From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wen Congyang Date: Tue, 20 Nov 2012 09:37:49 +0000 Subject: Re: [PATCH v3 06/12] memory-hotplug: unregister memory section on SPARSEMEM_VMEMMAP Message-Id: <50AB4F6D.3050002@cn.fujitsu.com> List-Id: References: <1351763083-7905-1-git-send-email-wency@cn.fujitsu.com> <1351763083-7905-7-git-send-email-wency@cn.fujitsu.com> <50AB21A4.8050709@gmail.com> <50AB2967.5010302@cn.fujitsu.com> <50AB2A1A.6040606@gmail.com> In-Reply-To: <50AB2A1A.6040606@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 At 11/20/2012 02:58 PM, Jaegeuk Hanse Wrote: > On 11/20/2012 02:55 PM, Wen Congyang wrote: >> At 11/20/2012 02:22 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, >>> >>> In order to review this patch, I should dig sparse memory codes in >>> advance. But I have some confuse of codes. Why need encode/decode mem >>> map instead of set mem_map to ms->section_mem_map directly? >> The memmap is aligned, and the low bits are zero. We store some >> information >> in these bits. So we need to encode/decode memmap here. > > Hi Congyang, > > Thanks for you reponse. But I mean why return (unsigned long)(mem_map - > (section_nr_to_pfn(pnum))); in function sparse_encode_mem_map, and then > return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum); in > funtion sparse_decode_mem_map instead of just store mem_map in > ms->section_mep_map directly. I don't know why. I try to find the reason, but I don't find any place to use the pfn stored in the mem_map except in the decode function. Maybe the designer doesn't want us to access the mem_map directly. Thanks Wen Congyang > > Regards, > Jaegeuk > >> >> 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) >>> > >