From nobody Mon Feb 9 15:26:45 2026 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 24411283FDD for ; Sun, 21 Dec 2025 23:36:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766360218; cv=none; b=OAy5hnZDSYysKpVNoxFeLxdBJFWNWS/KWDhv5ZxnhfuINmVR+is1TzmzK7a+IOifqB265vXcKH0U7Eca4wjqM+SDcouJ97krfblsE+ktH9XkrcV1Dm7X+yTbxWQkBWXvVaw31m6jliS6MDf9vfhiw8f7m2GQ/0ZAV6yN9hBveEw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766360218; c=relaxed/simple; bh=TH8d2yyXKa4fMd0WI4nPJ0bzAgbIns0ypw8/ovvAOfM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ZmOr9wrMICM0hhDM5pDVScFTo4vE59LNiee7q0yz01YFNWVtQ+yJr/bhJMwHhh/ZFFevaQFzt1C7i9Hc3rKSBNUv/ykMypqiwqOZHtGAYuDqlOg9TVtuGv5AT61bbLVigdi26iaJdWL7FKfptpRRSY+K7fInUSET8TwwvA1IMCM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--bingjiao.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=aJaErCQG; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--bingjiao.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="aJaErCQG" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-b99763210e5so6945449a12.3 for ; Sun, 21 Dec 2025 15:36:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1766360216; x=1766965016; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=4GfhhMoWYFTh/aN/kwrLJXHldk5+UtwhObh4bR+INB4=; b=aJaErCQGfQUOk6wMvmLvIIMGxSp+3eaKlUbdKiv2Pe5fgHmS11NP+tGw/Wr7fY7pmJ UU3n3hPnXo4jL3dWwF821Fo99YmbuMQQUkcaoWD97ooXi7LIc586fWvrh5EqHyS/fH7Z uPqGHVjizbslTG85ZTQunVdgtFvWAZAZNBMkloGPCUULrjxHVG67XA9OetrsOJ1/XyT5 rDJfrnADGMX0zsfJBqu9atLaSpBc/AjF5V9yuQQhom51XM9pblp33tXKhbKHxFXjLEzC i92D60U+2K6De7hg1KRDxVfBERgkror0Dk7XEeD6QcWF/GER1DBHm7kV+obcJr/DPo+K Brxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1766360216; x=1766965016; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=4GfhhMoWYFTh/aN/kwrLJXHldk5+UtwhObh4bR+INB4=; b=JkuPP9ceE1h7TeexJxo73ZaoLKmNf4y5WBqnR3gPOGiUOwOBRNcxb4uqOqco2rgxZo W/ZSEiRREXi3h6fJvZL8CWYoJAph4QfBY7nGb63SlZFh0EUSC7QaUoaP5F5O7Gq7H3KF Zjs33JvSicPrah+dHsOR5I5RTrRh09XazmNbMjYTO2PwWPdScJcltL2Z9vzPq+P9dVk+ UvG6UW3bf5hd9KNk+t+KHdWXzCrcbx+n8Q9Zyg68RBS3WFEmsniAJoUzDoFHAoUpgQ8e Wlb53cHiG9yugMH9smDas8wdrsVWObjoP0ulUuWX/KeX4a3T+cBbe9xMA+vTz6o0bvqZ So6Q== X-Gm-Message-State: AOJu0YxFr+kUv7IzTZQOPYss54pdwFoOtfSUZrYoUMfbAkul078R0Ec8 wluaWXYj9l0o1GfGPiuM2ngg04Z6Aqh6YLESsQIA5Qj0TKUBmLQYgDTIGcNjKfKuA1PPG7LA6sj rqojGK8uzRtHVwg== X-Google-Smtp-Source: AGHT+IEicLxazx7S6uu1698T5FhlbmHzMdzgeAbcuTNEEaAVkEM1v1fpFPWcA/uiQi7D96w3YBVKbgPaJ+Ktsg== X-Received: from dyboo7.prod.google.com ([2002:a05:7301:1e87:b0:2ac:36d5:fc65]) (user=bingjiao job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7301:d89:b0:2ac:2263:dcc0 with SMTP id 5a478bee46e88-2b05ec19181mr11168511eec.19.1766360216254; Sun, 21 Dec 2025 15:36:56 -0800 (PST) Date: Sun, 21 Dec 2025 23:36:34 +0000 In-Reply-To: <20251221233635.3761887-1-bingjiao@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251220061022.2726028-1-bingjiao@google.com> <20251221233635.3761887-1-bingjiao@google.com> X-Mailer: git-send-email 2.52.0.351.gbe84eed79e-goog Message-ID: <20251221233635.3761887-2-bingjiao@google.com> Subject: [PATCH v2 1/2] mm/vmscan: respect mems_effective in demote_folio_list() From: Bing Jiao To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, akpm@linux-foundation.org, gourry@gourry.net, longman@redhat.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, tj@kernel.org, mkoutny@suse.com, david@kernel.org, zhengqi.arch@bytedance.com, lorenzo.stoakes@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, cgroups@vger.kernel.org, Bing Jiao Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Commit 7d709f49babc ("vmscan,cgroup: apply mems_effective to reclaim") introduces the cpuset.mems_effective check and applies it to can_demote(). However, it does not apply this check in demote_folio_list(). This omission leads to situations where pages are demoted to nodes that are explicitly excluded from the task's cpuset.mems. The impact is two-fold: 1. Resource Isolation: This bug breaks resource isolation provided by cpuset.mems. It allows pages to be demoted to nodes that are dedicated to other tasks or are intended for hot-unplugging. 2. Performance Issue: In multi-tier systems, users use cpuset.mems to bind tasks to different performed-far tiers (e.g., avoiding the slowest tiers for latency-sensitive data). This bug can cause unexpected latency spikes if pages are demoted to the farthest nodes. To address the bug, implement a new function mem_cgroup_filter_mems_allowed() to filter out nodes that are not set in mems_effective, and update demote_folio_list() to utilize this filtering logic. This ensures that demotions target respect task's memory placement constraints. Fixes: 7d709f49babc ("vmscan,cgroup: apply mems_effective to reclaim") Signed-off-by: Bing Jiao --- include/linux/cpuset.h | 6 ++++++ include/linux/memcontrol.h | 7 +++++++ kernel/cgroup/cpuset.c | 18 ++++++++++++++++++ mm/memcontrol.c | 6 ++++++ mm/vmscan.c | 13 ++++++++++--- 5 files changed, 47 insertions(+), 3 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index a98d3330385c..0e94548e2d24 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -175,6 +175,7 @@ static inline void set_mems_allowed(nodemask_t nodemask) } =20 extern bool cpuset_node_allowed(struct cgroup *cgroup, int nid); +extern void cpuset_node_filter_allowed(struct cgroup *cgroup, nodemask_t *= mask); #else /* !CONFIG_CPUSETS */ =20 static inline bool cpusets_enabled(void) { return false; } @@ -305,6 +306,11 @@ static inline bool cpuset_node_allowed(struct cgroup *= cgroup, int nid) { return true; } + +static inline void cpuset_node_filter_allowed(struct cgroup *cgroup, + nodemask_t *mask) +{ +} #endif /* !CONFIG_CPUSETS */ =20 #endif /* _LINUX_CPUSET_H */ diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index fd400082313a..7cfd71c57caa 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1742,6 +1742,8 @@ static inline void count_objcg_events(struct obj_cgro= up *objcg, =20 bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid); =20 +void mem_cgroup_filter_mems_allowed(struct mem_cgroup *memcg, nodemask_t *= mask); + void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg); =20 static inline bool memcg_is_dying(struct mem_cgroup *memcg) @@ -1816,6 +1818,11 @@ static inline bool mem_cgroup_node_allowed(struct me= m_cgroup *memcg, int nid) return true; } =20 +static inline bool mem_cgroup_filter_mems_allowed(struct mem_cgroup *memcg, + nodemask_t *mask) +{ +} + static inline void mem_cgroup_show_protected_memory(struct mem_cgroup *mem= cg) { } diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 6e6eb09b8db6..2925bd6bca91 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -4452,6 +4452,24 @@ bool cpuset_node_allowed(struct cgroup *cgroup, int = nid) return allowed; } =20 +void cpuset_node_filter_allowed(struct cgroup *cgroup, nodemask_t *mask) +{ + struct cgroup_subsys_state *css; + struct cpuset *cs; + + if (!cpuset_v2()) + return; + + css =3D cgroup_get_e_css(cgroup, &cpuset_cgrp_subsys); + if (!css) + return; + + /* Follows the same assumption in cpuset_node_allowed() */ + cs =3D container_of(css, struct cpuset, css); + nodes_and(*mask, *mask, cs->effective_mems); + css_put(css); +} + /** * cpuset_spread_node() - On which node to begin search for a page * @rotor: round robin rotor diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 75fc22a33b28..f414653867de 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5602,6 +5602,12 @@ bool mem_cgroup_node_allowed(struct mem_cgroup *memc= g, int nid) return memcg ? cpuset_node_allowed(memcg->css.cgroup, nid) : true; } =20 +void mem_cgroup_filter_mems_allowed(struct mem_cgroup *memcg, nodemask_t *= mask) +{ + if (memcg) + cpuset_node_filter_allowed(memcg->css.cgroup, mask); +} + void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg) { if (mem_cgroup_disabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) diff --git a/mm/vmscan.c b/mm/vmscan.c index 453d654727c1..4d23c491e914 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1018,7 +1018,8 @@ static struct folio *alloc_demote_folio(struct folio = *src, * Folios which are not demoted are left on @demote_folios. */ static unsigned int demote_folio_list(struct list_head *demote_folios, - struct pglist_data *pgdat) + struct pglist_data *pgdat, + struct mem_cgroup *memcg) { int target_nid =3D next_demotion_node(pgdat->node_id); unsigned int nr_succeeded; @@ -1032,7 +1033,6 @@ static unsigned int demote_folio_list(struct list_hea= d *demote_folios, */ .gfp_mask =3D (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOMEMALLOC | GFP_NOWAIT, - .nid =3D target_nid, .nmask =3D &allowed_mask, .reason =3D MR_DEMOTION, }; @@ -1044,6 +1044,13 @@ static unsigned int demote_folio_list(struct list_he= ad *demote_folios, return 0; =20 node_get_allowed_targets(pgdat, &allowed_mask); + /* Filter the given nmask based on cpuset.mems.allowed */ + mem_cgroup_filter_mems_allowed(memcg, &allowed_mask); + if (nodes_empty(allowed_mask)) + return 0; + if (!node_isset(target_nid, allowed_mask)) + target_nid =3D node_random(&allowed_mask); + mtc.nid =3D target_nid; =20 /* Demotion ignores all cpuset and mempolicy settings */ migrate_pages(demote_folios, alloc_demote_folio, NULL, @@ -1565,7 +1572,7 @@ static unsigned int shrink_folio_list(struct list_hea= d *folio_list, /* 'folio_list' is always empty here */ =20 /* Migrate folios selected for demotion */ - nr_demoted =3D demote_folio_list(&demote_folios, pgdat); + nr_demoted =3D demote_folio_list(&demote_folios, pgdat, memcg); nr_reclaimed +=3D nr_demoted; stat->nr_demoted +=3D nr_demoted; /* Folios that could not be demoted are still in @demote_folios */ --=20 2.52.0.351.gbe84eed79e-goog