Commit 6b970599 authored by Kefeng Wang's avatar Kefeng Wang Committed by Andrew Morton
Browse files

mm: hwpoison: support recovery from ksm_might_need_to_copy() 

When the kernel copies 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 the issue recently fixed by Copy-on-write
poison recovery.

When an error is detected during the page copy, return VM_FAULT_HWPOISON
in do_swap_page(), and install a hwpoison entry in unuse_pte() when
swapoff, 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, and we could support KSM
page recovery in the feature.

[wangkefeng.wang@huawei.com: enhance unuse_pte(), fix issue found by lkp]
  Link: https://lkml.kernel.org/r/20221213120523.141588-1-wangkefeng.wang@huawei.com
[wangkefeng.wang@huawei.com: update changelog, alter ksm_might_need_to_copy(), restore unlikely() in unuse_pte()]
  Link: https://lkml.kernel.org/r/20230201074433.96641-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20221209072801.193221-1-wangkefeng.wang@huawei.com


Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: default avatarNaoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 55d77bae

mm/ksm.c

+5 −2
Original line number Diff line number Diff line
@@ -2629,8 +2629,11 @@ 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);

			memory_failure_queue(page_to_pfn(page), 0);

			return ERR_PTR(-EHWPOISON);

		}

		SetPageDirty(new_page);

		__SetPageUptodate(new_page);

		__SetPageLocked(new_page);

mm/memory.c

+3 −0
Original line number Diff line number Diff line
@@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) 
		if (unlikely(!page)) {

			ret = VM_FAULT_OOM;

			goto out_page;

		} else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {

			ret = VM_FAULT_HWPOISON;

			goto out_page;

		}

		folio = page_folio(page);

mm/swapfile.c

+14 −6
Original line number Diff line number Diff line
@@ -1764,12 +1764,15 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 
	struct page *swapcache;

	spinlock_t *ptl;

	pte_t *pte, new_pte;

	bool hwposioned = false;

	int ret = 1;



	swapcache = page;

	page = ksm_might_need_to_copy(page, vma, addr);

	if (unlikely(!page))

		return -ENOMEM;

	else if (unlikely(PTR_ERR(page) == -EHWPOISON))

		hwposioned = true;



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

	if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) {
@@ -1777,15 +1780,19 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 
		goto out;

	}



	if (unlikely(!PageUptodate(page))) {

		pte_t pteval;

	if (unlikely(hwposioned || !PageUptodate(page))) {

		swp_entry_t swp_entry;



		dec_mm_counter(vma->vm_mm, MM_SWAPENTS);

		pteval = swp_entry_to_pte(make_swapin_error_entry());

		set_pte_at(vma->vm_mm, addr, pte, pteval);

		swap_free(entry);

		if (hwposioned) {

			swp_entry = make_hwpoison_entry(swapcache);

			page = swapcache;

		} else {

			swp_entry = make_swapin_error_entry();

		}

		new_pte = swp_entry_to_pte(swp_entry);

		ret = 0;

		goto out;

		goto setpte;

	}



	/* See do_swap_page() */
@@ -1817,6 +1824,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 
		new_pte = pte_mksoft_dirty(new_pte);

	if (pte_swp_uffd_wp(*pte))

		new_pte = pte_mkuffd_wp(new_pte);

setpte:

	set_pte_at(vma->vm_mm, addr, pte, new_pte);

	swap_free(entry);

out: