Re: [PATCH 4/4] quota: add generic subtree quota support

[Dmitry Monakhov <dmonakhov@openvz.org>]

Christoph Hellwig <hch@infradead.org> writes:

> On Tue, Feb 16, 2010 at 11:25:28AM +0300, Dmitry Monakhov wrote:
>> But this is not "project quota". Project quota is XFS feature.
>> This patch aimed to give an opportunity to implement fs-specific
>> quota_id mapping, and XFS is just an one of possible usecases.
>
> What you desribe as subtree quota is exactly a slightly limited
> implementation of project quotas.  And yes, fs-specific quota interfaces
what do you mean by "slightly limited" ?
I dont now xfs project-id feature very well.
I cant find good explanation of this feature(except man pages).
Can you please post main design assumptions.
> are a horribly bad idea.  If you add features add them in generic code
> and make them opt-in for a specific filesystem to support.
Please read following thread.
http://marc.info/?l=linux-ext4&m=126563931215496&w=2
It will be good idea to implement this in generic vfs layer.
Today i'll plan to post patches which introduce genetic subtree support
on vfs layer.
In fact i use get_id in order to support second-level quota feature
*Second-level quota*
 In order to isolate user/group quota in one subtree from other subtree
 we have to remap quota id similar to:
   quota_uid = (subtree_id << 32) | uid;
>
> And yes, fs-specific quota interfaces are an utter nightmare, speaking
> as the person fixing all this crap up right now.
I've prepare patches against ext4 because:
- i do know something about it internals
- it has journalled quota support.
But off course it will be brilliant to have this feature in VFS layer.
>
> ---end quoted text---