linux/fs/fat/fat.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _FAT_H
#define _FAT_H

#include <linux/buffer_head.h>
#include <linux/nls.h>
#include <linux/hash.h>
#include <linux/ratelimit.h>
#include <linux/msdos_fs.h>

/*
 * vfat shortname flags
 */
#define VFAT_SFN_DISPLAY_LOWER	0x0001 /* convert to lowercase for display */
#define VFAT_SFN_DISPLAY_WIN95	0x0002 /* emulate win95 rule for display */
#define VFAT_SFN_DISPLAY_WINNT	0x0004 /* emulate winnt rule for display */
#define VFAT_SFN_CREATE_WIN95	0x0100 /* emulate win95 rule for create */
#define VFAT_SFN_CREATE_WINNT	0x0200 /* emulate winnt rule for create */

#define FAT_ERRORS_CONT		1      /* ignore error and continue */
#define FAT_ERRORS_PANIC	2      /* panic on error */
#define FAT_ERRORS_RO		3      /* remount r/o on error */

#define FAT_NFS_STALE_RW	1      /* NFS RW support, can cause ESTALE */
#define FAT_NFS_NOSTALE_RO	2      /* NFS RO support, no ESTALE issue */

struct fat_mount_options {
	kuid_t fs_uid;
	kgid_t fs_gid;
	unsigned short fs_fmask;
	unsigned short fs_dmask;
	unsigned short codepage;   /* Codepage for shortname conversions */
	int time_offset;	   /* Offset of timestamps from UTC (in minutes) */
	char *iocharset;           /* Charset used for filename input/display */
	unsigned short shortname;  /* flags for shortname display/create rule */
	unsigned char name_check;  /* r = relaxed, n = normal, s = strict */
	unsigned char errors;	   /* On error: continue, panic, remount-ro */
	unsigned char nfs;	  /* NFS support: nostale_ro, stale_rw */
	unsigned short allow_utime;/* permission for setting the [am]time */
	unsigned quiet:1,          /* set = fake successful chmods and chowns */
		 showexec:1,       /* set = only set x bit for com/exe/bat */
		 sys_immutable:1,  /* set = system files are immutable */
		 dotsOK:1,         /* set = hidden and system files are named '.filename' */
		 isvfat:1,         /* 0=no vfat long filename support, 1=vfat support */
		 utf8:1,	   /* Use of UTF-8 character set (Default) */
		 unicode_xlate:1,  /* create escape sequences for unhandled Unicode */
		 numtail:1,        /* Does first alias have a numeric '~1' type tail? */
		 flush:1,	   /* write things quickly */
		 nocase:1,	   /* Does this need case conversion? 0=need case conversion*/
		 usefree:1,	   /* Use free_clusters for FAT32 */
		 tz_set:1,	   /* Filesystem timestamps' offset set */
		 rodir:1,	   /* allow ATTR_RO for directory */
		 discard:1,	   /* Issue discard requests on deletions */
		 dos1xfloppy:1;	   /* Assume default BPB for DOS 1.x floppies */
};

#define FAT_HASH_BITS	8
#define FAT_HASH_SIZE	(1UL << FAT_HASH_BITS)

/*
 * MS-DOS file system in-core superblock data
 */
struct msdos_sb_info {
	unsigned short sec_per_clus;  /* sectors/cluster */
	unsigned short cluster_bits;  /* log2(cluster_size) */
	unsigned int cluster_size;    /* cluster size */
	unsigned char fats, fat_bits; /* number of FATs, FAT bits (12,16 or 32) */
	unsigned short fat_start;
	unsigned long fat_length;     /* FAT start & length (sec.) */
	unsigned long dir_start;
	unsigned short dir_entries;   /* root dir start & entries */
	unsigned long data_start;     /* first data sector */
	unsigned long max_cluster;    /* maximum cluster number */
	unsigned long root_cluster;   /* first cluster of the root directory */
	unsigned long fsinfo_sector;  /* sector number of FAT32 fsinfo */
	struct mutex fat_lock;
	struct mutex nfs_build_inode_lock;
	struct mutex s_lock;
	unsigned int prev_free;      /* previously allocated cluster number */
	unsigned int free_clusters;  /* -1 if undefined */
	unsigned int free_clus_valid; /* is free_clusters valid? */
	struct fat_mount_options options;
	struct nls_table *nls_disk;   /* Codepage used on disk */
	struct nls_table *nls_io;     /* Charset used for input and display */
	const void *dir_ops;	      /* Opaque; default directory operations */
	int dir_per_block;	      /* dir entries per block */
	int dir_per_block_bits;	      /* log2(dir_per_block) */
	unsigned int vol_id;		/*volume ID*/

	int fatent_shift;
	const struct fatent_operations *fatent_ops;
	struct inode *fat_inode;
	struct inode *fsinfo_inode;

	struct ratelimit_state ratelimit;

	spinlock_t inode_hash_lock;
	struct hlist_head inode_hashtable[FAT_HASH_SIZE];

	spinlock_t dir_hash_lock;
	struct hlist_head dir_hashtable[FAT_HASH_SIZE];

	unsigned int dirty;           /* fs state before mount */
	struct rcu_head rcu;
};

#define FAT_CACHE_VALID	0	/* special case for valid cache */

/*
 * MS-DOS file system inode data in memory
 */
struct msdos_inode_info {
	spinlock_t cache_lru_lock;
	struct list_head cache_lru;
	int nr_caches;
	/* for avoiding the race between fat_free() and fat_get_cluster() */
	unsigned int cache_valid_id;

	/* NOTE: mmu_private is 64bits, so must hold ->i_mutex to access */
	loff_t mmu_private;	/* physically allocated size */

	int i_start;		/* first cluster or 0 */
	int i_logstart;		/* logical first cluster */
	int i_attrs;		/* unused attribute bits */
	loff_t i_pos;		/* on-disk position of directory entry or 0 */
	struct hlist_node i_fat_hash;	/* hash by i_location */
	struct hlist_node i_dir_hash;	/* hash by i_logstart */
	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
	struct inode vfs_inode;
};

struct fat_slot_info {
	loff_t i_pos;		/* on-disk position of directory entry */
	loff_t slot_off;	/* offset for slot or de start */
	int nr_slots;		/* number of slots + 1(de) in filename */
	struct msdos_dir_entry *de;
	struct buffer_head *bh;
};

static inline struct msdos_sb_info *MSDOS_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}

/*
 * Functions that determine the variant of the FAT file system (i.e.,
 * whether this is FAT12, FAT16 or FAT32.
 */
static inline bool is_fat12(const struct msdos_sb_info *sbi)
{
	return sbi->fat_bits == 12;
}

static inline bool is_fat16(const struct msdos_sb_info *sbi)
{
	return sbi->fat_bits == 16;
}

static inline bool is_fat32(const struct msdos_sb_info *sbi)
{
	return sbi->fat_bits == 32;
}

/* Maximum number of clusters */
static inline u32 max_fat(struct super_block *sb)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);

	return is_fat32(sbi) ? MAX_FAT32 :
		is_fat16(sbi) ? MAX_FAT16 : MAX_FAT12;
}

static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
{
	return container_of(inode, struct msdos_inode_info, vfs_inode);
}

/*
 * If ->i_mode can't hold S_IWUGO (i.e. ATTR_RO), we use ->i_attrs to
 * save ATTR_RO instead of ->i_mode.
 *
 * If it's directory and !sbi->options.rodir, ATTR_RO isn't read-only
 * bit, it's just used as flag for app.
 */
static inline int fat_mode_can_hold_ro(struct inode *inode)
{
	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
	umode_t mask;

	if (S_ISDIR(inode->i_mode)) {
		if (!sbi->options.rodir)
			return 0;
		mask = ~sbi->options.fs_dmask;
	} else
		mask = ~sbi->options.fs_fmask;

	if (!(mask & S_IWUGO))
		return 0;
	return 1;
}

/* Convert attribute bits and a mask to the UNIX mode. */
static inline umode_t fat_make_mode(struct msdos_sb_info *sbi,
				   u8 attrs, umode_t mode)
{
	if (attrs & ATTR_RO && !((attrs & ATTR_DIR) && !sbi->options.rodir))
		mode &= ~S_IWUGO;

	if (attrs & ATTR_DIR)
		return (mode & ~sbi->options.fs_dmask) | S_IFDIR;
	else
		return (mode & ~sbi->options.fs_fmask) | S_IFREG;
}

/* Return the FAT attribute byte for this inode */
static inline u8 fat_make_attrs(struct inode *inode)
{
	u8 attrs = MSDOS_I(inode)->i_attrs;
	if (S_ISDIR(inode->i_mode))
		attrs |= ATTR_DIR;
	if (fat_mode_can_hold_ro(inode) && !(inode->i_mode & S_IWUGO))
		attrs |= ATTR_RO;
	return attrs;
}

static inline void fat_save_attrs(struct inode *inode, u8 attrs)
{
	if (fat_mode_can_hold_ro(inode))
		MSDOS_I(inode)->i_attrs = attrs & ATTR_UNUSED;
	else
		MSDOS_I(inode)->i_attrs = attrs & (ATTR_UNUSED | ATTR_RO);
}

static inline unsigned char fat_checksum(const __u8 *name)
{
	unsigned char s = name[0];
	s = (s<<7) + (s>>1) + name[1];	s = (s<<7) + (s>>1) + name[2];
	s = (s<<7) + (s>>1) + name[3];	s = (s<<7) + (s>>1) + name[4];
	s = (s<<7) + (s>>1) + name[5];	s = (s<<7) + (s>>1) + name[6];
	s = (s<<7) + (s>>1) + name[7];	s = (s<<7) + (s>>1) + name[8];
	s = (s<<7) + (s>>1) + name[9];	s = (s<<7) + (s>>1) + name[10];
	return s;
}

static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus)
{
	return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus
		+ sbi->data_start;
}

static inline void fat_get_blknr_offset(struct msdos_sb_info *sbi,
				loff_t i_pos, sector_t *blknr, int *offset)
{
	*blknr = i_pos >> sbi->dir_per_block_bits;
	*offset = i_pos & (sbi->dir_per_block - 1);
}

static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
					struct inode *inode)
{
	loff_t i_pos;
#if BITS_PER_LONG == 32
	spin_lock(&sbi->inode_hash_lock);
#endif
	i_pos = MSDOS_I(inode)->i_pos;
#if BITS_PER_LONG == 32
	spin_unlock(&sbi->inode_hash_lock);
#endif
	return i_pos;
}

static inline void fat16_towchar(wchar_t *dst, const __u8 *src, size_t len)
{
#ifdef __BIG_ENDIAN
	while (len--) {
		*dst++ = src[0] | (src[1] << 8);
		src += 2;
	}
#else
	memcpy(dst, src, len * 2);
#endif
}

static inline int fat_get_start(const struct msdos_sb_info *sbi,
				const struct msdos_dir_entry *de)
{
	int cluster = le16_to_cpu(de->start);
	if (is_fat32(sbi))
		cluster |= (le16_to_cpu(de->starthi) << 16);
	return cluster;
}

static inline void fat_set_start(struct msdos_dir_entry *de, int cluster)
{
	de->start   = cpu_to_le16(cluster);
	de->starthi = cpu_to_le16(cluster >> 16);
}

static inline void fatwchar_to16(__u8 *dst, const wchar_t *src, size_t len)
{
#ifdef __BIG_ENDIAN
	while (len--) {
		dst[0] = *src & 0x00FF;
		dst[1] = (*src & 0xFF00) >> 8;
		dst += 2;
		src++;
	}
#else
	memcpy(dst, src, len * 2);
#endif
}

/* fat/cache.c */
extern void fat_cache_inval_inode(struct inode *inode);
extern int fat_get_cluster(struct inode *inode, int cluster,
			   int *fclus, int *dclus);
extern int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
				  sector_t last_block,
				  unsigned long *mapped_blocks, sector_t *bmap);
extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
		    unsigned long *mapped_blocks, int create, bool from_bmap);

/* fat/dir.c */
extern const struct file_operations fat_dir_operations;
extern int fat_search_long(struct inode *inode, const unsigned char *name,
			   int name_len, struct fat_slot_info *sinfo);
extern int fat_dir_empty(struct inode *dir);
extern int fat_subdirs(struct inode *dir);
extern int fat_scan(struct inode *dir, const unsigned char *name,
		    struct fat_slot_info *sinfo);
extern int fat_scan_logstart(struct inode *dir, int i_logstart,
			     struct fat_slot_info *sinfo);
extern int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
				struct msdos_dir_entry **de);
extern int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts);
extern int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
			   struct fat_slot_info *sinfo);
extern int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo);

/* fat/fatent.c */
struct fat_entry {
	int entry;
	union {
		u8 *ent12_p[2];
		__le16 *ent16_p;
		__le32 *ent32_p;
	} u;
	int nr_bhs;
	struct buffer_head *bhs[2];
	struct inode *fat_inode;
};

static inline void fatent_init(struct fat_entry *fatent)
{
	fatent->nr_bhs = 0;
	fatent->entry = 0;
	fatent->u.ent32_p = NULL;
	fatent->bhs[0] = fatent->bhs[1] = NULL;
	fatent->fat_inode = NULL;
}

static inline void fatent_set_entry(struct fat_entry *fatent, int entry)
{
	fatent->entry = entry;
	fatent->u.ent32_p = NULL;
}

static inline void fatent_brelse(struct fat_entry *fatent)
{
	int i;
	fatent->u.ent32_p = NULL;
	for (i = 0; i < fatent->nr_bhs; i++)
		brelse(fatent->bhs[i]);
	fatent->nr_bhs = 0;
	fatent->bhs[0] = fatent->bhs[1] = NULL;
	fatent->fat_inode = NULL;
}

static inline bool fat_valid_entry(struct msdos_sb_info *sbi, int entry)
{
	return FAT_START_ENT <= entry && entry < sbi->max_cluster;
}

extern void fat_ent_access_init(struct super_block *sb);
extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent,
			int entry);
extern int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
			 int new, int wait);
extern int fat_alloc_clusters(struct inode *inode, int *cluster,
			      int nr_cluster);
extern int fat_free_clusters(struct inode *inode, int cluster);
extern int fat_count_free_clusters(struct super_block *sb);
extern int fat_trim_fs(struct inode *inode, struct fstrim_range *range);

/* fat/file.c */
extern long fat_generic_ioctl(struct file *filp, unsigned int cmd,
			      unsigned long arg);
extern const struct file_operations fat_file_operations;
extern const struct inode_operations fat_file_inode_operations;
extern int fat_setattr(struct dentry *dentry, struct iattr *attr);
extern void fat_truncate_blocks(struct inode *inode, loff_t offset);
extern int fat_getattr(const struct path *path, struct kstat *stat,
		       u32 request_mask, unsigned int flags);
extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
			  int datasync);

/* fat/inode.c */
extern int fat_block_truncate_page(struct inode *inode, loff_t from);
extern void fat_attach(struct inode *inode, loff_t i_pos);
extern void fat_detach(struct inode *inode);
extern struct inode *fat_iget(struct super_block *sb, loff_t i_pos);
extern struct inode *fat_build_inode(struct super_block *sb,
			struct msdos_dir_entry *de, loff_t i_pos);
extern int fat_sync_inode(struct inode *inode);
extern int fat_fill_super(struct super_block *sb, void *data, int silent,
			  int isvfat, void (*setup)(struct super_block *));
extern int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de);

extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
			    struct inode *i2);
static inline unsigned long fat_dir_hash(int logstart)
{
	return hash_32(logstart, FAT_HASH_BITS);
}
extern int fat_add_cluster(struct inode *inode);

/* fat/misc.c */
extern __printf(3, 4) __cold
void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...);
#define fat_fs_error(sb, fmt, args...)		\
	__fat_fs_error(sb, 1, fmt , ## args)
#define fat_fs_error_ratelimit(sb, fmt, args...) \
	__fat_fs_error(sb, __ratelimit(&MSDOS_SB(sb)->ratelimit), fmt , ## args)
__printf(3, 4) __cold
void fat_msg(struct super_block *sb, const char *level, const char *fmt, ...);
#define fat_msg_ratelimit(sb, level, fmt, args...)	\
	do {	\
			if (__ratelimit(&MSDOS_SB(sb)->ratelimit))	\
				fat_msg(sb, level, fmt, ## args);	\
	 } while (0)
extern int fat_clusters_flush(struct super_block *sb);
extern int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster);
extern void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
			      __le16 __time, __le16 __date, u8 time_cs);
extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
			      __le16 *time, __le16 *date, u8 *time_cs);
extern int fat_truncate_time(struct inode *inode, struct timespec64 *now,
			     int flags);
extern int fat_update_time(struct inode *inode, struct timespec64 *now,
			   int flags);
extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);

int fat_cache_init(void);
void fat_cache_destroy(void);

/* fat/nfs.c */
extern const struct export_operations fat_export_ops;
extern const struct export_operations fat_export_ops_nostale;

/* helper for printk */
typedef unsigned long long	llu;

#endif /* !_FAT_H */