From 35dca71c1fad13616d9ea336c05730071793b63a Mon Sep 17 00:00:00 2001 From: Yasuaki Ishimatsu Date: Wed, 29 Oct 2014 14:50:40 -0700 Subject: [PATCH] memory-hotplug: clear pgdat which is allocated by bootmem in try_offline_node() When hot adding the same memory after hot removal, the following messages are shown: WARNING: CPU: 20 PID: 6 at mm/page_alloc.c:4968 free_area_init_node+0x3fe/0x426() ... Call Trace: dump_stack+0x46/0x58 warn_slowpath_common+0x81/0xa0 warn_slowpath_null+0x1a/0x20 free_area_init_node+0x3fe/0x426 hotadd_new_pgdat+0x90/0x110 add_memory+0xd4/0x200 acpi_memory_device_add+0x1aa/0x289 acpi_bus_attach+0xfd/0x204 acpi_bus_attach+0x178/0x204 acpi_bus_scan+0x6a/0x90 acpi_device_hotplug+0xe8/0x418 acpi_hotplug_work_fn+0x1f/0x2b process_one_work+0x14e/0x3f0 worker_thread+0x11b/0x510 kthread+0xe1/0x100 ret_from_fork+0x7c/0xb0 The detaled explanation is as follows: When hot removing memory, pgdat is set to 0 in try_offline_node(). But if the pgdat is allocated by bootmem allocator, the clearing step is skipped. And when hot adding the same memory, the uninitialized pgdat is reused. But free_area_init_node() checks wether pgdat is set to zero. As a result, free_area_init_node() hits WARN_ON(). This patch clears pgdat which is allocated by bootmem allocator in try_offline_node(). Signed-off-by: Yasuaki Ishimatsu Cc: Zhang Zhen Cc: Wang Nan Cc: Tang Chen Reviewed-by: Toshi Kani Cc: Dave Hansen Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 29d8693d0c61..252e1dbbed86 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1912,7 +1912,6 @@ void try_offline_node(int nid) unsigned long start_pfn = pgdat->node_start_pfn; unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages; unsigned long pfn; - struct page *pgdat_page = virt_to_page(pgdat); int i; for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) { @@ -1941,10 +1940,6 @@ void try_offline_node(int nid) node_set_offline(nid); unregister_one_node(nid); - if (!PageSlab(pgdat_page) && !PageCompound(pgdat_page)) - /* node data is allocated from boot memory */ - return; - /* free waittable in each zone */ for (i = 0; i < MAX_NR_ZONES; i++) { struct zone *zone = pgdat->node_zones + i; -- 2.20.1