// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2016 Facebook
 */
#include "percpu_freelist.h"

int pcpu_freelist_init(struct pcpu_freelist *s)
{
        int cpu;

        s->freelist = alloc_percpu(struct pcpu_freelist_head);
        if (!s->freelist)
                return -ENOMEM;

        for_each_possible_cpu(cpu) {
                struct pcpu_freelist_head *head = per_cpu_ptr(s->freelist, cpu);

                raw_res_spin_lock_init(&head->lock);
                head->first = NULL;
        }
        return 0;
}

void pcpu_freelist_destroy(struct pcpu_freelist *s)
{
        free_percpu(s->freelist);
}

static inline void pcpu_freelist_push_node(struct pcpu_freelist_head *head,
                                           struct pcpu_freelist_node *node)
{
        node->next = head->first;
        WRITE_ONCE(head->first, node);
}

static inline bool ___pcpu_freelist_push(struct pcpu_freelist_head *head,
                                         struct pcpu_freelist_node *node)
{
        if (raw_res_spin_lock(&head->lock))
                return false;
        pcpu_freelist_push_node(head, node);
        raw_res_spin_unlock(&head->lock);
        return true;
}

void __pcpu_freelist_push(struct pcpu_freelist *s,
                        struct pcpu_freelist_node *node)
{
        struct pcpu_freelist_head *head;
        int cpu;

        if (___pcpu_freelist_push(this_cpu_ptr(s->freelist), node))
                return;

        while (true) {
                for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) {
                        if (cpu == raw_smp_processor_id())
                                continue;
                        head = per_cpu_ptr(s->freelist, cpu);
                        if (raw_res_spin_lock(&head->lock))
                                continue;
                        pcpu_freelist_push_node(head, node);
                        raw_res_spin_unlock(&head->lock);
                        return;
                }
        }
}

void pcpu_freelist_push(struct pcpu_freelist *s,
                        struct pcpu_freelist_node *node)
{
        unsigned long flags;

        local_irq_save(flags);
        __pcpu_freelist_push(s, node);
        local_irq_restore(flags);
}

void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size,
                            u32 nr_elems)
{
        struct pcpu_freelist_head *head;
        unsigned int cpu, cpu_idx, i, j, n, m;

        n = nr_elems / num_possible_cpus();
        m = nr_elems % num_possible_cpus();

        cpu_idx = 0;
        for_each_possible_cpu(cpu) {
                head = per_cpu_ptr(s->freelist, cpu);
                j = n + (cpu_idx < m ? 1 : 0);
                for (i = 0; i < j; i++) {
                        /* No locking required as this is not visible yet. */
                        pcpu_freelist_push_node(head, buf);
                        buf += elem_size;
                }
                cpu_idx++;
        }
}

static struct pcpu_freelist_node *___pcpu_freelist_pop(struct pcpu_freelist *s)
{
        struct pcpu_freelist_node *node = NULL;
        struct pcpu_freelist_head *head;
        int cpu;

        for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) {
                head = per_cpu_ptr(s->freelist, cpu);
                if (!READ_ONCE(head->first))
                        continue;
                if (raw_res_spin_lock(&head->lock))
                        continue;
                node = head->first;
                if (node) {
                        WRITE_ONCE(head->first, node->next);
                        raw_res_spin_unlock(&head->lock);
                        return node;
                }
                raw_res_spin_unlock(&head->lock);
        }
        return node;
}

struct pcpu_freelist_node *__pcpu_freelist_pop(struct pcpu_freelist *s)
{
        return ___pcpu_freelist_pop(s);
}

struct pcpu_freelist_node *pcpu_freelist_pop(struct pcpu_freelist *s)
{
        struct pcpu_freelist_node *ret;
        unsigned long flags;

        local_irq_save(flags);
        ret = __pcpu_freelist_pop(s);
        local_irq_restore(flags);
        return ret;
}