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:

quoted

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 [off-list ref]
SUSE Labs, CR