dir.c

讲述linux的初始化过程

		unsigned char sum;
		unsigned char alias_checksum;

		if (!unicode) {
			unicode = (unsigned char *)
				__get_free_page(GFP_KERNEL);
			if (!unicode) {
				filp->f_pos = cpos;
				fat_brelse(sb, bh);
				return -ENOMEM;
			}
		}
ParseLong:
		slots = 0;
		offset = 0;
		ds = (struct msdos_dir_slot *) de;
		id = ds->id;
		if (!(id & 0x40))
			goto RecEnd;
		slots = id & ~0x40;
		if (slots > 20 || !slots)	/* ceil(256 * 2 / 26) */
			goto RecEnd;
		long_slots = slots;
		alias_checksum = ds->alias_checksum;

		slot = slots;
		while (1) {
			slot--;
			offset = slot * 26;
			memcpy(&unicode[offset], ds->name0_4, 10);
			memcpy(&unicode[offset+10], ds->name5_10, 12);
			memcpy(&unicode[offset+22], ds->name11_12, 4);
			offset += 26;

			if (ds->id & 0x40) {
				unicode[offset] = 0;
				unicode[offset+1] = 0;
			}
			if (fat_get_entry(inode,&cpos,&bh,&de,&ino) == -1)
				goto EODir;
			if (slot == 0)
				break;
			ds = (struct msdos_dir_slot *) de;
			if (ds->attr !=  ATTR_EXT)
				goto RecEnd;	/* XXX */
			if ((ds->id & ~0x40) != slot)
				goto ParseLong;
			if (ds->alias_checksum != alias_checksum)
				goto ParseLong;
		}
		if (de->name[0] == (__s8) DELETED_FLAG)
			goto RecEnd;
		if (de->attr ==  ATTR_EXT)
			goto ParseLong;
		if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME))
			goto RecEnd;
		for (sum = 0, i = 0; i < 11; i++)
			sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i];
		if (sum != alias_checksum)
			long_slots = 0;
	}

	if ((de->attr & ATTR_HIDDEN) && MSDOS_SB(sb)->options.dotsOK) {
		fat_short2lower_uni(nls_disk, '.', ptuname);
		*ptname++ = '.';
		dotoffset = 1;
	}
	for (i = 0, last = 0; i < 8;) {
		if (!(c = de->name[i])) break;
		/* see namei.c, msdos_format_name */
		if (c == 0x05) c = 0xE5;
		fat_short2lower_uni(nls_disk, c, &ptuname[i]);
		ptname[i++] = (!nocase && c>='A' && c<='Z') ? c+32 : c;
		if (c != ' ')
			last = i;
	}
	i = last;
	fat_short2lower_uni(nls_disk, '.', &ptuname[i]);
	ptname[i++] = '.';
	for (i2 = 0; i2 < 3; i2++) {
		if (!(c = de->ext[i2])) break;
		fat_short2lower_uni(nls_disk, c, &ptuname[i]);
		ptname[i++] = (!nocase && c>='A' && c<='Z') ? c+32 : c;
		if (c != ' ')
			last = i;
	}
	if (!last)
		goto RecEnd;

	i = last + dotoffset;

	lpos = cpos - (long_slots+1)*sizeof(struct msdos_dir_entry);
	if (!memcmp(de->name,MSDOS_DOT,11))
		inum = inode->i_ino;
	else if (!memcmp(de->name,MSDOS_DOTDOT,11)) {
/*		inum = fat_parent_ino(inode,0); */
		inum = filp->f_dentry->d_parent->d_inode->i_ino;
	} else {
		struct inode *tmp = fat_iget(sb, ino);
		if (tmp) {
			inum = tmp->i_ino;
			iput(tmp);
		} else
			inum = iunique(sb, MSDOS_ROOT_INO);
	}

	if (isvfat) {
		memset(&bufuname[i], 0, sizeof(wchar_t));
		i = utf8 ? utf8_wcstombs(bufname, bufuname, 56)
			 : uni16_to_x8(bufname, bufuname, uni_xlate, nls_io);
	}

	if (!long_slots||shortnames) {
		if (both)
			bufname[i] = '\0';
		if (filldir(dirent, bufname, i, *furrfu, inum,
			    (de->attr & ATTR_DIR) ? DT_DIR : DT_REG) < 0)
			goto FillFailed;
	} else {
		char longname[275];
		unsigned char long_len = utf8
			? utf8_wcstombs(longname, (wchar_t *) unicode, 275)
			: uni16_to_x8(longname, (wchar_t *) unicode, uni_xlate,
				      nls_io);
		if (both) {
			memcpy(&longname[long_len+1], bufname, i);
			long_len += i;
		}
		if (filldir(dirent, longname, long_len, *furrfu, inum,
			    (de->attr & ATTR_DIR) ? DT_DIR : DT_REG) < 0)
			goto FillFailed;
	}

RecEnd:
	furrfu = &lpos;
	filp->f_pos = cpos;
	goto GetNew;
EODir:
	filp->f_pos = cpos;
FillFailed:
	if (bh)
		fat_brelse(sb, bh);
	if (unicode) {
		free_page((unsigned long) unicode);
	}
	return 0;
}

int fat_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
	struct inode *inode = filp->f_dentry->d_inode;
	return fat_readdirx(inode, filp, dirent, filldir, 0, 0);
}

static int vfat_ioctl_fill(
	void * buf,
	const char * name,
	int name_len,
	off_t offset,
	ino_t ino,
	unsigned int d_type)
{
	struct dirent *d1 = (struct dirent *)buf;
	struct dirent *d2 = d1 + 1;
	int len, slen;
	int dotdir;

	get_user(len, &d1->d_reclen);
	if (len != 0) {
		return -1;
	}

	if ((name_len == 1 && name[0] == '.') ||
	    (name_len == 2 && name[0] == '.' && name[1] == '.')) {
		dotdir = 1;
		len = name_len;
	} else {
		dotdir = 0;
		len = strlen(name);
	}
	if (len != name_len) {
		copy_to_user(d2->d_name, name, len);
		put_user(0, d2->d_name + len);
		put_user(len, &d2->d_reclen);
		put_user(ino, &d2->d_ino);
		put_user(offset, &d2->d_off);
		slen = name_len - len;
		copy_to_user(d1->d_name, name+len+1, slen);
		put_user(0, d1->d_name+slen);
		put_user(slen, &d1->d_reclen);
	} else {
		put_user(0, d2->d_name);
		put_user(0, &d2->d_reclen);
		copy_to_user(d1->d_name, name, len);
		put_user(0, d1->d_name+len);
		put_user(len, &d1->d_reclen);
	}
	PRINTK(("FAT d1=%p d2=%p len=%d, name_len=%d\n",
		d1, d2, len, name_len));

	return 0;
}

int fat_dir_ioctl(struct inode * inode, struct file * filp,
		  unsigned int cmd, unsigned long arg)
{
	int err;
	/*
	 * We want to provide an interface for Samba to be able
	 * to get the short filename for a given long filename.
	 * Samba should use this ioctl instead of readdir() to
	 * get the information it needs.
	 */
	switch (cmd) {
	case VFAT_IOCTL_READDIR_BOTH: {
		struct dirent *d1 = (struct dirent *)arg;
		err = verify_area(VERIFY_WRITE, d1, sizeof(struct dirent[2]));
		if (err)
			return err;
		put_user(0, &d1->d_reclen);
		return fat_readdirx(inode,filp,(void *)arg,
				    vfat_ioctl_fill, 0, 1);
	}
	case VFAT_IOCTL_READDIR_SHORT: {
		struct dirent *d1 = (struct dirent *)arg;
		put_user(0, &d1->d_reclen);
		err = verify_area(VERIFY_WRITE, d1, sizeof(struct dirent[2]));
		if (err)
			return err;
		return fat_readdirx(inode,filp,(void *)arg,
				    vfat_ioctl_fill, 1, 1);
	}
	default:
		/* forward ioctl to CVF extension */
	       if (MSDOS_SB(inode->i_sb)->cvf_format &&
		   MSDOS_SB(inode->i_sb)->cvf_format->cvf_dir_ioctl)
		       return MSDOS_SB(inode->i_sb)->cvf_format
			       ->cvf_dir_ioctl(inode,filp,cmd,arg);
		return -EINVAL;
	}

	return 0;
}

/***** See if directory is empty */
int fat_dir_empty(struct inode *dir)
{
	loff_t pos;
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	int ino,result = 0;

	pos = 0;
	bh = NULL;
	while (fat_get_entry(dir,&pos,&bh,&de,&ino) > -1) {
		/* Ignore vfat longname entries */
		if (de->attr == ATTR_EXT)
			continue;
		if (!IS_FREE(de->name) && 
		    strncmp(de->name,MSDOS_DOT   , MSDOS_NAME) &&
		    strncmp(de->name,MSDOS_DOTDOT, MSDOS_NAME)) {
			result = -ENOTEMPTY;
			break;
		}
	}
	if (bh)
		fat_brelse(dir->i_sb, bh);

	return result;
}

/* This assumes that size of cluster is above the 32*slots */

int fat_add_entries(struct inode *dir,int slots, struct buffer_head **bh,
		  struct msdos_dir_entry **de, int *ino)
{
	struct super_block *sb = dir->i_sb;
	loff_t offset, curr;
	int row;
	struct buffer_head *new_bh;

	offset = curr = 0;
	*bh = NULL;
	row = 0;
	while (fat_get_entry(dir,&curr,bh,de,ino) > -1) {
		if (IS_FREE((*de)->name)) {
			if (++row == slots)
				return offset;
		} else {
			row = 0;
			offset = curr;
		}
	}
	if ((dir->i_ino == MSDOS_ROOT_INO) && (MSDOS_SB(sb)->fat_bits != 32)) 
		return -ENOSPC;
	new_bh = fat_extend_dir(dir);
	if (!new_bh)
		return -ENOSPC;
	fat_brelse(sb, new_bh);
	do fat_get_entry(dir,&curr,bh,de,ino); while (++row<slots);
	return offset;
}

int fat_new_dir(struct inode *dir, struct inode *parent, int is_vfat)
{
	struct super_block *sb = dir->i_sb;
	struct buffer_head *bh;
	struct msdos_dir_entry *de;
	__u16 date, time;

	if ((bh = fat_extend_dir(dir)) == NULL) return -ENOSPC;
	/* zeroed out, so... */
	fat_date_unix2dos(dir->i_mtime,&time,&date);
	de = (struct msdos_dir_entry*)&bh->b_data[0];
	memcpy(de[0].name,MSDOS_DOT,MSDOS_NAME);
	memcpy(de[1].name,MSDOS_DOTDOT,MSDOS_NAME);
	de[0].attr = de[1].attr = ATTR_DIR;
	de[0].time = de[1].time = CT_LE_W(time);
	de[0].date = de[1].date = CT_LE_W(date);
	if (is_vfat) {	/* extra timestamps */
		de[0].ctime = de[1].ctime = CT_LE_W(time);
		de[0].adate = de[0].cdate =
			de[1].adate = de[1].cdate = CT_LE_W(date);
	}
	de[0].start = CT_LE_W(MSDOS_I(dir)->i_logstart);
	de[0].starthi = CT_LE_W(MSDOS_I(dir)->i_logstart>>16);
	de[1].start = CT_LE_W(MSDOS_I(parent)->i_logstart);
	de[1].starthi = CT_LE_W(MSDOS_I(parent)->i_logstart>>16);
	fat_mark_buffer_dirty(sb, bh);
	fat_brelse(sb, bh);
	dir->i_atime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
	mark_inode_dirty(dir);

	return 0;
}

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-indent-level: 8
 * c-brace-imaginary-offset: 0
 * c-brace-offset: -8
 * c-argdecl-indent: 8
 * c-label-offset: -8
 * c-continued-statement-offset: 8
 * c-continued-brace-offset: 0
 * End:
 */