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    Subject[PATCH] mm: hwposion: support recovery from ksm_might_need_to_copy()
    Date
    When the kernel copy a page from ksm_might_need_to_copy(), but runs
    into an uncorrectable error, it will crash since poisoned page is
    consumed by kernel, this is similar to Copy-on-write poison recovery,
    When an error is detected during the page copy, return VM_FAULT_HWPOISON,
    which help us to avoid system crash. Note, memory failure on a KSM
    page will be skipped, but still call memory_failure_queue() to be
    consistent with general memory failure process.

    Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
    ---
    mm/ksm.c | 8 ++++++--
    mm/memory.c | 3 +++
    mm/swapfile.c | 2 +-
    3 files changed, 10 insertions(+), 3 deletions(-)

    diff --git a/mm/ksm.c b/mm/ksm.c
    index f1e06b1d47f3..356e93b85287 100644
    --- a/mm/ksm.c
    +++ b/mm/ksm.c
    @@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
    new_page = NULL;
    }
    if (new_page) {
    - copy_user_highpage(new_page, page, address, vma);
    -
    + if (copy_mc_user_highpage(new_page, page, address, vma)) {
    + put_page(new_page);
    + new_page = ERR_PTR(-EHWPOISON);
    + memory_failure_queue(page_to_pfn(page), 0);
    + return new_page;
    + }
    SetPageDirty(new_page);
    __SetPageUptodate(new_page);
    __SetPageLocked(new_page);
    diff --git a/mm/memory.c b/mm/memory.c
    index 2615fa615be4..bb7b35e42297 100644
    --- a/mm/memory.c
    +++ b/mm/memory.c
    @@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
    if (unlikely(!page)) {
    ret = VM_FAULT_OOM;
    goto out_page;
    + } els if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
    + ret = VM_FAULT_HWPOISON;
    + goto out_page;
    }
    folio = page_folio(page);

    diff --git a/mm/swapfile.c b/mm/swapfile.c
    index f670ffb7df7e..763ff6a8a576 100644
    --- a/mm/swapfile.c
    +++ b/mm/swapfile.c
    @@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,

    swapcache = page;
    page = ksm_might_need_to_copy(page, vma, addr);
    - if (unlikely(!page))
    + if (IS_ERR_OR_NULL(!page))
    return -ENOMEM;

    pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
    --
    2.35.3
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