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Cc: zhuhui@kylinos.cn,geliang@kernel.org,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,clm@meta.com,ihor.solodrai@linux.dev
Subject: Re: [RFC PATCH bpf-next v5 08/12] mm: memcontrol: Add BPF struct_ops for memory controller
Date: Tue, 27 Jan 2026 10:08:36 +0000 (UTC) [thread overview]
Message-ID: <6173f32708a0a1401350ac03dfeb0c3a6b212331b233b3269ff708dfc74dcffe@mail.kernel.org> (raw)
In-Reply-To: <f14f1ad53f742f993a7ac5cb5ba6eaee26bebd91.1769506741.git.zhuhui@kylinos.cn>
[-- Attachment #1: Type: text/plain, Size: 2175 bytes --]
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1f74fce27677..8d90575aa77d 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
[ ... ]
> @@ -2530,10 +2537,14 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
> * kernel. If this is successful, the return path will see it
> * when it rechecks the overage and simply bail out.
> */
> - if (current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH &&
> - !(current->flags & PF_MEMALLOC) &&
> - gfpflags_allow_blocking(gfp_mask))
> - __mem_cgroup_handle_over_high(gfp_mask);
> + if (gfpflags_allow_blocking(gfp_mask)) {
> + unsigned long bpf_high_delay;
> +
> + bpf_high_delay = bpf_memcg_get_high_delay(orig_memcg);
> + if (bpf_high_delay ||
> + current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH)
> + __mem_cgroup_handle_over_high(gfp_mask, bpf_high_delay);
> + }
The old code checked !(current->flags & PF_MEMALLOC) before calling
__mem_cgroup_handle_over_high(). This check appears to be missing in the
new code.
When PF_MEMALLOC is set, the task is already in the memory reclaim context.
Calling __mem_cgroup_handle_over_high() from such a context would invoke
reclaim_high() -> try_to_free_mem_cgroup_pages(), potentially causing
reclaim recursion.
Was the removal of the PF_MEMALLOC check intentional? If a BPF program
returns a non-zero delay from get_high_delay_ms while the task is in a
reclaim context, could this lead to recursive reclaim or deadlock?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21392729810
AI-authorship-score: low
AI-authorship-explanation: The code shows typical human characteristics including a refactoring oversight that AI would likely not make; the commit follows standard kernel conventions and has multiple human authors.
issues-found: 1
issue-severity-score: medium
issue-severity-explanation: Missing PF_MEMALLOC check could cause memory reclaim recursion when BPF programs are attached, potentially leading to system instability.
next prev parent reply other threads:[~2026-01-27 10:08 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-27 9:42 [RFC PATCH bpf-next v5 00/12] mm: memcontrol: Add BPF hooks " Hui Zhu
2026-01-27 9:42 ` [RFC PATCH bpf-next v5 01/12] bpf: move bpf_struct_ops_link into bpf.h Hui Zhu
2026-01-27 9:42 ` [RFC PATCH bpf-next v5 02/12] bpf: initial support for attaching struct ops to cgroups Hui Zhu
2026-01-27 9:42 ` [RFC PATCH bpf-next v5 03/12] bpf: mark struct oom_control's memcg field as TRUSTED_OR_NULL Hui Zhu
2026-01-27 9:42 ` [RFC PATCH bpf-next v5 04/12] mm: define mem_cgroup_get_from_ino() outside of CONFIG_SHRINKER_DEBUG Hui Zhu
2026-01-27 9:42 ` [RFC PATCH bpf-next v5 05/12] libbpf: introduce bpf_map__attach_struct_ops_opts() Hui Zhu
2026-01-27 10:08 ` bot+bpf-ci
2026-01-27 9:45 ` [RFC PATCH bpf-next v5 06/12] bpf: Pass flags in bpf_link_create for struct_ops Hui Zhu
2026-01-27 9:45 ` [RFC PATCH bpf-next v5 07/12] libbpf: Support passing user-defined flags " Hui Zhu
2026-01-27 9:45 ` [RFC PATCH bpf-next v5 08/12] mm: memcontrol: Add BPF struct_ops for memory controller Hui Zhu
2026-01-27 10:08 ` bot+bpf-ci [this message]
2026-01-27 9:47 ` [RFC PATCH bpf-next v5 09/12] selftests/bpf: Add tests for memcg_bpf_ops Hui Zhu
2026-01-27 10:08 ` bot+bpf-ci
2026-01-27 9:47 ` [RFC PATCH bpf-next v5 10/12] mm/bpf: Add BPF_F_ALLOW_OVERRIDE support " Hui Zhu
2026-01-27 10:08 ` bot+bpf-ci
2026-01-27 9:47 ` [RFC PATCH bpf-next v5 11/12] selftests/bpf: Add test for memcg_bpf_ops hierarchies Hui Zhu
2026-01-27 9:48 ` [RFC PATCH bpf-next v5 12/12] samples/bpf: Add memcg priority control example Hui Zhu
2026-01-27 10:08 ` bot+bpf-ci
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