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Date: Thu, 22 Mar 2007 17:01:22 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: "Ken Chen" <kenchen@google.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [patch] cache pipe buf page address for non-highmem arch
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On Thu, 22 Mar 2007 17:51:11 -0700 "Ken Chen" <kenchen@google.com> wrote:

> +#ifdef CONFIG_HIGHMEM
> +#define pipe_kmap		kmap
> +#define pipe_kmap_atomic	kmap_atomic
> +#else	/* CONFIG_HIGHMEM */
> +static inline void *pipe_kmap(struct page *page)
> +{
> +	return (void *) page->private;
> +}
> +static inline void *pipe_kmap_atomic(struct page *page, enum km_type type)
> +{
> +	pagefault_disable();
> +	return pipe_kmap(page);
> +}
> +#endif

If we're going to do this then we should also implement pipe_kunmap_atomic().
Relying upon kunmap_atomic() internals like this is weird-looking, and is fragile
against future changes to kunmap_atomic().