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Date: Sat, 17 Oct 2026 13:18:30 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
Cc: hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org,
 qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org,
 kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com,
 yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev,
 baolin.wang@linux.alibaba.com, yuzhao@google.com, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, apais@microsoft.com, rlmenge@gmail.com,
 stable@vger.kernel.org, Hardik Garg <hargar@linux.microsoft.com>
Subject: Re: [PATCH v2 1/2] mm: multi-gen LRU: fix NULL lruvec->pgdat deref
 with memcg disabled on cmdline
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On Sat, 17 Oct 2026 05:09:27 +0000 Siddharth Chintamaneni <sidchintamaneni@gmail.com> wrote:

> When CONFIG_MEMCG=y, lruvec_pgdat() returns lruvec->pgdat, which for the
> per-node pgdat->__lruvec is left NULL by lruvec_init() and only filled in
> lazily by mem_cgroup_lruvec(). Normally that happens early, e.g. on the
> first folio_add_lru().
> 
> With cgroup_disable=memory, lru_gen_shrink_node() passes &pgdat->__lruvec
> directly to shrink_one(). If direct reclaim runs before anything has
> called mem_cgroup_lruvec() for the node, which can happen during early
> boot under memory pressure (e.g. a kdump kernel), get_swappiness() ends
> up dereferencing a NULL pgdat:

Thanks, v2 lgtm.

Maintainers: please review and let us know whether you agree with the
cc:stable on both.