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msdosfs_fat.c
1132 lines (1047 loc) · 28.4 KB
/
msdosfs_fat.c
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/* $NetBSD: msdosfs_fat.c,v 1.14 2007/04/29 20:23:36 msaitoh Exp $ */
/*-
* Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
* Copyright (C) 1994, 1995, 1997 TooLs GmbH.
* All rights reserved.
* Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by TooLs GmbH.
* 4. The name of TooLs GmbH may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Written by Paul Popelka (paulp@uts.amdahl.com)
*
* You can do anything you want with this software, just don't say you wrote
* it, and don't remove this notice.
*
* This software is provided "as is".
*
* The author supplies this software to be publicly redistributed on the
* understanding that the author is not responsible for the correct
* functioning of this software in any circumstances and is not liable for
* any damages caused by this software.
*
* October 1992
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: msdosfs_fat.c,v 1.14 2007/04/29 20:23:36 msaitoh Exp $");
/*
* kernel include files.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/namei.h>
#include <sys/mount.h> /* to define statvfs structure */
#include <sys/vnode.h> /* to define vattr structure */
#include <sys/errno.h>
#include <sys/dirent.h>
#include <sys/kauth.h>
/*
* msdosfs include files.
*/
#include <fs/msdosfs/bpb.h>
#include <fs/msdosfs/msdosfsmount.h>
#include <fs/msdosfs/direntry.h>
#include <fs/msdosfs/denode.h>
#include <fs/msdosfs/fat.h>
/*
* Fat cache stats.
*/
int fc_fileextends; /* # of file extends */
int fc_lfcempty; /* # of time last file cluster cache entry
* was empty */
int fc_bmapcalls; /* # of times pcbmap was called */
#define LMMAX 20
int fc_lmdistance[LMMAX]; /* counters for how far off the last
* cluster mapped entry was. */
int fc_largedistance; /* off by more than LMMAX */
int fc_wherefrom, fc_whereto, fc_lastclust;
int pm_fatblocksize;
#ifdef MSDOSFS_DEBUG
void print_fat_stats(void);
void
print_fat_stats(void)
{
int i;
printf("fc_fileextends=%d fc_lfcempty=%d fc_bmapcalls=%d "
"fc_largedistance=%d [%d->%d=%d] fc_lastclust=%d pm_fatblocksize=%d\n",
fc_fileextends, fc_lfcempty, fc_bmapcalls, fc_largedistance,
fc_wherefrom, fc_whereto, fc_whereto-fc_wherefrom,
fc_lastclust, pm_fatblocksize);
fc_fileextends = fc_lfcempty = fc_bmapcalls = 0;
fc_wherefrom = fc_whereto = fc_lastclust = 0;
for (i = 0; i < LMMAX; i++) {
printf("%d:%d ", i, fc_lmdistance[i]);
fc_lmdistance[i] = 0;
}
printf("\n");
}
#endif
static void fatblock(struct msdosfsmount *, u_long, u_long *, u_long *,
u_long *);
void updatefats(struct msdosfsmount *, struct buf *, u_long);
static inline void usemap_free(struct msdosfsmount *, u_long);
static inline void usemap_alloc(struct msdosfsmount *, u_long);
static int fatchain(struct msdosfsmount *, u_long, u_long, u_long);
int chainlength(struct msdosfsmount *, u_long, u_long);
int chainalloc(struct msdosfsmount *, u_long, u_long, u_long, u_long *,
u_long *);
static void
fatblock(pmp, ofs, bnp, sizep, bop)
struct msdosfsmount *pmp;
u_long ofs;
u_long *bnp;
u_long *sizep;
u_long *bop;
{
u_long bn, size;
bn = ofs / pmp->pm_fatblocksize * pmp->pm_fatblocksec;
size = min(pmp->pm_fatblocksec, pmp->pm_FATsecs - bn)
* pmp->pm_BytesPerSec;
bn += pmp->pm_fatblk + pmp->pm_curfat * pmp->pm_FATsecs;
if (bnp)
*bnp = bn;
if (sizep)
*sizep = size;
if (bop)
*bop = ofs % pmp->pm_fatblocksize;
pm_fatblocksize = pmp->pm_fatblocksize;
}
/*
* Map the logical cluster number of a file into a physical disk sector
* that is filesystem relative.
*
* dep - address of denode representing the file of interest
* findcn - file relative cluster whose filesystem relative cluster number
* and/or block number are/is to be found
* bnp - address of where to place the file system relative block number.
* If this pointer is null then don't return this quantity.
* cnp - address of where to place the file system relative cluster number.
* If this pointer is null then don't return this quantity.
*
* NOTE: Either bnp or cnp must be non-null.
* This function has one side effect. If the requested file relative cluster
* is beyond the end of file, then the actual number of clusters in the file
* is returned in *cnp. This is useful for determining how long a directory is.
* If cnp is null, nothing is returned.
*/
int
pcbmap(dep, findcn, bnp, cnp, sp)
struct denode *dep;
u_long findcn; /* file relative cluster to get */
daddr_t *bnp; /* returned filesys rel sector number */
u_long *cnp; /* returned cluster number */
int *sp; /* returned block size */
{
int error;
u_long i;
u_long cn;
u_long prevcn = 0; /* XXX: prevcn could be used unititialized */
u_long byteoffset;
u_long bn;
u_long bo;
struct buf *bp = NULL;
u_long bp_bn = -1;
struct msdosfsmount *pmp = dep->de_pmp;
u_long bsize;
fc_bmapcalls++;
/*
* If they don't give us someplace to return a value then don't
* bother doing anything.
*/
if (bnp == NULL && cnp == NULL && sp == NULL)
return (0);
cn = dep->de_StartCluster;
/*
* The "file" that makes up the root directory is contiguous,
* permanently allocated, of fixed size, and is not made up of
* clusters. If the cluster number is beyond the end of the root
* directory, then return the number of clusters in the file.
*/
if (cn == MSDOSFSROOT) {
if (dep->de_Attributes & ATTR_DIRECTORY) {
if (de_cn2off(pmp, findcn) >= dep->de_FileSize) {
if (cnp)
*cnp = de_bn2cn(pmp, pmp->pm_rootdirsize);
return (E2BIG);
}
if (bnp)
*bnp = pmp->pm_rootdirblk + de_cn2bn(pmp, findcn);
if (cnp)
*cnp = MSDOSFSROOT;
if (sp)
*sp = min(pmp->pm_bpcluster,
dep->de_FileSize - de_cn2off(pmp, findcn));
return (0);
} else { /* just an empty file */
if (cnp)
*cnp = 0;
return (E2BIG);
}
}
/*
* All other files do I/O in cluster sized blocks
*/
if (sp)
*sp = pmp->pm_bpcluster;
/*
* Rummage around in the fat cache, maybe we can avoid tromping
* thru every fat entry for the file. And, keep track of how far
* off the cache was from where we wanted to be.
*/
i = 0;
fc_lookup(dep, findcn, &i, &cn);
if ((bn = findcn - i) >= LMMAX) {
fc_largedistance++;
fc_wherefrom = i;
fc_whereto = findcn;
fc_lastclust = dep->de_fc[FC_LASTFC].fc_frcn;
} else
fc_lmdistance[bn]++;
/*
* Handle all other files or directories the normal way.
*/
for (; i < findcn; i++) {
/*
* Stop with all reserved clusters, not just with EOF.
*/
if (cn >= (CLUST_RSRVD & pmp->pm_fatmask))
goto hiteof;
byteoffset = FATOFS(pmp, cn);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
if (bn != bp_bn) {
if (bp)
brelse(bp);
error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
bp_bn = bn;
}
prevcn = cn;
if (bo >= bsize) {
if (bp)
brelse(bp);
return (EIO);
}
KASSERT(bp != NULL);
if (FAT32(pmp))
cn = getulong((char *)bp->b_data + bo);
else
cn = getushort((char *)bp->b_data + bo);
if (FAT12(pmp) && (prevcn & 1))
cn >>= 4;
cn &= pmp->pm_fatmask;
}
if (!MSDOSFSEOF(cn, pmp->pm_fatmask)) {
if (bp)
brelse(bp);
if (bnp)
*bnp = cntobn(pmp, cn);
if (cnp)
*cnp = cn;
fc_setcache(dep, FC_LASTMAP, i, cn);
return (0);
}
hiteof:;
if (cnp)
*cnp = i;
if (bp)
brelse(bp);
/* update last file cluster entry in the fat cache */
fc_setcache(dep, FC_LASTFC, i - 1, prevcn);
return (E2BIG);
}
/*
* Find the closest entry in the fat cache to the cluster we are looking
* for.
*/
void
fc_lookup(dep, findcn, frcnp, fsrcnp)
struct denode *dep;
u_long findcn;
u_long *frcnp;
u_long *fsrcnp;
{
int i;
u_long cn;
struct fatcache *closest = 0;
for (i = 0; i < FC_SIZE; i++) {
cn = dep->de_fc[i].fc_frcn;
if (cn != FCE_EMPTY && cn <= findcn) {
if (closest == 0 || cn > closest->fc_frcn)
closest = &dep->de_fc[i];
}
}
if (closest) {
*frcnp = closest->fc_frcn;
*fsrcnp = closest->fc_fsrcn;
}
}
/*
* Purge the fat cache in denode dep of all entries relating to file
* relative cluster frcn and beyond.
*/
void
fc_purge(dep, frcn)
struct denode *dep;
u_int frcn;
{
int i;
struct fatcache *fcp;
fcp = dep->de_fc;
for (i = 0; i < FC_SIZE; i++, fcp++) {
if (fcp->fc_frcn >= frcn)
fcp->fc_frcn = FCE_EMPTY;
}
}
/*
* Update the fat.
* If mirroring the fat, update all copies, with the first copy as last.
* Else update only the current fat (ignoring the others).
*
* pmp - msdosfsmount structure for filesystem to update
* bp - addr of modified fat block
* fatbn - block number relative to begin of filesystem of the modified fat block.
*/
void
updatefats(pmp, bp, fatbn)
struct msdosfsmount *pmp;
struct buf *bp;
u_long fatbn;
{
int i;
struct buf *bpn;
#ifdef MSDOSFS_DEBUG
printf("updatefats(pmp %p, bp %p, fatbn %lu)\n",
pmp, bp, fatbn);
#endif
/*
* If we have an FSInfo block, update it.
*/
if (pmp->pm_fsinfo) {
u_long cn = pmp->pm_nxtfree;
if (pmp->pm_freeclustercount
&& (pmp->pm_inusemap[cn / N_INUSEBITS]
& (1 << (cn % N_INUSEBITS)))) {
/*
* The cluster indicated in FSInfo isn't free
* any longer. Got get a new free one.
*/
for (cn = 0; cn < pmp->pm_maxcluster; cn++)
if (pmp->pm_inusemap[cn / N_INUSEBITS] != (u_int)-1)
break;
pmp->pm_nxtfree = cn
+ ffs(pmp->pm_inusemap[cn / N_INUSEBITS]
^ (u_int)-1) - 1;
}
/*
* XXX If the fsinfo block is stored on media with
* 2KB or larger sectors, is the fsinfo structure
* padded at the end or in the middle?
*/
if (bread(pmp->pm_devvp, de_bn2kb(pmp, pmp->pm_fsinfo),
pmp->pm_BytesPerSec, NOCRED, &bpn) != 0) {
/*
* Ignore the error, but turn off FSInfo update for the future.
*/
pmp->pm_fsinfo = 0;
brelse(bpn);
} else {
struct fsinfo *fp = (struct fsinfo *)bpn->b_data;
putulong(fp->fsinfree, pmp->pm_freeclustercount);
putulong(fp->fsinxtfree, pmp->pm_nxtfree);
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bpn);
else
bdwrite(bpn);
}
}
if (pmp->pm_flags & MSDOSFS_FATMIRROR) {
/*
* Now copy the block(s) of the modified fat to the other copies of
* the fat and write them out. This is faster than reading in the
* other fats and then writing them back out. This could tie up
* the fat for quite a while. Preventing others from accessing it.
* To prevent us from going after the fat quite so much we use
* delayed writes, unless they specified "synchronous" when the
* filesystem was mounted. If synch is asked for then use
* bwrite()'s and really slow things down.
*/
for (i = 1; i < pmp->pm_FATs; i++) {
fatbn += pmp->pm_FATsecs;
/* getblk() never fails */
bpn = getblk(pmp->pm_devvp, de_bn2kb(pmp, fatbn),
bp->b_bcount, 0, 0);
memcpy(bpn->b_data, bp->b_data, bp->b_bcount);
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bpn);
else
bdwrite(bpn);
}
}
/*
* Write out the first (or current) fat last.
*/
if (pmp->pm_flags & MSDOSFSMNT_WAITONFAT)
bwrite(bp);
else
bdwrite(bp);
/*
* Maybe update fsinfo sector here?
*/
}
/*
* Updating entries in 12 bit fats is a pain in the butt.
*
* The following picture shows where nibbles go when moving from a 12 bit
* cluster number into the appropriate bytes in the FAT.
*
* byte m byte m+1 byte m+2
* +----+----+ +----+----+ +----+----+
* | 0 1 | | 2 3 | | 4 5 | FAT bytes
* +----+----+ +----+----+ +----+----+
*
* +----+----+----+ +----+----+----+
* | 3 0 1 | | 4 5 2 |
* +----+----+----+ +----+----+----+
* cluster n cluster n+1
*
* Where n is even. m = n + (n >> 2)
*
*/
static inline void
usemap_alloc(pmp, cn)
struct msdosfsmount *pmp;
u_long cn;
{
pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
pmp->pm_freeclustercount--;
}
static inline void
usemap_free(pmp, cn)
struct msdosfsmount *pmp;
u_long cn;
{
pmp->pm_freeclustercount++;
pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
}
int
clusterfree(pmp, cluster, oldcnp)
struct msdosfsmount *pmp;
u_long cluster;
u_long *oldcnp;
{
int error;
u_long oldcn;
usemap_free(pmp, cluster);
error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
if (error) {
usemap_alloc(pmp, cluster);
return (error);
}
/*
* If the cluster was successfully marked free, then update
* the count of free clusters, and turn off the "allocated"
* bit in the "in use" cluster bit map.
*/
if (oldcnp)
*oldcnp = oldcn;
return (0);
}
/*
* Get or Set or 'Get and Set' the cluster'th entry in the fat.
*
* function - whether to get or set a fat entry
* pmp - address of the msdosfsmount structure for the filesystem
* whose fat is to be manipulated.
* cn - which cluster is of interest
* oldcontents - address of a word that is to receive the contents of the
* cluster'th entry if this is a get function
* newcontents - the new value to be written into the cluster'th element of
* the fat if this is a set function.
*
* This function can also be used to free a cluster by setting the fat entry
* for a cluster to 0.
*
* All copies of the fat are updated if this is a set function. NOTE: If
* fatentry() marks a cluster as free it does not update the inusemap in
* the msdosfsmount structure. This is left to the caller.
*/
int
fatentry(function, pmp, cn, oldcontents, newcontents)
int function;
struct msdosfsmount *pmp;
u_long cn;
u_long *oldcontents;
u_long newcontents;
{
int error;
u_long readcn;
u_long bn, bo, bsize, byteoffset;
struct buf *bp;
#ifdef MSDOSFS_DEBUG
printf("fatentry(func %d, pmp %p, clust %lu, oldcon %p, newcon %lx)\n",
function, pmp, cn, oldcontents, newcontents);
#endif
#ifdef DIAGNOSTIC
/*
* Be sure they asked us to do something.
*/
if ((function & (FAT_SET | FAT_GET)) == 0) {
printf("fatentry(): function code doesn't specify get or set\n");
return (EINVAL);
}
/*
* If they asked us to return a cluster number but didn't tell us
* where to put it, give them an error.
*/
if ((function & FAT_GET) && oldcontents == NULL) {
printf("fatentry(): get function with no place to put result\n");
return (EINVAL);
}
#endif
/*
* Be sure the requested cluster is in the filesystem.
*/
if (cn < CLUST_FIRST || cn > pmp->pm_maxcluster)
return (EINVAL);
byteoffset = FATOFS(pmp, cn);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, NOCRED,
&bp)) != 0) {
brelse(bp);
return (error);
}
if (function & FAT_GET) {
if (FAT32(pmp))
readcn = getulong((char *)bp->b_data + bo);
else
readcn = getushort((char *)bp->b_data + bo);
if (FAT12(pmp) & (cn & 1))
readcn >>= 4;
readcn &= pmp->pm_fatmask;
*oldcontents = readcn;
}
if (function & FAT_SET) {
switch (pmp->pm_fatmask) {
case FAT12_MASK:
readcn = getushort((char *)bp->b_data + bo);
if (cn & 1) {
readcn &= 0x000f;
readcn |= newcontents << 4;
} else {
readcn &= 0xf000;
readcn |= newcontents & 0xfff;
}
putushort((char *)bp->b_data + bo, readcn);
break;
case FAT16_MASK:
putushort((char *)bp->b_data + bo, newcontents);
break;
case FAT32_MASK:
/*
* According to spec we have to retain the
* high order bits of the fat entry.
*/
readcn = getulong((char *)bp->b_data + bo);
readcn &= ~FAT32_MASK;
readcn |= newcontents & FAT32_MASK;
putulong((char *)bp->b_data + bo, readcn);
break;
}
updatefats(pmp, bp, bn);
bp = NULL;
pmp->pm_fmod = 1;
}
if (bp)
brelse(bp);
return (0);
}
/*
* Update a contiguous cluster chain
*
* pmp - mount point
* start - first cluster of chain
* count - number of clusters in chain
* fillwith - what to write into fat entry of last cluster
*/
static int
fatchain(pmp, start, count, fillwith)
struct msdosfsmount *pmp;
u_long start;
u_long count;
u_long fillwith;
{
int error;
u_long bn, bo, bsize, byteoffset, readcn, newc;
struct buf *bp;
#ifdef MSDOSFS_DEBUG
printf("fatchain(pmp %p, start %lu, count %lu, fillwith %lx)\n",
pmp, start, count, fillwith);
#endif
/*
* Be sure the clusters are in the filesystem.
*/
if (start < CLUST_FIRST || start + count - 1 > pmp->pm_maxcluster)
return (EINVAL);
while (count > 0) {
byteoffset = FATOFS(pmp, start);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize, NOCRED,
&bp);
if (error) {
brelse(bp);
return (error);
}
while (count > 0) {
start++;
newc = --count > 0 ? start : fillwith;
switch (pmp->pm_fatmask) {
case FAT12_MASK:
readcn = getushort((char *)bp->b_data + bo);
if (start & 1) {
readcn &= 0xf000;
readcn |= newc & 0xfff;
} else {
readcn &= 0x000f;
readcn |= newc << 4;
}
putushort((char *)bp->b_data + bo, readcn);
bo++;
if (!(start & 1))
bo++;
break;
case FAT16_MASK:
putushort((char *)bp->b_data + bo, newc);
bo += 2;
break;
case FAT32_MASK:
readcn = getulong((char *)bp->b_data + bo);
readcn &= ~pmp->pm_fatmask;
readcn |= newc & pmp->pm_fatmask;
putulong((char *)bp->b_data + bo, readcn);
bo += 4;
break;
}
if (bo >= bsize)
break;
}
updatefats(pmp, bp, bn);
}
pmp->pm_fmod = 1;
return (0);
}
/*
* Check the length of a free cluster chain starting at start.
*
* pmp - mount point
* start - start of chain
* count - maximum interesting length
*/
int
chainlength(pmp, start, count)
struct msdosfsmount *pmp;
u_long start;
u_long count;
{
u_long idx, max_idx;
u_int map;
u_long len;
max_idx = pmp->pm_maxcluster / N_INUSEBITS;
idx = start / N_INUSEBITS;
start %= N_INUSEBITS;
map = pmp->pm_inusemap[idx];
map &= ~((1 << start) - 1);
if (map) {
len = ffs(map) - 1 - start;
return (len > count ? count : len);
}
len = N_INUSEBITS - start;
if (len >= count)
return (count);
while (++idx <= max_idx) {
if (len >= count)
break;
if ((map = pmp->pm_inusemap[idx]) != 0) {
len += ffs(map) - 1;
break;
}
len += N_INUSEBITS;
}
return (len > count ? count : len);
}
/*
* Allocate contigous free clusters.
*
* pmp - mount point.
* start - start of cluster chain.
* count - number of clusters to allocate.
* fillwith - put this value into the fat entry for the
* last allocated cluster.
* retcluster - put the first allocated cluster's number here.
* got - how many clusters were actually allocated.
*/
int
chainalloc(pmp, start, count, fillwith, retcluster, got)
struct msdosfsmount *pmp;
u_long start;
u_long count;
u_long fillwith;
u_long *retcluster;
u_long *got;
{
int error;
u_long cl, n;
for (cl = start, n = count; n-- > 0;)
usemap_alloc(pmp, cl++);
if ((error = fatchain(pmp, start, count, fillwith)) != 0)
return (error);
#ifdef MSDOSFS_DEBUG
printf("clusteralloc(): allocated cluster chain at %lu (%lu clusters)\n",
start, count);
#endif
if (retcluster)
*retcluster = start;
if (got)
*got = count;
return (0);
}
/*
* Allocate contiguous free clusters.
*
* pmp - mount point.
* start - preferred start of cluster chain.
* count - number of clusters requested.
* fillwith - put this value into the fat entry for the
* last allocated cluster.
* retcluster - put the first allocated cluster's number here.
* got - how many clusters were actually allocated.
*/
int
clusteralloc(pmp, start, count, retcluster, got)
struct msdosfsmount *pmp;
u_long start;
u_long count;
u_long *retcluster;
u_long *got;
{
u_long idx;
u_long len, newst, foundl, cn, l;
u_long foundcn = 0; /* XXX: foundcn could be used unititialized */
u_long fillwith = CLUST_EOFE;
u_int map;
#ifdef MSDOSFS_DEBUG
printf("clusteralloc(): find %lu clusters\n",count);
#endif
if (start) {
if ((len = chainlength(pmp, start, count)) >= count)
return (chainalloc(pmp, start, count, fillwith, retcluster, got));
} else {
/*
* This is a new file, initialize start
*/
struct timeval tv;
microtime(&tv);
start = (tv.tv_usec >> 10) | tv.tv_usec;
len = 0;
}
/*
* Start at a (pseudo) random place to maximize cluster runs
* under multiple writers.
*/
newst = (start * 1103515245 + 12345) % (pmp->pm_maxcluster + 1);
foundl = 0;
for (cn = newst; cn <= pmp->pm_maxcluster;) {
idx = cn / N_INUSEBITS;
map = pmp->pm_inusemap[idx];
map |= (1 << (cn % N_INUSEBITS)) - 1;
if (map != (u_int)-1) {
cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
if ((l = chainlength(pmp, cn, count)) >= count)
return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
if (l > foundl) {
foundcn = cn;
foundl = l;
}
cn += l + 1;
continue;
}
cn += N_INUSEBITS - cn % N_INUSEBITS;
}
for (cn = 0; cn < newst;) {
idx = cn / N_INUSEBITS;
map = pmp->pm_inusemap[idx];
map |= (1 << (cn % N_INUSEBITS)) - 1;
if (map != (u_int)-1) {
cn = idx * N_INUSEBITS + ffs(map^(u_int)-1) - 1;
if ((l = chainlength(pmp, cn, count)) >= count)
return (chainalloc(pmp, cn, count, fillwith, retcluster, got));
if (l > foundl) {
foundcn = cn;
foundl = l;
}
cn += l + 1;
continue;
}
cn += N_INUSEBITS - cn % N_INUSEBITS;
}
if (!foundl)
return (ENOSPC);
if (len)
return (chainalloc(pmp, start, len, fillwith, retcluster, got));
else
return (chainalloc(pmp, foundcn, foundl, fillwith, retcluster, got));
}
/*
* Free a chain of clusters.
*
* pmp - address of the msdosfs mount structure for the filesystem
* containing the cluster chain to be freed.
* startcluster - number of the 1st cluster in the chain of clusters to be
* freed.
*/
int
freeclusterchain(pmp, cluster)
struct msdosfsmount *pmp;
u_long cluster;
{
int error;
struct buf *bp = NULL;
u_long bn, bo, bsize, byteoffset;
u_long readcn, lbn = -1;
while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
byteoffset = FATOFS(pmp, cluster);
fatblock(pmp, byteoffset, &bn, &bsize, &bo);
if (lbn != bn) {
if (bp)
updatefats(pmp, bp, lbn);
error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
lbn = bn;
}
usemap_free(pmp, cluster);
KASSERT(bp != NULL);
switch (pmp->pm_fatmask) {
case FAT12_MASK:
readcn = getushort((char *)bp->b_data + bo);
if (cluster & 1) {
cluster = readcn >> 4;
readcn &= 0x000f;
readcn |= MSDOSFSFREE << 4;
} else {
cluster = readcn;
readcn &= 0xf000;
readcn |= MSDOSFSFREE & 0xfff;
}
putushort((char *)bp->b_data + bo, readcn);
break;
case FAT16_MASK:
cluster = getushort((char *)bp->b_data + bo);
putushort((char *)bp->b_data + bo, MSDOSFSFREE);
break;
case FAT32_MASK:
cluster = getulong((char *)bp->b_data + bo);
putulong((char *)bp->b_data + bo,
(MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
break;
}
cluster &= pmp->pm_fatmask;
}
if (bp)
updatefats(pmp, bp, bn);
return (0);
}
/*
* Read in fat blocks looking for free clusters. For every free cluster
* found turn off its corresponding bit in the pm_inusemap.
*/
int
fillinusemap(pmp)
struct msdosfsmount *pmp;
{
struct buf *bp = NULL;
u_long cn, readcn;
int error;
u_long bn, bo, bsize, byteoffset;
/*
* Mark all clusters in use, we mark the free ones in the fat scan
* loop further down.
*/
for (cn = 0; cn < (pmp->pm_maxcluster + N_INUSEBITS) / N_INUSEBITS; cn++)
pmp->pm_inusemap[cn] = (u_int)-1;
/*
* Figure how many free clusters are in the filesystem by ripping
* through the fat counting the number of entries whose content is
* zero. These represent free clusters.
*/
pmp->pm_freeclustercount = 0;
for (cn = CLUST_FIRST; cn <= pmp->pm_maxcluster; cn++) {
byteoffset = FATOFS(pmp, cn);
bo = byteoffset % pmp->pm_fatblocksize;
if (!bo || !bp) {
/* Read new FAT block */
if (bp)
brelse(bp);
fatblock(pmp, byteoffset, &bn, &bsize, NULL);
error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), bsize,
NOCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
}
if (FAT32(pmp))
readcn = getulong((char *)bp->b_data + bo);
else
readcn = getushort((char *)bp->b_data + bo);
if (FAT12(pmp) && (cn & 1))
readcn >>= 4;
readcn &= pmp->pm_fatmask;