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
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5
6
7 #include <linux/msdos_fs.h>
8 #include <linux/kernel.h>
9 #include <linux/errno.h>
10 #include <linux/string.h>
11 #include <linux/stat.h>
12
13
14 static struct fat_cache *fat_cache,cache[FAT_CACHE];
15
16
17
18
19 int fat_access(struct super_block *sb,int nr,int new_value)
20 {
21 struct buffer_head *bh,*bh2,*c_bh,*c_bh2;
22 unsigned char *p_first,*p_last;
23 void *data,*data2,*c_data,*c_data2;
24 int first,last,next,copy;
25
26 if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters) return 0;
27 if (MSDOS_SB(sb)->fat_bits == 16) first = last = nr*2;
28 else {
29 first = nr*3/2;
30 last = first+1;
31 }
32 if (!(bh = msdos_sread(sb->s_dev,MSDOS_SB(sb)->fat_start+(first >>
33 SECTOR_BITS),&data))) {
34 printk("bread in fat_access failed\n");
35 return 0;
36 }
37 if ((first >> SECTOR_BITS) == (last >> SECTOR_BITS)) {
38 bh2 = bh;
39 data2 = data;
40 }
41 else {
42 if (!(bh2 = msdos_sread(sb->s_dev,MSDOS_SB(sb)->fat_start+(last
43 >> SECTOR_BITS),&data2))) {
44 brelse(bh);
45 printk("bread in fat_access failed\n");
46 return 0;
47 }
48 }
49 if (MSDOS_SB(sb)->fat_bits == 16) {
50 p_first = p_last = NULL;
51 next = CF_LE_W(((unsigned short *) data)[(first &
52 (SECTOR_SIZE-1)) >> 1]);
53 if (next >= 0xfff7) next = -1;
54 }
55 else {
56 p_first = &((unsigned char *) data)[first & (SECTOR_SIZE-1)];
57 p_last = &((unsigned char *) data2)[(first+1) &
58 (SECTOR_SIZE-1)];
59 if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
60 else next = (*p_first+(*p_last << 8)) & 0xfff;
61 if (next >= 0xff7) next = -1;
62 }
63 if (new_value != -1) {
64 if (MSDOS_SB(sb)->fat_bits == 16)
65 ((unsigned short *) data)[(first & (SECTOR_SIZE-1)) >>
66 1] = CT_LE_W(new_value);
67 else {
68 if (nr & 1) {
69 *p_first = (*p_first & 0xf) | (new_value << 4);
70 *p_last = new_value >> 4;
71 }
72 else {
73 *p_first = new_value & 0xff;
74 *p_last = (*p_last & 0xf0) | (new_value >> 8);
75 }
76 mark_buffer_dirty(bh2, 1);
77 }
78 mark_buffer_dirty(bh, 1);
79 for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
80 if (!(c_bh = msdos_sread(sb->s_dev,MSDOS_SB(sb)->
81 fat_start+(first >> SECTOR_BITS)+MSDOS_SB(sb)->
82 fat_length*copy,&c_data))) break;
83 memcpy(c_data,data,SECTOR_SIZE);
84 mark_buffer_dirty(c_bh, 1);
85 if (data != data2 || bh != bh2) {
86 if (!(c_bh2 = msdos_sread(sb->s_dev,
87 MSDOS_SB(sb)->fat_start+(first >>
88 SECTOR_BITS)+MSDOS_SB(sb)->fat_length*copy
89 +1,&c_data2))) {
90 brelse(c_bh);
91 break;
92 }
93 memcpy(c_data2,data2,SECTOR_SIZE);
94 brelse(c_bh2);
95 }
96 brelse(c_bh);
97 }
98 }
99 brelse(bh);
100 if (data != data2) brelse(bh2);
101 return next;
102 }
103
104
105 void cache_init(void)
106 {
107 static int initialized = 0;
108 int count;
109
110 if (initialized) return;
111 fat_cache = &cache[0];
112 for (count = 0; count < FAT_CACHE; count++) {
113 cache[count].device = 0;
114 cache[count].next = count == FAT_CACHE-1 ? NULL :
115 &cache[count+1];
116 }
117 initialized = 1;
118 }
119
120
121 void cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
122 {
123 struct fat_cache *walk;
124
125 #ifdef DEBUG
126 printk("cache lookup: <%d,%d> %d (%d,%d) -> ",inode->i_dev,inode->i_ino,cluster,
127 *f_clu,*d_clu);
128 #endif
129 for (walk = fat_cache; walk; walk = walk->next)
130 if (inode->i_dev == walk->device && walk->ino == inode->i_ino &&
131 walk->file_cluster <= cluster && walk->file_cluster >
132 *f_clu) {
133 *d_clu = walk->disk_cluster;
134 #ifdef DEBUG
135 printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
136 #endif
137 if ((*f_clu = walk->file_cluster) == cluster) return;
138 }
139 #ifdef DEBUG
140 printk("cache miss\n");
141 #endif
142 }
143
144
145 #ifdef DEBUG
146 static void list_cache(void)
147 {
148 struct fat_cache *walk;
149
150 for (walk = fat_cache; walk; walk = walk->next) {
151 if (walk->device)
152 printk("<%d,%d>(%d,%d) ",walk->device,walk->ino,
153 walk->file_cluster,walk->disk_cluster);
154 else printk("-- ");
155 }
156 printk("\n");
157 }
158 #endif
159
160
161 void cache_add(struct inode *inode,int f_clu,int d_clu)
162 {
163 struct fat_cache *walk,*last;
164
165 #ifdef DEBUG
166 printk("cache add: <%d,%d> %d (%d)\n",inode->i_dev,inode->i_ino,f_clu,d_clu);
167 #endif
168 last = NULL;
169 for (walk = fat_cache; walk->next; walk = (last = walk)->next)
170 if (inode->i_dev == walk->device && walk->ino == inode->i_ino &&
171 walk->file_cluster == f_clu) {
172 if (walk->disk_cluster != d_clu) {
173 printk("FAT cache corruption");
174 cache_inval_inode(inode);
175 return;
176 }
177
178 if (last == NULL) return;
179 last->next = walk->next;
180 walk->next = fat_cache;
181 fat_cache = walk;
182 #ifdef DEBUG
183 list_cache();
184 #endif
185 return;
186 }
187 walk->device = inode->i_dev;
188 walk->ino = inode->i_ino;
189 walk->file_cluster = f_clu;
190 walk->disk_cluster = d_clu;
191 last->next = NULL;
192 walk->next = fat_cache;
193 fat_cache = walk;
194 #ifdef DEBUG
195 list_cache();
196 #endif
197 }
198
199
200
201
202
203 void cache_inval_inode(struct inode *inode)
204 {
205 struct fat_cache *walk;
206
207 for (walk = fat_cache; walk; walk = walk->next)
208 if (walk->device == inode->i_dev && walk->ino == inode->i_ino)
209 walk->device = 0;
210 }
211
212
213 void cache_inval_dev(int device)
214 {
215 struct fat_cache *walk;
216
217 for (walk = fat_cache; walk; walk = walk->next)
218 if (walk->device == device) walk->device = 0;
219 }
220
221
222 int get_cluster(struct inode *inode,int cluster)
223 {
224 int nr,count;
225
226 if (!(nr = MSDOS_I(inode)->i_start)) return 0;
227 if (!cluster) return nr;
228 count = 0;
229 for (cache_lookup(inode,cluster,&count,&nr); count < cluster;
230 count++) {
231 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
232 if (!nr) return 0;
233 }
234 cache_add(inode,cluster,nr);
235 return nr;
236 }
237
238
239 int msdos_smap(struct inode *inode,int sector)
240 {
241 struct msdos_sb_info *sb;
242 int cluster,offset;
243
244 sb = MSDOS_SB(inode->i_sb);
245 if (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
246 !MSDOS_I(inode)->i_start)) {
247 if (sector >= sb->dir_entries >> MSDOS_DPS_BITS) return 0;
248 return sector+sb->dir_start;
249 }
250 cluster = sector/sb->cluster_size;
251 offset = sector % sb->cluster_size;
252 if (!(cluster = get_cluster(inode,cluster))) return 0;
253 return (cluster-2)*sb->cluster_size+sb->data_start+offset;
254 }
255
256
257
258
259
260 int fat_free(struct inode *inode,int skip)
261 {
262 int nr,last;
263
264 if (!(nr = MSDOS_I(inode)->i_start)) return 0;
265 last = 0;
266 while (skip--) {
267 last = nr;
268 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
269 if (!nr) {
270 printk("fat_free: skipped EOF\n");
271 return -EIO;
272 }
273 }
274 if (last)
275 fat_access(inode->i_sb,last,MSDOS_SB(inode->i_sb)->fat_bits ==
276 12 ? 0xff8 : 0xfff8);
277 else {
278 MSDOS_I(inode)->i_start = 0;
279 inode->i_dirt = 1;
280 }
281 lock_fat(inode->i_sb);
282 while (nr != -1) {
283 if (!(nr = fat_access(inode->i_sb,nr,0))) {
284 fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
285 break;
286 }
287 if (MSDOS_SB(inode->i_sb)->free_clusters != -1)
288 MSDOS_SB(inode->i_sb)->free_clusters++;
289 inode->i_blocks -= MSDOS_SB(inode->i_sb)->cluster_size;
290 }
291 unlock_fat(inode->i_sb);
292 cache_inval_inode(inode);
293 return 0;
294 }
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