From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-f70.google.com (mail-ot1-f70.google.com [209.85.210.70]) by kanga.kvack.org (Postfix) with ESMTP id 07C7F6B06E0 for ; Fri, 9 Nov 2018 05:47:02 -0500 (EST) Received: by mail-ot1-f70.google.com with SMTP id g28so835407otd.19 for ; Fri, 09 Nov 2018 02:47:02 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id v34si2996195oti.39.2018.11.09.02.47.00 for ; Fri, 09 Nov 2018 02:47:00 -0800 (PST) Subject: Re: [RFC][PATCH v1 04/11] mm: madvise: call soft_offline_page() without MF_COUNT_INCREASED References: <1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1541746035-13408-5-git-send-email-n-horiguchi@ah.jp.nec.com> From: Anshuman Khandual Message-ID: <21e5b9ca-ad72-b0d5-3397-4b65831b236b@arm.com> Date: Fri, 9 Nov 2018 16:16:55 +0530 MIME-Version: 1.0 In-Reply-To: <1541746035-13408-5-git-send-email-n-horiguchi@ah.jp.nec.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Michal Hocko , Andrew Morton , Mike Kravetz , xishi.qiuxishi@alibaba-inc.com, Laurent Dufour On 11/09/2018 12:17 PM, Naoya Horiguchi wrote: > Currently madvise_inject_error() pins the target page when calling > memory error handler, but it's not good because the refcount is just > an artifact of error injector and mock nothing about hw error itself. > IOW, pinning the error page is part of error handler's task, so > let's stop doing it. Did not get that. Could you please kindly explain how an incremented ref count through get_user_pages_fast() was a mocking the HW error previously ? Though I might be missing the some context here. > > Signed-off-by: Naoya Horiguchi > --- > mm/madvise.c | 25 +++++++++++-------------- > 1 file changed, 11 insertions(+), 14 deletions(-) > > diff --git v4.19-mmotm-2018-10-30-16-08/mm/madvise.c v4.19-mmotm-2018-10-30-16-08_patched/mm/madvise.c > index 6cb1ca9..9fa0225 100644 > --- v4.19-mmotm-2018-10-30-16-08/mm/madvise.c > +++ v4.19-mmotm-2018-10-30-16-08_patched/mm/madvise.c > @@ -637,6 +637,16 @@ static int madvise_inject_error(int behavior, > ret = get_user_pages_fast(start, 1, 0, &page); > if (ret != 1) > return ret; > + /* > + * The get_user_pages_fast() is just to get the pfn of the > + * given address, and the refcount has nothing to do with > + * what we try to test, so it should be released immediately. > + * This is racy but it's intended because the real hardware > + * errors could happen at any moment and memory error handlers > + * must properly handle the race. > + */ > + put_page(page); > + > pfn = page_to_pfn(page); > > /* > @@ -646,16 +656,11 @@ static int madvise_inject_error(int behavior, > */ > order = compound_order(compound_head(page)); > > - if (PageHWPoison(page)) { > - put_page(page); > - continue; > - } > - > if (behavior == MADV_SOFT_OFFLINE) { > pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n", > pfn, start); > > - ret = soft_offline_page(page, MF_COUNT_INCREASED); > + ret = soft_offline_page(page, 0); Probably something defined as a new "ignored" in the memory faults flag enumeration instead of passing '0' directly.