Re: [PATCH v3 08/12] memory-hotplug: remove memmap of sparse-vmemmap

Wen Congyang
2012-11-27T07:00:57Z

At 11/27/2012 01:47 PM, Jianguo Wu Wrote:
> On 2012/11/1 17:44, Wen Congyang wrote:
>
>> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>
>> 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.
>>
>> Note: vmemmap_kfree() and vmemmap_free_bootmem() are not implemented for ia64,
>> ppc, s390, and sparc.
>>
>> CC: David Rientjes <rientjes@google.com>
>> CC: Jiang Liu <liuj97@gmail.com>
>> CC: Len Brown <len.brown@intel.com>
>> 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/ia64/mm/discontig.c | 8 ++++
>> arch/powerpc/mm/init_64.c | 8 ++++
>> arch/s390/mm/vmem.c | 8 ++++
>> arch/sparc/mm/init_64.c | 8 ++++
>> arch/x86/mm/init_64.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/mm.h | 2 +
>> mm/memory_hotplug.c | 17 +------
>> mm/sparse.c | 5 +-
>> 8 files changed, 158 insertions(+), 17 deletions(-)
>>
>> diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
>> index 33943db..0d23b69 100644
>> --- a/arch/ia64/mm/discontig.c
>> +++ b/arch/ia64/mm/discontig.c
>> @@ -823,6 +823,14 @@ int __meminit vmemmap_populate(struct page *start_page,
>> return vmemmap_populate_basepages(start_page, size, node);
>> }
>>
>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> void register_page_bootmem_memmap(unsigned long section_nr,
>> struct page *start_page, unsigned long size)
>> {
>> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
>> index 6466440..df7d155 100644
>> --- a/arch/powerpc/mm/init_64.c
>> +++ b/arch/powerpc/mm/init_64.c
>> @@ -298,6 +298,14 @@ int __meminit vmemmap_populate(struct page *start_page,
>> return 0;
>> }
>>
>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> void register_page_bootmem_memmap(unsigned long section_nr,
>> struct page *start_page, unsigned long size)
>> {
>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
>> index 4f4803a..ab69c34 100644
>> --- a/arch/s390/mm/vmem.c
>> +++ b/arch/s390/mm/vmem.c
>> @@ -236,6 +236,14 @@ out:
>> return ret;
>> }
>>
>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> void register_page_bootmem_memmap(unsigned long section_nr,
>> struct page *start_page, unsigned long size)
>> {
>> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
>> index 75a984b..546855d 100644
>> --- a/arch/sparc/mm/init_64.c
>> +++ b/arch/sparc/mm/init_64.c
>> @@ -2232,6 +2232,14 @@ void __meminit vmemmap_populate_print_last(void)
>> }
>> }
>>
>> +void vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> +void vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
>> +{
>> +}
>> +
>> void register_page_bootmem_memmap(unsigned long section_nr,
>> struct page *start_page, unsigned long size)
>> {
>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>> index 795dae3..e85626d 100644
>> --- a/arch/x86/mm/init_64.c
>> +++ b/arch/x86/mm/init_64.c
>> @@ -998,6 +998,125 @@ vmemmap_populate(struct page *start_page, unsigned long size, int node)
>> 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 = NULL;
>> + 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(addr);
>> + }
>> +}
>> +
>> +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)
>> {
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 8e5a56f..42b8723 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1642,6 +1642,8 @@ int vmemmap_populate(struct page *start_page, unsigned long pages, int node);
>> 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,
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index db9806c..03153cf 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -312,19 +312,6 @@ static int __meminit __add_section(int nid, struct zone *zone,
>> 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;
>> -
>> - if (!valid_section(ms))
>> - return ret;
>> -
>> - ret = unregister_memory_section(ms);
>> -
>> - return ret;
>> -}
>> -#else
>> static int __remove_section(struct zone *zone, struct mem_section *ms)
>> {
>> unsigned long flags;
>> @@ -341,9 +328,9 @@ static int __remove_section(struct zone *zone, struct mem_section *ms)
>> 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
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index fac95f2..ab9d755 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -613,12 +613,13 @@ static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
>> /* 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);
>> }
>
> Hi Congyang,
> For vmemmap, nr_pages should be PAGES_PER_SECTION for free_map_bootmem(),
> which is passed by free_section_usemap(), right?
> But now, nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page)) >> PAGE_SHIFT.
>
> Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
> ---
> mm/sparse.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index fac95f2..31e5282 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -713,8 +713,12 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
> struct page *memmap_page;
> memmap_page = virt_to_page(memmap);
>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + nr_pages = PAGES_PER_SECTION;
> +#else
> nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
> >> PAGE_SHIFT;
> +#endif

Hmm, to avoid using ifdef, I think we can pass PAGE_PER_SECTION to free_map_bootmem(),
and calculate how many pages is used to store struct page.

Thanks
Wen Congyang

>
> free_map_bootmem(memmap_page, nr_pages);
> }