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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 1B2C4C282D7 for ; Wed, 30 Jan 2019 18:14:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF29020870 for ; Wed, 30 Jan 2019 18:14:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="rli5gtMI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732891AbfA3SOa (ORCPT ); Wed, 30 Jan 2019 13:14:30 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:19209 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727402AbfA3SO3 (ORCPT ); Wed, 30 Jan 2019 13:14:29 -0500 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 30 Jan 2019 10:14:01 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Wed, 30 Jan 2019 10:14:29 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Wed, 30 Jan 2019 10:14:29 -0800 Received: from [10.110.48.28] (172.20.13.39) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 30 Jan 2019 18:14:28 +0000 Subject: Re: [v3 PATCH] mm: ksm: do not block on page lock when searching stable tree To: Yang Shi , , , , CC: , References: <1548793753-62377-1-git-send-email-yang.shi@linux.alibaba.com> <82ba1395-baab-3b95-a3f7-47e219551881@nvidia.com> <7cf16cfb-3190-dfbd-ce72-92a94d9277f5@linux.alibaba.com> From: John Hubbard Message-ID: <9bf60825-286f-d46c-b6d5-ee8bfffaaa48@nvidia.com> Date: Wed, 30 Jan 2019 10:14:28 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <7cf16cfb-3190-dfbd-ce72-92a94d9277f5@linux.alibaba.com> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL103.nvidia.com (172.20.187.11) To HQMAIL101.nvidia.com (172.20.187.10) Content-Type: text/plain; charset="utf-8" Content-Language: en-US-large Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1548872041; bh=vRFnZGny9hUnD9eny/611Mn7d12FxGlSSC/uexCXw2o=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=rli5gtMIAFpKXWV/KbzHzT5AIrb3FbVc7sMVRw+V8zZHiJE4y6MvNz1NiK9Hnx7Sl Zplal1p/QflKbl/jb6FEsKs0W2mVCTgC5XOWGn1cyT8phMAQHCe1ayZzol5rieXEzE ZKkGLyBNdeIccVbLZuT9iWpZKbJ0sLCH7SctfnEOil4gGOd6l1oJnEHiuel2EkjHlT eVlthmdkOgV2SM7Ho/uuOKn7iTbZnrOxTZphLT5lFm/CXapXf9RORKmH0ci3oHZAfY QXv/a+8oXTi255Avi9r7XdMI4bwhG3neFpS3GtoMes/ugRQUmYKQ9iCt+aCNA1vqxJ l8cRsAGO8TXVg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/30/19 9:47 AM, Yang Shi wrote: [...] >>> @@ -1673,7 +1688,12 @@ static struct page *stable_tree_search(struct pa= ge *page) >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 * It would be more elegant to return stable_node >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 * than kpage, but that involves more changes. >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 */ >>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 tre= e_page =3D get_ksm_page(stable_node_dup, true); >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 tre= e_page =3D get_ksm_page(stable_node_dup, >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= GET_KSM_PAGE_TRYLOCK); >>> + >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if = (PTR_ERR(tree_page) =3D=3D -EBUSY) >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 return ERR_PTR(-EBUSY); >> >> or just: >> >> =C2=A0=C2=A0=C2=A0=C2=A0if (PTR_ERR(tree_page) =3D=3D -EBUSY) >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return tree_page; >> >> right? >=20 > Either looks fine to me. Returning errno may look more explicit? Anyway I= really don't have preference. Yes, either one is fine. I like to see less code on the screen, all else be= ing equal, but it's an extremely minor point, and sometimes being explicit instead is = better anyway. thanks, --=20 John Hubbard NVIDIA