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    Subject[PATCH 10/10] memory-hotplug : remove sysfs file of node
    From: Wen Congyang <wency@cn.fujitsu.com>

    This patch introduces a new function try_offline_node() to
    remove sysfs file of node when all memory sections of this
    node are removed. If some memory sections of this node are
    not removed, this function does nothing.

    CC: David Rientjes <rientjes@google.com>
    CC: Jiang Liu <liuj97@gmail.com>
    CC: Len Brown <len.brown@intel.com>
    CC: Christoph Lameter <cl@linux.com>
    Cc: Minchan Kim <minchan.kim@gmail.com>
    CC: Andrew Morton <akpm@linux-foundation.org>
    CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    CC: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
    ---
    mm/memory_hotplug.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
    1 file changed, 54 insertions(+)

    Index: linux-3.6/mm/memory_hotplug.c
    ===================================================================
    --- linux-3.6.orig/mm/memory_hotplug.c 2012-10-04 18:30:31.767709165 +0900
    +++ linux-3.6/mm/memory_hotplug.c 2012-10-04 18:32:46.907842637 +0900
    @@ -29,6 +29,7 @@
    #include <linux/suspend.h>
    #include <linux/mm_inline.h>
    #include <linux/firmware-map.h>
    +#include <linux/stop_machine.h>

    #include <asm/tlbflush.h>

    @@ -1276,6 +1277,57 @@ int offline_memory(u64 start, u64 size)
    return 0;
    }

    +static int check_cpu_on_node(void *data)
    +{
    + struct pglist_data *pgdat = data;
    + int cpu;
    +
    + for_each_online_cpu(cpu) {
    + if (cpu_to_node(cpu) == pgdat->node_id)
    + /*
    + * the cpu on this node is onlined, and we can't
    + * offline this node.
    + */
    + return -EBUSY;
    + }
    +
    + return 0;
    +}
    +
    +/* offline the node if all memory sections of this node are removed */
    +static void try_offline_node(int nid)
    +{
    + unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
    + unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
    + unsigned long pfn;
    +
    + for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
    + unsigned long section_nr = pfn_to_section_nr(pfn);
    +
    + if (!present_section_nr(section_nr))
    + continue;
    +
    + if (pfn_to_nid(pfn) != nid)
    + continue;
    +
    + /*
    + * some memory sections of this node are not removed, and we
    + * can't offline node now.
    + */
    + return;
    + }
    +
    + if (stop_machine(check_cpu_on_node, NODE_DATA(nid), NULL))
    + return;
    +
    + /*
    + * all memory sections of this node are removed, we can offline this
    + * node now.
    + */
    + node_set_offline(nid);
    + unregister_one_node(nid);
    +}
    +
    int __ref remove_memory(int nid, u64 start, u64 size)
    {
    int ret = 0;
    @@ -1296,6 +1348,8 @@ int __ref remove_memory(int nid, u64 sta
    firmware_map_remove(start, start + size, "System RAM");

    arch_remove_memory(start, size);
    +
    + try_offline_node(nid);
    out:
    unlock_memory_hotplug();
    return ret;


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