ext4 设备文件处理

if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
	      S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
	inode->i_op = &ext4_special_inode_operations;
	if (raw_inode->i_block[0])
		init_special_inode(inode, inode->i_mode,
		   old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
	else
		init_special_inode(inode, inode->i_mode,
		   new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
}

void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
{
	inode->i_mode = mode;
	if (S_ISCHR(mode)) {
		inode->i_fop = &def_chr_fops;
		inode->i_rdev = rdev;
	} else if (S_ISBLK(mode)) {
		inode->i_fop = &def_blk_fops;
		inode->i_rdev = rdev;
	} else if (S_ISFIFO(mode))
		inode->i_fop = &pipefifo_fops;
	else if (S_ISSOCK(mode))
		;	/* leave it no_open_fops */
	else
		printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"
				  " inode %s:%lu\n", mode, inode->i_sb->s_id,
				  inode->i_ino);
}
EXPORT_SYMBOL(init_special_inode);

const struct inode_operations ext4_special_inode_operations = {
	.setattr	= ext4_setattr,
	.listxattr	= ext4_listxattr,
	.get_acl	= ext4_get_acl,
	.set_acl	= ext4_set_acl,
};