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[209.132.180.67]) by mx.google.com with ESMTP id w4si897874otq.144.2020.02.06.19.11.14; Thu, 06 Feb 2020 19:11:27 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=INKYZ4Nx; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726755AbgBGDKV (ORCPT + 99 others); Thu, 6 Feb 2020 22:10:21 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:28926 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726509AbgBGDKV (ORCPT ); Thu, 6 Feb 2020 22:10:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581045020; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ewJLTC6LRmSKJd248CeUIvVW+fCQGBNVg2u0Qpt8QYU=; b=INKYZ4NxGJvRlPPArc1eQ/a4Ew7nplHrG6JLGJu9j/tLTvmnteb6qMhbgGbrfNX/Av1X2u F2+psqfz2hc0nLAqXaBV+3vNqXg0bNG62W9xPKQBzW17RbW8oLYnpvY4wnZlqM5RtbpvAd I361BUfE76FZWO1SolBB5rLrLiUevQY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-45-7_6eto-FNlqE8-gl1Fjh0A-1; Thu, 06 Feb 2020 22:10:19 -0500 X-MC-Unique: 7_6eto-FNlqE8-gl1Fjh0A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7AC661084420; Fri, 7 Feb 2020 03:10:17 +0000 (UTC) Received: from localhost (ovpn-12-30.pek2.redhat.com [10.72.12.30]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5334910016DA; Fri, 7 Feb 2020 03:10:14 +0000 (UTC) Date: Fri, 7 Feb 2020 11:10:11 +0800 From: Baoquan He To: Dan Williams Cc: Wei Yang , Andrew Morton , Oscar Salvador , Linux MM , Linux Kernel Mailing List , David Hildenbrand Subject: Re: [PATCH 2/3] mm/sparsemem: get physical address to page struct instead of virtual address to pfn Message-ID: <20200207031011.GR8965@MiWiFi-R3L-srv> References: <20200206231629.14151-1-richardw.yang@linux.intel.com> <20200206231629.14151-3-richardw.yang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dan, On 02/06/20 at 06:19pm, Dan Williams wrote: > On Thu, Feb 6, 2020 at 3:17 PM Wei Yang wrote: > > diff --git a/mm/sparse.c b/mm/sparse.c > > index b5da121bdd6e..56816f653588 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -888,7 +888,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, > > /* Align memmap to section boundary in the subsection case */ > > if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && > > section_nr_to_pfn(section_nr) != start_pfn) > > - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr)); > > + memmap = pfn_to_page(section_nr_to_pfn(section_nr)); > > Yes, this looks obviously correct. This might be tripping up > makedumpfile. Do you see any practical effects of this bug? The kernel > mostly avoids ->section_mem_map in the vmemmap case and in the > !vmemmap case section_nr_to_pfn(section_nr) should always equal > start_pfn. The practical effects is that the memmap for the first unaligned section will be lost when destroy namespace to hot remove it. Because we encode the ->section_mem_map into mem_section, and get memmap from the related mem_section to free it in section_deactivate(). In fact in vmemmap, we don't need to encode the ->section_mem_map with memmap. By the way, sub-section support is only valid in vmemmap case, right? Seems yes from code, but I don't find any document to prove it. Thanks Baoquan