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    Subject[RFC v8 PATCH 02/20] memory-hotplug: implement offline_memory()
    Date
    From: Wen Congyang <wency@cn.fujitsu.com>

    The function offline_memory() will be called when hot removing a
    memory device. The memory device may contain more than one memory
    block. If the memory block has been offlined, __offline_pages()
    will fail. So we should try to offline one memory block at a
    time.

    If the memory block is offlined in offline_memory(), we also
    update it's state, and notify the userspace that its state is
    changed.

    The function offline_memory() also check each memory block's
    state. So there is no need to check the memory block's state
    before calling offline_memory().

    CC: David Rientjes <rientjes@google.com>
    CC: Jiang Liu <liuj97@gmail.com>
    CC: Len Brown <len.brown@intel.com>
    CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    CC: Paul Mackerras <paulus@samba.org>
    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>
    CC: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
    Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
    ---
    drivers/base/memory.c | 31 +++++++++++++++++++++++++++----
    include/linux/memory_hotplug.h | 2 ++
    mm/memory_hotplug.c | 37 ++++++++++++++++++++++++++++++++++++-
    3 files changed, 65 insertions(+), 5 deletions(-)

    diff --git a/drivers/base/memory.c b/drivers/base/memory.c
    index 44e7de6..86c8821 100644
    --- a/drivers/base/memory.c
    +++ b/drivers/base/memory.c
    @@ -275,13 +275,11 @@ memory_block_action(unsigned long phys_index, unsigned long action)
    return ret;
    }

    -static int memory_block_change_state(struct memory_block *mem,
    +static int __memory_block_change_state(struct memory_block *mem,
    unsigned long to_state, unsigned long from_state_req)
    {
    int ret = 0;

    - mutex_lock(&mem->state_mutex);
    -
    if (mem->state != from_state_req) {
    ret = -EINVAL;
    goto out;
    @@ -309,10 +307,20 @@ static int memory_block_change_state(struct memory_block *mem,
    break;
    }
    out:
    - mutex_unlock(&mem->state_mutex);
    return ret;
    }

    +static int memory_block_change_state(struct memory_block *mem,
    + unsigned long to_state, unsigned long from_state_req)
    +{
    + int ret;
    +
    + mutex_lock(&mem->state_mutex);
    + ret = __memory_block_change_state(mem, to_state, from_state_req);
    + mutex_unlock(&mem->state_mutex);
    +
    + return ret;
    +}
    static ssize_t
    store_mem_state(struct device *dev,
    struct device_attribute *attr, const char *buf, size_t count)
    @@ -653,6 +661,21 @@ int unregister_memory_section(struct mem_section *section)
    }

    /*
    + * offline one memory block. If the memory block has been offlined, do nothing.
    + */
    +int offline_memory_block(struct memory_block *mem)
    +{
    + int ret = 0;
    +
    + mutex_lock(&mem->state_mutex);
    + if (mem->state != MEM_OFFLINE)
    + ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
    + mutex_unlock(&mem->state_mutex);
    +
    + return ret;
    +}
    +
    +/*
    * Initialize the sysfs support for memory devices...
    */
    int __init memory_dev_init(void)
    diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
    index c183f39..0b040bb 100644
    --- a/include/linux/memory_hotplug.h
    +++ b/include/linux/memory_hotplug.h
    @@ -10,6 +10,7 @@ struct page;
    struct zone;
    struct pglist_data;
    struct mem_section;
    +struct memory_block;

    #ifdef CONFIG_MEMORY_HOTPLUG

    @@ -234,6 +235,7 @@ extern int mem_online_node(int nid);
    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 int offline_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 c182c76..3113cd4 100644
    --- a/mm/memory_hotplug.c
    +++ b/mm/memory_hotplug.c
    @@ -1001,7 +1001,42 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)

    int offline_memory(u64 start, u64 size)
    {
    - return -EINVAL;
    + struct memory_block *mem = NULL;
    + struct mem_section *section;
    + unsigned long start_pfn, end_pfn;
    + unsigned long pfn, section_nr;
    + int ret;
    +
    + start_pfn = PFN_DOWN(start);
    + end_pfn = start_pfn + PFN_DOWN(size);
    +
    + 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 = offline_memory_block(mem);
    + if (ret) {
    + kobject_put(&mem->dev.kobj);
    + return ret;
    + }
    + }
    +
    + if (mem)
    + kobject_put(&mem->dev.kobj);
    +
    + return 0;
    }
    #else
    int offline_pages(u64 start, u64 size)
    --
    1.7.1


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