mm: memory-hotplug: enable memory hotplug to handle hugepage

Until now we can't offline memory blocks which contain hugepages because a
hugepage is considered as an unmovable page.  But now with this patch
series, a hugepage has become movable, so by using hugepage migration we
can offline such memory blocks.

What's different from other users of hugepage migration is that we need to
decompose all the hugepages inside the target memory block into free buddy
pages after hugepage migration, because otherwise free hugepages remaining
in the memory block intervene the memory offlining.  For this reason we
introduce new functions dissolve_free_huge_page() and
dissolve_free_huge_pages().

Other than that, what this patch does is straightforwardly to add hugepage
migration code, that is, adding hugepage code to the functions which scan
over pfn and collect hugepages to be migrated, and adding a hugepage
allocation function to alloc_migrate_target().

As for larger hugepages (1GB for x86_64), it's not easy to do hotremove
over them because it's larger than memory block.  So we now simply leave
it to fail as it is.

[yongjun_wei@trendmicro.com.cn: remove duplicated include]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index d1db00790a84..2e02c4ed1035 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -68,6 +68,7 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed);
 int dequeue_hwpoisoned_huge_page(struct page *page);
 bool isolate_huge_page(struct page *page, struct list_head *list);
 void putback_active_hugepage(struct page *page);
+bool is_hugepage_active(struct page *page);
 void copy_huge_page(struct page *dst, struct page *src);
 
 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
@@ -138,6 +139,7 @@ static inline int dequeue_hwpoisoned_huge_page(struct page *page)
 
 #define isolate_huge_page(p, l) false
 #define putback_active_hugepage(p)      do {} while (0)
+#define is_hugepage_active(x)   false
 static inline void copy_huge_page(struct page *dst, struct page *src)
 {
 }
@@ -377,6 +379,9 @@ static inline pgoff_t basepage_index(struct page *page)
         return __basepage_index(page);
 }
 
+extern void dissolve_free_huge_pages(unsigned long start_pfn,
+                                     unsigned long end_pfn);
+
 #else   /* CONFIG_HUGETLB_PAGE */
 struct hstate {};
 #define alloc_huge_page_node(h, nid) NULL
@@ -403,6 +408,7 @@ static inline pgoff_t basepage_index(struct page *page)
 {
         return page->index;
 }
+#define dissolve_free_huge_pages(s, e)  do {} while (0)
 #endif  /* CONFIG_HUGETLB_PAGE */
 
 #endif /* _LINUX_HUGETLB_H */