This source file includes following definitions.
- fat_access
- cache_init
- cache_lookup
- list_cache
- cache_add
- cache_inval_inode
- cache_inval_dev
- get_cluster
- msdos_smap
- fat_free
1
2
3
4
5
6
7 #include <linux/msdos_fs.h>
8 #include <linux/kernel.h>
9 #include <linux/errno.h>
10 #include <linux/stat.h>
11
12
13 static struct fat_cache *fat_cache,cache[FAT_CACHE];
14
15
16
17
18 int fat_access(struct super_block *sb,int nr,int new_value)
19 {
20 struct buffer_head *bh,*bh2,*c_bh,*c_bh2;
21 unsigned char *p_first,*p_last;
22 void *data,*data2,*c_data,*c_data2;
23 int first,last,next,copy;
24
25 if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters) return 0;
26 if (MSDOS_SB(sb)->fat_bits == 16) first = last = nr*2;
27 else {
28 first = nr*3/2;
29 last = first+1;
30 }
31 if (!(bh = msdos_sread(sb->s_dev,MSDOS_SB(sb)->fat_start+(first >>
32 SECTOR_BITS),&data))) {
33 printk("bread in fat_access failed\n");
34 return 0;
35 }
36 if ((first >> SECTOR_BITS) == (last >> SECTOR_BITS)) {
37 bh2 = bh;
38 data2 = data;
39 }
40 else {
41 if (!(bh2 = msdos_sread(sb->s_dev,MSDOS_SB(sb)->fat_start+(last
42 >> SECTOR_BITS),&data2))) {
43 brelse(bh);
44 printk("bread in fat_access failed\n");
45 return 0;
46 }
47 }
48 if (MSDOS_SB(sb)->fat_bits == 16) {
49 p_first = p_last = NULL;
50 next = CF_LE_W(((unsigned short *) data)[(first &
51 (SECTOR_SIZE-1)) >> 1]);
52 if (next >= 0xfff7) next = -1;
53 }
54 else {
55 p_first = &((unsigned char *) data)[first & (SECTOR_SIZE-1)];
56 p_last = &((unsigned char *) data2)[(first+1) &
57 (SECTOR_SIZE-1)];
58 if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
59 else next = (*p_first+(*p_last << 8)) & 0xfff;
60 if (next >= 0xff7) next = -1;
61 }
62 if (new_value != -1) {
63 if (MSDOS_SB(sb)->fat_bits == 16)
64 ((unsigned short *) data)[(first & (SECTOR_SIZE-1)) >>
65 1] = CT_LE_W(new_value);
66 else {
67 if (nr & 1) {
68 *p_first = (*p_first & 0xf) | (new_value << 4);
69 *p_last = new_value >> 4;
70 }
71 else {
72 *p_first = new_value & 0xff;
73 *p_last = (*p_last & 0xf0) | (new_value >> 8);
74 }
75 bh2->b_dirt = 1;
76 }
77 bh->b_dirt = 1;
78 for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
79 if (!(c_bh = msdos_sread(sb->s_dev,MSDOS_SB(sb)->
80 fat_start+(first >> SECTOR_BITS)+MSDOS_SB(sb)->
81 fat_length*copy,&c_data))) break;
82 memcpy(c_data,data,SECTOR_SIZE);
83 c_bh->b_dirt = 1;
84 if (data != data2 || bh != bh2) {
85 if (!(c_bh2 = msdos_sread(sb->s_dev,
86 MSDOS_SB(sb)->fat_start+(first >>
87 SECTOR_BITS)+MSDOS_SB(sb)->fat_length*copy
88 +1,&c_data2))) {
89 brelse(c_bh);
90 break;
91 }
92 memcpy(c_data2,data2,SECTOR_SIZE);
93 brelse(c_bh2);
94 }
95 brelse(c_bh);
96 }
97 }
98 brelse(bh);
99 if (data != data2) brelse(bh2);
100 return next;
101 }
102
103
104 void cache_init(void)
105 {
106 static int initialized = 0;
107 int count;
108
109 if (initialized) return;
110 fat_cache = &cache[0];
111 for (count = 0; count < FAT_CACHE; count++) {
112 cache[count].device = 0;
113 cache[count].next = count == FAT_CACHE-1 ? NULL :
114 &cache[count+1];
115 }
116 initialized = 1;
117 }
118
119
120 void cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
121 {
122 struct fat_cache *walk;
123
124 #ifdef DEBUG
125 printk("cache lookup: <%d,%d> %d (%d,%d) -> ",inode->i_dev,inode->i_ino,cluster,
126 *f_clu,*d_clu);
127 #endif
128 for (walk = fat_cache; walk; walk = walk->next)
129 if (inode->i_dev == walk->device && walk->ino == inode->i_ino &&
130 walk->file_cluster <= cluster && walk->file_cluster >
131 *f_clu) {
132 *d_clu = walk->disk_cluster;
133 #ifdef DEBUG
134 printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
135 #endif
136 if ((*f_clu = walk->file_cluster) == cluster) return;
137 }
138 #ifdef DEBUG
139 printk("cache miss\n");
140 #endif
141 }
142
143
144 #ifdef DEBUG
145 static void list_cache(void)
146 {
147 struct fat_cache *walk;
148
149 for (walk = fat_cache; walk; walk = walk->next) {
150 if (walk->device)
151 printk("<%d,%d>(%d,%d) ",walk->device,walk->ino,
152 walk->file_cluster,walk->disk_cluster);
153 else printk("-- ");
154 }
155 printk("\n");
156 }
157 #endif
158
159
160 void cache_add(struct inode *inode,int f_clu,int d_clu)
161 {
162 struct fat_cache *walk,*last;
163
164 #ifdef DEBUG
165 printk("cache add: <%d,%d> %d (%d)\n",inode->i_dev,inode->i_ino,f_clu,d_clu);
166 #endif
167 last = NULL;
168 for (walk = fat_cache; walk->next; walk = (last = walk)->next)
169 if (inode->i_dev == walk->device && walk->ino == inode->i_ino &&
170 walk->file_cluster == f_clu) {
171 if (walk->disk_cluster != d_clu) {
172 printk("FAT cache corruption");
173 cache_inval_inode(inode);
174 return;
175 }
176
177 if (last == NULL) return;
178 last->next = walk->next;
179 walk->next = fat_cache;
180 fat_cache = walk;
181 #ifdef DEBUG
182 list_cache();
183 #endif
184 return;
185 }
186 walk->device = inode->i_dev;
187 walk->ino = inode->i_ino;
188 walk->file_cluster = f_clu;
189 walk->disk_cluster = d_clu;
190 last->next = NULL;
191 walk->next = fat_cache;
192 fat_cache = walk;
193 #ifdef DEBUG
194 list_cache();
195 #endif
196 }
197
198
199
200
201
202 void cache_inval_inode(struct inode *inode)
203 {
204 struct fat_cache *walk;
205
206 for (walk = fat_cache; walk; walk = walk->next)
207 if (walk->device == inode->i_dev && walk->ino == inode->i_ino)
208 walk->device = 0;
209 }
210
211
212 void cache_inval_dev(int device)
213 {
214 struct fat_cache *walk;
215
216 for (walk = fat_cache; walk; walk = walk->next)
217 if (walk->device == device) walk->device = 0;
218 }
219
220
221 int get_cluster(struct inode *inode,int cluster)
222 {
223 int nr,count;
224
225 if (!(nr = MSDOS_I(inode)->i_start)) return 0;
226 if (!cluster) return nr;
227 count = 0;
228 for (cache_lookup(inode,cluster,&count,&nr); count < cluster;
229 count++) {
230 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
231 if (!nr) return 0;
232 }
233 cache_add(inode,cluster,nr);
234 return nr;
235 }
236
237
238 int msdos_smap(struct inode *inode,int sector)
239 {
240 struct msdos_sb_info *sb;
241 int cluster,offset;
242
243 sb = MSDOS_SB(inode->i_sb);
244 if (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
245 !MSDOS_I(inode)->i_start)) {
246 if (sector >= sb->dir_entries >> MSDOS_DPS_BITS) return 0;
247 return sector+sb->dir_start;
248 }
249 cluster = sector/sb->cluster_size;
250 offset = sector % sb->cluster_size;
251 if (!(cluster = get_cluster(inode,cluster))) return 0;
252 return (cluster-2)*sb->cluster_size+sb->data_start+offset;
253 }
254
255
256
257
258
259 int fat_free(struct inode *inode,int skip)
260 {
261 int nr,last;
262
263 if (!(nr = MSDOS_I(inode)->i_start)) return 0;
264 last = 0;
265 while (skip--) {
266 last = nr;
267 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
268 if (!nr) {
269 printk("fat_free: skipped EOF\n");
270 return -EIO;
271 }
272 }
273 if (last)
274 fat_access(inode->i_sb,last,MSDOS_SB(inode->i_sb)->fat_bits ==
275 12 ? 0xff8 : 0xfff8);
276 else {
277 MSDOS_I(inode)->i_start = 0;
278 inode->i_dirt = 1;
279 }
280 lock_fat(inode->i_sb);
281 while (nr != -1) {
282 if (!(nr = fat_access(inode->i_sb,nr,0))) {
283 fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
284 break;
285 }
286 if (MSDOS_SB(inode->i_sb)->free_clusters != -1)
287 MSDOS_SB(inode->i_sb)->free_clusters++;
288 inode->i_blocks -= MSDOS_SB(inode->i_sb)->cluster_size;
289 }
290 unlock_fat(inode->i_sb);
291 cache_inval_inode(inode);
292 return 0;
293 }
![[first]](../icons/first.png){kind=icon}
![[previous]](../icons/n_left.png){kind=icon}
![[next]](../icons/n_right.png){kind=icon}
![[last]](../icons/last.png){kind=icon}
![[top]](../icons/n_top.png){kind=icon}
![[bottom]](../icons/bottom.png){kind=icon}
![[index]](../icons/index.png){kind=icon}
![[help]](../icons/help.png){kind=icon}
*/
![[next]](../icons/right.png)
![[first]](../icons/n_first.png)
![[top]](../icons/top.png)
![[previous]](../icons/left.png)
![[last]](../icons/n_last.png)
![[bottom]](../icons/n_bottom.png){kind=icon}