/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_LIST_BL_H
#define _LINUX_LIST_BL_H

#include <linux/list.h>
#include <linux/bit_spinlock.h>

/*
 * Special version of lists, where head of the list has a lock in the lowest
 * bit. This is useful for scalable hash tables without increasing memory
 * footprint overhead.
 *
 * For modification operations, the 0 bit of hlist_bl_head->first
 * pointer must be set.
 *
 * With some small modifications, this can easily be adapted to store several
 * arbitrary bits (not just a single lock bit), if the need arises to store
 * some fast and compact auxiliary data.
 */

#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
#define LIST_BL_LOCKMASK        1UL
#else
#define LIST_BL_LOCKMASK        0UL
#endif

#ifdef CONFIG_DEBUG_LIST
#define LIST_BL_BUG_ON(x) BUG_ON(x)
#else
#define LIST_BL_BUG_ON(x)
#endif


struct hlist_bl_head {
        struct hlist_bl_node *first;
};

struct hlist_bl_node {
        struct hlist_bl_node *next, **pprev;
};
#define INIT_HLIST_BL_HEAD(ptr) \
        ((ptr)->first = NULL)

static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h)
{
        h->next = NULL;
        h->pprev = NULL;
}

#define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member)

static inline bool  hlist_bl_unhashed(const struct hlist_bl_node *h)
{
        return !h->pprev;
}

static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h)
{
        return (struct hlist_bl_node *)
                ((unsigned long)h->first & ~LIST_BL_LOCKMASK);
}

static inline void hlist_bl_set_first(struct hlist_bl_head *h,
                                        struct hlist_bl_node *n)
{
        LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
        LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
                                                        LIST_BL_LOCKMASK);
        h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
}

static inline bool hlist_bl_empty(const struct hlist_bl_head *h)
{
        return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK);
}

static inline void hlist_bl_add_head(struct hlist_bl_node *n,
                                        struct hlist_bl_head *h)
{
        struct hlist_bl_node *first = hlist_bl_first(h);

        n->next = first;
        if (first)
                first->pprev = &n->next;
        n->pprev = &h->first;
        hlist_bl_set_first(h, n);
}

static inline void hlist_bl_add_before(struct hlist_bl_node *n,
                                       struct hlist_bl_node *next)
{
        struct hlist_bl_node **pprev = next->pprev;

        n->pprev = pprev;
        n->next = next;
        next->pprev = &n->next;

        /* pprev may be `first`, so be careful not to lose the lock bit */
        WRITE_ONCE(*pprev,
                   (struct hlist_bl_node *)
                        ((uintptr_t)n | ((uintptr_t)*pprev & LIST_BL_LOCKMASK)));
}

static inline void hlist_bl_add_behind(struct hlist_bl_node *n,
                                       struct hlist_bl_node *prev)
{
        n->next = prev->next;
        n->pprev = &prev->next;
        prev->next = n;

        if (n->next)
                n->next->pprev = &n->next;
}

static inline void __hlist_bl_del(struct hlist_bl_node *n)
{
        struct hlist_bl_node *next = n->next;
        struct hlist_bl_node **pprev = n->pprev;

        LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);

        /* pprev may be `first`, so be careful not to lose the lock bit */
        WRITE_ONCE(*pprev,
                   (struct hlist_bl_node *)
                        ((unsigned long)next |
                         ((unsigned long)*pprev & LIST_BL_LOCKMASK)));
        if (next)
                next->pprev = pprev;
}

static inline void hlist_bl_del(struct hlist_bl_node *n)
{
        __hlist_bl_del(n);
        n->next = LIST_POISON1;
        n->pprev = LIST_POISON2;
}

static inline void hlist_bl_del_init(struct hlist_bl_node *n)
{
        if (!hlist_bl_unhashed(n)) {
                __hlist_bl_del(n);
                INIT_HLIST_BL_NODE(n);
        }
}

static inline void hlist_bl_lock(struct hlist_bl_head *b)
{
        bit_spin_lock(0, (unsigned long *)b);
}

static inline void hlist_bl_unlock(struct hlist_bl_head *b)
{
        __bit_spin_unlock(0, (unsigned long *)b);
}

static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
{
        return bit_spin_is_locked(0, (unsigned long *)b);
}

/**
 * hlist_bl_for_each_entry      - iterate over list of given type
 * @tpos:       the type * to use as a loop cursor.
 * @pos:        the &struct hlist_node to use as a loop cursor.
 * @head:       the head for your list.
 * @member:     the name of the hlist_node within the struct.
 *
 */
#define hlist_bl_for_each_entry(tpos, pos, head, member)                \
        for (pos = hlist_bl_first(head);                                \
             pos &&                                                     \
                ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
             pos = pos->next)

/**
 * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @tpos:       the type * to use as a loop cursor.
 * @pos:        the &struct hlist_node to use as a loop cursor.
 * @n:          another &struct hlist_node to use as temporary storage
 * @head:       the head for your list.
 * @member:     the name of the hlist_node within the struct.
 */
#define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member)         \
        for (pos = hlist_bl_first(head);                                 \
             pos && ({ n = pos->next; 1; }) &&                           \
                ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
             pos = n)

#endif