HWPOISON, hugetlb: detect hwpoison in hugetlb code

This patch enables to block access to hwpoisoned hugepage and
also enables to block unmapping for it.

Dependency:
  "HWPOISON, hugetlb: enable error handling path for hugepage"

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8c163f64cf1076ce6b3fed95ad5ee0e30990eada..4c2efc0f3919b8c31176e330ab74b38b022d00ac 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -19,6 +19,8 @@
 #include <linux/sysfs.h>
 #include <linux/slab.h>
 #include <linux/rmap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -2149,6 +2151,19 @@ nomem:
        return -ENOMEM;
 }
 
+static int is_hugetlb_entry_hwpoisoned(pte_t pte)
+{
+       swp_entry_t swp;
+
+       if (huge_pte_none(pte) || pte_present(pte))
+               return 0;
+       swp = pte_to_swp_entry(pte);
+       if (non_swap_entry(swp) && is_hwpoison_entry(swp)) {
+               return 1;
+       } else
+               return 0;
+}
+
 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
                            unsigned long end, struct page *ref_page)
 {
@@ -2207,6 +2222,12 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
                if (huge_pte_none(pte))
                        continue;
 
+               /*
+                * HWPoisoned hugepage is already unmapped and dropped reference
+                */
+               if (unlikely(is_hugetlb_entry_hwpoisoned(pte)))
+                       continue;
+
                page = pte_page(pte);
                if (pte_dirty(pte))
                        set_page_dirty(page);
@@ -2490,6 +2511,18 @@ retry:
                page_dup_rmap(page);
        }
 
+       /*
+        * Since memory error handler replaces pte into hwpoison swap entry
+        * at the time of error handling, a process which reserved but not have
+        * the mapping to the error hugepage does not have hwpoison swap entry.
+        * So we need to block accesses from such a process by checking
+        * PG_hwpoison bit here.
+        */
+       if (unlikely(PageHWPoison(page))) {
+               ret = VM_FAULT_HWPOISON;
+               goto backout_unlocked;
+       }
+
        /*
         * If we are going to COW a private mapping later, we examine the
         * pending reservations for this page now. This will ensure that
@@ -2544,6 +2577,13 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
        static DEFINE_MUTEX(hugetlb_instantiation_mutex);
        struct hstate *h = hstate_vma(vma);
 
+       ptep = huge_pte_offset(mm, address);
+       if (ptep) {
+               entry = huge_ptep_get(ptep);
+               if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
+                       return VM_FAULT_HWPOISON;
+       }
+
        ptep = huge_pte_alloc(mm, address, huge_page_size(h));
        if (!ptep)
                return VM_FAULT_OOM;