linux-kernel - Re: [PATCH -V7 21/26] richacl: xattr mapping functions

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Message-ID: <20111121133521.GB656@fieldses.org>
Date:	Mon, 21 Nov 2011 08:35:21 -0500
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Christoph Hellwig <hch@...radead.org>, agruen@...nel.org,
	akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
	dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH -V7 21/26] richacl: xattr mapping functions

On Sat, Nov 19, 2011 at 01:28:10AM -0800, Eric W. Biederman wrote:
> Thanks for the cc.  After looking at the user namespace issues it looks
> like the sane thing is really to map the user namespace uids into
> appropriate uids for storing on the filesystem.  Anything else
> seems to be a lot of pain for very little gain.
> 
> If a filesystem went as far as storing string ids.  I think I would
> be happy to use different domains for different user namespaces, but
> for anything else I just don't see the point.
> 
> What it does look like to me is that at some point we will want to
> support > 32bit uids.  There are 7 billion people on the planet and we
> only have 4 billion user ids.  The biggest individual organization have
> 3 million users, which keeps us safe for now.  However my forecast is
> each user namespace is going to wind up giving each user a bunch of
> uids.  That will accelerate the point at which we find 32bit uids tight.
> How fast being generous and assigning 10k uids per user is going to get
> us into trouble I don't know. 

Yes, bigger uid's make sense to me.

But at the point when we make that transition I think updating the ACL
format will be the least of our troubles.  So I think we'll leave it
alone rather than try to guess the right type now.

--b.
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