From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Ferdinand Subject: Re: Input requirement for persistent configuration items in bcache Date: Sun, 5 Jul 2020 11:12:14 +0200 Message-ID: <20200705091214.GL14425@xoff> References: <0fe47cd9-ffa0-b440-44ca-6ed9419dfb01@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725901AbgGEJOh (ORCPT ); Sun, 5 Jul 2020 05:14:37 -0400 Received: from smtp.mfedv.net (smtp.mfedv.net [IPv6:2a04:6c0:2::19]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F151C061794 for ; Sun, 5 Jul 2020 02:14:37 -0700 (PDT) Content-Disposition: inline In-Reply-To: <0fe47cd9-ffa0-b440-44ca-6ed9419dfb01@suse.de> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Coly Li Cc: "linux-bcache@vger.kernel.org" On Sun, Jul 05, 2020 at 12:45:41PM +0800, Coly Li wrote: > While I am thinking about this, I do appreciate your help about the > input on which configuration item should be stored in the on-disk > superblock. Hi, my use case is rather limited, all my bcache devices run in writeback mode, and the only parameters I keep playing with are writeback_percent and sequential_cutoff. My short list of favourites: - cache_mode - writeback_percent - sequential_cutoff But I vaguely remember that I used rebooting as last resort after too much fiddling with tunables; persisting them in the superblock means losing this reset-to-defaults method. Would be nice to have some other way of resetting. An alternative to modifying the superblock might be something more out-of-band like iptables does with iptables-save and iptables-restore: convert current settings to text, e.g. on shutdown or at regular intervals, and restore settings on boot from this text file. Regards Matthias