linux-kernel - Re: [PATCH 00/37] Permit filesystem local caching

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Message-ID: <12508.1203538281@redhat.com>
Date:	Wed, 20 Feb 2008 20:11:21 +0000
From:	David Howells <dhowells@...hat.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	dhowells@...hat.com, Trond.Myklebust@...app.com,
	chuck.lever@...cle.com, casey@...aufler-ca.com,
	nfsv4@...ux-nfs.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, selinux@...ho.nsa.gov,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 00/37] Permit filesystem local caching

Serge E. Hallyn <serue@...ibm.com> wrote:

> Seems *really* weird that every time you send this, patch 6 doesn't seem
> to reach me in any of my mailboxes...  (did get it from the url
> you listed)

It's the largest of the patches, so that's not entirely surprising.  Hence why
I included the URL to the tarball also.

> I'm sorry if I miss where you explicitly state this, but is it safe to
> assume, as perusing the patches suggests, that
> 
> 	1. tsk->sec never changes other than in task_alloc_security()?  

Correct.

> 	2. tsk->act_as is only ever dereferenced from (a) current->

That ought to be correct.

> 	   except (b) in do_coredump?

Actually, do_coredump() only deals with current->act_as.

> (thereby carefully avoiding locking issues)

That's the idea.

> I'd still like to see some performance numbers.  Not to object to
> these patches, just to make sure there's no need to try and optimize
> more of the dereferences away when they're not needed.

I hope that the performance impact is minimal.  The kernel should spend very
little time looking at the security data.  I'll try and get some though.

> Oh, manually copied from patch 6, I see you have in the task_security
> struct definition:
> 
> 	kernel_cap_t    cap_bset;       /* ? */
> 
> That comment can be filled in with 'capability bounding set' (for this
> task and all its future descendents).

Thanks.

David
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