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AJvYcCWRiy6vfq9WW/kkmfyfAQcyIdc85K0wLOjHrPYsMQ41CJb9rjxiFN641iGwqtNzTlauqRVVCWTM1w==@kvack.org X-Gm-Message-State: AOJu0YyCVYr2GsbzcsSiTy0XH6VuRFqSVeRM6WUSvk17/x/Gd7Q2UTOS U6mebmFXm/wW+6xrdVdMqxIBZPIkpB+Hj63oJMuTmjlVGqWgrjTAsuq8h1egeDQTWIjwld8Tdus kNvJg6If48W1aL5TssdwtbObwUr/OSKI= X-Gm-Gg: ASbGnctIv+88fQJe5WtB1SNfleSgqHuXOwqEaK27FrIRZhsB838F55STjNAaivLKYRh zJAjK6TGtc9MMcpMibBjVWpMXmouQDUzJIqMIK2V5y2fRxJcvaFTpmB5nbNuQDK6qqbw4GtRudE FJYc9bZ49vsa7P885hJoPFmkOJbaFfHdtq7Wbn9n3U2UOtDAMnZvMLiFwZX30pczBjSujhjtCom KkmCyzuAsWpyZlWxKv2ChFWYVwvoE2viNJqMlnRiJ7CAKq6WLFuBB/ADauzmiQ= X-Google-Smtp-Source: AGHT+IFGNrAI2dq3NSrRL0OcSYM4Z5okAFYQKhuh27ccqKymPLtZeC7L6zTwS+qJQzu1LIvsGty8JwB7F48ezlC7tv0= X-Received: by 2002:a17:90b:3ec6:b0:339:ec9c:b26d with SMTP id 98e67ed59e1d1-33b510f8488mr41389554a91.8.1760546165323; Wed, 15 Oct 2025 09:36:05 -0700 (PDT) MIME-Version: 1.0 References: <20251015141716.887-1-laoar.shao@gmail.com> <20251015141716.887-7-laoar.shao@gmail.com> In-Reply-To: <20251015141716.887-7-laoar.shao@gmail.com> From: Andrii Nakryiko Date: Wed, 15 Oct 2025 09:35:52 -0700 X-Gm-Features: AS18NWADyZQhCWHApHI8yY-s9dj0g7hVHDNjJ__LLzs5iWjWLcNDNGLGYWesqlU Message-ID: Subject: Re: [RFC PATCH v10 mm-new 6/9] bpf: mark mm->owner as __safe_rcu_or_null To: Yafang Shao 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-Stat-Signature: 8t7y64xkioyiu4wr4d5o9dqpujyztd6u X-Rspamd-Queue-Id: C352C4000A X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760546166-96893 X-HE-Meta: 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 PInn61NN 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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 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? > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index c4f69a9e9af6..d400e18ee31e 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -7123,6 +7123,9 @@ BTF_TYPE_SAFE_RCU(struct cgroup_subsys_state) { > /* RCU trusted: these fields are trusted in RCU CS and can be NULL */ > BTF_TYPE_SAFE_RCU_OR_NULL(struct mm_struct) { > struct file __rcu *exe_file; > +#ifdef CONFIG_MEMCG > + struct task_struct __rcu *owner; > +#endif > }; > > /* skb->sk, req->sk are not RCU protected, but we mark them as such > -- > 2.47.3 >