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Wed, 15 Oct 2025 23:43:20 -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 14:42:43 +0800 X-Gm-Features: AS18NWCmAzqewH7c8lKNSOM6N3YN2rFyfdEP9RCIkzoVhyDUX8WzpaYI1pA7pxE Message-ID: Subject: Re: [RFC PATCH v10 mm-new 6/9] bpf: mark mm->owner as __safe_rcu_or_null To: Andrii Nakryiko Cc: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.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-Server: rspam12 X-Rspamd-Queue-Id: 1606E140007 X-Stat-Signature: nga55hry9kurgbeogiky1ha6skudarf1 X-Rspam-User: X-HE-Tag: 1760597001-241573 X-HE-Meta: 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 bk1CAIal 8Gf/QqykmerRcOMvTfqVIweFKmX8A7JePnPX61r4gI7+SCLfo9RofdqsCsd0HLdHQNCe2aMMeRXIt06iaLZjfkIsi9nRVZW5qVS/g83bascwXGIBx498v1lBw9l0Nfe6fT24MFIFkNgPa4u+4Lbhgynbi1QK37GdwCfmYK+qdRKwR/nsz8JPb8nQZdhZ1Iy+iuAP2gchYM7VODi4wDFzSm7hbTT3+pcGoo2GL8Uh7vRiLBA1rInZ7r+pGyj1+f6a+Ri+x+J7SU/8hirVbr6HD25eZ+jpW51tNAMSqmUKtIa+fdYJEpVQgsPcau/5DMcB+I+bU/E93tIt9o80KST/W8XsNC6ZcBHGa2Yxo37XbFREW31ZewblmMZNWit1p4rKiom3oxJH2QF7dC7YejC7DYGNTGcY1xKcre9Lv3HvcZMBVfG4RdB5mGGm/5WYsWkRLvQNnb7I/KJYQpGs/0TBuR/gD3HlYnPMay1cdII4TLKcc/zhTU6Ey/ZNUKvh3H/Mow61nFCBNtLQjiFMAGWHIdy1ORNepit2jfQKPqQZCievYqTJ82vwFMTNq/+AD8EcBOJXHJK6w7MhnzUc= 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 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. The > > 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 field > > @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 your > 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.com/ --=20 Regards Yafang