From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx149.postini.com [74.125.245.149]) by kanga.kvack.org (Postfix) with SMTP id 11A326B0074 for ; Tue, 4 Dec 2012 04:23:01 -0500 (EST) Message-ID: <50BDC0B9.50007@cn.fujitsu.com> Date: Tue, 04 Dec 2012 17:22:01 +0800 From: Tang Chen MIME-Version: 1.0 Subject: Re: [Patch v4 02/12] memory-hotplug: check whether all memory blocks are offlined or not when removing memory References: <1354010422-19648-1-git-send-email-wency@cn.fujitsu.com> <1354010422-19648-3-git-send-email-wency@cn.fujitsu.com> In-Reply-To: <1354010422-19648-3-git-send-email-wency@cn.fujitsu.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: owner-linux-mm@kvack.org List-ID: To: Wen Congyang Cc: 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 , Yasuaki Ishimatsu , Jianguo Wu On 11/27/2012 06:00 PM, Wen Congyang wrote: > From: Yasuaki Ishimatsu > > We remove the memory like this: > 1. lock memory hotplug > 2. offline a memory block > 3. unlock memory hotplug > 4. repeat 1-3 to offline all memory blocks > 5. lock memory hotplug > 6. remove memory(TODO) > 7. unlock memory hotplug > > All memory blocks must be offlined before removing memory. But we don't hold > the lock in the whole operation. So we should check whether all memory blocks > are offlined before step6. Otherwise, kernel maybe panicked. > > CC: David Rientjes > CC: Jiang Liu > CC: Len Brown > CC: Christoph Lameter > Cc: Minchan Kim > CC: Andrew Morton > CC: KOSAKI Motohiro > Signed-off-by: Wen Congyang > Signed-off-by: Yasuaki Ishimatsu Reviewed-by: Tang Chen > --- > drivers/base/memory.c | 6 ++++++ > include/linux/memory_hotplug.h | 1 + > mm/memory_hotplug.c | 47 ++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 86c8821..badb025 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -675,6 +675,12 @@ int offline_memory_block(struct memory_block *mem) > return ret; > } > > +/* return true if the memory block is offlined, otherwise, return false */ > +bool is_memblock_offlined(struct memory_block *mem) > +{ > + return mem->state == MEM_OFFLINE; > +} > + > /* > * Initialize the sysfs support for memory devices... > */ > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index 95573ec..38675e9 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -236,6 +236,7 @@ extern int add_memory(int nid, u64 start, u64 size); > extern int arch_add_memory(int nid, u64 start, u64 size); > extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages); > extern int offline_memory_block(struct memory_block *mem); > +extern bool is_memblock_offlined(struct memory_block *mem); > extern int remove_memory(u64 start, u64 size); > extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn, > int nr_pages); > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index b825dbc..b6d1101 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1054,6 +1054,53 @@ repeat: > goto repeat; > } > > + lock_memory_hotplug(); > + > + /* > + * we have offlined all memory blocks like this: > + * 1. lock memory hotplug > + * 2. offline a memory block > + * 3. unlock memory hotplug > + * > + * repeat step1-3 to offline the memory block. All memory blocks > + * must be offlined before removing memory. But we don't hold the > + * lock in the whole operation. So we should check whether all > + * memory blocks are offlined. > + */ > + > + for (pfn = start_pfn; pfn< end_pfn; pfn += PAGES_PER_SECTION) { > + section_nr = pfn_to_section_nr(pfn); > + if (!present_section_nr(section_nr)) > + continue; > + > + section = __nr_to_section(section_nr); > + /* same memblock? */ > + if (mem) > + if ((section_nr>= mem->start_section_nr)&& > + (section_nr<= mem->end_section_nr)) > + continue; > + > + mem = find_memory_block_hinted(section, mem); > + if (!mem) > + continue; > + > + ret = is_memblock_offlined(mem); > + if (!ret) { > + pr_warn("removing memory fails, because memory " > + "[%#010llx-%#010llx] is onlined\n", > + PFN_PHYS(section_nr_to_pfn(mem->start_section_nr)), > + PFN_PHYS(section_nr_to_pfn(mem->end_section_nr + 1)) - 1); > + > + kobject_put(&mem->dev.kobj); > + unlock_memory_hotplug(); > + return ret; > + } > + } > + > + if (mem) > + kobject_put(&mem->dev.kobj); > + unlock_memory_hotplug(); > + > return 0; > } > #else -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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