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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA
Cc: kosaki.motohiro@jp.fujitsu.com, Rik van Riel <riel@redhat.com>,
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Date: Thu,  8 Apr 2010 11:03:27 +0900 (JST)
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Hi

Wow, your patch is very cool. I'm surprising such 20 lines patch makes
lots simplify.

> On Wed, 7 Apr 2010, Linus Torvalds wrote:
> > 
> > Yes. The failure point is too late to do anything really interesting with, 
> > and the old code also just causes a SIGBUS. My intention was to change the 
> > 
> > 	WARN_ONCE(!vma->anon_vma);
> > 
> > into returning that SIGBUS - which is not wonderful, but is no different 
> > from old failures.
> 
> Not SIGBUS, but VM_FAULT_OOM, of course.

Now pagefault don't insert anon_vma anymore, right? if so, SIGBUS is better.
Now SIGBUS and VM_FAULT_OOM make different result.

SIGBUS       -> kill current task
VM_FAULT_OOM -> invoke oom-killer (see pagefault_out_of_memory())

If current task can't recover proper anon_vma. we should just kill current
instead random highest badness process. otherwise !anon_vma process continue
to randomly invoke oom-killer.

Perhaps, I'm missing something.