inode.c

linux环境下基于FAT的文件系统的通用代码

static void __exit fat_destroy_inodecache(void)
{
	kmem_cache_destroy(fat_inode_cachep);
}

static int fat_remount(struct super_block *sb, int *flags, char *data)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	*flags |= MS_NODIRATIME | (sbi->options.isvfat ? 0 : MS_NOATIME);
	return 0;
}

static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);

	/* If the count of free cluster is still unknown, counts it here. */
	if (sbi->free_clusters == -1 || !sbi->free_clus_valid) {
		int err = fat_count_free_clusters(dentry->d_sb);
		if (err)
			return err;
	}

	buf->f_type = dentry->d_sb->s_magic;
	buf->f_bsize = sbi->cluster_size;
	buf->f_blocks = sbi->max_cluster - FAT_START_ENT;
	buf->f_bfree = sbi->free_clusters;
	buf->f_bavail = sbi->free_clusters;
	buf->f_namelen = sbi->options.isvfat ? 260 : 12;

	return 0;
}

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 int fat_write_inode(struct inode *inode, int wait)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct buffer_head *bh;
	struct msdos_dir_entry *raw_entry;
	loff_t i_pos;
	int err;

	if (inode->i_ino == MSDOS_ROOT_INO)
		return 0;

retry:
	i_pos = fat_i_pos_read(sbi, inode);
	if (!i_pos)
		return 0;

	bh = sb_bread(sb, i_pos >> sbi->dir_per_block_bits);
	if (!bh) {
		printk(KERN_ERR "FAT: unable to read inode block "
		       "for updating (i_pos %lld)\n", i_pos);
		return -EIO;
	}
	spin_lock(&sbi->inode_hash_lock);
	if (i_pos != MSDOS_I(inode)->i_pos) {
		spin_unlock(&sbi->inode_hash_lock);
		brelse(bh);
		goto retry;
	}

	raw_entry = &((struct msdos_dir_entry *) (bh->b_data))
	    [i_pos & (sbi->dir_per_block - 1)];
	if (S_ISDIR(inode->i_mode))
		raw_entry->size = 0;
	else
		raw_entry->size = cpu_to_le32(inode->i_size);
	raw_entry->attr = fat_make_attrs(inode);
	raw_entry->start = cpu_to_le16(MSDOS_I(inode)->i_logstart);
	raw_entry->starthi = cpu_to_le16(MSDOS_I(inode)->i_logstart >> 16);
	fat_time_unix2fat(sbi, &inode->i_mtime, &raw_entry->time,
			  &raw_entry->date, NULL);
	if (sbi->options.isvfat) {
		__le16 atime;
		fat_time_unix2fat(sbi, &inode->i_ctime, &raw_entry->ctime,
				  &raw_entry->cdate, &raw_entry->ctime_cs);
		fat_time_unix2fat(sbi, &inode->i_atime, &atime,
				  &raw_entry->adate, NULL);
	}
	spin_unlock(&sbi->inode_hash_lock);
	mark_buffer_dirty(bh);
	err = 0;
	if (wait)
		err = sync_dirty_buffer(bh);
	brelse(bh);
	return err;
}

int fat_sync_inode(struct inode *inode)
{
	return fat_write_inode(inode, 1);
}

EXPORT_SYMBOL_GPL(fat_sync_inode);

static int fat_show_options(struct seq_file *m, struct vfsmount *mnt);
static const struct super_operations fat_sops = {
	.alloc_inode	= fat_alloc_inode,
	.destroy_inode	= fat_destroy_inode,
	.write_inode	= fat_write_inode,
	.delete_inode	= fat_delete_inode,
	.put_super	= fat_put_super,
	.write_super	= fat_write_super,
	.statfs		= fat_statfs,
	.clear_inode	= fat_clear_inode,
	.remount_fs	= fat_remount,

	.show_options	= fat_show_options,
};

/*
 * a FAT file handle with fhtype 3 is
 *  0/  i_ino - for fast, reliable lookup if still in the cache
 *  1/  i_generation - to see if i_ino is still valid
 *          bit 0 == 0 iff directory
 *  2/  i_pos(8-39) - if ino has changed, but still in cache
 *  3/  i_pos(4-7)|i_logstart - to semi-verify inode found at i_pos
 *  4/  i_pos(0-3)|parent->i_logstart - maybe used to hunt for the file on disc
 *
 * Hack for NFSv2: Maximum FAT entry number is 28bits and maximum
 * i_pos is 40bits (blocknr(32) + dir offset(8)), so two 4bits
 * of i_logstart is used to store the directory entry offset.
 */

static struct dentry *fat_fh_to_dentry(struct super_block *sb,
		struct fid *fid, int fh_len, int fh_type)
{
	struct inode *inode = NULL;
	struct dentry *result;
	u32 *fh = fid->raw;

	if (fh_len < 5 || fh_type != 3)
		return NULL;

	inode = ilookup(sb, fh[0]);
	if (!inode || inode->i_generation != fh[1]) {
		if (inode)
			iput(inode);
		inode = NULL;
	}
	if (!inode) {
		loff_t i_pos;
		int i_logstart = fh[3] & 0x0fffffff;

		i_pos = (loff_t)fh[2] << 8;
		i_pos |= ((fh[3] >> 24) & 0xf0) | (fh[4] >> 28);

		/* try 2 - see if i_pos is in F-d-c
		 * require i_logstart to be the same
		 * Will fail if you truncate and then re-write
		 */

		inode = fat_iget(sb, i_pos);
		if (inode && MSDOS_I(inode)->i_logstart != i_logstart) {
			iput(inode);
			inode = NULL;
		}
	}

	/*
	 * For now, do nothing if the inode is not found.
	 *
	 * What we could do is:
	 *
	 *	- follow the file starting at fh[4], and record the ".." entry,
	 *	  and the name of the fh[2] entry.
	 *	- then follow the ".." file finding the next step up.
	 *
	 * This way we build a path to the root of the tree. If this works, we
	 * lookup the path and so get this inode into the cache.  Finally try
	 * the fat_iget lookup again.  If that fails, then we are totally out
	 * of luck.  But all that is for another day
	 */
	result = d_obtain_alias(inode);
	if (!IS_ERR(result))
		result->d_op = sb->s_root->d_op;
	return result;
}

static int
fat_encode_fh(struct dentry *de, __u32 *fh, int *lenp, int connectable)
{
	int len = *lenp;
	struct inode *inode =  de->d_inode;
	u32 ipos_h, ipos_m, ipos_l;

	if (len < 5)
		return 255; /* no room */

	ipos_h = MSDOS_I(inode)->i_pos >> 8;
	ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
	ipos_l = (MSDOS_I(inode)->i_pos & 0x0f) << 28;
	*lenp = 5;
	fh[0] = inode->i_ino;
	fh[1] = inode->i_generation;
	fh[2] = ipos_h;
	fh[3] = ipos_m | MSDOS_I(inode)->i_logstart;
	spin_lock(&de->d_lock);
	fh[4] = ipos_l | MSDOS_I(de->d_parent->d_inode)->i_logstart;
	spin_unlock(&de->d_lock);
	return 3;
}

static struct dentry *fat_get_parent(struct dentry *child)
{
	struct super_block *sb = child->d_sb;
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	loff_t i_pos;
	struct dentry *parent;
	struct inode *inode;
	int err;

	lock_super(sb);

	err = fat_get_dotdot_entry(child->d_inode, &bh, &de, &i_pos);
	if (err) {
		parent = ERR_PTR(err);
		goto out;
	}
	inode = fat_build_inode(sb, de, i_pos);
	brelse(bh);

	parent = d_obtain_alias(inode);
	if (!IS_ERR(parent))
		parent->d_op = sb->s_root->d_op;
out:
	unlock_super(sb);

	return parent;
}

static const struct export_operations fat_export_ops = {
	.encode_fh	= fat_encode_fh,
	.fh_to_dentry	= fat_fh_to_dentry,
	.get_parent	= fat_get_parent,
};

static int fat_show_options(struct seq_file *m, struct vfsmount *mnt)
{
	struct msdos_sb_info *sbi = MSDOS_SB(mnt->mnt_sb);
	struct fat_mount_options *opts = &sbi->options;
	int isvfat = opts->isvfat;

	if (opts->fs_uid != 0)
		seq_printf(m, ",uid=%u", opts->fs_uid);
	if (opts->fs_gid != 0)
		seq_printf(m, ",gid=%u", opts->fs_gid);
	seq_printf(m, ",fmask=%04o", opts->fs_fmask);
	seq_printf(m, ",dmask=%04o", opts->fs_dmask);
	if (opts->allow_utime)
		seq_printf(m, ",allow_utime=%04o", opts->allow_utime);
	if (sbi->nls_disk)
		seq_printf(m, ",codepage=%s", sbi->nls_disk->charset);
	if (isvfat) {
		if (sbi->nls_io)
			seq_printf(m, ",iocharset=%s", sbi->nls_io->charset);

		switch (opts->shortname) {
		case VFAT_SFN_DISPLAY_WIN95 | VFAT_SFN_CREATE_WIN95:
			seq_puts(m, ",shortname=win95");
			break;
		case VFAT_SFN_DISPLAY_WINNT | VFAT_SFN_CREATE_WINNT:
			seq_puts(m, ",shortname=winnt");
			break;
		case VFAT_SFN_DISPLAY_WINNT | VFAT_SFN_CREATE_WIN95:
			seq_puts(m, ",shortname=mixed");
			break;
		case VFAT_SFN_DISPLAY_LOWER | VFAT_SFN_CREATE_WIN95:
			/* seq_puts(m, ",shortname=lower"); */
			break;
		default:
			seq_puts(m, ",shortname=unknown");
			break;
		}
	}
	if (opts->name_check != 'n')
		seq_printf(m, ",check=%c", opts->name_check);
	if (opts->usefree)
		seq_puts(m, ",usefree");
	if (opts->quiet)
		seq_puts(m, ",quiet");
	if (opts->showexec)
		seq_puts(m, ",showexec");
	if (opts->sys_immutable)
		seq_puts(m, ",sys_immutable");
	if (!isvfat) {
		if (opts->dotsOK)
			seq_puts(m, ",dotsOK=yes");
		if (opts->nocase)
			seq_puts(m, ",nocase");
	} else {
		if (opts->utf8)
			seq_puts(m, ",utf8");
		if (opts->unicode_xlate)
			seq_puts(m, ",uni_xlate");
		if (!opts->numtail)
			seq_puts(m, ",nonumtail");
		if (opts->rodir)
			seq_puts(m, ",rodir");
	}
	if (opts->flush)
		seq_puts(m, ",flush");
	if (opts->tz_utc)
		seq_puts(m, ",tz=UTC");

	return 0;
}

enum {
	Opt_check_n, Opt_check_r, Opt_check_s, Opt_uid, Opt_gid,
	Opt_umask, Opt_dmask, Opt_fmask, Opt_allow_utime, Opt_codepage,
	Opt_usefree, Opt_nocase, Opt_quiet, Opt_showexec, Opt_debug,
	Opt_immutable, Opt_dots, Opt_nodots,
	Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
	Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
	Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
	Opt_obsolate, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err,
};

static const match_table_t fat_tokens = {
	{Opt_check_r, "check=relaxed"},
	{Opt_check_s, "check=strict"},
	{Opt_check_n, "check=normal"},
	{Opt_check_r, "check=r"},
	{Opt_check_s, "check=s"},
	{Opt_check_n, "check=n"},
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_umask, "umask=%o"},
	{Opt_dmask, "dmask=%o"},
	{Opt_fmask, "fmask=%o"},
	{Opt_allow_utime, "allow_utime=%o"},
	{Opt_codepage, "codepage=%u"},
	{Opt_usefree, "usefree"},
	{Opt_nocase, "nocase"},
	{Opt_quiet, "quiet"},
	{Opt_showexec, "showexec"},
	{Opt_debug, "debug"},
	{Opt_immutable, "sys_immutable"},
	{Opt_obsolate, "conv=binary"},
	{Opt_obsolate, "conv=text"},
	{Opt_obsolate, "conv=auto"},
	{Opt_obsolate, "conv=b"},
	{Opt_obsolate, "conv=t"},
	{Opt_obsolate, "conv=a"},
	{Opt_obsolate, "fat=%u"},
	{Opt_obsolate, "blocksize=%u"},
	{Opt_obsolate, "cvf_format=%20s"},
	{Opt_obsolate, "cvf_options=%100s"},
	{Opt_obsolate, "posix"},
	{Opt_flush, "flush"},
	{Opt_tz_utc, "tz=UTC"},
	{Opt_err, NULL},
};
static const match_table_t msdos_tokens = {
	{Opt_nodots, "nodots"},
	{Opt_nodots, "dotsOK=no"},
	{Opt_dots, "dots"},
	{Opt_dots, "dotsOK=yes"},
	{Opt_err, NULL}
};
static const match_table_t vfat_tokens = {
	{Opt_charset, "iocharset=%s"},
	{Opt_shortname_lower, "shortname=lower"},
	{Opt_shortname_win95, "shortname=win95"},
	{Opt_shortname_winnt, "shortname=winnt"},
	{Opt_shortname_mixed, "shortname=mixed"},
	{Opt_utf8_no, "utf8=0"},		/* 0 or no or false */
	{Opt_utf8_no, "utf8=no"},
	{Opt_utf8_no, "utf8=false"},
	{Opt_utf8_yes, "utf8=1"},		/* empty or 1 or yes or true */
	{Opt_utf8_yes, "utf8=yes"},
	{Opt_utf8_yes, "utf8=true"},
	{Opt_utf8_yes, "utf8"},
	{Opt_uni_xl_no, "uni_xlate=0"},		/* 0 or no or false */
	{Opt_uni_xl_no, "uni_xlate=no"},
	{Opt_uni_xl_no, "uni_xlate=false"},
	{Opt_uni_xl_yes, "uni_xlate=1"},	/* empty or 1 or yes or true */
	{Opt_uni_xl_yes, "uni_xlate=yes"},
	{Opt_uni_xl_yes, "uni_xlate=true"},
	{Opt_uni_xl_yes, "uni_xlate"},
	{Opt_nonumtail_no, "nonumtail=0"},	/* 0 or no or false */
	{Opt_nonumtail_no, "nonumtail=no"},
	{Opt_nonumtail_no, "nonumtail=false"},
	{Opt_nonumtail_yes, "nonumtail=1"},	/* empty or 1 or yes or true */
	{Opt_nonumtail_yes, "nonumtail=yes"},
	{Opt_nonumtail_yes, "nonumtail=true"},
	{Opt_nonumtail_yes, "nonumtail"},
	{Opt_rodir, "rodir"},
	{Opt_err, NULL}
};

static int parse_options(char *options, int is_vfat, int silent, int *debug,
			 struct fat_mount_options *opts)
{
	char *p;
	substring_t args[MAX_OPT_ARGS];
	int option;
	char *iocharset;

	opts->isvfat = is_vfat;

	opts->fs_uid = current_uid();
	opts->fs_gid = current_gid();
	opts->fs_fmask = opts->fs_dmask = current->fs->umask;
	opts->allow_utime = -1;
	opts->codepage = fat_default_codepage;
	opts->iocharset = fat_default_iocharset;
	if (is_vfat) {
		opts->shortname = VFAT_SFN_DISPLAY_LOWER|VFAT_SFN_CREATE_WIN95;
		opts->rodir = 0;
	} else {
		opts->shortname = 0;
		opts->rodir = 1;
	}
	opts->name_check = 'n';
	opts->quiet = opts->showexec = opts->sys_immutable = opts->dotsOK =  0;
	opts->utf8 = opts->unicode_xlate = 0;
	opts->numtail = 1;
	opts->usefree = opts->nocase = 0;
	opts->tz_utc = 0;
	*debug = 0;

	if (!options)
		goto out;

	while ((p = strsep(&options, ",")) != NULL) {
		int token;
		if (!*p)
			continue;

		token = match_token(p, fat_tokens, args);
		if (token == Opt_err) {
			if (is_vfat)
				token = match_token(p, vfat_tokens, args);
			else
				token = match_token(p, msdos_tokens, args);
		}
		switch (token) {
		case Opt_check_s:
			opts->name_check = 's';
			break;
		case Opt_check_r:
			opts->name_check = 'r';
			break;
		case Opt_check_n:
			opts->name_check = 'n';
			break;
		case Opt_usefree:
			opts->usefree = 1;
			break;
		case Opt_nocase:
			if (!is_vfat)
				opts->nocase = 1;
			else {
				/* for backward compatibility */
				opts->shortname = VFAT_SFN_DISPLAY_WIN95
					| VFAT_SFN_CREATE_WIN95;
			}
			break;
		case Opt_quiet:
			opts->quiet = 1;
			break;
		case Opt_showexec:
			opts->showexec = 1;
			break;
		case Opt_debug:
			*debug = 1;
			break;
		case Opt_immutable:
			opts->sys_immutable = 1;
			break;
		case Opt_uid:
			if (match_int(&args[0], &option))
				return 0;
			opts->fs_uid = option;
			break;
		case Opt_gid:
			if (match_int(&args[0], &option))
				return 0;
			opts->fs_gid = option;
			break;
		case Opt_umask:
			if (match_octal(&args[0], &option))
				return 0;
			opts->fs_fmask = opts->fs_dmask = option;
			break;
		case Opt_dmask:
			if (match_octal(&args[0], &option))
				return 0;
			opts->fs_dmask = option;
			break;
		case Opt_fmask:
			if (match_octal(&args[0], &option))