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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04074C433F5 for ; Mon, 25 Oct 2021 06:19:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEE9F604DA for ; Mon, 25 Oct 2021 06:19:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230368AbhJYGWI (ORCPT ); Mon, 25 Oct 2021 02:22:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230342AbhJYGWG (ORCPT ); Mon, 25 Oct 2021 02:22:06 -0400 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59464C061745 for ; Sun, 24 Oct 2021 23:19:45 -0700 (PDT) Received: by mail-pj1-x104a.google.com with SMTP id n2-20020a17090a2fc200b001a1bafb59bfso6532972pjm.1 for ; Sun, 24 Oct 2021 23:19:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=ZWcH7rWC3ZsHErnrMwwxWzyNMoxVakai+vPjAaFHzVQ=; b=hOMf4il33vbkfJyrzLVbrglaaETehyTreBSt+7K7c6eZFmlWBxyFhb8QmG53tAMHjo 9A8hK5RqzXNl6UGb+aHrz3o1OoeY2Qi/m87JHrptd2Cscjtjhi5OKqHdS3euGZ+DDudF vDpFkGp7HmYoSHhDu/i8JDYjJ/9Lj7E5M5UyH79Xjg+64TS9RKsRfayisnySku0cQpbz UtDKoXNGhPG1DtxPSW40RGRHQEKG2ZqIpmm1+0BsfREZ2y4LufrJHNbKls/e8a1bWs3t JqdKSFi/RIalkhdeKVCE8qoaIHmviBIT1IK5Avzg832qRyK/hHnWPb2D5A/j1A1wC+am eBCw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=ZWcH7rWC3ZsHErnrMwwxWzyNMoxVakai+vPjAaFHzVQ=; b=NIfnfnigOvMsIpNons5xGsQ8LJhaSKDTUFfclh5rrujjmzEvvjp/38jJ2/Lz6pSeUB ML8bzeL9j3/tYp9+2b+4fg+XMxky30pTazwzni46/MxzI+6i4unH6DHmqVT6rZVX4e8o OicGwE+qOmXIKPCSpdCUux7bC3DwL7zSx0ukSRKeoDdnWAhHYHls8pnz7izDWnZmPuE1 0R0RoVOUUEIeG6NruPWLDLgDBc0xFe56olbjDFSKVjLLYfis/yUryZ+WMZvGAsUmgysd 2GU9WjsUGaUBEuNFR5xow4z9dVjNMoDyXU5wzPsLv2xxgj2usEvgnhcvGxQ6YZuHZdpn V29g== X-Gm-Message-State: AOAM533nFiRzhzdR01n+MVIBgjZusQQ6q92vI9yAdmjahlSCOCzEXEfa bfaHOnJlRyBdHF196B8Mr27kjO2npvVGaw== X-Google-Smtp-Source: ABdhPJx9F7pAWgZ6WYTAsccOwUOsCSZiJ6kXBdE/NiUDfqEGLGo/WzXciBcY4CWxMDQ4aOh3tIen2NBAb17VnA== X-Received: from shakeelb.svl.corp.google.com ([2620:15c:2cd:202:faf1:73d1:a656:9f7e]) (user=shakeelb job=sendgmr) by 2002:a17:90a:62ca:: with SMTP id k10mr18394369pjs.38.1635142784779; Sun, 24 Oct 2021 23:19:44 -0700 (PDT) Date: Sun, 24 Oct 2021 23:19:15 -0700 In-Reply-To: <20211025061916.3853623-1-shakeelb@google.com> Message-Id: <20211025061916.3853623-2-shakeelb@google.com> Mime-Version: 1.0 References: <20211025061916.3853623-1-shakeelb@google.com> X-Mailer: git-send-email 2.33.0.1079.g6e70778dc9-goog Subject: [PATCH 2/3] cgroup: remove cgroup_mutex from cgroupstats_build From: Shakeel Butt To: Tejun Heo Cc: "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Shakeel Butt Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The function cgroupstats_build extracts cgroup from the kernfs_node's priv pointer which is a RCU pointer. So, there is no need to grab cgroup_mutex. Just get the reference on the cgroup before using and remove the cgroup_mutex altogether. Signed-off-by: Shakeel Butt --- kernel/cgroup/cgroup-v1.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index f6cc5f8484dc..fd14a60379c1 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -698,8 +698,6 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) kernfs_type(kn) != KERNFS_DIR) return -EINVAL; - mutex_lock(&cgroup_mutex); - /* * We aren't being called from kernfs and there's no guarantee on * @kn->priv's validity. For this and css_tryget_online_from_dir(), @@ -707,9 +705,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) */ rcu_read_lock(); cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv); - if (!cgrp || cgroup_is_dead(cgrp)) { + if (!cgrp || !cgroup_tryget(cgrp)) { rcu_read_unlock(); - mutex_unlock(&cgroup_mutex); return -ENOENT; } rcu_read_unlock(); @@ -737,7 +734,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) } css_task_iter_end(&it); - mutex_unlock(&cgroup_mutex); + cgroup_put(cgrp); return 0; } -- 2.33.0.1079.g6e70778dc9-goog From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shakeel Butt Subject: [PATCH 2/3] cgroup: remove cgroup_mutex from cgroupstats_build Date: Sun, 24 Oct 2021 23:19:15 -0700 Message-ID: <20211025061916.3853623-2-shakeelb@google.com> References: <20211025061916.3853623-1-shakeelb@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=ZWcH7rWC3ZsHErnrMwwxWzyNMoxVakai+vPjAaFHzVQ=; b=hOMf4il33vbkfJyrzLVbrglaaETehyTreBSt+7K7c6eZFmlWBxyFhb8QmG53tAMHjo 9A8hK5RqzXNl6UGb+aHrz3o1OoeY2Qi/m87JHrptd2Cscjtjhi5OKqHdS3euGZ+DDudF vDpFkGp7HmYoSHhDu/i8JDYjJ/9Lj7E5M5UyH79Xjg+64TS9RKsRfayisnySku0cQpbz UtDKoXNGhPG1DtxPSW40RGRHQEKG2ZqIpmm1+0BsfREZ2y4LufrJHNbKls/e8a1bWs3t JqdKSFi/RIalkhdeKVCE8qoaIHmviBIT1IK5Avzg832qRyK/hHnWPb2D5A/j1A1wC+am eBCw== In-Reply-To: <20211025061916.3853623-1-shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: =?UTF-8?q?Michal=20Koutn=C3=BD?= , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Shakeel Butt The function cgroupstats_build extracts cgroup from the kernfs_node's priv pointer which is a RCU pointer. So, there is no need to grab cgroup_mutex. Just get the reference on the cgroup before using and remove the cgroup_mutex altogether. Signed-off-by: Shakeel Butt --- kernel/cgroup/cgroup-v1.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index f6cc5f8484dc..fd14a60379c1 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -698,8 +698,6 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) kernfs_type(kn) != KERNFS_DIR) return -EINVAL; - mutex_lock(&cgroup_mutex); - /* * We aren't being called from kernfs and there's no guarantee on * @kn->priv's validity. For this and css_tryget_online_from_dir(), @@ -707,9 +705,8 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) */ rcu_read_lock(); cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv); - if (!cgrp || cgroup_is_dead(cgrp)) { + if (!cgrp || !cgroup_tryget(cgrp)) { rcu_read_unlock(); - mutex_unlock(&cgroup_mutex); return -ENOENT; } rcu_read_unlock(); @@ -737,7 +734,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) } css_task_iter_end(&it); - mutex_unlock(&cgroup_mutex); + cgroup_put(cgrp); return 0; } -- 2.33.0.1079.g6e70778dc9-goog