[linux.git] / fs / fat / cache.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  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.
 */

#include <linux/slab.h>
#include "fat.h"

/* this must be > 0. */
#define FAT_MAX_CACHE	8

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

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

static inline int fat_max_cache(struct inode *inode)
{
	return FAT_MAX_CACHE;
}

static struct kmem_cache *fat_cache_cachep;

static void init_once(void *foo)
{
	struct fat_cache *cache = (struct fat_cache *)foo;

	INIT_LIST_HEAD(&cache->cache_list);
}

int __init fat_cache_init(void)
{
	fat_cache_cachep = kmem_cache_create("fat_cache",
				sizeof(struct fat_cache),
				0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
				init_once);
	if (fat_cache_cachep == NULL)
		return -ENOMEM;
	return 0;
}

void fat_cache_destroy(void)
{
	kmem_cache_destroy(fat_cache_cachep);
}

static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
{
	return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
}

static inline void fat_cache_free(struct fat_cache *cache)
{
	BUG_ON(!list_empty(&cache->cache_list));
	kmem_cache_free(fat_cache_cachep, cache);
}

static inline void fat_cache_update_lru(struct inode *inode,
					struct fat_cache *cache)
{
	if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
		list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
}

static int fat_cache_lookup(struct inode *inode, int fclus,
			    struct fat_cache_id *cid,
			    int *cached_fclus, int *cached_dclus)
{
	static struct fat_cache nohit = { .fcluster = 0, };

	struct fat_cache *hit = &nohit, *p;
	int offset = -1;

	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
	list_for_each_entry(p, &MSDOS_I(inode)->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) {
		fat_cache_update_lru(inode, hit);

		cid->id = MSDOS_I(inode)->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(&MSDOS_I(inode)->cache_lru_lock);

	return offset;
}

static struct fat_cache *fat_cache_merge(struct inode *inode,
					 struct fat_cache_id *new)
{
	struct fat_cache *p;

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

static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
{
	struct fat_cache *cache, *tmp;

	if (new->fcluster == -1) /* dummy cache */
		return;

	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
	if (new->id != FAT_CACHE_VALID &&
	    new->id != MSDOS_I(inode)->cache_valid_id)
		goto out;	/* this cache was invalidated */

	cache = fat_cache_merge(inode, new);
	if (cache == NULL) {
		if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
			MSDOS_I(inode)->nr_caches++;
			spin_unlock(&MSDOS_I(inode)->cache_lru_lock);

			tmp = fat_cache_alloc(inode);
			if (!tmp) {
				spin_lock(&MSDOS_I(inode)->cache_lru_lock);
				MSDOS_I(inode)->nr_caches--;
				spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
				return;
			}

			spin_lock(&MSDOS_I(inode)->cache_lru_lock);
			cache = fat_cache_merge(inode, new);
			if (cache != NULL) {
				MSDOS_I(inode)->nr_caches--;
				fat_cache_free(tmp);
				goto out_update_lru;
			}
			cache = tmp;
		} else {
			struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
			cache = list_entry(p, struct fat_cache, cache_list);
		}
		cache->fcluster = new->fcluster;
		cache->dcluster = new->dcluster;
		cache->nr_contig = new->nr_contig;
	}
out_update_lru:
	fat_cache_update_lru(inode, cache);
out:
	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
}

/*
 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 * fixes itself after a while.
 */
static void __fat_cache_inval_inode(struct inode *inode)
{
	struct msdos_inode_info *i = MSDOS_I(inode);
	struct fat_cache *cache;

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

void fat_cache_inval_inode(struct inode *inode)
{
	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
	__fat_cache_inval_inode(inode);
	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
}

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

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

int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	const int limit = sb->s_maxbytes >> sbi->cluster_bits;
	struct fat_entry fatent;
	struct fat_cache_id cid;
	int nr;

	BUG_ON(MSDOS_I(inode)->i_start == 0);

	*fclus = 0;
	*dclus = MSDOS_I(inode)->i_start;
	if (!fat_valid_entry(sbi, *dclus)) {
		fat_fs_error_ratelimit(sb,
			"%s: invalid start cluster (i_pos %lld, start %08x)",
			__func__, MSDOS_I(inode)->i_pos, *dclus);
		return -EIO;
	}
	if (cluster == 0)
		return 0;

	if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
		/*
		 * dummy, always not contiguous
		 * This is reinitialized by cache_init(), later.
		 */
		cache_init(&cid, -1, -1);
	}

	fatent_init(&fatent);
	while (*fclus < cluster) {
		/* prevent the infinite loop of cluster chain */
		if (*fclus > limit) {
			fat_fs_error_ratelimit(sb,
				"%s: detected the cluster chain loop (i_pos %lld)",
				__func__, MSDOS_I(inode)->i_pos);
			nr = -EIO;
			goto out;
		}

		nr = fat_ent_read(inode, &fatent, *dclus);
		if (nr < 0)
			goto out;
		else if (nr == FAT_ENT_FREE) {
			fat_fs_error_ratelimit(sb,
				"%s: invalid cluster chain (i_pos %lld)",
				__func__, MSDOS_I(inode)->i_pos);
			nr = -EIO;
			goto out;
		} else if (nr == FAT_ENT_EOF) {
			fat_cache_add(inode, &cid);
			goto out;
		}
		(*fclus)++;
		*dclus = nr;
		if (!cache_contiguous(&cid, *dclus))
			cache_init(&cid, *fclus, *dclus);
	}
	nr = 0;
	fat_cache_add(inode, &cid);
out:
	fatent_brelse(&fatent);
	return nr;
}

static int fat_bmap_cluster(struct inode *inode, int cluster)
{
	struct super_block *sb = inode->i_sb;
	int ret, fclus, dclus;

	if (MSDOS_I(inode)->i_start == 0)
		return 0;

	ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
	if (ret < 0)
		return ret;
	else if (ret == FAT_ENT_EOF) {
		fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
			     __func__, MSDOS_I(inode)->i_pos);
		return -EIO;
	}
	return dclus;
}

int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
			   sector_t last_block,
			   unsigned long *mapped_blocks, sector_t *bmap)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int cluster, offset;

	cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
	offset  = sector & (sbi->sec_per_clus - 1);
	cluster = fat_bmap_cluster(inode, cluster);
	if (cluster < 0)
		return cluster;
	else if (cluster) {
		*bmap = fat_clus_to_blknr(sbi, cluster) + offset;
		*mapped_blocks = sbi->sec_per_clus - offset;
		if (*mapped_blocks > last_block - sector)
			*mapped_blocks = last_block - sector;
	}

	return 0;
}

static int is_exceed_eof(struct inode *inode, sector_t sector,
			 sector_t *last_block, int create)
{
	struct super_block *sb = inode->i_sb;
	const unsigned long blocksize = sb->s_blocksize;
	const unsigned char blocksize_bits = sb->s_blocksize_bits;

	*last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
	if (sector >= *last_block) {
		if (!create)
			return 1;

		/*
		 * ->mmu_private can access on only allocation path.
		 * (caller must hold ->i_mutex)
		 */
		*last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
			>> blocksize_bits;
		if (sector >= *last_block)
			return 1;
	}

	return 0;
}

int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
	     unsigned long *mapped_blocks, int create, bool from_bmap)
{
	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
	sector_t last_block;

	*phys = 0;
	*mapped_blocks = 0;
	if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) {
		if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
			*phys = sector + sbi->dir_start;
			*mapped_blocks = 1;
		}
		return 0;
	}

	if (!from_bmap) {
		if (is_exceed_eof(inode, sector, &last_block, create))
			return 0;
	} else {
		last_block = inode->i_blocks >>
				(inode->i_sb->s_blocksize_bits - 9);
		if (sector >= last_block)
			return 0;
	}

	return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks,
				      phys);
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1da177e4 LT	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
5a0e3ad6	12	#include <linux/slab.h>
9e975dae	13	#include "fat.h"
1da177e4 LT	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
	32	static inline int fat_max_cache(struct inode *inode)
	33	{
	34	return FAT_MAX_CACHE;
	35	}
	36
e18b890b	37	static struct kmem_cache *fat_cache_cachep;
1da177e4	38
51cc5068	39	static void init_once(void *foo)
1da177e4 LT	40	{
	41	struct fat_cache cache = (struct fat_cache )foo;
	42
a35afb83	43	INIT_LIST_HEAD(&cache->cache_list);
1da177e4 LT	44	}
	45
	46	int __init fat_cache_init(void)
	47	{
	48	fat_cache_cachep = kmem_cache_create("fat_cache",
	49	sizeof(struct fat_cache),
4b6a9316	50	0, SLAB_RECLAIM_ACCOUNT\|SLAB_MEM_SPREAD,
20c2df83	51	init_once);
1da177e4 LT	52	if (fat_cache_cachep == NULL)
	53	return -ENOMEM;
	54	return 0;
	55	}
	56
ef6689ef	57	void fat_cache_destroy(void)
1da177e4	58	{
1a1d92c1	59	kmem_cache_destroy(fat_cache_cachep);
1da177e4 LT	60	}
	61
	62	static inline struct fat_cache fat_cache_alloc(struct inode inode)
	63	{
8f593427	64	return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
1da177e4 LT	65	}
	66
	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
	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
	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
	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
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);
70030929 OH	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
1da177e4 LT	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	*/
	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)) {
c9051829 CJB	192	cache = list_entry(i->cache_lru.next,
c9051829 CJB	193	struct fat_cache, cache_list);
1da177e4 LT	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
	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
	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
	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
	225	int fat_get_cluster(struct inode inode, int cluster, int fclus, int *dclus)
	226	{
	227	struct super_block *sb = inode->i_sb;
0afa9626 OH	228	struct msdos_sb_info *sbi = MSDOS_SB(sb);
0afa9626 OH	229	const int limit = sb->s_maxbytes >> sbi->cluster_bits;
1da177e4 LT	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;
0afa9626 OH	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	}
1da177e4 LT	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) {
aaa04b48	259	fat_fs_error_ratelimit(sb,
0afa9626 OH	260	"%s: detected the cluster chain loop (i_pos %lld)",
0afa9626 OH	261	__func__, MSDOS_I(inode)->i_pos);
1da177e4 LT	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) {
c9051829	270	fat_fs_error_ratelimit(sb,
0afa9626 OH	271	"%s: invalid cluster chain (i_pos %lld)",
0afa9626 OH	272	__func__, MSDOS_I(inode)->i_pos);
1da177e4 LT	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
	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) {
85c78591	303	fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
8e24eea7	304	__func__, MSDOS_I(inode)->i_pos);
1da177e4 LT	305	return -EIO;
	306	}
	307	return dclus;
	308	}
	309
16fab201 NJ	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)
1da177e4 LT	313	{
	314	struct super_block *sb = inode->i_sb;
	315	struct msdos_sb_info *sbi = MSDOS_SB(sb);
16fab201 NJ	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
	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;
2bdf67eb OH	337	const unsigned long blocksize = sb->s_blocksize;
2bdf67eb OH	338	const unsigned char blocksize_bits = sb->s_blocksize_bits;
16fab201 NJ	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
	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);
1da177e4	362	sector_t last_block;
1da177e4 LT	363
1da177e4 LT	364	*phys = 0;
e5174baa	365	*mapped_blocks = 0;
306790f7	366	if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) {
e5174baa	367	if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
1da177e4	368	*phys = sector + sbi->dir_start;
e5174baa OH	369	*mapped_blocks = 1;
e5174baa OH	370	}
1da177e4 LT	371	return 0;
1da177e4 LT	372	}
2bdf67eb	373
16fab201 NJ	374	if (!from_bmap) {
16fab201 NJ	375	if (is_exceed_eof(inode, sector, &last_block, create))
2bdf67eb	376	return 0;
16fab201 NJ	377	} else {
	378	last_block = inode->i_blocks >>
	379	(inode->i_sb->s_blocksize_bits - 9);
2bdf67eb OH	380	if (sector >= last_block)
	381	return 0;
	382	}
1da177e4	383
16fab201 NJ	384	return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks,
16fab201 NJ	385	phys);
1da177e4	386	}