From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH cgroup/for-4.13-fixes] cgroup: create dfl_root files on subsys registration Date: Tue, 18 Jul 2017 17:57:46 -0400 Message-ID: <20170718215746.GG3365493@devbig577.frc2.facebook.com> References: <1500406336-29512-1-git-send-email-longman@redhat.com> <20170718195148.GC3365493@devbig577.frc2.facebook.com> <539870d2-8b85-2f54-61bd-4ba068e75ce0@redhat.com> <20170718201229.GD3365493@devbig577.frc2.facebook.com> <255cc198-2c10-af76-98ca-086807d11540@redhat.com> <20170718205009.GE3365493@devbig577.frc2.facebook.com> <20170718210658.GF3365493@devbig577.frc2.facebook.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=tEebydgxZIPI63c7/CldSstE6qd+9pLl/Ru4YY7CKcs=; b=D2FB/KP5fo0HvErKeJAWTstna7jBbavpDcbMxEH3GRPwKivJrw5KUuwBvYtZaA5gHy JciWng129CYVE8Hxj9iaNNmd6fVCFrT1FkfTCQeoN4bShX1H1UOr1AZGqcaIEuYEFMmU 49fw8XaqZ/yhrF6vot2SSO3cUPU5zA11H/iS0WFrMd3mvECwyTkjpfo19x5zlYHwwIV2 93b1p6PiZpCOfQLp7RIm6CHkl7/BoJRiVgR5hQsS3zrAFBLTt3cVI/FLChr3f813BDlK 9ixRqrg1lv8GQniYivu4d30ZgNmSarfZT9GFTCmuvy8MjVgwEXm57d37+xfQPAy9Nd7T Ia8Q== Content-Disposition: inline In-Reply-To: <20170718210658.GF3365493@devbig577.frc2.facebook.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Waiman Long Cc: Li Zefan , Johannes Weiner , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On subsystem registration, css_populate_dir() is not called on the new root css, so the interface files for the subsystem on cgrp_dfl_root aren't created on registration. This is a residue from the days when cgrp_dfl_root was used only as the parking spot for unused subsystems, which no longer is true as it's used as the root for cgroup2. This is often fine as later operations tend to create them as a part of mount (cgroup1) or subtree_control operations (cgroup2); however, it's not difficult to mount cgroup2 with the controller interface files missing as Waiman found out. Fix it by invoking css_populate_dir() on the root css on subsys registration. Signed-off-by: Tejun Heo Reported-by: Waiman Long Cc: stable@vger.kernel.org # v4.5+ --- Hello, Waiman. Can you please verify that this fixes the bug? Thanks. kernel/cgroup/cgroup.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 620794a..9d33108 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4669,6 +4669,10 @@ int __init cgroup_init(void) if (ss->bind) ss->bind(init_css_set.subsys[ssid]); + + mutex_lock(&cgroup_mutex); + css_populate_dir(init_css_set.subsys[ssid]); + mutex_unlock(&cgroup_mutex); } /* init_css_set.subsys[] has been updated, re-hash */