// SPDX-License-Identifier: GPL-2.0

#include <linux/objpool.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/atomic.h>
#include <linux/irqflags.h>
#include <linux/cpumask.h>
#include <linux/log2.h>

/*
 * objpool: ring-array based lockless MPMC/FIFO queues
 *
 * Copyright: wuqiang.matt@bytedance.com,mhiramat@kernel.org
 */

/* initialize percpu objpool_slot */
static int
objpool_init_percpu_slot(struct objpool_head *pool,
                         struct objpool_slot *slot,
                         int nodes, void *context,
                         objpool_init_obj_cb objinit)
{
        void *obj = (void *)&slot->entries[pool->capacity];
        int i;

        /* initialize elements of percpu objpool_slot */
        slot->mask = pool->capacity - 1;

        for (i = 0; i < nodes; i++) {
                if (objinit) {
                        int rc = objinit(obj, context);
                        if (rc)
                                return rc;
                }
                slot->entries[slot->tail & slot->mask] = obj;
                obj = obj + pool->obj_size;
                slot->tail++;
                slot->last = slot->tail;
                pool->nr_objs++;
        }

        return 0;
}

/* allocate and initialize percpu slots */
static int
objpool_init_percpu_slots(struct objpool_head *pool, int nr_objs,
                          void *context, objpool_init_obj_cb objinit)
{
        int i, cpu_count = 0;

        for (i = 0; i < nr_cpu_ids; i++) {

                struct objpool_slot *slot;
                int nodes, size, rc;

                /* skip the cpu node which could never be present */
                if (!cpu_possible(i))
                        continue;

                /* compute how many objects to be allocated with this slot */
                nodes = nr_objs / pool->nr_possible_cpus;
                if (cpu_count < (nr_objs % pool->nr_possible_cpus))
                        nodes++;
                cpu_count++;

                size = struct_size(slot, entries, pool->capacity) +
                        pool->obj_size * nodes;

                /*
                 * here we allocate percpu-slot & objs together in a single
                 * allocation to make it more compact, taking advantage of
                 * warm caches and TLB hits. in default vmalloc is used to
                 * reduce the pressure of kernel slab system. as we know,
                 * mimimal size of vmalloc is one page since vmalloc would
                 * always align the requested size to page size.
                 * but if vmalloc fails or it is not available (e.g. GFP_ATOMIC)
                 * allocate percpu slot with kmalloc.
                 */
                slot = NULL;

                if ((pool->gfp & (GFP_ATOMIC | GFP_KERNEL)) != GFP_ATOMIC)
                        slot = __vmalloc_node(size, sizeof(void *), pool->gfp,
                                cpu_to_node(i), __builtin_return_address(0));

                if (!slot) {
                        slot = kmalloc_node(size, pool->gfp, cpu_to_node(i));
                        if (!slot)
                                return -ENOMEM;
                }
                memset(slot, 0, size);
                pool->cpu_slots[i] = slot;

                /* initialize the objpool_slot of cpu node i */
                rc = objpool_init_percpu_slot(pool, slot, nodes, context, objinit);
                if (rc)
                        return rc;
        }

        return 0;
}

/* cleanup all percpu slots of the object pool */
static void objpool_fini_percpu_slots(struct objpool_head *pool)
{
        int i;

        if (!pool->cpu_slots)
                return;

        for (i = 0; i < nr_cpu_ids; i++)
                kvfree(pool->cpu_slots[i]);
        kfree(pool->cpu_slots);
}

/* initialize object pool and pre-allocate objects */
int objpool_init(struct objpool_head *pool, int nr_objs, int object_size,
                gfp_t gfp, void *context, objpool_init_obj_cb objinit,
                objpool_fini_cb release)
{
        int rc, capacity, slot_size;

        /* check input parameters */
        if (nr_objs <= 0 || nr_objs > OBJPOOL_NR_OBJECT_MAX ||
            object_size <= 0 || object_size > OBJPOOL_OBJECT_SIZE_MAX)
                return -EINVAL;

        /* align up to unsigned long size */
        object_size = ALIGN(object_size, sizeof(long));

        /* calculate capacity of percpu objpool_slot */
        capacity = roundup_pow_of_two(nr_objs);
        if (!capacity)
                return -EINVAL;

        /* initialize objpool pool */
        memset(pool, 0, sizeof(struct objpool_head));
        pool->nr_possible_cpus = num_possible_cpus();
        pool->obj_size = object_size;
        pool->capacity = capacity;
        pool->gfp = gfp & ~__GFP_ZERO;
        pool->context = context;
        pool->release = release;
        slot_size = nr_cpu_ids * sizeof(struct objpool_slot *);
        pool->cpu_slots = kzalloc(slot_size, pool->gfp);
        if (!pool->cpu_slots)
                return -ENOMEM;

        /* initialize per-cpu slots */
        rc = objpool_init_percpu_slots(pool, nr_objs, context, objinit);
        if (rc)
                objpool_fini_percpu_slots(pool);
        else
                refcount_set(&pool->ref, pool->nr_objs + 1);

        return rc;
}
EXPORT_SYMBOL_GPL(objpool_init);

/* release whole objpool forcely */
void objpool_free(struct objpool_head *pool)
{
        if (!pool->cpu_slots)
                return;

        /* release percpu slots */
        objpool_fini_percpu_slots(pool);

        /* call user's cleanup callback if provided */
        if (pool->release)
                pool->release(pool, pool->context);
}
EXPORT_SYMBOL_GPL(objpool_free);

/* drop the allocated object, rather reclaim it to objpool */
int objpool_drop(void *obj, struct objpool_head *pool)
{
        if (!obj || !pool)
                return -EINVAL;

        if (refcount_dec_and_test(&pool->ref)) {
                objpool_free(pool);
                return 0;
        }

        return -EAGAIN;
}
EXPORT_SYMBOL_GPL(objpool_drop);

/* drop unused objects and defref objpool for releasing */
void objpool_fini(struct objpool_head *pool)
{
        int count = 1; /* extra ref for objpool itself */

        /* drop all remained objects from objpool */
        while (objpool_pop(pool))
                count++;

        if (refcount_sub_and_test(count, &pool->ref))
                objpool_free(pool);
}
EXPORT_SYMBOL_GPL(objpool_fini);