From patchwork Tue Mar 19 05:03:01 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jose Fernandez X-Patchwork-Id: 781240 Received: from mail-yb1-f177.google.com (mail-yb1-f177.google.com [209.85.219.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0AC363E493 for ; Tue, 19 Mar 2024 05:04:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.177 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710824677; cv=none; b=JcJx9XwnKIAttX/BzvXWGumzeN1AJS4nDBMQkdlNsBWrt/C5vDpbWO5cq4CvSNsR+WI+pPbvEUTwQLC19XI2clVGzHODdUTuoBGfpe7dyJxEAezMPYaWY0AX9VOJtS2UL16CjkG5ye+rVEAq/L8no70M3MfNKShdpg4mSzBqxto= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710824677; c=relaxed/simple; bh=Lz2CrH8A7WjP27QDwUAd0Apjplhh1crikLeGS9SaF0E=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=BQZfLOcbrgaMGpNM45sWR//EJ6oKcudwNgELPOOdAbwYWdlOuO0ofPbQRawHPmLNGJwrk3Edp6EWRLW1NoalcU1UooKO6bgS31O75CYaPJGFambdgQy6pbAkByrnc7OabZY4aiDpQBjwOj95/S6YKmVllGo213zFVp09AxdGMhs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=netflix.com; spf=pass smtp.mailfrom=netflix.com; dkim=pass (1024-bit key) header.d=netflix.com header.i=@netflix.com header.b=OMRvrYg7; arc=none smtp.client-ip=209.85.219.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=netflix.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netflix.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=netflix.com header.i=@netflix.com header.b="OMRvrYg7" Received: by mail-yb1-f177.google.com with SMTP id 3f1490d57ef6-dcbc00f6c04so4453648276.3 for ; Mon, 18 Mar 2024 22:04:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netflix.com; s=google; t=1710824674; x=1711429474; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=C+tjYLQhJo+BMVuUInD+N/p7F8UX37fJMVNt77Cc/o8=; b=OMRvrYg7HgBuIVmUkj1ch1iK0S0ygVW8fUtADWjIpylwb6Hxo3l66hHvDxyVbY7eoa 221LGIRkuutwtnLCR6FLdS2PTXMf+ruKaVuZAn0yWT3ov0u/tQDXkwqNRtx+yf81aodF 1IJEPTgS0ODyBAQ9uFkRyrmGgrh15Tb25B3qg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710824674; x=1711429474; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=C+tjYLQhJo+BMVuUInD+N/p7F8UX37fJMVNt77Cc/o8=; b=U1ZW1nBGnweZRoLSuGT9dF1EnyzCUDWxjI+60+EVQZuxVVyG+WFjbI3twFKpJ+hY0S 49pGtxettUcYg2h31YkHoSJF3c8euRBKS/Uh0pgCvf3VcWLVEc1zRbNTHKdIJ6AM+iQR PSQQkJwWeKmyKyaBVQyBe+2Mi3CfUnyPNV1VNplUwlFwY5r1HLn9F3wnR4saCYh4Zbnm zpnX+y079PvtIbkjWfDlePwWQyBl/kiTWGnIOjNJH3AXtD8nP/iSlRY8WPZ9VVlvJ8fB mK/n6TLAce1s10T+ldv1xmM9Y+6GHf69yVS7kuaqK2QnFhoOphySrw685oISX2d6wMvm ccKA== X-Forwarded-Encrypted: i=1; AJvYcCXPWAvBjkXWIQQx0EVGt/sU9RbwaerWoq57IN4goekUzmAZsbdyXCuGUgdpQ8JMT/zp+zmHhw8TLMhK4Ax0iwvi2Vv0KCSZfko24TUQRZgw X-Gm-Message-State: AOJu0YzBv6EHQSGS3ob9bfy5OpHAITqHE7CwMACn5xZRTKhWeV9n+koE yH6SboOJVlF6Nx9+WYTybMRW9pWaCPFEnym1vUMMSm0G/di5TyMhHxx++bGnXN4= X-Google-Smtp-Source: AGHT+IGKnEb1MFeHqBSw8vDsqBbEODWdU6GBl76O84BfZEbLJavR+eqn8sFeEHheRyEbc1ga1F6bAQ== X-Received: by 2002:a25:6405:0:b0:dc6:deca:468f with SMTP id y5-20020a256405000000b00dc6deca468fmr9032612ybb.29.1710824673931; Mon, 18 Mar 2024 22:04:33 -0700 (PDT) Received: from localhost ([12.220.158.163]) by smtp.gmail.com with UTF8SMTPSA id t10-20020a25908a000000b00dcc0cbb0aeesm2023977ybl.27.2024.03.18.22.04.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Mar 2024 22:04:33 -0700 (PDT) From: Jose Fernandez To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Jose Fernandez , Tycho Andersen Subject: [PATCH V3 bpf-next 1/2] bpf: add bpf_task_get_cgroup kfunc Date: Mon, 18 Mar 2024 23:03:01 -0600 Message-Id: <20240319050302.1085006-1-josef@netflix.com> X-Mailer: git-send-email 2.40.1 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This patch enhances the BPF helpers by adding a kfunc to retrieve the cgroup v2 of a task, addressing a previous limitation where only bpf_task_get_cgroup1 was available for cgroup v1. The new kfunc is particularly useful for scenarios where obtaining the cgroup ID of a task other than the "current" one is necessary, which the existing bpf_get_current_cgroup_id helper cannot accommodate. A specific use case at Netflix involved the sched_switch tracepoint, where we had to get the cgroup IDs of both the prev and next tasks. The bpf_task_get_cgroup kfunc acquires and returns a reference to a task's default cgroup, ensuring thread-safe access by correctly implementing RCU read locking and unlocking. It leverages the existing cgroup.h helper, and cgroup_tryget to safely acquire a reference to it. Signed-off-by: Jose Fernandez Reviewed-by: Tycho Andersen Acked-by: Yonghong Song Acked-by: Stanislav Fomichev Acked-by: Jiri Olsa Acked-by: Tejun Heo --- V2 -> V3: No changes V1 -> V2: Return a pointer to the cgroup instead of the cgroup ID kernel/bpf/helpers.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) base-commit: c733239f8f530872a1f80d8c45dcafbaff368737 diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index a89587859571..bbd19d5eedb6 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2266,6 +2266,31 @@ bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) return NULL; return cgrp; } + +/** + * bpf_task_get_cgroup - Acquire a reference to the default cgroup of a task. + * @task: The target task + * + * This function returns the task's default cgroup, primarily + * designed for use with cgroup v2. In cgroup v1, the concept of default + * cgroup varies by subsystem, and while this function will work with + * cgroup v1, it's recommended to use bpf_task_get_cgroup1 instead. + * A cgroup returned by this kfunc which is not subsequently stored in a + * map, must be released by calling bpf_cgroup_release(). + * + * Return: On success, the cgroup is returned. On failure, NULL is returned. + */ +__bpf_kfunc struct cgroup *bpf_task_get_cgroup(struct task_struct *task) +{ + struct cgroup *cgrp; + + rcu_read_lock(); + cgrp = task_dfl_cgroup(task); + if (!cgroup_tryget(cgrp)) + cgrp = NULL; + rcu_read_unlock(); + return cgrp; +} #endif /* CONFIG_CGROUPS */ /** @@ -2573,6 +2598,7 @@ BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU) BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_task_get_cgroup, KF_ACQUIRE | KF_RCU | KF_RET_NULL) #endif BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_throw)