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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 02239C3F2C6 for ; Tue, 3 Mar 2020 09:58:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE7DB214D8 for ; Tue, 3 Mar 2020 09:58:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583229536; bh=4mY+eBzqEAqUVgHJBB+37VWPwTk5qHToh5K0kzSRiGQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=L6vG/JtJR64fOxVi5WJNfl4DpvezAINwEE3DpVANwNAZ6q1fiww/2LCjcBJsG5lzU CnP12tVGwbqz/TWnBGPNHawPtO8LhrbYUh51sFPtUpkiu7r4p4J1/lkb0hrzareONu kAL8uV+DTHuL2QKHxsEpcotZqDCqUAjyzEMuT4xk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728381AbgCCJ6z (ORCPT ); Tue, 3 Mar 2020 04:58:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:51194 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727818AbgCCJ6z (ORCPT ); Tue, 3 Mar 2020 04:58:55 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.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 C103020866; Tue, 3 Mar 2020 09:58:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583229533; bh=4mY+eBzqEAqUVgHJBB+37VWPwTk5qHToh5K0kzSRiGQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RvLaQssSdeUj4EIJz4bsPbTB5s6RWxPx2KmQIq3H4ZfSpkCu4UU8sXwU5FecLG1jM LwRTmFo5dE5dQuvB90IyP711StWZRPZbaOQrDHv1KcqLYhQ8MVM7ycOqXZgJvmQ+2T if72tEA5TIdvg5XYBmUAu5z0dyfPhVTEm/UajgPk= Date: Tue, 3 Mar 2020 10:58:49 +0100 From: Greg Kroah-Hartman To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Paul Mackerras , Benjamin Herrenschmidt , kvm-ppc@vger.kernel.org Subject: Re: [PATCH 2/6] powerpc: kvm: no need to check return value of debugfs_create functions Message-ID: <20200303095849.GA1399072@kroah.com> References: <20200209105901.1620958-1-gregkh@linuxfoundation.org> <20200209105901.1620958-2-gregkh@linuxfoundation.org> <87imjlswxc.fsf@mpe.ellerman.id.au> <20200303085039.GA1323622@kroah.com> <87d09tsrf0.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87d09tsrf0.fsf@mpe.ellerman.id.au> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 03, 2020 at 08:45:23PM +1100, Michael Ellerman wrote: > Greg Kroah-Hartman writes: > > On Tue, Mar 03, 2020 at 06:46:23PM +1100, Michael Ellerman wrote: > >> Greg Kroah-Hartman writes: > >> > When calling debugfs functions, there is no need to ever check the > >> > return value. The function can work or not, but the code logic should > >> > never do something different based on this. > >> > >> Except it does need to do something different, if the file was created > >> it needs to be removed in the remove path. > >> > >> > diff --git a/arch/powerpc/kvm/timing.c b/arch/powerpc/kvm/timing.c > >> > index bfe4f106cffc..8e4791c6f2af 100644 > >> > --- a/arch/powerpc/kvm/timing.c > >> > +++ b/arch/powerpc/kvm/timing.c > >> > @@ -207,19 +207,12 @@ static const struct file_operations kvmppc_exit_timing_fops = { > >> > void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id) > >> > { > >> > static char dbg_fname[50]; > >> > - struct dentry *debugfs_file; > >> > > >> > snprintf(dbg_fname, sizeof(dbg_fname), "vm%u_vcpu%u_timing", > >> > current->pid, id); > >> > - debugfs_file = debugfs_create_file(dbg_fname, 0666, > >> > - kvm_debugfs_dir, vcpu, > >> > - &kvmppc_exit_timing_fops); > >> > - > >> > - if (!debugfs_file) { > >> > - printk(KERN_ERR"%s: error creating debugfs file %s\n", > >> > - __func__, dbg_fname); > >> > - return; > >> > - } > >> > + debugfs_create_file(dbg_fname, 0666, kvm_debugfs_dir, vcpu, > >> > + &kvmppc_exit_timing_fops); > >> > + > >> > > >> > vcpu->arch.debugfs_exit_timing = debugfs_file; > > > > Ugh, you are right, how did I miss that? How is 0-day missing this? > > It's been in my tree for a long time, odd. > > This code isn't enabled by default, or in any defconfig. So it's only > allmodconfig that would trip it, I guess 0-day isn't doing powerpc > allmodconfig builds. > > >> I squashed this in, which seems to work: > ... > >> > >> void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu) > >> { > >> - if (vcpu->arch.debugfs_exit_timing) { > >> + if (!IS_ERR_OR_NULL(vcpu->arch.debugfs_exit_timing)) { > >> debugfs_remove(vcpu->arch.debugfs_exit_timing); > >> vcpu->arch.debugfs_exit_timing = NULL; > >> } > > > > No, this can just be: > > debugfs_remove(vcpu->arch.debugfs_exit_timing); > > > > No need to check anything, just call it and the debugfs code can handle > > it just fine. > > Oh duh, of course, I should have checked. > > I'd still like to NULL out the debugfs_exit_timing member, so I'll do: > > void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu) > { > debugfs_remove(vcpu->arch.debugfs_exit_timing); > vcpu->arch.debugfs_exit_timing = NULL; > } Fair enough, but I doubt it ever matters :) Thanks for the fixups, sorry for sending a broken patch, my fault. greg k-h