916:
! 917: /*
! 918: * Read in fat blocks looking for free clusters. For every free cluster
! 919: * found turn off its corresponding bit in the pm_inusemap.
! 920: */
! 921: int
! 922: fillinusemap(pmp)
! 923: struct msdosfsmount *pmp;
! 924: {
! 925: struct buf *bp = NULL;
! 926: uint32_t cn, readcn;
! 927: int error;
! 928: uint32_t bn, bo, bsize, byteoffset;
! 929:
! 930: /*
! 931: * Mark all clusters in use, we mark the free ones in the fat scan
! 932: * loop further down.
! 933: */
! 934: for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
! 935: pmp->pm_inusemap[cn] = (u_int)-1;
! 936:
! 937: /*
! 938: * Figure how many free clusters are in the filesystem by ripping
! 939: * through the fat counting the number of entries whose content is
! 940: * zero. These represent free clusters.
! 941: */
! 942: pmp->pm_freeclustercount = 0;
! 943: for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
! 944: byteoffset = FATOFS(pmp, cn);
! 945: bo = byteoffset % pmp->pm_fatblocksize;
! 946: if (!bo || !bp) {
! 947: /* Read new FAT block */
! 948: if (bp)
! 949: brelse(bp);
! 950: fatblock(pmp, byteoffset, &bn, &bsize, NULL);
! 951: error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
! 952: if (error) {
! 953: brelse(bp);
! 954: return (error);
! 955: }
! 956: }
! 957: if (FAT32(pmp))
! 958: readcn = getulong(&bp->b_data[bo]);
! 959: else
! 960: readcn = getushort(&bp->b_data[bo]);
! 961: if (FAT12(pmp) && (cn & 1))
! 962: readcn >>= 4;
! 963: readcn &= pmp->pm_fatmask;
! 964:
! 965: if (readcn == 0)
! 966: usemap_free(pmp, cn);
! 967: }
! 968: brelse(bp);
! 969: return (0);
! 970: }
! 971:
! 972: /*
! 973: * Allocate a new cluster and chain it onto the end of the file.
! 974: *
! 975: * dep - the file to extend
! 976: * count - number of clusters to allocate
! 977: * bpp - where to return the address of the buf header for the first new
! 978: * file block
! 979: * ncp - where to put cluster number of the first newly allocated cluster
! 980: * If this pointer is 0, do not return the cluster number.
! 981: * flags - see fat.h
! 982: *
! 983: * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
! 984: * the de_flag field of the denode and it does not change the de_FileSize
! 985: * field. This is left for the caller to do.
! 986: */
! 987: int
! 988: extendfile(dep, count, bpp, ncp, flags)
! 989: struct denode *dep;
! 990: uint32_t count;
! 991: struct buf **bpp;
! 992: uint32_t *ncp;
! 993: int flags;
! 994: {
! 995: int error;
! 996: uint32_t frcn;
! 997: uint32_t cn, got;
! 998: struct msdosfsmount *pmp = dep->de_pmp;
! 999: struct buf *bp;
! 1000:
! 1001: /*
! 1002: * Don't try to extend the root directory
! 1003: */
! 1004: if (dep->de_StartCluster == MSDOSFSROOT
! 1005: && (dep->de_Attributes & ATTR_DIRECTORY)) {
! 1006: printf("extendfile(): attempt to extend root directory\n");
! 1007: return (ENOSPC);
! 1008: }
! 1009:
! 1010: /*
! 1011: * If the "file's last cluster" cache entry is empty, and the file
! 1012: * is not empty, then fill the cache entry by calling pcbmap().
! 1013: */
! 1014: fc_fileextends++;
! 1015: if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
! 1016: dep->de_StartCluster != 0) {
! 1017: fc_lfcempty++;
! 1018: error = pcbmap(dep, 0xffff, 0, &cn, 0);
! 1019: /* we expect it to return E2BIG */
! 1020: if (error != E2BIG)
! 1021: return (error);
! 1022: }
! 1023:
! 1024: while (count > 0) {
! 1025: /*
! 1026: * Allocate a new cluster chain and cat onto the end of the
! 1027: * file. * If the file is empty we make de_StartCluster point
! 1028: * to the new block. Note that de_StartCluster being 0 is
! 1029: * sufficient to be sure the file is empty since we exclude
! 1030: * attempts to extend the root directory above, and the root
! 1031: * dir is the only file with a startcluster of 0 that has
! 1032: * blocks allocated (sort of).
! 1033: */
! 1034: if (dep->de_StartCluster == 0)
! 1035: cn = 0;
! 1036: else
! 1037: cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
! 1038: error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got);
! 1039: if (error)
! 1040: return (error);
! 1041:
! 1042: count -= got;
! 1043:
! 1044: /*
! 1045: * Give them the filesystem relative cluster number if they want
! 1046: * it.
! 1047: */
! 1048: if (ncp) {
! 1049: *ncp = cn;
! 1050: ncp = NULL;
! 1051: }
! 1052:
! 1053: if (dep->de_StartCluster == 0) {
! 1054: dep->de_StartCluster = cn;
! 1055: frcn = 0;
! 1056: } else {
! 1057: error = fatentry(FAT_SET, pmp,
! 1058: dep->de_fc[FC_LASTFC].fc_fsrcn,
! 1059: 0, cn);
! 1060: if (error) {
! 1061: clusterfree(pmp, cn, NULL);
! 1062: return (error);
! 1063: }
! 1064: frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
! 1065: }
! 1066:
! 1067: /*
! 1068: * Update the "last cluster of the file" entry in the denode's fat
! 1069: * cache.
! 1070: */
! 1071: fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
! 1072:
! 1073: if (flags & DE_CLEAR) {
! 1074: while (got-- > 0) {
! 1075: /*
! 1076: * Get the buf header for the new block of the file.
! 1077: */
! 1078: if (dep->de_Attributes & ATTR_DIRECTORY)
! 1079: bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++),
! 1080: pmp->pm_bpcluster, 0, 0);
! 1081: else {
! 1082: bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++),
! 1083: pmp->pm_bpcluster, 0, 0);
! 1084: /*
! 1085: * Do the bmap now, as in msdosfs_write
! 1086: */
! 1087: if (pcbmap(dep,
! 1088: de_bn2cn(pmp, bp->b_lblkno),
! 1089: &bp->b_blkno, 0, 0))
! 1090: bp->b_blkno = -1;
! 1091: if (bp->b_blkno == -1)
! 1092: panic("extendfile: pcbmap");
! 1093: }
! 1094: clrbuf(bp);
! 1095: if (bpp) {
! 1096: *bpp = bp;
! 1097: bpp = NULL;
! 1098: } else
! 1099: bdwrite(bp);
! 1100: }
! 1101: }
! 1102: }
! 1103:
! 1104: return (0);
! 1105: }
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