From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:41414 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751650AbeA2VIl (ORCPT ); Mon, 29 Jan 2018 16:08:41 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 223BE4F1B0 for ; Mon, 29 Jan 2018 21:08:41 +0000 (UTC) Date: Mon, 29 Jan 2018 16:08:37 -0500 From: Mike Snitzer To: linux-block@vger.kernel.org, dm-devel@redhat.com Subject: [LSF/MM TOPIC] block, dm: restack queue_limits Message-ID: <20180129210836.GA5744@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org We currently don't restack the queue_limits if the lowest, or intermediate, layer of an IO stack changes. This is particularly unfortunate in the case of FLUSH/FUA which may change if/when a HW controller's BBU fails; whereby requiring the device advertise that it has a volatile write cache (WCE=1). But in the context of DM, really it'd be best if the entire stack of devices had their limits restacked if any underlying layer's limits change. In the past, Martin and I discussed that we should "just do it" but never did. Not sure we need a lengthy discussion but figured I'd put it out there. Maybe I'll find time, between now and April, to try implementing it. Thanks, Mike