From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-io1-f45.google.com (mail-io1-f45.google.com [209.85.166.45]) (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 79EF34D9FF for ; Fri, 15 Mar 2024 18:28:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710527334; cv=none; b=c9kQxtbqxG3PxkutBmNM50pZBIVKBwOkgu5/svSrmKl5V25QyTAbbrCxuOH0JIqq4mIi+mLVQNfXF1wjrYVC8K2rSc+VA7tiawapXSbWf3AaChv3UVTWzCylkcJqAygVWHTef/PqQqCMU7dRa4/0x+efBdFJ5Yf5dYlq/25JwBU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710527334; c=relaxed/simple; bh=lWf98zPH7AshEAfiihgiLaljEiVmaYNX6Bsa9pdVB3Q=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=rnzQsm6hNogX8nTpC+/7p8nJkLE7k6bML1LQiTqIN0VGhBeEP7Zf+uPfXGLF8I2tlj+8RX3oYiU02Lvh2xez8DJtQWPqgqiCEsIWoilzi6ol3nBvY6sqbLT41RRglrlUKoNQjqmXcLT7yMKnZLc09AqBUgrJEJrienYuidtR578= 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=fkMPeTfX; arc=none smtp.client-ip=209.85.166.45 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="fkMPeTfX" Received: by mail-io1-f45.google.com with SMTP id ca18e2360f4ac-7c8d3da056aso39262739f.2 for ; Fri, 15 Mar 2024 11:28:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netflix.com; s=google; t=1710527329; x=1711132129; 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=lCgfh3Sxm/BV+pCR26EGSXvQQ7SOcSkk18NjS+RmHtA=; b=fkMPeTfXdww4tYqDlvBxrFDh4WXGOgfIsQ4XeTXXCCzBD1jXRy+CIsK521iYLfcmNA D6rf+ZmZqeqH+RZFa9pmr44vr5hljIw9aEVbb6R5uiqs0oF2j9NwbhiVaMEDCl/uRhui KpvrSY6oZ29LOLP23D06QZLwkD+wdAQcKbBxo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710527329; x=1711132129; 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=lCgfh3Sxm/BV+pCR26EGSXvQQ7SOcSkk18NjS+RmHtA=; b=ZmNOBr51ClPRJpDGmNvhXZ4jp2jUtAhBrzvjkPKLrsvH8EqVOOUyvFtOFPzBIUJUy0 WtLhCjbAzRdeNDIfI8ao2oVtESyqIBRZxrqL8nitGoMgVgDCQ117EqqW6FVxC91sltwc HfCEPLEq7mjlUjE02sCBByt/5VQybP05vqJXCb55UcYLIfVVKa5R06N4oomoRxgU91rl 78RdKzlcLAlyF1MIc6t+h8K2PaC2QrWJ/R8ULb7LzWAG9FSOVYzgP4Ak5cBjqvOUceOE BJ/6BNX9x9ddbzwyqAjJKookY6Hwhr4bIPOdCPsLVUgimOHpqWnLRHqBJ5PvxNhgDdZj IX4A== X-Forwarded-Encrypted: i=1; AJvYcCVJPldN8IsDTNofNQg6dOXZKwMC+uUpGWwbaZvu7czU6KeuXE6vqjbADC1DhAW8A1NAT+v6oQhnj9HTUHFU+k5iq/oSs5MC/jVxpk1R X-Gm-Message-State: AOJu0Yw7QBkBXrLNXYVw+e2Qhvgfn7rLSwo+t9DI7E0hUtUXAB5FE3sd IMsvN8OpsJDs/BGSugfEhdwqPKtRVDeP+mP1mJ166HvjySyruQK0Ibmz87q3k4U= X-Google-Smtp-Source: AGHT+IGbfe1+m911z4rDE0JLVaBIDIJ1kWDx4d7pMYs3vMUJE4YT+724SXKHssUqJerD08G4ekyvPw== X-Received: by 2002:a05:6602:184b:b0:7ca:ebbc:ee27 with SMTP id d11-20020a056602184b00b007caebbcee27mr5832106ioi.21.1710527329584; Fri, 15 Mar 2024 11:28:49 -0700 (PDT) Received: from localhost ([2601:285:8700:8f20:c760:7c0b:344d:cd33]) by smtp.gmail.com with UTF8SMTPSA id dl22-20020a056638279600b00477b9971a45sm185526jab.17.2024.03.15.11.28.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Mar 2024 11:28:49 -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 bpf-next 1/2] bpf: add btf_task_get_cgroup_id kfunc Date: Fri, 15 Mar 2024 12:28:03 -0600 Message-Id: <20240315182804.216081-1-josef@netflix.com> X-Mailer: git-send-email 2.40.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This patch enhances the BPF helpers by adding a kfunc to retrieve the cgroup v2 ID of a specific 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 previous and next tasks. The bpf_task_get_cgroup_id kfunc returns a task's cgroup ID, correctly implementing RCU read locking and unlocking for safe data access, and leverages existing cgroup.h helpers to fetch the cgroup and its ID. Signed-off-by: Jose Fernandez Reviewed-by: Tycho Andersen --- kernel/bpf/helpers.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index a89587859571..8038b2bd3488 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2266,6 +2266,27 @@ bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) return NULL; return cgrp; } + +/** + * bpf_task_get_cgroup_id - Get the cgroup ID of a task. + * @task: The target task + * + * This function returns the ID of 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. + */ +__bpf_kfunc u64 bpf_task_get_cgroup_id(struct task_struct *task) +{ + struct cgroup *cgrp; + u64 cgrp_id; + + rcu_read_lock(); + cgrp = task_dfl_cgroup(task); + cgrp_id = cgroup_id(cgrp); + rcu_read_unlock(); + return cgrp_id; +} #endif /* CONFIG_CGROUPS */ /** @@ -2573,6 +2594,7 @@ 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_id, KF_RCU) #endif BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_throw) -- 2.40.1