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Thu, 16 Oct 2025 01:18:44 -0700 (PDT) MIME-Version: 1.0 References: <20251015141716.887-1-laoar.shao@gmail.com> <20251015141716.887-7-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Thu, 16 Oct 2025 16:18:08 +0800 X-Gm-Features: AS18NWD2AXGKlmvFo5UH1F2cQyeA_L5yHcpBAgeZL4_sZgqmARGxyWqYqUTXbrc Message-ID: Subject: Re: [RFC PATCH v10 mm-new 6/9] bpf: mark mm->owner as __safe_rcu_or_null To: Lorenzo Stoakes Cc: Andrii Nakryiko , akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, 21cnbao@gmail.com, shakeel.butt@linux.dev, tj@kernel.org, lance.yang@linux.dev, rdunlap@infradead.org, bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: EA50C40004 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: dk6wt96q1hcqgifpmgwuqfjhmr3dh1zf X-HE-Tag: 1760602725-513729 X-HE-Meta: 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 KWIzoaeT yMYzlNdmH/LYe5NXIqUIotY+cHTxl2oWVwrOCyvT69syTnPPN23m1K8IzsM2bLg8VQwgB7/vcuj1svdhljLFEI+zCMEdje9CfFlR7HnKeo0yld1COw0FX5wo279gvDVGdbyjtmMXQcw7zNPdiFSUfxotlKHJxqoXV70sZ/zvCX5HRi9r2z4o3ex7+fh12W+ENnbPW+K8afAE+pa0UhfbU17hld3QQhoA6fMi8d5qk+thLmSQ1J9NIbeyNe36DbJbSefoBiI5TEpyRC55WjClwknyNTRGtOVJGf9T24wssOf7MbNtLA4ZRiErKbeVIyhLETFXRVtIAd/ldJtFmAX6DR1kVT8utmIKzqDDRkLxbHcm9IqhkAFwsJuNki7vOuanygtJG9AYOqoIi5KctozpwgqoOFJSlfj0ftS8d0J78BvJJhKXzzx9Ah+P881kY8aXjALeJXi5miWI/QeczPl0dcyBGatQmgFVi7myup3noVOVRHiRWssyJhd4tHbyg44mJPh5HGQwwJVm1wvZUrB4deJ1A9dzU1MINnWzfhbSV00KOKjYqK8bcrUOEM0HJTEG9TzLeSf18d+iS65A= 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 Thu, Oct 16, 2025 at 3:21=E2=80=AFPM Lorenzo Stoakes wrote: > > On Thu, Oct 16, 2025 at 02:42:43PM +0800, Yafang Shao wrote: > > On Thu, Oct 16, 2025 at 12:36=E2=80=AFAM Andrii Nakryiko > > wrote: > > > > > > On Wed, Oct 15, 2025 at 7:18=E2=80=AFAM Yafang Shao wrote: > > > > > > > > When CONFIG_MEMCG is enabled, we can access mm->owner under RCU. Th= e > > > > owner can be NULL. With this change, BPF helpers can safely access > > > > mm->owner to retrieve the associated task from the mm. We can then = make > > > > policy decision based on the task attribute. > > > > > > > > The typical use case is as follows, > > > > > > > > bpf_rcu_read_lock(); // rcu lock must be held for rcu trusted fie= ld > > > > @owner =3D @mm->owner; // mm_struct::owner is rcu trusted or null > > > > if (!@owner) > > > > goto out; > > > > > > > > /* Do something based on the task attribute */ > > > > > > > > out: > > > > bpf_rcu_read_unlock(); > > > > > > > > Suggested-by: Andrii Nakryiko > > > > Signed-off-by: Yafang Shao > > > > Acked-by: Lorenzo Stoakes > > > > --- > > > > kernel/bpf/verifier.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > > > I thought you were going to send this and next patches outside of you= r > > > thp patch set to land them sooner, as they don't have dependency on > > > the rest of the patches and are useful on their own? > > > > Thanks for your reminder. > > They have been sent separately: > > > > https://lore.kernel.org/bpf/20251016063929.13830-1-laoar.shao@gmail.c= om/ > > Could we respin this as a v2 without them then please so we can sensibly = keep > the two separate? Sure, I will send a v2. > > Thanks! > > > > > -- > > Regards > > Yafang > > I do intend to have a look through the various conversations on this, jus= t > catching up after 2 weeks vacation :) in the kernel this is an eternity, = even > during the merge window it seems :P Huh, we've been refactoring a bit too fast and furious since your last review ;-) --=20 Regards Yafang