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 1A140C433F5 for ; Fri, 30 Sep 2022 18:04:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231406AbiI3SEJ (ORCPT ); Fri, 30 Sep 2022 14:04:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbiI3SEG (ORCPT ); Fri, 30 Sep 2022 14:04:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 629EB1D7BE4 for ; Fri, 30 Sep 2022 11:04:05 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DE4D4623EE for ; Fri, 30 Sep 2022 18:04:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB2CFC433D6; Fri, 30 Sep 2022 18:04:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664561044; bh=HBbYVcvs75oAGjIxPLKiGDrS/lAmgAYEWh80o4c7DwU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V1R010OMHBKNAGjTeSeoIApHOfQ4ULH6A5Y07XTINnt+5Jh+PEdjRmiAd/8NTLqKO TAwqEoitSYsbV0U5494V4j7MS5yfZYBchOjx50jc787sef9qf9SWpfG8sZ8dy7G6HV 6mVhNAu7/5nv4qTuH2BNiL9uaAFIAMm7vru4/azxPVCV+OcKs/jiKHom+QXszb3iHc Tyn8IBsM1BVOirEfnD8e4aVG2PyTCH7kTEWzW+kPe0uP97PfyIjXE0MRq6HNnxKpQl X8hedZmFo1kkRwzKNXJmaU/wbORpZVMspxAH31gf5dWkHYNXba+WZco3uAPfmtHI26 qBhNpcKAZJlYw== From: SeongJae Park To: haoxin Cc: SeongJae Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm/damon: add DAMON_OBJ macro Date: Fri, 30 Sep 2022 18:04:01 +0000 Message-Id: <20220930180401.67230-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <61df199f-5579-933e-3f11-35f204f93bf4@linux.alibaba.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Xin, On Fri, 30 Sep 2022 11:46:26 +0800 haoxin wrote: > Hi SJ, > > 在 2022/9/22 上午12:41, SeongJae Park 写道: > > Hi Xin, > > > > On Wed, 21 Sep 2022 11:49:42 +0800 Xin Hao wrote: > > > >> In damon/sysfs.c file, we use 'container_of' macro to get > >> damon_sysfs_xxx struct instances, but i think it has a little > >> inconvenience, because we have to pass three arguments to > >> 'container_of', and the codes also look a bit long, so there i add a > >> 'DAMON_OBJ' macro, you just need to pass one arguments, then you can get > >> the right damon_sysfs_xxx struct instance. > > Thank you always for your helps and efforts, but I have some comments below. > > > >> Signed-off-by: Xin Hao > >> --- > >> include/linux/damon.h | 7 ++ > >> mm/damon/sysfs.c | 230 +++++++++++++++++------------------------- > >> 2 files changed, 102 insertions(+), 135 deletions(-) > >> > >> diff --git a/include/linux/damon.h b/include/linux/damon.h > >> index e7808a84675f..a3b577677caa 100644 > >> --- a/include/linux/damon.h > >> +++ b/include/linux/damon.h > >> @@ -24,6 +24,13 @@ static inline unsigned long damon_rand(unsigned long l, unsigned long r) > >> return l + prandom_u32_max(r - l); > >> } > >> > >> +/* > >> + * Get damon_sysfs_xxx relative struct instance. > >> + */ > >> +#define DAMON_OBJ(_type) ({ \ > >> + const typeof(((struct _type *)0)->kobj)*__mptr = (kobj); \ > >> + (struct _type *)((char *)__mptr - offsetof(struct _type, kobj)); }) > >> + > > So, this macro assumes two implicit rules. > > 1. The caller would have a relevant 'struct kobject *' variable called 'kobj', > > and > > 2. The '_type' would have the field 'kobj'. > > > > I think the implicit rules could make some people confused, so would be better > > to be well documented. Even though those are well documented, I think it > > cannot intuitively read by everyone. Making the name better self-explaining > > might help, but then the length of the code would be not so different. > > > > So IMHO, this change makes the code a little bit shorter but unclear to > > understand what it does. And at least to my humble eyes, use of > > 'container_of()' makes the code a little bit more verbose, but clear to > > understand. I have no idea how we can make this code shorter while keeping it > > still easily understandable, and I think the level of verboseness is acceptable > > for the readability. So Nack at the moment, sorry. > > I really feel the need to do that， how about keep it in the sysfs.c > file, and change it like this： > > #define DAMON_OBJ(_struct) container_of(kobj, struct _struct, kobj) > > it will feel easy to understand and made sense. I don't think this is enough, at least for my humble eyes. My questions for better self-explaining name and removing the implicit rules are not answered. After all, I don't think the usage of container_of() is a real problem, though we might always have rooms for improvement. Thanks, SJ [...]