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    SubjectRe: [RFC PATCH 10/12] memory-hotplug : free memmap of sparse-vmemmap
    On 06/27/2012 01:56 PM, Yasuaki Ishimatsu wrote:
    > I don't think that all pages of virtual mapping in removed memory can be
    > freed, since page which type is MIX_SECTION_INFO is difficult to free.
    > So, the patch only frees page which type is SECTION_INFO at first.
    >
    > 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/x86/mm/init_64.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++
    > include/linux/mm.h | 2 +
    > mm/memory_hotplug.c | 5 ++
    > mm/sparse.c | 5 +-
    > 4 files changed, 99 insertions(+), 2 deletions(-)
    >
    > Index: linux-3.5-rc4/include/linux/mm.h
    > ===================================================================
    > --- linux-3.5-rc4.orig/include/linux/mm.h 2012-06-27 09:11:13.790150442 +0900
    > +++ linux-3.5-rc4/include/linux/mm.h 2012-06-27 09:11:16.433117400 +0900
    > @@ -1588,6 +1588,8 @@ int vmemmap_populate(struct page *start_
    > void vmemmap_populate_print_last(void);
    > void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
    > unsigned long size);
    > +void vmemmap_kfree(struct page *memmpa, unsigned long nr_pages);
    > +void vmemmap_free_bootmem(struct page *memmpa, unsigned long nr_pages);
    >
    > enum mf_flags {
    > MF_COUNT_INCREASED = 1 << 0,
    > Index: linux-3.5-rc4/mm/sparse.c
    > ===================================================================
    > --- linux-3.5-rc4.orig/mm/sparse.c 2012-06-27 09:06:35.317631878 +0900
    > +++ linux-3.5-rc4/mm/sparse.c 2012-06-27 09:11:16.434117388 +0900
    > @@ -614,12 +614,13 @@ static inline struct page *kmalloc_secti
    > /* This will make the necessary allocations eventually. */
    > return sparse_mem_map_populate(pnum, nid);
    > }
    > -static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
    > +static void __kfree_section_memmap(struct page *page, unsigned long nr_pages)
    > {
    > - return; /* XXX: Not implemented yet */
    > + vmemmap_kfree(page, nr_pages);
    > }
    > static void free_map_bootmem(struct page *page, unsigned long nr_pages)
    > {
    > + vmemmap_free_bootmem(page, nr_pages);
    > }
    > #else
    > static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
    > Index: linux-3.5-rc4/arch/x86/mm/init_64.c
    > ===================================================================
    > --- linux-3.5-rc4.orig/arch/x86/mm/init_64.c 2012-06-27 09:11:13.791150430 +0900
    > +++ linux-3.5-rc4/arch/x86/mm/init_64.c 2012-06-27 09:11:59.254581998 +0900
    > @@ -978,6 +978,95 @@ vmemmap_populate(struct page *start_page
    > return 0;
    > }
    >
    > +unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
    > + struct page *page)
    I think the third parameter should be "struct page **pp" instead of "struct page *page".
    And "page = pte_page(*pte)" should be "*pp = pte_page(*pte)".
    Otherwise the found page pointer can't be returned to the caller and vmemmap_kfree()
    just sees random value in variable "page".

    > +{
    > + pgd_t *pgd;
    > + pud_t *pud;
    > + pmd_t *pmd;
    > + pte_t *pte;
    > + unsigned long next;
    > +
    > + page = NULL;
    > +
    > + pgd = pgd_offset_k(addr);
    > + if (pgd_none(*pgd))
    > + return PAGE_SIZE;
    > +
    > + pud = pud_offset(pgd, addr);
    > + if (pud_none(*pud))
    > + return PAGE_SIZE;
    > +
    > + if (!cpu_has_pse) {
    > + next = (addr + PAGE_SIZE) & PAGE_MASK;
    > + pmd = pmd_offset(pud, addr);
    > + if (pmd_none(*pmd))
    > + return next;
    > +
    > + pte = pte_offset_kernel(pmd, addr);
    > + if (pte_none(*pte))
    > + return next;
    > +
    > + page = pte_page(*pte);
    > + pte_clear(&init_mm, addr, pte);
    > + } else {
    > + next = pmd_addr_end(addr, end);
    > +
    > + pmd = pmd_offset(pud, addr);
    > + if (pmd_none(*pmd))
    > + return next;
    > +
    > + page = pmd_page(*pmd);
    > + pmd_clear(pmd);
    > + }
    > +
    > + return next;
    > +}
    > +
    > +void __meminit
    > +vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
    > +{
    > + unsigned long addr = (unsigned long)memmap;
    > + unsigned long end = (unsigned long)(memmap + nr_pages);
    > + unsigned long next;
    > + unsigned int order;
    > + struct page *page;
    > +
    > + for (; addr < end; addr = next) {
    > + next = find_and_clear_pte_page(addr, end, page);
    > + if (!page)
    > + continue;
    > +
    > + if (is_vmalloc_addr(page))
    > + vfree(page);
    > + else {
    > + order = next - addr;
    > + free_pages((unsigned long)page,
    > + get_order(sizeof(struct page) * order));
    > + }
    > + }
    > +}
    > +
    > +void __meminit
    > +vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
    > +{
    > + unsigned long addr = (unsigned long)memmap;
    > + unsigned long end = (unsigned long)(memmap + nr_pages);
    > + unsigned long next;
    > + struct page *page;
    > + unsigned long magic;
    > +
    > + for (; addr < end; addr = next) {
    > + next = find_and_clear_pte_page(addr, end, page);
    > + if (!page)
    > + continue;
    > +
    > + magic = (unsigned long) page->lru.next;
    > + if (magic == SECTION_INFO)
    > + put_page_bootmem(page);
    > + }
    > +}
    > +
    > void __meminit
    > register_page_bootmem_memmap(unsigned long section_nr, struct page *start_page,
    > unsigned long size)
    > Index: linux-3.5-rc4/mm/memory_hotplug.c
    > ===================================================================
    > --- linux-3.5-rc4.orig/mm/memory_hotplug.c 2012-06-27 09:11:13.789150454 +0900
    > +++ linux-3.5-rc4/mm/memory_hotplug.c 2012-06-27 09:11:16.436117363 +0900
    > @@ -303,6 +303,8 @@ static int __meminit __add_section(int n
    > #ifdef CONFIG_SPARSEMEM_VMEMMAP
    > static int __remove_section(struct zone *zone, struct mem_section *ms)
    > {
    > + unsigned long flags;
    > + struct pglist_data *pgdat = zone->zone_pgdat;
    > int ret;
    >
    > if (!valid_section(ms))
    > @@ -310,6 +312,9 @@ static int __remove_section(struct zone
    >
    > ret = unregister_memory_section(ms);
    >
    > + pgdat_resize_lock(pgdat, &flags);
    > + sparse_remove_one_section(zone, ms);
    > + pgdat_resize_unlock(pgdat, &flags);
    > return ret;
    > }
    > #else
    >
    > --
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    >




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