// 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"
#include "internal.h"

#ifdef CONFIG_MEMCG
static LIST_HEAD(memcg_list_lrus);
static DEFINE_MUTEX(list_lrus_mutex);

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

static void list_lru_register(struct list_lru *lru)
{
        if (!list_lru_memcg_aware(lru))
                return;

        mutex_lock(&list_lrus_mutex);
        list_add(&lru->list, &memcg_list_lrus);
        mutex_unlock(&list_lrus_mutex);
}

static void list_lru_unregister(struct list_lru *lru)
{
        if (!list_lru_memcg_aware(lru))
                return;

        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 struct list_lru_one *
list_lru_from_memcg_idx(struct list_lru *lru, int nid, int idx)
{
        if (list_lru_memcg_aware(lru) && idx >= 0) {
                struct list_lru_memcg *mlru = xa_load(&lru->xa, idx);

                return mlru ? &mlru->node[nid] : NULL;
        }
        return &lru->node[nid].lru;
}

static inline bool lock_list_lru(struct list_lru_one *l, bool irq)
{
        if (irq)
                spin_lock_irq(&l->lock);
        else
                spin_lock(&l->lock);
        if (unlikely(READ_ONCE(l->nr_items) == LONG_MIN)) {
                if (irq)
                        spin_unlock_irq(&l->lock);
                else
                        spin_unlock(&l->lock);
                return false;
        }
        return true;
}

static inline struct list_lru_one *
lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
                       bool irq, bool skip_empty)
{
        struct list_lru_one *l;

        rcu_read_lock();
again:
        l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
        if (likely(l) && lock_list_lru(l, irq)) {
                rcu_read_unlock();
                return l;
        }
        /*
         * Caller may simply bail out if raced with reparenting or
         * may iterate through the list_lru and expect empty slots.
         */
        if (skip_empty) {
                rcu_read_unlock();
                return NULL;
        }
        VM_WARN_ON(!css_is_dying(&memcg->css));
        memcg = parent_mem_cgroup(memcg);
        goto again;
}

static inline void unlock_list_lru(struct list_lru_one *l, bool irq_off)
{
        if (irq_off)
                spin_unlock_irq(&l->lock);
        else
                spin_unlock(&l->lock);
}
#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 *lru, int nid, int idx)
{
        return &lru->node[nid].lru;
}

static inline struct list_lru_one *
lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
                       bool irq, bool skip_empty)
{
        struct list_lru_one *l = &lru->node[nid].lru;

        if (irq)
                spin_lock_irq(&l->lock);
        else
                spin_lock(&l->lock);

        return l;
}

static inline void unlock_list_lru(struct list_lru_one *l, bool irq_off)
{
        if (irq_off)
                spin_unlock_irq(&l->lock);
        else
                spin_unlock(&l->lock);
}
#endif /* CONFIG_MEMCG */

/* The caller must ensure the memcg lifetime. */
bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
                  struct mem_cgroup *memcg)
{
        struct list_lru_node *nlru = &lru->node[nid];
        struct list_lru_one *l;

        l = lock_list_lru_of_memcg(lru, nid, memcg, false, false);
        if (!l)
                return false;
        if (list_empty(item)) {
                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));
                unlock_list_lru(l, false);
                atomic_long_inc(&nlru->nr_items);
                return true;
        }
        unlock_list_lru(l, false);
        return false;
}

bool list_lru_add_obj(struct list_lru *lru, struct list_head *item)
{
        bool ret;
        int nid = page_to_nid(virt_to_page(item));

        if (list_lru_memcg_aware(lru)) {
                rcu_read_lock();
                ret = list_lru_add(lru, item, nid, mem_cgroup_from_virt(item));
                rcu_read_unlock();
        } else {
                ret = list_lru_add(lru, item, nid, NULL);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(list_lru_add_obj);

/* The caller must ensure the memcg lifetime. */
bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
                  struct mem_cgroup *memcg)
{
        struct list_lru_node *nlru = &lru->node[nid];
        struct list_lru_one *l;
        l = lock_list_lru_of_memcg(lru, nid, memcg, false, false);
        if (!l)
                return false;
        if (!list_empty(item)) {
                list_del_init(item);
                l->nr_items--;
                unlock_list_lru(l, false);
                atomic_long_dec(&nlru->nr_items);
                return true;
        }
        unlock_list_lru(l, false);
        return false;
}

bool list_lru_del_obj(struct list_lru *lru, struct list_head *item)
{
        bool ret;
        int nid = page_to_nid(virt_to_page(item));

        if (list_lru_memcg_aware(lru)) {
                rcu_read_lock();
                ret = list_lru_del(lru, item, nid, mem_cgroup_from_virt(item));
                rcu_read_unlock();
        } else {
                ret = list_lru_del(lru, item, nid, NULL);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(list_lru_del_obj);

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_one *l;
        long count;

        rcu_read_lock();
        l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
        count = l ? READ_ONCE(l->nr_items) : 0;
        rcu_read_unlock();

        if (unlikely(count < 0))
                count = 0;

        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 atomic_long_read(&nlru->nr_items);
}
EXPORT_SYMBOL_GPL(list_lru_count_node);

static 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, bool irq_off)
{
        struct list_lru_node *nlru = &lru->node[nid];
        struct list_lru_one *l = NULL;
        struct list_head *item, *n;
        unsigned long isolated = 0;

restart:
        l = lock_list_lru_of_memcg(lru, nid, memcg, irq_off, true);
        if (!l)
                return isolated;
        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, cb_arg);
                switch (ret) {
                /*
                 * LRU_RETRY, LRU_REMOVED_RETRY and LRU_STOP will drop the lru
                 * lock. List traversal will have to restart from scratch.
                 */
                case LRU_RETRY:
                        goto restart;
                case LRU_REMOVED_RETRY:
                        fallthrough;
                case LRU_REMOVED:
                        isolated++;
                        atomic_long_dec(&nlru->nr_items);
                        if (ret == LRU_REMOVED_RETRY)
                                goto restart;
                        break;
                case LRU_ROTATE:
                        list_move_tail(item, &l->list);
                        break;
                case LRU_SKIP:
                        break;
                case LRU_STOP:
                        goto out;
                default:
                        BUG();
                }
        }
        unlock_list_lru(l, irq_off);
out:
        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)
{
        return __list_lru_walk_one(lru, nid, memcg, isolate,
                                   cb_arg, nr_to_walk, false);
}
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)
{
        return __list_lru_walk_one(lru, nid, memcg, isolate,
                                   cb_arg, nr_to_walk, true);
}

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;

        isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
                                      nr_to_walk);

#ifdef CONFIG_MEMCG
        if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
                struct list_lru_memcg *mlru;
                struct mem_cgroup *memcg;
                unsigned long index;

                xa_for_each(&lru->xa, index, mlru) {
                        rcu_read_lock();
                        memcg = mem_cgroup_from_private_id(index);
                        if (!mem_cgroup_tryget(memcg)) {
                                rcu_read_unlock();
                                continue;
                        }
                        rcu_read_unlock();
                        isolated += __list_lru_walk_one(lru, nid, memcg,
                                                        isolate, cb_arg,
                                                        nr_to_walk, false);
                        mem_cgroup_put(memcg);

                        if (*nr_to_walk <= 0)
                                break;
                }
        }
#endif

        return isolated;
}
EXPORT_SYMBOL_GPL(list_lru_walk_node);

static void init_one_lru(struct list_lru *lru, struct list_lru_one *l)
{
        INIT_LIST_HEAD(&l->list);
        spin_lock_init(&l->lock);
        l->nr_items = 0;
#ifdef CONFIG_LOCKDEP
        if (lru->key)
                lockdep_set_class(&l->lock, lru->key);
#endif
}

#ifdef CONFIG_MEMCG
static struct list_lru_memcg *memcg_init_list_lru_one(struct list_lru *lru, gfp_t gfp)
{
        int nid;
        struct list_lru_memcg *mlru;

        mlru = kmalloc_flex(*mlru, node, nr_node_ids, gfp);
        if (!mlru)
                return NULL;

        for_each_node(nid)
                init_one_lru(lru, &mlru->node[nid]);

        return mlru;
}

static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
{
        if (memcg_aware)
                xa_init_flags(&lru->xa, XA_FLAGS_LOCK_IRQ);
        lru->memcg_aware = memcg_aware;
}

static void memcg_destroy_list_lru(struct list_lru *lru)
{
        XA_STATE(xas, &lru->xa, 0);
        struct list_lru_memcg *mlru;

        if (!list_lru_memcg_aware(lru))
                return;

        xas_lock_irq(&xas);
        xas_for_each(&xas, mlru, ULONG_MAX) {
                kfree(mlru);
                xas_store(&xas, NULL);
        }
        xas_unlock_irq(&xas);
}

static void memcg_reparent_list_lru_one(struct list_lru *lru, int nid,
                                        struct list_lru_one *src,
                                        struct mem_cgroup *dst_memcg)
{
        int dst_idx = dst_memcg->kmemcg_id;
        struct list_lru_one *dst;

        spin_lock_irq(&src->lock);
        dst = list_lru_from_memcg_idx(lru, nid, dst_idx);
        spin_lock_nested(&dst->lock, SINGLE_DEPTH_NESTING);

        list_splice_init(&src->list, &dst->list);
        if (src->nr_items) {
                WARN_ON(src->nr_items < 0);
                dst->nr_items += src->nr_items;
                set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));
        }
        /* Mark the list_lru_one dead */
        src->nr_items = LONG_MIN;

        spin_unlock(&dst->lock);
        spin_unlock_irq(&src->lock);
}

void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)
{
        struct list_lru *lru;
        int i;

        mutex_lock(&list_lrus_mutex);
        list_for_each_entry(lru, &memcg_list_lrus, list) {
                struct list_lru_memcg *mlru;
                XA_STATE(xas, &lru->xa, memcg->kmemcg_id);

                /*
                 * Lock the Xarray to ensure no on going list_lru_memcg
                 * allocation and further allocation will see css_is_dying().
                 */
                xas_lock_irq(&xas);
                mlru = xas_store(&xas, NULL);
                xas_unlock_irq(&xas);
                if (!mlru)
                        continue;

                /*
                 * With Xarray value set to NULL, holding the lru lock below
                 * prevents list_lru_{add,del,isolate} from touching the lru,
                 * safe to reparent.
                 */
                for_each_node(i)
                        memcg_reparent_list_lru_one(lru, i, &mlru->node[i], parent);

                /*
                 * Here all list_lrus corresponding to the cgroup are guaranteed
                 * to remain empty, we can safely free this lru, any further
                 * memcg_list_lru_alloc() call will simply bail out.
                 */
                kvfree_rcu(mlru, rcu);
        }
        mutex_unlock(&list_lrus_mutex);
}

static inline bool memcg_list_lru_allocated(struct mem_cgroup *memcg,
                                            struct list_lru *lru)
{
        int idx = memcg->kmemcg_id;

        return idx < 0 || xa_load(&lru->xa, idx);
}

int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
                         gfp_t gfp)
{
        unsigned long flags;
        struct list_lru_memcg *mlru = NULL;
        struct mem_cgroup *pos, *parent;
        XA_STATE(xas, &lru->xa, 0);

        if (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru))
                return 0;

        gfp &= GFP_RECLAIM_MASK;
        /*
         * Because the list_lru can be reparented to the parent cgroup's
         * list_lru, we should make sure that this cgroup and all its
         * ancestors have allocated list_lru_memcg.
         */
        do {
                /*
                 * Keep finding the farest parent that wasn't populated
                 * until found memcg itself.
                 */
                pos = memcg;
                parent = parent_mem_cgroup(pos);
                while (!memcg_list_lru_allocated(parent, lru)) {
                        pos = parent;
                        parent = parent_mem_cgroup(pos);
                }

                if (!mlru) {
                        mlru = memcg_init_list_lru_one(lru, gfp);
                        if (!mlru)
                                return -ENOMEM;
                }
                xas_set(&xas, pos->kmemcg_id);
                do {
                        xas_lock_irqsave(&xas, flags);
                        if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
                                xas_store(&xas, mlru);
                                if (!xas_error(&xas))
                                        mlru = NULL;
                        }
                        xas_unlock_irqrestore(&xas, flags);
                } while (xas_nomem(&xas, gfp));
        } while (pos != memcg && !css_is_dying(&pos->css));

        if (unlikely(mlru))
                kfree(mlru);

        return xas_error(&xas);
}
#else
static inline void memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
{
}

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

int __list_lru_init(struct list_lru *lru, bool memcg_aware, struct shrinker *shrinker)
{
        int i;

#ifdef CONFIG_MEMCG
        if (shrinker)
                lru->shrinker_id = shrinker->id;
        else
                lru->shrinker_id = -1;

        if (mem_cgroup_kmem_disabled())
                memcg_aware = false;
#endif

        lru->node = kzalloc_objs(*lru->node, nr_node_ids);
        if (!lru->node)
                return -ENOMEM;

        for_each_node(i)
                init_one_lru(lru, &lru->node[i].lru);

        memcg_init_list_lru(lru, memcg_aware);
        list_lru_register(lru);

        return 0;
}
EXPORT_SYMBOL_GPL(__list_lru_init);

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

        list_lru_unregister(lru);

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

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