HWPOISON, hugetlb: add free check to dequeue_hwpoison_huge_page()

This check is necessary to avoid race between dequeue and allocation,
which can cause a free hugepage to be dequeued twice and get kernel unstable.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

1 files changed, 25 insertions, 4 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0fa9de8361bd..deb7bebefe68 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2955,18 +2955,39 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
         hugetlb_acct_memory(h, -(chg - freed));
 }
 
+/* Should be called in hugetlb_lock */
+static int is_hugepage_on_freelist(struct page *hpage)
+{
+        struct page *page;
+        struct page *tmp;
+        struct hstate *h = page_hstate(hpage);
+        int nid = page_to_nid(hpage);
+
+        list_for_each_entry_safe(page, tmp, &h->hugepage_freelists[nid], lru)
+                if (page == hpage)
+                        return 1;
+        return 0;
+}
+
+#ifdef CONFIG_MEMORY_FAILURE
 /*
  * This function is called from memory failure code.
  * Assume the caller holds page lock of the head page.
  */
-void __isolate_hwpoisoned_huge_page(struct page *hpage)
+int dequeue_hwpoisoned_huge_page(struct page *hpage)
 {
         struct hstate *h = page_hstate(hpage);
         int nid = page_to_nid(hpage);
+        int ret = -EBUSY;
 
         spin_lock(&hugetlb_lock);
-        list_del(&hpage->lru);
-        h->free_huge_pages--;
-        h->free_huge_pages_node[nid]--;
+        if (is_hugepage_on_freelist(hpage)) {
+                list_del(&hpage->lru);
+                h->free_huge_pages--;
+                h->free_huge_pages_node[nid]--;
+                ret = 0;
+        }
         spin_unlock(&hugetlb_lock);
+        return ret;
 }
+#endif