aboutsummaryrefslogtreecommitdiff
path: root/fs/exfat/cache.c
blob: 5a2f119b7e8c79c6e6c917dd66f12b10acef00b5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  linux/fs/fat/cache.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
 *	of inode number.
 *  May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
 *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 */

#include <linux/slab.h>
#include <asm/unaligned.h>
#include <linux/buffer_head.h>

#include "exfat_raw.h"
#include "exfat_fs.h"

#define EXFAT_MAX_CACHE		16

struct exfat_cache {
	struct list_head cache_list;
	unsigned int nr_contig;	/* number of contiguous clusters */
	unsigned int fcluster;	/* cluster number in the file. */
	unsigned int dcluster;	/* cluster number on disk. */
};

struct exfat_cache_id {
	unsigned int id;
	unsigned int nr_contig;
	unsigned int fcluster;
	unsigned int dcluster;
};

static struct kmem_cache *exfat_cachep;

static void exfat_cache_init_once(void *c)
{
	struct exfat_cache *cache = (struct exfat_cache *)c;

	INIT_LIST_HEAD(&cache->cache_list);
}

int exfat_cache_init(void)
{
	exfat_cachep = kmem_cache_create("exfat_cache",
				sizeof(struct exfat_cache),
				0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
				exfat_cache_init_once);
	if (!exfat_cachep)
		return -ENOMEM;
	return 0;
}

void exfat_cache_shutdown(void)
{
	if (!exfat_cachep)
		return;
	kmem_cache_destroy(exfat_cachep);
}

static inline struct exfat_cache *exfat_cache_alloc(void)
{
	return kmem_cache_alloc(exfat_cachep, GFP_NOFS);
}

static inline void exfat_cache_free(struct exfat_cache *cache)
{
	WARN_ON(!list_empty(&cache->cache_list));
	kmem_cache_free(exfat_cachep, cache);
}

static inline void exfat_cache_update_lru(struct inode *inode,
		struct exfat_cache *cache)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);

	if (ei->cache_lru.next != &cache->cache_list)
		list_move(&cache->cache_list, &ei->cache_lru);
}

static unsigned int exfat_cache_lookup(struct inode *inode,
		unsigned int fclus, struct exfat_cache_id *cid,
		unsigned int *cached_fclus, unsigned int *cached_dclus)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);
	static struct exfat_cache nohit = { .fcluster = 0, };
	struct exfat_cache *hit = &nohit, *p;
	unsigned int offset = EXFAT_EOF_CLUSTER;

	spin_lock(&ei->cache_lru_lock);
	list_for_each_entry(p, &ei->cache_lru, cache_list) {
		/* Find the cache of "fclus" or nearest cache. */
		if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
			hit = p;
			if (hit->fcluster + hit->nr_contig < fclus) {
				offset = hit->nr_contig;
			} else {
				offset = fclus - hit->fcluster;
				break;
			}
		}
	}
	if (hit != &nohit) {
		exfat_cache_update_lru(inode, hit);

		cid->id = ei->cache_valid_id;
		cid->nr_contig = hit->nr_contig;
		cid->fcluster = hit->fcluster;
		cid->dcluster = hit->dcluster;
		*cached_fclus = cid->fcluster + offset;
		*cached_dclus = cid->dcluster + offset;
	}
	spin_unlock(&ei->cache_lru_lock);

	return offset;
}

static struct exfat_cache *exfat_cache_merge(struct inode *inode,
		struct exfat_cache_id *new)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);
	struct exfat_cache *p;

	list_for_each_entry(p, &ei->cache_lru, cache_list) {
		/* Find the same part as "new" in cluster-chain. */
		if (p->fcluster == new->fcluster) {
			if (new->nr_contig > p->nr_contig)
				p->nr_contig = new->nr_contig;
			return p;
		}
	}
	return NULL;
}

static void exfat_cache_add(struct inode *inode,
		struct exfat_cache_id *new)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);
	struct exfat_cache *cache, *tmp;

	if (new->fcluster == EXFAT_EOF_CLUSTER) /* dummy cache */
		return;

	spin_lock(&ei->cache_lru_lock);
	if (new->id != EXFAT_CACHE_VALID &&
	    new->id != ei->cache_valid_id)
		goto unlock;	/* this cache was invalidated */

	cache = exfat_cache_merge(inode, new);
	if (cache == NULL) {
		if (ei->nr_caches < EXFAT_MAX_CACHE) {
			ei->nr_caches++;
			spin_unlock(&ei->cache_lru_lock);

			tmp = exfat_cache_alloc();
			if (!tmp) {
				spin_lock(&ei->cache_lru_lock);
				ei->nr_caches--;
				spin_unlock(&ei->cache_lru_lock);
				return;
			}

			spin_lock(&ei->cache_lru_lock);
			cache = exfat_cache_merge(inode, new);
			if (cache != NULL) {
				ei->nr_caches--;
				exfat_cache_free(tmp);
				goto out_update_lru;
			}
			cache = tmp;
		} else {
			struct list_head *p = ei->cache_lru.prev;

			cache = list_entry(p,
					struct exfat_cache, cache_list);
		}
		cache->fcluster = new->fcluster;
		cache->dcluster = new->dcluster;
		cache->nr_contig = new->nr_contig;
	}
out_update_lru:
	exfat_cache_update_lru(inode, cache);
unlock:
	spin_unlock(&ei->cache_lru_lock);
}

/*
 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 * fixes itself after a while.
 */
static void __exfat_cache_inval_inode(struct inode *inode)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);
	struct exfat_cache *cache;

	while (!list_empty(&ei->cache_lru)) {
		cache = list_entry(ei->cache_lru.next,
				   struct exfat_cache, cache_list);
		list_del_init(&cache->cache_list);
		ei->nr_caches--;
		exfat_cache_free(cache);
	}
	/* Update. The copy of caches before this id is discarded. */
	ei->cache_valid_id++;
	if (ei->cache_valid_id == EXFAT_CACHE_VALID)
		ei->cache_valid_id++;
}

void exfat_cache_inval_inode(struct inode *inode)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);

	spin_lock(&ei->cache_lru_lock);
	__exfat_cache_inval_inode(inode);
	spin_unlock(&ei->cache_lru_lock);
}

static inline int cache_contiguous(struct exfat_cache_id *cid,
		unsigned int dclus)
{
	cid->nr_contig++;
	return cid->dcluster + cid->nr_contig == dclus;
}

static inline void cache_init(struct exfat_cache_id *cid,
		unsigned int fclus, unsigned int dclus)
{
	cid->id = EXFAT_CACHE_VALID;
	cid->fcluster = fclus;
	cid->dcluster = dclus;
	cid->nr_contig = 0;
}

int exfat_get_cluster(struct inode *inode, unsigned int cluster,
		unsigned int *fclus, unsigned int *dclus,
		unsigned int *last_dclus, int allow_eof)
{
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	unsigned int limit = sbi->num_clusters;
	struct exfat_inode_info *ei = EXFAT_I(inode);
	struct exfat_cache_id cid;
	unsigned int content;

	if (ei->start_clu == EXFAT_FREE_CLUSTER) {
		exfat_fs_error(sb,
			"invalid access to exfat cache (entry 0x%08x)",
			ei->start_clu);
		return -EIO;
	}

	*fclus = 0;
	*dclus = ei->start_clu;
	*last_dclus = *dclus;

	/*
	 * Don`t use exfat_cache if zero offset or non-cluster allocation
	 */
	if (cluster == 0 || *dclus == EXFAT_EOF_CLUSTER)
		return 0;

	cache_init(&cid, EXFAT_EOF_CLUSTER, EXFAT_EOF_CLUSTER);

	if (exfat_cache_lookup(inode, cluster, &cid, fclus, dclus) ==
			EXFAT_EOF_CLUSTER) {
		/*
		 * dummy, always not contiguous
		 * This is reinitialized by cache_init(), later.
		 */
		WARN_ON(cid.id != EXFAT_CACHE_VALID ||
			cid.fcluster != EXFAT_EOF_CLUSTER ||
			cid.dcluster != EXFAT_EOF_CLUSTER ||
			cid.nr_contig != 0);
	}

	if (*fclus == cluster)
		return 0;

	while (*fclus < cluster) {
		/* prevent the infinite loop of cluster chain */
		if (*fclus > limit) {
			exfat_fs_error(sb,
				"detected the cluster chain loop (i_pos %u)",
				(*fclus));
			return -EIO;
		}

		if (exfat_ent_get(sb, *dclus, &content))
			return -EIO;

		*last_dclus = *dclus;
		*dclus = content;
		(*fclus)++;

		if (content == EXFAT_EOF_CLUSTER) {
			if (!allow_eof) {
				exfat_fs_error(sb,
				       "invalid cluster chain (i_pos %u, last_clus 0x%08x is EOF)",
				       *fclus, (*last_dclus));
				return -EIO;
			}

			break;
		}

		if (!cache_contiguous(&cid, *dclus))
			cache_init(&cid, *fclus, *dclus);
	}

	exfat_cache_add(inode, &cid);
	return 0;
}