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b=tiQ2QQ+/tugRqJGTfepSFY1hDwW/i74IZieK5RoR+GP4YTR4Cb+1Zc4bBqSBS1N0P LLnVNlvDIlQuGY+Rnz1AHWQZPuHeCjCgtjRK/zgILMh6FIAbuJ6POUDrIwljrgWgyM 5JdqQ24zfkvP7xBXYQ0/nsfVv9cNv1URigg1cYfc= Date: Mon, 22 Sep 2025 16:43:28 -0700 From: Andrew Morton To: Shakeel Butt Cc: Tejun Heo , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Alexei Starovoitov , Peilin Ye , Kumar Kartikeya Dwivedi , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team , Michal Hocko Subject: Re: [PATCH v2] memcg: skip cgroup_file_notify if spinning is not allowed Message-Id: <20250922164328.0d766c95f9c15330e99514bd@linux-foundation.org> In-Reply-To: References: <20250922220203.261714-1-shakeel.butt@linux.dev> <20250922160308.524be6ba4d418886095ab223@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: xnejwp11t13jde41wxq1txdkdqf96ers X-Rspamd-Queue-Id: 33FE3180006 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1758584611-686059 X-HE-Meta: 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 B+/k1Fq0 IdcPW/zsdA0aEmz4iMEz3BCyp00k/k7Wgkm5DWm/iJVKG8TOxuVpoBXmA7DKICRQs9eIEJYE7JkZ/IKB/LiQaA1XRHmgJRWymBtWzdMHH/ePt6cYAw82PrRvoGFQ7YX4+e+vQVVuayWEiqc5coIQBbT0VYrBiTyJ4a26J2q442JRznqEQrZKdoVhKT+MJDT4xSGsZCaQu6++R7ufFijiFniuS64ttBauFCtoZRHOeQnw6I3651YX5MhmRwHzawxjij4A5Q19BsfRqHmZ4O5dIUoiu801pQXuf8FWM0ppNydRXPBI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 22 Sep 2025 16:22:57 -0700 Shakeel Butt wrote: > > > > > --- a/mm/memcontrol.c > > > +++ b/mm/memcontrol.c > > > @@ -2307,12 +2307,13 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > > > bool drained = false; > > > bool raised_max_event = false; > > > unsigned long pflags; > > > + bool allow_spinning = gfpflags_allow_spinning(gfp_mask); > > > > > > > Does this affect only the problematic call chain which you have > > identified, or might other callers be undesirably affected? > > It will only affect the call chain which can not spin due to possibly > NMI context and at the moment only bpf programs can cause that. "possibly" NMI context? Is it possible that a bpf caller which could have taken locks will now skip the notifications? Or do the gfp_flags get propagated all the way through?