From nobody Thu Dec 18 23:15:16 2025 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 498652D63EF for ; Fri, 3 Oct 2025 16:54:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759510452; cv=none; b=ILn129m/r40IKtas02ReoamCBqBEz9ot5bNRGlRJMWNmO1r/fEGU+A0Q6xnNIQn6oCe3ADNISqypxINp60uPtz2iMxwwLUZ9ScZiEueNPsae42+LKWKDgwyjBdVs4GsjJjhPn8yGzSsT/0ekjY7vyMxYEWT9kuVyNi5yU7ek4JM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759510452; c=relaxed/simple; bh=MwpxNOjOU/W2lfsYh1DnL+WdrFKsA/2BkGojiQShrJs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=agiMLG9VhTtYCJlVMNt0nFEiSvPrhxPzw/Y5Vu6njJQ1fiZfOEB5CDCRr0DORCAZR+ajwX/OmIKZGrVqYWuZsmd54ZWTj8Qt2DvhIhntIfLu6rkAOqdey34x0aXtpuUPdf41nGmKVpt8NInOHe/8yaUid0bB7auAG70/4h4TAtI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=sHZI/SdY; arc=none smtp.client-ip=95.215.58.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="sHZI/SdY" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1759510447; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Jx/up15hgoocFMTTmoEqLtWBcwNy2yCwXsVyYpG2qec=; b=sHZI/SdYJexk3J7ukbM/EEnC/7bI/bjQrZNFcUYz/sorUAWS6rT/d0Ktx6P1KYiqd+xYze JoTDu7a60Xy/6AiG/ZmFJ2ThTyUb0BPL188CyhbXUCtDYzjQ2km5dueSVGnw/ATv85ayvC 9KkyfS0EKwTfM6ZsKOzt1/DOQNJ4WHo= 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, harry.yoo@oracle.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 v4 2/4] mm: thp: introduce folio_split_queue_lock and its variants Date: Sat, 4 Oct 2025 00:53:16 +0800 Message-ID: <68492101fa51d4bab4ade327354b986c0959250e.1759510072.git.zhengqi.arch@bytedance.com> 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 X-Migadu-Flow: FLOW_OUT 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 Signed-off-by: Qi Zheng Acked-by: Johannes Weiner Reviewed-by: Zi Yan Acked-by: Shakeel Butt Acked-by: David Hildenbrand Reviewed-by: Harry Yoo --- include/linux/memcontrol.h | 10 ++++ mm/huge_memory.c | 119 ++++++++++++++++++++++++++----------- 2 files changed, 94 insertions(+), 35 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 873e510d6f8d9..0b2d4ec79adfe 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1674,6 +1674,11 @@ 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 @@ -1705,6 +1710,11 @@ 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 6db24b3a57005..134666503440d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1076,28 +1076,86 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_s= truct *vma) return pmd; } =20 +static struct deferred_split *split_queue_node(int nid) +{ + struct pglist_data *pgdata =3D NODE_DATA(nid); + + return &pgdata->deferred_split_queue; +} + #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 (mem_cgroup_disabled()) + return NULL; + if (split_queue_node(folio_nid(folio)) =3D=3D queue) + return NULL; + return container_of(queue, struct mem_cgroup, deferred_split_queue); +} =20 - if (memcg) - return &memcg->deferred_split_queue; - else - return &pgdat->deferred_split_queue; +static struct deferred_split *memcg_split_queue(int nid, struct mem_cgroup= *memcg) +{ + return memcg ? &memcg->deferred_split_queue : split_queue_node(nid); } #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 NULL; +} =20 - return &pgdat->deferred_split_queue; +static struct deferred_split *memcg_split_queue(int nid, struct mem_cgroup= *memcg) +{ + return split_queue_node(nid); } #endif =20 +static struct deferred_split *split_queue_lock(int nid, struct mem_cgroup = *memcg) +{ + struct deferred_split *queue; + + queue =3D memcg_split_queue(nid, memcg); + spin_lock(&queue->split_queue_lock); + + return queue; +} + +static struct deferred_split * +split_queue_lock_irqsave(int nid, struct mem_cgroup *memcg, unsigned long = *flags) +{ + struct deferred_split *queue; + + queue =3D memcg_split_queue(nid, memcg); + spin_lock_irqsave(&queue->split_queue_lock, *flags); + + return queue; +} + +static struct deferred_split *folio_split_queue_lock(struct folio *folio) +{ + return split_queue_lock(folio_nid(folio), folio_memcg(folio)); +} + +static struct deferred_split * +folio_split_queue_lock_irqsave(struct folio *folio, unsigned long *flags) +{ + return split_queue_lock_irqsave(folio_nid(folio), folio_memcg(folio), fla= gs); +} + +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 +3637,7 @@ 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 +3776,7 @@ 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 +3798,7 @@ 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 +3893,7 @@ 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 +4074,7 @@ 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 +4085,7 @@ 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 +4093,7 @@ 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 +4116,7 @@ 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 +4131,16 @@ 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, @@ -4128,19 +4183,13 @@ static bool thp_underused(struct folio *folio) static unsigned long deferred_split_scan(struct shrinker *shrink, struct shrink_control *sc) { - struct pglist_data *pgdata =3D NODE_DATA(sc->nid); - struct deferred_split *ds_queue =3D &pgdata->deferred_split_queue; + struct deferred_split *ds_queue; unsigned long flags; LIST_HEAD(list); struct folio *folio, *next, *prev =3D NULL; int split =3D 0, removed =3D 0; =20 -#ifdef CONFIG_MEMCG - if (sc->memcg) - ds_queue =3D &sc->memcg->deferred_split_queue; -#endif - - spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + ds_queue =3D split_queue_lock_irqsave(sc->nid, sc->memcg, &flags); /* Take pin on all head pages to avoid freeing them under us */ list_for_each_entry_safe(folio, next, &ds_queue->split_queue, _deferred_list) { @@ -4159,7 +4208,7 @@ static unsigned long deferred_split_scan(struct shrin= ker *shrink, if (!--sc->nr_to_scan) break; } - spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); + split_queue_unlock_irqrestore(ds_queue, flags); =20 list_for_each_entry_safe(folio, next, &list, _deferred_list) { bool did_split =3D false; --=20 2.20.1