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 68EB8C3F2CD for ; Tue, 3 Mar 2020 08:50:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 411A82086A for ; Tue, 3 Mar 2020 08:50:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583225446; bh=eR6LH6mxRiiMpd/1mg6HONvlCCBV3PmOyYycLqHqkdw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=DrMvhlJfeRa7/csQbX8vAsU9MtPYKlX1HQrw8skc0q/iDPNF5+WTkxVAVQl2JGbzA bKlhbWtBmio/MkjG8NZVuDoBm6LwLTRlJ74xfgjy7uQHQUoQOTJLhbGYOlPmjpefXL xV4wqrzK6FwYInwA37YXR7wsbodzk4ctiOJRTbUE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727828AbgCCIup (ORCPT ); Tue, 3 Mar 2020 03:50:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:33744 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727412AbgCCIun (ORCPT ); Tue, 3 Mar 2020 03:50:43 -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 E5FA920873; Tue, 3 Mar 2020 08:50:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583225442; bh=eR6LH6mxRiiMpd/1mg6HONvlCCBV3PmOyYycLqHqkdw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eEDuts2CyWKxUkuRazmkCwT4hZjsAxqrHnv14Uf/LNboVoyo0q8uTK5wcmrqOiCfz d64lQUTg3g5FM9OQUp2chBDAGhbLXbHoANW6G9t4HWgZx/OQxWiIuJky8Iqwupvt4Q ex517U3FK6IIxONywHvdH+C/N1tSRCy/KDMqPNys= Date: Tue, 3 Mar 2020 09:50:39 +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: <20200303085039.GA1323622@kroah.com> References: <20200209105901.1620958-1-gregkh@linuxfoundation.org> <20200209105901.1620958-2-gregkh@linuxfoundation.org> <87imjlswxc.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87imjlswxc.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 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 doesn't build: > > arch/powerpc/kvm/timing.c:217:35: error: 'debugfs_file' undeclared (first use in this function); did you mean 'debugfs_file_put'? > > We can't just drop the assignment, we need the dentry to do the removal: > > void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu) > { > if (vcpu->arch.debugfs_exit_timing) { > debugfs_remove(vcpu->arch.debugfs_exit_timing); > vcpu->arch.debugfs_exit_timing = NULL; > } > } > > > I squashed this in, which seems to work: > > diff --git a/arch/powerpc/kvm/timing.c b/arch/powerpc/kvm/timing.c > index 8e4791c6f2af..5b7a66f86bd5 100644 > --- a/arch/powerpc/kvm/timing.c > +++ b/arch/powerpc/kvm/timing.c > @@ -207,19 +207,19 @@ 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_create_file(dbg_fname, 0666, kvm_debugfs_dir, vcpu, > - &kvmppc_exit_timing_fops); > - > + debugfs_file = debugfs_create_file(dbg_fname, 0666, kvm_debugfs_dir, > + vcpu, &kvmppc_exit_timing_fops); > > vcpu->arch.debugfs_exit_timing = debugfs_file; That works, yes. > } > > 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. thanks, greg k-h