From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89D38C369C2 for ; Mon, 28 Apr 2025 03:36:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C42446B0023; Sun, 27 Apr 2025 23:36:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BE6EE6B0024; Sun, 27 Apr 2025 23:36:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AAEEE6B0025; Sun, 27 Apr 2025 23:36:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 887126B0023 for ; Sun, 27 Apr 2025 23:36:54 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 84A01C1220 for ; Mon, 28 Apr 2025 03:36:54 +0000 (UTC) X-FDA: 83382041148.27.FBA7290 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) by imf02.hostedemail.com (Postfix) with ESMTP id E5D2780007 for ; Mon, 28 Apr 2025 03:36:52 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="UhML/02x"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf02.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.183 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1745811413; a=rsa-sha256; cv=none; b=ZdfXa9GmJe8nXt3afWU0zikhomqcjevV9FH95Kqi9ZMHZlQQW9nNGPIfVqoiV3n1/59Wdr KADaRVh9PCbE4bamAyGfO21b2CbnRc55KK4SfvMv43vpbOVEJZTI0kDSrvjciu/Cue/dTl r1se+WwQGRUg2qO/7Fo4dnmpIpedD+w= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="UhML/02x"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf02.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.183 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1745811413; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qfqCE3hqvHS+xiXy15ifFZ17rwxpSXuqOJ5f+GS0Txw=; b=xygPFH2fR8Rdop1ByITisFmglTDVKtSRdfBHoo6hOg+2OBzo/QF5VIgby4V0rdB/wWNOlQ SKCcfTjVnA8Kl+t9TD2SxqlkG4528MFWg5K7QBdBTRcjHKfV/uzgZ9xg1KtMdqOPBXWxW+ 1ag62VVCu2IUMwk1VvdEh7vcTizhlE4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1745811411; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qfqCE3hqvHS+xiXy15ifFZ17rwxpSXuqOJ5f+GS0Txw=; b=UhML/02xIM7DqvIPdJnhpoz8FvXU+vUJ3076QF2Bjl8xAs4sHviG4NWvY3TA/Iaktg77gS UnzlxPWUWfB/AMcFRYJ1/Fk7r9XaTgqUF7FVAkeKd41yMUa2h8UWiWu2HaHPsT6vXSK9xT dxuqZuQBnCjYC5nbqtW+gYFEomHsXZY= From: Roman Gushchin To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Alexei Starovoitov , Johannes Weiner , Michal Hocko , Shakeel Butt , Suren Baghdasaryan , David Rientjes , Josh Don , Chuyi Zhou , cgroups@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Roman Gushchin Subject: [PATCH rfc 06/12] mm: introduce bpf_get_root_mem_cgroup() bpf kfunc Date: Mon, 28 Apr 2025 03:36:11 +0000 Message-ID: <20250428033617.3797686-7-roman.gushchin@linux.dev> In-Reply-To: <20250428033617.3797686-1-roman.gushchin@linux.dev> References: <20250428033617.3797686-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E5D2780007 X-Stat-Signature: 396r44qkwqdgcxhhxoi3wifaz3z5d4jc X-Rspam-User: X-HE-Tag: 1745811412-857652 X-HE-Meta: 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 fhQTDhMN wz0r0GXI8lif5TmpqzdZlVmHg9o1tkf3rKUGHJ4pM7afq0XgYqIh7/zvJET8smrV/FysE5wwFXCQTiZhFwOwlKV7cS9BvMGwXiBPRcAlY8ndmlPROIuleg9uXyA4LQh5IBGUANErxxbG25G+VaSycSPRbnEmzdVmenKfLqq7uYz5173jZTmKyr8aGg0XyPhgmEqmeE2iRwbepCSHfUV0/2Vcg+Q== 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: Introduce a bpf kfunc to get a trusted pointer to the root memory cgroup. It's very handy to traverse the full memcg tree, e.g. for handling a system-wide OOM. It's possible to obtain this pointer by traversing the memcg tree up from any known memcg, but it's sub-optimal and makes bpf programs more complex and less efficient. bpf_get_root_mem_cgroup() has a KF_ACQUIRE | KF_RET_NULL semantics, however in reality it's not necessarily to bump the corresponding reference counter - root memory cgroup is immortal, reference counting is skipped, see css_get(). Once set, root_mem_cgroup is always a valid memcg pointer. It's safe to call bpf_put_mem_cgroup() for the pointer obtained with bpf_get_root_mem_cgroup(), it's effectively a no-op. Signed-off-by: Roman Gushchin --- mm/bpf_memcontrol.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c index dacdf53735e5..94bc6c17d80b 100644 --- a/mm/bpf_memcontrol.c +++ b/mm/bpf_memcontrol.c @@ -10,6 +10,12 @@ __bpf_kfunc_start_defs(); +__bpf_kfunc struct mem_cgroup *bpf_get_root_mem_cgroup(void) +{ + /* css_get() is not needed */ + return root_mem_cgroup; +} + __bpf_kfunc struct mem_cgroup * bpf_get_mem_cgroup(struct cgroup_subsys_state *css) { @@ -72,6 +78,7 @@ __bpf_kfunc void bpf_mem_cgroup_flush_stats(struct mem_cgroup *memcg) __bpf_kfunc_end_defs(); BTF_KFUNCS_START(bpf_memcontrol_kfuncs) +BTF_ID_FLAGS(func, bpf_get_root_mem_cgroup, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_get_mem_cgroup, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_put_mem_cgroup, KF_RELEASE) -- 2.49.0.901.g37484f566f-goog