On 09/11/2012 10:24 AM, Yasuaki Ishimatsu wrote:
Hi Wen,
2012/09/11 11:15, Wen Congyang wrote:
Hi, ishimatsu
At 09/05/2012 05:25 PM, wency@xxxxxxxxxxxxxx Wrote:
From: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
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.
Because we use memory_block_change_state() to hotremoving memory, I
think
this patch can be removed. What do you think?
Pleae teach me detals a little more. If we use
memory_block_change_state(),
does the conflict never occur? Why?
since memory hot-add or hot-remove is based on memblock, if check in
memory_block_change_state()
can guarantee conflict never occur?
Thansk,
Yasuaki Ishimatsu
Thanks
Wen Congyang
CC: David Rientjes <rientjes@xxxxxxxxxx>
CC: Jiang Liu <liuj97@xxxxxxxxx>
CC: Len Brown <len.brown@xxxxxxxxx>
CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
CC: Paul Mackerras <paulus@xxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: Wen Congyang <wency@xxxxxxxxxxxxxx>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 19 +++++++++++++++++++
mm/memory_hotplug.c | 13 +++++++++++++
2 files changed, 32 insertions(+), 0 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 2daa54f..ac3ae30 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1180,6 +1180,25 @@ 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 + i))
+ continue;
+ else
+ 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
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 49f7747..299747d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -467,6 +467,19 @@ int __ref online_pages(unsigned long pfn,
unsigned long nr_pages)
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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