linux-kernel - Re: [PATCH] mm: Warn once when a page is freed with PG

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Message-ID: <20090724120004.GA2874@cmpxchg.org>
Date:	Fri, 24 Jul 2009 14:00:04 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	kosaki.motohiro@...fujitsu.com, maximlevitsky@...il.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Lee.Schermerhorn@...com, penberg@...helsinki.fi,
	jirislaby@...il.com
Subject: Re: [PATCH] mm: Warn once when a page is freed with PG_mlocked set V2

On Fri, Jul 24, 2009 at 11:36:56AM +0100, Mel Gorman wrote:
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index b8283e8..d3d0707 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -488,6 +488,11 @@ static inline void __free_one_page(struct page *page,
>   */
>  static inline void free_page_mlock(struct page *page)
>  {
> +	WARN_ONCE(1, KERN_WARNING
> +		"Page flag mlocked set for process %s at pfn:%05lx\n"
> +		"page:%p flags:%#lx\n",
> +		current->comm, page_to_pfn(page),
> +		page, page->flags|__PG_MLOCKED);

I don't think printing page->flags is all too useful after they have
been cleared by free_pages_check().

But it's probably a reasonable trade-off for not having it in the
fast-path.

Acked-by: Johannes Weiner <hannes@...xchg.org>
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