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Date: Thu, 7 Jan 2010 16:39:27 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Christoph Lameter <cl@linux-foundation.org>, Arjan van de Ven <arjan@infradead.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "minchan.kim@gmail.com" <minchan.kim@gmail.com>, "hugh.dickins" <hugh.dickins@tiscali.co.uk>, Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>
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On Fri, 8 Jan 2010, KAMEZAWA Hiroyuki wrote:
> 
> Hmm, do_brk() sometimes unmap conflicting mapping. Isn't it be a problem ?

No. For two reasons:

 - sys_brk() doesn't actually do that (see the "find_vma_intersection()" 
   call). I'm not sure why do_brk() does, but it might have to do with 
   execve().

 - the patch I sent out just falls back to the old code if it finds 
   something fishy, so it will do whatever do_brk() does regardless.

(Yes, brk() does unmap the old brk for the _shrinking_ case, of course. 
Again, the patch I sent just falls back to the old behavior in that case)

		Linus

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