Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751537AbdFID1e (ORCPT ); Thu, 8 Jun 2017 23:27:34 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:45259 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751473AbdFID1c (ORCPT ); Thu, 8 Jun 2017 23:27:32 -0400 X-ME-Sender: X-Sasl-enc: joODVy+ZEEYGAea7ATDGCYJjqertAtG8dU5HN/vD8Hz7 1496978850 Date: Fri, 9 Jun 2017 00:27:28 -0300 From: Henrique de Moraes Holschuh To: NeilBrown Cc: Mikulas Patocka , Shaohua Li , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra Subject: Re: [PATCH] md: don't use flush_signals in userspace processes Message-ID: <20170609032728.GA25899@khazad-dum.debian.net> References: <87h8zrart4.fsf@notabene.neil.brown.name> <87shja9b7s.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87shja9b7s.fsf@notabene.neil.brown.name> X-GPG-Fingerprint1: 4096R/0x0BD9E81139CB4807: C467 A717 507B BAFE D3C1 6092 0BD9 E811 39CB 4807 User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 980 Lines: 21 On Fri, 09 Jun 2017, NeilBrown wrote: > Or maybe it could be discarded - the md_check_recovery() thing. > The idea was that if you alt-sysrq-K to kill all processes, md arrays > would go into immediate-safe-mode where the metadata is marked clean > immediately after writes finish, rather than waiting a few seconds. The > chance of having a clean array after shutdown is hopefully improved. > > I've never actually used this though, and I doubt many people know about > it. And bitmaps make it fairly pointless. Hmm, I have, although I had no idea this was why my arrays were getting far less frazzled than expected... It is really useful behavior, now that I know it can do that. If you can teach SysRq+S, and especially SysRq+U, to force all arrays into safe-mode *after* they carried their current meanings (sync/umount), that would be more useful though, and it would help a lot of people to avoid dirty arrays without them even knowing why... -- Henrique Holschuh