Re: [RFCv2 3/5] mm/balloon: apply driver page migratable into balloon

[Konstantin Khlebnikov]

On Fri, Jun 26, 2015 at 12:58 PM, Gioh Kim <gioh.kim@xxxxxxx> wrote:
> Apply driver page migration into balloon driver.
>
> Signed-off-by: Gioh Kim <gioh.kim@xxxxxxx>
> ---
>  drivers/virtio/virtio_balloon.c        |  3 +++
>  fs/proc/page.c                         |  3 +++
>  include/linux/balloon_compaction.h     | 33 +++++++++++++++++++++------------
>  include/uapi/linux/kernel-page-flags.h |  2 +-
>  mm/balloon_compaction.c                | 19 +++++++++++++++++--
>  5 files changed, 45 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 82e80e0..c49b553 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -505,6 +505,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
>         balloon_devinfo_init(&vb->vb_dev_info);
>  #ifdef CONFIG_BALLOON_COMPACTION
>         vb->vb_dev_info.migratepage = virtballoon_migratepage;
> +       vb->vb_dev_info.inode = anon_inode_new();
> +       vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
> +       mapping_set_migratable(vb->vb_dev_info.inode->i_mapping);
>  #endif
>
>         err = init_vqs(vb);
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 7eee2d8..2dc3673 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -146,6 +146,9 @@ u64 stable_page_flags(struct page *page)
>         if (PageBalloon(page))
>                 u |= 1 << KPF_BALLOON;
>
> +       if (PageMigratable(page))
> +               u |= 1 << KPF_MIGRATABLE;
> +
>         u |= kpf_copy_bit(k, KPF_LOCKED,        PG_locked);
>
>         u |= kpf_copy_bit(k, KPF_SLAB,          PG_slab);
> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
> index 9b0a15d..e8a3670 100644
> --- a/include/linux/balloon_compaction.h
> +++ b/include/linux/balloon_compaction.h
> @@ -48,6 +48,7 @@
>  #include <linux/migrate.h>
>  #include <linux/gfp.h>
>  #include <linux/err.h>
> +#include <linux/fs.h>
>
>  /*
>   * Balloon device information descriptor.
> @@ -62,6 +63,7 @@ struct balloon_dev_info {
>         struct list_head pages;         /* Pages enqueued & handled to Host */
>         int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
>                         struct page *page, enum migrate_mode mode);
> +       struct inode *inode;
>  };
>
>  extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
> @@ -73,24 +75,28 @@ static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
>         spin_lock_init(&balloon->pages_lock);
>         INIT_LIST_HEAD(&balloon->pages);
>         balloon->migratepage = NULL;
> +       balloon->inode = NULL;
>  }
>
>  #ifdef CONFIG_BALLOON_COMPACTION
> -extern bool balloon_page_isolate(struct page *page);
> +extern const struct address_space_operations balloon_aops;
> +extern bool balloon_page_isolate(struct page *page,
> +                                isolate_mode_t mode);
>  extern void balloon_page_putback(struct page *page);
> -extern int balloon_page_migrate(struct page *newpage,
> +extern int balloon_page_migrate(struct address_space *mapping,
> +                               struct page *newpage,
>                                 struct page *page, enum migrate_mode mode);
>
>  /*
> - * __is_movable_balloon_page - helper to perform @page PageBalloon tests
> + * __is_movable_balloon_page - helper to perform @page PageMigratable tests
>   */
>  static inline bool __is_movable_balloon_page(struct page *page)
>  {
> -       return PageBalloon(page);
> +       return PageMigratable(page);
>  }
>
>  /*
> - * balloon_page_movable - test PageBalloon to identify balloon pages
> + * balloon_page_movable - test PageMigratable to identify balloon pages
>   *                       and PagePrivate to check that the page is not
>   *                       isolated and can be moved by compaction/migration.
>   *
> @@ -99,7 +105,7 @@ static inline bool __is_movable_balloon_page(struct page *page)
>   */
>  static inline bool balloon_page_movable(struct page *page)
>  {
> -       return PageBalloon(page) && PagePrivate(page);
> +       return PageMigratable(page) && PagePrivate(page);
>  }
>
>  /*
> @@ -108,7 +114,7 @@ static inline bool balloon_page_movable(struct page *page)
>   */
>  static inline bool isolated_balloon_page(struct page *page)
>  {
> -       return PageBalloon(page);
> +       return PageMigratable(page);
>  }
>
>  /*
> @@ -123,7 +129,8 @@ static inline bool isolated_balloon_page(struct page *page)
>  static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>                                        struct page *page)
>  {
> -       __SetPageBalloon(page);
> +       page->mapping = balloon->inode->i_mapping;
> +       __SetPageMigratable(page);
>         SetPagePrivate(page);
>         set_page_private(page, (unsigned long)balloon);
>         list_add(&page->lru, &balloon->pages);
> @@ -139,7 +146,8 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>   */
>  static inline void balloon_page_delete(struct page *page)
>  {
> -       __ClearPageBalloon(page);
> +       page->mapping = NULL;
> +       __ClearPageMigratable(page);

Please leave balloon pages marked as balloon.
Just check them in migration code like:
if (PageBalloon(page) || PageMobile(page)) ...


>         set_page_private(page, 0);
>         if (PagePrivate(page)) {
>                 ClearPagePrivate(page);
> @@ -166,13 +174,13 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
>  static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>                                        struct page *page)
>  {
> -       __SetPageBalloon(page);
> +       __SetPageMigratable(page);
>         list_add(&page->lru, &balloon->pages);
>  }
>
>  static inline void balloon_page_delete(struct page *page)
>  {
> -       __ClearPageBalloon(page);
> +       __ClearPageMigratable(page);
>         list_del(&page->lru);
>  }
>
> @@ -191,7 +199,8 @@ static inline bool isolated_balloon_page(struct page *page)
>         return false;
>  }
>
> -static inline bool balloon_page_isolate(struct page *page)
> +static inline bool balloon_page_isolate(struct page *page,
> +                                       isolate_mode_t mode)
>  {
>         return false;
>  }
> diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
> index a6c4962..65db3a6 100644
> --- a/include/uapi/linux/kernel-page-flags.h
> +++ b/include/uapi/linux/kernel-page-flags.h
> @@ -33,6 +33,6 @@
>  #define KPF_THP                        22
>  #define KPF_BALLOON            23
>  #define KPF_ZERO_PAGE          24
> -
> +#define KPF_MIGRATABLE         25
>
>  #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */
> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
> index fcad832..df72846 100644
> --- a/mm/balloon_compaction.c
> +++ b/mm/balloon_compaction.c
> @@ -131,7 +131,7 @@ static inline void __putback_balloon_page(struct page *page)
>  }
>
>  /* __isolate_lru_page() counterpart for a ballooned page */
> -bool balloon_page_isolate(struct page *page)
> +bool balloon_page_isolate(struct page *page, isolate_mode_t mode)
>  {
>         /*
>          * Avoid burning cycles with pages that are yet under __free_pages(),
> @@ -175,6 +175,9 @@ bool balloon_page_isolate(struct page *page)
>  /* putback_lru_page() counterpart for a ballooned page */
>  void balloon_page_putback(struct page *page)
>  {
> +       if (!isolated_balloon_page(page))
> +               return;
> +
>         /*
>          * 'lock_page()' stabilizes the page and prevents races against
>          * concurrent isolation threads attempting to re-isolate it.
> @@ -193,12 +196,16 @@ void balloon_page_putback(struct page *page)
>  }
>
>  /* move_to_new_page() counterpart for a ballooned page */
> -int balloon_page_migrate(struct page *newpage,
> +int balloon_page_migrate(struct address_space *mapping,
> +                        struct page *newpage,
>                          struct page *page, enum migrate_mode mode)
>  {
>         struct balloon_dev_info *balloon = balloon_page_device(page);
>         int rc = -EAGAIN;
>
> +       if (!isolated_balloon_page(page))
> +               return rc;
> +
>         /*
>          * Block others from accessing the 'newpage' when we get around to
>          * establishing additional references. We should be the only one
> @@ -218,4 +225,12 @@ int balloon_page_migrate(struct page *newpage,
>         unlock_page(newpage);
>         return rc;
>  }
> +
> +/* define the balloon_mapping->a_ops callback to allow balloon page migration */
> +const struct address_space_operations balloon_aops = {
> +       .migratepage = balloon_page_migrate,
> +       .isolatepage = balloon_page_isolate,
> +       .putbackpage = balloon_page_putback,
> +};
> +EXPORT_SYMBOL_GPL(balloon_aops);
>  #endif /* CONFIG_BALLOON_COMPACTION */
> --
> 1.9.1
>
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