On Tue, 17 Jul 2012 13:50:41 -0300
Rafael Aquini <aquini@xxxxxxxxxx> wrote:
> This patch introduces the helper functions as well as the necessary changes
> to teach compaction and migration bits how to cope with pages which are
> part of a guest memory balloon, in order to make them movable by memory
> compaction procedures.
>
> ...
>
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1629,5 +1629,20 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; }
> static inline bool page_is_guard(struct page *page) { return false; }
> #endif /* CONFIG_DEBUG_PAGEALLOC */
>
> +#if (defined(CONFIG_VIRTIO_BALLOON) || \
> + defined(CONFIG_VIRTIO_BALLOON_MODULE)) && defined(CONFIG_COMPACTION)
> +extern bool putback_balloon_page(struct page *);
> +extern struct address_space *balloon_mapping;
> +
> +static inline bool is_balloon_page(struct page *page)
> +{
> + return (page->mapping == balloon_mapping) ? true : false;
You can simply do
return page->mapping == balloon_mapping;
> +}
> +#else
> +static inline bool is_balloon_page(struct page *page) { return false; }
> +static inline bool isolate_balloon_page(struct page *page) { return false; }
> +static inline bool putback_balloon_page(struct page *page) { return false; }
> +#endif /* (VIRTIO_BALLOON || VIRTIO_BALLOON_MODULE) && COMPACTION */
This means that if CONFIG_VIRTIO_BALLOON=y and CONFIG_COMPACTION=n,
is_balloon_page() will always return NULL. IOW, no pages are balloon
pages! This is wrong.
I'm not sure what to do about this, apart from renaming the function to
is_compactible_balloon_page() or something similarly aawkward.
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