linux-kernel - Re: [PATCH] Allocate memory cgroup structures in local nodes v2

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Message-ID: <20110504213850.GA16685@cmpxchg.org>
Date:	Wed, 4 May 2011 23:38:50 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	rientjes@...gle.com, Michal Hocko <mhocko@...e.cz>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Balbir Singh <balbir@...ibm.com>
Subject: Re: [PATCH] Allocate memory cgroup structures in local nodes v2

On Wed, May 04, 2011 at 01:26:23PM -0700, Andi Kleen wrote:
> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
> index 9905501..a362215 100644
> --- a/mm/page_cgroup.c
> +++ b/mm/page_cgroup.c
> @@ -134,7 +134,7 @@ static void *__init_refok alloc_page_cgroup(size_t size, int nid)
>  {
>  	void *addr = NULL;
>  
> -	addr = alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN);
> +	addr = alloc_pages_exact_node(nid, GFP_KERNEL | __GFP_NOWARN, size);

alloc_pages_exact_node is not the 'specify node as well'-version of
alloc_pages_exact, it refers to 'exact node'.  Thus the
free_pages_exact call is no longer the right counter-part.

alloc_pages_exact_node takes an order, not a size argument.

alloc_pages_exact_node returns a pointer to the struct page, not to
the allocated memory, like all other alloc_pages* functions with the
exception of alloc_pages_exact.

I don't think any of those mistakes even triggers a compiler warning.
Wow.  This API is so thoroughly fscked beyond belief that I think the
only way to top this is to have one of the functions invert the bits
of its return value depending on the parity of the uptime counter.
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