linux-kernel - Re: [PATCH] mm: hwposion: support recovery from ksm_might_need_to

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Date:   Fri, 9 Dec 2022 09:56:16 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     <naoya.horiguchi@....com>, <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>
CC:     <tony.luck@...el.com>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: Re: [PATCH] mm: hwposion: support recovery from
 ksm_might_need_to_copy()

sorry, please ignore it,  will resend.

On 2022/12/9 10:10, Kefeng Wang wrote:
> 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@...wei.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);