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Message-ID: <55A37ABA.3000001@lge.com>
Date: Mon, 13 Jul 2015 17:45:46 +0900
From: Gioh Kim <gioh.kim@....com>
To: Konstantin Khlebnikov <koct9i@...il.com>
CC: Jeff Layton <jlayton@...chiereds.net>,
Bruce Fields <bfields@...ldses.org>,
Vlastimil Babka <vbabka@...e.cz>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Al Viro <viro@...iv.linux.org.uk>,
"Michael S. Tsirkin" <mst@...hat.com>,
Minchan Kim <minchan@...nel.org>,
Rafael Aquini <aquini@...hat.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
virtualization@...ts.linux-foundation.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>, gunho.lee@....com,
Andrew Morton <akpm@...ux-foundation.org>,
Gioh Kim <gurugio@...mail.net>
Subject: Re: [RFCv3 2/5] mm/compaction: enable mobile-page migration
>> @@ -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.
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