Messages in this thread |  | | Date | Fri, 16 Dec 2022 16:42:34 +0800 | Subject | Re: [PATCH -next resend v3] mm: hwposion: support recovery from ksm_might_need_to_copy() | From | Kefeng Wang <> |
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On 2022/12/16 9:47, HORIGUCHI NAOYA(堀口 直也) wrote: > On Tue, Dec 13, 2022 at 08:05:23PM +0800, 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, > > Maybe you mean "this is similar to the issue recently fixed by > Copy-on-write poison recovery."? And if this sentence ends here, > please put "." instead of ",".
That what I mean, will update the changelog. > >> 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. > > Thank you for the work. I have a few comment below ... > >> >> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> >> --- >> v3 resend: >> - enhance unuse_pte() if ksm_might_need_to_copy() return -EHWPOISON >> - fix issue found by lkp >> >> mm/ksm.c | 8 ++++++-- >> mm/memory.c | 3 +++ >> mm/swapfile.c | 20 ++++++++++++++------ >> 3 files changed, 23 insertions(+), 8 deletions(-) >> >> diff --git a/mm/ksm.c b/mm/ksm.c >> index dd02780c387f..83e2f74ae7da 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; > > Simply return ERR_PTR(-EHWPOISON)?
OK.
> >> + } >> SetPageDirty(new_page); >> __SetPageUptodate(new_page); >> __SetPageLocked(new_page); >> diff --git a/mm/memory.c b/mm/memory.c >> index aad226daf41b..5b2c137dfb2a 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; >> + } else 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 908a529bca12..0efb1c2c2415 100644 >> --- a/mm/swapfile.c >> +++ b/mm/swapfile.c >> @@ -1763,12 +1763,15 @@ 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)))) { >> @@ -1776,15 +1779,19 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, >> goto out; >> } >> >> - if (unlikely(!PageUptodate(page))) { >> - pte_t pteval; >> + if (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; > > This might work for the process accessing to the broken page, but ksm > pages are likely to be shared by multiple processes, so it would be > much nicer if you can convert all mapping entries for the error ksm page > into hwpoisoned ones. Maybe in this thorough approach, > hwpoison_user_mappings() is updated to call try_to_unmap() for ksm pages. > But it's not necessary to do this together with applying mcsafe-memcpy, > because recovery action and mcsafe-memcpy can be done independently.
Yes, the memory failure won't handle KSM page (commit 01e00f880ca7 "HWPOISON: fix oops on ksm pages"), we could support it later,
> > Thanks, > Naoya Horiguchi > >> + } 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() */ >> @@ -1816,6 +1823,7 @@ 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: >> -- >> 2.35.3 > >
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