linux-kernel - Re: [Patch] mmu_notifiers destroyed by __mmu_notifier_release() retain extra mm

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Message-ID: <20090205212058.GK14011@random.random>
Date:	Thu, 5 Feb 2009 22:20:58 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Robin Holt <holt@....com>
Cc:	linux-mm@...ck.org, Nick Piggin <npiggin@...e.de>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [Patch] mmu_notifiers destroyed by __mmu_notifier_release()
	retain extra mm_count.

On Thu, Feb 05, 2009 at 11:23:03AM -0600, Robin Holt wrote:
> 
> An application relying upon mmu_notifier_release for teardown of the
> mmu_notifiers will leak mm_structs.  At the do_mmu_notifier_register
> increments mm_count, but __mmu_notifier_release() does not decrement it.

Sure agreed, thanks! This got unnoticed this long because KVM uses the
unregister method instead of the self-disarming ->release and I guess
your systems have quite some ram so it'd take a while for the memleak
to trigger.
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