Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:3 as permitted sender) client-ip=2620:137:e000::3:3;
MIME-Version: 1.0
References: <20230919171447.2712746-1-nphamcs@gmail.com> <20230919171447.2712746-2-nphamcs@gmail.com>
In-Reply-To: <20230919171447.2712746-2-nphamcs@gmail.com>
From:   Yosry Ahmed <yosryahmed@google.com>
Date:   Mon, 25 Sep 2023 13:17:04 -0700
Message-ID: <CAJD7tkZqm9ZsAL0triwJPLYuN02jMMS-5Y8DE7TuDJVnOCm_7Q@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] zswap: make shrinking memcg-aware
To:     Nhat Pham <nphamcs@gmail.com>
Cc:     akpm@linux-foundation.org, hannes@cmpxchg.org,
        cerasuolodomenico@gmail.com, sjenning@redhat.com,
        ddstreet@ieee.org, vitaly.wool@konsulko.com, mhocko@kernel.org,
        roman.gushchin@linux.dev, shakeelb@google.com,
        muchun.song@linux.dev, linux-mm@kvack.org, kernel-team@meta.com,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        Chris Li <chrisl@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

+Chris Li

On Tue, Sep 19, 2023 at 10:14=E2=80=AFAM Nhat Pham <nphamcs@gmail.com> wrot=
e:
>
> From: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
>
> Currently, we only have a single global LRU for zswap. This makes it
> impossible to perform worload-specific shrinking - an memcg cannot
> determine which pages in the pool it owns, and often ends up writing
> pages from other memcgs. This issue has been previously observed in
> practice and mitigated by simply disabling memcg-initiated shrinking:
>
> https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@gmail.com/T/=
#u
>
> This patch fully resolves the issue by replacing the global zswap LRU
> with memcg- and NUMA-specific LRUs, and modify the reclaim logic:
>
> a) When a store attempt hits an memcg limit, it now triggers a
>    synchronous reclaim attempt that, if successful, allows the new
>    hotter page to be accepted by zswap.
> b) If the store attempt instead hits the global zswap limit, it will
>    trigger an asynchronous reclaim attempt, in which an memcg is
>    selected for reclaim in a round-robin-like fashion.

Hey Nhat,

I didn't take a very close look as I am currently swamped, but going
through the patch I have some comments/questions below.

I am not very familiar with list_lru, but it seems like the existing
API derives the node and memcg from the list item itself. Seems like
we can avoid a lot of changes if we allocate struct zswap_entry from
the same node as the page, and account it to the same memcg. Would
this be too much of a change or too strong of a restriction? It's a
slab allocation and we will free memory on that node/memcg right
after.

>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> Co-developed-by: Nhat Pham <nphamcs@gmail.com>
> Signed-off-by: Nhat Pham <nphamcs@gmail.com>
> ---
>  include/linux/list_lru.h   |  39 +++++++
>  include/linux/memcontrol.h |   5 +
>  include/linux/zswap.h      |   9 ++
>  mm/list_lru.c              |  46 ++++++--
>  mm/swap_state.c            |  19 ++++
>  mm/zswap.c                 | 221 +++++++++++++++++++++++++++++--------
>  6 files changed, 287 insertions(+), 52 deletions(-)
>
> diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
> index b35968ee9fb5..b517b4e2c7c4 100644
> --- a/include/linux/list_lru.h
> +++ b/include/linux/list_lru.h
> @@ -89,6 +89,24 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg=
, struct mem_cgroup *paren
>   */
>  bool list_lru_add(struct list_lru *lru, struct list_head *item);
>
> +/**
> + * __list_lru_add: add an element to a specific sublist.
> + * @list_lru: the lru pointer
> + * @item: the item to be added.
> + * @memcg: the cgroup of the sublist to add the item to.
> + * @nid: the node id of the sublist to add the item to.
> + *
> + * This function is similar to list_lru_add(), but it allows the caller =
to
> + * specify the sublist to which the item should be added. This can be us=
eful
> + * when the list_head node is not necessarily in the same cgroup and NUM=
A node
> + * as the data it represents, such as zswap, where the list_head node co=
uld be
> + * from kswapd and the data from a different cgroup altogether.
> + *
> + * Return value: true if the list was updated, false otherwise
> + */
> +bool __list_lru_add(struct list_lru *lru, struct list_head *item, int ni=
d,
> +               struct mem_cgroup *memcg);
> +
>  /**
>   * list_lru_del: delete an element to the lru list
>   * @list_lru: the lru pointer
> @@ -102,6 +120,18 @@ bool list_lru_add(struct list_lru *lru, struct list_=
head *item);
>   */
>  bool list_lru_del(struct list_lru *lru, struct list_head *item);
>
> +/**
> + * __list_lru_delete: delete an element from a specific sublist.
> + * @list_lru: the lru pointer
> + * @item: the item to be deleted.
> + * @memcg: the cgroup of the sublist to delete the item from.
> + * @nid: the node id of the sublist to delete the item from.
> + *
> + * Return value: true if the list was updated, false otherwise.
> + */
> +bool __list_lru_del(struct list_lru *lru, struct list_head *item, int ni=
d,
> +               struct mem_cgroup *memcg);
> +
>  /**
>   * list_lru_count_one: return the number of objects currently held by @l=
ru
>   * @lru: the lru pointer.
> @@ -137,6 +167,15 @@ void list_lru_isolate(struct list_lru_one *list, str=
uct list_head *item);
>  void list_lru_isolate_move(struct list_lru_one *list, struct list_head *=
item,
>                            struct list_head *head);
>
> +/*
> + * list_lru_putback: undo list_lru_isolate.
> + *
> + * Since we might have dropped the LRU lock in between, recompute list_l=
ru_one
> + * from the node's id and memcg.
> + */
> +void list_lru_putback(struct list_lru *lru, struct list_head *item, int =
nid,
> +               struct mem_cgroup *memcg);
> +
>  typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
>                 struct list_lru_one *list, spinlock_t *lock, void *cb_arg=
);
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 67b823dfa47d..05d34b328d9d 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1179,6 +1179,11 @@ static inline struct mem_cgroup *page_memcg_check(=
struct page *page)
>         return NULL;
>  }
>
> +static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cg=
roup *objcg)
> +{
> +       return NULL;
> +}
> +
>  static inline bool folio_memcg_kmem(struct folio *folio)
>  {
>         return false;
> diff --git a/include/linux/zswap.h b/include/linux/zswap.h
> index 2a60ce39cfde..04f80b64a09b 100644
> --- a/include/linux/zswap.h
> +++ b/include/linux/zswap.h
> @@ -15,6 +15,8 @@ bool zswap_load(struct folio *folio);
>  void zswap_invalidate(int type, pgoff_t offset);
>  void zswap_swapon(int type);
>  void zswap_swapoff(int type);
> +bool zswap_remove_swpentry_from_lru(swp_entry_t swpentry);
> +void zswap_insert_swpentry_into_lru(swp_entry_t swpentry);
>
>  #else
>
> @@ -32,6 +34,13 @@ static inline void zswap_invalidate(int type, pgoff_t =
offset) {}
>  static inline void zswap_swapon(int type) {}
>  static inline void zswap_swapoff(int type) {}
>
> +static inline bool zswap_remove_swpentry_from_lru(swp_entry_t swpentry)
> +{
> +       return false;
> +}
> +
> +static inline void zswap_insert_swpentry_into_lru(swp_entry_t swpentry) =
{}
> +
>  #endif
>
>  #endif /* _LINUX_ZSWAP_H */
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index a05e5bef3b40..37c5c2ef6c0e 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -119,18 +119,26 @@ list_lru_from_kmem(struct list_lru *lru, int nid, v=
oid *ptr,
>  bool list_lru_add(struct list_lru *lru, struct list_head *item)
>  {
>         int nid =3D page_to_nid(virt_to_page(item));
> +       struct mem_cgroup *memcg =3D list_lru_memcg_aware(lru) ?
> +               mem_cgroup_from_slab_obj(item) : NULL;
> +
> +       return __list_lru_add(lru, item, nid, memcg);
> +}
> +EXPORT_SYMBOL_GPL(list_lru_add);
> +
> +bool __list_lru_add(struct list_lru *lru, struct list_head *item, int ni=
d,
> +               struct mem_cgroup *memcg)
> +{
>         struct list_lru_node *nlru =3D &lru->node[nid];
> -       struct mem_cgroup *memcg;
>         struct list_lru_one *l;
>
>         spin_lock(&nlru->lock);
>         if (list_empty(item)) {
> -               l =3D list_lru_from_kmem(lru, nid, item, &memcg);
> +               l =3D list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(mem=
cg));
>                 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));
> +                       set_shrinker_bit(memcg, nid, lru_shrinker_id(lru)=
);

Unrelated diff.

>                 nlru->nr_items++;
>                 spin_unlock(&nlru->lock);
>                 return true;
> @@ -138,17 +146,27 @@ bool list_lru_add(struct list_lru *lru, struct list=
_head *item)
>         spin_unlock(&nlru->lock);
>         return false;
>  }
> -EXPORT_SYMBOL_GPL(list_lru_add);
> +EXPORT_SYMBOL_GPL(__list_lru_add);
>
>  bool list_lru_del(struct list_lru *lru, struct list_head *item)
>  {
>         int nid =3D page_to_nid(virt_to_page(item));
> +       struct mem_cgroup *memcg =3D list_lru_memcg_aware(lru) ?
> +               mem_cgroup_from_slab_obj(item) : NULL;
> +
> +       return __list_lru_del(lru, item, nid, memcg);
> +}
> +EXPORT_SYMBOL_GPL(list_lru_del);
> +
> +bool __list_lru_del(struct list_lru *lru, struct list_head *item, int ni=
d,
> +               struct mem_cgroup *memcg)
> +{
>         struct list_lru_node *nlru =3D &lru->node[nid];
>         struct list_lru_one *l;
>
>         spin_lock(&nlru->lock);
>         if (!list_empty(item)) {
> -               l =3D list_lru_from_kmem(lru, nid, item, NULL);

If we decide to keep the list_lru.c changes, do we have any other
callers of list_lru_from_kmem()?

> +               l =3D list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(mem=
cg));
>                 list_del_init(item);
>                 l->nr_items--;
>                 nlru->nr_items--;
> @@ -158,7 +176,7 @@ bool list_lru_del(struct list_lru *lru, struct list_h=
ead *item)
>         spin_unlock(&nlru->lock);
>         return false;
>  }
> -EXPORT_SYMBOL_GPL(list_lru_del);
> +EXPORT_SYMBOL_GPL(__list_lru_del);
>
>  void list_lru_isolate(struct list_lru_one *list, struct list_head *item)
>  {
> @@ -175,6 +193,20 @@ void list_lru_isolate_move(struct list_lru_one *list=
, struct list_head *item,
>  }
>  EXPORT_SYMBOL_GPL(list_lru_isolate_move);
>
> +void list_lru_putback(struct list_lru *lru, struct list_head *item, int =
nid,
> +               struct mem_cgroup *memcg)
> +{
> +       struct list_lru_one *list =3D
> +               list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
> +
> +       if (list_empty(item)) {
> +               list_add_tail(item, &list->list);
> +               if (!list->nr_items++)
> +                       set_shrinker_bit(memcg, nid, lru_shrinker_id(lru)=
);
> +       }
> +}
> +EXPORT_SYMBOL_GPL(list_lru_putback);
> +
>  unsigned long list_lru_count_one(struct list_lru *lru,
>                                  int nid, struct mem_cgroup *memcg)
>  {
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index b3b14bd0dd64..1c826737aacb 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -21,6 +21,7 @@
>  #include <linux/swap_slots.h>
>  #include <linux/huge_mm.h>
>  #include <linux/shmem_fs.h>
> +#include <linux/zswap.h>
>  #include "internal.h"
>  #include "swap.h"
>
> @@ -417,6 +418,7 @@ struct page *__read_swap_cache_async(swp_entry_t entr=
y, gfp_t gfp_mask,
>         struct folio *folio;
>         struct page *page;
>         void *shadow =3D NULL;
> +       bool zswap_lru_removed =3D false;
>
>         *new_page_allocated =3D false;
>         si =3D get_swap_device(entry);
> @@ -485,6 +487,17 @@ struct page *__read_swap_cache_async(swp_entry_t ent=
ry, gfp_t gfp_mask,
>         __folio_set_locked(folio);
>         __folio_set_swapbacked(folio);
>
> +       /*
> +        * Page fault might itself trigger reclaim, on a zswap object tha=
t
> +        * corresponds to the same swap entry. However, as the swap entry=
 has
> +        * previously been pinned, the task will run into an infinite loo=
p trying
> +        * to pin the swap entry again.
> +        *
> +        * To prevent this from happening, we remove it from the zswap
> +        * LRU to prevent its reclamation.
> +        */
> +       zswap_lru_removed =3D zswap_remove_swpentry_from_lru(entry);
> +

This will add a zswap lookup (and potentially an insertion below) in
every single swap fault path, right?. Doesn't this introduce latency
regressions? I am also not a fan of having zswap-specific details in
this path.

When you say "pinned", do you mean the call to swapcache_prepare()
above (i.e. setting SWAP_HAS_CACHE)? IIUC, the scenario you are
worried about is that the following call to charge the page may invoke
reclaim, go into zswap, and try to writeback the same page we are
swapping in here. The writeback call will recurse into
__read_swap_cache_async(), call swapcache_prepare() and get EEXIST,
and keep looping indefinitely. Is this correct?

If yes, can we handle this by adding a flag to
__read_swap_cache_async() that basically says "don't wait for
SWAP_HAS_CACHE and the swapcache to be consistent, if
swapcache_prepare() returns EEXIST just fail and return"? The zswap
writeback path can pass in this flag and skip such pages. We might
want to modify the writeback code to put back those pages at the end
of the lru instead of in the beginning.

>         if (mem_cgroup_swapin_charge_folio(folio, NULL, gfp_mask, entry))
>                 goto fail_unlock;
>
> @@ -497,6 +510,9 @@ struct page *__read_swap_cache_async(swp_entry_t entr=
y, gfp_t gfp_mask,
>         if (shadow)
>                 workingset_refault(folio, shadow);
>
> +       if (zswap_lru_removed)
> +               zswap_insert_swpentry_into_lru(entry);
> +
>         /* Caller will initiate read into locked folio */
>         folio_add_lru(folio);
>         *new_page_allocated =3D true;
> @@ -506,6 +522,9 @@ struct page *__read_swap_cache_async(swp_entry_t entr=
y, gfp_t gfp_mask,
>         return page;
>
>  fail_unlock:
> +       if (zswap_lru_removed)
> +               zswap_insert_swpentry_into_lru(entry);
> +
>         put_swap_folio(folio, entry);
>         folio_unlock(folio);
>         folio_put(folio);
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 412b1409a0d7..1a469e5d5197 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -34,6 +34,7 @@
>  #include <linux/writeback.h>
>  #include <linux/pagemap.h>
>  #include <linux/workqueue.h>
> +#include <linux/list_lru.h>
>
>  #include "swap.h"
>  #include "internal.h"
> @@ -171,8 +172,8 @@ struct zswap_pool {
>         struct work_struct shrink_work;
>         struct hlist_node node;
>         char tfm_name[CRYPTO_MAX_ALG_NAME];
> -       struct list_head lru;
> -       spinlock_t lru_lock;
> +       struct list_lru list_lru;
> +       struct mem_cgroup *next_shrink;
>  };
>
>  /*
> @@ -209,6 +210,7 @@ struct zswap_entry {
>                 unsigned long value;
>         };
>         struct obj_cgroup *objcg;
> +       int nid;
>         struct list_head lru;
>  };

Ideally this can be avoided if we can allocate struct zswap_entry on
the correct node.

>
> @@ -309,6 +311,29 @@ static void zswap_entry_cache_free(struct zswap_entr=
y *entry)
>         kmem_cache_free(zswap_entry_cache, entry);
>  }
>
> +/*********************************
> +* lru functions
> +**********************************/
> +static bool zswap_lru_add(struct list_lru *list_lru, struct zswap_entry =
*entry)
> +{
> +       struct mem_cgroup *memcg =3D entry->objcg ?
> +               get_mem_cgroup_from_objcg(entry->objcg) : NULL;

This line is repeated at least 3 times, perhaps add a helper for it?
get_mem_cgroup_from_zswap()?

> +       bool added =3D __list_lru_add(list_lru, &entry->lru, entry->nid, =
memcg);
> +
> +       mem_cgroup_put(memcg);
> +       return added;
> +}
> +
> +static bool zswap_lru_del(struct list_lru *list_lru, struct zswap_entry =
*entry)
> +{
> +       struct mem_cgroup *memcg =3D entry->objcg ?
> +               get_mem_cgroup_from_objcg(entry->objcg) : NULL;
> +       bool removed =3D __list_lru_del(list_lru, &entry->lru, entry->nid=
, memcg);
> +
> +       mem_cgroup_put(memcg);
> +       return removed;
> +}
> +
>  /*********************************
>  * rbtree functions
>  **********************************/
> @@ -393,9 +418,7 @@ static void zswap_free_entry(struct zswap_entry *entr=
y)
>         if (!entry->length)
>                 atomic_dec(&zswap_same_filled_pages);
>         else {
> -               spin_lock(&entry->pool->lru_lock);
> -               list_del(&entry->lru);
> -               spin_unlock(&entry->pool->lru_lock);
> +               zswap_lru_del(&entry->pool->list_lru, entry);
>                 zpool_free(zswap_find_zpool(entry), entry->handle);
>                 zswap_pool_put(entry->pool);
>         }
> @@ -629,21 +652,16 @@ static void zswap_invalidate_entry(struct zswap_tre=
e *tree,
>                 zswap_entry_put(tree, entry);
>  }
>
> -static int zswap_reclaim_entry(struct zswap_pool *pool)
> +static enum lru_status shrink_memcg_cb(struct list_head *item, struct li=
st_lru_one *l,
> +                                      spinlock_t *lock, void *arg)
>  {
> -       struct zswap_entry *entry;
> +       struct zswap_entry *entry =3D container_of(item, struct zswap_ent=
ry, lru);
> +       struct mem_cgroup *memcg;
>         struct zswap_tree *tree;
>         pgoff_t swpoffset;
> -       int ret;
> +       enum lru_status ret =3D LRU_REMOVED_RETRY;
> +       int writeback_result;
>
> -       /* Get an entry off the LRU */
> -       spin_lock(&pool->lru_lock);
> -       if (list_empty(&pool->lru)) {
> -               spin_unlock(&pool->lru_lock);
> -               return -EINVAL;
> -       }
> -       entry =3D list_last_entry(&pool->lru, struct zswap_entry, lru);
> -       list_del_init(&entry->lru);
>         /*
>          * Once the lru lock is dropped, the entry might get freed. The
>          * swpoffset is copied to the stack, and entry isn't deref'd agai=
n
> @@ -651,26 +669,35 @@ static int zswap_reclaim_entry(struct zswap_pool *p=
ool)
>          */
>         swpoffset =3D swp_offset(entry->swpentry);
>         tree =3D zswap_trees[swp_type(entry->swpentry)];
> -       spin_unlock(&pool->lru_lock);
> +       list_lru_isolate(l, item);
> +       spin_unlock(lock);
>
>         /* Check for invalidate() race */
>         spin_lock(&tree->lock);
>         if (entry !=3D zswap_rb_search(&tree->rbroot, swpoffset)) {
> -               ret =3D -EAGAIN;
>                 goto unlock;
>         }
>         /* Hold a reference to prevent a free during writeback */
>         zswap_entry_get(entry);
>         spin_unlock(&tree->lock);
>
> -       ret =3D zswap_writeback_entry(entry, tree);
> +       writeback_result =3D zswap_writeback_entry(entry, tree);
>
>         spin_lock(&tree->lock);
> -       if (ret) {
> -               /* Writeback failed, put entry back on LRU */
> -               spin_lock(&pool->lru_lock);
> -               list_move(&entry->lru, &pool->lru);
> -               spin_unlock(&pool->lru_lock);
> +       if (writeback_result) {
> +               zswap_reject_reclaim_fail++;
> +
> +               /* Check for invalidate() race */
> +               if (entry !=3D zswap_rb_search(&tree->rbroot, swpoffset))
> +                       goto put_unlock;
> +
> +               memcg =3D entry->objcg ? get_mem_cgroup_from_objcg(entry-=
>objcg) : NULL;
> +               spin_lock(lock);
> +               /* we cannot use zswap_lru_add here, because it increment=
s node's lru count */
> +               list_lru_putback(&entry->pool->list_lru, item, entry->nid=
, memcg);
> +               spin_unlock(lock);
> +               mem_cgroup_put(memcg);
> +               ret =3D LRU_RETRY;
>                 goto put_unlock;
>         }
>
> @@ -686,19 +713,63 @@ static int zswap_reclaim_entry(struct zswap_pool *p=
ool)
>         zswap_entry_put(tree, entry);
>  unlock:
>         spin_unlock(&tree->lock);
> -       return ret ? -EAGAIN : 0;
> +       spin_lock(lock);
> +       return ret;
> +}
> +
> +static int shrink_memcg(struct mem_cgroup *memcg)
> +{
> +       struct zswap_pool *pool;
> +       int nid, shrunk =3D 0;
> +       bool is_empty =3D true;
> +
> +       pool =3D zswap_pool_current_get();
> +       if (!pool)
> +               return -EINVAL;
> +
> +       for_each_node_state(nid, N_NORMAL_MEMORY) {
> +               unsigned long nr_to_walk =3D 1;
> +
> +               if (list_lru_walk_one(&pool->list_lru, nid, memcg, &shrin=
k_memcg_cb,
> +                                     NULL, &nr_to_walk))
> +                       shrunk++;
> +               if (!nr_to_walk)

nr_to_walk will be 0 if we shrunk 1 page, so it's the same condition
as the above, right?

is_empty seems to be shrunk =3D=3D 0 if I understand correctly, seems like
there is no need for both.

> +                       is_empty =3D false;
> +       }
> +       zswap_pool_put(pool);
> +
> +       if (is_empty)
> +               return -EINVAL;
> +       if (shrunk)
> +               return 0;
> +       return -EAGAIN;
>  }
>
>  static void shrink_worker(struct work_struct *w)
>  {
>         struct zswap_pool *pool =3D container_of(w, typeof(*pool),
>                                                 shrink_work);
> -       int ret, failures =3D 0;
> +       int ret, failures =3D 0, memcg_selection_failures =3D 0;
>
> +       /* global reclaim will select cgroup in a round-robin fashion. */
>         do {
> -               ret =3D zswap_reclaim_entry(pool);
> +               /* previous next_shrink has become a zombie - restart fro=
m the top */

Do we skip zombies because all zswap entries are reparented with the objcg?

If yes, why do we restart from the top instead of just skipping them?
memcgs after a zombie will not be reachable now IIUC.

Also, why explicitly check for zombies instead of having
shrink_memcg() just skip memcgs with no zswap entries? The logic is
slightly complicated.

> +               if (pool->next_shrink && !mem_cgroup_online(pool->next_sh=
rink)) {
> +                       mem_cgroup_put(pool->next_shrink);
> +                       pool->next_shrink =3D NULL;
> +               }
> +               pool->next_shrink =3D mem_cgroup_iter(NULL, pool->next_sh=
rink, NULL);
> +
> +               /* fails to find a suitable cgroup - give the worker anot=
her chance. */
> +               if (!pool->next_shrink) {
> +                       if (++memcg_selection_failures =3D=3D 2)
> +                               break;
> +                       continue;
> +               }
> +
> +               ret =3D shrink_memcg(pool->next_shrink);
> +
>                 if (ret) {
> -                       zswap_reject_reclaim_fail++;
>                         if (ret !=3D -EAGAIN)
>                                 break;
>                         if (++failures =3D=3D MAX_RECLAIM_RETRIES)
> @@ -764,9 +835,8 @@ static struct zswap_pool *zswap_pool_create(char *typ=
e, char *compressor)
>          */
>         kref_init(&pool->kref);
>         INIT_LIST_HEAD(&pool->list);
> -       INIT_LIST_HEAD(&pool->lru);
> -       spin_lock_init(&pool->lru_lock);
>         INIT_WORK(&pool->shrink_work, shrink_worker);
> +       list_lru_init_memcg(&pool->list_lru, NULL);
>
>         zswap_pool_debug("created", pool);
>
> @@ -831,6 +901,9 @@ static void zswap_pool_destroy(struct zswap_pool *poo=
l)
>
>         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->no=
de);
>         free_percpu(pool->acomp_ctx);
> +       list_lru_destroy(&pool->list_lru);
> +       if (pool->next_shrink)
> +               mem_cgroup_put(pool->next_shrink);
>         for (i =3D 0; i < ZSWAP_NR_ZPOOLS; i++)
>                 zpool_destroy_pool(pool->zpools[i]);
>         kfree(pool);
> @@ -1199,8 +1272,10 @@ bool zswap_store(struct folio *folio)
>         struct scatterlist input, output;
>         struct crypto_acomp_ctx *acomp_ctx;
>         struct obj_cgroup *objcg =3D NULL;
> +       struct mem_cgroup *memcg =3D NULL;
>         struct zswap_pool *pool;
>         struct zpool *zpool;
> +       int lru_alloc_ret;
>         unsigned int dlen =3D PAGE_SIZE;
>         unsigned long handle, value;
>         char *buf;
> @@ -1218,14 +1293,15 @@ bool zswap_store(struct folio *folio)
>         if (!zswap_enabled || !tree)
>                 return false;
>
> -       /*
> -        * XXX: zswap reclaim does not work with cgroups yet. Without a
> -        * cgroup-aware entry LRU, we will push out entries system-wide b=
ased on
> -        * local cgroup limits.
> -        */
>         objcg =3D get_obj_cgroup_from_folio(folio);
> -       if (objcg && !obj_cgroup_may_zswap(objcg))
> -               goto reject;
> +       if (objcg && !obj_cgroup_may_zswap(objcg)) {
> +               memcg =3D get_mem_cgroup_from_objcg(objcg);
> +               if (shrink_memcg(memcg)) {
> +                       mem_cgroup_put(memcg);
> +                       goto reject;
> +               }
> +               mem_cgroup_put(memcg);
> +       }
>
>         /* reclaim space if needed */
>         if (zswap_is_full()) {
> @@ -1240,7 +1316,11 @@ bool zswap_store(struct folio *folio)
>                 else
>                         zswap_pool_reached_full =3D false;
>         }
> -
> +       pool =3D zswap_pool_current_get();
> +       if (!pool) {
> +               ret =3D -EINVAL;
> +               goto reject;
> +       }
>         /* allocate entry */
>         entry =3D zswap_entry_cache_alloc(GFP_KERNEL);
>         if (!entry) {
> @@ -1256,6 +1336,7 @@ bool zswap_store(struct folio *folio)
>                         entry->length =3D 0;
>                         entry->value =3D value;
>                         atomic_inc(&zswap_same_filled_pages);
> +                       zswap_pool_put(pool);
>                         goto insert_entry;
>                 }
>                 kunmap_atomic(src);
> @@ -1264,6 +1345,15 @@ bool zswap_store(struct folio *folio)
>         if (!zswap_non_same_filled_pages_enabled)
>                 goto freepage;
>
> +       if (objcg) {
> +               memcg =3D get_mem_cgroup_from_objcg(objcg);
> +               lru_alloc_ret =3D memcg_list_lru_alloc(memcg, &pool->list=
_lru, GFP_KERNEL);
> +               mem_cgroup_put(memcg);
> +
> +               if (lru_alloc_ret)
> +                       goto freepage;
> +       }
> +
>         /* if entry is successfully added, it keeps the reference */
>         entry->pool =3D zswap_pool_current_get();
>         if (!entry->pool)
> @@ -1325,6 +1415,7 @@ bool zswap_store(struct folio *folio)
>
>  insert_entry:
>         entry->objcg =3D objcg;
> +       entry->nid =3D page_to_nid(page);
>         if (objcg) {
>                 obj_cgroup_charge_zswap(objcg, entry->length);
>                 /* Account before objcg ref is moved to tree */
> @@ -1338,9 +1429,8 @@ bool zswap_store(struct folio *folio)
>                 zswap_invalidate_entry(tree, dupentry);
>         }
>         if (entry->length) {
> -               spin_lock(&entry->pool->lru_lock);
> -               list_add(&entry->lru, &entry->pool->lru);
> -               spin_unlock(&entry->pool->lru_lock);
> +               INIT_LIST_HEAD(&entry->lru);
> +               zswap_lru_add(&pool->list_lru, entry);
>         }
>         spin_unlock(&tree->lock);
>
> @@ -1447,9 +1537,8 @@ bool zswap_load(struct folio *folio)
>                 zswap_invalidate_entry(tree, entry);
>                 folio_mark_dirty(folio);
>         } else if (entry->length) {
> -               spin_lock(&entry->pool->lru_lock);
> -               list_move(&entry->lru, &entry->pool->lru);
> -               spin_unlock(&entry->pool->lru_lock);
> +               zswap_lru_del(&entry->pool->list_lru, entry);
> +               zswap_lru_add(&entry->pool->list_lru, entry);
>         }
>         zswap_entry_put(tree, entry);
>         spin_unlock(&tree->lock);
> @@ -1507,6 +1596,48 @@ void zswap_swapoff(int type)
>         zswap_trees[type] =3D NULL;
>  }
>
> +bool zswap_remove_swpentry_from_lru(swp_entry_t swpentry)
> +{
> +       struct zswap_tree *tree =3D zswap_trees[swp_type(swpentry)];
> +       struct zswap_entry *entry;
> +       struct zswap_pool *pool;
> +       bool removed =3D false;
> +
> +       /* get the zswap entry and prevent it from being freed */
> +       spin_lock(&tree->lock);
> +       entry =3D zswap_rb_search(&tree->rbroot, swp_offset(swpentry));
> +       /* skip if the entry is already written back or is a same filled =
page */
> +       if (!entry || !entry->length)
> +               goto tree_unlock;
> +
> +       pool =3D entry->pool;
> +       removed =3D zswap_lru_del(&pool->list_lru, entry);
> +
> +tree_unlock:
> +       spin_unlock(&tree->lock);
> +       return removed;
> +}
> +
> +void zswap_insert_swpentry_into_lru(swp_entry_t swpentry)
> +{
> +       struct zswap_tree *tree =3D zswap_trees[swp_type(swpentry)];
> +       struct zswap_entry *entry;
> +       struct zswap_pool *pool;
> +
> +       /* get the zswap entry and prevent it from being freed */
> +       spin_lock(&tree->lock);
> +       entry =3D zswap_rb_search(&tree->rbroot, swp_offset(swpentry));
> +       /* skip if the entry is already written back or is a same filled =
page */
> +       if (!entry || !entry->length)
> +               goto tree_unlock;
> +
> +       pool =3D entry->pool;
> +       zswap_lru_add(&pool->list_lru, entry);
> +
> +tree_unlock:
> +       spin_unlock(&tree->lock);
> +}
> +
>  /*********************************
>  * debugfs functions
>  **********************************/
> @@ -1560,7 +1691,7 @@ static int zswap_setup(void)
>         struct zswap_pool *pool;
>         int ret;
>
> -       zswap_entry_cache =3D KMEM_CACHE(zswap_entry, 0);
> +       zswap_entry_cache =3D KMEM_CACHE(zswap_entry, SLAB_ACCOUNT);
>         if (!zswap_entry_cache) {
>                 pr_err("entry cache creation failed\n");
>                 goto cache_fail;
> --
> 2.34.1