Date: Tue, 7 Apr 2009 22:24:49 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, x86@kernel.org
Subject: Re: [PATCH] [8/16] POISON: Add various poison checks in mm/memory.c
Message-ID: <20090407202449.GX17934@one.firstfloor.org>
References: <20090407509.382219156@firstfloor.org> <20090407151005.4E24B1D046D@basil.firstfloor.org> <20090407190330.GB3818@cmpxchg.org> <20090407193145.GU17934@one.firstfloor.org> <20090407201708.GA4220@cmpxchg.org>
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> I think we missed each other here.  I wasn't talking about _why_ you
> take that reference -- that is clear.  But I see these two
> possibilities:
> 
>   a) memory_failure() is called on a page on the free list, the
>   get_page() will trigger a bug because the refcount is 0

Ah got it now. Sorry for misreading you. That's indeed a problem.
Fixing.

free pages was something my injector based test suite didn't cover :/

>   b) if that is not possible, the above check is not needed

There was at least one case where the process could free it anyways.
I think. Or maybe that was something I fixed in a different way.
It's possible this check is not needed, but it's probably safer
to keep it (and it's all super slow path)

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.
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