From: Li Xi <pkuelelixi@gmail.com>
Subject: Re: [PATCH 0/4] quota: add project quota support
Date: Mon, 4 Aug 2014 22:44:29 +0800
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>   Hum, you are right. add_dquot_ref() is an issue. So probably we'll have
> add get_projid() method to struct dquot_operations (similar to
> get_reserved_space() we have there).
>
>> Personally, I perfer to add projid in the inode
>> stucture, since projid looks like uid and gid of an inode.
>> get_projid()/setprojid()
>> looks duplicated with getattr()/setattr() or getxattr()/setxattr(). Is there any
>> performance impact of increasing size of inode structure, e.g. cache
>> line problem?  I will add get_projid() method if so.
>   I agree projid looks like uid or gid. But uid & gid are in POSIX so
> everyone needs them. projid isn't so we'll just waste space for lots of
> inodes (not too much but still some and this way struct inode gets slowly
> bloated and we can have lots of inodes around). And it's not too hard to
> live without project ID in core inode... Once significant portion of
> filesystems start to support project ID, situation is different and we'll
> move project ID into core inode.
>
> Regarding getting & setting project ID from userspace I suppose you'll have
> to resort to fs-specific ioctl like XFS does and then setting project ID in
> fs-specific part of the inode is trivial.
OK. Thank you very much for your detailed advices. I will refresh the patches
soon.

Regards,
Li Xi