From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 5BA726B0037 for ; Tue, 11 Feb 2014 12:24:32 -0500 (EST) Received: by mail-pa0-f46.google.com with SMTP id rd3so7979578pab.33 for ; Tue, 11 Feb 2014 09:24:32 -0800 (PST) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTP id m8si19654087pbq.269.2014.02.11.09.24.29 for ; Tue, 11 Feb 2014 09:24:31 -0800 (PST) From: "Kirill A. Shutemov" Subject: [PATCH] mm, thp: fix infinite loop on memcg OOM Date: Tue, 11 Feb 2014 19:24:11 +0200 Message-Id: <1392139451-15446-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: m.mizuma@jp.fujitsu.com, mhocko@suse.cz, aarcange@redhat.com, linux-mm@kvack.org, "Kirill A. Shutemov" Masayoshi Mizuma has reported bug with hung of application under memcg limit. It happens on write-protection fault to huge zero page If we successfully allocate huge page to replace zero page, but hit memcg limit we need to split zero page with split_huge_page_pmd() and fallback to small pages. Other part 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 see VM_FAULT_OOM and it will will retry page fault handling. It causes infinite loop if the page was not split. do_huge_pmd_wp_zero_page_fallback() can return VM_FAULT_OOM if it failed to allocat 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 Reported-by: Masayoshi Mizuma --- mm/huge_memory.c | 9 ++++++--- mm/memory.c | 14 +++----------- 2 files changed, 9 insertions(+), 14 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 82166bf974e1..65a88bef8694 100644 --- a/mm/huge_memory.c +++ b/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 --git a/mm/memory.c b/mm/memory.c index be6a0c0d4ae0..3b57b7864667 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3703,7 +3703,6 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, 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) @@ -3741,20 +3740,13 @@ 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; } } -- 1.8.5.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org