From: Andrew Morton <akpm@linux-foundation.org>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
Kairui Song <kasong@tencent.com>, Qi Zheng <qi.zheng@linux.dev>,
Barry Song <baohua@kernel.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Meta kernel team <kernel-team@meta.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org,
syzbot+12ee2725d5fde63a9c96@syzkaller.appspotmail.com
Subject: Re: [PATCH 1/9] memcg: make the v1 soft limit knob inert
Date: Wed, 12 Aug 2026 15:50:10 -0700 [thread overview]
Message-ID: <20260812155010.8710b4a9191c9ee4ad6da255@linux-foundation.org> (raw)
In-Reply-To: <20260811203203.3456029-2-shakeel.butt@linux.dev>
On Tue, 11 Aug 2026 13:31:55 -0700 Shakeel Butt <shakeel.butt@linux.dev> wrote:
> The v1 soft limit has been deprecated since v6.12 and nobody has
> reported depending on it. Start the removal by decoupling the interface
> from the implementation: keep memory.soft_limit_in_bytes, but ignore
> writes to it and always report the maximum value on read similar to
> what memory.kmem.limit_in_bytes already does.
>
> Writes are still parsed, so malformed input keeps returning -EINVAL.
> The knob now also behaves the same everywhere: it used to return
> -EOPNOTSUPP on PREEMPT_RT, where soft limit reclaim has always been
> disabled.
>
> This also fixes the syzbot report linked below. Soft limit reclaim is
> the only caller that runs shrink_lruvec() from kswapd against a
> specific memcg, so it is the only way to reach lru_gen_shrink_lruvec()
> and in turn set_mm_walk(), which warns when called from kswapd.
Thanks, I'll pluck this one as a hotfix.
It's old code, yes? Are there any theories about why the sysbot issue
has just popped up? Should we backport the fix?
next prev parent reply other threads:[~2026-08-12 22:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-11 20:31 [PATCH for-7.4 0/9] memcg: remove the v1 soft limit Shakeel Butt
2026-08-11 20:31 ` [PATCH 1/9] memcg: make the v1 soft limit knob inert Shakeel Butt
2026-08-12 22:50 ` Andrew Morton [this message]
2026-08-12 23:40 ` Shakeel Butt
2026-08-11 20:31 ` [PATCH 2/9] memcg: remove v1 soft limit reclaim Shakeel Butt
2026-08-11 20:31 ` [PATCH 3/9] memcg: remove mem_cgroup_shrink_node() Shakeel Butt
2026-08-11 20:31 ` [PATCH 4/9] memcg: remove the soft limit reclaim tracepoints Shakeel Butt
2026-08-11 20:31 ` [PATCH 5/9] memcg: remove the soft limit rbtree Shakeel Butt
2026-08-11 20:32 ` [PATCH 6/9] memcg: remove lru_gen_soft_reclaim() Shakeel Butt
2026-08-11 20:32 ` [PATCH 7/9] memcg: remove the per-node soft limit tree fields Shakeel Butt
2026-08-11 20:32 ` [PATCH 8/9] memcg: remove mem_cgroup->soft_limit Shakeel Butt
2026-08-11 20:32 ` [PATCH 9/9] memcg: simplify v1 event ratelimiting Shakeel Butt
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