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Sun, 17 Aug 2025 22:55:44 -0700 (PDT) Received: from localhost.localdomain ([39.144.105.14]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-323439961c9sm7003413a91.13.2025.08.17.22.55.38 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 17 Aug 2025 22:55:44 -0700 (PDT) From: Yafang Shao To: 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 Cc: bpf@vger.kernel.org, linux-mm@kvack.org, Yafang Shao Subject: [RFC PATCH v5 mm-new 3/5] mm: thp: add a new kfunc bpf_mm_get_task() Date: Mon, 18 Aug 2025 13:55:08 +0800 Message-Id: <20250818055510.968-4-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20250818055510.968-1-laoar.shao@gmail.com> References: <20250818055510.968-1-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit We will utilize this new kfunc bpf_mm_get_task() to retrieve the associated task_struct from the given @mm. The obtained task_struct must be released by calling bpf_task_release() as a paired operation. Signed-off-by: Yafang Shao --- mm/bpf_thp.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/mm/bpf_thp.c b/mm/bpf_thp.c index bdcf6f6af99b..8ed1bf0d7f4d 100644 --- a/mm/bpf_thp.c +++ b/mm/bpf_thp.c @@ -205,11 +205,45 @@ __bpf_kfunc void bpf_put_mem_cgroup(struct mem_cgroup *memcg) #endif } +/** + * bpf_mm_get_task - Get the task struct associated with a mm_struct. + * @mm: The mm_struct to query + * + * The obtained task_struct must be released by calling bpf_task_release(). + * + * Return: The associated task_struct on success, or NULL on failure. Note that + * this function depends on CONFIG_MEMCG being enabled - it will always return + * NULL if CONFIG_MEMCG is not configured. + */ +__bpf_kfunc struct task_struct *bpf_mm_get_task(struct mm_struct *mm) +{ +#ifdef CONFIG_MEMCG + struct task_struct *task; + + if (!mm) + return NULL; + rcu_read_lock(); + task = rcu_dereference(mm->owner); + if (!task) + goto out; + if (!refcount_inc_not_zero(&task->rcu_users)) + goto out; + + rcu_read_unlock(); + return task; + +out: + rcu_read_unlock(); +#endif + return NULL; +} + __bpf_kfunc_end_defs(); BTF_KFUNCS_START(bpf_thp_ids) BTF_ID_FLAGS(func, bpf_mm_get_mem_cgroup, KF_TRUSTED_ARGS | KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_put_mem_cgroup, KF_RELEASE) +BTF_ID_FLAGS(func, bpf_mm_get_task, KF_TRUSTED_ARGS | KF_ACQUIRE | KF_RET_NULL) BTF_KFUNCS_END(bpf_thp_ids) static const struct btf_kfunc_id_set bpf_thp_set = { -- 2.47.3