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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6FAB4C433F5 for ; Mon, 14 Feb 2022 21:21:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230486AbiBNVVv (ORCPT ); Mon, 14 Feb 2022 16:21:51 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:47000 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230474AbiBNVVq (ORCPT ); Mon, 14 Feb 2022 16:21:46 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A66421179BA; Mon, 14 Feb 2022 13:21:37 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 48FD8B8164B; Mon, 14 Feb 2022 19:05:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D599C340E9; Mon, 14 Feb 2022 19:05:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644865550; bh=0qXjvfXrQAWSIg6NzaQiBgbrubEQO78+++XPIl1Kl8c=; h=Date:From:To:Cc:Subject:Reply-To:From; b=rZoYLgMoANJJQhw6AF430YieYpe50cyfmskQ8MsdJR2TZcu266KSWTuNs7Y2aYx1+ CHhdGj1EQKrOcSDoQWpOkCvYMZp7eX5l+P2kFOb4WqgNTAe2qyvKvYN+oJYUavpSoA 67WDlT3swFWpW9jcvLjwBdy9iRGWgWC/KpHRRidnIU57H+7a2Wcaq752/j/c3mPXyE CResbLhsqjSIU3HRY6Qa3/4tRlp7x+43k9hls/xPM1p0NcwNSuWvBIi3es9uoVohyg eZXKWqPy3LREqlQXWp55dVvInVSOnf+l1er9wnatIzNgYZ0LgzEvGA9DE+y5iTY8YI 9hgeJcTGnxV6Q== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 918F35C0388; Mon, 14 Feb 2022 11:05:49 -0800 (PST) Date: Mon, 14 Feb 2022 11:05:49 -0800 From: "Paul E. McKenney" To: clm@fb.com Cc: riel@surriel.com, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-team@fb.com Subject: [PATCH RFC fs/namespace] Make kern_unmount() use synchronize_rcu_expedited() Message-ID: <20220214190549.GA2815154@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Experimental. Not for inclusion. Yet, anyway. Freeing large numbers of namespaces in quick succession can result in a bottleneck on the synchronize_rcu() invoked from kern_unmount(). This patch applies the synchronize_rcu_expedited() hammer to allow further testing and fault isolation. Hey, at least there was no need to change the comment! ;-) Cc: Alexander Viro Cc: Cc: Not-yet-signed-off-by: Paul E. McKenney --- namespace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/namespace.c b/fs/namespace.c index 40b994a29e90d..79c50ad0ade5b 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -4389,7 +4389,7 @@ void kern_unmount(struct vfsmount *mnt) /* release long term mount so mount point can be released */ if (!IS_ERR_OR_NULL(mnt)) { real_mount(mnt)->mnt_ns = NULL; - synchronize_rcu(); /* yecchhh... */ + synchronize_rcu_expedited(); /* yecchhh... */ mntput(mnt); } }