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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 CD6EFC04AB5 for ; Thu, 6 Jun 2019 04:53:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A3C8920868 for ; Thu, 6 Jun 2019 04:53:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726530AbfFFExs (ORCPT ); Thu, 6 Jun 2019 00:53:48 -0400 Received: from foss.arm.com ([217.140.101.70]:40720 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725766AbfFFExs (ORCPT ); Thu, 6 Jun 2019 00:53:48 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9BA9280D; Wed, 5 Jun 2019 21:53:47 -0700 (PDT) Received: from [10.162.43.122] (p8cg001049571a15.blr.arm.com [10.162.43.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 37FC13F690; Wed, 5 Jun 2019 21:53:44 -0700 (PDT) Subject: Re: [PATCH V2 4/4] arm64/mm: Drop local variable vm_fault_t from __do_page_fault() To: Catalin Marinas Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Will Deacon , Mark Rutland , James Morse , Andrey Konovalov , Christoph Hellwig References: <1559544085-7502-1-git-send-email-anshuman.khandual@arm.com> <1559544085-7502-5-git-send-email-anshuman.khandual@arm.com> <20190604145612.GM6610@arrakis.emea.arm.com> From: Anshuman Khandual Message-ID: <1d89177a-e7af-ac4e-1a04-e8b750c2c768@arm.com> Date: Thu, 6 Jun 2019 10:24:01 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190604145612.GM6610@arrakis.emea.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/04/2019 08:26 PM, Catalin Marinas wrote: > On Mon, Jun 03, 2019 at 12:11:25PM +0530, Anshuman Khandual wrote: >> __do_page_fault() is over complicated with multiple goto statements. This >> cleans up the code flow and while there drops local variable vm_fault_t. > > I'd change the subject as well here to something like refactor or > simplify __do_page_fault(). Sure. > >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index 4bb65f3..41fa905 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -397,37 +397,29 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re >> static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr, >> unsigned int mm_flags, unsigned long vm_flags) >> { >> - struct vm_area_struct *vma; >> - vm_fault_t fault; >> + struct vm_area_struct *vma = find_vma(mm, addr); >> >> - vma = find_vma(mm, addr); >> - fault = VM_FAULT_BADMAP; >> if (unlikely(!vma)) >> - goto out; >> - if (unlikely(vma->vm_start > addr)) >> - goto check_stack; >> + return VM_FAULT_BADMAP; >> >> /* >> * Ok, we have a good vm_area for this memory access, so we can handle >> * it. >> */ >> -good_area: >> + if (unlikely(vma->vm_start > addr)) { >> + if (!(vma->vm_flags & VM_GROWSDOWN)) >> + return VM_FAULT_BADMAP; >> + if (expand_stack(vma, addr)) >> + return VM_FAULT_BADMAP; >> + } > > You could have a single return here: > > if (unlikely(vma->vm_start > addr) && > (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, addr))) > return VM_FAULT_BADMAP; > > Not sure it's any clearer though. > TBH the proposed one seems clearer as it separates effect (vma->vm_start > addr) from required permission check (vma->vm_flags & VM_GROWSDOWN) and required action (expand_stack(vma, addr)). But I am happy to change as you have mentioned if that is preferred.