linux-kernel - Re: [PATCH] [8/16] POISON: Add various poison checks in mm/memory.c

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Message-ID: <20090407202449.GX17934@one.firstfloor.org>
Date:	Tue, 7 Apr 2009 22:24:49 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH] [8/16] POISON: Add various poison checks in mm/memory.c

> 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@...ux.intel.com -- Speaking for myself only.
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