/* API structs */

struct pg_i {
        u64 last_swapout_t; /* last swapped-out */
        u16 access_bit_vec; /* accessed-bit vector */
        int owner_pid;      /* pid of the owner of the page */
        u64 cgroup_id;      /* cgroup_id of the owner of the page */
};

struct zn_i {
        int zone_id;        /* zone number */
        int capacity;       /* capacity (in slots) of the zone */
        int occupied_slots; /* number of occupied slots in the zone */
        int invalid_slots;  /* number of invalid (not used) slots in the zone */
        int swap_cache_slots; /* number of slots which have a swap-cache page in the zone */
        int swap_zone_id;     /* the last swap-zone slot number */
};

struct vm_i {
        u64 vm_flags;         /* the vm_flags of the first vma of the page */
        u64 size;             /* size of the vma */
        int readahead_win_sz; /* readahead window size of the vma */
        u64 cgroup_id;        /* cgroup_id of the vma */
};

struct swap_i {
        u64 num_slots;        /* total number of swap slots the device has */
        u64 num_zns;          /* total number of zones the device has */
        u64 free_slots;       /* number of free swap slots the device has */
        u64 free_zns;         /* number of free (Empty) zones the device has */
        u8 zslot_array_sz;    /* size of the swap-zone array */
        u32 high_wmark;       /* high wmark (configured via sysfs) */
        u32 low_wmark;        /* low wmark (configured via sysfs) */
        bool gc_running;      /* is vmGC currently running in the background */
};

/* Callbacks */

/* Call this function in the module init to register a callback
 * function which will get invoked when a new zone-slot needs
 * to be chosen. u64 is the victim page's pfn. swapolicy is needed
 * for some function calls within the callback function
 */
void register_policy(int(*pol)(u64, struct swappolicy*));

/* Trigger an async GC operation on zn`
extern void rec_zn(int zn);

/* Retrieve information on a page (pfn). Pass the sp element to the fuction 
 * recieved by the callback function */
extern void pg_inf(struct pg_i* pg, u64 pfn, struct swappolicy *sp);

/* Retrieve information on the page's vm_area_struct */
extern void vm_inf(struct vm_i* vm, u64 pfn, struct swappolicy *sp);

/* Retrieve information on a specific zone */
extern void zn_inf(struct zn_i* zn, int zone);

/* Retrieve information of the zoned swap device */
extern void swap_inf(struct swap_i* swap);

/* Register a callback function for the policy, which will be called
 * when a new swap-slot needs to be chosen for a victim page */
extern void register_policy(int(*pol)(u64, struct swappolicy*));