From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754601AbcJEGu4 (ORCPT ); Wed, 5 Oct 2016 02:50:56 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:47029 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752359AbcJEGuz (ORCPT ); Wed, 5 Oct 2016 02:50:55 -0400 Date: Wed, 5 Oct 2016 08:51:01 +0200 From: Greg KH To: Andy Grover , dm-devel@redhat.com, linux-kernel@vger.kernel.org, snitzer@redhat.com Subject: Re: [dm-devel] [PATCH 0/9] Generate uevents for all DM events Message-ID: <20161005065101.GB11013@kroah.com> References: <1475522580-16723-1-git-send-email-agrover@redhat.com> <20161004072015.GA11216@kroah.com> <20161005004004.GC28416@agk-dp.fab.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161005004004.GC28416@agk-dp.fab.redhat.com> User-Agent: Mutt/1.7.0 (2016-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 05, 2016 at 01:40:05AM +0100, Alasdair G Kergon wrote: > On Tue, Oct 04, 2016 at 04:39:28PM -0700, Andy Grover wrote: > > devicemapper is using uevents for: > > a. dm-verity detected corruption > > b. dm-multipath: path failed or reinstated > > c. dm device renamed > > d. there's also some use in md and bcache. > > > > devicemapper uses DM_EVENT ioctl (yuck) for: > > 1. dm-thin pool data/metadata filling up (hit a threshold) > > 2. dm-cache is now clean > > 3. dm-log flushed or log failed > > 4. dm-raid error detected or sync complete > > > there doesn't seem to be much technical differentiation between the > > two lists. > > The distinction in dm is that events in the first category may affect > the availability of the device: they represent major (and hopefully > rare) changes. > > Events in the second category are just notifications: no impact on /dev, > no need to trigger udev rules, and their use will continue to be > extended, and (rarely at the moment) could be frequent (which is no > problem for the existing polling-based mechanism). > > > Instead of using uevent for everything, we could go to a separate > > genetlink for 1-4 instead of making them use uevent like a-d, but we'd > > end up with two different userspace notification techniques. > > We see these as two different categories of notifications, and prefer > the greater flexibility a mechanism independent of uevents would > provide. The team has discussed several alternatives over the years but > didn't make a decision as we've not yet reached a point where we're > straining the existing mechanism too far. So, no changes need to be made? I'm confused here, who is wanting this changed? greg k-h