hlist_node v/s list_head

[Onkar Mahajan <kern.devel@xxxxxxxxx>]

hi All,

struct hlist_head {
    struct hlist_node *first;
};

struct hlist_node {
    struct hlist_node *next, **pprev;<--------------------------------
};

Why there is a double pointer here  ??


struct list_head {
    struct list_head *next, *prev;
};


Regards,
Onkar