Re: [RFC PATCH v4 7/13] memory-hotplug : remove_memory calls __remove_pages

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Hi Bob,

2012/07/19 17:32, Bob Liu wrote:
On Wed, Jul 18, 2012 at 6:12 PM, Yasuaki Ishimatsu
<isimatu.yasuaki@xxxxxxxxxxxxxx> wrote:
The patch adds __remove_pages() to remove_memory(). Then the range of
phys_start_pfn argument and nr_pages argument in __remove_pagse() may
have different zone. So zone argument is removed from __remove_pages()
and __remove_pages() caluculates zone in each section.

When CONFIG_SPARSEMEM_VMEMMAP is defined, there is no way to remove a memmap.
So __remove_section only calls unregister_memory_section().

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>

---
  arch/powerpc/platforms/pseries/hotplug-memory.c |    5 +----
  include/linux/memory_hotplug.h                  |    3 +--
  mm/memory_hotplug.c                             |   19 ++++++++++++-------
  3 files changed, 14 insertions(+), 13 deletions(-)

Index: linux-3.5-rc6/mm/memory_hotplug.c
===================================================================
--- linux-3.5-rc6.orig/mm/memory_hotplug.c      2012-07-18 18:00:27.440145432 +0900
+++ linux-3.5-rc6/mm/memory_hotplug.c   2012-07-18 18:01:02.070712487 +0900
@@ -275,11 +275,14 @@ static int __meminit __add_section(int n
  #ifdef CONFIG_SPARSEMEM_VMEMMAP
  static int __remove_section(struct zone *zone, struct mem_section *ms)
  {
-       /*
-        * XXX: Freeing memmap with vmemmap is not implement yet.
-        *      This should be removed later.
-        */
-       return -EBUSY;
+       int ret = -EINVAL;
+
+       if (!valid_section(ms))
+               return ret;
+
+       ret = unregister_memory_section(ms);
+

I saw a patch from Jiang Liu "mm/hotplug: free zone->pageset when a
zone becomes empty" to
free the zone->pageset and i think there may more cleanup needed when
a zone becomes empty.

We already have __add_zone() in __add_section(), what about add a
function like __remove_zone()
to do the cleanup here?

Thank you for your cooment. As you say, I think cleanup function of zone
is necessary. So I'll update it.

Thanks,
Yasuaki Ishimatsu.


+       return ret;
  }
  #else
  static int __remove_section(struct zone *zone, struct mem_section *ms)
@@ -346,11 +349,11 @@ EXPORT_SYMBOL_GPL(__add_pages);
   * sure that pages are marked reserved and zones are adjust properly by
   * calling offline_pages().
   */
-int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
-                unsigned long nr_pages)
+int __remove_pages(unsigned long phys_start_pfn, unsigned long nr_pages)
  {
         unsigned long i, ret = 0;
         int sections_to_remove;
+       struct zone *zone;

         /*
          * We can only remove entire sections
@@ -363,6 +366,7 @@ int __remove_pages(struct zone *zone, un
         sections_to_remove = nr_pages / PAGES_PER_SECTION;
         for (i = 0; i < sections_to_remove; i++) {
                 unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
+               zone = page_zone(pfn_to_page(pfn));
                 ret = __remove_section(zone, __pfn_to_section(pfn));
                 if (ret)
                         break;
@@ -1031,6 +1035,7 @@ int __ref remove_memory(int nid, u64 sta
         /* remove memmap entry */
         firmware_map_remove(start, start + size, "System RAM");

+       __remove_pages(start >> PAGE_SHIFT, size >> PAGE_SHIFT);
  out:
         unlock_memory_hotplug();
         return ret;
Index: linux-3.5-rc6/include/linux/memory_hotplug.h
===================================================================
--- linux-3.5-rc6.orig/include/linux/memory_hotplug.h   2012-07-18 18:00:27.445145371 +0900
+++ linux-3.5-rc6/include/linux/memory_hotplug.h        2012-07-18 18:00:40.461982690 +0900
@@ -89,8 +89,7 @@ extern bool is_pageblock_removable_noloc
  /* reasonably generic interface to expand the physical pages in a zone  */
  extern int __add_pages(int nid, struct zone *zone, unsigned long start_pfn,
         unsigned long nr_pages);
-extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
-       unsigned long nr_pages);
+extern int __remove_pages(unsigned long start_pfn, unsigned long nr_pages);

  #ifdef CONFIG_NUMA
  extern int memory_add_physaddr_to_nid(u64 start);
Index: linux-3.5-rc6/arch/powerpc/platforms/pseries/hotplug-memory.c
===================================================================
--- linux-3.5-rc6.orig/arch/powerpc/platforms/pseries/hotplug-memory.c  2012-07-18 18:00:27.442145407 +0900
+++ linux-3.5-rc6/arch/powerpc/platforms/pseries/hotplug-memory.c       2012-07-18 18:00:40.470982578 +0900
@@ -76,7 +76,6 @@ unsigned long memory_block_size_bytes(vo
  static int pseries_remove_memblock(unsigned long base, unsigned int memblock_size)
  {
         unsigned long start, start_pfn;
-       struct zone *zone;
         int i, ret;
         int sections_to_remove;

@@ -87,8 +86,6 @@ static int pseries_remove_memblock(unsig
                 return 0;
         }

-       zone = page_zone(pfn_to_page(start_pfn));
-
         /*
          * Remove section mappings and sysfs entries for the
          * section of the memory we are removing.
@@ -101,7 +98,7 @@ static int pseries_remove_memblock(unsig
         sections_to_remove = (memblock_size >> PAGE_SHIFT) / PAGES_PER_SECTION;
         for (i = 0; i < sections_to_remove; i++) {
                 unsigned long pfn = start_pfn + i * PAGES_PER_SECTION;
-               ret = __remove_pages(zone, start_pfn,  PAGES_PER_SECTION);
+               ret = __remove_pages(start_pfn,  PAGES_PER_SECTION);
                 if (ret)
                         return ret;
         }

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