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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9548AC2D0E4 for ; Fri, 20 Nov 2020 16:14:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05D762240B for ; Fri, 20 Nov 2020 16:14:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="R2dKT3/A" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728602AbgKTQOB (ORCPT ); Fri, 20 Nov 2020 11:14:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48486 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728296AbgKTQOA (ORCPT ); Fri, 20 Nov 2020 11:14:00 -0500 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 578BCC0613CF for ; Fri, 20 Nov 2020 08:14:00 -0800 (PST) Received: from zn.tnic (p200300ec2f11ba002f58e87ff3ef848f.dip0.t-ipconnect.de [IPv6:2003:ec:2f11:ba00:2f58:e87f:f3ef:848f]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 655451EC04E4; Fri, 20 Nov 2020 17:13:58 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1605888838; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=KtO9yaqvZcz3NUWGPTgeRgf/kR7pds6O5UFlAwADpkQ=; b=R2dKT3/AWv3hTfmPbhgbFl4GN/PVNtgFKLvveM8PAa+A2co4QD2tc05rD+i7SYWmlVWbTL /Wis3G5l9fyaCChzuQ+aGwkE3C5MQXmZA4Yt1NORLtmx/QXW+KAya9Du9m7b+XF+KVcf30 jOSl2oG4hdyoHAIX35TOsB9p81q0/s8= Date: Fri, 20 Nov 2020 17:13:51 +0100 From: Borislav Petkov To: Xiaochen Shen Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, tony.luck@intel.com, fenghua.yu@intel.com, reinette.chatre@intel.com, willemb@google.com, x86@kernel.org, linux-kernel@vger.kernel.org, pei.p.jia@intel.com Subject: Re: [PATCH 1/3] x86/resctrl: Remove superfluous kernfs_get() calls to prevent refcount leak Message-ID: <20201120161351.GC712@zn.tnic> References: <1604084530-31048-1-git-send-email-xiaochen.shen> <1604084638-31197-1-git-send-email-xiaochen.shen@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1604084638-31197-1-git-send-email-xiaochen.shen@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 31, 2020 at 03:03:58AM +0800, Xiaochen Shen wrote: > Willem reported growing of kernfs_node_cache entries in slabtop when > repeatedly creating and removing resctrl subdirectories as well as when > repeatedly mounting and unmounting resctrl filesystem. > > On resource group (control as well as monitoring) creation via a mkdir > an extra kernfs_node reference is obtained to ensure that the rdtgroup > structure remains accessible for the rdtgroup_kn_unlock() calls where it > is removed on deletion. The kernfs_node reference count is dropped by > kernfs_put() in rdtgroup_kn_unlock(). > > With the above explaining the need for one kernfs_get()/kernfs_put() > pair in resctrl there are more places where a kernfs_node reference is > obtained without a corresponding release. The excessive amount of > reference count on kernfs nodes will never be dropped to 0 and the > kernfs nodes will never be freed in the call paths of rmdir and umount. > It leads to reference count leak and kernfs_node_cache memory leak. > > Remove the superfluous kernfs_get() calls and expand the existing > comments surrounding the remaining kernfs_get()/kernfs_put() pair that > remains in use. > > Superfluous kernfs_get() calls are removed from two areas: > > (1) In call paths of mount and mkdir, when kernfs nodes for "info", > "mon_groups" and "mon_data" directories and sub-directories are > created, the reference count of newly created kernfs node is set to 1. > But after kernfs_create_dir() returns, superfluous kernfs_get() are > called to take an additional reference. > > (2) kernfs_get() calls in rmdir call paths. > > Cc: stable@vger.kernel.org > Fixes: 17eafd076291 ("x86/intel_rdt: Split resource group removal in two") > Fixes: 4af4a88e0c92 ("x86/intel_rdt/cqm: Add mount,umount support") > Fixes: f3cbeacaa06e ("x86/intel_rdt/cqm: Add rmdir support") > Fixes: d89b7379015f ("x86/intel_rdt/cqm: Add mon_data") > Fixes: c7d9aac61311 ("x86/intel_rdt/cqm: Add mkdir support for RDT monitoring") > Fixes: 5dc1d5c6bac2 ("x86/intel_rdt: Simplify info and base file lists") > Fixes: 60cf5e101fd4 ("x86/intel_rdt: Add mkdir to resctrl file system") > Fixes: 4e978d06dedb ("x86/intel_rdt: Add "info" files to resctrl file system") Are those 8(!) Fixes tags supposed to list *all* commits which add those wrong kernfs_get() calls? -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette