mount出错，请教各位前辈

fyfzh

小弟用fist工具开发了一个堆叠式的加密文件系统，但在mount的时候不成功，然后dmesg显示，“kcfs_read_super: missing data argument”错误，kcfs为文件系统模块名：找该函数的代码如下：
kcfs_read_super(super_block_t *sb, void *raw_data, int silent)
{
        struct dentry *lower_root = NULL;
        struct vfsmount *lower_mount = NULL;
        int err = 0;

        print_entry_location();

#ifdef FIST_MALLOC_DEBUG
        atomic_set(&kcfs_malloc_counter, 0); /* for malloc debugging */
#endif /* FIST_MALLOC_DEBUG */

        if (!raw_data) {
                printk(KERN_WARNING "kcfs_read_super: missing data argument\n");
                err = -EINVAL;
                goto out_no_raw;
        }
        /*
         * Allocate superblock private data
         */
        SUPERBLOCK_TO_PRIVATE_SM(sb) = KMALLOC(sizeof(struct kcfs_sb_info), GFP_KERNEL);
        if (!SUPERBLOCK_TO_PRIVATE(sb)) {
                printk(KERN_WARNING "%s: out of memory\n", __FUNCTION__);
                err = -ENOMEM;
                goto out;
        }
        memset(SUPERBLOCK_TO_PRIVATE(sb), 0, sizeof(struct kcfs_sb_info));


        if ((err = kcfs_parse_options(sb, raw_data, &lower_root, &lower_mount))) {
                goto out_free;
        }
        if (IS_ERR(lower_root)) {
                printk(KERN_WARNING "kcfs_read_super: lookup_dentry failed (err = %ld)\n", PTR_ERR(lower_root));
                err = PTR_ERR(lower_root);
                goto out_free;
        }
        if (!lower_root->d_inode) {
                printk(KERN_WARNING "kcfs_read_super: no directory to interpose on\n");
                goto out_dput;
        }
        SUPERBLOCK_TO_LOWER(sb) = lower_root->d_sb;

        sb->s_maxbytes = lower_root->d_sb->s_maxbytes;

        sb->s_op = &kcfs_sops;
        /*
         * we can't use d_alloc_root if we want to use
         * our own interpose function unchanged,
         * so we simply replicate *most* of the code in d_alloc_root here
         */

        sb->s_root = d_alloc(NULL, &(const struct qstr){hash: 0, name: "/", len: 1});
        if (IS_ERR(sb->s_root)) {
                printk(KERN_WARNING "kcfs_read_super: d_alloc failed\n");
                err = -ENOMEM;
                goto out_dput;
        }

        sb->s_root->d_op = &kcfs_dops;
        sb->s_root->d_sb = sb;
        sb->s_root->d_parent = sb->s_root;
        /* link the upper and lower dentries */
        DENTRY_TO_PRIVATE_SM(sb->s_root) = (struct kcfs_dentry_info *) KMALLOC(sizeof(struct kcfs_dentry_info), GFP_KERNEL);

        if (!DENTRY_TO_PRIVATE(sb->s_root)) {
                err = -ENOMEM;
                goto out_dput2;
        }
        DENTRY_TO_LOWER(sb->s_root) = lower_root;
        DENTRY_TO_LVFSMNT(sb->s_root) = lower_mount;


        if ((err = kcfs_interpose(lower_root, sb->s_root, sb, 0)) != 0)
                goto out_dput2;

        fist_print_dentry("kcfs_read_super OUT lower_dentry", lower_root);
        fist_print_inode("kcfs_read_super OUT lower_inode", lower_root->d_inode);
        // next line causes null ptr deref at mount(2) time
        // fist_print_dentry("%s OUT sb->s_root", __FUNCTION__, sb->s_root);
        goto out;

out_dput2:
        dput(sb->s_root);
out_dput:
        dput(lower_root);
out_free:
        // XXX: HL: is that mntput necessary? There is some relation to the path_walk in parse_options -
        //  there the path_release is "missing"
        mntput(lower_mount);
        KFREE(SUPERBLOCK_TO_PRIVATE(sb));
        SUPERBLOCK_TO_PRIVATE_SM(sb) = NULL;
out:
        fist_print_sb("OUT sb", sb);
        if (SUPERBLOCK_TO_PRIVATE(sb))
                fist_print_sb("OUT lower_sb", SUPERBLOCK_TO_LOWER(sb));
out_no_raw:
        print_exit_location();
        return err;
}
请各位前辈帮帮忙，怎么解决？