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=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 B1C9DC3F2CD for ; Tue, 3 Mar 2020 09:45:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B38221739 for ; Tue, 3 Mar 2020 09:45:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ellerman.id.au header.i=@ellerman.id.au header.b="FvTeVOpG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727822AbgCCJp1 (ORCPT ); Tue, 3 Mar 2020 04:45:27 -0500 Received: from ozlabs.org ([203.11.71.1]:55693 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727738AbgCCJp1 (ORCPT ); Tue, 3 Mar 2020 04:45:27 -0500 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 48WsZD4YDzz9sRN; Tue, 3 Mar 2020 20:45:24 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ellerman.id.au; s=201909; t=1583228724; bh=Wo5bQeKUPhAri+IWkOD5PZEI0f97+gdXT92XXJeUOaY=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=FvTeVOpG1HL369swVAGKwuZdqRj3BH9QUPT5UA/ZR7E5xAuX9Esj/AXStB1Ufwp/o QjA2R3+CuKGBGHH3MqixMIW38v3h0eUpP5sxQQWxA0p6yPZdapZMWwxaXwGjaWVSHt zK0R/sxz/ci+xcCJvVi3zbBt0Rrv0T/jAZ7jt1PXRDPS3OHKqT7hY/Rl0cxnygArbk zv2DhYTyCO9oVaS+AhI3jBya3LfjhHJw2ZG/CuvBjZ3gAJ2zpo00YD2XR3nIFgpgJr ot9rVNJKqYM69dM4qti8YMpiXwlagy+JcXiObIoaRe3hmrALaOVbi2xxlyDej5Ppmp pZb/DytQtWifA== From: Michael Ellerman To: Greg Kroah-Hartman 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 In-Reply-To: <20200303085039.GA1323622@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> Date: Tue, 03 Mar 2020 20:45:23 +1100 Message-ID: <87d09tsrf0.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; } cheers