memory-hotplug: check whether all memory blocks are offlined or not when removing memory (6677e3ea) · Commits · 戴 / test

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 <wency@cn.fujitsu.com> Signed-off-by:

Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Signed-off-by:

Tang Chen <tangchen@cn.fujitsu.com> Acked-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Jiang Liu <jiang.liu@huawei.com> Cc: Jianguo Wu <wujianguo@huawei.com> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Wu Jianguo <wujianguo@huawei.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/memory.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -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...
		*/

include/linux/memory_hotplug.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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);

mm/memory_hotplug.c

+48 −0

Original line number	Diff line number	Diff line
		@@ -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

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