(added [email protected] to CC)
On Tue, 11 Feb 2014 12:35:54 -0800 [email protected] wrote:
> Subject: + mm-thp-fix-infinite-loop-on-memcg-oom.patch added to -mm tree
> To:
> [email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
> From: [email protected]
> Date: Tue, 11 Feb 2014 12:35:54 -0800
>
>
> The patch titled
> Subject: mm, thp: fix infinite loop on memcg OOM
> has been added to the -mm tree. Its filename is
> mm-thp-fix-infinite-loop-on-memcg-oom.patch
>
> This patch should soon appear at
>
> http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-fix-infinite-loop-on-memcg-oom.patch
> and later at
>
> http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-fix-infinite-loop-on-memcg-oom.patch
>
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>
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
>
> ------------------------------------------------------
> From: "Kirill A. Shutemov" <[email protected]>
> Subject: mm, thp: fix infinite loop on memcg OOM
>
> Masayoshi Mizuma reported a bug with the hang of an application under the
> memcg limit. It happens on write-protection fault to huge zero page
>
> If we successfully allocate a huge page to replace zero page but hit the
> memcg limit we need to split the zero page with split_huge_page_pmd() and
> fallback to small pages.
>
> The other part of the problem is that VM_FAULT_OOM has special meaning in
> do_huge_pmd_wp_page() context. __handle_mm_fault() expects the page to be
> split if it sees VM_FAULT_OOM and it will will retry page fault handling.
> This causes an infinite loop if the page was not split.
>
> do_huge_pmd_wp_zero_page_fallback() can return VM_FAULT_OOM if it failed
> to allocate one small page, so fallback to small pages will not help.
>
> The solution for this part is to replace VM_FAULT_OOM with
> VM_FAULT_FALLBACK is fallback required.
>
> Signed-off-by: Kirill A. Shutemov <[email protected]>
> Reported-by: Masayoshi Mizuma <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Johannes Weiner <[email protected]>
> Cc: Andrea Arcangeli <[email protected]>
> Cc: David Rientjes <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> ---
I believe this patch should be backported to stable tree.
Regards,
Masayoshi Mizuma
>
> mm/huge_memory.c | 9 ++++++---
> mm/memory.c | 14 +++-----------
> 2 files changed, 9 insertions(+), 14 deletions(-)
>
> diff -puN mm/huge_memory.c~mm-thp-fix-infinite-loop-on-memcg-oom
> mm/huge_memory.c
> --- a/mm/huge_memory.c~mm-thp-fix-infinite-loop-on-memcg-oom
> +++ a/mm/huge_memory.c
> @@ -1166,8 +1166,10 @@ alloc:
> } else {
> ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
> pmd, orig_pmd, page, haddr);
> - if (ret & VM_FAULT_OOM)
> + if (ret & VM_FAULT_OOM) {
> split_huge_page(page);
> + ret |= VM_FAULT_FALLBACK;
> + }
> put_page(page);
> }
> count_vm_event(THP_FAULT_FALLBACK);
> @@ -1179,9 +1181,10 @@ alloc:
> if (page) {
> split_huge_page(page);
> put_page(page);
> - }
> + } else
> + split_huge_page_pmd(vma, address, pmd);
> + ret |= VM_FAULT_FALLBACK;
> count_vm_event(THP_FAULT_FALLBACK);
> - ret |= VM_FAULT_OOM;
> goto out;
> }
>
> diff -puN mm/memory.c~mm-thp-fix-infinite-loop-on-memcg-oom mm/memory.c
> --- a/mm/memory.c~mm-thp-fix-infinite-loop-on-memcg-oom
> +++ a/mm/memory.c
> @@ -3704,7 +3704,6 @@ static int __handle_mm_fault(struct mm_s
> if (unlikely(is_vm_hugetlb_page(vma)))
> return hugetlb_fault(mm, vma, address, flags);
>
> -retry:
> pgd = pgd_offset(mm, address);
> pud = pud_alloc(mm, pgd, address);
> if (!pud)
> @@ -3742,20 +3741,13 @@ retry:
> if (dirty && !pmd_write(orig_pmd)) {
> ret = do_huge_pmd_wp_page(mm, vma, address, pmd,
> orig_pmd);
> - /*
> - * If COW results in an oom, the huge pmd will
> - * have been split, so retry the fault on the
> - * pte for a smaller charge.
> - */
> - if (unlikely(ret & VM_FAULT_OOM))
> - goto retry;
> - return ret;
> + if (!(ret & VM_FAULT_FALLBACK))
> + return ret;
> } else {
> huge_pmd_set_accessed(mm, vma, address, pmd,
> orig_pmd, dirty);
> + return 0;
> }
> -
> - return 0;
> }
> }
>
> _
>
> Patches currently in -mm which might be from [email protected]
> are
>
> mm-hwpoison-release-page-on-pagehwpoison-in-__do_fault.patch
> mm-thp-fix-infinite-loop-on-memcg-oom.patch
> pagewalk-update-page-table-walker-core.patch
> pagewalk-add-walk_page_vma.patch
> smaps-redefine-callback-functions-for-page-table-walker.patch
> clear_refs-redefine-callback-functions-for-page-table-walker.patch
> pagemap-redefine-callback-functions-for-page-table-walker.patch
> numa_maps-redefine-callback-functions-for-page-table-walker.patch
> memcg-redefine-callback-functions-for-page-table-walker.patch
> madvise-redefine-callback-functions-for-page-table-walker.patch
> arch-powerpc-mm-subpage-protc-use-walk_page_vma-instead-of-walk_page_range.patch
> pagewalk-remove-argument-hmask-from-hugetlb_entry.patch
> mempolicy-apply-page-table-walker-on-queue_pages_range.patch
> mm-rename-__do_fault-do_fault.patch
> mm-do_fault-extract-to-call-vm_ops-do_fault-to-separate-function.patch
> mm-introduce-do_read_fault.patch
> mm-introduce-do_cow_fault.patch
> mm-introduce-do_shared_fault-and-drop-do_fault.patch
> mm-consolidate-code-to-call-vm_ops-page_mkwrite.patch
> mm-consolidate-code-to-setup-pte.patch
> mm-thp-drop-do_huge_pmd_wp_zero_page_fallback.patch
>
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