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    Subject[PATCH 7/8] HWPOISON, hugetlb: detect hwpoison in hugetlb code
    Date
    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: Andi Kleen <andi@firstfloor.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Wu Fengguang <fengguang.wu@intel.com>
    ---
    mm/hugetlb.c | 40 ++++++++++++++++++++++++++++++++++++++++
    1 files changed, 40 insertions(+), 0 deletions(-)

    diff --git v2.6.34/mm/hugetlb.c v2.6.34/mm/hugetlb.c
    index aaba3cc..5580568 100644
    --- v2.6.34/mm/hugetlb.c
    +++ v2.6.34/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>
    @@ -2145,6 +2147,19 @@ 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)
    {
    @@ -2203,6 +2218,12 @@ 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);
    @@ -2487,6 +2508,18 @@ retry:
    }

    /*
    + * 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
    * any allocations necessary to record that reservation occur outside
    @@ -2540,6 +2573,13 @@ 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;
    --
    1.7.0


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