memory-hotplug, mm/sparse.c: clear the memory to store struct page

If sparse memory vmemmap is enabled, we can't free the memory to store
struct page when a memory device is hotremoved, because we may store
struct page in the memory to manage the memory which doesn't belong to
this memory device.  When we hotadded this memory device again, we will
reuse this memory to store struct page, and struct page may contain some
obsolete information, and we will get bad-page state:

[   59.611278] init_memory_mapping: [mem 0x80000000-0x9fffffff]
[   59.637836] Built 2 zonelists in Node order, mobility grouping on.  Total pages: 547617
[   59.638739] Policy zone: Normal
[   59.650840] BUG: Bad page state in process bash  pfn:9b6dc
[   59.651124] page:ffffea0002200020 count:0 mapcount:0 mapping:          (null) index:0xfdfdfdfdfdfdfdfd
[   59.651494] page flags: 0x2fdfdfdfd5df9fd(locked|referenced|uptodate|dirty|lru|active|slab|owner_priv_1|private|private_2|writeback|head|tail|swapcache|reclaim|swapbacked|unevictable|uncached|compound_lock)
[   59.653604] Modules linked in: netconsole acpiphp pci_hotplug acpi_memhotplug loop kvm_amd kvm microcode tpm_tis tpm tpm_bios evdev psmouse serio_raw i2c_piix4 i2c_core parport_pc parport processor button thermal_sys ext3 jbd mbcache sg sr_mod cdrom ata_generic virtio_net ata_piix virtio_blk libata virtio_pci virtio_ring virtio scsi_mod
[   59.656998] Pid: 988, comm: bash Not tainted 3.6.0-rc7-guest #12
[   59.657172] Call Trace:
[   59.657275]  [<ffffffff810e9b30>] ? bad_page+0xb0/0x100
[   59.657434]  [<ffffffff810ea4c3>] ? free_pages_prepare+0xb3/0x100
[   59.657610]  [<ffffffff810ea668>] ? free_hot_cold_page+0x48/0x1a0
[   59.657787]  [<ffffffff8112cc08>] ? online_pages_range+0x68/0xa0
[   59.657961]  [<ffffffff8112cba0>] ? __online_page_increment_counters+0x10/0x10
[   59.658162]  [<ffffffff81045561>] ? walk_system_ram_range+0x101/0x110
[   59.658346]  [<ffffffff814c4f95>] ? online_pages+0x1a5/0x2b0
[   59.658515]  [<ffffffff8135663d>] ? __memory_block_change_state+0x20d/0x270
[   59.658710]  [<ffffffff81356756>] ? store_mem_state+0xb6/0xf0
[   59.658878]  [<ffffffff8119e482>] ? sysfs_write_file+0xd2/0x160
[   59.659052]  [<ffffffff8113769a>] ? vfs_write+0xaa/0x160
[   59.659212]  [<ffffffff81137977>] ? sys_write+0x47/0x90
[   59.659371]  [<ffffffff814e2f25>] ? async_page_fault+0x25/0x30
[   59.659543]  [<ffffffff814ea239>] ? system_call_fastpath+0x16/0x1b
[   59.659720] Disabling lock debugging due to kernel taint

This patch clears the memory to store struct page to avoid unexpected error.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Reported-by: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/sparse.c b/mm/sparse.c
index 8152952e50141509aa96648a7fdfa10743086150..b2d37c6071029b4d0002013e0c7aca5fcc79b1e0 100644 (file)
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -638,7 +638,6 @@ static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
 got_map_page:
        ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
 got_map_ptr:
-       memset(ret, 0, memmap_size);
 
        return ret;
 }
@@ -760,6 +759,8 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
                goto out;
        }
 
+       memset(memmap, 0, sizeof(struct page) * nr_pages);
+
        ms->section_mem_map |= SECTION_MARKED_PRESENT;
 
        ret = sparse_init_one_section(ms, section_nr, memmap, usemap);