From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A340D36AB7D; Wed, 4 Mar 2026 16:42:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772642553; cv=none; b=SmGIvvi9jTVg/JGdDJqgbKmalrKoRtYDNGm32tskFgENp36t2cbz9CPVTbpwNqxXwc9I0P2CdHVcWrHT9LL1WGMwIfIM4LVPXBZSfuPxfCuUpVehHrzZ9I7Y8eC6rocCxM9oqsM0urgUmDtdnZMoqxoqkwiGD4QyjCAskoyUhn0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772642553; c=relaxed/simple; bh=PUN9MokrNUQzb1CRuNzEuvihL2Rfl4GYvtOUTRwsVH0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aBtH/INCb4dPWNwZC9YaLNXcxjW/Z4rDBFRi7y2l190VHZJS1r4BNS1IFfiHPWKbCbwHgOT5Q+CNhjzVE5xtHBK3Ib0pDRyeYBtXKv67b5G18NZAorCkMW0s3WAnPA3EYx8xnENTItl1cSs16DXm1lCxQQvRMXVqD7AyZA3O3cU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KJekaLHE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KJekaLHE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4632FC4CEF7; Wed, 4 Mar 2026 16:42:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772642553; bh=PUN9MokrNUQzb1CRuNzEuvihL2Rfl4GYvtOUTRwsVH0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KJekaLHEc6yHM0DWkmu6wUVO7dUymf0IAb+kvnxU6m81luYkPmU1UFN7FB2W0lFjB neMK82ko9l6EfyrLQlD3nBx8cFpbahfTGiyPABju3bj4ci56UV7Azx0GLvYtwVCmHL 1LqIx2DegU07+QgFYk7hP7DgmEye2ADD33HW6M5YHpRN3upHOLV+SjHEWWgXyfa4TO xHpb94R1UxmxbUOVp47K0+JpW1yVL5c+5TZOjmXfdCOw5q2Ydl/HzBOu6cumbYyOSV Y5Zgxq9msTcoQCadMWT6WyKkB8sp31DUaZ40ylxB84I8EH1LMUbPY63XN8dvZt1eOj Wwo+PpS/ZE7OA== Date: Wed, 4 Mar 2026 06:42:32 -1000 From: Tejun Heo To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Breno Leitao , Jens Axboe , Josef Bacik , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, thevlad@meta.com, kernel-team@meta.com Subject: Re: [PATCH v2] blk-cgroup: always display debug stats in io.stat Message-ID: References: <20260303-blk_cgroup_debug_stats-v2-1-196c713cb762@debian.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Hello, On Wed, Mar 04, 2026 at 02:28:03PM +0100, Michal Koutný wrote: > On Tue, Mar 03, 2026 at 07:46:46AM -1000, Tejun Heo wrote: > > > has not been modularized since commit 32e380aedc3de ("blkcg: make > > > CONFIG_BLK_CGROUP bool"), making the module parameter a historical > > > artifact. Readers of the nested-keys format should be able to handle > > > additional fields. > > > > I'm not sure what the above para means. Module param works just fine for > > built-in modules on both boot command line and through sysfs. > > Yeah, it works but BLK_CGROUP is not a module/built-in it's config > option affecting builds. I find the module_param() in blk-cgroup.c to be > a residual, I admit it's convenient way how to expose a tunable to > userspace. > > (Contemporary way of implementing the option could also be a cgroupfs > mount option/feature or maybe sysctl for which tooling is available.) I don't konw whether I'm the only one doing it but I use moduleparams as an easy way to get non-API boot and runtime toggles whether the target code is actually module or not. It's easy to use and the params are in a pretty gray area in terms of API stability, so if you wanna throw in a debug option, it works. Thanks. -- tejun