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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 88449C3A59B for ; Fri, 30 Aug 2019 15:53:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66735215EA for ; Fri, 30 Aug 2019 15:53:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728246AbfH3PxY (ORCPT ); Fri, 30 Aug 2019 11:53:24 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:3543 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727135AbfH3PxY (ORCPT ); Fri, 30 Aug 2019 11:53:24 -0400 Received: from DGGEMM403-HUB.china.huawei.com (unknown [172.30.72.53]) by Forcepoint Email with ESMTP id 35A7FA282F3B47C6C9FA; Fri, 30 Aug 2019 23:53:12 +0800 (CST) Received: from dggeme762-chm.china.huawei.com (10.3.19.108) by DGGEMM403-HUB.china.huawei.com (10.3.20.211) with Microsoft SMTP Server (TLS) id 14.3.439.0; Fri, 30 Aug 2019 23:53:11 +0800 Received: from architecture4 (10.140.130.215) by dggeme762-chm.china.huawei.com (10.3.19.108) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1591.10; Fri, 30 Aug 2019 23:53:11 +0800 Date: Fri, 30 Aug 2019 23:52:23 +0800 From: Gao Xiang To: Christoph Hellwig CC: Joe Perches , Chao Yu , Dan Carpenter , Greg Kroah-Hartman , , LKML , , Chao Yu , Miao Xie , , Fang Wei Subject: Re: [PATCH v2 2/7] erofs: some marcos are much more readable as a function Message-ID: <20190830155223.GA69026@architecture4> References: <20190830030040.10599-1-gaoxiang25@huawei.com> <20190830030040.10599-2-gaoxiang25@huawei.com> <5b2ecf5cec1a6aa3834e9af41886a7fcb18ae86a.camel@perches.com> <20190830154551.GA11571@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20190830154551.GA11571@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [10.140.130.215] X-ClientProxiedBy: dggeme712-chm.china.huawei.com (10.1.199.108) To dggeme762-chm.china.huawei.com (10.3.19.108) X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christoph, On Fri, Aug 30, 2019 at 08:45:51AM -0700, Christoph Hellwig wrote: > On Thu, Aug 29, 2019 at 08:16:27PM -0700, Joe Perches wrote: > > > - sizeof(__u32) * ((__count) - 1); }) > > > +static inline unsigned int erofs_xattr_ibody_size(__le16 d_icount) > > > +{ > > > + unsigned int icount = le16_to_cpu(d_icount); > > > + > > > + if (!icount) > > > + return 0; > > > + > > > + return sizeof(struct erofs_xattr_ibody_header) + > > > + sizeof(__u32) * (icount - 1); > > > > Maybe use struct_size()? > > Declaring a variable that is only used for struct_size is rather ugly. > But while we are nitpicking: you don't need to byteswap to check for 0, > so the local variable could be avoided. > > Also what is that magic -1 for? Normally we use that for the > deprecated style where a variable size array is declared using > varname[1], but that doesn't seem to be the case for erofs. I have to explain more about this (sorry about my awkward English) here i_xattr_icount is to represent the size of xattr field of erofs, as follows: 0 - no xattr at all (no erofs_xattr_ibody_header) _______ | inode | |_______| 1 - a erofs_xattr_ibody_header (12 byte) + 4-byte (shared + inline) xattrs 2 - a erofs_xattr_ibody_header (12 byte) + 8-byte (shared + inline) xattrs .... (that is the magic -1 means...) In order to keep the number continuously, actually the content could be an array of shared_xattr_id and an inline xattr combination (struct erofs_xattr_entry + name + value) Thanks, Gao Xiang