Re: [dm-devel] generic wrappers for multi-device FS operations

[James Bottomley <James Bottomley suse de>]

On Tue, 2011-03-08 at 13:13 -0500, Ric Wheeler wrote:
> On 03/08/2011 01:05 PM, Wendy Cheng wrote:
> >> On Tue, Mar 08, 2011 at 12:04:25PM -0500, Ric Wheeler wrote:
> >>> To make this trivial to do for users, I think that it would be really
> >>> nice to have a two-level wrappers for things like resize, add a volume,
> >>> shrink, etc. Similar to the way we have mount or fsck invoke file system
> >>> specific bits.
> >>> Good idea? Bad idea?
> > So the "resize" is on the filesystem, not the volume ? The "grow" part
> > is probably easy. Unfortunately, the "shrink" may not be easy for some
> > of the filesystems:
> >
> > -- Wendy
> 
> I think any "standard" operation would be allowed to fail with "notsupported" 
> effectively. Shrink is definitely a challenge & even when it works, it often has 
> performance implications.
> 
> I think that adding support to fsadm might be the easy path forward, but we 
> would need to be able to do at least a handful of more advanced things (add a 
> whole device for example).

There's still the problem of moving the underlying device from being a
plain block device to being a dm one ... what happened to the idea of
presenting all devices as dm ones to solve this?

James