Re: [PATCH v2 1/2] mm: multi-gen LRU: fix NULL lruvec->pgdat deref with memcg disabled on cmdline

[Andrew Morton]

On Sat, 17 Oct 2026 05:09:27 +0000 Siddharth Chintamaneni <sidchintamaneni@xxxxxxxxx> 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.