Re: [PATCH 2/8] soft-offline: use migrate_pages() instead of migrate_huge_page()

[Hillf Danton <dhillf@gmail.com>]

On Thu, Jul 25, 2013 at 12:54 PM, Naoya Horiguchi
<n-horiguchi@ah.jp.nec.com> wrote:
> Currently migrate_huge_page() takes a pointer to a hugepage to be
> migrated as an argument, instead of taking a pointer to the list of
> hugepages to be migrated. This behavior was introduced in commit
> 189ebff28 ("hugetlb: simplify migrate_huge_page()"), and was OK
> because until now hugepage migration is enabled only for soft-offlining
> which migrates only one hugepage in a single call.
>
> But the situation will change in the later patches in this series
> which enable other users of page migration to support hugepage migration.
> They can kick migration for both of normal pages and hugepages
> in a single call, so we need to go back to original implementation
> which uses linked lists to collect the hugepages to be migrated.
>
> With this patch, soft_offline_huge_page() switches to use migrate_pages(),
> and migrate_huge_page() is not used any more. So let's remove it.
>
> ChangeLog v3:
>  - Merged with another cleanup patch (4/10 in previous version)
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Acked-by: Andi Kleen <ak@linux.intel.com>
> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
> ---
Acked-by: Hillf Danton <dhillf@gmail.com>

>  include/linux/migrate.h |  5 -----
>  mm/memory-failure.c     | 15 ++++++++++++---
>  mm/migrate.c            | 28 ++--------------------------
>  3 files changed, 14 insertions(+), 34 deletions(-)
>
> diff --git v3.11-rc1.orig/include/linux/migrate.h v3.11-rc1/include/linux/migrate.h
> index a405d3dc..6fe5214 100644
> --- v3.11-rc1.orig/include/linux/migrate.h
> +++ v3.11-rc1/include/linux/migrate.h
> @@ -41,8 +41,6 @@ extern int migrate_page(struct address_space *,
>                         struct page *, struct page *, enum migrate_mode);
>  extern int migrate_pages(struct list_head *l, new_page_t x,
>                 unsigned long private, enum migrate_mode mode, int reason);
> -extern int migrate_huge_page(struct page *, new_page_t x,
> -               unsigned long private, enum migrate_mode mode);
>
>  extern int fail_migrate_page(struct address_space *,
>                         struct page *, struct page *);
> @@ -62,9 +60,6 @@ static inline void putback_movable_pages(struct list_head *l) {}
>  static inline int migrate_pages(struct list_head *l, new_page_t x,
>                 unsigned long private, enum migrate_mode mode, int reason)
>         { return -ENOSYS; }
> -static inline int migrate_huge_page(struct page *page, new_page_t x,
> -               unsigned long private, enum migrate_mode mode)
> -       { return -ENOSYS; }
>
>  static inline int migrate_prep(void) { return -ENOSYS; }
>  static inline int migrate_prep_local(void) { return -ENOSYS; }
> diff --git v3.11-rc1.orig/mm/memory-failure.c v3.11-rc1/mm/memory-failure.c
> index 2c13aa7..af6f61c 100644
> --- v3.11-rc1.orig/mm/memory-failure.c
> +++ v3.11-rc1/mm/memory-failure.c
> @@ -1467,6 +1467,7 @@ static int soft_offline_huge_page(struct page *page, int flags)
>         int ret;
>         unsigned long pfn = page_to_pfn(page);
>         struct page *hpage = compound_head(page);
> +       LIST_HEAD(pagelist);
>
>         /*
>          * This double-check of PageHWPoison is to avoid the race with
> @@ -1482,12 +1483,20 @@ static int soft_offline_huge_page(struct page *page, int flags)
>         unlock_page(hpage);
>
>         /* Keep page count to indicate a given hugepage is isolated. */
> -       ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL,
> -                               MIGRATE_SYNC);
> -       put_page(hpage);
> +       list_move(&hpage->lru, &pagelist);
> +       ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
> +                               MIGRATE_SYNC, MR_MEMORY_FAILURE);
>         if (ret) {
>                 pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
>                         pfn, ret, page->flags);
> +               /*
> +                * We know that soft_offline_huge_page() tries to migrate
> +                * only one hugepage pointed to by hpage, so we need not
> +                * run through the pagelist here.
> +                */
> +               putback_active_hugepage(hpage);
> +               if (ret > 0)
> +                       ret = -EIO;
>         } else {
>                 set_page_hwpoison_huge_page(hpage);
>                 dequeue_hwpoisoned_huge_page(hpage);
> diff --git v3.11-rc1.orig/mm/migrate.c v3.11-rc1/mm/migrate.c
> index b44a067..3ec47d3 100644
> --- v3.11-rc1.orig/mm/migrate.c
> +++ v3.11-rc1/mm/migrate.c
> @@ -979,6 +979,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>
>         unlock_page(hpage);
>  out:
> +       if (rc != -EAGAIN)
> +               putback_active_hugepage(hpage);
>         put_page(new_hpage);
>         if (result) {
>                 if (rc)
> @@ -1066,32 +1068,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>         return rc;
>  }
>
> -int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
> -                     unsigned long private, enum migrate_mode mode)
> -{
> -       int pass, rc;
> -
> -       for (pass = 0; pass < 10; pass++) {
> -               rc = unmap_and_move_huge_page(get_new_page, private,
> -                                               hpage, pass > 2, mode);
> -               switch (rc) {
> -               case -ENOMEM:
> -                       goto out;
> -               case -EAGAIN:
> -                       /* try again */
> -                       cond_resched();
> -                       break;
> -               case MIGRATEPAGE_SUCCESS:
> -                       goto out;
> -               default:
> -                       rc = -EIO;
> -                       goto out;
> -               }
> -       }
> -out:
> -       return rc;
> -}
> -
>  #ifdef CONFIG_NUMA
>  /*
>   * Move a list of individual pages
> --
> 1.8.3.1
>

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