1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/fat/cache.c
4 *
5 * Written 1992,1993 by Werner Almesberger
6 *
7 * Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
8 * of inode number.
9 * May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
10 */
11
12 #include <linux/slab.h>
13 #include "fat.h"
14
15 /* this must be > 0. */
16 #define FAT_MAX_CACHE 8
17
18 struct fat_cache {
19 struct list_head cache_list;
20 int nr_contig; /* number of contiguous clusters */
21 int fcluster; /* cluster number in the file. */
22 int dcluster; /* cluster number on disk. */
23 };
24
25 struct fat_cache_id {
26 unsigned int id;
27 int nr_contig;
28 int fcluster;
29 int dcluster;
30 };
31
fat_max_cache(struct inode * inode)32 static inline int fat_max_cache(struct inode *inode)
33 {
34 return FAT_MAX_CACHE;
35 }
36
37 static struct kmem_cache *fat_cache_cachep;
38
init_once(void * foo)39 static void init_once(void *foo)
40 {
41 struct fat_cache *cache = (struct fat_cache *)foo;
42
43 INIT_LIST_HEAD(&cache->cache_list);
44 }
45
fat_cache_init(void)46 int __init fat_cache_init(void)
47 {
48 fat_cache_cachep = kmem_cache_create("fat_cache",
49 sizeof(struct fat_cache),
50 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
51 init_once);
52 if (fat_cache_cachep == NULL)
53 return -ENOMEM;
54 return 0;
55 }
56
fat_cache_destroy(void)57 void fat_cache_destroy(void)
58 {
59 kmem_cache_destroy(fat_cache_cachep);
60 }
61
fat_cache_alloc(struct inode * inode)62 static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
63 {
64 return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
65 }
66
fat_cache_free(struct fat_cache * cache)67 static inline void fat_cache_free(struct fat_cache *cache)
68 {
69 BUG_ON(!list_empty(&cache->cache_list));
70 kmem_cache_free(fat_cache_cachep, cache);
71 }
72
fat_cache_update_lru(struct inode * inode,struct fat_cache * cache)73 static inline void fat_cache_update_lru(struct inode *inode,
74 struct fat_cache *cache)
75 {
76 if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
77 list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
78 }
79
fat_cache_lookup(struct inode * inode,int fclus,struct fat_cache_id * cid,int * cached_fclus,int * cached_dclus)80 static int fat_cache_lookup(struct inode *inode, int fclus,
81 struct fat_cache_id *cid,
82 int *cached_fclus, int *cached_dclus)
83 {
84 static struct fat_cache nohit = { .fcluster = 0, };
85
86 struct fat_cache *hit = &nohit, *p;
87 int offset = -1;
88
89 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
90 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
91 /* Find the cache of "fclus" or nearest cache. */
92 if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
93 hit = p;
94 if ((hit->fcluster + hit->nr_contig) < fclus) {
95 offset = hit->nr_contig;
96 } else {
97 offset = fclus - hit->fcluster;
98 break;
99 }
100 }
101 }
102 if (hit != &nohit) {
103 fat_cache_update_lru(inode, hit);
104
105 cid->id = MSDOS_I(inode)->cache_valid_id;
106 cid->nr_contig = hit->nr_contig;
107 cid->fcluster = hit->fcluster;
108 cid->dcluster = hit->dcluster;
109 *cached_fclus = cid->fcluster + offset;
110 *cached_dclus = cid->dcluster + offset;
111 }
112 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
113
114 return offset;
115 }
116
fat_cache_merge(struct inode * inode,struct fat_cache_id * new)117 static struct fat_cache *fat_cache_merge(struct inode *inode,
118 struct fat_cache_id *new)
119 {
120 struct fat_cache *p;
121
122 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
123 /* Find the same part as "new" in cluster-chain. */
124 if (p->fcluster == new->fcluster) {
125 BUG_ON(p->dcluster != new->dcluster);
126 if (new->nr_contig > p->nr_contig)
127 p->nr_contig = new->nr_contig;
128 return p;
129 }
130 }
131 return NULL;
132 }
133
fat_cache_add(struct inode * inode,struct fat_cache_id * new)134 static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
135 {
136 struct fat_cache *cache, *tmp;
137
138 if (new->fcluster == -1) /* dummy cache */
139 return;
140
141 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
142 if (new->id != FAT_CACHE_VALID &&
143 new->id != MSDOS_I(inode)->cache_valid_id)
144 goto out; /* this cache was invalidated */
145
146 cache = fat_cache_merge(inode, new);
147 if (cache == NULL) {
148 if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
149 MSDOS_I(inode)->nr_caches++;
150 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
151
152 tmp = fat_cache_alloc(inode);
153 if (!tmp) {
154 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
155 MSDOS_I(inode)->nr_caches--;
156 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
157 return;
158 }
159
160 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
161 cache = fat_cache_merge(inode, new);
162 if (cache != NULL) {
163 MSDOS_I(inode)->nr_caches--;
164 fat_cache_free(tmp);
165 goto out_update_lru;
166 }
167 cache = tmp;
168 } else {
169 struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
170 cache = list_entry(p, struct fat_cache, cache_list);
171 }
172 cache->fcluster = new->fcluster;
173 cache->dcluster = new->dcluster;
174 cache->nr_contig = new->nr_contig;
175 }
176 out_update_lru:
177 fat_cache_update_lru(inode, cache);
178 out:
179 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
180 }
181
182 /*
183 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
184 * fixes itself after a while.
185 */
__fat_cache_inval_inode(struct inode * inode)186 static void __fat_cache_inval_inode(struct inode *inode)
187 {
188 struct msdos_inode_info *i = MSDOS_I(inode);
189 struct fat_cache *cache;
190
191 while (!list_empty(&i->cache_lru)) {
192 cache = list_entry(i->cache_lru.next,
193 struct fat_cache, cache_list);
194 list_del_init(&cache->cache_list);
195 i->nr_caches--;
196 fat_cache_free(cache);
197 }
198 /* Update. The copy of caches before this id is discarded. */
199 i->cache_valid_id++;
200 if (i->cache_valid_id == FAT_CACHE_VALID)
201 i->cache_valid_id++;
202 }
203
fat_cache_inval_inode(struct inode * inode)204 void fat_cache_inval_inode(struct inode *inode)
205 {
206 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
207 __fat_cache_inval_inode(inode);
208 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
209 }
210
cache_contiguous(struct fat_cache_id * cid,int dclus)211 static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
212 {
213 cid->nr_contig++;
214 return ((cid->dcluster + cid->nr_contig) == dclus);
215 }
216
cache_init(struct fat_cache_id * cid,int fclus,int dclus)217 static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
218 {
219 cid->id = FAT_CACHE_VALID;
220 cid->fcluster = fclus;
221 cid->dcluster = dclus;
222 cid->nr_contig = 0;
223 }
224
fat_get_cluster(struct inode * inode,int cluster,int * fclus,int * dclus)225 int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
226 {
227 struct super_block *sb = inode->i_sb;
228 struct msdos_sb_info *sbi = MSDOS_SB(sb);
229 const int limit = sb->s_maxbytes >> sbi->cluster_bits;
230 struct fat_entry fatent;
231 struct fat_cache_id cid;
232 int nr;
233
234 BUG_ON(MSDOS_I(inode)->i_start == 0);
235
236 *fclus = 0;
237 *dclus = MSDOS_I(inode)->i_start;
238 if (!fat_valid_entry(sbi, *dclus)) {
239 fat_fs_error_ratelimit(sb,
240 "%s: invalid start cluster (i_pos %lld, start %08x)",
241 __func__, MSDOS_I(inode)->i_pos, *dclus);
242 return -EIO;
243 }
244 if (cluster == 0)
245 return 0;
246
247 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
248 /*
249 * dummy, always not contiguous
250 * This is reinitialized by cache_init(), later.
251 */
252 cache_init(&cid, -1, -1);
253 }
254
255 fatent_init(&fatent);
256 while (*fclus < cluster) {
257 /* prevent the infinite loop of cluster chain */
258 if (*fclus > limit) {
259 fat_fs_error_ratelimit(sb,
260 "%s: detected the cluster chain loop (i_pos %lld)",
261 __func__, MSDOS_I(inode)->i_pos);
262 nr = -EIO;
263 goto out;
264 }
265
266 nr = fat_ent_read(inode, &fatent, *dclus);
267 if (nr < 0)
268 goto out;
269 else if (nr == FAT_ENT_FREE) {
270 fat_fs_error_ratelimit(sb,
271 "%s: invalid cluster chain (i_pos %lld)",
272 __func__, MSDOS_I(inode)->i_pos);
273 nr = -EIO;
274 goto out;
275 } else if (nr == FAT_ENT_EOF) {
276 fat_cache_add(inode, &cid);
277 goto out;
278 }
279 (*fclus)++;
280 *dclus = nr;
281 if (!cache_contiguous(&cid, *dclus))
282 cache_init(&cid, *fclus, *dclus);
283 }
284 nr = 0;
285 fat_cache_add(inode, &cid);
286 out:
287 fatent_brelse(&fatent);
288 return nr;
289 }
290
fat_bmap_cluster(struct inode * inode,int cluster)291 static int fat_bmap_cluster(struct inode *inode, int cluster)
292 {
293 struct super_block *sb = inode->i_sb;
294 int ret, fclus, dclus;
295
296 if (MSDOS_I(inode)->i_start == 0)
297 return 0;
298
299 ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
300 if (ret < 0)
301 return ret;
302 else if (ret == FAT_ENT_EOF) {
303 fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
304 __func__, MSDOS_I(inode)->i_pos);
305 return -EIO;
306 }
307 return dclus;
308 }
309
fat_get_mapped_cluster(struct inode * inode,sector_t sector,sector_t last_block,unsigned long * mapped_blocks,sector_t * bmap)310 int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
311 sector_t last_block,
312 unsigned long *mapped_blocks, sector_t *bmap)
313 {
314 struct super_block *sb = inode->i_sb;
315 struct msdos_sb_info *sbi = MSDOS_SB(sb);
316 int cluster, offset;
317
318 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
319 offset = sector & (sbi->sec_per_clus - 1);
320 cluster = fat_bmap_cluster(inode, cluster);
321 if (cluster < 0)
322 return cluster;
323 else if (cluster) {
324 *bmap = fat_clus_to_blknr(sbi, cluster) + offset;
325 *mapped_blocks = sbi->sec_per_clus - offset;
326 if (*mapped_blocks > last_block - sector)
327 *mapped_blocks = last_block - sector;
328 }
329
330 return 0;
331 }
332
is_exceed_eof(struct inode * inode,sector_t sector,sector_t * last_block,int create)333 static int is_exceed_eof(struct inode *inode, sector_t sector,
334 sector_t *last_block, int create)
335 {
336 struct super_block *sb = inode->i_sb;
337 const unsigned long blocksize = sb->s_blocksize;
338 const unsigned char blocksize_bits = sb->s_blocksize_bits;
339
340 *last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
341 if (sector >= *last_block) {
342 if (!create)
343 return 1;
344
345 /*
346 * ->mmu_private can access on only allocation path.
347 * (caller must hold ->i_mutex)
348 */
349 *last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
350 >> blocksize_bits;
351 if (sector >= *last_block)
352 return 1;
353 }
354
355 return 0;
356 }
357
fat_bmap(struct inode * inode,sector_t sector,sector_t * phys,unsigned long * mapped_blocks,int create,bool from_bmap)358 int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
359 unsigned long *mapped_blocks, int create, bool from_bmap)
360 {
361 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
362 sector_t last_block;
363
364 *phys = 0;
365 *mapped_blocks = 0;
366 if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) {
367 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
368 *phys = sector + sbi->dir_start;
369 *mapped_blocks = 1;
370 }
371 return 0;
372 }
373
374 if (!from_bmap) {
375 if (is_exceed_eof(inode, sector, &last_block, create))
376 return 0;
377 } else {
378 last_block = inode->i_blocks >>
379 (inode->i_sb->s_blocksize_bits - 9);
380 if (sector >= last_block)
381 return 0;
382 }
383
384 return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks,
385 phys);
386 }
387