linux-kernel - Re: [PATCH 39/40] autonuma: bugcheck page_autonuma fields on newly allocated pages

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Date:	Mon, 02 Jul 2012 02:40:53 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Hillf Danton <dhillf@...il.com>, Dan Smith <danms@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Bharata B Rao <bharata.rao@...il.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Johannes Weiner <hannes@...xchg.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Alex Shi <alex.shi@...el.com>,
	Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Don Morris <don.morris@...com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 39/40] autonuma: bugcheck page_autonuma fields on newly
 allocated pages

On 06/28/2012 08:56 AM, Andrea Arcangeli wrote:
> Debug tweak.

> +static inline void autonuma_check_new_page(struct page *page)
> +{
> +	struct page_autonuma *page_autonuma;
> +	if (!autonuma_impossible()) {
> +		page_autonuma = lookup_page_autonuma(page);
> +		BUG_ON(page_autonuma->autonuma_migrate_nid != -1);
> +		BUG_ON(page_autonuma->autonuma_last_nid != -1);

At this point, BUG_ON is not likely to give us a useful backtrace
at all.

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 2d53a1f..5943ed2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -833,6 +833,7 @@ static inline int check_new_page(struct page *page)
>   		bad_page(page);
>   		return 1;
>   	}
> +	autonuma_check_new_page(page);
>   	return 0;
>   }

Why don't you hook into the return codes that
check_new_page uses?

They appear to be there for a reason.

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