From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFA93C352A3 for ; Thu, 6 Feb 2020 22:14:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 766A4217BA for ; Thu, 6 Feb 2020 22:14:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 766A4217BA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B541D6B0003; Thu, 6 Feb 2020 17:14:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B05D86B0006; Thu, 6 Feb 2020 17:14:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9FB6B6B0007; Thu, 6 Feb 2020 17:14:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0046.hostedemail.com [216.40.44.46]) by kanga.kvack.org (Postfix) with ESMTP id 860F76B0003 for ; Thu, 6 Feb 2020 17:14:54 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 46BD2180AD801 for ; Thu, 6 Feb 2020 22:14:54 +0000 (UTC) X-FDA: 76461108108.24.fear35_2ab7a56019d58 X-HE-Tag: fear35_2ab7a56019d58 X-Filterd-Recvd-Size: 4729 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by imf32.hostedemail.com (Postfix) with ESMTP for ; Thu, 6 Feb 2020 22:14:53 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Feb 2020 14:14:51 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,411,1574150400"; d="scan'208";a="404626475" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga005.jf.intel.com with ESMTP; 06 Feb 2020 14:14:49 -0800 Date: Fri, 7 Feb 2020 06:15:06 +0800 From: Wei Yang To: David Hildenbrand Cc: Baoquan He , Wei Yang , akpm@linux-foundation.org, osalvador@suse.de, dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM Message-ID: <20200206221506.GA8863@richard> Reply-To: Wei Yang References: <20200206125343.9070-1-richardw.yang@linux.intel.com> <6d9e36cb-ee4a-00c8-447b-9b75a0262c3a@redhat.com> <20200206135016.GA25537@MiWiFi-R3L-srv> <87bb4563-481d-cce9-b916-50a098558210@redhat.com> <20200206140703.GB25537@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 06, 2020 at 03:37:40PM +0100, David Hildenbrand wrote: >On 06.02.20 15:07, Baoquan He wrote: >> On 02/06/20 at 02:55pm, David Hildenbrand wrote: >>> On 06.02.20 14:50, Baoquan He wrote: >>>> On 02/06/20 at 02:28pm, David Hildenbrand wrote: >>>>> On 06.02.20 13:53, Wei Yang wrote: >>>>>> When we use SPARSEMEM instead of SPARSEMEM_VMEMMAP, pfn_to_page() >>>>>> doesn't work before sparse_init_one_section() is called. This leads to a >>>>>> crash when hotplug memory. >>>>>> >>>>>> We should use memmap as it did. >>>>>> >>>>>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >>>>>> Signed-off-by: Wei Yang >>>>>> CC: Dan Williams >>>>>> --- >>>>>> mm/sparse.c | 2 +- >>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/mm/sparse.c b/mm/sparse.c >>>>>> index 5a8599041a2a..2efb24ff8f96 100644 >>>>>> --- a/mm/sparse.c >>>>>> +++ b/mm/sparse.c >>>>>> @@ -882,7 +882,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, >>>>>> * Poison uninitialized struct pages in order to catch invalid flags >>>>>> * combinations. >>>>>> */ >>>>>> - page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages); >>>>>> + page_init_poison(memmap, sizeof(struct page) * nr_pages); >>>>> >>>>> If you add sub-sections that don't fall onto the start of the section, >>>>> >>>>> pfn_to_page(start_pfn) != memmap >>>>> >>>>> and your patch would break that under SPARSEMEM_VMEMMAP if I am not wrong. >>>> >>>> It returns the pfn_to_page(pfn) from __populate_section_memmap() and >>>> assign to memmap in vmemmap case, how come it breaks anything. Correct >>>> me if I was wrong. >>> >>> I'm sorry, I can't follow :) Can you elaborate? >>> >>> Was your comment targeted at why the old code cannot be broken or why >>> this patch cannot be broken? >> >> Sorry for the confusion :-) the latter. I mean the returned memmap has been >> at the pfn_to_page(start_pfn) in SPARSEMEM_VMEMMAP case. > >Yeah, at least for SPARSEMEM_VMEMMAP it is indeed right. Thanks :) > > >Now, about SPARSEMEM: > >populate_section_memmap() does not care about nr_pages and will allocate >a memmap for the whole section. So, whenever we add sub-sections to a >section, we allocate a new memmap for the whole section. And we do >overwrite the memmap pointer in our section. ( sparse_add_section() ) > >That makes me assume that sub-section hot-add under SPARSEMEM is either > >a) never enabled and only works with SPARSEMEM_VMEMMAP >b) horribly broken > >And I think a) applies (looking at pfn_section_valid()). Therefore, we >don't have to care about sub-section hot-add specifics (and I would be >broken already) Yes, I am looking into this problem. Actually, there maybe another problem. Just get my brain refreshed, need some time to dig into. > >Acked-by: David Hildenbrand > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me