1 /* $FreeBSD: src/sys/msdosfs/msdosfs_fat.c,v 1.23 2000/01/27 14:43:06 nyan Exp $ */
2 /* $DragonFly: src/sys/vfs/msdosfs/msdosfs_fat.c,v 1.5 2003/08/20 09:56:32 rob Exp $ */
3 /* $NetBSD: msdosfs_fat.c,v 1.28 1997/11/17 15:36:49 ws Exp $ */
6 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
7 * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
9 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by TooLs GmbH.
22 * 4. The name of TooLs GmbH may not be used to endorse or promote products
23 * derived from this software without specific prior written permission.
25 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
29 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
30 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
31 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
32 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
33 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
34 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 * Written by Paul Popelka (paulp@uts.amdahl.com)
39 * You can do anything you want with this software, just don't say you wrote
40 * it, and don't remove this notice.
42 * This software is provided "as is".
44 * The author supplies this software to be publicly redistributed on the
45 * understanding that the author is not responsible for the correct
46 * functioning of this software in any circumstances and is not liable for
47 * any damages caused by this software.
53 * kernel include files.
55 #include <sys/param.h>
56 #include <sys/systm.h>
58 #include <sys/mount.h> /* to define statfs structure */
59 #include <sys/vnode.h> /* to define vattr structure */
62 * msdosfs include files.
65 #include "msdosfsmount.h"
73 static int fc_fileextends; /* # of file extends */
74 static int fc_lfcempty; /* # of time last file cluster cache entry
76 static int fc_bmapcalls; /* # of times pcbmap was called */
79 static int fc_lmdistance[LMMAX];/* counters for how far off the last
80 * cluster mapped entry was. */
81 static int fc_largedistance; /* off by more than LMMAX */
83 static int chainalloc (struct msdosfsmount *pmp, u_long start,
84 u_long count, u_long fillwith,
85 u_long *retcluster, u_long *got);
86 static int chainlength (struct msdosfsmount *pmp, u_long start,
88 static void fatblock (struct msdosfsmount *pmp, u_long ofs,
89 u_long *bnp, u_long *sizep, u_long *bop);
90 static int fatchain (struct msdosfsmount *pmp, u_long start,
91 u_long count, u_long fillwith);
92 static void fc_lookup (struct denode *dep, u_long findcn,
93 u_long *frcnp, u_long *fsrcnp);
94 static void updatefats (struct msdosfsmount *pmp, struct buf *bp,
97 usemap_alloc (struct msdosfsmount *pmp, u_long cn);
99 usemap_free (struct msdosfsmount *pmp, u_long cn);
102 fatblock(pmp, ofs, bnp, sizep, bop)
103 struct msdosfsmount *pmp;
111 bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
112 size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
114 bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
121 *bop = ofs % pmp->pm_fatblocksize;
125 * Map the logical cluster number of a file into a physical disk sector
126 * that is filesystem relative.
128 * dep - address of denode representing the file of interest
129 * findcn - file relative cluster whose filesystem relative cluster number
130 * and/or block number are/is to be found
131 * bnp - address of where to place the file system relative block number.
132 * If this pointer is null then don't return this quantity.
133 * cnp - address of where to place the file system relative cluster number.
134 * If this pointer is null then don't return this quantity.
136 * NOTE: Either bnp or cnp must be non-null.
137 * This function has one side effect. If the requested file relative cluster
138 * is beyond the end of file, then the actual number of clusters in the file
139 * is returned in *cnp. This is useful for determining how long a directory is.
140 * If cnp is null, nothing is returned.
143 pcbmap(dep, findcn, bnp, cnp, sp)
145 u_long findcn; /* file relative cluster to get */
146 daddr_t *bnp; /* returned filesys relative blk number */
147 u_long *cnp; /* returned cluster number */
148 int *sp; /* returned block size */
153 u_long prevcn = 0; /* XXX: prevcn could be used unititialized */
157 struct buf *bp = NULL;
159 struct msdosfsmount *pmp = dep->de_pmp;
165 * If they don't give us someplace to return a value then don't
166 * bother doing anything.
168 if (bnp == NULL && cnp == NULL && sp == NULL)
171 cn = dep->de_StartCluster;
173 * The "file" that makes up the root directory is contiguous,
174 * permanently allocated, of fixed size, and is not made up of
175 * clusters. If the cluster number is beyond the end of the root
176 * directory, then return the number of clusters in the file.
178 if (cn == MSDOSFSROOT) {
179 if (dep->de_Attributes & ATTR_DIRECTORY) {
180 if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
182 *cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
186 *bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
190 *sp = min(pmp->pm_bpcluster,
191 dep->de_FileSize - de_cn2off(pmp, findcn));
193 } else { /* just an empty file */
201 * All other files do I/O in cluster sized blocks
204 *sp = pmp->pm_bpcluster;
207 * Rummage around in the fat cache, maybe we can avoid tromping
208 * thru every fat entry for the file. And, keep track of how far
209 * off the cache was from where we wanted to be.
212 fc_lookup(dep, findcn, &i, &cn);
213 if ((bn = findcn - i) >= LMMAX)
219 * Handle all other files or directories the normal way.
221 for (; i < findcn; i++) {
223 * Stop with all reserved clusters, not just with EOF.
225 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
227 byteoffset = FATOFS(pmp, cn);
228 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
232 error = bread(pmp->pm_devvp, bn, bsize, &bp);
241 cn = getulong(&bp->b_data[bo]);
243 cn = getushort(&bp->b_data[bo]);
244 if (FAT12(pmp) && (prevcn & 1))
246 cn &= pmp->pm_fatmask;
249 * Force the special cluster numbers
250 * to be the same for all cluster sizes
251 * to let the rest of msdosfs handle
252 * all cases the same.
254 if ((cn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
255 cn |= ~pmp->pm_fatmask;
258 if (!MSDOSFSEOF(pmp, cn)) {
262 *bnp = cntobn(pmp, cn);
265 fc_setcache(dep, FC_LASTMAP, i, cn);
274 /* update last file cluster entry in the fat cache */
275 fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
280 * Find the closest entry in the fat cache to the cluster we are looking
284 fc_lookup(dep, findcn, frcnp, fsrcnp)
292 struct fatcache *closest = 0;
294 for (i = 0; i < FC_SIZE; i++) {
295 cn = dep->de_fc[i].fc_frcn;
296 if (cn != FCE_EMPTY && cn <= findcn) {
297 if (closest == 0 || cn > closest->fc_frcn)
298 closest = &dep->de_fc[i];
302 *frcnp = closest->fc_frcn;
303 *fsrcnp = closest->fc_fsrcn;
308 * Purge the fat cache in denode dep of all entries relating to file
309 * relative cluster frcn and beyond.
317 struct fatcache *fcp;
320 for (i = 0; i < FC_SIZE; i++, fcp++) {
321 if (fcp->fc_frcn >= frcn)
322 fcp->fc_frcn = FCE_EMPTY;
328 * If mirroring the fat, update all copies, with the first copy as last.
329 * Else update only the current fat (ignoring the others).
331 * pmp - msdosfsmount structure for filesystem to update
332 * bp - addr of modified fat block
333 * fatbn - block number relative to begin of filesystem of the modified fat block.
336 updatefats(pmp, bp, fatbn)
337 struct msdosfsmount *pmp;
345 printf("updatefats(pmp %p, bp %p, fatbn %lu)\n", pmp, bp, fatbn);
349 * If we have an FSInfo block, update it.
351 if (pmp->pm_fsinfo) {
352 u_long cn = pmp->pm_nxtfree;
354 if (pmp->pm_freeclustercount
355 && (pmp->pm_inusemap[cn / N_INUSEBITS]
356 & (1 << (cn % N_INUSEBITS)))) {
358 * The cluster indicated in FSInfo isn't free
359 * any longer. Got get a new free one.
361 for (cn = 0; cn < pmp->pm_maxcluster; cn += N_INUSEBITS)
362 if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
365 + ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
368 if (bread(pmp->pm_devvp, pmp->pm_fsinfo, fsi_size(pmp), &bpn) != 0) {
370 * Ignore the error, but turn off FSInfo update for the future.
375 struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
377 putulong(fp->fsinfree, pmp->pm_freeclustercount);
378 putulong(fp->fsinxtfree, pmp->pm_nxtfree);
379 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
386 if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
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.
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)
410 * Write out the first (or current) fat last.
412 if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
417 * Maybe update fsinfo sector here?
422 * Updating entries in 12 bit fats is a pain in the butt.
424 * The following picture shows where nibbles go when moving from a 12 bit
425 * cluster number into the appropriate bytes in the FAT.
427 * byte m byte m+1 byte m+2
428 * +----+----+ +----+----+ +----+----+
429 * | 0 1 | | 2 3 | | 4 5 | FAT bytes
430 * +----+----+ +----+----+ +----+----+
432 * +----+----+----+ +----+----+----+
433 * | 3 0 1 | | 4 5 2 |
434 * +----+----+----+ +----+----+----+
435 * cluster n cluster n+1
437 * Where n is even. m = n + (n >> 2)
441 usemap_alloc(pmp, cn)
442 struct msdosfsmount *pmp;
446 pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
447 pmp->pm_freeclustercount--;
452 struct msdosfsmount *pmp;
456 pmp->pm_freeclustercount++;
457 pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
461 clusterfree(pmp, cluster, oldcnp)
462 struct msdosfsmount *pmp;
469 usemap_free(pmp, cluster);
470 error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
472 usemap_alloc(pmp, cluster);
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.
486 * Get or Set or 'Get and Set' the cluster'th entry in the fat.
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.
497 * This function can also be used to free a cluster by setting the fat entry
498 * for a cluster to 0.
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.
505 fatentry(function, pmp, cn, oldcontents, newcontents)
507 struct msdosfsmount *pmp;
514 u_long bn, bo, bsize, byteoffset;
518 printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n",
519 function, pmp, cn, oldcontents, newcontents);
524 * Be sure they asked us to do something.
526 if ((function & (FAT_SET | FAT_GET)) == 0) {
527 printf("fatentry(): function code doesn't specify get or set\n");
532 * If they asked us to return a cluster number but didn't tell us
533 * where to put it, give them an error.
535 if ((function & FAT_GET) && oldcontents == NULL) {
536 printf("fatentry(): get function with no place to put result\n");
542 * Be sure the requested cluster is in the filesystem.
544 if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
547 byteoffset = FATOFS(pmp, cn);
548 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
549 error = bread(pmp->pm_devvp, bn, bsize, &bp);
555 if (function & FAT_GET) {
557 readcn = getulong(&bp->b_data[bo]);
559 readcn = getushort(&bp->b_data[bo]);
560 if (FAT12(pmp) & (cn & 1))
562 readcn &= pmp->pm_fatmask;
563 /* map reserved fat entries to same values for all fats */
564 if ((readcn | ~pmp->pm_fatmask) >= CLUST_RSRVD)
565 readcn |= ~pmp->pm_fatmask;
566 *oldcontents = readcn;
568 if (function & FAT_SET) {
569 switch (pmp->pm_fatmask) {
571 readcn = getushort(&bp->b_data[bo]);
574 readcn |= newcontents << 4;
577 readcn |= newcontents & 0xfff;
579 putushort(&bp->b_data[bo], readcn);
582 putushort(&bp->b_data[bo], newcontents);
586 * According to spec we have to retain the
587 * high order bits of the fat entry.
589 readcn = getulong(&bp->b_data[bo]);
590 readcn &= ~FAT32_MASK;
591 readcn |= newcontents & FAT32_MASK;
592 putulong(&bp->b_data[bo], readcn);
595 updatefats(pmp, bp, bn);
605 * Update a contiguous cluster chain
608 * start - first cluster of chain
609 * count - number of clusters in chain
610 * fillwith - what to write into fat entry of last cluster
613 fatchain(pmp, start, count, fillwith)
614 struct msdosfsmount *pmp;
620 u_long bn, bo, bsize, byteoffset, readcn, newc;
624 printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n",
625 pmp, start, count, fillwith);
628 * Be sure the clusters are in the filesystem.
630 if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
634 byteoffset = FATOFS(pmp, start);
635 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
636 error = bread(pmp->pm_devvp, bn, bsize, &bp);
643 newc = --count > 0 ? start : fillwith;
644 switch (pmp->pm_fatmask) {
646 readcn = getushort(&bp->b_data[bo]);
649 readcn |= newc & 0xfff;
654 putushort(&bp->b_data[bo], readcn);
660 putushort(&bp->b_data[bo], newc);
664 readcn = getulong(&bp->b_data[bo]);
665 readcn &= ~pmp->pm_fatmask;
666 readcn |= newc & pmp->pm_fatmask;
667 putulong(&bp->b_data[bo], readcn);
674 updatefats(pmp, bp, bn);
681 * Check the length of a free cluster chain starting at start.
684 * start - start of chain
685 * count - maximum interesting length
688 chainlength(pmp, start, count)
689 struct msdosfsmount *pmp;
697 max_idx = pmp->pm_maxcluster / N_INUSEBITS;
698 idx = start / N_INUSEBITS;
699 start %= N_INUSEBITS;
700 map = pmp->pm_inusemap[idx];
701 map &= ~((1 << start) - 1);
703 len = ffs(map) - 1 - start;
704 return (len > count ? count : len);
706 len = N_INUSEBITS - start;
709 while (++idx <= max_idx) {
712 map = pmp->pm_inusemap[idx];
719 return (len > count ? count : len);
723 * Allocate contigous free clusters.
726 * start - start of cluster chain.
727 * count - number of clusters to allocate.
728 * fillwith - put this value into the fat entry for the
729 * last allocated cluster.
730 * retcluster - put the first allocated cluster's number here.
731 * got - how many clusters were actually allocated.
734 chainalloc(pmp, start, count, fillwith, retcluster, got)
735 struct msdosfsmount *pmp;
745 for (cl = start, n = count; n-- > 0;)
746 usemap_alloc(pmp, cl++);
748 error = fatchain(pmp, start, count, fillwith);
752 printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n",
763 * Allocate contiguous free clusters.
766 * start - preferred start of cluster chain.
767 * count - number of clusters requested.
768 * fillwith - put this value into the fat entry for the
769 * last allocated cluster.
770 * retcluster - put the first allocated cluster's number here.
771 * got - how many clusters were actually allocated.
774 clusteralloc(pmp, start, count, fillwith, retcluster, got)
775 struct msdosfsmount *pmp;
783 u_long len, newst, foundl, cn, l;
784 u_long foundcn = 0; /* XXX: foundcn could be used unititialized */
788 printf("clusteralloc(): find %lu clusters\n",count);
791 if ((len = chainlength(pmp, start, count)) >= count)
792 return (chainalloc(pmp, start, count, fillwith, retcluster, got));
797 * Start at a (pseudo) random place to maximize cluster runs
798 * under multiple writers.
800 newst = random() % (pmp->pm_maxcluster + 1);
803 for (cn = newst; cn <= pmp->pm_maxcluster;) {
804 idx = cn / N_INUSEBITS;
805 map = pmp->pm_inusemap[idx];
806 map |= (1 << (cn % N_INUSEBITS)) - 1;
807 if (map != (u_int)-1) {
808 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
809 if ((l = chainlength(pmp, cn, count)) >= count)
810 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
818 cn += N_INUSEBITS - cn % N_INUSEBITS;
820 for (cn = 0; cn < newst;) {
821 idx = cn / N_INUSEBITS;
822 map = pmp->pm_inusemap[idx];
823 map |= (1 << (cn % N_INUSEBITS)) - 1;
824 if (map != (u_int)-1) {
825 cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
826 if ((l = chainlength(pmp, cn, count)) >= count)
827 return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
835 cn += N_INUSEBITS - cn % N_INUSEBITS;
842 return (chainalloc(pmp, start, len, fillwith, retcluster, got));
844 return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
849 * Free a chain of clusters.
851 * pmp - address of the msdosfs mount structure for the filesystem
852 * containing the cluster chain to be freed.
853 * startcluster - number of the 1st cluster in the chain of clusters to be
857 freeclusterchain(pmp, cluster)
858 struct msdosfsmount *pmp;
862 struct buf *bp = NULL;
863 u_long bn, bo, bsize, byteoffset;
864 u_long readcn, lbn = -1;
866 while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
867 byteoffset = FATOFS(pmp, cluster);
868 fatblock(pmp, byteoffset, &bn, &bsize, &bo);
871 updatefats(pmp, bp, lbn);
872 error = bread(pmp->pm_devvp, bn, bsize, &bp);
879 usemap_free(pmp, cluster);
880 switch (pmp->pm_fatmask) {
882 readcn = getushort(&bp->b_data[bo]);
884 cluster = readcn >> 4;
886 readcn |= MSDOSFSFREE << 4;
890 readcn |= MSDOSFSFREE & 0xfff;
892 putushort(&bp->b_data[bo], readcn);
895 cluster = getushort(&bp->b_data[bo]);
896 putushort(&bp->b_data[bo], MSDOSFSFREE);
899 cluster = getulong(&bp->b_data[bo]);
900 putulong(&bp->b_data[bo],
901 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
904 cluster &= pmp->pm_fatmask;
905 if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
906 cluster |= pmp->pm_fatmask;
909 updatefats(pmp, bp, bn);
914 * Read in fat blocks looking for free clusters. For every free cluster
915 * found turn off its corresponding bit in the pm_inusemap.
919 struct msdosfsmount *pmp;
921 struct buf *bp = NULL;
924 u_long bn, bo, bsize, byteoffset;
927 * Mark all clusters in use, we mark the free ones in the fat scan
930 for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
931 pmp->pm_inusemap[cn] = (u_int)-1;
934 * Figure how many free clusters are in the filesystem by ripping
935 * through the fat counting the number of entries whose content is
936 * zero. These represent free clusters.
938 pmp->pm_freeclustercount = 0;
939 for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
940 byteoffset = FATOFS(pmp, cn);
941 bo = byteoffset % pmp->pm_fatblocksize;
943 /* Read new FAT block */
946 fatblock(pmp, byteoffset, &bn, &bsize, NULL);
947 error = bread(pmp->pm_devvp, bn, bsize, &bp);
954 readcn = getulong(&bp->b_data[bo]);
956 readcn = getushort(&bp->b_data[bo]);
957 if (FAT12(pmp) && (cn & 1))
959 readcn &= pmp->pm_fatmask;
962 usemap_free(pmp, cn);
969 * Allocate a new cluster and chain it onto the end of the file.
971 * dep - the file to extend
972 * count - number of clusters to allocate
973 * bpp - where to return the address of the buf header for the first new
975 * ncp - where to put cluster number of the first newly allocated cluster
976 * If this pointer is 0, do not return the cluster number.
979 * NOTE: This function is not responsible for turning on the DE_UPDATE bit of
980 * the de_flag field of the denode and it does not change the de_FileSize
981 * field. This is left for the caller to do.
984 extendfile(dep, count, bpp, ncp, flags)
994 struct msdosfsmount *pmp = dep->de_pmp;
998 * Don't try to extend the root directory
1000 if (dep->de_StartCluster == MSDOSFSROOT
1001 && (dep->de_Attributes & ATTR_DIRECTORY)) {
1002 printf("extendfile(): attempt to extend root directory\n");
1007 * If the "file's last cluster" cache entry is empty, and the file
1008 * is not empty, then fill the cache entry by calling pcbmap().
1011 if (dep->de_fc[FC_LASTFC].fc_frcn == FCE_EMPTY &&
1012 dep->de_StartCluster != 0) {
1014 error = pcbmap(dep, 0xffff, 0, &cn, 0);
1015 /* we expect it to return E2BIG */
1022 * Allocate a new cluster chain and cat onto the end of the
1023 * file. * If the file is empty we make de_StartCluster point
1024 * to the new block. Note that de_StartCluster being 0 is
1025 * sufficient to be sure the file is empty since we exclude
1026 * attempts to extend the root directory above, and the root
1027 * dir is the only file with a startcluster of 0 that has
1028 * blocks allocated (sort of).
1030 if (dep->de_StartCluster == 0)
1033 cn = dep->de_fc[FC_LASTFC].fc_fsrcn + 1;
1034 error = clusteralloc(pmp, cn, count, CLUST_EOFE, &cn, &got);
1041 * Give them the filesystem relative cluster number if they want
1049 if (dep->de_StartCluster == 0) {
1050 dep->de_StartCluster = cn;
1053 error = fatentry(FAT_SET, pmp,
1054 dep->de_fc[FC_LASTFC].fc_fsrcn,
1057 clusterfree(pmp, cn, NULL);
1060 frcn = dep->de_fc[FC_LASTFC].fc_frcn + 1;
1064 * Update the "last cluster of the file" entry in the denode's fat
1067 fc_setcache(dep, FC_LASTFC, frcn + got - 1, cn + got - 1);
1069 if (flags & DE_CLEAR) {
1072 * Get the buf header for the new block of the file.
1074 if (dep->de_Attributes & ATTR_DIRECTORY)
1075 bp = getblk(pmp->pm_devvp, cntobn(pmp, cn++),
1076 pmp->pm_bpcluster, 0, 0);
1078 bp = getblk(DETOV(dep), de_cn2bn(pmp, frcn++),
1079 pmp->pm_bpcluster, 0, 0);
1081 * Do the bmap now, as in msdosfs_write
1084 de_bn2cn(pmp, bp->b_lblkno),
1085 &bp->b_blkno, 0, 0))
1087 if (bp->b_blkno == -1)
1088 panic("extendfile: pcbmap");