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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54CB2C433EF for ; Wed, 2 Mar 2022 14:04:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242589AbiCBOFO convert rfc822-to-8bit (ORCPT ); Wed, 2 Mar 2022 09:05:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242563AbiCBOE5 (ORCPT ); Wed, 2 Mar 2022 09:04:57 -0500 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 591C985951 for ; Wed, 2 Mar 2022 06:04:13 -0800 (PST) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-196-4Li6Fux3PdyQ14Lo-DMf3A-1; Wed, 02 Mar 2022 14:04:10 +0000 X-MC-Unique: 4Li6Fux3PdyQ14Lo-DMf3A-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.28; Wed, 2 Mar 2022 14:04:06 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.028; Wed, 2 Mar 2022 14:04:06 +0000 From: David Laight To: 'Xiaomeng Tong' , "torvalds@linux-foundation.org" CC: "akpm@linux-foundation.org" , "alsa-devel@alsa-project.org" , "amd-gfx@lists.freedesktop.org" , "andriy.shevchenko@linux.intel.com" , "arnd@arndb.de" , "bcm-kernel-feedback-list@broadcom.com" , "bjohannesmeyer@gmail.com" , "c.giuffrida@vu.nl" , "christian.koenig@amd.com" , "christophe.jaillet@wanadoo.fr" , "dan.carpenter@oracle.com" , "dmaengine@vger.kernel.org" , "drbd-dev@lists.linbit.com" , "dri-devel@lists.freedesktop.org" , "gustavo@embeddedor.com" , "h.j.bos@vu.nl" , "intel-gfx@lists.freedesktop.org" , "intel-wired-lan@lists.osuosl.org" , "jakobkoschel@gmail.com" , "jgg@ziepe.ca" , "keescook@chromium.org" , "kgdb-bugreport@lists.sourceforge.net" , "kvm@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-aspeed@lists.ozlabs.org" , "linux-block@vger.kernel.org" , "linux-cifs@vger.kernel.org" , "linux-crypto@vger.kernel.org" , "linux-f2fs-devel@lists.sourceforge.net" , "linux-fsdevel@vger.kernel.org" , "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-media@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , "linux-pm@vger.kernel.org" , "linux-rdma@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "linux-sgx@vger.kernel.org" , "linux-staging@lists.linux.dev" , "linux-tegra@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "linux1394-devel@lists.sourceforge.net" , "linux@rasmusvillemoes.dk" , "linuxppc-dev@lists.ozlabs.org" , "nathan@kernel.org" , "netdev@vger.kernel.org" , "nouveau@lists.freedesktop.org" , "rppt@kernel.org" , "samba-technical@lists.samba.org" , "tglx@linutronix.de" , "tipc-discussion@lists.sourceforge.net" , "v9fs-developer@lists.sourceforge.net" Subject: RE: [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr Thread-Topic: [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr Thread-Index: AQHYLhg9+DU/OogLf0+tiSFmjztyUKysHu+Q Date: Wed, 2 Mar 2022 14:04:06 +0000 Message-ID: <1077f17e50d34dc2bbfdf4e52a1cb2fd@AcuMS.aculab.com> References: <20220302093106.8402-1-xiam0nd.tong@gmail.com> In-Reply-To: <20220302093106.8402-1-xiam0nd.tong@gmail.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Xiaomeng Tong > Sent: 02 March 2022 09:31 > > On Mon, 28 Feb 2022 16:41:04 -0800, Linus Torvalds > wrote: > > > > But basically to _me_, the important part is that the end result is > > maintainable longer-term. > > I couldn't agree more. And because of that, I stick with the following > approach because it's maintainable longer-term than "type(pos) pos" one: > Implements a new macro for each list_for_each_entry* with _inside suffix. > #define list_for_each_entry_inside(pos, type, head, member) I think that it would be better to make any alternate loop macro just set the variable to NULL on the loop exit. That is easier to code for and the compiler might be persuaded to not redo the test. It also doesn't need an extra variable defined in the for() statement so can be back-ported to older kernels without required declaration in the middle of blocks. OTOH there may be alternative definitions that can be used to get the compiler (or other compiler-like tools) to detect broken code. Even if the definition can't possibly generate a working kerrnel. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)