From 50265ae8e68ea1ab13b6d2d4aa3a347cc10febc5 Mon Sep 17 00:00:00 2001 From: Yasuaki Ishimatsu Date: Wed, 20 Feb 2013 13:14:10 +1100 Subject: [PATCH] memory-hotplug: check whether all memory blocks are offlined or not when removing memory 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. Offlining a memory block and removing a memory device can be two different operations. Users can just offline some memory blocks without removing the memory device. For this purpose, the kernel has held lock_memory_hotplug() in __offline_pages(). To reuse the code for memory hot-remove, we repeat step 1-3 to offline all the memory blocks, repeatedly lock and unlock memory hotplug, but not hold the memory hotplug lock in the whole operation. Signed-off-by: Wen Congyang Signed-off-by: Yasuaki Ishimatsu Signed-off-by: Tang Chen Acked-by: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro Cc: Jiang Liu Cc: Jianguo Wu Cc: Kamezawa Hiroyuki Cc: Lai Jiangshan Cc: Wu Jianguo Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Signed-off-by: Andrew Morton --- drivers/base/memory.c | 6 +++++ include/linux/memory_hotplug.h | 1 + mm/memory_hotplug.c | 48 ++++++++++++++++++++++++++++++++++ 3 files changed, 55 insertions(+) diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 83d0b17ba1c2..a51007b79032 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 4a45c4e50025..8dd0950a6a7a 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 6a82972aeae5..5d350f5c68e5 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1429,6 +1429,54 @@ 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. + */ + + mem = NULL; + 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 -- 2.39.5