// 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_KMEM
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 struct list_lru_one *
list_lru_from_kmem(struct list_lru *lru, int nid, void *ptr,
struct mem_cgroup **memcg_ptr)
{
struct list_lru_node *nlru = &lru->node[nid];
struct list_lru_one *l = &nlru->lru;
struct mem_cgroup *memcg = NULL;
if (!list_lru_memcg_aware(lru))
goto out;
memcg = mem_cgroup_from_obj(ptr);
if (!memcg)
goto out;
l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_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 *lru, int nid, int idx)
{
return &lru->node[nid].lru;
}
static inline struct list_lru_one *
list_lru_from_kmem(struct list_lru *lru, int nid, void *ptr,
struct mem_cgroup **memcg_ptr)
{
if (memcg_ptr)
*memcg_ptr = NULL;
return &lru->node[nid].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(lru, nid, 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(lru, nid, 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_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 nlru->nr_items;
}
EXPORT_SYMBOL_GPL(list_lru_count_node);
static unsigned long
__list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx,
list_lru_walk_cb isolate, void *cb_arg,
unsigned long *nr_to_walk)
{
struct list_lru_node *nlru = &lru->node[nid];
struct list_lru_one *l;
struct list_head *item, *n;
unsigned long isolated = 0;
restart:
l = list_lru_from_memcg_idx(lru, nid, memcg_idx);
if (!l)
goto out;
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();
}
}
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)
{
struct list_lru_node *nlru = &lru->node[nid];
unsigned long ret;
spin_lock(&nlru->lock);
ret = __list_lru_walk_one(lru, nid, memcg_kmem_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(lru, nid, memcg_kmem_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;
isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
nr_to_walk);
#ifdef CONFIG_MEMCG_KMEM
if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
struct list_lru_memcg *mlru;
unsigned long index;
xa_for_each(&lru->xa, index, mlru) {
struct list_lru_node *nlru = &lru->node[nid];
spin_lock(&nlru->lock);
isolated += __list_lru_walk_one(lru, nid, index,
isolate, cb_arg,
nr_to_walk);
spin_unlock(&nlru->lock);
if (*nr_to_walk <= 0)
break;
}
}
#endif
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 struct list_lru_memcg *memcg_init_list_lru_one(gfp_t gfp)
{
int nid;
struct list_lru_memcg *mlru;
mlru = kmalloc(struct_size(mlru, node, nr_node_ids), gfp);
if (!mlru)
return NULL;
for_each_node(nid)
init_one_lru(&mlru->node[nid]);
return mlru;
}
static void memcg_list_lru_free(struct list_lru *lru, int src_idx)
{
struct list_lru_memcg *mlru = xa_erase_irq(&lru->xa, src_idx);
/*
* The __list_lru_walk_one() can walk the list of this node.
* We need kvfree_rcu() here. And the walking of the list
* is under lru->node[nid]->lock, which can serve as a RCU
* read-side critical section.
*/
if (mlru)
kvfree_rcu(mlru, rcu);
}
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_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(lru, nid, src_idx);
if (!src)
goto out;
dst = list_lru_from_memcg_idx(lru, nid, 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;
}
out:
spin_unlock_irq(&nlru->lock);
}
static void memcg_reparent_list_lru(struct list_lru *lru,
int src_idx, struct mem_cgroup *dst_memcg)
{
int i;
for_each_node(i)
memcg_reparent_list_lru_node(lru, i, src_idx, dst_memcg);
memcg_list_lru_free(lru, src_idx);
}
void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)
{
struct cgroup_subsys_state *css;
struct list_lru *lru;
int src_idx = memcg->kmemcg_id;
/*
* Change kmemcg_id of this cgroup and all its descendants to the
* parent's id, and then move all entries from this cgroup's list_lrus
* to ones of the parent.
*
* After we have finished, all list_lrus corresponding to this cgroup
* are guaranteed to remain empty. So we can safely free this cgroup's
* list lrus in memcg_list_lru_free().
*
* Changing ->kmemcg_id to the parent can prevent memcg_list_lru_alloc()
* from allocating list lrus for this cgroup after memcg_list_lru_free()
* call.
*/
rcu_read_lock();
css_for_each_descendant_pre(css, &memcg->css) {
struct mem_cgroup *child;
child = mem_cgroup_from_css(css);
WRITE_ONCE(child->kmemcg_id, parent->kmemcg_id);
}
rcu_read_unlock();
mutex_lock(&list_lrus_mutex);
list_for_each_entry(lru, &memcg_list_lrus, list)
memcg_reparent_list_lru(lru, src_idx, parent);
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)
{
int i;
unsigned long flags;
struct list_lru_memcg_table {
struct list_lru_memcg *mlru;
struct mem_cgroup *memcg;
} *table;
XA_STATE(xas, &lru->xa, 0);
if (!list_lru_memcg_aware(lru) || memcg_list_lru_allocated(memcg, lru))
return 0;
gfp &= GFP_RECLAIM_MASK;
table = kmalloc_array(memcg->css.cgroup->level, sizeof(*table), gfp);
if (!table)
return -ENOMEM;
/*
* 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.
*/
for (i = 0; memcg; memcg = parent_mem_cgroup(memcg), i++) {
if (memcg_list_lru_allocated(memcg, lru))
break;
table[i].memcg = memcg;
table[i].mlru = memcg_init_list_lru_one(gfp);
if (!table[i].mlru) {
while (i--)
kfree(table[i].mlru);
kfree(table);
return -ENOMEM;
}
}
xas_lock_irqsave(&xas, flags);
while (i--) {
int index = READ_ONCE(table[i].memcg->kmemcg_id);
struct list_lru_memcg *mlru = table[i].mlru;
xas_set(&xas, index);
retry:
if (unlikely(index < 0 || xas_error(&xas) || xas_load(&xas))) {
kfree(mlru);
} else {
xas_store(&xas, mlru);
if (xas_error(&xas) == -ENOMEM) {
xas_unlock_irqrestore(&xas, flags);
if (xas_nomem(&xas, gfp))
xas_set_err(&xas, 0);
xas_lock_irqsave(&xas, flags);
/*
* The xas lock has been released, this memcg
* can be reparented before us. So reload
* memcg id. More details see the comments
* in memcg_reparent_list_lrus().
*/
index = READ_ONCE(table[i].memcg->kmemcg_id);
if (index < 0)
xas_set_err(&xas, 0);
else if (!xas_error(&xas) && index != xas.xa_index)
xas_set(&xas, index);
goto retry;
}
}
}
/* xas_nomem() is used to free memory instead of memory allocation. */
if (xas.xa_alloc)
xas_nomem(&xas, gfp);
xas_unlock_irqrestore(&xas, flags);
kfree(table);
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_KMEM */
int __list_lru_init(struct list_lru *lru, bool memcg_aware,
struct lock_class_key *key, struct shrinker *shrinker)
{
int i;
#ifdef CONFIG_MEMCG_KMEM
if (shrinker)
lru->shrinker_id = shrinker->id;
else
lru->shrinker_id = -1;
#endif
lru->node = kcalloc(nr_node_ids, sizeof(*lru->node), GFP_KERNEL);
if (!lru->node)
return -ENOMEM;
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);
}
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_KMEM
lru->shrinker_id = -1;
#endif
}
EXPORT_SYMBOL_GPL(list_lru_destroy);