From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from song.cn.fujitsu.com (unknown [222.73.24.84]) by ozlabs.org (Postfix) with ESMTP id 57F0C2C0098 for ; Tue, 4 Dec 2012 20:18:30 +1100 (EST) Message-ID: <50BDBFAA.7040008@cn.fujitsu.com> Date: Tue, 04 Dec 2012 17:17:30 +0800 From: Tang Chen MIME-Version: 1.0 To: Wen Congyang Subject: Re: [Patch v4 01/12] memory-hotplug: try to offline the memory twice to avoid dependence References: <1354010422-19648-1-git-send-email-wency@cn.fujitsu.com> <1354010422-19648-2-git-send-email-wency@cn.fujitsu.com> In-Reply-To: <1354010422-19648-2-git-send-email-wency@cn.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org, Len Brown , linux-acpi@vger.kernel.org, linux-sh@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, cmetcalf@tilera.com, Jianguo Wu , linux-mm@kvack.org, Yasuaki Ishimatsu , paulus@samba.org, Minchan Kim , KOSAKI Motohiro , David Rientjes , sparclinux@vger.kernel.org, Christoph Lameter , linuxppc-dev@lists.ozlabs.org, Andrew Morton , Jiang Liu List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 11/27/2012 06:00 PM, Wen Congyang wrote: > memory can't be offlined when CONFIG_MEMCG is selected. > For example: there is a memory device on node 1. The address range > is [1G, 1.5G). You will find 4 new directories memory8, memory9, memory10, > and memory11 under the directory /sys/devices/system/memory/. > > If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup > when we online pages. When we online memory8, the memory stored page cgroup > is not provided by this memory device. But when we online memory9, the memory > stored page cgroup may be provided by memory8. So we can't offline memory8 > now. We should offline the memory in the reversed order. > > When the memory device is hotremoved, we will auto offline memory provided > by this memory device. But we don't know which memory is onlined first, so > offlining memory may fail. In such case, iterate twice to offline the memory. > 1st iterate: offline every non primary memory block. > 2nd iterate: offline primary (i.e. first added) memory block. > > This idea is suggested by KOSAKI Motohiro. > > CC: David Rientjes > CC: Jiang Liu > CC: Len Brown > CC: Christoph Lameter > Cc: Minchan Kim > CC: Andrew Morton > CC: KOSAKI Motohiro > CC: Yasuaki Ishimatsu > Signed-off-by: Wen Congyang Reviewed-by: Tang Chen > --- > mm/memory_hotplug.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index e4eeaca..b825dbc 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1012,10 +1012,13 @@ int remove_memory(u64 start, u64 size) > unsigned long start_pfn, end_pfn; > unsigned long pfn, section_nr; > int ret; > + int return_on_error = 0; > + int retry = 0; > > start_pfn = PFN_DOWN(start); > end_pfn = start_pfn + PFN_DOWN(size); > > +repeat: > for (pfn = start_pfn; pfn< end_pfn; pfn += PAGES_PER_SECTION) { > section_nr = pfn_to_section_nr(pfn); > if (!present_section_nr(section_nr)) > @@ -1034,14 +1037,23 @@ int remove_memory(u64 start, u64 size) > > ret = offline_memory_block(mem); > if (ret) { > - kobject_put(&mem->dev.kobj); > - return ret; > + if (return_on_error) { > + kobject_put(&mem->dev.kobj); > + return ret; > + } else { > + retry = 1; > + } > } > } > > if (mem) > kobject_put(&mem->dev.kobj); > > + if (retry) { > + return_on_error = 1; > + goto repeat; > + } > + > return 0; > } > #else