v2.4.8 -> v2.4.8.1
[opensuse:kernel.git] / fs / fat / cache.c
1 /*
2  *  linux/fs/fat/cache.c
3  *
4  *  Written 1992,1993 by Werner Almesberger
5  *
6  *  Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
7  *      of inode number.
8  *  May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
9  */
10
11 #include <linux/msdos_fs.h>
12 #include <linux/kernel.h>
13 #include <linux/errno.h>
14 #include <linux/string.h>
15 #include <linux/stat.h>
16 #include <linux/fat_cvf.h>
17
18 #if 0
19 #  define PRINTK(x) printk x
20 #else
21 #  define PRINTK(x)
22 #endif
23
24 static struct fat_cache *fat_cache,cache[FAT_CACHE];
25 static spinlock_t fat_cache_lock = SPIN_LOCK_UNLOCKED;
26
27 /* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
28    new_value is != -1, that FAT entry is replaced by it. */
29
30 int fat_access(struct super_block *sb,int nr,int new_value)
31 {
32         return MSDOS_SB(sb)->cvf_format->fat_access(sb,nr,new_value);
33 }
34
35 int fat_bmap(struct inode *inode,int sector)
36 {
37         return MSDOS_SB(inode->i_sb)->cvf_format->cvf_bmap(inode,sector);
38 }
39
40 int default_fat_access(struct super_block *sb,int nr,int new_value)
41 {
42         struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
43         unsigned char *p_first, *p_last;
44         int copy, first, last, next, b;
45
46         if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters)
47                 return 0;
48         if (MSDOS_SB(sb)->fat_bits == 32) {
49                 first = last = nr*4;
50         } else if (MSDOS_SB(sb)->fat_bits == 16) {
51                 first = last = nr*2;
52         } else {
53                 first = nr*3/2;
54                 last = first+1;
55         }
56         b = MSDOS_SB(sb)->fat_start + (first >> sb->s_blocksize_bits);
57         if (!(bh = fat_bread(sb, b))) {
58                 printk("bread in fat_access failed\n");
59                 return 0;
60         }
61         if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
62                 bh2 = bh;
63         } else {
64                 if (!(bh2 = fat_bread(sb, b+1))) {
65                         fat_brelse(sb, bh);
66                         printk("2nd bread in fat_access failed\n");
67                         return 0;
68                 }
69         }
70         if (MSDOS_SB(sb)->fat_bits == 32) {
71                 p_first = p_last = NULL; /* GCC needs that stuff */
72                 next = CF_LE_L(((__u32 *) bh->b_data)[(first &
73                     (sb->s_blocksize - 1)) >> 2]);
74                 /* Fscking Microsoft marketing department. Their "32" is 28. */
75                 next &= 0xfffffff;
76                 if (next >= 0xffffff7) next = -1;
77                 PRINTK(("fat_bread: 0x%x, nr=0x%x, first=0x%x, next=0x%x\n", b, nr, first, next));
78
79         } else if (MSDOS_SB(sb)->fat_bits == 16) {
80                 p_first = p_last = NULL; /* GCC needs that stuff */
81                 next = CF_LE_W(((__u16 *) bh->b_data)[(first &
82                     (sb->s_blocksize - 1)) >> 1]);
83                 if (next >= 0xfff7) next = -1;
84         } else {
85                 p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
86                 p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
87                 if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
88                 else next = (*p_first+(*p_last << 8)) & 0xfff;
89                 if (next >= 0xff7) next = -1;
90         }
91         if (new_value != -1) {
92                 if (MSDOS_SB(sb)->fat_bits == 32) {
93                         ((__u32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
94                                 = CT_LE_L(new_value);
95                 } else if (MSDOS_SB(sb)->fat_bits == 16) {
96                         ((__u16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
97                                 = CT_LE_W(new_value);
98                 } else {
99                         if (nr & 1) {
100                                 *p_first = (*p_first & 0xf) | (new_value << 4);
101                                 *p_last = new_value >> 4;
102                         }
103                         else {
104                                 *p_first = new_value & 0xff;
105                                 *p_last = (*p_last & 0xf0) | (new_value >> 8);
106                         }
107                         fat_mark_buffer_dirty(sb, bh2);
108                 }
109                 fat_mark_buffer_dirty(sb, bh);
110                 for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
111                         b = MSDOS_SB(sb)->fat_start + (first >> sb->s_blocksize_bits)
112                                 + MSDOS_SB(sb)->fat_length * copy;
113                         if (!(c_bh = fat_bread(sb, b)))
114                                 break;
115                         if (bh != bh2) {
116                                 if (!(c_bh2 = fat_bread(sb, b+1))) {
117                                         fat_brelse(sb, c_bh);
118                                         break;
119                                 }
120                                 memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
121                                 fat_mark_buffer_dirty(sb, c_bh2);
122                                 fat_brelse(sb, c_bh2);
123                         }
124                         memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
125                         fat_mark_buffer_dirty(sb, c_bh);
126                         fat_brelse(sb, c_bh);
127                 }
128         }
129         fat_brelse(sb, bh);
130         if (bh != bh2)
131                 fat_brelse(sb, bh2);
132         return next;
133 }
134
135 void fat_cache_init(void)
136 {
137         static int initialized = 0;
138         int count;
139
140         spin_lock(&fat_cache_lock);
141         if (initialized) {
142                 spin_unlock(&fat_cache_lock);
143                 return;
144         }
145         fat_cache = &cache[0];
146         for (count = 0; count < FAT_CACHE; count++) {
147                 cache[count].device = 0;
148                 cache[count].next = count == FAT_CACHE-1 ? NULL :
149                     &cache[count+1];
150         }
151         initialized = 1;
152         spin_unlock(&fat_cache_lock);
153 }
154
155
156 void fat_cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
157 {
158         struct fat_cache *walk;
159         int first = MSDOS_I(inode)->i_start;
160
161         if (!first)
162                 return;
163         spin_lock(&fat_cache_lock);
164         for (walk = fat_cache; walk; walk = walk->next)
165                 if (inode->i_dev == walk->device
166                     && walk->start_cluster == first
167                     && walk->file_cluster <= cluster
168                     && walk->file_cluster > *f_clu) {
169                         *d_clu = walk->disk_cluster;
170 #ifdef DEBUG
171 printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
172 #endif
173                         if ((*f_clu = walk->file_cluster) == cluster) { 
174                                 spin_unlock(&fat_cache_lock);
175                                 return;
176                         }
177                 }
178         spin_unlock(&fat_cache_lock);
179 #ifdef DEBUG
180 printk("cache miss\n");
181 #endif
182 }
183
184
185 #ifdef DEBUG
186 static void list_cache(void)
187 {
188         struct fat_cache *walk;
189
190         for (walk = fat_cache; walk; walk = walk->next) {
191                 if (walk->device)
192                         printk("<%s,%d>(%d,%d) ", kdevname(walk->device),
193                                walk->start_cluster, walk->file_cluster,
194                                walk->disk_cluster);
195                 else printk("-- ");
196         }
197         printk("\n");
198 }
199 #endif
200
201
202 void fat_cache_add(struct inode *inode,int f_clu,int d_clu)
203 {
204         struct fat_cache *walk,*last;
205         int first = MSDOS_I(inode)->i_start;
206
207         last = NULL;
208         spin_lock(&fat_cache_lock);
209         for (walk = fat_cache; walk->next; walk = (last = walk)->next)
210                 if (inode->i_dev == walk->device
211                     && walk->start_cluster == first
212                     && walk->file_cluster == f_clu) {
213                         if (walk->disk_cluster != d_clu) {
214                                 printk("FAT cache corruption inode=%ld\n",
215                                         inode->i_ino);
216                                 spin_unlock(&fat_cache_lock);
217                                 fat_cache_inval_inode(inode);
218                                 return;
219                         }
220                         /* update LRU */
221                         if (last == NULL) {
222                                 spin_unlock(&fat_cache_lock);
223                                 return;
224                         }
225                         last->next = walk->next;
226                         walk->next = fat_cache;
227                         fat_cache = walk;
228 #ifdef DEBUG
229 list_cache();
230 #endif
231                         spin_unlock(&fat_cache_lock);
232                         return;
233                 }
234         walk->device = inode->i_dev;
235         walk->start_cluster = first;
236         walk->file_cluster = f_clu;
237         walk->disk_cluster = d_clu;
238         last->next = NULL;
239         walk->next = fat_cache;
240         fat_cache = walk;
241         spin_unlock(&fat_cache_lock);
242 #ifdef DEBUG
243 list_cache();
244 #endif
245 }
246
247
248 /* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
249    fixes itself after a while. */
250
251 void fat_cache_inval_inode(struct inode *inode)
252 {
253         struct fat_cache *walk;
254         int first = MSDOS_I(inode)->i_start;
255
256         spin_lock(&fat_cache_lock);
257         for (walk = fat_cache; walk; walk = walk->next)
258                 if (walk->device == inode->i_dev
259                     && walk->start_cluster == first)
260                         walk->device = 0;
261         spin_unlock(&fat_cache_lock);
262 }
263
264
265 void fat_cache_inval_dev(kdev_t device)
266 {
267         struct fat_cache *walk;
268
269         spin_lock(&fat_cache_lock);
270         for (walk = fat_cache; walk; walk = walk->next)
271                 if (walk->device == device)
272                         walk->device = 0;
273         spin_unlock(&fat_cache_lock);
274 }
275
276
277 int fat_get_cluster(struct inode *inode,int cluster)
278 {
279         int nr,count;
280
281         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
282         if (!cluster) return nr;
283         count = 0;
284         for (fat_cache_lookup(inode,cluster,&count,&nr); count < cluster;
285             count++) {
286                 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
287                 if (!nr) return 0;
288         }
289         fat_cache_add(inode,cluster,nr);
290         return nr;
291 }
292
293 int default_fat_bmap(struct inode *inode,int sector)
294 {
295         struct super_block *sb = inode->i_sb;
296         struct msdos_sb_info *sbi = MSDOS_SB(sb);
297         int cluster, offset, last_block;
298
299         if ((sbi->fat_bits != 32) &&
300             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
301              !MSDOS_I(inode)->i_start))) {
302                 if (sector >= sbi->dir_entries >> sbi->dir_per_block_bits)
303                         return 0;
304                 return sector + sbi->dir_start;
305         }
306         last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
307                 >> sb->s_blocksize_bits;
308         if (sector >= last_block)
309                 return 0;
310
311         cluster = sector / sbi->cluster_size;
312         offset  = sector % sbi->cluster_size;
313         if (!(cluster = fat_get_cluster(inode, cluster)))
314                 return 0;
315
316         return (cluster - 2) * sbi->cluster_size + sbi->data_start + offset;
317 }
318
319
320 /* Free all clusters after the skip'th cluster. Doesn't use the cache,
321    because this way we get an additional sanity check. */
322
323 int fat_free(struct inode *inode,int skip)
324 {
325         int nr,last;
326
327         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
328         last = 0;
329         while (skip--) {
330                 last = nr;
331                 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
332                 if (!nr) {
333                         printk("fat_free: skipped EOF\n");
334                         return -EIO;
335                 }
336         }
337         if (last) {
338                 fat_access(inode->i_sb,last,EOF_FAT(inode->i_sb));
339                 fat_cache_inval_inode(inode);
340         } else {
341                 fat_cache_inval_inode(inode);
342                 MSDOS_I(inode)->i_start = 0;
343                 MSDOS_I(inode)->i_logstart = 0;
344                 mark_inode_dirty(inode);
345         }
346         lock_fat(inode->i_sb);
347         while (nr != -1) {
348                 if (!(nr = fat_access(inode->i_sb,nr,0))) {
349                         fat_fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
350                         break;
351                 }
352                 if (MSDOS_SB(inode->i_sb)->free_clusters != -1) {
353                         MSDOS_SB(inode->i_sb)->free_clusters++;
354                         if (MSDOS_SB(inode->i_sb)->fat_bits == 32) {
355                                 fat_clusters_flush(inode->i_sb);
356                         }
357                 }
358                 inode->i_blocks -= (1 << MSDOS_SB(inode->i_sb)->cluster_bits) / 512;
359         }
360         unlock_fat(inode->i_sb);
361         return 0;
362 }