mm/hugetlb.c: fix warning on freeing hwpoisoned hugepage

Fix the warning from __list_del_entry() which is triggered when a process
tries to do free_huge_page() for a hwpoisoned hugepage.

free_huge_page() can be called for hwpoisoned hugepage from
unpoison_memory().  This function gets refcount once and clears
PageHWPoison, and then puts refcount twice to return the hugepage back to
free pool.  The second put_page() finally reaches free_huge_page().

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.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 e53f39cd67dba964cc9c651d32d82e55e32f5377..22508ef943e6ba841a06f3516a81918b4795301d 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3172,7 +3172,13 @@ int dequeue_hwpoisoned_huge_page(struct page *hpage)
 
        spin_lock(&hugetlb_lock);
        if (is_hugepage_on_freelist(hpage)) {
-               list_del(&hpage->lru);
+               /*
+                * Hwpoisoned hugepage isn't linked to activelist or freelist,
+                * but dangling hpage->lru can trigger list-debug warnings
+                * (this happens when we call unpoison_memory() on it),
+                * so let it point to itself with list_del_init().
+                */
+               list_del_init(&hpage->lru);
                set_page_refcounted(hpage);
                h->free_huge_pages--;
                h->free_huge_pages_node[nid]--;