Re: [PATCH v8 3/6] zswap: make shrinking memcg-aware

Nhat Pham
2023-12-05T18:49:41Z

On Tue, Dec 5, 2023 at 10:21 AM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Thu, Nov 30, 2023 at 11:40 AM Nhat Pham <nphamcs@gmail.com> wrote:
> >
> > 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.
> >
> > 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/memcontrol.h | 5 +
> > include/linux/zswap.h | 2 +
> > mm/memcontrol.c | 2 +
> > mm/swap.h | 3 +-
> > mm/swap_state.c | 24 +++-
> > mm/zswap.c | 269 +++++++++++++++++++++++++++++--------
> > 6 files changed, 245 insertions(+), 60 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 2bd7d14ace78..a308c8eacf20 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -1192,6 +1192,11 @@ 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_cgroup *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..e571e393669b 100644
> > --- a/include/linux/zswap.h
> > +++ b/include/linux/zswap.h
> > @@ -15,6 +15,7 @@ bool zswap_load(struct folio *folio);
> > void zswap_invalidate(int type, pgoff_t offset);
> > void zswap_swapon(int type);
> > void zswap_swapoff(int type);
> > +void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg);
> >
> > #else
> >
> > @@ -31,6 +32,7 @@ static inline bool zswap_load(struct folio *folio)
> > 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 void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg) {}
> >
> > #endif
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 470821d1ba1a..792ca21c5815 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -5614,6 +5614,8 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> > page_counter_set_min(&memcg->memory, 0);
> > page_counter_set_low(&memcg->memory, 0);
> >
> > + zswap_memcg_offline_cleanup(memcg);
> > +
> > memcg_offline_kmem(memcg);
> > reparent_shrinker_deferred(memcg);
> > wb_memcg_offline(memcg);
> > diff --git a/mm/swap.h b/mm/swap.h
> > index 73c332ee4d91..c0dc73e10e91 100644
> > --- a/mm/swap.h
> > +++ b/mm/swap.h
> > @@ -51,7 +51,8 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> > struct swap_iocb **plug);
> > struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> > struct mempolicy *mpol, pgoff_t ilx,
> > - bool *new_page_allocated);
> > + bool *new_page_allocated,
> > + bool skip_if_exists);
> > struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
> > struct mempolicy *mpol, pgoff_t ilx);
> > struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
> > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > index 85d9e5806a6a..6c84236382f3 100644
> > --- a/mm/swap_state.c
> > +++ b/mm/swap_state.c
> > @@ -412,7 +412,8 @@ struct folio *filemap_get_incore_folio(struct address_space *mapping,
> >
> > struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> > struct mempolicy *mpol, pgoff_t ilx,
> > - bool *new_page_allocated)
> > + bool *new_page_allocated,
> > + bool skip_if_exists)
> > {
> > struct swap_info_struct *si;
> > struct folio *folio;
> > @@ -470,6 +471,17 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> > if (err != -EEXIST)
> > goto fail_put_swap;
> >
> > + /*
> > + * Protect against a recursive call to __read_swap_cache_async()
> > + * on the same entry waiting forever here because SWAP_HAS_CACHE
> > + * is set but the folio is not the swap cache yet. This can
> > + * happen today if mem_cgroup_swapin_charge_folio() below
> > + * triggers reclaim through zswap, which may call
> > + * __read_swap_cache_async() in the writeback path.
> > + */
> > + if (skip_if_exists)
> > + goto fail_put_swap;
> > +
> > /*
> > * We might race against __delete_from_swap_cache(), and
> > * stumble across a swap_map entry whose SWAP_HAS_CACHE
> > @@ -537,7 +549,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> >
> > mpol = get_vma_policy(vma, addr, 0, &ilx);
> > page = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
> > - &page_allocated);
> > + &page_allocated, false);
> > mpol_cond_put(mpol);
> >
> > if (page_allocated)
> > @@ -654,7 +666,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> > /* Ok, do the async read-ahead now */
> > page = __read_swap_cache_async(
> > swp_entry(swp_type(entry), offset),
> > - gfp_mask, mpol, ilx, &page_allocated);
> > + gfp_mask, mpol, ilx, &page_allocated, false);
> > if (!page)
> > continue;
> > if (page_allocated) {
> > @@ -672,7 +684,7 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> > skip:
> > /* The page was likely read above, so no need for plugging here */
> > page = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
> > - &page_allocated);
> > + &page_allocated, false);
> > if (unlikely(page_allocated))
> > swap_readpage(page, false, NULL);
> > return page;
> > @@ -827,7 +839,7 @@ static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> > pte_unmap(pte);
> > pte = NULL;
> > page = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
> > - &page_allocated);
> > + &page_allocated, false);
> > if (!page)
> > continue;
> > if (page_allocated) {
> > @@ -847,7 +859,7 @@ static struct page *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
> > skip:
> > /* The page was likely read above, so no need for plugging here */
> > page = __read_swap_cache_async(targ_entry, gfp_mask, mpol, targ_ilx,
> > - &page_allocated);
> > + &page_allocated, false);
> > if (unlikely(page_allocated))
> > swap_readpage(page, false, NULL);
> > return page;
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index 4bdb2d83bb0d..f323e45cbdc7 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -35,6 +35,7 @@
> > #include <linux/writeback.h>
> > #include <linux/pagemap.h>
> > #include <linux/workqueue.h>
> > +#include <linux/list_lru.h>
> >
> > #include "swap.h"
> > #include "internal.h"
> > @@ -174,8 +175,8 @@ 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;
> > };
> >
> > /*
> > @@ -291,15 +292,46 @@ static void zswap_update_total_size(void)
> > zswap_pool_total_size = total;
> > }
> >
> > +/* should be called under RCU */
>
> nit: probably WARN_ON_ONCE(!rcu_read_lock_held()) or
> RCU_LOCKDEP_WARN(!rcu_read_lock_held()) in the function body is
> better?
>
> > +#ifdef CONFIG_MEMCG
> > +static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry)
> > +{
> > + return entry->objcg ? obj_cgroup_memcg(entry->objcg) : NULL;
> > +}
> > +#else
> > +static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry)
> > +{
> > + return NULL;
> > +}
> > +#endif
> > +
> > +static inline int entry_to_nid(struct zswap_entry *entry)
> > +{
> > + return page_to_nid(virt_to_page(entry));
> > +}
> > +
> > +void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg)
> > +{
> > + struct zswap_pool *pool;
> > +
> > + /* lock out zswap pools list modification */
> > + spin_lock(&zswap_pools_lock);
> > + list_for_each_entry(pool, &zswap_pools, list) {
> > + if (pool->next_shrink == memcg)
> > + pool->next_shrink = mem_cgroup_iter(NULL, pool->next_shrink, NULL);
> > + }
> > + spin_unlock(&zswap_pools_lock);
> > +}
> > +
> > /*********************************
> > * zswap entry functions
> > **********************************/
> > static struct kmem_cache *zswap_entry_cache;
> >
> > -static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
> > +static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp, int nid)
> > {
> > struct zswap_entry *entry;
> > - entry = kmem_cache_alloc(zswap_entry_cache, gfp);
> > + entry = kmem_cache_alloc_node(zswap_entry_cache, gfp, nid);
> > if (!entry)
> > return NULL;
> > entry->refcount = 1;
> > @@ -312,6 +344,61 @@ static void zswap_entry_cache_free(struct zswap_entry *entry)
> > kmem_cache_free(zswap_entry_cache, entry);
> > }
> >
> > +/*********************************
> > +* lru functions
> > +**********************************/
> > +static void zswap_lru_add(struct list_lru *list_lru, struct zswap_entry *entry)
> > +{
> > + int nid = entry_to_nid(entry);
> > + struct mem_cgroup *memcg;
> > +
> > + /*
> > + * Note that it is safe to use rcu_read_lock() here, even in the face of
> > + * concurrent memcg offlining. Thanks to the memcg->kmemcg_id indirection
> > + * used in list_lru lookup, only two scenarios are possible:
> > + *
> > + * 1. list_lru_add() is called before memcg->kmemcg_id is updated. The
> > + * new entry will be reparented to memcg's parent's list_lru.
> > + * 2. list_lru_add() is called after memcg->kmemcg_id is updated. The
> > + * new entry will be added directly to memcg's parent's list_lru.
> > + *
> > + * Similar reasoning holds for list_lru_del() and list_lru_putback().
> > + */
> > + rcu_read_lock();
> > + memcg = mem_cgroup_from_entry(entry);
> > + /* will always succeed */
> > + list_lru_add(list_lru, &entry->lru, nid, memcg);
> > + rcu_read_unlock();
> > +}
> > +
> > +static void zswap_lru_del(struct list_lru *list_lru, struct zswap_entry *entry)
> > +{
> > + int nid = entry_to_nid(entry);
> > + struct mem_cgroup *memcg;
> > +
> > + rcu_read_lock();
> > + memcg = mem_cgroup_from_entry(entry);
> > + /* will always succeed */
> > + list_lru_del(list_lru, &entry->lru, nid, memcg);
> > + rcu_read_unlock();
> > +}
> > +
> > +static void zswap_lru_putback(struct list_lru *list_lru,
> > + struct zswap_entry *entry)
> > +{
> > + int nid = entry_to_nid(entry);
> > + spinlock_t *lock = &list_lru->node[nid].lock;
> > + struct mem_cgroup *memcg;
> > +
> > + rcu_read_lock();
> > + memcg = mem_cgroup_from_entry(entry);
> > + spin_lock(lock);
> > + /* we cannot use list_lru_add here, because it increments node's lru count */
> > + list_lru_putback(list_lru, &entry->lru, nid, memcg);
> > + spin_unlock(lock);
> > + rcu_read_unlock();
> > +}
> > +
> > /*********************************
> > * rbtree functions
> > **********************************/
> > @@ -396,9 +483,7 @@ static void zswap_free_entry(struct zswap_entry *entry)
> > 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);
> > }
> > @@ -632,21 +717,15 @@ static void zswap_invalidate_entry(struct zswap_tree *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 list_lru_one *l,
> > + spinlock_t *lock, void *arg)
> > {
> > - struct zswap_entry *entry;
> > + struct zswap_entry *entry = container_of(item, struct zswap_entry, lru);
> > struct zswap_tree *tree;
> > pgoff_t swpoffset;
> > - int ret;
> > + enum lru_status ret = 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 = 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 again
> > @@ -654,28 +733,32 @@ static int zswap_reclaim_entry(struct zswap_pool *pool)
> > */
> > swpoffset = swp_offset(entry->swpentry);
> > tree = zswap_trees[swp_type(entry->swpentry)];
> > - spin_unlock(&pool->lru_lock);
> > + list_lru_isolate(l, item);
> > + /*
> > + * It's safe to drop the lock here because we return either
> > + * LRU_REMOVED_RETRY or LRU_RETRY.
> > + */
> > + spin_unlock(lock);
> >
> > /* Check for invalidate() race */
> > spin_lock(&tree->lock);
> > - if (entry != zswap_rb_search(&tree->rbroot, swpoffset)) {
> > - ret = -EAGAIN;
> > + if (entry != zswap_rb_search(&tree->rbroot, swpoffset))
> > goto unlock;
> > - }
> > +
> > /* Hold a reference to prevent a free during writeback */
> > zswap_entry_get(entry);
> > spin_unlock(&tree->lock);
> >
> > - ret = zswap_writeback_entry(entry, tree);
> > + writeback_result = 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++;
> > + zswap_lru_putback(&entry->pool->list_lru, entry);
> > + ret = LRU_RETRY;
> > goto put_unlock;
> > }
> > + zswap_written_back_pages++;
> >
> > /*
> > * Writeback started successfully, the page now belongs to the
> > @@ -689,27 +772,93 @@ static int zswap_reclaim_entry(struct zswap_pool *pool)
> > 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 = 0;
> > +
> > + /*
> > + * Skip zombies because their LRUs are reparented and we would be
> > + * reclaiming from the parent instead of the dead memcg.
> > + */
> > + if (memcg && !mem_cgroup_online(memcg))
> > + return -ENOENT;
> > +
> > + pool = zswap_pool_current_get();
> > + if (!pool)
> > + return -EINVAL;
> > +
> > + for_each_node_state(nid, N_NORMAL_MEMORY) {
> > + unsigned long nr_to_walk = 1;
> > +
> > + shrunk += list_lru_walk_one(&pool->list_lru, nid, memcg,
> > + &shrink_memcg_cb, NULL, &nr_to_walk);
> > + }
> > + zswap_pool_put(pool);
> > + return shrunk ? 0 : -EAGAIN;
> > }
> >
> > static void shrink_worker(struct work_struct *w)
> > {
> > struct zswap_pool *pool = container_of(w, typeof(*pool),
> > shrink_work);
> > + struct mem_cgroup *memcg;
> > int ret, failures = 0;
> >
> > + /* global reclaim will select cgroup in a round-robin fashion. */
> > do {
> > - ret = zswap_reclaim_entry(pool);
> > - if (ret) {
> > - zswap_reject_reclaim_fail++;
> > - if (ret != -EAGAIN)
> > + spin_lock(&zswap_pools_lock);
> > + pool->next_shrink = mem_cgroup_iter(NULL, pool->next_shrink, NULL);
> > + memcg = pool->next_shrink;
> > +
> > + /*
> > + * We need to retry if we have gone through a full round trip, or if we
> > + * got an offline memcg (or else we risk undoing the effect of the
> > + * zswap memcg offlining cleanup callback). This is not catastrophic
> > + * per se, but it will keep the now offlined memcg hostage for a while.
> > + *
> > + * Note that if we got an online memcg, we will keep the extra
> > + * reference in case the original reference obtained by mem_cgroup_iter
> > + * is dropped by the zswap memcg offlining callback, ensuring that the
> > + * memcg is not killed when we are reclaiming.
> > + */
> > + if (!memcg) {
> > + spin_unlock(&zswap_pools_lock);
> > + if (++failures == MAX_RECLAIM_RETRIES)
> > break;
> > +
> > + goto resched;
> > + }
> > +
> > + if (!mem_cgroup_online(memcg)) {
> > + /* drop the reference from mem_cgroup_iter() */
> > + mem_cgroup_put(memcg);
>
> Probably better to use mem_cgroup_iter_break() here?

mem_cgroup_iter_break(NULL, memcg) seems to perform the same thing, right?

>
> Also, I don't see mem_cgroup_tryget_online() being used here (where I
> expected it to be used), did I miss it?

Oh shoot yeah that was a typo - it should be
mem_cgroup_tryget_online(). Let me send a fix to that.

>
> > + pool->next_shrink = NULL;
> > + spin_unlock(&zswap_pools_lock);
> > +
> > if (++failures == MAX_RECLAIM_RETRIES)
> > break;
> > +
> > + goto resched;
> > }
> > + spin_unlock(&zswap_pools_lock);
> > +
> > + ret = shrink_memcg(memcg);
>
> We just checked for online-ness above, and then shrink_memcg() checks
> it again. Is this intentional?

Hmm these two checks are for two different purposes. The check above
is mainly to prevent accidentally undoing the offline cleanup callback
during memcg selection step. Inside shrink_memcg(), we check
onlineness again to prevent reclaiming from offlined memcgs - which in
effect will trigger the reclaim of the parent's memcg.

>
> > + /* drop the extra reference */
>
> Where does the extra reference come from?

The extra reference is from mem_cgroup_tryget_online(). We get two
references in the dance above - one from mem_cgroup_iter() (which can
be dropped) and one extra from mem_cgroup_tryget_online(). I kept the
second one in case the first one was dropped by the zswap memcg
offlining callback, but after reclaiming it is safe to just drop it.

>
> > + mem_cgroup_put(memcg);
> > +
> > + if (ret == -EINVAL)
> > + break;
> > + if (ret && ++failures == MAX_RECLAIM_RETRIES)
> > + break;
> > +
> > +resched:
> > cond_resched();
> > } while (!zswap_can_accept());
> > - zswap_pool_put(pool);
> > }
> >
> > static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> > @@ -767,8 +916,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> > */
> > kref_init(&pool->kref);
> > INIT_LIST_HEAD(&pool->list);
> > - INIT_LIST_HEAD(&pool->lru);
> > - spin_lock_init(&pool->lru_lock);
> > + list_lru_init_memcg(&pool->list_lru, NULL);
> > INIT_WORK(&pool->shrink_work, shrink_worker);
> >
> > zswap_pool_debug("created", pool);
> > @@ -834,6 +982,13 @@ static void zswap_pool_destroy(struct zswap_pool *pool)
> >
> > cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
> > free_percpu(pool->acomp_ctx);
> > + list_lru_destroy(&pool->list_lru);
> > +
> > + spin_lock(&zswap_pools_lock);
> > + mem_cgroup_put(pool->next_shrink);
> > + pool->next_shrink = NULL;
> > + spin_unlock(&zswap_pools_lock);
> > +
> > for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
> > zpool_destroy_pool(pool->zpools[i]);
> > kfree(pool);
> > @@ -1081,7 +1236,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
> > /* try to allocate swap cache page */
> > mpol = get_task_policy(current);
> > page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
> > - NO_INTERLEAVE_INDEX, &page_was_allocated);
> > + NO_INTERLEAVE_INDEX, &page_was_allocated, true);
> > if (!page) {
> > ret = -ENOMEM;
> > goto fail;
> > @@ -1152,7 +1307,6 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
> > /* start writeback */
> > __swap_writepage(page, &wbc);
> > put_page(page);
> > - zswap_written_back_pages++;
> >
> > return ret;
> >
> > @@ -1209,6 +1363,7 @@ bool zswap_store(struct folio *folio)
> > struct scatterlist input, output;
> > struct crypto_acomp_ctx *acomp_ctx;
> > struct obj_cgroup *objcg = NULL;
> > + struct mem_cgroup *memcg = NULL;
> > struct zswap_pool *pool;
> > struct zpool *zpool;
> > unsigned int dlen = PAGE_SIZE;
> > @@ -1240,15 +1395,15 @@ bool zswap_store(struct folio *folio)
> > zswap_invalidate_entry(tree, dupentry);
> > }
> > spin_unlock(&tree->lock);
> > -
> > - /*
> > - * XXX: zswap reclaim does not work with cgroups yet. Without a
> > - * cgroup-aware entry LRU, we will push out entries system-wide based on
> > - * local cgroup limits.
> > - */
> > objcg = get_obj_cgroup_from_folio(folio);
> > - if (objcg && !obj_cgroup_may_zswap(objcg))
> > - goto reject;
> > + if (objcg && !obj_cgroup_may_zswap(objcg)) {
> > + memcg = get_mem_cgroup_from_objcg(objcg);
>
> Do we need a reference here? IIUC, this is folio_memcg() and the folio
> is locked, so folio_memcg() should remain stable, no?

Hmmm obj_cgroup_may_zswap() also holds a reference to the objcg's
memcg, so I just followed the patterns to be safe.

>
> Same for the call below.
>
> > + if (shrink_memcg(memcg)) {
> > + mem_cgroup_put(memcg);
> > + goto reject;
> > + }
> > + mem_cgroup_put(memcg);
> > + }
> >
> > /* reclaim space if needed */
> > if (zswap_is_full()) {
> > @@ -1265,7 +1420,7 @@ bool zswap_store(struct folio *folio)
> > }
> >
> > /* allocate entry */
> > - entry = zswap_entry_cache_alloc(GFP_KERNEL);
> > + entry = zswap_entry_cache_alloc(GFP_KERNEL, page_to_nid(page));
> > if (!entry) {
> > zswap_reject_kmemcache_fail++;
> > goto reject;
> > @@ -1292,6 +1447,15 @@ bool zswap_store(struct folio *folio)
> > if (!entry->pool)
> > goto freepage;
> >
> > + if (objcg) {
> > + memcg = get_mem_cgroup_from_objcg(objcg);
> > + if (memcg_list_lru_alloc(memcg, &entry->pool->list_lru, GFP_KERNEL)) {
> > + mem_cgroup_put(memcg);
> > + goto put_pool;
> > + }
> > + mem_cgroup_put(memcg);
> > + }
> > +
> > /* compress */
> > acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> >
> > @@ -1370,9 +1534,8 @@ 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(&entry->pool->list_lru, entry);
> > }
> > spin_unlock(&tree->lock);
> >
> > @@ -1385,6 +1548,7 @@ bool zswap_store(struct folio *folio)
> >
> > put_dstmem:
> > mutex_unlock(acomp_ctx->mutex);
> > +put_pool:
> > zswap_pool_put(entry->pool);
> > freepage:
> > zswap_entry_cache_free(entry);
> > @@ -1479,9 +1643,8 @@ 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);
> > --
> > 2.34.1