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/*
* linux/fs/fat/cache.c
*
* Written 1992,1993 by Werner Almesberger
*
* Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
* of inode number.
* May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
*/
#include <linux/msdos_fs.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/fat_cvf.h>
#if 0
# define PRINTK(x) printk x
#else
# define PRINTK(x)
#endif
static struct fat_cache *fat_cache,cache[FAT_CACHE];
static spinlock_t fat_cache_lock = SPIN_LOCK_UNLOCKED;
/* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
new_value is != -1, that FAT entry is replaced by it. */
int fat_access(struct super_block *sb,int nr,int new_value)
{
return MSDOS_SB(sb)->cvf_format->fat_access(sb,nr,new_value);
}
int fat_bmap(struct inode *inode,int sector)
{
return MSDOS_SB(inode->i_sb)->cvf_format->cvf_bmap(inode,sector);
}
int default_fat_access(struct super_block *sb,int nr,int new_value)
{
struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
unsigned char *p_first, *p_last;
int copy, first, last, next, b;
if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters)
return 0;
if (MSDOS_SB(sb)->fat_bits == 32) {
first = last = nr*4;
} else if (MSDOS_SB(sb)->fat_bits == 16) {
first = last = nr*2;
} else {
first = nr*3/2;
last = first+1;
}
b = MSDOS_SB(sb)->fat_start + (first >> sb->s_blocksize_bits);
if (!(bh = fat_bread(sb, b))) {
printk("bread in fat_access failed\n");
return 0;
}
if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
bh2 = bh;
} else {
if (!(bh2 = fat_bread(sb, b+1))) {
fat_brelse(sb, bh);
printk("2nd bread in fat_access failed\n");
return 0;
}
}
if (MSDOS_SB(sb)->fat_bits == 32) {
p_first = p_last = NULL; /* GCC needs that stuff */
next = CF_LE_L(((__u32 *) bh->b_data)[(first &
(sb->s_blocksize - 1)) >> 2]);
/* Fscking Microsoft marketing department. Their "32" is 28. */
next &= 0xfffffff;
if (next >= 0xffffff7) next = -1;
PRINTK(("fat_bread: 0x%x, nr=0x%x, first=0x%x, next=0x%x\n", b, nr, first, next));
} else if (MSDOS_SB(sb)->fat_bits == 16) {
p_first = p_last = NULL; /* GCC needs that stuff */
next = CF_LE_W(((__u16 *) bh->b_data)[(first &
(sb->s_blocksize - 1)) >> 1]);
if (next >= 0xfff7) next = -1;
} else {
p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
else next = (*p_first+(*p_last << 8)) & 0xfff;
if (next >= 0xff7) next = -1;
}
if (new_value != -1) {
if (MSDOS_SB(sb)->fat_bits == 32) {
((__u32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
= CT_LE_L(new_value);
} else if (MSDOS_SB(sb)->fat_bits == 16) {
((__u16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
= CT_LE_W(new_value);
} else {
if (nr & 1) {
*p_first = (*p_first & 0xf) | (new_value << 4);
*p_last = new_value >> 4;
}
else {
*p_first = new_value & 0xff;
*p_last = (*p_last & 0xf0) | (new_value >> 8);
}
fat_mark_buffer_dirty(sb, bh2);
}
fat_mark_buffer_dirty(sb, bh);
for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
b = MSDOS_SB(sb)->fat_start + (first >> sb->s_blocksize_bits)
+ MSDOS_SB(sb)->fat_length * copy;
if (!(c_bh = fat_bread(sb, b)))
break;
if (bh != bh2) {
if (!(c_bh2 = fat_bread(sb, b+1))) {
fat_brelse(sb, c_bh);
break;
}
memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
fat_mark_buffer_dirty(sb, c_bh2);
fat_brelse(sb, c_bh2);
}
memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
fat_mark_buffer_dirty(sb, c_bh);
fat_brelse(sb, c_bh);
}
}
fat_brelse(sb, bh);
if (bh != bh2)
fat_brelse(sb, bh2);
return next;
}
void fat_cache_init(void)
{
static int initialized = 0;
int count;
spin_lock(&fat_cache_lock);
if (initialized) {
spin_unlock(&fat_cache_lock);
return;
}
fat_cache = &cache[0];
for (count = 0; count < FAT_CACHE; count++) {
cache[count].device = 0;
cache[count].next = count == FAT_CACHE-1 ? NULL :
&cache[count+1];
}
initialized = 1;
spin_unlock(&fat_cache_lock);
}
void fat_cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
{
struct fat_cache *walk;
int first = MSDOS_I(inode)->i_start;
if (!first)
return;
spin_lock(&fat_cache_lock);
for (walk = fat_cache; walk; walk = walk->next)
if (inode->i_dev == walk->device
&& walk->start_cluster == first
&& walk->file_cluster <= cluster
&& walk->file_cluster > *f_clu) {
*d_clu = walk->disk_cluster;
#ifdef DEBUG
printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
#endif
if ((*f_clu = walk->file_cluster) == cluster) {
spin_unlock(&fat_cache_lock);
return;
}
}
spin_unlock(&fat_cache_lock);
#ifdef DEBUG
printk("cache miss\n");
#endif
}
#ifdef DEBUG
static void list_cache(void)
{
struct fat_cache *walk;
for (walk = fat_cache; walk; walk = walk->next) {
if (walk->device)
printk("<%s,%d>(%d,%d) ", kdevname(walk->device),
walk->start_cluster, walk->file_cluster,
walk->disk_cluster);
else printk("-- ");
}
printk("\n");
}
#endif
void fat_cache_add(struct inode *inode,int f_clu,int d_clu)
{
struct fat_cache *walk,*last;
int first = MSDOS_I(inode)->i_start;
last = NULL;
spin_lock(&fat_cache_lock);
for (walk = fat_cache; walk->next; walk = (last = walk)->next)
if (inode->i_dev == walk->device
&& walk->start_cluster == first
&& walk->file_cluster == f_clu) {
if (walk->disk_cluster != d_clu) {
printk("FAT cache corruption inode=%ld\n",
inode->i_ino);
spin_unlock(&fat_cache_lock);
fat_cache_inval_inode(inode);
return;
}
/* update LRU */
if (last == NULL) {
spin_unlock(&fat_cache_lock);
return;
}
last->next = walk->next;
walk->next = fat_cache;
fat_cache = walk;
#ifdef DEBUG
list_cache();
#endif
spin_unlock(&fat_cache_lock);
return;
}
walk->device = inode->i_dev;
walk->start_cluster = first;
walk->file_cluster = f_clu;
walk->disk_cluster = d_clu;
last->next = NULL;
walk->next = fat_cache;
fat_cache = walk;
spin_unlock(&fat_cache_lock);
#ifdef DEBUG
list_cache();
#endif
}
/* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
fixes itself after a while. */
void fat_cache_inval_inode(struct inode *inode)
{
struct fat_cache *walk;
int first = MSDOS_I(inode)->i_start;
spin_lock(&fat_cache_lock);
for (walk = fat_cache; walk; walk = walk->next)
if (walk->device == inode->i_dev
&& walk->start_cluster == first)
walk->device = 0;
spin_unlock(&fat_cache_lock);
}
void fat_cache_inval_dev(kdev_t device)
{
struct fat_cache *walk;
spin_lock(&fat_cache_lock);
for (walk = fat_cache; walk; walk = walk->next)
if (walk->device == device)
walk->device = 0;
spin_unlock(&fat_cache_lock);
}
int fat_get_cluster(struct inode *inode,int cluster)
{
int nr,count;
if (!(nr = MSDOS_I(inode)->i_start)) return 0;
if (!cluster) return nr;
count = 0;
for (fat_cache_lookup(inode,cluster,&count,&nr); count < cluster;
count++) {
if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
if (!nr) return 0;
}
fat_cache_add(inode,cluster,nr);
return nr;
}
int default_fat_bmap(struct inode *inode,int sector)
{
struct super_block *sb = inode->i_sb;
struct msdos_sb_info *sbi = MSDOS_SB(sb);
int cluster, offset, last_block;
if ((sbi->fat_bits != 32) &&
(inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
!MSDOS_I(inode)->i_start))) {
if (sector >= sbi->dir_entries >> sbi->dir_per_block_bits)
return 0;
return sector + sbi->dir_start;
}
last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
>> sb->s_blocksize_bits;
if (sector >= last_block)
return 0;
cluster = sector / sbi->cluster_size;
offset = sector % sbi->cluster_size;
if (!(cluster = fat_get_cluster(inode, cluster)))
return 0;
return (cluster - 2) * sbi->cluster_size + sbi->data_start + offset;
}
/* Free all clusters after the skip'th cluster. Doesn't use the cache,
because this way we get an additional sanity check. */
int fat_free(struct inode *inode,int skip)
{
int nr,last;
if (!(nr = MSDOS_I(inode)->i_start)) return 0;
last = 0;
while (skip--) {
last = nr;
if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
if (!nr) {
printk("fat_free: skipped EOF\n");
return -EIO;
}
}
if (last) {
fat_access(inode->i_sb,last,EOF_FAT(inode->i_sb));
fat_cache_inval_inode(inode);
} else {
fat_cache_inval_inode(inode);
MSDOS_I(inode)->i_start = 0;
MSDOS_I(inode)->i_logstart = 0;
mark_inode_dirty(inode);
}
lock_fat(inode->i_sb);
while (nr != -1) {
if (!(nr = fat_access(inode->i_sb,nr,0))) {
fat_fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
break;
}
if (MSDOS_SB(inode->i_sb)->free_clusters != -1) {
MSDOS_SB(inode->i_sb)->free_clusters++;
if (MSDOS_SB(inode->i_sb)->fat_bits == 32) {
fat_clusters_flush(inode->i_sb);
}
}
inode->i_blocks -= (1 << MSDOS_SB(inode->i_sb)->cluster_bits) / 512;
}
unlock_fat(inode->i_sb);
return 0;
}
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