From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Teigland Subject: Re: [git pull] device mapper fix for 4.18-rc6 Date: Tue, 24 Jul 2018 10:30:55 -0500 Message-ID: <20180724153055.GA12605@redhat.com> References: <20180720191407.GA11868@redhat.com> <20180720224046.GA12929@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Mikulas Patocka Cc: dm-devel@redhat.com, Linus Torvalds , Mike Snitzer List-Id: dm-devel.ids On Tue, Jul 24, 2018 at 11:18:54AM -0400, Mikulas Patocka wrote: > > I hold it to be a "fix" because it was an embarassing oversight on my > > part. Without this, userspace support cannot be properly added. LVM2 > > developers raised their inability to put their metadata anywhere and I > > was like "oh shit". > > This is not oversight. > > It was originally planned that the dm-writecache target would use lvm > metadata just like the dm-cache target - if it were implemented this way, > no "offset" argument would be needed. But David Teigland who was given the > task to implement dm-writecache support in lvm refused to do it this way > and he insists that he must put some of his own metadata at the beginning > of the cache device before the superblock. > > So this patch is needed because of him. Mikulas, an offset would have been useful while I was experimenting with dm-writecache. I don't actually use or need the offset in lvm. I don't think it's a bad idea, but I don't care. Dave