mm/hugetlb: fix incorrect hugepages count during mem hotplug

When memory hotplug operates, free hugepages will be freed if the
movable node is offline.  Therefore, /proc/sys/vm/nr_hugepages will be
incorrect.

Fix it by reducing max_huge_pages when the node is offlined.

n-horiguchi@ah.jp.nec.com said:

: dissolve_free_huge_page intends to break a hugepage into buddy, and the
: destination hugepage is supposed to be allocated from the pool of the
: destination node, so the system-wide pool size is reduced.  So adding
: h->max_huge_pages-- makes sense to me.

Link: http://lkml.kernel.org/r/1470624546-902-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index b9aa1b0b38b0..87e11d8ad536 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1448,6 +1448,7 @@ static void dissolve_free_huge_page(struct page *page)
                 list_del(&page->lru);
                 h->free_huge_pages--;
                 h->free_huge_pages_node[nid]--;
+                h->max_huge_pages--;
                 update_and_free_page(h, page);
         }
         spin_unlock(&hugetlb_lock);