linux-ext4 - Re: [PATCH 0/4] quota: add project quota support

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Message-ID: <20140801201756.GD7525@quack.suse.cz>
Date:	Fri, 1 Aug 2014 22:17:56 +0200
From:	Jan Kara <jack@...e.cz>
To:	Li Xi <pkuelelixi@...il.com>
Cc:	Jan Kara <jack@...e.cz>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 0/4] quota: add project quota support

On Fri 01-08-14 23:48:31, Li Xi wrote:
> 2014-08-01 23:28 GMT+08:00 Li Xi <pkuelelixi@...il.com>:
> > 2014-08-01 20:40 GMT+08:00 Jan Kara <jack@...e.cz>:
> >>
> >> 1) It should have been also posted to linux-fsdevel@...r.kernel.org, Al Viro
> >> <viro@...IV.linux.org.uk>, Christoph Hellwig <hch@...radead.org> because
> >> you are changing core VFS inode and infrastructure as well. For quota
> >> changes you should have also CCed me as a quota maintainer.
> > Sure. Thanks for reminding me. I will add these addresses next time.
> >>
> >> 2) I'm not convinced we actually want project ID in the core inode - so far
> >> only XFS has this. For everyone else it's just extra bloat so we could just
> >> put it in ext4_inode_info. Granted we'd need to somewhat change quota
> >> interface so that it sees all the ids (uid, gid, projid) but they are
> >> really needed in two places - dquot_initalize() and dquot_transfer() and
> >> creating variants of these functions that just take an array of ids and use
> >> them in ext4 is simple enough.
> > OK, agreed.
> After searching dquot_initalize() and dquot_transfer(), I found changing these
> two functions envolves too many file systems. Is there any good reason not to
> add kprojid_t field in inode structure?
  Yes. It grows struct inode which is used by *all* filesystems and only
ext4 (and possibly xfs) would use it. That's why I suggested you create
something like:

struct inode_ids {
	kuid_t uid;
	kgid_t gid;
	kprojid_t projid;
};

void dquot_initialize_ids(struct inode *inode, struct inode_ids *ids)
{
...
}

and

static inline void dquot_initialize(struct inode *inode)
{
	struct inode_ids ids = {
				.uid = inode->i_uid,
				.gid = inode->i_gid,
				.projid = INVALID_PROJID,
			};
	dquot_initialize_ids(inode, &ids);			
}

Then filesystems not using project ids remain untouched and filesystems
with project ids (i.e. ext4) can use dquot_initialize_ids() - probably you
should create something like:

static inline void ext4_dquot_initialize(struct inode *inode)
{
	struct inode_ids ids = {
				.uid = inode->i_uid,
				.gid = inode->i_gid,
				.projid = EXT4_I(inode)->i_projid,
			};
	dquot_initialize_ids(inode, &ids);
}

and use ext4_dquot_initialize() throughout ext4.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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