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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD707C00307 for ; Thu, 5 Sep 2019 20:10:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FB9220692 for ; Thu, 5 Sep 2019 20:10:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388606AbfIEUKC (ORCPT ); Thu, 5 Sep 2019 16:10:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39844 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732468AbfIEUKC (ORCPT ); Thu, 5 Sep 2019 16:10:02 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5C742300BEAE; Thu, 5 Sep 2019 20:10:01 +0000 (UTC) Received: from ovpn-124-235.rdu2.redhat.com (ovpn-124-235.rdu2.redhat.com [10.10.124.235]) by smtp.corp.redhat.com (Postfix) with ESMTP id 26E605C1D4; Thu, 5 Sep 2019 20:09:59 +0000 (UTC) Message-ID: Subject: Re: Why add the general notification queue and its sources From: David Lehman To: Ray Strode , Steven Whitehouse Cc: Linus Torvalds , David Howells , Greg Kroah-Hartman , Nicolas Dichtel , raven@themaw.net, keyrings@vger.kernel.org, linux-usb@vger.kernel.org, linux-block , Christian Brauner , LSM List , linux-fsdevel , Linux API , Linux List Kernel Mailing , Ian Kent Date: Thu, 05 Sep 2019 16:09:58 -0400 In-Reply-To: References: <156763534546.18676.3530557439501101639.stgit@warthog.procyon.org.uk> <17703.1567702907@warthog.procyon.org.uk> <11667f69-fbb5-28d2-3c31-7f865f2b93e5@redhat.com> Organization: Red Hat, Inc. Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Thu, 05 Sep 2019 20:10:01 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Archived-At: List-Archive: List-Post: On Thu, 2019-09-05 at 14:51 -0400, Ray Strode wrote: > Hi, > > On Thu, Sep 5, 2019 at 2:37 PM Steven Whitehouse > wrote: > > The original reason for the mount notification mechanism was so > > that we > > are able to provide information to GUIs and similar filesystem and > > storage management tools, matching the state of the filesystem with > > the > > state of the underlying devices. This is part of a larger project > > entitled "Project Springfield" to try and provide better management > > tools for storage and filesystems. I've copied David Lehman in, > > since he > > can provide a wider view on this topic. > So one problem that I've heard discussed before is what happens in a > thinp > setup when the disk space is overallocated and gets used up. IIRC, > the > volumes just sort of eat themselves? > > Getting proper notification of looming catastrophic failure to the > workstation user > before it's too late would be useful, indeed. > > I don't know if this new mechanism dhowells has development can help > with that, My understanding is that there is already a dm devent that gets sent when the low water mark is crossed for a thin pool, but there is nothing in userspace that knows how to effectively get the user's attention at that time. > and/or if solving that problem is part of the Project Springfield > initiative or not. Do you > know off hand? We have been looking into building a userspace event notification service (for storage, initially) to aggregate and add context to low- level events such as these, providing a single source for all kinds of storage events with an excellent signal:noise ratio. Thin pool exhaustion is high on the list of problems we would want to address. David