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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 010E6C64EB0 for ; Tue, 9 Oct 2018 07:00:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC3B02089D for ; Tue, 9 Oct 2018 07:00:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC3B02089D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726488AbeJIOPi (ORCPT ); Tue, 9 Oct 2018 10:15:38 -0400 Received: from ozlabs.org ([203.11.71.1]:60681 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725835AbeJIOPi (ORCPT ); Tue, 9 Oct 2018 10:15:38 -0400 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPSA id 42Tp5P1wtPz9s47; Tue, 9 Oct 2018 18:00:08 +1100 (AEDT) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au From: Michael Ellerman To: YueHaibing , benh@kernel.crashing.org, paulus@samba.org, nfont@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, YueHaibing Subject: Re: [PATCH v2 -next] powerpc/pseries/memory-hotplug: Fix return value type of find_aa_index In-Reply-To: <20181004094113.5492-1-yuehaibing@huawei.com> References: <20181004094113.5492-1-yuehaibing@huawei.com> Date: Tue, 09 Oct 2018 18:00:08 +1100 Message-ID: <871s8z38qv.fsf@concordia.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 YueHaibing writes: > 'aa_index' is defined as an unsigned value, but find_aa_index > may return -1 when dlpar_clone_property fails. So we use an rc > value to track the validation of finding the aa_index instead > of the 'aa_index' value itself > > Fixes: c05a5a40969e ("powerpc/pseries: Dynamic add entires to associativity lookup array") > Signed-off-by: YueHaibing > --- > v2: use 'rc' track the validation of aa_index Thanks for sending a v2, some more comments ... > diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c > index 9a15d39..796e68b 100644 > --- a/arch/powerpc/platforms/pseries/hotplug-memory.c > +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c > @@ -101,13 +101,12 @@ static struct property *dlpar_clone_property(struct property *prop, > return new_prop; > } > > -static u32 find_aa_index(struct device_node *dr_node, > - struct property *ala_prop, const u32 *lmb_assoc) > +static int find_aa_index(struct device_node *dr_node, struct property *ala_prop, > + const u32 *lmb_assoc, u32 *aa_index) > { > u32 *assoc_arrays; > - u32 aa_index; > int aa_arrays, aa_array_entries, aa_array_sz; > - int i, index; > + int i, index, rc = -1; It's preferable to leave rc uninitialised until we actually need to initialise it, that gives the compiler the chance to warn us if we use it inadvertently before that. > > /* > * The ibm,associativity-lookup-arrays property is defined to be > @@ -121,18 +120,18 @@ static u32 find_aa_index(struct device_node *dr_node, > aa_array_entries = be32_to_cpu(assoc_arrays[1]); > aa_array_sz = aa_array_entries * sizeof(u32); > > - aa_index = -1; So that would be here: rc = -1; But .. > for (i = 0; i < aa_arrays; i++) { > index = (i * aa_array_entries) + 2; > > if (memcmp(&assoc_arrays[index], &lmb_assoc[1], aa_array_sz)) > continue; > > - aa_index = i; > + *aa_index = i; > + rc = 0; > break; > } The 'rc' variable is basically a boolean now, it means "we found something". And all we do with it in the found case (rc = 0) is test it below and return. So can't we just return directly in the for loop above, rather than breaking? In which case we don't need the rc variable at all. And the whole function may as well return bool, rather than int. Does that make sense? cheers > - if (aa_index == -1) { > + if (rc == -1) { > struct property *new_prop; > u32 new_prop_size; > > @@ -157,10 +156,11 @@ static u32 find_aa_index(struct device_node *dr_node, > * number of entries - 1 since we added its associativity > * to the end of the lookup array. > */ > - aa_index = be32_to_cpu(assoc_arrays[0]) - 1; > + *aa_index = be32_to_cpu(assoc_arrays[0]) - 1; > + rc = 0; > } > > - return aa_index; > + return rc; > } > > static int update_lmb_associativity_index(struct drmem_lmb *lmb)