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Thu, 18 Sep 2025 20:49:52 -0700 (PDT) From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH 2/4] mm: thp: introduce folio_split_queue_lock and its variants Date: Fri, 19 Sep 2025 11:46:33 +0800 Message-ID: X-Mailer: git-send-email 2.48.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Muchun Song In future memcg removal, the binding between a folio and a memcg may change, making the split lock within the memcg unstable when held. A new approach is required to reparent the split queue to its parent. This patch starts introducing a unified way to acquire the split lock for future work. It's a code-only refactoring with no functional changes. Signed-off-by: Muchun Song Acked-by: Johannes Weiner Signed-off-by: Qi Zheng Acked-by: David Hildenbrand Acked-by: Shakeel Butt --- include/linux/memcontrol.h | 10 +++++ mm/huge_memory.c | 89 ++++++++++++++++++++++++++------------ 2 files changed, 71 insertions(+), 28 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 16fe0306e50ea..99876af13c315 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1662,6 +1662,11 @@ int alloc_shrinker_info(struct mem_cgroup *memcg); void free_shrinker_info(struct mem_cgroup *memcg); void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id); void reparent_shrinker_deferred(struct mem_cgroup *memcg); + +static inline int shrinker_id(struct shrinker *shrinker) +{ + return shrinker->id; +} #else #define mem_cgroup_sockets_enabled 0 =20 @@ -1693,6 +1698,11 @@ static inline void set_shrinker_bit(struct mem_cgrou= p *memcg, int nid, int shrinker_id) { } + +static inline int shrinker_id(struct shrinker *shrinker) +{ + return -1; +} #endif =20 #ifdef CONFIG_MEMCG diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 582628ddf3f33..d34516a22f5bb 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1078,26 +1078,62 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_s= truct *vma) =20 #ifdef CONFIG_MEMCG static inline -struct deferred_split *get_deferred_split_queue(struct folio *folio) +struct mem_cgroup *folio_split_queue_memcg(struct folio *folio, + struct deferred_split *queue) { - struct mem_cgroup *memcg =3D folio_memcg(folio); - struct pglist_data *pgdat =3D NODE_DATA(folio_nid(folio)); - - if (memcg) - return &memcg->deferred_split_queue; - else - return &pgdat->deferred_split_queue; + if (mem_cgroup_disabled()) + return NULL; + if (&NODE_DATA(folio_nid(folio))->deferred_split_queue =3D=3D queue) + return NULL; + return container_of(queue, struct mem_cgroup, deferred_split_queue); } #else static inline -struct deferred_split *get_deferred_split_queue(struct folio *folio) +struct mem_cgroup *folio_split_queue_memcg(struct folio *folio, + struct deferred_split *queue) { - struct pglist_data *pgdat =3D NODE_DATA(folio_nid(folio)); - - return &pgdat->deferred_split_queue; + return NULL; } #endif =20 +static struct deferred_split *folio_split_queue_lock(struct folio *folio) +{ + struct mem_cgroup *memcg; + struct deferred_split *queue; + + memcg =3D folio_memcg(folio); + queue =3D memcg ? &memcg->deferred_split_queue : + &NODE_DATA(folio_nid(folio))->deferred_split_queue; + spin_lock(&queue->split_queue_lock); + + return queue; +} + +static struct deferred_split * +folio_split_queue_lock_irqsave(struct folio *folio, unsigned long *flags) +{ + struct mem_cgroup *memcg; + struct deferred_split *queue; + + memcg =3D folio_memcg(folio); + queue =3D memcg ? &memcg->deferred_split_queue : + &NODE_DATA(folio_nid(folio))->deferred_split_queue; + spin_lock_irqsave(&queue->split_queue_lock, *flags); + + return queue; +} + +static inline void split_queue_unlock(struct deferred_split *queue) +{ + spin_unlock(&queue->split_queue_lock); +} + +static inline void split_queue_unlock_irqrestore(struct deferred_split *qu= eue, + unsigned long flags) +{ + spin_unlock_irqrestore(&queue->split_queue_lock, flags); +} + static inline bool is_transparent_hugepage(const struct folio *folio) { if (!folio_test_large(folio)) @@ -3579,7 +3615,7 @@ static int __folio_split(struct folio *folio, unsigne= d int new_order, struct page *split_at, struct page *lock_at, struct list_head *list, bool uniform_split) { - struct deferred_split *ds_queue =3D get_deferred_split_queue(folio); + struct deferred_split *ds_queue; XA_STATE(xas, &folio->mapping->i_pages, folio->index); struct folio *end_folio =3D folio_next(folio); bool is_anon =3D folio_test_anon(folio); @@ -3718,7 +3754,7 @@ static int __folio_split(struct folio *folio, unsigne= d int new_order, } =20 /* Prevent deferred_split_scan() touching ->_refcount */ - spin_lock(&ds_queue->split_queue_lock); + ds_queue =3D folio_split_queue_lock(folio); if (folio_ref_freeze(folio, 1 + extra_pins)) { struct swap_cluster_info *ci =3D NULL; struct lruvec *lruvec; @@ -3740,7 +3776,7 @@ static int __folio_split(struct folio *folio, unsigne= d int new_order, */ list_del_init(&folio->_deferred_list); } - spin_unlock(&ds_queue->split_queue_lock); + split_queue_unlock(ds_queue); if (mapping) { int nr =3D folio_nr_pages(folio); =20 @@ -3835,7 +3871,7 @@ static int __folio_split(struct folio *folio, unsigne= d int new_order, if (ci) swap_cluster_unlock(ci); } else { - spin_unlock(&ds_queue->split_queue_lock); + split_queue_unlock(ds_queue); ret =3D -EAGAIN; } fail: @@ -4016,8 +4052,7 @@ bool __folio_unqueue_deferred_split(struct folio *fol= io) WARN_ON_ONCE(folio_ref_count(folio)); WARN_ON_ONCE(!mem_cgroup_disabled() && !folio_memcg_charged(folio)); =20 - ds_queue =3D get_deferred_split_queue(folio); - spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + ds_queue =3D folio_split_queue_lock_irqsave(folio, &flags); if (!list_empty(&folio->_deferred_list)) { ds_queue->split_queue_len--; if (folio_test_partially_mapped(folio)) { @@ -4028,7 +4063,7 @@ bool __folio_unqueue_deferred_split(struct folio *fol= io) list_del_init(&folio->_deferred_list); unqueued =3D true; } - spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); + split_queue_unlock_irqrestore(ds_queue, flags); =20 return unqueued; /* useful for debug warnings */ } @@ -4036,10 +4071,7 @@ bool __folio_unqueue_deferred_split(struct folio *fo= lio) /* partially_mapped=3Dfalse won't clear PG_partially_mapped folio flag */ void deferred_split_folio(struct folio *folio, bool partially_mapped) { - struct deferred_split *ds_queue =3D get_deferred_split_queue(folio); -#ifdef CONFIG_MEMCG - struct mem_cgroup *memcg =3D folio_memcg(folio); -#endif + struct deferred_split *ds_queue; unsigned long flags; =20 /* @@ -4062,7 +4094,7 @@ void deferred_split_folio(struct folio *folio, bool p= artially_mapped) if (folio_test_swapcache(folio)) return; =20 - spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + ds_queue =3D folio_split_queue_lock_irqsave(folio, &flags); if (partially_mapped) { if (!folio_test_partially_mapped(folio)) { folio_set_partially_mapped(folio); @@ -4077,15 +4109,16 @@ void deferred_split_folio(struct folio *folio, bool= partially_mapped) VM_WARN_ON_FOLIO(folio_test_partially_mapped(folio), folio); } if (list_empty(&folio->_deferred_list)) { + struct mem_cgroup *memcg; + + memcg =3D folio_split_queue_memcg(folio, ds_queue); list_add_tail(&folio->_deferred_list, &ds_queue->split_queue); ds_queue->split_queue_len++; -#ifdef CONFIG_MEMCG if (memcg) set_shrinker_bit(memcg, folio_nid(folio), - deferred_split_shrinker->id); -#endif + shrinker_id(deferred_split_shrinker)); } - spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); + split_queue_unlock_irqrestore(ds_queue, flags); } =20 static unsigned long deferred_split_count(struct shrinker *shrink, --=20 2.20.1