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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 268E5C2BB1D for ; Thu, 12 Mar 2020 12:44:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3A8C206FA for ; Thu, 12 Mar 2020 12:44:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="g0kKRPt5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727266AbgCLMon (ORCPT ); Thu, 12 Mar 2020 08:44:43 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:57163 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727193AbgCLMok (ORCPT ); Thu, 12 Mar 2020 08:44:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584017079; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=NDC/aDJLXgt4BSQCv1kgy9uzztvACIYJCoAY3Dz157U=; b=g0kKRPt5OclIlH12SVAWuDFaUqctOWEs7pCwA9nwqbYTPwt1f3xkKSVjrlvS5yJr6u+pVj /xGECBL8usL4z9l5Wm69D1L4jd7SWXI8xSpa8piFa7RH6RgKnFxIWrPDvRQN7++APWa+vj 0Px3mcm01MIq8TD8/57ANAtyOvCBq+g= 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-5-N2kBufpfPLuoAUuVKNAdGw-1; Thu, 12 Mar 2020 08:44:37 -0400 X-MC-Unique: N2kBufpfPLuoAUuVKNAdGw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 686EB8018B2; Thu, 12 Mar 2020 12:44:36 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-43.pek2.redhat.com [10.72.12.43]) by smtp.corp.redhat.com (Postfix) with ESMTP id 975768FBEF; Thu, 12 Mar 2020 12:44:33 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.com, david@redhat.com, richard.weiyang@gmail.com, dan.j.williams@intel.com, bhe@redhat.com Subject: [PATCH v4 4/5] mm/sparse.c: add note about only VMEMMAP supporting sub-section hotplug Date: Thu, 12 Mar 2020 20:44:13 +0800 Message-Id: <20200312124414.439-5-bhe@redhat.com> In-Reply-To: <20200312124414.439-1-bhe@redhat.com> References: <20200312124414.439-1-bhe@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org And tell check_pfn_span() gating the porper alignment and size of hot added memory region. And also move the code comments from inside section_deactivate() to being above it. The code comments are reasonable for the whole function, and the moving makes code cleaner. Signed-off-by: Baoquan He Acked-by: Michal Hocko --- mm/sparse.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) diff --git a/mm/sparse.c b/mm/sparse.c index 117fe4554c38..f02a524e17d1 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -771,6 +771,22 @@ static bool is_subsection_map_empty(struct mem_section *ms) } #endif +/* + * To deactivate a memory region, there are 3 cases to handle across + * two configurations (SPARSEMEM_VMEMMAP={y,n}): + * + * 1. deactivation of a partial hot-added section (only possible in + * the SPARSEMEM_VMEMMAP=y case). + * a) section was present at memory init. + * b) section was hot-added post memory init. + * 2. deactivation of a complete hot-added section. + * 3. deactivation of a complete section from memory init. + * + * For 1, when subsection_map does not empty we will not be freeing the + * usage map, but still need to free the vmemmap range. + * + * For 2 and 3, the SPARSEMEM_VMEMMAP={y,n} cases are unified + */ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, struct vmem_altmap *altmap) { @@ -781,23 +797,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, if (clear_subsection_map(pfn, nr_pages)) return; - /* - * There are 3 cases to handle across two configurations - * (SPARSEMEM_VMEMMAP={y,n}): - * - * 1/ deactivation of a partial hot-added section (only possible - * in the SPARSEMEM_VMEMMAP=y case). - * a/ section was present at memory init - * b/ section was hot-added post memory init - * 2/ deactivation of a complete hot-added section - * 3/ deactivation of a complete section from memory init - * - * For 1/, when subsection_map does not empty we will not be - * freeing the usage map, but still need to free the vmemmap - * range. - * - * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified - */ + empty = is_subsection_map_empty(ms); if (empty) { unsigned long section_nr = pfn_to_section_nr(pfn); @@ -905,6 +905,10 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, * * This is only intended for hotplug. * + * Note that only VMEMMAP supports sub-section aligned hotplug, + * the proper alignment and size are gated by check_pfn_span(). + * + * * Return: * * 0 - On success. * * -EEXIST - Section has been present. -- 2.17.2