linux-ext4 - Re: [v6 2/4] ext4: adds project ID support

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Date:	Tue, 11 Nov 2014 21:23:02 +0100
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Li Xi <pkuelelixi@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-api@...r.kernel.org,
	adilger@...ger.ca, jack@...e.cz, viro@...iv.linux.org.uk,
	hch@...radead.org, dmonakhov@...nvz.org
Subject: Re: [v6 2/4] ext4: adds project ID support

On Mon 10-11-14 23:26:06, Ted Tso wrote:
> On Sun, Nov 09, 2014 at 01:43:37AM +0800, Li Xi wrote:
> > This patch adds a new internal field of ext4 inode to save project
> > identifier. Also a new flag EXT4_INODE_PROJINHERIT is added for
> > inheriting project ID from parent directory.
> 
> What would be the downside of simply always inhereiting the project ID
> from the parent directory?  I see that if the flag is not set, the
> project id will be 0 instead.  I'm not sure when that would actually
> be desirable.
  Well, 0 is a fallback project ID effectively meaning "not accounted in
project quota".

> To the extent that the project ID is designed to implement a quota
> over a directory extent, the fact that the owner can clear the
> EXT4_PROJINHERET_FL and then arrange to have the quota charged to
> project 0 seems to me to be a bug, not a feature.
> 
> Can you explain what your intended use case for this flag might be?
  So I agree that for directory quotas there's no reason not to inherit the
project ID. But there might be other use cases and I strongly prefer to
stay compatible with XFS as far as reasonably possible to make life for
userspace simpler.

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