Messages in this thread | | | Date | Wed, 18 Jul 2012 15:46:05 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v4 1/3] mm: introduce compaction and migration for virtio ballooned pages |
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On Tue, 17 Jul 2012 13:50:41 -0300 Rafael Aquini <aquini@redhat.com> 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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