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

[Ric Wheeler <ricwheeler@gmail.com>]

On 03/08/2011 01:34 PM, James Bottomley wrote:
> 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

I think that would certainly be a nice start, but we could do something short 
term that did not require that.

Ric