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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE1EDCA0EE0 for ; Wed, 13 Aug 2025 16:24:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4BCCB9000AD; Wed, 13 Aug 2025 12:24:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 46D78900088; Wed, 13 Aug 2025 12:24:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 30EFA9000AD; Wed, 13 Aug 2025 12:24:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 18942900088 for ; Wed, 13 Aug 2025 12:24:51 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 90ACE58DB3 for ; Wed, 13 Aug 2025 16:24:50 +0000 (UTC) X-FDA: 83772257940.10.571DB3B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf17.hostedemail.com (Postfix) with ESMTP id CE9AF40006 for ; Wed, 13 Aug 2025 16:24:48 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NowuzJLv; spf=pass (imf17.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1755102289; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Ntpsda4EGycyiP3WgWJ5U2Zn4afzuVItLgDlY0baPT4=; b=FxX7qTYht2d5+h8kG0wn+PfVZ9B7qwuW6VdYsWJ/FEt4aLgcm2+Xl+ePPenQc+NN/8abk7 fNiwMqQHOxSKbzyQPTRd7wEWUn2ic5QiWSZMF8nE5NujAVCsYfEitUHKRKdr3Di8YoHn9Z b/LbKjp1AEnF6EsMKh72Pzbv26yLQrw= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NowuzJLv; spf=pass (imf17.hostedemail.com: domain of sj@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1755102289; a=rsa-sha256; cv=none; b=XkSe6phxS4Enu7dtsprEaePA/sCe8n/ATvBOCzHqiHa7Xd/DFM0CWcJehXjobTIVJopmTB PWWkO32dwlQCO4GrxBz2Q6xxwpN4+Tg4vVdfTIxwBZIpj8AhntvkPIe/i9mXElvLlze6iQ EXKk775G5Og5+ylNFlUqKufE3aXlclg= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 56FAA41A7E; Wed, 13 Aug 2025 16:24:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09AF3C4CEEB; Wed, 13 Aug 2025 16:24:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755102287; bh=K1Qnz6FeiAMe891bHx38SnseQkGtn7jJpOFA1e7ci+8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NowuzJLvoDcytU2mnlkUjH9a3VkVMtm7ue/1JeEievbLShowGrZYKS4ljQgIc4Tvt 3+vYZnNOWzD9UQ8pSH9fEmYwxPiiGspKJ3H0P32SvVzl8AqitUBhqFYwGCZ45kSKAJ 87/gu7vuZjna5FtZYWWUpp9S1G/8o7Ty64t0lObmjPlPr2MXYLPDtH4Sc4eAU6xND8 ThhzDQ4hSAh1VB48U+GqBbKfJNoQAGi7b1yhwF4mFVAalvl713Ll6uzzSrl8gdzvsB qxd/OanAUdPmrliRUlwzqp8QiFiC+SAvfzE7ZdQVKX6a28IsBlnq34Yk6UcqsLFVxB 8m4KWJEM4NWXw== From: SeongJae Park To: Lorenzo Stoakes Cc: SeongJae Park , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , "David S . Miller" , Andreas Larsson , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Xu Xin , Chengming Zhou , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , David Rientjes , Shakeel Butt , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , Masami Hiramatsu , Oleg Nesterov , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Jason Gunthorpe , John Hubbard , Peter Xu , Jann Horn , Pedro Falcato , Matthew Wilcox , Mateusz Guzik , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH 00/10] mm: make mm->flags a bitmap and 64-bit on all arches Date: Wed, 13 Aug 2025 09:24:45 -0700 Message-Id: <20250813162445.5456-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CE9AF40006 X-Stat-Signature: hm63e57oe4yyoudynmzu4zdpho89ortx X-Rspam-User: X-HE-Tag: 1755102288-289612 X-HE-Meta: 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 fXpZdqeY VoGxrlE9UkIux/nkZnNkM8506OD6fa5a0nArR0F9Xc6gFciPWzTyDbT5eLSgElsqgpA6Y541SnJYY2lHoNtDsvkRZtc2JlyTlYtrzzKFTdTI4Us8ZLHywRNiMa3e7qkF0H4ErFRmnrV5qcy57J/YAhtKBp8wkBjS2OABTlnDE3Hx56M+sHL1Ohmpxr2K1P9RggOIuuBuXAmOJFZ96AxoYFTWds/D0bVH4d3WiUajRzxKDtPQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 13 Aug 2025 05:18:31 +0100 Lorenzo Stoakes wrote: > On Tue, Aug 12, 2025 at 01:13:26PM -0700, SeongJae Park wrote: > > On Tue, 12 Aug 2025 16:44:09 +0100 Lorenzo Stoakes wrote: [...] > > > In order to execute this change, we introduce a new opaque type - > > > mm_flags_t - which wraps a bitmap. > > > > I have no strong opinion here, but I think coding-style.rst[1] has one? To > > quote, > > > > Please don't use things like ``vps_t``. > > It's a **mistake** to use typedef for structures and pointers. > > You stopped reading the relevant section in [1] :) Keep going and you see: > > Lots of people think that typedefs help readability. Not so. They > are useful only for: totally opaque objects (where the typedef is > actively used to hide what the object is). Example: pte_t > etc. opaque objects that you can only access using the proper > accessor functions. > > So this is what this is. > > The point is that it's opaque, that is you aren't supposed to know about or > care about what's inside, you use the accessors. > > This means we can extend the size of this thing as we like, and can enforce > atomicity through the accessors. > > We further highlight the opaqueness through the use of the __private. > > > > > checkpatch.pl also complains similarly. > > > > Again, I have no strong opinion, but I think adding a clarification about why > > we use typedef despite of the documented recommendation here might be nice? > > I already gave one, I clearly indicate it's opaque. You're completely right and I agree all the points. Thank you for kindly enlightening me :) Thanks, SJ [...]