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 BEA8ACA0EDB for ; Tue, 12 Aug 2025 20:13:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1B7418E0192; Tue, 12 Aug 2025 16:13:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 190E58E0151; Tue, 12 Aug 2025 16:13:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0A4FA8E0192; Tue, 12 Aug 2025 16:13:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id EACB68E0151 for ; Tue, 12 Aug 2025 16:13:32 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 7F3731A01AF for ; Tue, 12 Aug 2025 20:13:32 +0000 (UTC) X-FDA: 83769205464.12.A87F450 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf13.hostedemail.com (Postfix) with ESMTP id BE4AF20003 for ; Tue, 12 Aug 2025 20:13:30 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gZk5s4qd; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1755029610; a=rsa-sha256; cv=none; b=UbU1KPdeBl72Cfi9vLQ6iKzPOZO7qG5flZFB938GfvOOw7mU+acjwGuxqASq7mmOKFHPtL Rg+TrOJ3JnQtnKfJ6oVMugW4RzCesoG3VKZzVr4DRyRFbw9bAf3vz+bQ/nvgUJWp6sKifG DcRETkhvISC3ZCe/7/9UoyQq55knsuY= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gZk5s4qd; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf13.hostedemail.com: domain of sj@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1755029610; 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=yp7X0r++DmuQ8lJAATuCSuGbLBdI9PUcD+fxof48LXQ=; b=YMlwDyxdt1Hw9oK+fJbnZ5cHRZLnSGejV0HAxH0YMehb451D2mlju3XwodyFtNXijMXgpI JzSqC5gj7Z7R/eGYhYLkRXW683UUKYz1bIqVdnFvugUDk4+QVWMpjtI0fomyYfSsa5kARd khs7A+kVJMvCUp4whfMGy70p5w1YUpY= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 9B7515C5B72; Tue, 12 Aug 2025 20:13:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1AD26C4CEF0; Tue, 12 Aug 2025 20:13:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755029609; bh=67thnts7t0DLgkZq/Ii6wBw0jrSFJtM5mUMWCYrbVS8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gZk5s4qdbM6pcT8YroWmQOKRLwIIFGieYYi0v9aoNi2ICJDuc3wg8bhKf+s6pvQNd c+i3MR/y/FAagcjMfROfPVLTOsoG3YlP79F/PpCEZGyFDsyuBtQtypuh96jit6toX0 v+aQUOZ71f1sVS4LLJKLKq+8hdeGPjE2mpVgs/FuY2KZSzhX/6T7dzeh6CvpLmMDoF weuTiAVwv1mVOxNZA1KKoDpEA1hk0wwazemaioBJiDYkvkx74pTiTr9+YupNxQLK8F rz5RHVzbW4bBYKxh5nyMODvXXmIYvJS3DB65gwqyMSJvM3wUZw/6uqpQTB/gIvOiXG Gs3FPiwr7oo7A== From: SeongJae Park To: Lorenzo Stoakes Cc: SeongJae Park , Andrew Morton , 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: Tue, 12 Aug 2025 13:13:26 -0700 Message-Id: <20250812201326.60843-1-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: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: BE4AF20003 X-Stat-Signature: 3emej8uh6tr7udemy55dfgkxgce54xff X-HE-Tag: 1755029610-2172 X-HE-Meta: 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 J+udKwEr EXTnF99AA9PM1qaoHYJrZFsILGbiUh4rk8TUhFJmTW87DJ3VePXmQzCNQvPAx3AEYqDIiGGtYeI9kMTOzOdMm6hv4+ePvtoD6BimPKR2unmUliR9rw3FfdVmF+7GUMFC2qVdlcY1uP60h+xh0lEPEqab2UHInRAi1wm27nEKctPrX6eNMljm/MkofJWqNBhD0yn9fwtsbhAC2pfAYhU3mkzYnraPZUFRKiS8EvM2pxJlCIXlKhlOwBpaQwz9LW/4K9A+eZV3xV9sS246xogXM2zavFQ== 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 Tue, 12 Aug 2025 16:44:09 +0100 Lorenzo Stoakes wrote: > We are currently in the bizarre situation where we are constrained on the > number of flags we can set in an mm_struct based on whether this is a > 32-bit or 64-bit kernel. > > This is because mm->flags is an unsigned long field, which is 32-bits on a > 32-bit system and 64-bits on a 64-bit system. > > In order to keep things functional across both architectures, we do not > permit mm flag bits to be set above flag 31 (i.e. the 32nd bit). > > This is a silly situation, especially given how profligate we are in > storing metadata in mm_struct, so let's convert mm->flags into a bitmap and > allow ourselves as many bits as we like. I like this conversion. [...] > > 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. 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? [...] > For mm->flags initialisation on fork, we adjust the logic to ensure all > bits are cleared correctly, and then adjust the existing intialisation Nit. s/intialisation/initialisation/ ? [...] [1] https://docs.kernel.org/process/coding-style.html#typedefs Thanks, SJ