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1628 |
jcastillo |
/*
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* linux/fs/fat/cache.c
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*
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* Written 1992,1993 by Werner Almesberger
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*/
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#include <linux/msdos_fs.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/stat.h>
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#include "msbuffer.h"
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#if 0
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# define PRINTK(x) printk x
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#else
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# define PRINTK(x)
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#endif
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static struct fat_cache *fat_cache,cache[FAT_CACHE];
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/* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
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new_value is != -1, that FAT entry is replaced by it. */
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int fat_access(struct super_block *sb,int nr,int new_value)
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{
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struct buffer_head *bh,*bh2,*c_bh,*c_bh2;
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unsigned char *p_first,*p_last;
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int copy,first,last,next,b;
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if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters)
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return 0;
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if (MSDOS_SB(sb)->fat_bits == 32) {
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first = last = nr*4;
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} else if (MSDOS_SB(sb)->fat_bits == 16) {
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first = last = nr*2;
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} else {
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first = nr*3/2;
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last = first+1;
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}
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b = MSDOS_SB(sb)->fat_start + (first >> SECTOR_BITS);
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if (!(bh = fat_bread(sb, b))) {
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printk("bread in fat_access failed\n");
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return 0;
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}
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if ((first >> SECTOR_BITS) == (last >> SECTOR_BITS)) {
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bh2 = bh;
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} else {
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if (!(bh2 = fat_bread(sb, b+1))) {
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fat_brelse(sb, bh);
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printk("2nd bread in fat_access failed\n");
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return 0;
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}
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}
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if (MSDOS_SB(sb)->fat_bits == 32) {
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p_first = p_last = NULL; /* GCC needs that stuff */
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next = CF_LE_L(((unsigned long *) bh->b_data)[(first &
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(SECTOR_SIZE-1)) >> 2]);
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if (next >= 0xffffff7) next = -1;
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PRINTK(("fat_bread: 0x%x, nr=0x%x, first=0x%x, next=0x%d\n", b, nr, first, next));
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} else if (MSDOS_SB(sb)->fat_bits == 16) {
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p_first = p_last = NULL; /* GCC needs that stuff */
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next = CF_LE_W(((unsigned short *) bh->b_data)[(first &
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(SECTOR_SIZE-1)) >> 1]);
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if (next >= 0xfff7) next = -1;
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} else {
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p_first = &((unsigned char *) bh->b_data)[first & (SECTOR_SIZE-1)];
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p_last = &((unsigned char *) bh2->b_data)[(first+1) &
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(SECTOR_SIZE-1)];
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if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
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else next = (*p_first+(*p_last << 8)) & 0xfff;
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if (next >= 0xff7) next = -1;
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}
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if (new_value != -1) {
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if (MSDOS_SB(sb)->fat_bits == 32) {
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((unsigned long *) bh->b_data)[(first & (SECTOR_SIZE-1)) >>
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2] = CT_LE_L(new_value);
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} else if (MSDOS_SB(sb)->fat_bits == 16) {
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((unsigned short *) bh->b_data)[(first & (SECTOR_SIZE-1)) >>
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1] = CT_LE_W(new_value);
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} else {
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if (nr & 1) {
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*p_first = (*p_first & 0xf) | (new_value << 4);
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*p_last = new_value >> 4;
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}
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else {
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*p_first = new_value & 0xff;
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*p_last = (*p_last & 0xf0) | (new_value >> 8);
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}
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fat_mark_buffer_dirty(sb, bh2, 1);
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}
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fat_mark_buffer_dirty(sb, bh, 1);
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for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
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b = MSDOS_SB(sb)->fat_start + (first >> SECTOR_BITS) +
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MSDOS_SB(sb)->fat_length * copy;
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if (!(c_bh = fat_bread(sb, b)))
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break;
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memcpy(c_bh->b_data,bh->b_data,SECTOR_SIZE);
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fat_mark_buffer_dirty(sb, c_bh, 1);
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if (bh != bh2) {
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if (!(c_bh2 = fat_bread(sb, b+1))) {
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fat_brelse(sb, c_bh);
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break;
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}
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memcpy(c_bh2->b_data,bh2->b_data,SECTOR_SIZE);
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fat_brelse(sb, c_bh2);
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}
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fat_brelse(sb, c_bh);
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}
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}
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fat_brelse(sb, bh);
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if (bh != bh2)
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fat_brelse(sb, bh2);
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return next;
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}
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void cache_init(void)
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{
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static int initialized = 0;
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int count;
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if (initialized) return;
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fat_cache = &cache[0];
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for (count = 0; count < FAT_CACHE; count++) {
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cache[count].device = 0;
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cache[count].next = count == FAT_CACHE-1 ? NULL :
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&cache[count+1];
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}
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initialized = 1;
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}
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void cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
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{
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struct fat_cache *walk;
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#ifdef DEBUG
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printk("cache lookup: <%s,%d> %d (%d,%d) -> ", kdevname(inode->i_dev),
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inode->i_ino, cluster, *f_clu, *d_clu);
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#endif
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for (walk = fat_cache; walk; walk = walk->next)
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if (inode->i_dev == walk->device
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&& walk->ino == inode->i_ino
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&& walk->file_cluster <= cluster
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&& walk->file_cluster > *f_clu) {
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*d_clu = walk->disk_cluster;
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#ifdef DEBUG
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printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
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#endif
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if ((*f_clu = walk->file_cluster) == cluster) return;
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}
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#ifdef DEBUG
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printk("cache miss\n");
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#endif
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}
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#ifdef DEBUG
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static void list_cache(void)
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{
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struct fat_cache *walk;
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for (walk = fat_cache; walk; walk = walk->next) {
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if (walk->device)
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printk("<%s,%d>(%d,%d) ", kdevname(walk->device),
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walk->ino, walk->file_cluster, walk->disk_cluster);
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else printk("-- ");
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}
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printk("\n");
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}
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#endif
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void cache_add(struct inode *inode,int f_clu,int d_clu)
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{
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struct fat_cache *walk,*last;
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#ifdef DEBUG
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printk("cache add: <%s,%d> %d (%d)\n", kdevname(inode->i_dev),
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inode->i_ino, f_clu, d_clu);
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#endif
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last = NULL;
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for (walk = fat_cache; walk->next; walk = (last = walk)->next)
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if (inode->i_dev == walk->device
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&& walk->ino == inode->i_ino
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&& walk->file_cluster == f_clu) {
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if (walk->disk_cluster != d_clu) {
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printk("FAT cache corruption");
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fat_cache_inval_inode(inode);
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return;
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}
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/* update LRU */
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if (last == NULL) return;
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last->next = walk->next;
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| 198 |
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walk->next = fat_cache;
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fat_cache = walk;
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| 200 |
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#ifdef DEBUG
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list_cache();
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#endif
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return;
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| 204 |
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}
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walk->device = inode->i_dev;
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| 206 |
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walk->ino = inode->i_ino;
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| 207 |
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walk->file_cluster = f_clu;
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| 208 |
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walk->disk_cluster = d_clu;
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| 209 |
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last->next = NULL;
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| 210 |
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walk->next = fat_cache;
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| 211 |
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fat_cache = walk;
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#ifdef DEBUG
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| 213 |
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list_cache();
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#endif
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| 215 |
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}
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| 216 |
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| 217 |
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| 218 |
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/* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
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fixes itself after a while. */
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| 220 |
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| 221 |
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void fat_cache_inval_inode(struct inode *inode)
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{
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| 223 |
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struct fat_cache *walk;
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| 224 |
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| 225 |
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for (walk = fat_cache; walk; walk = walk->next)
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| 226 |
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if (walk->device == inode->i_dev
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&& walk->ino == inode->i_ino)
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| 228 |
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walk->device = 0;
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| 229 |
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}
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| 230 |
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| 231 |
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| 232 |
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void fat_cache_inval_dev(kdev_t device)
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| 233 |
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{
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| 234 |
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struct fat_cache *walk;
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| 235 |
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| 236 |
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for (walk = fat_cache; walk; walk = walk->next)
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| 237 |
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if (walk->device == device)
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| 238 |
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walk->device = 0;
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| 239 |
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}
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| 240 |
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| 241 |
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| 242 |
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int get_cluster(struct inode *inode,int cluster)
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| 243 |
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{
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| 244 |
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int nr,count;
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| 245 |
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| 246 |
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if (!(nr = MSDOS_I(inode)->i_start)) return 0;
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| 247 |
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if (!cluster) return nr;
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| 248 |
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count = 0;
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| 249 |
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for (cache_lookup(inode,cluster,&count,&nr); count < cluster;
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| 250 |
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count++) {
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| 251 |
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if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
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| 252 |
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if (!nr) return 0;
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| 253 |
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}
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| 254 |
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cache_add(inode,cluster,nr);
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| 255 |
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return nr;
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| 256 |
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}
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| 257 |
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| 258 |
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int fat_smap(struct inode *inode,int sector)
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| 259 |
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{
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| 260 |
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struct msdos_sb_info *sb;
|
| 261 |
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int cluster,offset;
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| 262 |
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| 263 |
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sb = MSDOS_SB(inode->i_sb);
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| 264 |
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if ((sb->fat_bits != 32) &&
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| 265 |
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(inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
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| 266 |
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!MSDOS_I(inode)->i_start))) {
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| 267 |
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if (sector >= sb->dir_entries >> MSDOS_DPS_BITS)
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| 268 |
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return 0;
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| 269 |
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return sector+sb->dir_start;
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| 270 |
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}
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| 271 |
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cluster = sector/sb->cluster_size;
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| 272 |
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offset = sector % sb->cluster_size;
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| 273 |
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if (!(cluster = get_cluster(inode,cluster))) return 0;
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| 274 |
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return (cluster-2)*sb->cluster_size+sb->data_start+offset;
|
| 275 |
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}
|
| 276 |
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| 277 |
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| 278 |
|
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/* Free all clusters after the skip'th cluster. Doesn't use the cache,
|
| 279 |
|
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because this way we get an additional sanity check. */
|
| 280 |
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|
| 281 |
|
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int fat_free(struct inode *inode,int skip)
|
| 282 |
|
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{
|
| 283 |
|
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int nr,last;
|
| 284 |
|
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int fat_bits;
|
| 285 |
|
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|
| 286 |
|
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if (!(nr = MSDOS_I(inode)->i_start)) return 0;
|
| 287 |
|
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last = 0;
|
| 288 |
|
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while (skip--) {
|
| 289 |
|
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last = nr;
|
| 290 |
|
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if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
|
| 291 |
|
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if (!nr) {
|
| 292 |
|
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printk("fat_free: skipped EOF\n");
|
| 293 |
|
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return -EIO;
|
| 294 |
|
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}
|
| 295 |
|
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}
|
| 296 |
|
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if (last) {
|
| 297 |
|
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fat_bits = MSDOS_SB(inode->i_sb)->fat_bits;
|
| 298 |
|
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fat_access(inode->i_sb,last,fat_bits == 12 ? EOF_FAT12 :
|
| 299 |
|
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fat_bits == 16 ? EOF_FAT16 : EOF_FAT32);
|
| 300 |
|
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} else {
|
| 301 |
|
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MSDOS_I(inode)->i_start = 0;
|
| 302 |
|
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MSDOS_I(inode)->i_logstart = 0;
|
| 303 |
|
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inode->i_dirt = 1;
|
| 304 |
|
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}
|
| 305 |
|
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lock_fat(inode->i_sb);
|
| 306 |
|
|
while (nr != -1) {
|
| 307 |
|
|
if (!(nr = fat_access(inode->i_sb,nr,0))) {
|
| 308 |
|
|
fat_fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
|
| 309 |
|
|
break;
|
| 310 |
|
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}
|
| 311 |
|
|
if (MSDOS_SB(inode->i_sb)->free_clusters != -1) {
|
| 312 |
|
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MSDOS_SB(inode->i_sb)->free_clusters++;
|
| 313 |
|
|
if (MSDOS_SB(inode->i_sb)->fat_bits == 32) {
|
| 314 |
|
|
fat_clusters_flush(inode->i_sb);
|
| 315 |
|
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}
|
| 316 |
|
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}
|
| 317 |
|
|
inode->i_blocks -= MSDOS_SB(inode->i_sb)->cluster_size;
|
| 318 |
|
|
}
|
| 319 |
|
|
unlock_fat(inode->i_sb);
|
| 320 |
|
|
fat_cache_inval_inode(inode);
|
| 321 |
|
|
return 0;
|
| 322 |
|
|
}
|
