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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 6E27EC00319 for ; Thu, 21 Feb 2019 09:10:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D0C821734 for ; Thu, 21 Feb 2019 09:10:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550740228; bh=Zc/gh5XVtsFlrscEHZAid4fIIgkXtpwjwzxteWVCRis=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Ckj7BHKhiYm8pgqfKhmvTBJpIIpJVqe4yvmklumkhwApzC/pzZrmM2zNK5CuQn0U8 nL3oCiQ82J9fKR4TqgweoyfpZdSgmaZ/hJE6PiX0lK/UTbW0nKqwcY2l9Z4LCOQqUI S1Rr33kx70CXvfjnNvzYhwqWFoBr0ohXoSkl3dnI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727515AbfBUJK0 (ORCPT ); Thu, 21 Feb 2019 04:10:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:59876 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727475AbfBUJK0 (ORCPT ); Thu, 21 Feb 2019 04:10:26 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 34CC32086C; Thu, 21 Feb 2019 09:10:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550740225; bh=Zc/gh5XVtsFlrscEHZAid4fIIgkXtpwjwzxteWVCRis=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gUtZMWHCxaCg01+EOD2xmRqaLCjOXO6snMc1iP5S/6gwLH8mvp5SlZ3ToAxgBtqU0 12ZALVGdjQTcTrZ9NrfVV1OrBK5gHbM7XE+37+0Ox/nL6Mq7jyNXwDthphL680FPWe A+cAitJLZSZFNgXTiscikl6jCJLVsxMUhDWWnSh4= Date: Thu, 21 Feb 2019 10:10:22 +0100 From: Greg KH To: Michal Hocko Cc: Yue Hu , akpm@linux-foundation.org, rientjes@google.com, joe@perches.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, huyue2@yulong.com Subject: Re: [PATCH] mm/cma_debug: Check for null tmp in cma_debugfs_add_one() Message-ID: <20190221091022.GB11118@kroah.com> References: <20190221040130.8940-1-zbestahu@gmail.com> <20190221040130.8940-2-zbestahu@gmail.com> <20190221082309.GG4525@dhcp22.suse.cz> <20190221083624.GD6397@kroah.com> <20190221084525.GI4525@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190221084525.GI4525@dhcp22.suse.cz> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 21, 2019 at 09:45:25AM +0100, Michal Hocko wrote: > On Thu 21-02-19 09:36:24, Greg KH wrote: > > On Thu, Feb 21, 2019 at 09:23:09AM +0100, Michal Hocko wrote: > > > On Thu 21-02-19 12:01:30, Yue Hu wrote: > > > > From: Yue Hu > > > > > > > > If debugfs_create_dir() failed, the following debugfs_create_file() > > > > will be meanless since it depends on non-NULL tmp dentry and it will > > > > only waste CPU resource. > > > > > > The file will be created in the debugfs root. But, more importantly. > > > Greg (CCed now) is working on removing the failure paths because he > > > believes they do not really matter for debugfs and they make code more > > > ugly. More importantly a check for NULL is not correct because you > > > get ERR_PTR after recent changes IIRC. > > > > > > > > > > > Signed-off-by: Yue Hu > > > > --- > > > > mm/cma_debug.c | 2 ++ > > > > 1 file changed, 2 insertions(+) > > > > > > > > diff --git a/mm/cma_debug.c b/mm/cma_debug.c > > > > index 2c2c869..3e9d984 100644 > > > > --- a/mm/cma_debug.c > > > > +++ b/mm/cma_debug.c > > > > @@ -169,6 +169,8 @@ static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry) > > > > scnprintf(name, sizeof(name), "cma-%s", cma->name); > > > > > > > > tmp = debugfs_create_dir(name, root_dentry); > > > > + if (!tmp) > > > > + return; > > > > Ick, yes, this patch isn't ok, I've been doing lots of work to rip these > > checks out :) > > Btw. I believe that it would help to clarify this stance in the > kerneldoc otherwise these checks will be returning back because the > general kernel development attitude is to check for errors. As I've said > previously debugfs being different is ugly but decision is yours. Yes, I'll be doing that, thanks for the reminder. greg k-h