Re: [git pull] device mapper fix for 4.18-rc6

[David Teigland <teigland@redhat.com>]

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