From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kamezawa Hiroyuki Date: Wed, 26 Dec 2012 03:10:43 +0000 Subject: Re: [PATCH v5 02/14] memory-hotplug: check whether all memory blocks are offlined or not when removi Message-Id: <50DA6AB3.2030608@jp.fujitsu.com> List-Id: References: <1356350964-13437-1-git-send-email-tangchen@cn.fujitsu.com> <1356350964-13437-3-git-send-email-tangchen@cn.fujitsu.com> In-Reply-To: <1356350964-13437-3-git-send-email-tangchen@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tang Chen Cc: akpm@linux-foundation.org, rientjes@google.com, liuj97@gmail.com, len.brown@intel.com, benh@kernel.crashing.org, paulus@samba.org, cl@linux.com, minchan.kim@gmail.com, kosaki.motohiro@jp.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, wujianguo@huawei.com, wency@cn.fujitsu.com, hpa@zytor.com, linfeng@cn.fujitsu.com, laijs@cn.fujitsu.com, mgorman@suse.de, yinghai@kernel.org, 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 (2012/12/24 21:09), Tang Chen 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. > > Signed-off-by: Wen Congyang > Signed-off-by: Yasuaki Ishimatsu Acked-by: KAMEZAWA Hiroyuki a nitpick below. > --- > drivers/base/memory.c | 6 +++++ > include/linux/memory_hotplug.h | 1 + > mm/memory_hotplug.c | 47 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 54 insertions(+), 0 deletions(-) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 987604d..8300a18 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -693,6 +693,12 @@ 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 4a45c4e..8dd0950 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -247,6 +247,7 @@ 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 62e04c9..d43d97b 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1430,6 +1430,53 @@ 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) { I prefer adding mem = NULL at the start of this for(). > + 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; > + Thanks, -Kame