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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 2E9AAC352A2 for ; Thu, 6 Feb 2020 13:57:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0348F214AF for ; Thu, 6 Feb 2020 13:57:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WyQ5OENC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727940AbgBFN5q (ORCPT ); Thu, 6 Feb 2020 08:57:46 -0500 Received: from mail-wr1-f65.google.com ([209.85.221.65]:35712 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727549AbgBFN5q (ORCPT ); Thu, 6 Feb 2020 08:57:46 -0500 Received: by mail-wr1-f65.google.com with SMTP id w12so7347313wrt.2 for ; Thu, 06 Feb 2020 05:57:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:reply-to:references:mime-version :content-disposition:in-reply-to:user-agent; bh=37rkqrVeTaF+mZnTFwvQ9NfsdsUskom+KVb6+jBTRMY=; b=WyQ5OENCxNDcGZer2tSh2fFvA+ujWZQVW0Sq1drxk3NvK4WXYuCVzMS4Smv+KqAv2q jQDLMZtpsPg4NhYE8M9W68qbyhtUrvTIQTC+BuqKz8imR2fZpnUZMFXJSEb7PcjYTvy5 EV9dzmxQGtj0j4kQgFL2pZONUoLumxjg7CQCL83LqUqDx2rzo7sPtslyido2PJil4Jc4 TZzxkwvMFwFdFdbyY58gZA0m+HGsuuBdeBGaix4P/8dNTpp7ZeqRx/4vbBeRCmEaxp0P 5ghXItAykEskc0tJ8bP4JkEd33Lb71kzA5KqkMGRl3GRncQOf4Di0xJFtKT7aBsrR9M4 776A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:reply-to :references:mime-version:content-disposition:in-reply-to:user-agent; bh=37rkqrVeTaF+mZnTFwvQ9NfsdsUskom+KVb6+jBTRMY=; b=UFIGvQYZtjPca73uoDGvFDXMaTv7Ks3+eSm3dWsr+9fBS1Uese+AK4MXGwCCTT+2PJ GsKHZwubaeY6CXMXoDxRIr+MO84R59ubVws+LNwtRVAmn4KdwZsPhI9RAQUvt8EuFS6x T9SZRc48yaxVFnYmxF6Eq0+YFvSO8fcDdZy73gFfzxaS+QvFAeb/7hER5f5Tc8nA8b6Y gsHxstBmy2Kt2dcWAeCiArZg7GN2XR1qJOp4OYhwIb8d61jpKeuwPOcds2Y7WWaZjY0f tnJXMH3+/Swutcq9KaNw3dA3gG2R/3QqgiItZYxgW44A89GFeb6G52T/L0Q++LN7rlpN S09A== X-Gm-Message-State: APjAAAVy0gINs27bNM6MQFztxb0LNNXk7Qi1/V/91w/6OJXI77nakwdC Le5TreZgsgQoN9+pDXQl8rQ= X-Google-Smtp-Source: APXvYqwbWl3cDVywFO+VJspZ918ynJg0D0jUj6fPi4athSnC627IC8hulvLKqsnFAgFRBTrSgVhHhA== X-Received: by 2002:adf:f787:: with SMTP id q7mr3922226wrp.297.1580997463195; Thu, 06 Feb 2020 05:57:43 -0800 (PST) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id 124sm4030148wmc.29.2020.02.06.05.57.42 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 06 Feb 2020 05:57:42 -0800 (PST) Date: Thu, 6 Feb 2020 13:57:42 +0000 From: Wei Yang To: David Hildenbrand Cc: Wei Yang , akpm@linux-foundation.org, osalvador@suse.de, dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bhe@redhat.com Subject: Re: [PATCH] mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM Message-ID: <20200206135742.454wgna4ta76yv5w@master> Reply-To: Wei Yang References: <20200206125343.9070-1-richardw.yang@linux.intel.com> <6d9e36cb-ee4a-00c8-447b-9b75a0262c3a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6d9e36cb-ee4a-00c8-447b-9b75a0262c3a@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 06, 2020 at 02:28:53PM +0100, 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. > >Instead of memmap, there would have to be something like > >memmap + (start_pfn - SECTION_ALIGN_DOWN(start_pfn)) > >If I am not wrong :) Hi, David, Thanks for your comment. To be hones, I am not familiar with SPARSEMEM_VMEMMAP. Here is my understanding about section_activate() when SPARSEMEM_VMEMMAP is set. section_activate(nid, start_pfn, nr_pages, altmap) populate_section_mmemap(start_pfn, nr_pages, nid, altmap) __populate_section_mmemap(start_pfn, nr_pages, nid, altmap) return pfn_to_page(start_pfn) So the memmap is the page struct for start_pfn when SPARSEMEM_VMEMMAP is set. Maybe I missed some critical part? > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me