mm, hugetlb: protect reserved pages when soft offlining a hugepage

Don't use the reserve pool when soft offlining a hugepage.  Check we have
free pages outside the reserve pool before we dequeue the huge page.
Otherwise, we can steal other's reserve page.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5b084c7b34c6ba2232d4afcfc8729d3b87b65f5b..583db19481454d2cb04eed66b34710d99d378cc1 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -955,10 +955,11 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
  */
 struct page *alloc_huge_page_node(struct hstate *h, int nid)
 {
-       struct page *page;
+       struct page *page = NULL;
 
        spin_lock(&hugetlb_lock);
-       page = dequeue_huge_page_node(h, nid);
+       if (h->free_huge_pages - h->resv_huge_pages > 0)
+               page = dequeue_huge_page_node(h, nid);
        spin_unlock(&hugetlb_lock);
 
        if (!page)