Re: [Patch v4 05/12] memory-hotplug: introduce new function arch_remove_memory() for removing page table depends on architecture

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On 11/27/2012 06:00 PM, Wen Congyang wrote:
For removing memory, we need to remove page table. But it depends
on architecture. So the patch introduce arch_remove_memory() for
removing page table. Now it only calls __remove_pages().

Note: __remove_pages() for some archtecuture is not implemented
       (I don't know how to implement it for s390).

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: Yasuaki Ishimatsu<isimatu.yasuaki@xxxxxxxxxxxxxx>
Signed-off-by: Wen Congyang<wency@xxxxxxxxxxxxxx>
---
  arch/ia64/mm/init.c            | 18 ++++++++++++++++++
  arch/powerpc/mm/mem.c          | 12 ++++++++++++
  arch/s390/mm/init.c            | 12 ++++++++++++
  arch/sh/mm/init.c              | 17 +++++++++++++++++
  arch/tile/mm/init.c            |  8 ++++++++
  arch/x86/mm/init_32.c          | 12 ++++++++++++
  arch/x86/mm/init_64.c          | 15 +++++++++++++++
  include/linux/memory_hotplug.h |  1 +
  mm/memory_hotplug.c            |  2 ++
  9 files changed, 97 insertions(+)

diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 082e383..e333822 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c
@@ -689,6 +689,24 @@ int arch_add_memory(int nid, u64 start, u64 size)

  	return ret;
  }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+int arch_remove_memory(u64 start, u64 size)
+{
+	unsigned long start_pfn = start>>  PAGE_SHIFT;
+	unsigned long nr_pages = size>>  PAGE_SHIFT;
+	struct zone *zone;
+	int ret;
+
+	zone = page_zone(pfn_to_page(start_pfn));
+	ret = __remove_pages(zone, start_pfn, nr_pages);
+	if (ret)
+		pr_warn("%s: Problem encountered in __remove_pages() as"
+			" ret=%d\n", __func__,  ret);
+
+	return ret;

Just a little question, why do we have different handlers for ret on
different platforms ?  Sometimes we print a msg, sometimes we just
return, and sometimes we give a WARN_ON(). But no big deal. :)

Reviewed-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>

+}
+#endif
  #endif

  /*
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 0dba506..09c6451 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -133,6 +133,18 @@ int arch_add_memory(int nid, u64 start, u64 size)

  	return __add_pages(nid, zone, start_pfn, nr_pages);
  }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+int arch_remove_memory(u64 start, u64 size)
+{
+	unsigned long start_pfn = start>>  PAGE_SHIFT;
+	unsigned long nr_pages = size>>  PAGE_SHIFT;
+	struct zone *zone;
+
+	zone = page_zone(pfn_to_page(start_pfn));
+	return __remove_pages(zone, start_pfn, nr_pages);
+}
+#endif
  #endif /* CONFIG_MEMORY_HOTPLUG */

  /*
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 81e596c..b565190 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -257,4 +257,16 @@ int arch_add_memory(int nid, u64 start, u64 size)
  		vmem_remove_mapping(start, size);
  	return rc;
  }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+int arch_remove_memory(u64 start, u64 size)
+{
+	/*
+	 * There is no hardware or firmware interface which could trigger a
+	 * hot memory remove on s390. So there is nothing that needs to be
+	 * implemented.
+	 */
+	return -EBUSY;
+}
+#endif
  #endif /* CONFIG_MEMORY_HOTPLUG */
diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 82cc576..1057940 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -558,4 +558,21 @@ int memory_add_physaddr_to_nid(u64 addr)
  EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
  #endif

+#ifdef CONFIG_MEMORY_HOTREMOVE
+int arch_remove_memory(u64 start, u64 size)
+{
+	unsigned long start_pfn = start>>  PAGE_SHIFT;
+	unsigned long nr_pages = size>>  PAGE_SHIFT;
+	struct zone *zone;
+	int ret;
+
+	zone = page_zone(pfn_to_page(start_pfn));
+	ret = __remove_pages(zone, start_pfn, nr_pages);
+	if (unlikely(ret))
+		pr_warn("%s: Failed, __remove_pages() == %d\n", __func__,
+			ret);
+
+	return ret;
+}
+#endif
  #endif /* CONFIG_MEMORY_HOTPLUG */
diff --git a/arch/tile/mm/init.c b/arch/tile/mm/init.c
index ef29d6c..2749515 100644
--- a/arch/tile/mm/init.c
+++ b/arch/tile/mm/init.c
@@ -935,6 +935,14 @@ int remove_memory(u64 start, u64 size)
  {
  	return -EINVAL;
  }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+int arch_remove_memory(u64 start, u64 size)
+{
+	/* TODO */
+	return -EBUSY;
+}
+#endif
  #endif

  struct kmem_cache *pgd_cache;
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 11a5800..b19eba4 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -839,6 +839,18 @@ int arch_add_memory(int nid, u64 start, u64 size)

  	return __add_pages(nid, zone, start_pfn, nr_pages);
  }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+int arch_remove_memory(u64 start, u64 size)
+{
+	unsigned long start_pfn = start>>  PAGE_SHIFT;
+	unsigned long nr_pages = size>>  PAGE_SHIFT;
+	struct zone *zone;
+
+	zone = page_zone(pfn_to_page(start_pfn));
+	return __remove_pages(zone, start_pfn, nr_pages);
+}
+#endif
  #endif

  /*
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 3baff25..5675335 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -680,6 +680,21 @@ int arch_add_memory(int nid, u64 start, u64 size)
  }
  EXPORT_SYMBOL_GPL(arch_add_memory);

+#ifdef CONFIG_MEMORY_HOTREMOVE
+int __ref arch_remove_memory(u64 start, u64 size)
+{
+	unsigned long start_pfn = start>>  PAGE_SHIFT;
+	unsigned long nr_pages = size>>  PAGE_SHIFT;
+	struct zone *zone;
+	int ret;
+
+	zone = page_zone(pfn_to_page(start_pfn));
+	ret = __remove_pages(zone, start_pfn, nr_pages);
+	WARN_ON_ONCE(ret);
+
+	return ret;
+}
+#endif
  #endif /* CONFIG_MEMORY_HOTPLUG */

  static struct kcore_list kcore_vsyscall;
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 38675e9..191b2d9 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -85,6 +85,7 @@ extern void __online_page_free(struct page *page);

  #ifdef CONFIG_MEMORY_HOTREMOVE
  extern bool is_pageblock_removable_nolock(struct page *page);
+extern int arch_remove_memory(u64 start, u64 size);
  #endif /* CONFIG_MEMORY_HOTREMOVE */

  /* reasonably generic interface to expand the physical pages in a zone  */
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 63d5388..e741732 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1111,6 +1111,8 @@ repeat:
  	/* remove memmap entry */
  	firmware_map_remove(start, start + size, "System RAM");

+	arch_remove_memory(start, size);
+
  	unlock_memory_hotplug();

  	return 0;

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