Re: [PATCH 1/3] Btrfs-progs: add support to set subvolume/snapshot readonly

[Ilya Dryomov <idryomov@gmail.com>]

On Mon, Jul 02, 2012 at 10:07:42AM +0800, Liu Bo wrote:
> On 06/29/2012 06:21 PM, Ilya Dryomov wrote:
> 
> > On Fri, Jun 29, 2012 at 06:00:36PM +0800, Liu Bo wrote:
> >> Setting subvolume/snapshot readonly has been missing for a long time.
> >>
> >> With this patch, we can set a subvolume/snapshot readonly via:
> >>
> >> o    btrfs subvolume set-ro <path>
> > 
> > Alexander's 'btrfs property' patches do exactly this, but in a much more
> > generic and extensible way.  'btrfs property' subgroup provides a
> > uniform interface for getting and setting properties of filesystem
> > objects in general, not only those of subvolumes and snapshots.  It
> > provides a much better user interface, and it also allows us to easily
> > rethink kernel-user interface for generic get/set in future.
> > 
> 
> 
> Thanks for the explanation!
> 
> But I prefer keeping the current categories {subvolume,filesystem,device,...}:
> 
> o Compatibility, we cannot remove the old commands until we make sure that no users will
>   use them.

We are not going to remove old commands any time soon.  However, adding
new ones that clearly fall into get/set category, is not a good idea.
Especially when there is a generic interface on its way.

> 
> o We've three properties {default, readonly, lable}, is it worthy making another new interface?

It's not just about subvolumes.  There will be a lot more properties on
the table as filesystem matures, for example device speeds, subvolume
profiles, quotas.

> 
> o Current categories are clear and clean.

Once again, it's not just about subvolumes.  Current categories are
indeed clear, but adding two commands for each non-trivial property that
comes up in future does not seem practical to me.

Thanks,

		Ilya