path: root/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) +