From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6944740F726; Fri, 9 Oct 2026 05:58:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791525517; cv=none; b=KcOfpl5vRWRaOq8gJsfBKCLsjGo1yTZGj6NHhchPIkRJhRrLOJiSxZKrZNutUppUvSmil+qOAW4TfLtrHN3ivPEA2YCnELJcgKqrK7aRU/HiSKRXFNDAZrSnSFoPLMDags3LFnPwtt3eDRLcg/o+yW/6wbsvbHuGLhXohVyNn+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791525517; c=relaxed/simple; bh=HNHwlyulERrNgJq+D/JTK1VNH7fNkfHCHTinFuJj8YI=; h=Date:To:From:Subject:Message-Id; b=mPfiSNmvcnymf5ieUQUjFwB4DQP6dwcJW5lyyz5cuhJXQC3zT4CDO9ToXk8x3gImISIkiPuPzmGzFPSUUAtfwI1jTcNyji4olNio1j6xBoAe/hDiqN8DyKPKar99HAG/ELUoV5y+3LPnMm1XdGH4w5eo9vCuirS5Kx7UQr5c4Gg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=GRDsaloO; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="GRDsaloO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3ED6B1F00893; Fri, 9 Oct 2026 05:58:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791525516; bh=ZwMf04IOolWopGJqfhK2jETxsFhAkPxdUgqADRNfjGk=; h=Date:To:From:Subject; b=GRDsaloOHCdZTbu2lXkmqN0LvLw47z4yoRaXIqpslwfCJ3k/ttss+tcA2xWhjF17h YL0U7FVJUmIKDWFVqyqbXmvJJKKPVtlGJ1vhGSpG8KO6fBIrtKxqzuCoge55aIRW99 opdX+sNu5XQRK1XffPJ7oc8qj2KwMfqo66I8sDGc= Date: Thu, 08 Oct 2026 22:58:35 -0700 To: mm-commits@vger.kernel.org,yuzhao@google.com,yuanchu@google.com,weixugc@google.com,tj@kernel.org,stable@vger.kernel.org,shakeel.butt@linux.dev,roman.gushchin@linux.dev,muchun.song@linux.dev,mhocko@kernel.org,ljs@kernel.org,kasong@tencent.com,hannes@cmpxchg.org,david@kernel.org,chris@chrisdown.name,baohua@kernel.org,axelrasmussen@google.com,chenridong@xiaomi.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-mglru-fix-ineffective-memory-protection-for-non-kswapd-reclaim.patch removed from -mm tree Message-Id: <20261009055836.3ED6B1F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/mglru: fix ineffective memory protection for non-kswapd reclaim has been removed from the -mm tree. Its filename was mm-mglru-fix-ineffective-memory-protection-for-non-kswapd-reclaim.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Ridong Chen Subject: mm/mglru: fix ineffective memory protection for non-kswapd reclaim Date: Mon, 7 Sep 2026 10:54:45 +0800 For MGLRU, memory.min/low is not honored during global proactive reclaim (writing to the root memory.reclaim) and global direct reclaim, because these paths shrink memcgs using stale protection (emin/elow). It can be reproduced as follows: # echo 7 > /sys/kernel/mm/lru_gen/enabled # cd /sys/fs/cgroup # mkdir -p a/b # echo 100M > a/memory.min # echo +memory > a/cgroup.subtree_control # echo 100M > a/b/memory.min # echo $$ > a/b/cgroup.procs # dd if=/dev/zero of=/tmp/testfile bs=1M count=200 # cat a/b/memory.current 222650368 # echo 500M > memory.reclaim -bash: echo: write error: Resource temporarily unavailable # cat a/b/memory.current 6070272 memory.min is 100M, yet reclaim drops a/b down to 6M, breaking the protection. The traditional LRU path is not affected because shrink_node() calls mem_cgroup_calculate_protection() for each memcg it visits during a top-down tree walk. Commit 30d77b7eef01 ("mm/mglru: fix ineffective protection calculation") moved the protection computation into lru_gen_age_node(), which only runs for kswapd. Non-kswapd global reclaim reaches shrink_one() through lru_gen_shrink_node() -> shrink_many() without any protection computation, so emin/elow are whatever a previous kswapd run left behind - or zero if kswapd never ran on this node. Relying on a prior kswapd pass is not correct either: a memcg's emin/elow are derived from its ancestors' memory.min/low settings and from children_min_usage, both of which change over time, so emin/elow go stale even after kswapd has run and must be recomputed at the point of reclaim. Introduce mem_cgroup_calculate_protection_path() which computes emin/elow along the root-to-target path only, by iterating through the cgroup ancestors array top-down. This avoids the full tree traversal that would be needed with mem_cgroup_calculate_protection(), limiting the cost to O(depth) per memcg - typically 3-5 levels. Call it from shrink_one() for the non-kswapd path so that each memcg about to be shrunk has correct protection values. Link: https://lore.kernel.org/20260907025445.1836238-3-ridong.chen@linux.dev Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists") Signed-off-by: Ridong Chen Signed-off-by: Andrew Morton Reviewed-by: Barry Song Reviewed-by: Johannes Weiner Assisted-by: Claude:claude-opus-4-8 Cc: Axel Rasmussen Cc: Chris Down Cc: David Hildenbrand Cc: Kairui Song Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Shakeel Butt Cc: Tejun Heo Cc: Wei Xu Cc: Yuanchu Xie Cc: Yu Zhao Cc: --- include/linux/memcontrol.h | 10 +++++++ mm/memcontrol.c | 45 +++++++++++++++++++++++++++++++++++ mm/vmscan.c | 8 +++++- 3 files changed, 62 insertions(+), 1 deletion(-) --- a/include/linux/memcontrol.h~mm-mglru-fix-ineffective-memory-protection-for-non-kswapd-reclaim +++ a/include/linux/memcontrol.h @@ -1921,6 +1921,16 @@ static inline bool memcg_is_dying(struct } #endif /* CONFIG_MEMCG */ +#if defined(CONFIG_MEMCG) && defined(CONFIG_LRU_GEN) +void mem_cgroup_calculate_protection_path(struct mem_cgroup *root, + struct mem_cgroup *memcg); +#else +static inline void mem_cgroup_calculate_protection_path(struct mem_cgroup *root, + struct mem_cgroup *memcg) +{ +} +#endif + #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP) bool obj_cgroup_may_zswap(struct obj_cgroup *objcg); void obj_cgroup_charge_zswap(struct obj_cgroup *objcg, size_t size); --- a/mm/memcontrol.c~mm-mglru-fix-ineffective-memory-protection-for-non-kswapd-reclaim +++ a/mm/memcontrol.c @@ -5267,6 +5267,51 @@ void mem_cgroup_calculate_protection(str page_counter_calculate_protection(&root->memory, &memcg->memory, recursive_protection); } +#ifdef CONFIG_LRU_GEN +/** + * mem_cgroup_calculate_protection_path - compute protection along a path + * @root: the top ancestor of the sub-tree being checked (NULL for root_mem_cgroup) + * @memcg: the target memory cgroup + * + * Walk the ancestor path from @root down to @memcg and compute the effective + * protection at each level. This is safe for isolated queries because it + * ensures parents are computed before children. + */ +void mem_cgroup_calculate_protection_path(struct mem_cgroup *root, + struct mem_cgroup *memcg) +{ + bool recursive_protection = + cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT; + struct cgroup *cg; + int root_level, i; + + if (mem_cgroup_disabled()) + return; + + if (!root) + root = root_mem_cgroup; + + if (memcg == root) + return; + + root_level = root->css.cgroup->level; + cg = memcg->css.cgroup; + + rcu_read_lock(); + for (i = root_level + 1; i <= cg->level; i++) { + struct mem_cgroup *cur; + + cur = mem_cgroup_from_css(cgroup_css(cg->ancestors[i], + &memory_cgrp_subsys)); + if (cur) + page_counter_calculate_protection(&root->memory, + &cur->memory, + recursive_protection); + } + rcu_read_unlock(); +} +#endif /* CONFIG_LRU_GEN */ + static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg, gfp_t gfp) { --- a/mm/vmscan.c~mm-mglru-fix-ineffective-memory-protection-for-non-kswapd-reclaim +++ a/mm/vmscan.c @@ -5251,7 +5251,13 @@ static int shrink_one(struct lruvec *lru struct mem_cgroup *memcg = lruvec_memcg(lruvec); struct pglist_data *pgdat = lruvec_pgdat(lruvec); - /* lru_gen_age_node() called mem_cgroup_calculate_protection() */ + /* + * For kswapd, mem_cgroup_calculate_protection() has already + * been called during the top-down cgroup traversal. + */ + if (!current_is_kswapd()) + mem_cgroup_calculate_protection_path(NULL, memcg); + if (mem_cgroup_below_min(NULL, memcg)) return MEMCG_LRU_YOUNG; _ Patches currently in -mm which might be from chenridong@xiaomi.com are mm-vmscan-put-rotation-missed-folios-at-the-lru-tail.patch