blob: ae8200f84e395f4e27680d509e28ade20807c82e [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/fs.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090012#include <linux/slab.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070013#include <linux/buffer_head.h>
OGAWA Hirofumi9e975da2008-11-06 12:53:46 -080014#include "fat.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
16/* this must be > 0. */
17#define FAT_MAX_CACHE 8
18
19struct fat_cache {
20 struct list_head cache_list;
21 int nr_contig; /* number of contiguous clusters */
22 int fcluster; /* cluster number in the file. */
23 int dcluster; /* cluster number on disk. */
24};
25
26struct fat_cache_id {
27 unsigned int id;
28 int nr_contig;
29 int fcluster;
30 int dcluster;
31};
32
33static inline int fat_max_cache(struct inode *inode)
34{
35 return FAT_MAX_CACHE;
36}
37
Christoph Lametere18b8902006-12-06 20:33:20 -080038static struct kmem_cache *fat_cache_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -070039
Alexey Dobriyan51cc5062008-07-25 19:45:34 -070040static void init_once(void *foo)
Linus Torvalds1da177e2005-04-16 15:20:36 -070041{
42 struct fat_cache *cache = (struct fat_cache *)foo;
43
Christoph Lametera35afb82007-05-16 22:10:57 -070044 INIT_LIST_HEAD(&cache->cache_list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070045}
46
47int __init fat_cache_init(void)
48{
49 fat_cache_cachep = kmem_cache_create("fat_cache",
50 sizeof(struct fat_cache),
Paul Jackson4b6a9312006-03-24 03:16:05 -080051 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
Paul Mundt20c2df82007-07-20 10:11:58 +090052 init_once);
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 if (fat_cache_cachep == NULL)
54 return -ENOMEM;
55 return 0;
56}
57
Andrew Mortonef6689e2005-06-30 22:13:14 -070058void fat_cache_destroy(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -070059{
Alexey Dobriyan1a1d92c2006-09-27 01:49:40 -070060 kmem_cache_destroy(fat_cache_cachep);
Linus Torvalds1da177e2005-04-16 15:20:36 -070061}
62
63static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
64{
Linus Torvalds8f593422008-05-19 19:53:01 -070065 return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -070066}
67
68static inline void fat_cache_free(struct fat_cache *cache)
69{
70 BUG_ON(!list_empty(&cache->cache_list));
71 kmem_cache_free(fat_cache_cachep, cache);
72}
73
74static inline void fat_cache_update_lru(struct inode *inode,
75 struct fat_cache *cache)
76{
77 if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
78 list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
79}
80
81static int fat_cache_lookup(struct inode *inode, int fclus,
82 struct fat_cache_id *cid,
83 int *cached_fclus, int *cached_dclus)
84{
85 static struct fat_cache nohit = { .fcluster = 0, };
86
87 struct fat_cache *hit = &nohit, *p;
88 int offset = -1;
89
90 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
91 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
92 /* Find the cache of "fclus" or nearest cache. */
93 if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
94 hit = p;
95 if ((hit->fcluster + hit->nr_contig) < fclus) {
96 offset = hit->nr_contig;
97 } else {
98 offset = fclus - hit->fcluster;
99 break;
100 }
101 }
102 }
103 if (hit != &nohit) {
104 fat_cache_update_lru(inode, hit);
105
106 cid->id = MSDOS_I(inode)->cache_valid_id;
107 cid->nr_contig = hit->nr_contig;
108 cid->fcluster = hit->fcluster;
109 cid->dcluster = hit->dcluster;
110 *cached_fclus = cid->fcluster + offset;
111 *cached_dclus = cid->dcluster + offset;
112 }
113 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
114
115 return offset;
116}
117
118static struct fat_cache *fat_cache_merge(struct inode *inode,
119 struct fat_cache_id *new)
120{
121 struct fat_cache *p;
122
123 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
124 /* Find the same part as "new" in cluster-chain. */
125 if (p->fcluster == new->fcluster) {
126 BUG_ON(p->dcluster != new->dcluster);
127 if (new->nr_contig > p->nr_contig)
128 p->nr_contig = new->nr_contig;
129 return p;
130 }
131 }
132 return NULL;
133}
134
135static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
136{
137 struct fat_cache *cache, *tmp;
138
139 if (new->fcluster == -1) /* dummy cache */
140 return;
141
142 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
143 if (new->id != FAT_CACHE_VALID &&
144 new->id != MSDOS_I(inode)->cache_valid_id)
145 goto out; /* this cache was invalidated */
146
147 cache = fat_cache_merge(inode, new);
148 if (cache == NULL) {
149 if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
150 MSDOS_I(inode)->nr_caches++;
151 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
152
153 tmp = fat_cache_alloc(inode);
154 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
155 cache = fat_cache_merge(inode, new);
156 if (cache != NULL) {
157 MSDOS_I(inode)->nr_caches--;
158 fat_cache_free(tmp);
159 goto out_update_lru;
160 }
161 cache = tmp;
162 } else {
163 struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
164 cache = list_entry(p, struct fat_cache, cache_list);
165 }
166 cache->fcluster = new->fcluster;
167 cache->dcluster = new->dcluster;
168 cache->nr_contig = new->nr_contig;
169 }
170out_update_lru:
171 fat_cache_update_lru(inode, cache);
172out:
173 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
174}
175
176/*
177 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
178 * fixes itself after a while.
179 */
180static void __fat_cache_inval_inode(struct inode *inode)
181{
182 struct msdos_inode_info *i = MSDOS_I(inode);
183 struct fat_cache *cache;
184
185 while (!list_empty(&i->cache_lru)) {
186 cache = list_entry(i->cache_lru.next, struct fat_cache, cache_list);
187 list_del_init(&cache->cache_list);
188 i->nr_caches--;
189 fat_cache_free(cache);
190 }
191 /* Update. The copy of caches before this id is discarded. */
192 i->cache_valid_id++;
193 if (i->cache_valid_id == FAT_CACHE_VALID)
194 i->cache_valid_id++;
195}
196
197void fat_cache_inval_inode(struct inode *inode)
198{
199 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
200 __fat_cache_inval_inode(inode);
201 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
202}
203
204static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
205{
206 cid->nr_contig++;
207 return ((cid->dcluster + cid->nr_contig) == dclus);
208}
209
210static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
211{
212 cid->id = FAT_CACHE_VALID;
213 cid->fcluster = fclus;
214 cid->dcluster = dclus;
215 cid->nr_contig = 0;
216}
217
218int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
219{
220 struct super_block *sb = inode->i_sb;
221 const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
222 struct fat_entry fatent;
223 struct fat_cache_id cid;
224 int nr;
225
226 BUG_ON(MSDOS_I(inode)->i_start == 0);
227
228 *fclus = 0;
229 *dclus = MSDOS_I(inode)->i_start;
230 if (cluster == 0)
231 return 0;
232
233 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
234 /*
235 * dummy, always not contiguous
236 * This is reinitialized by cache_init(), later.
237 */
238 cache_init(&cid, -1, -1);
239 }
240
241 fatent_init(&fatent);
242 while (*fclus < cluster) {
243 /* prevent the infinite loop of cluster chain */
244 if (*fclus > limit) {
OGAWA Hirofumiaaa04b42010-05-24 14:33:12 -0700245 fat_fs_error_ratelimit(sb,
246 "%s: detected the cluster chain loop"
247 " (i_pos %lld)", __func__,
248 MSDOS_I(inode)->i_pos);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 nr = -EIO;
250 goto out;
251 }
252
253 nr = fat_ent_read(inode, &fatent, *dclus);
254 if (nr < 0)
255 goto out;
256 else if (nr == FAT_ENT_FREE) {
OGAWA Hirofumiaaa04b42010-05-24 14:33:12 -0700257 fat_fs_error_ratelimit(sb, "%s: invalid cluster chain"
258 " (i_pos %lld)", __func__,
259 MSDOS_I(inode)->i_pos);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 nr = -EIO;
261 goto out;
262 } else if (nr == FAT_ENT_EOF) {
263 fat_cache_add(inode, &cid);
264 goto out;
265 }
266 (*fclus)++;
267 *dclus = nr;
268 if (!cache_contiguous(&cid, *dclus))
269 cache_init(&cid, *fclus, *dclus);
270 }
271 nr = 0;
272 fat_cache_add(inode, &cid);
273out:
274 fatent_brelse(&fatent);
275 return nr;
276}
277
278static int fat_bmap_cluster(struct inode *inode, int cluster)
279{
280 struct super_block *sb = inode->i_sb;
281 int ret, fclus, dclus;
282
283 if (MSDOS_I(inode)->i_start == 0)
284 return 0;
285
286 ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
287 if (ret < 0)
288 return ret;
289 else if (ret == FAT_ENT_EOF) {
Denis Karpov85c78592009-06-04 02:34:22 +0900290 fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
Harvey Harrison8e24eea2008-04-30 00:55:09 -0700291 __func__, MSDOS_I(inode)->i_pos);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 return -EIO;
293 }
294 return dclus;
295}
296
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800297int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
OGAWA Hirofumi2bdf67e2008-11-06 12:53:57 -0800298 unsigned long *mapped_blocks, int create)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299{
300 struct super_block *sb = inode->i_sb;
301 struct msdos_sb_info *sbi = MSDOS_SB(sb);
OGAWA Hirofumi2bdf67e2008-11-06 12:53:57 -0800302 const unsigned long blocksize = sb->s_blocksize;
303 const unsigned char blocksize_bits = sb->s_blocksize_bits;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304 sector_t last_block;
305 int cluster, offset;
306
307 *phys = 0;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800308 *mapped_blocks = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800310 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 *phys = sector + sbi->dir_start;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800312 *mapped_blocks = 1;
313 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 return 0;
315 }
OGAWA Hirofumi2bdf67e2008-11-06 12:53:57 -0800316
317 last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
318 if (sector >= last_block) {
319 if (!create)
320 return 0;
321
322 /*
323 * ->mmu_private can access on only allocation path.
324 * (caller must hold ->i_mutex)
325 */
326 last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
327 >> blocksize_bits;
328 if (sector >= last_block)
329 return 0;
330 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331
332 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
333 offset = sector & (sbi->sec_per_clus - 1);
334 cluster = fat_bmap_cluster(inode, cluster);
335 if (cluster < 0)
336 return cluster;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800337 else if (cluster) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 *phys = fat_clus_to_blknr(sbi, cluster) + offset;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800339 *mapped_blocks = sbi->sec_per_clus - offset;
340 if (*mapped_blocks > last_block - sector)
341 *mapped_blocks = last_block - sector;
342 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 return 0;
344}