[PATCH v2 01/20] mm, hugetlb: protect reserved pages when soft offlining a hugepage

[Joonsoo Kim]

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.

Reviewed-by: Aneesh Kumar <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6782b41..d971233 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -935,10 +935,11 @@ 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)
-- 
1.7.9.5

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