Re: [RFCv3 2/5] mm/compaction: enable mobile-page migration

[Gioh Kim]

> > @@ -51,6 +54,66 @@ extern void compaction_defer_reset(struct zone *zone, int order,
> >                                  bool alloc_success);
> >   extern bool compaction_restarting(struct zone *zone, int order);
> >
> > +static inline bool mobile_page(struct page *page)
> > +{
> > +       return page->mapping && page->mapping->a_ops &&
>
> Dereferncing mapping->a_ops isn't safe without page-lock and isn't required:
> all mappings always have ->a_ops.

I got it.

> > +static inline void putback_mobilepage(struct page *page)
> > +{
> > +       /*
> > +        * 'lock_page()' stabilizes the page and prevents races against
> > +        * concurrent isolation threads attempting to re-isolate it.
> > +        */
> > +       lock_page(page);
> > +       if (mobile_page(page) && page->mapping->a_ops->putbackpage) {
>
> It seems "if (page->mapping && page->mapping->a_ops->putbackpage)"
> should be enough: we already seen that page as mobile.

Ditto.

> > +               page->mapping->a_ops->putbackpage(page);
> > +               /* drop the extra ref count taken for mobile page isolation */
> > +               put_page(page);
> > +       }
> > +       unlock_page(page);
>
> call put_page() after unlock and do that always -- putback must drop
> page reference from caller.
>
> lock_page(page);
> if (page->mapping && page->mapping->a_ops->putbackpage)
>       page->mapping->a_ops->putbackpage(page);
> unlock_page();
> put_page(page);

Ditto.

> > +}
> >   #else
> >   static inline unsigned long try_to_compact_pages(gfp_t gfp_mask,
> >                          unsigned int order, int alloc_flags,
> > @@ -83,6 +146,19 @@ static inline bool compaction_deferred(struct zone *zone, int order)
> >          return true;
> >   }
> >
> > +static inline bool mobile_page(struct page *page)
> > +{
> > +       return false;
> > +}
> > +
> > +static inline bool isolate_mobilepage(struct page *page, isolate_mode_t mode)
> > +{
> > +       return false;
> > +}
> > +
> > +static inline void putback_mobilepage(struct page *page)
> > +{
> > +}
> >   #endif /* CONFIG_COMPACTION */
> >
> >   #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 35ec87e..33c9aa5 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -395,6 +395,8 @@ struct address_space_operations {
> >           */
> >          int (*migratepage) (struct address_space *,
> >                          struct page *, struct page *, enum migrate_mode);
> > +       bool (*isolatepage) (struct page *, isolate_mode_t);
> > +       void (*putbackpage) (struct page *);
> >          int (*launder_page) (struct page *);
> >          int (*is_partially_uptodate) (struct page *, unsigned long,
> >                                          unsigned long);
> > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> > index f34e040..abef145 100644
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -582,6 +582,25 @@ static inline void __ClearPageBalloon(struct page *page)
> >          atomic_set(&page->_mapcount, -1);
> >   }
> >
> > +#define PAGE_MOBILE_MAPCOUNT_VALUE (-255)
> > +
> > +static inline int PageMobile(struct page *page)
> > +{
> > +       return atomic_read(&page->_mapcount) == PAGE_MOBILE_MAPCOUNT_VALUE;
> > +}
> > +
> > +static inline void __SetPageMobile(struct page *page)
> > +{
> > +       VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
> > +       atomic_set(&page->_mapcount, PAGE_MOBILE_MAPCOUNT_VALUE);
> > +}
> > +
> > +static inline void __ClearPageMobile(struct page *page)
> > +{
> > +       VM_BUG_ON_PAGE(!PageMobile(page), page);
> > +       atomic_set(&page->_mapcount, -1);
> > +}
> > +
> >   /*
> >    * If network-based swap is enabled, sl*b must keep track of whether pages
> >    * were allocated from pfmemalloc reserves.
> > diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
> > index a6c4962..d50d9e8 100644
> > --- a/include/uapi/linux/kernel-page-flags.h
> > +++ b/include/uapi/linux/kernel-page-flags.h
> > @@ -33,6 +33,7 @@
> >   #define KPF_THP                        22
> >   #define KPF_BALLOON            23
> >   #define KPF_ZERO_PAGE          24
> > +#define KPF_MOBILE             25
> >
> >
> >   #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */
> > --
> > 2.1.4

I fixed the code as your comments and I found patch 3/5 and 4/5 could not be applied separately.
So I merge them and report new [PATCH].
I appreciate your reviews.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/