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    SubjectRe: [RFC PATCH v4 7/13] memory-hotplug : remove_memory calls __remove_pages
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    On Wed, Jul 18, 2012 at 6:12 PM, Yasuaki Ishimatsu
    <isimatu.yasuaki@jp.fujitsu.com> 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@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>
    >
    > ---
    > 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?

    > + 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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    --
    Regards,
    --Bob


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