thp: fix splitting of hwpoisoned hugepages

[deliverable/linux.git] / mm / memory-failure.c

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 237aaa488f4eab4682be86800740c94e44191852..1e9c30b241c3697d1cb4d57fc855e71819183e0b 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -386,8 +386,6 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
        struct task_struct *tsk;
        struct anon_vma *av;
 
-       if (!PageHuge(page) && unlikely(split_huge_page(page)))
-               return;
        read_lock(&tasklist_lock);
        av = page_lock_anon_vma(page);
        if (av == NULL) /* Not actually mapped anymore */
@@ -896,6 +894,34 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
                }
        }
 
+       if (PageTransHuge(hpage)) {
+               /*
+                * Verify that this isn't a hugetlbfs head page, the check for
+                * PageAnon is just for avoid tripping a split_huge_page
+                * internal debug check, as split_huge_page refuses to deal with
+                * anything that isn't an anon page. PageAnon can't go away fro
+                * under us because we hold a refcount on the hpage, without a
+                * refcount on the hpage. split_huge_page can't be safely called
+                * in the first place, having a refcount on the tail isn't
+                * enough * to be safe.
+                */
+               if (!PageHuge(hpage) && PageAnon(hpage)) {
+                       if (unlikely(split_huge_page(hpage))) {
+                               /*
+                                * FIXME: if splitting THP is failed, it is
+                                * better to stop the following operation rather
+                                * than causing panic by unmapping. System might
+                                * survive if the page is freed later.
+                                */
+                               printk(KERN_INFO
+                                       "MCE %#lx: failed to split THP\n", pfn);
+
+                               BUG_ON(!PageHWPoison(p));
+                               return SWAP_FAIL;
+                       }
+               }
+       }
+
        /*
         * First collect all the processes that have the page
         * mapped in dirty form.  This has to be done before try_to_unmap,