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    SubjectRe: [PATCH v4 3/13] memory-hotplug : check whether memory is present or not
    Hi Wen,

    2012/07/18 19:25, Wen Congyang wrote:
    > At 07/18/2012 06:07 PM, Yasuaki Ishimatsu Wrote:
    >> If system supports memory hot-remove, online_pages() may online removed pages.
    >> So online_pages() need to check whether onlining pages are present or not.
    >>
    >> 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: Wen Congyang <wency@cn.fujitsu.com>
    >> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    >>
    >> ---
    >> include/linux/mmzone.h | 21 +++++++++++++++++++++
    >> mm/memory_hotplug.c | 13 +++++++++++++
    >> 2 files changed, 34 insertions(+)
    >>
    >> Index: linux-3.5-rc6/include/linux/mmzone.h
    >> ===================================================================
    >> --- linux-3.5-rc6.orig/include/linux/mmzone.h 2012-07-08 09:23:56.000000000 +0900
    >> +++ linux-3.5-rc6/include/linux/mmzone.h 2012-07-17 16:10:21.588186145 +0900
    >> @@ -1168,6 +1168,27 @@ void sparse_init(void);
    >> #define sparse_index_init(_sec, _nid) do {} while (0)
    >> #endif /* CONFIG_SPARSEMEM */
    >>
    >> +#ifdef CONFIG_SPARSEMEM
    >> +static inline int pfns_present(unsigned long pfn, unsigned long nr_pages)
    >> +{
    >> + int i;
    >> + for (i = 0; i < nr_pages; i++) {
    >> + if (pfn_present(pfn + 1))
    >> + continue;
    >> + else {
    >> + unlock_memory_hotplug();
    >
    > Why do you unlock memory hotplug here? The caller will do it.

    Ah, you are right. In this case, the function should only return -EINVAL.

    Thansks,
    Yasuaki Ishimatsu
    >
    > Thanks
    > Wen Congyang
    >
    >> + return -EINVAL;
    >> + }
    >> + }
    >> + return 0;
    >> +}
    >> +#else
    >> +static inline int pfns_present(unsigned long pfn, unsigned long nr_pages)
    >> +{
    >> + return 0;
    >> +}
    >> +#endif /* CONFIG_SPARSEMEM*/
    >> +
    >> #ifdef CONFIG_NODES_SPAN_OTHER_NODES
    >> bool early_pfn_in_nid(unsigned long pfn, int nid);
    >> #else
    >> Index: linux-3.5-rc6/mm/memory_hotplug.c
    >> ===================================================================
    >> --- linux-3.5-rc6.orig/mm/memory_hotplug.c 2012-07-17 14:26:40.000000000 +0900
    >> +++ linux-3.5-rc6/mm/memory_hotplug.c 2012-07-17 16:09:50.070580170 +0900
    >> @@ -467,6 +467,19 @@ int __ref online_pages(unsigned long pfn
    >> struct memory_notify arg;
    >>
    >> lock_memory_hotplug();
    >> + /*
    >> + * If system supports memory hot-remove, the memory may have been
    >> + * removed. So we check whether the memory has been removed or not.
    >> + *
    >> + * Note: When CONFIG_SPARSEMEM is defined, pfns_present() become
    >> + * effective. If CONFIG_SPARSEMEM is not defined, pfns_present()
    >> + * always returns 0.
    >> + */
    >> + ret = pfns_present(pfn, nr_pages);
    >> + if (ret) {
    >> + unlock_memory_hotplug();
    >> + return ret;
    >> + }
    >> arg.start_pfn = pfn;
    >> arg.nr_pages = nr_pages;
    >> arg.status_change_nid = -1;
    >>
    >>
    >





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