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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Christoph Lameter <clameter@sgi.com>
Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support)
Date: Tue, 11 Sep 2007 16:06:09 +1000
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Cc: Mel Gorman <mel@csn.ul.ie>, andrea@suse.de, torvalds@linux-foundation.org,
       linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       Christoph Hellwig <hch@lst.de>, Mel Gorman <mel@skynet.ie>,
       William Lee Irwin III <wli@holomorphy.com>, David Chinner <dgc@sgi.com>,
       Jens Axboe <jens.axboe@oracle.com>,
       Badari Pulavarty <pbadari@gmail.com>,
       Maxim Levitsky <maximlevitsky@gmail.com>,
       Fengguang Wu <fengguang.wu@gmail.com>, swin wang <wangswin@gmail.com>,
       totty.lu@gmail.com, hugh@veritas.com, joern@lazybastard.org
References: <20070911060349.993975297@sgi.com> <200709111530.16136.nickpiggin@yahoo.com.au> <Pine.LNX.4.64.0709111439280.27023@schroedinger.engr.sgi.com>
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On Wednesday 12 September 2007 07:41, Christoph Lameter wrote:
> On Tue, 11 Sep 2007, Nick Piggin wrote:
> > I think I would have as good a shot as any to write a fragmentation
> > exploit, yes. I think I've given you enough info to do the same, so I'd
> > like to hear a reason why it is not a problem.
>
> No you have not explained why the theoretical issues continue to exist
> given even just considering Lumpy Reclaim in .23 nor what effect the
> antifrag patchset would have.

So how does lumpy reclaim, your slab patches, or anti-frag have
much effect on the worst case situation? Or help much against a
targetted fragmentation attack?


> And you have used a 2M pagesize which is 
> irrelevant to this patchset that deals with blocksizes up to 64k. In my
> experience the use of blocksize < PAGE_COSTLY_ORDER (32k) is reasonably
> safe.

I used EXACTLY the page sizes that you brought up in your patch
description (ie. 64K and 2MB).
-
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