linux-kernel - Re: [PATCH 06/11] IMA: use i_writecount rather than a private counter

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Date:	Tue, 26 Oct 2010 09:57:45 -0400
From:	"John Stoffel" <john@...ffel.org>
To:	Eric Paris <eparis@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, John Stoffel <john@...ffel.org>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, hch@...radead.org, zohar@...ibm.com,
	warthog9@...nel.org, david@...morbit.com, jmorris@...ei.org,
	kyle@...artin.ca, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, mingo@...e.hu,
	viro@...iv.linux.org.uk
Subject: Re: [PATCH 06/11] IMA: use i_writecount rather than a private
 counter

>>>>> "Eric" == Eric Paris <eparis@...hat.com> writes:

Eric> On Mon, 2010-10-25 at 15:25 -0700, H. Peter Anvin wrote:
>> On 10/25/2010 02:52 PM, Eric Paris wrote:
>> > On Mon, 2010-10-25 at 15:27 -0400, John Stoffel wrote:
>> > 
>> >> The problems with kernel.org is a perfect exmaple of how an annocuous
>> >> feature like this, can kill a system's performance.
>> > 
>> > You admit that you don't know what you are talking about and then state
>> > that this kills systems performance.  Interesting conclusion.
>> > 
>> > I'm not going to try to refute you point by point but will instead paint
>> > a broad picture.  I see 3 possible states:
>> > 1) Configured out - 0 overhead.  period.
>> > 2) Configured in but default disabled
>> > 3) Configured in and enabled by admin intervention
>> > 
>> > I have (I think) pretty clearly discussed the overhead and the changes
>> > made in case #2.  We expand struct inode by 4 bytes, we increment and
>> > decrement those 4 bytes on open/close() and we use a new inode->i_flags.
>> > 
>> 
>> Case #2 is the bad one, as long as distros are likely to compile it in.

Eric> Agreed.  And that's the case this whole patch series is addressing.  It
Eric> makes it (literally not figuratively) hundreds of times better than it
Eric> is today  :)

And just to chime in, I really appreciate your hard work on this
cleanup!

John
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