From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754207Ab2KUC7Z (ORCPT ); Tue, 20 Nov 2012 21:59:25 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:8124 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752505Ab2KUC7X (ORCPT ); Tue, 20 Nov 2012 21:59:23 -0500 X-IronPort-AV: E=Sophos;i="4.83,290,1352044800"; d="scan'208";a="6242998" Message-ID: <50AC4505.1000007@cn.fujitsu.com> Date: Wed, 21 Nov 2012 11:05:41 +0800 From: Wen Congyang User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100413 Fedora/3.0.4-2.fc13 Thunderbird/3.0.4 MIME-Version: 1.0 To: Jaegeuk Hanse CC: Yasuaki Ishimatsu , x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-ia64@vger.kernel.org, cmetcalf@tilera.com, sparclinux@vger.kernel.org, David Rientjes , Jiang Liu , Len Brown , benh@kernel.crashing.org, paulus@samba.org, Christoph Lameter , Minchan Kim , Andrew Morton , KOSAKI Motohiro , Jianguo Wu Subject: Re: [PATCH v3 06/12] memory-hotplug: unregister memory section on SPARSEMEM_VMEMMAP References: <1351763083-7905-1-git-send-email-wency@cn.fujitsu.com> <1351763083-7905-7-git-send-email-wency@cn.fujitsu.com> <50AB669D.3060007@gmail.com> In-Reply-To: <50AB669D.3060007@gmail.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/11/21 10:59:03, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/11/21 10:59:04, Serialize complete at 2012/11/21 10:59:04 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At 11/20/2012 07:16 PM, Jaegeuk Hanse Wrote: > On 11/01/2012 05:44 PM, Wen Congyang wrote: >> From: Yasuaki Ishimatsu >> >> Currently __remove_section for SPARSEMEM_VMEMMAP does nothing. But >> even if >> we use SPARSEMEM_VMEMMAP, we can unregister the memory_section. >> >> So the patch add unregister_memory_section() into __remove_section(). > > Hi Yasuaki, > > I have a question about these sparse vmemmap memory related patches. Hot > add memory need allocated vmemmap pages, but this time is allocated by > buddy system. How can gurantee virtual address is continuous to the > address allocated before? If not continuous, page_to_pfn and pfn_to_page > can't work correctly. vmemmap has its virtual address range: ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB) We allocate memory from buddy system to store struct page, and its virtual address isn't in this range. So we should update the page table: kmalloc_section_memmap() sparse_mem_map_populate() pfn_to_page() // get the virtual address in the vmemmap range vmemmap_populate() // we update page table here When we use vmemmap, page_to_pfn() always returns address in the vmemmap range, not the address that kmalloc() returns. So the virtual address is continuous. Thanks Wen Congyang > > Regards, > Jaegeuk > >> >> CC: David Rientjes >> CC: Jiang Liu >> CC: Len Brown >> CC: Christoph Lameter >> Cc: Minchan Kim >> CC: Andrew Morton >> CC: KOSAKI Motohiro >> CC: Wen Congyang >> Signed-off-by: Yasuaki Ishimatsu >> --- >> mm/memory_hotplug.c | 13 ++++++++----- >> 1 file changed, 8 insertions(+), 5 deletions(-) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index ca07433..66a79a7 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -286,11 +286,14 @@ static int __meminit __add_section(int nid, >> struct zone *zone, >> #ifdef CONFIG_SPARSEMEM_VMEMMAP >> static int __remove_section(struct zone *zone, struct mem_section *ms) >> { >> - /* >> - * XXX: Freeing memmap with vmemmap is not implement yet. >> - * This should be removed later. >> - */ >> - return -EBUSY; >> + int ret = -EINVAL; >> + >> + if (!valid_section(ms)) >> + return ret; >> + >> + ret = unregister_memory_section(ms); >> + >> + return ret; >> } >> #else >> static int __remove_section(struct zone *zone, struct mem_section *ms) > >