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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT 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 19454C28CC0 for ; Wed, 29 May 2019 15:11:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED31923B8C for ; Wed, 29 May 2019 15:11:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726653AbfE2PLk (ORCPT ); Wed, 29 May 2019 11:11:40 -0400 Received: from foss.arm.com ([217.140.101.70]:47848 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725936AbfE2PLj (ORCPT ); Wed, 29 May 2019 11:11:39 -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 19717341; Wed, 29 May 2019 08:11:39 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B701F3F5AF; Wed, 29 May 2019 08:11:37 -0700 (PDT) Date: Wed, 29 May 2019 16:11:35 +0100 From: Mark Rutland To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , James Morse , Andrey Konovalov Subject: Re: [PATCH 4/4] arm64/mm: Drop vm_fault_t argument from __do_page_fault() Message-ID: <20190529151134.GH31777@lakrids.cambridge.arm.com> References: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> <1559133285-27986-5-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1559133285-27986-5-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 29, 2019 at 06:04:45PM +0530, Anshuman Khandual wrote: > __do_page_fault() is over complicated with multiple goto statements. This > cleans up code flow and while there drops the vm_fault_t argument. > Signed-off-by: Anshuman Khandual > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Mark Rutland > Cc: James Morse > Cc: Andrey Konovalov > --- > arch/arm64/mm/fault.c | 38 ++++++++++++++++---------------------- > 1 file changed, 16 insertions(+), 22 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 170c71f..a53a30e 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -397,37 +397,31 @@ 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. > + * Check if the VMA has got the required permssion with respect > + * to the access fault here. > */ We already had a perfectly good comment for this check: /* * Check that the permissions on the VMA allow for the fault which * occurred. */ ... so please keep that and minimize the diff. > -good_area: > + if (!(vma->vm_flags & vm_flags)) > + return VM_FAULT_BADACCESS; > + > /* > - * Check that the permissions on the VMA allow for the fault which > - * occurred. > + * There is a valid VMA for this access. But before proceeding > + * make sure that it has required flags if there is an attempt > + * to expand the stack downwards. > */ I think we can drop this comment, given we didn't have it previously. > - if (!(vma->vm_flags & vm_flags)) { > - fault = VM_FAULT_BADACCESS; > - goto out; > - } > + 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 can drop the line space between these two if statements. > + } > return handle_mm_fault(vma, addr & PAGE_MASK, mm_flags); > - > -check_stack: > - if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) > - goto good_area; > -out: > - return fault; We used to check the stack before the checknig the rest of the vm_flags, so this changes the precedence of the VM_FAULT_BADMAP and VM_FAULT_BADACCESS return codes. Please check the stack before checking the other vm_flags. Otherwise, this looks like a nice cleanup -- the old control flow was hideous. Thanks, Mark. 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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 7EE2EC28CC0 for ; Wed, 29 May 2019 15:11:47 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 54A6D23BBA for ; Wed, 29 May 2019 15:11:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="LKj7zMh5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 54A6D23BBA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=vM6U3nFyBeZMU77Kc+Maz8rJ6mdJepleoRKA6zHFkv0=; b=LKj7zMh5f5RSuk KSHhhqIB7xag5yTWNKgxuWvNaOPkyakkxF//4k97N0Cbf0mXQEb1jZ5FsD51hykYEIvbVlKVxj5h6 l3SzY6gZYcsnRUSWtnzVmKj6cWQrhn+R6TT3Um/RKLBWmgqDlxhEMVSkSHeAiZ3rNB2S/hlH+yAyO rErhPVQffkOF5CGLwUe8yu2y8Ha4xtcR5jnrI2mVstUPUtL1jzw7a22rIV4uamOkNedGQzCFrk/Ol dFLN+kKO7pM+inOQnK5S8EGdZlU3ig4yHmA6ooIE4I1H32Gkd+cAKn7vMC8rXKlCBq/GmuKkpURsb zOKS8YDNkV0HMjLAYqaQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hW0Ew-0002hR-Aj; Wed, 29 May 2019 15:11:42 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hW0Et-0002h7-A5 for linux-arm-kernel@lists.infradead.org; Wed, 29 May 2019 15:11:40 +0000 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 19717341; Wed, 29 May 2019 08:11:39 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B701F3F5AF; Wed, 29 May 2019 08:11:37 -0700 (PDT) Date: Wed, 29 May 2019 16:11:35 +0100 From: Mark Rutland To: Anshuman Khandual Subject: Re: [PATCH 4/4] arm64/mm: Drop vm_fault_t argument from __do_page_fault() Message-ID: <20190529151134.GH31777@lakrids.cambridge.arm.com> References: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> <1559133285-27986-5-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1559133285-27986-5-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190529_081139_358681_F6FFC1FD X-CRM114-Status: GOOD ( 23.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrey Konovalov , Will Deacon , linux-kernel@vger.kernel.org, James Morse , Catalin Marinas , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 29, 2019 at 06:04:45PM +0530, Anshuman Khandual wrote: > __do_page_fault() is over complicated with multiple goto statements. This > cleans up code flow and while there drops the vm_fault_t argument. > Signed-off-by: Anshuman Khandual > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Mark Rutland > Cc: James Morse > Cc: Andrey Konovalov > --- > arch/arm64/mm/fault.c | 38 ++++++++++++++++---------------------- > 1 file changed, 16 insertions(+), 22 deletions(-) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 170c71f..a53a30e 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -397,37 +397,31 @@ 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. > + * Check if the VMA has got the required permssion with respect > + * to the access fault here. > */ We already had a perfectly good comment for this check: /* * Check that the permissions on the VMA allow for the fault which * occurred. */ ... so please keep that and minimize the diff. > -good_area: > + if (!(vma->vm_flags & vm_flags)) > + return VM_FAULT_BADACCESS; > + > /* > - * Check that the permissions on the VMA allow for the fault which > - * occurred. > + * There is a valid VMA for this access. But before proceeding > + * make sure that it has required flags if there is an attempt > + * to expand the stack downwards. > */ I think we can drop this comment, given we didn't have it previously. > - if (!(vma->vm_flags & vm_flags)) { > - fault = VM_FAULT_BADACCESS; > - goto out; > - } > + 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 can drop the line space between these two if statements. > + } > return handle_mm_fault(vma, addr & PAGE_MASK, mm_flags); > - > -check_stack: > - if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) > - goto good_area; > -out: > - return fault; We used to check the stack before the checknig the rest of the vm_flags, so this changes the precedence of the VM_FAULT_BADMAP and VM_FAULT_BADACCESS return codes. Please check the stack before checking the other vm_flags. Otherwise, this looks like a nice cleanup -- the old control flow was hideous. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel