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[109.81.31.43]) by smtp.gmail.com with UTF8SMTPSA id a640c23a62f3a-b0761c9314esm150029966b.33.2025.09.08.23.20.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Sep 2025 23:20:51 -0700 (PDT) Date: Tue, 9 Sep 2025 08:20:50 +0200 From: Michal Hocko To: Alexei Starovoitov Cc: Peilin Ye , Shakeel Butt , Andrew Morton , Tejun Heo , Johannes Weiner , Roman Gushchin , Muchun Song , Alexei Starovoitov , Kumar Kartikeya Dwivedi , bpf , linux-mm , "open list:CONTROL GROUP (CGROUP)" , LKML , Meta kernel team Subject: Re: [PATCH] memcg: skip cgroup_file_notify if spinning is not allowed Message-ID: References: <20250905201606.66198-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: nsnwzpbz1ejub51o7yxgogjr66fmbzx4 X-Rspam-User: X-Rspamd-Queue-Id: 99444120007 X-Rspamd-Server: rspam04 X-HE-Tag: 1757398853-131228 X-HE-Meta: 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 KzOkOjte 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 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 08-09-25 10:11:29, Alexei Starovoitov wrote: > On Mon, Sep 8, 2025 at 2:08 AM Michal Hocko wrote: > > > > On Fri 05-09-25 20:48:46, Peilin Ye wrote: > > > On Fri, Sep 05, 2025 at 01:16:06PM -0700, Shakeel Butt wrote: > > > > Generally memcg charging is allowed from all the contexts including NMI > > > > where even spinning on spinlock can cause locking issues. However one > > > > call chain was missed during the addition of memcg charging from any > > > > context support. That is try_charge_memcg() -> memcg_memory_event() -> > > > > cgroup_file_notify(). > > > > > > > > The possible function call tree under cgroup_file_notify() can acquire > > > > many different spin locks in spinning mode. Some of them are > > > > cgroup_file_kn_lock, kernfs_notify_lock, pool_workqeue's lock. So, let's > > > > just skip cgroup_file_notify() from memcg charging if the context does > > > > not allow spinning. > > > > > > > > Signed-off-by: Shakeel Butt > > > > > > Tested-by: Peilin Ye > > > > > > The repro described in [1] no longer triggers locking issues after > > > applying this patch and making __bpf_async_init() use __GFP_HIGH > > > instead of GFP_ATOMIC: > > > > > > --- a/kernel/bpf/helpers.c > > > +++ b/kernel/bpf/helpers.c > > > @@ -1275,7 +1275,7 @@ static int __bpf_async_init(struct bpf_async_kern *async, struct bpf_map *map, u > > > } > > > > > > /* allocate hrtimer via map_kmalloc to use memcg accounting */ > > > - cb = bpf_map_kmalloc_node(map, size, GFP_ATOMIC, map->numa_node); > > > + cb = bpf_map_kmalloc_node(map, size, __GFP_HIGH, map->numa_node); > > > > Why do you need to consume memory reserves? Shouldn't kmalloc_nolock be > > used instead here? > > Yes. That's a plan. We'll convert most of bpf allocations to kmalloc_nolock() > when it lands. OK, I thought this was merged already. I suspect __GFP_HIGH is used here as a result of manual GFP_ATOMIC & ~GFP_RECLAIM. A TODO/FIXME referring to kmalloc_nolock would clarify the situation. -- Michal Hocko SUSE Labs