// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
 * Authors: David Chinner and Glauber Costa
 *
 * Generic LRU infrastructure
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/list_lru.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/memcontrol.h>
#include "slab.h"

#ifdef CONFIG_MEMCG_KMEM
static LIST_HEAD(list_lrus);
static DEFINE_MUTEX(list_lrus_mutex);

static void list_lru_register(struct list_lru *lru)
{
        mutex_lock(&list_lrus_mutex);
        list_add(&lru->list, &list_lrus);
        mutex_unlock(&list_lrus_mutex);
}

static void list_lru_unregister(struct list_lru *lru)
{
        mutex_lock(&list_lrus_mutex);
        list_del(&lru->list);
        mutex_unlock(&list_lrus_mutex);
}

static int lru_shrinker_id(struct list_lru *lru)
{
        return lru->shrinker_id;
}

static inline bool list_lru_memcg_aware(struct list_lru *lru)
{
        return lru->memcg_aware;
}

static inline struct list_lru_one *
list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
{
        struct list_lru_memcg *memcg_lrus;
        /*
         * Either lock or RCU protects the array of per cgroup lists
         * from relocation (see memcg_update_list_lru_node).
         */
        memcg_lrus = rcu_dereference_check(nlru->memcg_lrus,
                                           lockdep_is_held(&nlru->lock));
        if (memcg_lrus && idx >= 0)
                return memcg_lrus->lru[idx];
        return &nlru->lru;
}

static inline struct list_lru_one *
list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
                   struct mem_cgroup **memcg_ptr)
{
        struct list_lru_one *l = &nlru->lru;
        struct mem_cgroup *memcg = NULL;

        if (!nlru->memcg_lrus)
                goto out;

        memcg = mem_cgroup_from_obj(ptr);
        if (!memcg)
                goto out;

        l = list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg));
out:
        if (memcg_ptr)
                *memcg_ptr = memcg;
        return l;
}
#else
static void list_lru_register(struct list_lru *lru)
{
}

static void list_lru_unregister(struct list_lru *lru)
{
}

static int lru_shrinker_id(struct list_lru *lru)
{
        return -1;
}

static inline bool list_lru_memcg_aware(struct list_lru *lru)
{
        return false;
}

static inline struct list_lru_one *
list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
{
        return &nlru->lru;
}

static inline struct list_lru_one *
list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
                   struct mem_cgroup **memcg_ptr)
{
        if (memcg_ptr)
                *memcg_ptr = NULL;
        return &nlru->lru;
}
#endif /* CONFIG_MEMCG_KMEM */

bool list_lru_add(struct list_lru *lru, struct list_head *item)
{
        int nid = page_to_nid(virt_to_page(item));
        struct list_lru_node *nlru = &lru->node[nid];
        struct mem_cgroup *memcg;
        struct list_lru_one *l;

        spin_lock(&nlru->lock);
        if (list_empty(item)) {
                l = list_lru_from_kmem(nlru, item, &memcg);
                list_add_tail(item, &l->list);
                /* Set shrinker bit if the first element was added */
                if (!l->nr_items++)
                        set_shrinker_bit(memcg, nid,
                                         lru_shrinker_id(lru));
                nlru->nr_items++;
                spin_unlock(&nlru->lock);
                return true;
        }
        spin_unlock(&nlru->lock);
        return false;
}
EXPORT_SYMBOL_GPL(list_lru_add);

bool list_lru_del(struct list_lru *lru, struct list_head *item)
{
        int nid = page_to_nid(virt_to_page(item));
        struct list_lru_node *nlru = &lru->node[nid];
        struct list_lru_one *l;

        spin_lock(&nlru->lock);
        if (!list_empty(item)) {
                l = list_lru_from_kmem(nlru, item, NULL);
                list_del_init(item);
                l->nr_items--;
                nlru->nr_items--;
                spin_unlock(&nlru->lock);
                return true;
        }
        spin_unlock(&nlru->lock);
        return false;
}
EXPORT_SYMBOL_GPL(list_lru_del);

void list_lru_isolate(struct list_lru_one *list, struct list_head *item)
{
        list_del_init(item);
        list->nr_items--;
}
EXPORT_SYMBOL_GPL(list_lru_isolate);

void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
                           struct list_head *head)
{
        list_move(item, head);
        list->nr_items--;
}
EXPORT_SYMBOL_GPL(list_lru_isolate_move);

unsigned long list_lru_count_one(struct list_lru *lru,
                                 int nid, struct mem_cgroup *memcg)
{
        struct list_lru_node *nlru = &lru->node[nid];
        struct list_lru_one *l;
        unsigned long count;

        rcu_read_lock();
        l = list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg));
        count = READ_ONCE(l->nr_items);
        rcu_read_unlock();

        return count;
}
EXPORT_SYMBOL_GPL(list_lru_count_one);

unsigned long list_lru_count_node(struct list_lru *lru, int nid)
{
        struct list_lru_node *nlru;

        nlru = &lru->node[nid];
        return nlru->nr_items;
}
EXPORT_SYMBOL_GPL(list_lru_count_node);

static unsigned long
__list_lru_walk_one(struct list_lru_node *nlru, int memcg_idx,
                    list_lru_walk_cb isolate, void *cb_arg,
                    unsigned long *nr_to_walk)
{

        struct list_lru_one *l;
        struct list_head *item, *n;
        unsigned long isolated = 0;

        l = list_lru_from_memcg_idx(nlru, memcg_idx);
restart:
        list_for_each_safe(item, n, &l->list) {
                enum lru_status ret;

                /*
                 * decrement nr_to_walk first so that we don't livelock if we
                 * get stuck on large numbers of LRU_RETRY items
                 */
                if (!*nr_to_walk)
                        break;
                --*nr_to_walk;

                ret = isolate(item, l, &nlru->lock, cb_arg);
                switch (ret) {
                case LRU_REMOVED_RETRY:
                        assert_spin_locked(&nlru->lock);
                        fallthrough;
                case LRU_REMOVED:
                        isolated++;
                        nlru->nr_items--;
                        /*
                         * If the lru lock has been dropped, our list
                         * traversal is now invalid and so we have to
                         * restart from scratch.
                         */
                        if (ret == LRU_REMOVED_RETRY)
                                goto restart;
                        break;
                case LRU_ROTATE:
                        list_move_tail(item, &l->list);
                        break;
                case LRU_SKIP:
                        break;
                case LRU_RETRY:
                        /*
                         * The lru lock has been dropped, our list traversal is
                         * now invalid and so we have to restart from scratch.
                         */
                        assert_spin_locked(&nlru->lock);
                        goto restart;
                default:
                        BUG();
                }
        }
        return isolated;
}

unsigned long
list_lru_walk_one(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
                  list_lru_walk_cb isolate, void *cb_arg,
                  unsigned long *nr_to_walk)
{
        struct list_lru_node *nlru = &lru->node[nid];
        unsigned long ret;

        spin_lock(&nlru->lock);
        ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
                                  nr_to_walk);
        spin_unlock(&nlru->lock);
        return ret;
}
EXPORT_SYMBOL_GPL(list_lru_walk_one);

unsigned long
list_lru_walk_one_irq(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
                      list_lru_walk_cb isolate, void *cb_arg,
                      unsigned long *nr_to_walk)
{
        struct list_lru_node *nlru = &lru->node[nid];
        unsigned long ret;

        spin_lock_irq(&nlru->lock);
        ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
                                  nr_to_walk);
        spin_unlock_irq(&nlru->lock);
        return ret;
}

unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
                                 list_lru_walk_cb isolate, void *cb_arg,
                                 unsigned long *nr_to_walk)
{
        long isolated = 0;
        int memcg_idx;

        isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
                                      nr_to_walk);
        if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
                for_each_memcg_cache_index(memcg_idx) {
                        struct list_lru_node *nlru = &lru->node[nid];

                        spin_lock(&nlru->lock);
                        isolated += __list_lru_walk_one(nlru, memcg_idx,
                                                        isolate, cb_arg,
                                                        nr_to_walk);
                        spin_unlock(&nlru->lock);

                        if (*nr_to_walk <= 0)
                                break;
                }
        }
        return isolated;
}
EXPORT_SYMBOL_GPL(list_lru_walk_node);

static void init_one_lru(struct list_lru_one *l)
{
        INIT_LIST_HEAD(&l->list);
        l->nr_items = 0;
}

#ifdef CONFIG_MEMCG_KMEM
static void __memcg_destroy_list_lru_node(struct list_lru_memcg *memcg_lrus,
                                          int begin, int end)
{
        int i;

        for (i = begin; i < end; i++)
                kfree(memcg_lrus->lru[i]);
}

static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
                                      int begin, int end)
{
        int i;

        for (i = begin; i < end; i++) {
                struct list_lru_one *l;

                l = kmalloc(sizeof(struct list_lru_one), GFP_KERNEL);
                if (!l)
                        goto fail;

                init_one_lru(l);
                memcg_lrus->lru[i] = l;
        }
        return 0;
fail:
        __memcg_destroy_list_lru_node(memcg_lrus, begin, i);
        return -ENOMEM;
}

static int memcg_init_list_lru_node(struct list_lru_node *nlru)
{
        struct list_lru_memcg *memcg_lrus;
        int size = memcg_nr_cache_ids;

        memcg_lrus = kvmalloc(sizeof(*memcg_lrus) +
                              size * sizeof(void *), GFP_KERNEL);
        if (!memcg_lrus)
                return -ENOMEM;

        if (__memcg_init_list_lru_node(memcg_lrus, 0, size)) {
                kvfree(memcg_lrus);
                return -ENOMEM;
        }
        RCU_INIT_POINTER(nlru->memcg_lrus, memcg_lrus);

        return 0;
}

static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
{
        struct list_lru_memcg *memcg_lrus;
        /*
         * This is called when shrinker has already been unregistered,
         * and nobody can use it. So, there is no need to use kvfree_rcu().
         */
        memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
        __memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
        kvfree(memcg_lrus);
}

static int memcg_update_list_lru_node(struct list_lru_node *nlru,
                                      int old_size, int new_size)
{
        struct list_lru_memcg *old, *new;

        BUG_ON(old_size > new_size);

        old = rcu_dereference_protected(nlru->memcg_lrus,
                                        lockdep_is_held(&list_lrus_mutex));
        new = kvmalloc(sizeof(*new) + new_size * sizeof(void *), GFP_KERNEL);
        if (!new)
                return -ENOMEM;

        if (__memcg_init_list_lru_node(new, old_size, new_size)) {
                kvfree(new);
                return -ENOMEM;
        }

        memcpy(&new->lru, &old->lru, old_size * sizeof(void *));

        /*
         * The locking below allows readers that hold nlru->lock avoid taking
         * rcu_read_lock (see list_lru_from_memcg_idx).
         *
         * Since list_lru_{add,del} may be called under an IRQ-safe lock,
         * we have to use IRQ-safe primitives here to avoid deadlock.
         */
        spin_lock_irq(&nlru->lock);
        rcu_assign_pointer(nlru->memcg_lrus, new);
        spin_unlock_irq(&nlru->lock);

        kvfree_rcu(old, rcu);
        return 0;
}

static void memcg_cancel_update_list_lru_node(struct list_lru_node *nlru,
                                              int old_size, int new_size)
{
        struct list_lru_memcg *memcg_lrus;

        memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus,
                                               lockdep_is_held(&list_lrus_mutex));
        /* do not bother shrinking the array back to the old size, because we
         * cannot handle allocation failures here */
        __memcg_destroy_list_lru_node(memcg_lrus, old_size, new_size);
}

static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
{
        int i;

        lru->memcg_aware = memcg_aware;

        if (!memcg_aware)
                return 0;

        for_each_node(i) {
                if (memcg_init_list_lru_node(&lru->node[i]))
                        goto fail;
        }
        return 0;
fail:
        for (i = i - 1; i >= 0; i--) {
                if (!lru->node[i].memcg_lrus)
                        continue;
                memcg_destroy_list_lru_node(&lru->node[i]);
        }
        return -ENOMEM;
}

static void memcg_destroy_list_lru(struct list_lru *lru)
{
        int i;

        if (!list_lru_memcg_aware(lru))
                return;

        for_each_node(i)
                memcg_destroy_list_lru_node(&lru->node[i]);
}

static int memcg_update_list_lru(struct list_lru *lru,
                                 int old_size, int new_size)
{
        int i;

        if (!list_lru_memcg_aware(lru))
                return 0;

        for_each_node(i) {
                if (memcg_update_list_lru_node(&lru->node[i],
                                               old_size, new_size))
                        goto fail;
        }
        return 0;
fail:
        for (i = i - 1; i >= 0; i--) {
                if (!lru->node[i].memcg_lrus)
                        continue;

                memcg_cancel_update_list_lru_node(&lru->node[i],
                                                  old_size, new_size);
        }
        return -ENOMEM;
}

static void memcg_cancel_update_list_lru(struct list_lru *lru,
                                         int old_size, int new_size)
{
        int i;

        if (!list_lru_memcg_aware(lru))
                return;

        for_each_node(i)
                memcg_cancel_update_list_lru_node(&lru->node[i],
                                                  old_size, new_size);
}

int memcg_update_all_list_lrus(int new_size)
{
        int ret = 0;
        struct list_lru *lru;
        int old_size = memcg_nr_cache_ids;

        mutex_lock(&list_lrus_mutex);
        list_for_each_entry(lru, &list_lrus, list) {
                ret = memcg_update_list_lru(lru, old_size, new_size);
                if (ret)
                        goto fail;
        }
out:
        mutex_unlock(&list_lrus_mutex);
        return ret;
fail:
        list_for_each_entry_continue_reverse(lru, &list_lrus, list)
                memcg_cancel_update_list_lru(lru, old_size, new_size);
        goto out;
}

static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
                                      int src_idx, struct mem_cgroup *dst_memcg)
{
        struct list_lru_node *nlru = &lru->node[nid];
        int dst_idx = dst_memcg->kmemcg_id;
        struct list_lru_one *src, *dst;

        /*
         * Since list_lru_{add,del} may be called under an IRQ-safe lock,
         * we have to use IRQ-safe primitives here to avoid deadlock.
         */
        spin_lock_irq(&nlru->lock);

        src = list_lru_from_memcg_idx(nlru, src_idx);
        dst = list_lru_from_memcg_idx(nlru, dst_idx);

        list_splice_init(&src->list, &dst->list);

        if (src->nr_items) {
                dst->nr_items += src->nr_items;
                set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
                src->nr_items = 0;
        }

        spin_unlock_irq(&nlru->lock);
}

static void memcg_drain_list_lru(struct list_lru *lru,
                                 int src_idx, struct mem_cgroup *dst_memcg)
{
        int i;

        if (!list_lru_memcg_aware(lru))
                return;

        for_each_node(i)
                memcg_drain_list_lru_node(lru, i, src_idx, dst_memcg);
}

void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg)
{
        struct list_lru *lru;

        mutex_lock(&list_lrus_mutex);
        list_for_each_entry(lru, &list_lrus, list)
                memcg_drain_list_lru(lru, src_idx, dst_memcg);
        mutex_unlock(&list_lrus_mutex);
}
#else
static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
{
        return 0;
}

static void memcg_destroy_list_lru(struct list_lru *lru)
{
}
#endif /* CONFIG_MEMCG_KMEM */

int __list_lru_init(struct list_lru *lru, bool memcg_aware,
                    struct lock_class_key *key, struct shrinker *shrinker)
{
        int i;
        int err = -ENOMEM;

#ifdef CONFIG_MEMCG_KMEM
        if (shrinker)
                lru->shrinker_id = shrinker->id;
        else
                lru->shrinker_id = -1;
#endif
        memcg_get_cache_ids();

        lru->node = kcalloc(nr_node_ids, sizeof(*lru->node), GFP_KERNEL);
        if (!lru->node)
                goto out;

        for_each_node(i) {
                spin_lock_init(&lru->node[i].lock);
                if (key)
                        lockdep_set_class(&lru->node[i].lock, key);
                init_one_lru(&lru->node[i].lru);
        }

        err = memcg_init_list_lru(lru, memcg_aware);
        if (err) {
                kfree(lru->node);
                /* Do this so a list_lru_destroy() doesn't crash: */
                lru->node = NULL;
                goto out;
        }

        list_lru_register(lru);
out:
        memcg_put_cache_ids();
        return err;
}
EXPORT_SYMBOL_GPL(__list_lru_init);

void list_lru_destroy(struct list_lru *lru)
{
        /* Already destroyed or not yet initialized? */
        if (!lru->node)
                return;

        memcg_get_cache_ids();

        list_lru_unregister(lru);

        memcg_destroy_list_lru(lru);
        kfree(lru->node);
        lru->node = NULL;

#ifdef CONFIG_MEMCG_KMEM
        lru->shrinker_id = -1;
#endif
        memcg_put_cache_ids();
}
EXPORT_SYMBOL_GPL(list_lru_destroy);