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SubjectRe: [RFC PATCH v4 11/13] memory-hotplug : free memmap of sparse-vmemmap
At 07/18/2012 06:16 PM, Yasuaki Ishimatsu Wrote:
> All pages of virtual mapping in removed memory cannot be freed, since some pages
> used as PGD/PUD includes not only removed memory but also other memory. So the
> patch checks whether page can be freed or not.
>
> How to check whether page can be freed or not?
> 1. When removing memory, the page structs of the revmoved memory are filled
> with 0FD.
> 2. All page structs are filled with 0xFD on PT/PMD, PT/PMD can be cleared.
> In this case, the page used as PT/PMD can be freed.
>
> Applying patch, __remove_section() of CONFIG_SPARSEMEM_VMEMMAP is integrated
> into one. So __remove_section() of CONFIG_SPARSEMEM_VMEMMAP is deleted.
>
> 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/x86/mm/init_64.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mm.h | 2
> mm/memory_hotplug.c | 19 -------
> mm/sparse.c | 5 +-
> 4 files changed, 128 insertions(+), 19 deletions(-)
>
> Index: linux-3.5-rc6/include/linux/mm.h
> ===================================================================
> --- linux-3.5-rc6.orig/include/linux/mm.h 2012-07-18 18:01:28.000000000 +0900
> +++ linux-3.5-rc6/include/linux/mm.h 2012-07-18 18:03:05.551168773 +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-rc6/mm/sparse.c
> ===================================================================
> --- linux-3.5-rc6.orig/mm/sparse.c 2012-07-18 17:59:25.000000000 +0900
> +++ linux-3.5-rc6/mm/sparse.c 2012-07-18 18:03:05.553168749 +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-rc6/arch/x86/mm/init_64.c
> ===================================================================
> --- linux-3.5-rc6.orig/arch/x86/mm/init_64.c 2012-07-18 18:01:28.000000000 +0900
> +++ linux-3.5-rc6/arch/x86/mm/init_64.c 2012-07-18 18:03:05.564168611 +0900
> @@ -978,6 +978,127 @@ vmemmap_populate(struct page *start_page
> return 0;
> }
>
> +#define PAGE_INUSE 0xFD
> +
> +unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
> + struct page **pp, int *page_size)
> +{
> + pgd_t *pgd;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *pte;
> + void *page_addr;
> + unsigned long next;
> +
> + *pp = NULL;
> +
> + pgd = pgd_offset_k(addr);
> + if (pgd_none(*pgd))
> + return pgd_addr_end(addr, end);
> +
> + pud = pud_offset(pgd, addr);
> + if (pud_none(*pud))
> + return pud_addr_end(addr,end);
> +
> + 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_size = PAGE_SIZE;
> + *pp = pte_page(*pte);
> + } else {
> + next = pmd_addr_end(addr, end);
> +
> + pmd = pmd_offset(pud, addr);
> + if (pmd_none(*pmd))
> + return next;
> +
> + *page_size = PMD_SIZE;
> + *pp = pmd_page(*pmd);
> + }
> +
> + /*
> + * Removed page structs are filled with 0xFD.
> + */
> + memset((void *)addr, PAGE_INUSE, next - addr);
> +
> + page_addr = page_address(*pp);
> +
> + /*
> + * Check the page is filled with 0xFD or not.
> + * memchr_inv() returns the address. In this case, we cannot
> + * clear PTE/PUD entry, since the page is used by other.
> + * So we cannot also free the page.
> + *
> + * memchr_inv() returns NULL. In this case, we can clear
> + * PTE/PUD entry, since the page is not used by other.
> + * So we can also free the page.
> + */
> + if (memchr_inv(page_addr, PAGE_INUSE, *page_size)) {
> + *pp = NULL;
> + return next;
> + }
> +
> + if (!cpu_has_pse)
> + pte_clear(&init_mm, addr, pte);
> + else
> + pmd_clear(pmd);
> +
> + return next;
> +}
> +
> +void 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;
> + struct page *page;
> + int page_size;
> +
> + for (; addr < end; addr = next) {
> + page = NULL;
> + page_size = 0;
> + next = find_and_clear_pte_page(addr, end, &page, &page_size);
> + if (!page)
> + continue;
> +
> + free_pages((unsigned long)page_address(page),
> + get_order(page_size));
> + __flush_tlb_one((unsigned long)page_address(page));
> + }
> +
> +}
> +
> +void 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;
> + int page_size;
> + unsigned long magic;
> +
> + for (; addr < end; addr = next) {
> + page = NULL;
> + page_size = 0;
> + next = find_and_clear_pte_page(addr, end, &page, &page_size);
> + if (!page)
> + continue;
> +
> + magic = (unsigned long) page->lru.next;
> + if (magic == SECTION_INFO)
> + put_page_bootmem(page);
> + flush_tlb_kernel_range(addr, end);
> + }
> +
> +}
> +
> void register_page_bootmem_memmap(unsigned long section_nr,
> struct page *start_page, unsigned long size)
> {
> Index: linux-3.5-rc6/mm/memory_hotplug.c
> ===================================================================
> --- linux-3.5-rc6.orig/mm/memory_hotplug.c 2012-07-18 18:01:28.000000000 +0900
> +++ linux-3.5-rc6/mm/memory_hotplug.c 2012-07-18 18:25:11.036597977 +0900
> @@ -300,7 +300,6 @@ static int __meminit __add_section(int n
> return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
> }
>
> -#ifdef CONFIG_SPARSEMEM_VMEMMAP
> static int __remove_section(struct zone *zone, struct mem_section *ms)
> {
> int ret = -EINVAL;
> @@ -309,29 +308,15 @@ static int __remove_section(struct zone
> return ret;
>
> ret = unregister_memory_section(ms);
> -
> - return ret;
> -}
> -#else
> -static int __remove_section(struct zone *zone, struct mem_section *ms)
> -{
> - unsigned long flags;
> - struct pglist_data *pgdat = zone->zone_pgdat;

This two line should not be removed. Otherwise, we can not build the kernel.

Thanks
Wen Congyang

> - int ret = -EINVAL;
> -
> - if (!valid_section(ms))
> - return ret;
> -
> - ret = unregister_memory_section(ms);
> if (ret)
> return ret;
>
> pgdat_resize_lock(pgdat, &flags);
> sparse_remove_one_section(zone, ms);
> pgdat_resize_unlock(pgdat, &flags);
> - return 0;
> +
> + return ret;
> }
> -#endif
>
> /*
> * Reasonably generic function for adding memory. It is
>
> --
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