From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f182.google.com (mail-we0-f182.google.com [74.125.82.182]) by kanga.kvack.org (Postfix) with ESMTP id 7E9356B0031 for ; Wed, 12 Feb 2014 11:59:31 -0500 (EST) Received: by mail-we0-f182.google.com with SMTP id u57so6344091wes.27 for ; Wed, 12 Feb 2014 08:59:30 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id cp4si1848116wib.20.2014.02.12.08.59.28 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 12 Feb 2014 08:59:29 -0800 (PST) Date: Wed, 12 Feb 2014 17:59:27 +0100 From: Michal Hocko Subject: Re: [PATCH] mm, thp: fix infinite loop on memcg OOM Message-ID: <20140212165927.GE28085@dhcp22.suse.cz> References: <1392139451-15446-1-git-send-email-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392139451-15446-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Andrew Morton , m.mizuma@jp.fujitsu.com, aarcange@redhat.com, linux-mm@kvack.org On Tue 11-02-14 19:24:11, Kirill A. Shutemov wrote: > 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 FWIW Reviewed-by: Michal Hocko > --- > 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 > -- Michal Hocko SUSE Labs -- 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