The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/fs/msdosfs/msdosfs_fat.c

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    1 /* $FreeBSD: releng/8.4/sys/fs/msdosfs/msdosfs_fat.c 247686 2013-03-03 07:27:15Z kib $ */
    2 /*      $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $      */
    3 
    4 /*-
    5  * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
    6  * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
    7  * All rights reserved.
    8  * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. All advertising materials mentioning features or use of this software
   19  *    must display the following acknowledgement:
   20  *      This product includes software developed by TooLs GmbH.
   21  * 4. The name of TooLs GmbH may not be used to endorse or promote products
   22  *    derived from this software without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
   25  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   27  * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   29  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
   30  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   31  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   32  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   33  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   34  */
   35 /*-
   36  * Written by Paul Popelka (paulp@uts.amdahl.com)
   37  *
   38  * You can do anything you want with this software, just don't say you wrote
   39  * it, and don't remove this notice.
   40  *
   41  * This software is provided "as is".
   42  *
   43  * The author supplies this software to be publicly redistributed on the
   44  * understanding that the author is not responsible for the correct
   45  * functioning of this software in any circumstances and is not liable for
   46  * any damages caused by this software.
   47  *
   48  * October 1992
   49  */
   50 
   51 #include <sys/param.h>
   52 #include <sys/systm.h>
   53 #include <sys/buf.h>
   54 #include <sys/mount.h>
   55 #include <sys/vnode.h>
   56 
   57 #include <fs/msdosfs/bpb.h>
   58 #include <fs/msdosfs/direntry.h>
   59 #include <fs/msdosfs/denode.h>
   60 #include <fs/msdosfs/fat.h>
   61 #include <fs/msdosfs/msdosfsmount.h>
   62 
   63 static int      chainalloc(struct msdosfsmount *pmp, u_long start,
   64                     u_long count, u_long fillwith, u_long *retcluster,
   65                     u_long *got);
   66 static int      chainlength(struct msdosfsmount *pmp, u_long start,
   67                     u_long count);
   68 static void     fatblock(struct msdosfsmount *pmp, u_long ofs, u_long *bnp,
   69                     u_long *sizep, u_long *bop);
   70 static int      fatchain(struct msdosfsmount *pmp, u_long start, u_long count,
   71                     u_long fillwith);
   72 static void     fc_lookup(struct denode *dep, u_long findcn, u_long *frcnp,
   73                     u_long *fsrcnp);
   74 static void     updatefats(struct msdosfsmount *pmp, struct buf *bp,
   75                     u_long fatbn);
   76 static __inline void
   77                 usemap_alloc(struct msdosfsmount *pmp, u_long cn);
   78 static __inline void
   79                 usemap_free(struct msdosfsmount *pmp, u_long cn);
   80 static int      clusteralloc1(struct msdosfsmount *pmp, u_long start,
   81                     u_long count, u_long fillwith, u_long *retcluster,
   82                     u_long *got);
   83 
   84 static void
   85 fatblock(pmp, ofs, bnp, sizep, bop)
   86         struct msdosfsmount *pmp;
   87         u_long ofs;
   88         u_long *bnp;
   89         u_long *sizep;
   90         u_long *bop;
   91 {
   92         u_long bn, size;
   93 
   94         bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
   95         size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
   96             * DEV_BSIZE;
   97         bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
   98 
   99         if (bnp)
  100                 *bnp = bn;
  101         if (sizep)
  102                 *sizep = size;
  103         if (bop)
  104                 *bop = ofs % pmp->pm_fatblocksize;
  105 }
  106 
  107 /*
  108  * Map the logical cluster number of a file into a physical disk sector
  109  * that is filesystem relative.
  110  *
  111  * dep    - address of denode representing the file of interest
  112  * findcn - file relative cluster whose filesystem relative cluster number
  113  *          and/or block number are/is to be found
  114  * bnp    - address of where to place the filesystem relative block number.
  115  *          If this pointer is null then don't return this quantity.
  116  * cnp    - address of where to place the filesystem relative cluster number.
  117  *          If this pointer is null then don't return this quantity.
  118  *
  119  * NOTE: Either bnp or cnp must be non-null.
  120  * This function has one side effect.  If the requested file relative cluster
  121  * is beyond the end of file, then the actual number of clusters in the file
  122  * is returned in *cnp.  This is useful for determining how long a directory is.
  123  *  If cnp is null, nothing is returned.
  124  */
  125 int
  126 pcbmap(dep, findcn, bnp, cnp, sp)
  127         struct denode *dep;
  128         u_long findcn;          /* file relative cluster to get          */
  129         daddr_t *bnp;           /* returned filesys relative blk number  */
  130         u_long *cnp;            /* returned cluster number               */
  131         int *sp;                /* returned block size                   */
  132 {
  133         int error;
  134         u_long i;
  135         u_long cn;
  136         u_long prevcn = 0; /* XXX: prevcn could be used unititialized */
  137         u_long byteoffset;
  138         u_long bn;
  139         u_long bo;
  140         struct buf *bp = NULL;
  141         u_long bp_bn = -1;
  142         struct msdosfsmount *pmp = dep->de_pmp;
  143         u_long bsize;
  144 
  145         KASSERT(bnp != NULL || cnp != NULL || sp != NULL,
  146             ("pcbmap: extra call"));
  147         ASSERT_VOP_ELOCKED(DETOV(dep), "pcbmap");
  148 
  149         cn = dep->de_StartCluster;
  150         /*
  151          * The "file" that makes up the root directory is contiguous,
  152          * permanently allocated, of fixed size, and is not made up of
  153          * clusters.  If the cluster number is beyond the end of the root
  154          * directory, then return the number of clusters in the file.
  155          */
  156         if (cn == MSDOSFSROOT) {
  157                 if (dep->de_Attributes & ATTR_DIRECTORY) {
  158                         if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
  159                                 if (cnp)
  160                                         *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
  161                                 return (E2BIG);
  162                         }
  163                         if (bnp)
  164                                 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
  165                         if (cnp)
  166                                 *cnp = MSDOSFSROOT;
  167                         if (sp)
  168                                 *sp = min(pmp->pm_bpcluster,
  169                                     dep->de_FileSize - de_cn2off(pmp, findcn));
  170                         return (0);
  171                 } else {                /* just an empty file */
  172                         if (cnp)
  173                                 *cnp = 0;
  174                         return (E2BIG);
  175                 }
  176         }
  177 
  178         /*
  179          * All other files do I/O in cluster sized blocks
  180          */
  181         if (sp)
  182                 *sp = pmp->pm_bpcluster;
  183 
  184         /*
  185          * Rummage around in the fat cache, maybe we can avoid tromping
  186          * thru every fat entry for the file. And, keep track of how far
  187          * off the cache was from where we wanted to be.
  188          */
  189         i = 0;
  190         fc_lookup(dep, findcn, &i, &cn);
  191 
  192         /*
  193          * Handle all other files or directories the normal way.
  194          */
  195         for (; i < findcn; i++) {
  196                 /*
  197                  * Stop with all reserved clusters, not just with EOF.
  198                  */
  199                 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
  200                         goto hiteof;
  201                 byteoffset = FATOFS(pmp, cn);
  202                 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
  203                 if (bn != bp_bn) {
  204                         if (bp)
  205                                 brelse(bp);
  206                         error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
  207                         if (error) {
  208                                 brelse(bp);
  209                                 return (error);
  210                         }
  211                         bp_bn = bn;
  212                 }
  213                 prevcn = cn;
  214                 if (bo >= bsize) {
  215                         if (bp)
  216                                 brelse(bp);
  217                         return (EIO);
  218                 }
  219                 if (FAT32(pmp))
  220                         cn = getulong(&bp->b_data[bo]);
  221                 else
  222                         cn = getushort(&bp->b_data[bo]);
  223                 if (FAT12(pmp) && (prevcn & 1))
  224                         cn >>= 4;
  225                 cn &= pmp->pm_fatmask;
  226 
  227                 /*
  228                  * Force the special cluster numbers
  229                  * to be the same for all cluster sizes
  230                  * to let the rest of msdosfs handle
  231                  * all cases the same.
  232                  */
  233                 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
  234                         cn |= ~pmp->pm_fatmask;
  235         }
  236 
  237         if (!MSDOSFSEOF(pmp, cn)) {
  238                 if (bp)
  239                         brelse(bp);
  240                 if (bnp)
  241                         *bnp = cntobn(pmp, cn);
  242                 if (cnp)
  243                         *cnp = cn;
  244                 fc_setcache(dep, FC_LASTMAP, i, cn);
  245                 return (0);
  246         }
  247 
  248 hiteof:;
  249         if (cnp)
  250                 *cnp = i;
  251         if (bp)
  252                 brelse(bp);
  253         /* update last file cluster entry in the fat cache */
  254         fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
  255         return (E2BIG);
  256 }
  257 
  258 /*
  259  * Find the closest entry in the fat cache to the cluster we are looking
  260  * for.
  261  */
  262 static void
  263 fc_lookup(dep, findcn, frcnp, fsrcnp)
  264         struct denode *dep;
  265         u_long findcn;
  266         u_long *frcnp;
  267         u_long *fsrcnp;
  268 {
  269         int i;
  270         u_long cn;
  271         struct fatcache *closest = 0;
  272 
  273         ASSERT_VOP_LOCKED(DETOV(dep), "fc_lookup");
  274 
  275         for (i = 0; i < FC_SIZE; i++) {
  276                 cn = dep->de_fc[i].fc_frcn;
  277                 if (cn != FCE_EMPTY && cn <= findcn) {
  278                         if (closest == 0 || cn > closest->fc_frcn)
  279                                 closest = &dep->de_fc[i];
  280                 }
  281         }
  282         if (closest) {
  283                 *frcnp = closest->fc_frcn;
  284                 *fsrcnp = closest->fc_fsrcn;
  285         }
  286 }
  287 
  288 /*
  289  * Purge the fat cache in denode dep of all entries relating to file
  290  * relative cluster frcn and beyond.
  291  */
  292 void
  293 fc_purge(dep, frcn)
  294         struct denode *dep;
  295         u_int frcn;
  296 {
  297         int i;
  298         struct fatcache *fcp;
  299 
  300         ASSERT_VOP_ELOCKED(DETOV(dep), "fc_purge");
  301 
  302         fcp = dep->de_fc;
  303         for (i = 0; i < FC_SIZE; i++, fcp++) {
  304                 if (fcp->fc_frcn >= frcn)
  305                         fcp->fc_frcn = FCE_EMPTY;
  306         }
  307 }
  308 
  309 /*
  310  * Update the fat.
  311  * If mirroring the fat, update all copies, with the first copy as last.
  312  * Else update only the current fat (ignoring the others).
  313  *
  314  * pmp   - msdosfsmount structure for filesystem to update
  315  * bp    - addr of modified fat block
  316  * fatbn - block number relative to begin of filesystem of the modified fat block.
  317  */
  318 static void
  319 updatefats(pmp, bp, fatbn)
  320         struct msdosfsmount *pmp;
  321         struct buf *bp;
  322         u_long fatbn;
  323 {
  324         struct buf *bpn;
  325         int cleanfat, i;
  326 
  327 #ifdef MSDOSFS_DEBUG
  328         printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn);
  329 #endif
  330 
  331         if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
  332                 /*
  333                  * Now copy the block(s) of the modified fat to the other copies of
  334                  * the fat and write them out.  This is faster than reading in the
  335                  * other fats and then writing them back out.  This could tie up
  336                  * the fat for quite a while. Preventing others from accessing it.
  337                  * To prevent us from going after the fat quite so much we use
  338                  * delayed writes, unless they specfied "synchronous" when the
  339                  * filesystem was mounted.  If synch is asked for then use
  340                  * bwrite()'s and really slow things down.
  341                  */
  342                 if (fatbn != pmp->pm_fatblk || FAT12(pmp))
  343                         cleanfat = 0;
  344                 else if (FAT16(pmp))
  345                         cleanfat = 16;
  346                 else
  347                         cleanfat = 32;
  348                 for (i = 1; i < pmp->pm_FATs; i++) {
  349                         fatbn += pmp->pm_FATsecs;
  350                         /* getblk() never fails */
  351                         bpn = getblk(pmp->pm_devvp, fatbn, bp->b_bcount,
  352                             0, 0, 0);
  353                         bcopy(bp->b_data, bpn->b_data, bp->b_bcount);
  354                         /* Force the clean bit on in the other copies. */
  355                         if (cleanfat == 16)
  356                                 ((u_int8_t *)bpn->b_data)[3] |= 0x80;
  357                         else if (cleanfat == 32)
  358                                 ((u_int8_t *)bpn->b_data)[7] |= 0x08;
  359                         if (pmp->pm_mountp->mnt_flag & MNT_SYNCHRONOUS)
  360                                 bwrite(bpn);
  361                         else
  362                                 bdwrite(bpn);
  363                 }
  364         }
  365 
  366         /*
  367          * Write out the first (or current) fat last.
  368          */
  369         if (pmp->pm_mountp->mnt_flag & MNT_SYNCHRONOUS)
  370                 bwrite(bp);
  371         else
  372                 bdwrite(bp);
  373 }
  374 
  375 /*
  376  * Updating entries in 12 bit fats is a pain in the butt.
  377  *
  378  * The following picture shows where nibbles go when moving from a 12 bit
  379  * cluster number into the appropriate bytes in the FAT.
  380  *
  381  *      byte m        byte m+1      byte m+2
  382  *      +----+----+   +----+----+   +----+----+
  383  *      |  0    1 |   |  2    3 |   |  4    5 |   FAT bytes
  384  *      +----+----+   +----+----+   +----+----+
  385  *
  386  *      +----+----+----+   +----+----+----+
  387  *      |  3    0    1 |   |  4    5    2 |
  388  *      +----+----+----+   +----+----+----+
  389  *      cluster n          cluster n+1
  390  *
  391  * Where n is even. m = n + (n >> 2)
  392  *
  393  */
  394 static __inline void
  395 usemap_alloc(pmp, cn)
  396         struct msdosfsmount *pmp;
  397         u_long cn;
  398 {
  399 
  400         MSDOSFS_ASSERT_MP_LOCKED(pmp);
  401 
  402         KASSERT((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
  403             == 0, ("Allocating used sector %ld %ld %x", cn, cn % N_INUSEBITS,
  404                 (unsigned)pmp->pm_inusemap[cn / N_INUSEBITS]));
  405         pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
  406         KASSERT(pmp->pm_freeclustercount > 0, ("usemap_alloc: too little"));
  407         pmp->pm_freeclustercount--;
  408         pmp->pm_flags |= MSDOSFS_FSIMOD;
  409 }
  410 
  411 static __inline void
  412 usemap_free(pmp, cn)
  413         struct msdosfsmount *pmp;
  414         u_long cn;
  415 {
  416 
  417         MSDOSFS_ASSERT_MP_LOCKED(pmp);
  418         pmp->pm_freeclustercount++;
  419         pmp->pm_flags |= MSDOSFS_FSIMOD;
  420         KASSERT((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
  421             != 0, ("Freeing unused sector %ld %ld %x", cn, cn % N_INUSEBITS,
  422                 (unsigned)pmp->pm_inusemap[cn / N_INUSEBITS]));
  423         pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
  424 }
  425 
  426 int
  427 clusterfree(pmp, cluster, oldcnp)
  428         struct msdosfsmount *pmp;
  429         u_long cluster;
  430         u_long *oldcnp;
  431 {
  432         int error;
  433         u_long oldcn;
  434 
  435         error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
  436         if (error)
  437                 return (error);
  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         MSDOSFS_LOCK_MP(pmp);
  444         usemap_free(pmp, cluster);
  445         MSDOSFS_UNLOCK_MP(pmp);
  446         if (oldcnp)
  447                 *oldcnp = oldcn;
  448         return (0);
  449 }
  450 
  451 /*
  452  * Get or Set or 'Get and Set' the cluster'th entry in the fat.
  453  *
  454  * function     - whether to get or set a fat entry
  455  * pmp          - address of the msdosfsmount structure for the filesystem
  456  *                whose fat is to be manipulated.
  457  * cn           - which cluster is of interest
  458  * oldcontents  - address of a word that is to receive the contents of the
  459  *                cluster'th entry if this is a get function
  460  * newcontents  - the new value to be written into the cluster'th element of
  461  *                the fat if this is a set function.
  462  *
  463  * This function can also be used to free a cluster by setting the fat entry
  464  * for a cluster to 0.
  465  *
  466  * All copies of the fat are updated if this is a set function. NOTE: If
  467  * fatentry() marks a cluster as free it does not update the inusemap in
  468  * the msdosfsmount structure. This is left to the caller.
  469  */
  470 int
  471 fatentry(function, pmp, cn, oldcontents, newcontents)
  472         int function;
  473         struct msdosfsmount *pmp;
  474         u_long cn;
  475         u_long *oldcontents;
  476         u_long newcontents;
  477 {
  478         int error;
  479         u_long readcn;
  480         u_long bn, bo, bsize, byteoffset;
  481         struct buf *bp;
  482 
  483 #ifdef  MSDOSFS_DEBUG
  484         printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n",
  485             function, pmp, cn, oldcontents, newcontents);
  486 #endif
  487 
  488 #ifdef DIAGNOSTIC
  489         /*
  490          * Be sure they asked us to do something.
  491          */
  492         if ((function & (FAT_SET | FAT_GET)) == 0) {
  493 #ifdef MSDOSFS_DEBUG
  494                 printf("fatentry(): function code doesn't specify get or set\n");
  495 #endif
  496                 return (EINVAL);
  497         }
  498 
  499         /*
  500          * If they asked us to return a cluster number but didn't tell us
  501          * where to put it, give them an error.
  502          */
  503         if ((function & FAT_GET) && oldcontents == NULL) {
  504 #ifdef MSDOSFS_DEBUG
  505                 printf("fatentry(): get function with no place to put result\n");
  506 #endif
  507                 return (EINVAL);
  508         }
  509 #endif
  510 
  511         /*
  512          * Be sure the requested cluster is in the filesystem.
  513          */
  514         if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
  515                 return (EINVAL);
  516 
  517         byteoffset = FATOFS(pmp, cn);
  518         fatblock(pmp, byteoffset, &bn, &bsize, &bo);
  519         error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
  520         if (error) {
  521                 brelse(bp);
  522                 return (error);
  523         }
  524 
  525         if (function & FAT_GET) {
  526                 if (FAT32(pmp))
  527                         readcn = getulong(&bp->b_data[bo]);
  528                 else
  529                         readcn = getushort(&bp->b_data[bo]);
  530                 if (FAT12(pmp) & (cn & 1))
  531                         readcn >>= 4;
  532                 readcn &= pmp->pm_fatmask;
  533                 /* map reserved fat entries to same values for all fats */
  534                 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
  535                         readcn |= ~pmp->pm_fatmask;
  536                 *oldcontents = readcn;
  537         }
  538         if (function & FAT_SET) {
  539                 switch (pmp->pm_fatmask) {
  540                 case FAT12_MASK:
  541                         readcn = getushort(&bp->b_data[bo]);
  542                         if (cn & 1) {
  543                                 readcn &= 0x000f;
  544                                 readcn |= newcontents << 4;
  545                         } else {
  546                                 readcn &= 0xf000;
  547                                 readcn |= newcontents & 0xfff;
  548                         }
  549                         putushort(&bp->b_data[bo], readcn);
  550                         break;
  551                 case FAT16_MASK:
  552                         putushort(&bp->b_data[bo], newcontents);
  553                         break;
  554                 case FAT32_MASK:
  555                         /*
  556                          * According to spec we have to retain the
  557                          * high order bits of the fat entry.
  558                          */
  559                         readcn = getulong(&bp->b_data[bo]);
  560                         readcn &= ~FAT32_MASK;
  561                         readcn |= newcontents & FAT32_MASK;
  562                         putulong(&bp->b_data[bo], readcn);
  563                         break;
  564                 }
  565                 updatefats(pmp, bp, bn);
  566                 bp = NULL;
  567                 pmp->pm_fmod = 1;
  568         }
  569         if (bp)
  570                 brelse(bp);
  571         return (0);
  572 }
  573 
  574 /*
  575  * Update a contiguous cluster chain
  576  *
  577  * pmp      - mount point
  578  * start    - first cluster of chain
  579  * count    - number of clusters in chain
  580  * fillwith - what to write into fat entry of last cluster
  581  */
  582 static int
  583 fatchain(pmp, start, count, fillwith)
  584         struct msdosfsmount *pmp;
  585         u_long start;
  586         u_long count;
  587         u_long fillwith;
  588 {
  589         int error;
  590         u_long bn, bo, bsize, byteoffset, readcn, newc;
  591         struct buf *bp;
  592 
  593 #ifdef MSDOSFS_DEBUG
  594         printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n",
  595             pmp, start, count, fillwith);
  596 #endif
  597         /*
  598          * Be sure the clusters are in the filesystem.
  599          */
  600         if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
  601                 return (EINVAL);
  602 
  603         while (count > 0) {
  604                 byteoffset = FATOFS(pmp, start);
  605                 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
  606                 error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
  607                 if (error) {
  608                         brelse(bp);
  609                         return (error);
  610                 }
  611                 while (count > 0) {
  612                         start++;
  613                         newc = --count > 0 ? start : fillwith;
  614                         switch (pmp->pm_fatmask) {
  615                         case FAT12_MASK:
  616                                 readcn = getushort(&bp->b_data[bo]);
  617                                 if (start & 1) {
  618                                         readcn &= 0xf000;
  619                                         readcn |= newc & 0xfff;
  620                                 } else {
  621                                         readcn &= 0x000f;
  622                                         readcn |= newc << 4;
  623                                 }
  624                                 putushort(&bp->b_data[bo], readcn);
  625                                 bo++;
  626                                 if (!(start & 1))
  627                                         bo++;
  628                                 break;
  629                         case FAT16_MASK:
  630                                 putushort(&bp->b_data[bo], newc);
  631                                 bo += 2;
  632                                 break;
  633                         case FAT32_MASK:
  634                                 readcn = getulong(&bp->b_data[bo]);
  635                                 readcn &= ~pmp->pm_fatmask;
  636                                 readcn |= newc & pmp->pm_fatmask;
  637                                 putulong(&bp->b_data[bo], readcn);
  638                                 bo += 4;
  639                                 break;
  640                         }
  641                         if (bo >= bsize)
  642                                 break;
  643                 }
  644                 updatefats(pmp, bp, bn);
  645         }
  646         pmp->pm_fmod = 1;
  647         return (0);
  648 }
  649 
  650 /*
  651  * Check the length of a free cluster chain starting at start.
  652  *
  653  * pmp   - mount point
  654  * start - start of chain
  655  * count - maximum interesting length
  656  */
  657 static int
  658 chainlength(pmp, start, count)
  659         struct msdosfsmount *pmp;
  660         u_long start;
  661         u_long count;
  662 {
  663         u_long idx, max_idx;
  664         u_int map;
  665         u_long len;
  666 
  667         MSDOSFS_ASSERT_MP_LOCKED(pmp);
  668 
  669         max_idx = pmp->pm_maxcluster / N_INUSEBITS;
  670         idx = start / N_INUSEBITS;
  671         start %= N_INUSEBITS;
  672         map = pmp->pm_inusemap[idx];
  673         map &= ~((1 << start) - 1);
  674         if (map) {
  675                 len = ffs(map) - 1 - start;
  676                 return (len > count ? count : len);
  677         }
  678         len = N_INUSEBITS - start;
  679         if (len >= count)
  680                 return (count);
  681         while (++idx <= max_idx) {
  682                 if (len >= count)
  683                         break;
  684                 map = pmp->pm_inusemap[idx];
  685                 if (map) {
  686                         len += ffs(map) - 1;
  687                         break;
  688                 }
  689                 len += N_INUSEBITS;
  690         }
  691         return (len > count ? count : len);
  692 }
  693 
  694 /*
  695  * Allocate contigous free clusters.
  696  *
  697  * pmp        - mount point.
  698  * start      - start of cluster chain.
  699  * count      - number of clusters to allocate.
  700  * fillwith   - put this value into the fat entry for the
  701  *              last allocated cluster.
  702  * retcluster - put the first allocated cluster's number here.
  703  * got        - how many clusters were actually allocated.
  704  */
  705 static int
  706 chainalloc(pmp, start, count, fillwith, retcluster, got)
  707         struct msdosfsmount *pmp;
  708         u_long start;
  709         u_long count;
  710         u_long fillwith;
  711         u_long *retcluster;
  712         u_long *got;
  713 {
  714         int error;
  715         u_long cl, n;
  716 
  717         MSDOSFS_ASSERT_MP_LOCKED(pmp);
  718 
  719         for (cl = start, n = count; n-- > 0;)
  720                 usemap_alloc(pmp, cl++);
  721         pmp->pm_nxtfree = start + count;
  722         if (pmp->pm_nxtfree > pmp->pm_maxcluster)
  723                 pmp->pm_nxtfree = CLUST_FIRST;
  724         pmp->pm_flags |= MSDOSFS_FSIMOD;
  725         error = fatchain(pmp, start, count, fillwith);
  726         if (error != 0)
  727                 return (error);
  728 #ifdef MSDOSFS_DEBUG
  729         printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n",
  730             start, count);
  731 #endif
  732         if (retcluster)
  733                 *retcluster = start;
  734         if (got)
  735                 *got = count;
  736         return (0);
  737 }
  738 
  739 /*
  740  * Allocate contiguous free clusters.
  741  *
  742  * pmp        - mount point.
  743  * start      - preferred start of cluster chain.
  744  * count      - number of clusters requested.
  745  * fillwith   - put this value into the fat entry for the
  746  *              last allocated cluster.
  747  * retcluster - put the first allocated cluster's number here.
  748  * got        - how many clusters were actually allocated.
  749  */
  750 int
  751 clusteralloc(struct msdosfsmount *pmp, u_long start, u_long count,
  752     u_long fillwith, u_long *retcluster, u_long *got)
  753 {
  754         int error;
  755 
  756         MSDOSFS_LOCK_MP(pmp);
  757         error = clusteralloc1(pmp, start, count, fillwith, retcluster, got);
  758         MSDOSFS_UNLOCK_MP(pmp);
  759         return (error);
  760 }
  761 
  762 static int
  763 clusteralloc1(struct msdosfsmount *pmp, u_long start, u_long count,
  764     u_long fillwith, u_long *retcluster, u_long *got)
  765 {
  766         u_long idx;
  767         u_long len, newst, foundl, cn, l;
  768         u_long foundcn = 0; /* XXX: foundcn could be used unititialized */
  769         u_int map;
  770 
  771         MSDOSFS_ASSERT_MP_LOCKED(pmp);
  772 
  773 #ifdef MSDOSFS_DEBUG
  774         printf("clusteralloc(): find %lu clusters\n", count);
  775 #endif
  776         if (start) {
  777                 if ((len = chainlength(pmp, start, count)) >= count)
  778                         return (chainalloc(pmp, start, count, fillwith, retcluster, got));
  779         } else
  780                 len = 0;
  781 
  782         newst = pmp->pm_nxtfree;
  783         foundl = 0;
  784 
  785         for (cn = newst; cn <= pmp->pm_maxcluster;) {
  786                 idx = cn / N_INUSEBITS;
  787                 map = pmp->pm_inusemap[idx];
  788                 map |= (1 << (cn % N_INUSEBITS)) - 1;
  789                 if (map != (u_int)-1) {
  790                         cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
  791                         if ((l = chainlength(pmp, cn, count)) >= count)
  792                                 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
  793                         if (l > foundl) {
  794                                 foundcn = cn;
  795                                 foundl = l;
  796                         }
  797                         cn += l + 1;
  798                         continue;
  799                 }
  800                 cn += N_INUSEBITS - cn % N_INUSEBITS;
  801         }
  802         for (cn = 0; cn < newst;) {
  803                 idx = cn / N_INUSEBITS;
  804                 map = pmp->pm_inusemap[idx];
  805                 map |= (1 << (cn % N_INUSEBITS)) - 1;
  806                 if (map != (u_int)-1) {
  807                         cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
  808                         if ((l = chainlength(pmp, cn, count)) >= count)
  809                                 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
  810                         if (l > foundl) {
  811                                 foundcn = cn;
  812                                 foundl = l;
  813                         }
  814                         cn += l + 1;
  815                         continue;
  816                 }
  817                 cn += N_INUSEBITS - cn % N_INUSEBITS;
  818         }
  819 
  820         if (!foundl)
  821                 return (ENOSPC);
  822 
  823         if (len)
  824                 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
  825         else
  826                 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
  827 }
  828 
  829 
  830 /*
  831  * Free a chain of clusters.
  832  *
  833  * pmp          - address of the msdosfs mount structure for the filesystem
  834  *                containing the cluster chain to be freed.
  835  * startcluster - number of the 1st cluster in the chain of clusters to be
  836  *                freed.
  837  */
  838 int
  839 freeclusterchain(pmp, cluster)
  840         struct msdosfsmount *pmp;
  841         u_long cluster;
  842 {
  843         int error;
  844         struct buf *bp = NULL;
  845         u_long bn, bo, bsize, byteoffset;
  846         u_long readcn, lbn = -1;
  847 
  848         MSDOSFS_LOCK_MP(pmp);
  849         while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
  850                 byteoffset = FATOFS(pmp, cluster);
  851                 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
  852                 if (lbn != bn) {
  853                         if (bp)
  854                                 updatefats(pmp, bp, lbn);
  855                         error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
  856                         if (error) {
  857                                 brelse(bp);
  858                                 MSDOSFS_UNLOCK_MP(pmp);
  859                                 return (error);
  860                         }
  861                         lbn = bn;
  862                 }
  863                 usemap_free(pmp, cluster);
  864                 switch (pmp->pm_fatmask) {
  865                 case FAT12_MASK:
  866                         readcn = getushort(&bp->b_data[bo]);
  867                         if (cluster & 1) {
  868                                 cluster = readcn >> 4;
  869                                 readcn &= 0x000f;
  870                                 readcn |= MSDOSFSFREE << 4;
  871                         } else {
  872                                 cluster = readcn;
  873                                 readcn &= 0xf000;
  874                                 readcn |= MSDOSFSFREE & 0xfff;
  875                         }
  876                         putushort(&bp->b_data[bo], readcn);
  877                         break;
  878                 case FAT16_MASK:
  879                         cluster = getushort(&bp->b_data[bo]);
  880                         putushort(&bp->b_data[bo], MSDOSFSFREE);
  881                         break;
  882                 case FAT32_MASK:
  883                         cluster = getulong(&bp->b_data[bo]);
  884                         putulong(&bp->b_data[bo],
  885                                  (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
  886                         break;
  887                 }
  888                 cluster &= pmp->pm_fatmask;
  889                 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
  890                         cluster |= pmp->pm_fatmask;
  891         }
  892         if (bp)
  893                 updatefats(pmp, bp, bn);
  894         MSDOSFS_UNLOCK_MP(pmp);
  895         return (0);
  896 }
  897 
  898 /*
  899  * Read in fat blocks looking for free clusters. For every free cluster
  900  * found turn off its corresponding bit in the pm_inusemap.
  901  */
  902 int
  903 fillinusemap(pmp)
  904         struct msdosfsmount *pmp;
  905 {
  906         struct buf *bp = NULL;
  907         u_long cn, readcn;
  908         int error;
  909         u_long bn, bo, bsize, byteoffset;
  910 
  911         MSDOSFS_ASSERT_MP_LOCKED(pmp);
  912 
  913         /*
  914          * Mark all clusters in use, we mark the free ones in the fat scan
  915          * loop further down.
  916          */
  917         for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
  918                 pmp->pm_inusemap[cn] = (u_int)-1;
  919 
  920         /*
  921          * Figure how many free clusters are in the filesystem by ripping
  922          * through the fat counting the number of entries whose content is
  923          * zero.  These represent free clusters.
  924          */
  925         pmp->pm_freeclustercount = 0;
  926         for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
  927                 byteoffset = FATOFS(pmp, cn);
  928                 bo = byteoffset % pmp->pm_fatblocksize;
  929                 if (!bo || !bp) {
  930                         /* Read new FAT block */
  931                         if (bp)
  932                                 brelse(bp);
  933                         fatblock(pmp, byteoffset, &bn, &bsize, NULL);
  934                         error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
  935                         if (error) {
  936                                 brelse(bp);
  937                                 return (error);
  938                         }
  939                 }
  940                 if (FAT32(pmp))
  941                         readcn = getulong(&bp->b_data[bo]);
  942                 else
  943                         readcn = getushort(&bp->b_data[bo]);
  944                 if (FAT12(pmp) && (cn & 1))
  945                         readcn >>= 4;
  946                 readcn &= pmp->pm_fatmask;
  947 
  948                 if (readcn == 0)
  949                         usemap_free(pmp, cn);
  950         }
  951         if (bp != NULL)
  952                 brelse(bp);
  953         return (0);
  954 }
  955 
  956 /*
  957  * Allocate a new cluster and chain it onto the end of the file.
  958  *
  959  * dep   - the file to extend
  960  * count - number of clusters to allocate
  961  * bpp   - where to return the address of the buf header for the first new
  962  *         file block
  963  * ncp   - where to put cluster number of the first newly allocated cluster
  964  *         If this pointer is 0, do not return the cluster number.
  965  * flags - see fat.h
  966  *
  967  * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
  968  * the de_flag field of the denode and it does not change the de_FileSize
  969  * field.  This is left for the caller to do.
  970  */
  971 int
  972 extendfile(dep, count, bpp, ncp, flags)
  973         struct denode *dep;
  974         u_long count;
  975         struct buf **bpp;
  976         u_long *ncp;
  977         int flags;
  978 {
  979         int error;
  980         u_long frcn;
  981         u_long cn, got;
  982         struct msdosfsmount *pmp = dep->de_pmp;
  983         struct buf *bp;
  984         daddr_t blkno;
  985 
  986         /*
  987          * Don't try to extend the root directory
  988          */
  989         if (dep->de_StartCluster == MSDOSFSROOT
  990             && (dep->de_Attributes & ATTR_DIRECTORY)) {
  991 #ifdef MSDOSFS_DEBUG
  992                 printf("extendfile(): attempt to extend root directory\n");
  993 #endif
  994                 return (ENOSPC);
  995         }
  996 
  997         /*
  998          * If the "file's last cluster" cache entry is empty, and the file
  999          * is not empty, then fill the cache entry by calling pcbmap().
 1000          */
 1001         if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
 1002             dep->de_StartCluster != 0) {
 1003                 error = pcbmap(dep, 0xffff, 0, &cn, 0);
 1004                 /* we expect it to return E2BIG */
 1005                 if (error != E2BIG)
 1006                         return (error);
 1007         }
 1008 
 1009         dep->de_fc[FC_NEXTTOLASTFC].fc_frcn =
 1010             dep->de_fc[FC_LASTFC].fc_frcn;
 1011         dep->de_fc[FC_NEXTTOLASTFC].fc_fsrcn =
 1012             dep->de_fc[FC_LASTFC].fc_fsrcn;
 1013         while (count > 0) {
 1014                 /*
 1015                  * Allocate a new cluster chain and cat onto the end of the
 1016                  * file.  * If the file is empty we make de_StartCluster point
 1017                  * to the new block.  Note that de_StartCluster being 0 is
 1018                  * sufficient to be sure the file is empty since we exclude
 1019                  * attempts to extend the root directory above, and the root
 1020                  * dir is the only file with a startcluster of 0 that has
 1021                  * blocks allocated (sort of).
 1022                  */
 1023                 if (dep->de_StartCluster == 0)
 1024                         cn = 0;
 1025                 else
 1026                         cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
 1027                 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got);
 1028                 if (error)
 1029                         return (error);
 1030 
 1031                 count -= got;
 1032 
 1033                 /*
 1034                  * Give them the filesystem relative cluster number if they want
 1035                  * it.
 1036                  */
 1037                 if (ncp) {
 1038                         *ncp = cn;
 1039                         ncp = NULL;
 1040                 }
 1041 
 1042                 if (dep->de_StartCluster == 0) {
 1043                         dep->de_StartCluster = cn;
 1044                         frcn = 0;
 1045                 } else {
 1046                         error = fatentry(FAT_SET, pmp,
 1047                                          dep->de_fc[FC_LASTFC].fc_fsrcn,
 1048                                          0, cn);
 1049                         if (error) {
 1050                                 clusterfree(pmp, cn, NULL);
 1051                                 return (error);
 1052                         }
 1053                         frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
 1054                 }
 1055 
 1056                 /*
 1057                  * Update the "last cluster of the file" entry in the denode's fat
 1058                  * cache.
 1059                  */
 1060                 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
 1061 
 1062                 if (flags & DE_CLEAR) {
 1063                         while (got-- > 0) {
 1064                                 /*
 1065                                  * Get the buf header for the new block of the file.
 1066                                  */
 1067                                 if (dep->de_Attributes & ATTR_DIRECTORY)
 1068                                         bp = getblk(pmp->pm_devvp,
 1069                                             cntobn(pmp, cn++),
 1070                                             pmp->pm_bpcluster, 0, 0, 0);
 1071                                 else {
 1072                                         bp = getblk(DETOV(dep),
 1073                                             frcn++,
 1074                                             pmp->pm_bpcluster, 0, 0, 0);
 1075                                         /*
 1076                                          * Do the bmap now, as in msdosfs_write
 1077                                          */
 1078                                         if (pcbmap(dep,
 1079                                             bp->b_lblkno,
 1080                                             &blkno, 0, 0))
 1081                                                 bp->b_blkno = -1;
 1082                                         if (bp->b_blkno == -1)
 1083                                                 panic("extendfile: pcbmap");
 1084                                         else
 1085                                                 bp->b_blkno = blkno;
 1086                                 }
 1087                                 vfs_bio_clrbuf(bp);
 1088                                 if (bpp) {
 1089                                         *bpp = bp;
 1090                                         bpp = NULL;
 1091                                 } else
 1092                                         bdwrite(bp);
 1093                         }
 1094                 }
 1095         }
 1096 
 1097         return (0);
 1098 }
 1099 
 1100 /*-
 1101  * Routine to mark a FAT16 or FAT32 volume as "clean" or "dirty" by
 1102  * manipulating the upper bit of the FAT entry for cluster 1.  Note that
 1103  * this bit is not defined for FAT12 volumes, which are always assumed to
 1104  * be clean.
 1105  *
 1106  * The fatentry() routine only works on cluster numbers that a file could
 1107  * occupy, so it won't manipulate the entry for cluster 1.  So we have to do
 1108  * it here.  The code was stolen from fatentry() and tailored for cluster 1.
 1109  *
 1110  * Inputs:
 1111  *      pmp     The MS-DOS volume to mark
 1112  *      dirty   Non-zero if the volume should be marked dirty; zero if it
 1113  *              should be marked clean
 1114  *
 1115  * Result:
 1116  *      0       Success
 1117  *      EROFS   Volume is read-only
 1118  *      ?       (other errors from called routines)
 1119  */
 1120 int
 1121 markvoldirty(struct msdosfsmount *pmp, int dirty)
 1122 {
 1123         struct buf *bp;
 1124         u_long bn, bo, bsize, byteoffset, fatval;
 1125         int error;
 1126 
 1127         /*
 1128          * FAT12 does not support a "clean" bit, so don't do anything for
 1129          * FAT12.
 1130          */
 1131         if (FAT12(pmp))
 1132                 return (0);
 1133 
 1134         /* Can't change the bit on a read-only filesystem. */
 1135         if (pmp->pm_flags & MSDOSFSMNT_RONLY)
 1136                 return (EROFS);
 1137 
 1138         /*
 1139          * Fetch the block containing the FAT entry.  It is given by the
 1140          * pseudo-cluster 1.
 1141          */
 1142         byteoffset = FATOFS(pmp, 1);
 1143         fatblock(pmp, byteoffset, &bn, &bsize, &bo);
 1144         error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
 1145         if (error) {
 1146                 brelse(bp);
 1147                 return (error);
 1148         }
 1149 
 1150         /*
 1151          * Get the current value of the FAT entry and set/clear the relevant
 1152          * bit.  Dirty means clear the "clean" bit; clean means set the
 1153          * "clean" bit.
 1154          */
 1155         if (FAT32(pmp)) {
 1156                 /* FAT32 uses bit 27. */
 1157                 fatval = getulong(&bp->b_data[bo]);
 1158                 if (dirty)
 1159                         fatval &= 0xF7FFFFFF;
 1160                 else
 1161                         fatval |= 0x08000000;
 1162                 putulong(&bp->b_data[bo], fatval);
 1163         } else {
 1164                 /* Must be FAT16; use bit 15. */
 1165                 fatval = getushort(&bp->b_data[bo]);
 1166                 if (dirty)
 1167                         fatval &= 0x7FFF;
 1168                 else
 1169                         fatval |= 0x8000;
 1170                 putushort(&bp->b_data[bo], fatval);
 1171         }
 1172 
 1173         /* Write out the modified FAT block synchronously. */
 1174         return (bwrite(bp));
 1175 }

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