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 5F14DC3F2C6 for ; Tue, 3 Mar 2020 10:32:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 318C020838 for ; Tue, 3 Mar 2020 10:32:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ellerman.id.au header.i=@ellerman.id.au header.b="eiOxIkKN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728657AbgCCKcX (ORCPT ); Tue, 3 Mar 2020 05:32:23 -0500 Received: from bilbo.ozlabs.org ([203.11.71.1]:60365 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728372AbgCCKcW (ORCPT ); Tue, 3 Mar 2020 05:32:22 -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 48WtcN0RCtz9sPg; Tue, 3 Mar 2020 21:32:20 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ellerman.id.au; s=201909; t=1583231540; bh=plIVQelLQN+Lhv6LVRXDSOs7Mt1qf+ql5n8cFWM5qC8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=eiOxIkKNxkhy8BuTzjl2C8S7V8FWoaXiEldT4NoOUCn0HUgadrF25e6taTW9pGf1w 5I64che4K4w228Sj/uxYo0Lw7zi0NJjb+VsYtmOZwU+/3dWjkAe1KfsvGDFG6m/UzB KOq6cXj4eEXSpsYkJZof2d1KTxZXD8vGFxOjR3LtMhC9R1Bw2S9CzzZXBjXFVje9UQ 1O9maQhH6RCyv5+xSdQjDZmwIHeFuU5Fkodz+72JYsA+9qrBTZn72OuwphM2O6LJBQ 1PF7WZ2ARePgjBcFQGFGN6d8fq3RlFSulZrELavsjYJSYO0TEBe+MUaH6ofC8U3KmR m8X8oF93qTwJw== 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: <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> <20200303095849.GA1399072@kroah.com> Date: Tue, 03 Mar 2020 21:32:19 +1100 Message-ID: <874kv5sp8s.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 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 :) Yeah, but I'm paranoid and I have no way to test this code :) > Thanks for the fixups, sorry for sending a broken patch, my fault. No worries, we have too many CONFIG options. cheers