Patchwork [v4,08/12] memory-hotplug: remove memmap of sparse-vmemmap

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Submitter Jianguo Wu
Date Dec. 3, 2012, 2:23 a.m.
Message ID <50BC0D2D.8040008@huawei.com>
Download mbox | patch
Permalink /patch/203260/
State Not Applicable
Headers show

Comments

Jianguo Wu - Dec. 3, 2012, 2:23 a.m.
Hi Congyang,

This is the new version.

Thanks,
Jianguo Wu.


Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
---
 include/linux/mm.h  |    1 +
 mm/sparse-vmemmap.c |  231 +++++++++++++++++++++++++++++++++++++++++++++++++++
 mm/sparse.c         |    3 +-
 3 files changed, 234 insertions(+), 1 deletions(-)
Tang Chen - Dec. 4, 2012, 9:13 a.m.
Hi Wu,

Sorry to make noise here. Please see below. :)

On 12/03/2012 10:23 AM, Jianguo Wu wrote:
> Signed-off-by: Jianguo Wu<wujianguo@huawei.com>
> Signed-off-by: Jiang Liu<jiang.liu@huawei.com>
> ---
>   include/linux/mm.h  |    1 +
>   mm/sparse-vmemmap.c |  231 +++++++++++++++++++++++++++++++++++++++++++++++++++
>   mm/sparse.c         |    3 +-
>   3 files changed, 234 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5657670..1f26af5 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1642,6 +1642,7 @@ 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_free(struct page *memmap, unsigned long nr_pages);
>
>   enum mf_flags {
>   	MF_COUNT_INCREASED = 1<<  0,
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 1b7e22a..748732d 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -29,6 +29,10 @@
>   #include<asm/pgalloc.h>
>   #include<asm/pgtable.h>
>
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +#include<asm/tlbflush.h>
> +#endif
> +
>   /*
>    * Allocate a block of memory to be used to back the virtual memory map
>    * or to back the page tables that are used to create the mapping.
> @@ -224,3 +228,230 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>   		vmemmap_buf_end = NULL;
>   	}
>   }
> +
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +
> +#define PAGE_INUSE 0xFD
> +
> +static void vmemmap_free_pages(struct page *page, int order)
> +{
> +	struct zone *zone;
> +	unsigned long magic;
> +
> +	magic = (unsigned long) page->lru.next;
> +	if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
> +		put_page_bootmem(page);
> +
> +		zone = page_zone(page);
> +		zone_span_writelock(zone);
> +		zone->present_pages++;
> +		zone_span_writeunlock(zone);
> +		totalram_pages++;

Seems that we have different ways to handle pages allocated by bootmem
or by regular allocator. Is the checking way in [PATCH 09/12] available
here ?

+	/* bootmem page has reserved flag */
+	if (PageReserved(page)) {
......
+	}

If so, I think we can just merge these two functions.

> +	} else
> +		free_pages((unsigned long)page_address(page), order);
> +}
> +
> +static void free_pte_table(pmd_t *pmd)
> +{
> +	pte_t *pte, *pte_start;
> +	int i;
> +
> +	pte_start = (pte_t *)pmd_page_vaddr(*pmd);
> +	for (i = 0; i<  PTRS_PER_PTE; i++) {
> +		pte = pte_start + i;
> +		if (pte_val(*pte))
> +			return;
> +	}
> +
> +	/* free a pte talbe */
> +	vmemmap_free_pages(pmd_page(*pmd), 0);
> +	spin_lock(&init_mm.page_table_lock);
> +	pmd_clear(pmd);
> +	spin_unlock(&init_mm.page_table_lock);
> +}
> +
> +static void free_pmd_table(pud_t *pud)
> +{
> +	pmd_t *pmd, *pmd_start;
> +	int i;
> +
> +	pmd_start = (pmd_t *)pud_page_vaddr(*pud);
> +	for (i = 0; i<  PTRS_PER_PMD; i++) {
> +		pmd = pmd_start + i;
> +		if (pmd_val(*pmd))
> +			return;
> +	}
> +
> +	/* free a pmd talbe */
> +	vmemmap_free_pages(pud_page(*pud), 0);
> +	spin_lock(&init_mm.page_table_lock);
> +	pud_clear(pud);
> +	spin_unlock(&init_mm.page_table_lock);
> +}
> +
> +static void free_pud_table(pgd_t *pgd)
> +{
> +	pud_t *pud, *pud_start;
> +	int i;
> +
> +	pud_start = (pud_t *)pgd_page_vaddr(*pgd);
> +	for (i = 0; i<  PTRS_PER_PUD; i++) {
> +		pud = pud_start + i;
> +		if (pud_val(*pud))
> +			return;
> +	}
> +
> +	/* free a pud table */
> +	vmemmap_free_pages(pgd_page(*pgd), 0);
> +	spin_lock(&init_mm.page_table_lock);
> +	pgd_clear(pgd);
> +	spin_unlock(&init_mm.page_table_lock);
> +}

All the free_xxx_table() are very similar to the functions in
[PATCH 09/12]. Could we reuse them anyway ?

> +
> +static int split_large_page(pte_t *kpte, unsigned long address, pte_t *pbase)
> +{
> +	struct page *page = pmd_page(*(pmd_t *)kpte);
> +	int i = 0;
> +	unsigned long magic;
> +	unsigned long section_nr;
> +
> +	__split_large_page(kpte, address, pbase);

Is this patch going to replace [PATCH 08/12] ?

If so, __split_large_page() was added and exported in [PATCH 09/12],
then we should move it here, right ?

If not, free_map_bootmem() and __kfree_section_memmap() were changed in
[PATCH 08/12], and we need to handle this.

> +	__flush_tlb_all();
> +
> +	magic = (unsigned long) page->lru.next;
> +	if (magic == SECTION_INFO) {
> +		section_nr = pfn_to_section_nr(page_to_pfn(page));
> +		while (i<  PTRS_PER_PMD) {
> +			page++;
> +			i++;
> +			get_page_bootmem(section_nr, page, SECTION_INFO);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void vmemmap_pte_remove(pmd_t *pmd, unsigned long addr, unsigned long end)
> +{
> +	pte_t *pte;
> +	unsigned long next;
> +	void *page_addr;
> +
> +	pte = pte_offset_kernel(pmd, addr);
> +	for (; addr<  end; pte++, addr += PAGE_SIZE) {
> +		next = (addr + PAGE_SIZE)&  PAGE_MASK;
> +		if (next>  end)
> +			next = end;
> +
> +		if (pte_none(*pte))
> +			continue;
> +		if (IS_ALIGNED(addr, PAGE_SIZE)&&
> +		    IS_ALIGNED(next, PAGE_SIZE)) {
> +			vmemmap_free_pages(pte_page(*pte), 0);
> +			spin_lock(&init_mm.page_table_lock);
> +			pte_clear(&init_mm, addr, pte);
> +			spin_unlock(&init_mm.page_table_lock);
> +		} else {
> +			/*
> +			 * Removed page structs are filled with 0xFD.
> +			 */
> +			memset((void *)addr, PAGE_INUSE, next - addr);
> +			page_addr = page_address(pte_page(*pte));
> +
> +			if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
> +				spin_lock(&init_mm.page_table_lock);
> +				pte_clear(&init_mm, addr, pte);
> +				spin_unlock(&init_mm.page_table_lock);
> +			}
> +		}
> +	}
> +
> +	free_pte_table(pmd);
> +	__flush_tlb_all();
> +}
> +
> +static void vmemmap_pmd_remove(pud_t *pud, unsigned long addr, unsigned long end)
> +{
> +	unsigned long next;
> +	pmd_t *pmd;
> +
> +	pmd = pmd_offset(pud, addr);
> +	for (; addr<  end; addr = next, pmd++) {
> +		next = pmd_addr_end(addr, end);
> +		if (pmd_none(*pmd))
> +			continue;
> +
> +		if (cpu_has_pse) {
> +			unsigned long pte_base;
> +
> +			if (IS_ALIGNED(addr, PMD_SIZE)&&
> +			    IS_ALIGNED(next, PMD_SIZE)) {
> +				vmemmap_free_pages(pmd_page(*pmd),
> +						   get_order(PMD_SIZE));
> +				spin_lock(&init_mm.page_table_lock);
> +				pmd_clear(pmd);
> +				spin_unlock(&init_mm.page_table_lock);
> +				continue;
> +			}
> +
> +			/*
> +			 * We use 2M page, but we need to remove part of them,
> +			 * so split 2M page to 4K page.
> +			 */
> +			pte_base = get_zeroed_page(GFP_ATOMIC | __GFP_NOTRACK);
> +			if (!pte_base) {
> +				WARN_ON(1);
> +				continue;
> +			}
> +
> +			split_large_page((pte_t *)pmd, addr, (pte_t *)pte_base);
> +			__flush_tlb_all();
> +
> +			spin_lock(&init_mm.page_table_lock);
> +			pmd_populate_kernel(&init_mm, pmd, (pte_t *)pte_base);
> +			spin_unlock(&init_mm.page_table_lock);
> +		}
> +
> +		vmemmap_pte_remove(pmd, addr, next);
> +	}
> +
> +	free_pmd_table(pud);
> +	__flush_tlb_all();
> +}
> +
> +static void vmemmap_pud_remove(pgd_t *pgd, unsigned long addr, unsigned long end)
> +{
> +	unsigned long next;
> +	pud_t *pud;
> +
> +	pud = pud_offset(pgd, addr);
> +	for (; addr<  end; addr = next, pud++) {
> +		next = pud_addr_end(addr, end);
> +		if (pud_none(*pud))
> +			continue;
> +
> +		vmemmap_pmd_remove(pud, addr, next);
> +	}
> +
> +	free_pud_table(pgd);
> +	__flush_tlb_all();
> +}
> +
> +void vmemmap_free(struct page *memmap, unsigned long nr_pages)
> +{
> +	unsigned long addr = (unsigned long)memmap;
> +	unsigned long end = (unsigned long)(memmap + nr_pages);
> +	unsigned long next;
> +
> +	for (; addr<  end; addr = next) {
> +		pgd_t *pgd = pgd_offset_k(addr);
> +
> +		next = pgd_addr_end(addr, end);
> +		if (!pgd_present(*pgd))
> +			continue;
> +
> +		vmemmap_pud_remove(pgd, addr, next);
> +		sync_global_pgds(addr, next - 1);
> +	}
> +}
> +#endif
> diff --git a/mm/sparse.c b/mm/sparse.c
> index fac95f2..4060229 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -615,10 +615,11 @@ static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
>   }
>   static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
>   {
> -	return; /* XXX: Not implemented yet */
> +	vmemmap_free(memmap, nr_pages);
>   }
>   static void free_map_bootmem(struct page *page, unsigned long nr_pages)

In the latest kernel, this line was:
static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)

>   {
> +	vmemmap_free(page, nr_pages);
>   }
>   #else
>   static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
Jianguo Wu - Dec. 4, 2012, 12:20 p.m.
Hi Tang,

Thanks for your review and comments, Please see below for my reply.

On 2012/12/4 17:13, Tang Chen wrote:

> Hi Wu,
> 
> Sorry to make noise here. Please see below. :)
> 
> On 12/03/2012 10:23 AM, Jianguo Wu wrote:
>> Signed-off-by: Jianguo Wu<wujianguo@huawei.com>
>> Signed-off-by: Jiang Liu<jiang.liu@huawei.com>
>> ---
>>   include/linux/mm.h  |    1 +
>>   mm/sparse-vmemmap.c |  231 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>   mm/sparse.c         |    3 +-
>>   3 files changed, 234 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 5657670..1f26af5 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1642,6 +1642,7 @@ 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_free(struct page *memmap, unsigned long nr_pages);
>>
>>   enum mf_flags {
>>       MF_COUNT_INCREASED = 1<<  0,
>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>> index 1b7e22a..748732d 100644
>> --- a/mm/sparse-vmemmap.c
>> +++ b/mm/sparse-vmemmap.c
>> @@ -29,6 +29,10 @@
>>   #include<asm/pgalloc.h>
>>   #include<asm/pgtable.h>
>>
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +#include<asm/tlbflush.h>
>> +#endif
>> +
>>   /*
>>    * Allocate a block of memory to be used to back the virtual memory map
>>    * or to back the page tables that are used to create the mapping.
>> @@ -224,3 +228,230 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>>           vmemmap_buf_end = NULL;
>>       }
>>   }
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +
>> +#define PAGE_INUSE 0xFD
>> +
>> +static void vmemmap_free_pages(struct page *page, int order)
>> +{
>> +    struct zone *zone;
>> +    unsigned long magic;
>> +
>> +    magic = (unsigned long) page->lru.next;
>> +    if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
>> +        put_page_bootmem(page);
>> +
>> +        zone = page_zone(page);
>> +        zone_span_writelock(zone);
>> +        zone->present_pages++;
>> +        zone_span_writeunlock(zone);
>> +        totalram_pages++;
> 
> Seems that we have different ways to handle pages allocated by bootmem
> or by regular allocator. Is the checking way in [PATCH 09/12] available
> here ?
> 
> +    /* bootmem page has reserved flag */
> +    if (PageReserved(page)) {
> ......
> +    }
> 
> If so, I think we can just merge these two functions.

Hmm, direct mapping table isn't allocated by bootmem allocator such as memblock, can't be free by put_page_bootmem().
But I will try to merge these two functions.

> 
>> +    } else
>> +        free_pages((unsigned long)page_address(page), order);
>> +}
>> +
>> +static void free_pte_table(pmd_t *pmd)
>> +{
>> +    pte_t *pte, *pte_start;
>> +    int i;
>> +
>> +    pte_start = (pte_t *)pmd_page_vaddr(*pmd);
>> +    for (i = 0; i<  PTRS_PER_PTE; i++) {
>> +        pte = pte_start + i;
>> +        if (pte_val(*pte))
>> +            return;
>> +    }
>> +
>> +    /* free a pte talbe */
>> +    vmemmap_free_pages(pmd_page(*pmd), 0);
>> +    spin_lock(&init_mm.page_table_lock);
>> +    pmd_clear(pmd);
>> +    spin_unlock(&init_mm.page_table_lock);
>> +}
>> +
>> +static void free_pmd_table(pud_t *pud)
>> +{
>> +    pmd_t *pmd, *pmd_start;
>> +    int i;
>> +
>> +    pmd_start = (pmd_t *)pud_page_vaddr(*pud);
>> +    for (i = 0; i<  PTRS_PER_PMD; i++) {
>> +        pmd = pmd_start + i;
>> +        if (pmd_val(*pmd))
>> +            return;
>> +    }
>> +
>> +    /* free a pmd talbe */
>> +    vmemmap_free_pages(pud_page(*pud), 0);
>> +    spin_lock(&init_mm.page_table_lock);
>> +    pud_clear(pud);
>> +    spin_unlock(&init_mm.page_table_lock);
>> +}
>> +
>> +static void free_pud_table(pgd_t *pgd)
>> +{
>> +    pud_t *pud, *pud_start;
>> +    int i;
>> +
>> +    pud_start = (pud_t *)pgd_page_vaddr(*pgd);
>> +    for (i = 0; i<  PTRS_PER_PUD; i++) {
>> +        pud = pud_start + i;
>> +        if (pud_val(*pud))
>> +            return;
>> +    }
>> +
>> +    /* free a pud table */
>> +    vmemmap_free_pages(pgd_page(*pgd), 0);
>> +    spin_lock(&init_mm.page_table_lock);
>> +    pgd_clear(pgd);
>> +    spin_unlock(&init_mm.page_table_lock);
>> +}
> 
> All the free_xxx_table() are very similar to the functions in
> [PATCH 09/12]. Could we reuse them anyway ?

yes, we can reuse them.

> 
>> +
>> +static int split_large_page(pte_t *kpte, unsigned long address, pte_t *pbase)
>> +{
>> +    struct page *page = pmd_page(*(pmd_t *)kpte);
>> +    int i = 0;
>> +    unsigned long magic;
>> +    unsigned long section_nr;
>> +
>> +    __split_large_page(kpte, address, pbase);
> 
> Is this patch going to replace [PATCH 08/12] ?
> 

I wish to replace [PATCH 08/12], but need Congyang and Yasuaki to confirm first:)

> If so, __split_large_page() was added and exported in [PATCH 09/12],
> then we should move it here, right ?

yes.

and what do you think about moving vmemmap_pud[pmd/pte]_remove() to arch/x86/mm/init_64.c,
to be consistent with vmemmap_populate() ?

I will rework [PATCH 08/12] and [PATCH 09/12] soon.

Thanks,
Jianguo Wu.

> 
> If not, free_map_bootmem() and __kfree_section_memmap() were changed in
> [PATCH 08/12], and we need to handle this.
> 
>> +    __flush_tlb_all();
>> +
>> +    magic = (unsigned long) page->lru.next;
>> +    if (magic == SECTION_INFO) {
>> +        section_nr = pfn_to_section_nr(page_to_pfn(page));
>> +        while (i<  PTRS_PER_PMD) {
>> +            page++;
>> +            i++;
>> +            get_page_bootmem(section_nr, page, SECTION_INFO);
>> +        }
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static void vmemmap_pte_remove(pmd_t *pmd, unsigned long addr, unsigned long end)
>> +{
>> +    pte_t *pte;
>> +    unsigned long next;
>> +    void *page_addr;
>> +
>> +    pte = pte_offset_kernel(pmd, addr);
>> +    for (; addr<  end; pte++, addr += PAGE_SIZE) {
>> +        next = (addr + PAGE_SIZE)&  PAGE_MASK;
>> +        if (next>  end)
>> +            next = end;
>> +
>> +        if (pte_none(*pte))
>> +            continue;
>> +        if (IS_ALIGNED(addr, PAGE_SIZE)&&
>> +            IS_ALIGNED(next, PAGE_SIZE)) {
>> +            vmemmap_free_pages(pte_page(*pte), 0);
>> +            spin_lock(&init_mm.page_table_lock);
>> +            pte_clear(&init_mm, addr, pte);
>> +            spin_unlock(&init_mm.page_table_lock);
>> +        } else {
>> +            /*
>> +             * Removed page structs are filled with 0xFD.
>> +             */
>> +            memset((void *)addr, PAGE_INUSE, next - addr);
>> +            page_addr = page_address(pte_page(*pte));
>> +
>> +            if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
>> +                spin_lock(&init_mm.page_table_lock);
>> +                pte_clear(&init_mm, addr, pte);
>> +                spin_unlock(&init_mm.page_table_lock);
>> +            }
>> +        }
>> +    }
>> +
>> +    free_pte_table(pmd);
>> +    __flush_tlb_all();
>> +}
>> +
>> +static void vmemmap_pmd_remove(pud_t *pud, unsigned long addr, unsigned long end)
>> +{
>> +    unsigned long next;
>> +    pmd_t *pmd;
>> +
>> +    pmd = pmd_offset(pud, addr);
>> +    for (; addr<  end; addr = next, pmd++) {
>> +        next = pmd_addr_end(addr, end);
>> +        if (pmd_none(*pmd))
>> +            continue;
>> +
>> +        if (cpu_has_pse) {
>> +            unsigned long pte_base;
>> +
>> +            if (IS_ALIGNED(addr, PMD_SIZE)&&
>> +                IS_ALIGNED(next, PMD_SIZE)) {
>> +                vmemmap_free_pages(pmd_page(*pmd),
>> +                           get_order(PMD_SIZE));
>> +                spin_lock(&init_mm.page_table_lock);
>> +                pmd_clear(pmd);
>> +                spin_unlock(&init_mm.page_table_lock);
>> +                continue;
>> +            }
>> +
>> +            /*
>> +             * We use 2M page, but we need to remove part of them,
>> +             * so split 2M page to 4K page.
>> +             */
>> +            pte_base = get_zeroed_page(GFP_ATOMIC | __GFP_NOTRACK);
>> +            if (!pte_base) {
>> +                WARN_ON(1);
>> +                continue;
>> +            }
>> +
>> +            split_large_page((pte_t *)pmd, addr, (pte_t *)pte_base);
>> +            __flush_tlb_all();
>> +
>> +            spin_lock(&init_mm.page_table_lock);
>> +            pmd_populate_kernel(&init_mm, pmd, (pte_t *)pte_base);
>> +            spin_unlock(&init_mm.page_table_lock);
>> +        }
>> +
>> +        vmemmap_pte_remove(pmd, addr, next);
>> +    }
>> +
>> +    free_pmd_table(pud);
>> +    __flush_tlb_all();
>> +}
>> +
>> +static void vmemmap_pud_remove(pgd_t *pgd, unsigned long addr, unsigned long end)
>> +{
>> +    unsigned long next;
>> +    pud_t *pud;
>> +
>> +    pud = pud_offset(pgd, addr);
>> +    for (; addr<  end; addr = next, pud++) {
>> +        next = pud_addr_end(addr, end);
>> +        if (pud_none(*pud))
>> +            continue;
>> +
>> +        vmemmap_pmd_remove(pud, addr, next);
>> +    }
>> +
>> +    free_pud_table(pgd);
>> +    __flush_tlb_all();
>> +}
>> +
>> +void vmemmap_free(struct page *memmap, unsigned long nr_pages)
>> +{
>> +    unsigned long addr = (unsigned long)memmap;
>> +    unsigned long end = (unsigned long)(memmap + nr_pages);
>> +    unsigned long next;
>> +
>> +    for (; addr<  end; addr = next) {
>> +        pgd_t *pgd = pgd_offset_k(addr);
>> +
>> +        next = pgd_addr_end(addr, end);
>> +        if (!pgd_present(*pgd))
>> +            continue;
>> +
>> +        vmemmap_pud_remove(pgd, addr, next);
>> +        sync_global_pgds(addr, next - 1);
>> +    }
>> +}
>> +#endif
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index fac95f2..4060229 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -615,10 +615,11 @@ static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
>>   }
>>   static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
>>   {
>> -    return; /* XXX: Not implemented yet */
>> +    vmemmap_free(memmap, nr_pages);
>>   }
>>   static void free_map_bootmem(struct page *page, unsigned long nr_pages)
> 
> In the latest kernel, this line was:
> static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
> 
>>   {
>> +    vmemmap_free(page, nr_pages);
>>   }
>>   #else
>>   static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
> 
> 
> .
>
Tang Chen - Dec. 5, 2012, 2:07 a.m.
Hi Wu,

On 12/04/2012 08:20 PM, Jianguo Wu wrote:
(snip)
>>
>> Seems that we have different ways to handle pages allocated by bootmem
>> or by regular allocator. Is the checking way in [PATCH 09/12] available
>> here ?
>>
>> +    /* bootmem page has reserved flag */
>> +    if (PageReserved(page)) {
>> ......
>> +    }
>>
>> If so, I think we can just merge these two functions.
>
> Hmm, direct mapping table isn't allocated by bootmem allocator such as memblock, can't be free by put_page_bootmem().
> But I will try to merge these two functions.
>

Oh, I didn't notice this, thanks. :)

(snip)

>>> +
>>> +    __split_large_page(kpte, address, pbase);
>>
>> Is this patch going to replace [PATCH 08/12] ?
>>
>
> I wish to replace [PATCH 08/12], but need Congyang and Yasuaki to confirm first:)
>
>> If so, __split_large_page() was added and exported in [PATCH 09/12],
>> then we should move it here, right ?
>
> yes.
>
> and what do you think about moving vmemmap_pud[pmd/pte]_remove() to arch/x86/mm/init_64.c,
> to be consistent with vmemmap_populate() ?

It is a good idea since pud/pmd/pte related code could be platform
dependent. And I'm also trying to move vmemmap_free() to
arch/x86/mm/init_64.c too. I want to have a common interface just
like vmemmap_populate(). :)

>
> I will rework [PATCH 08/12] and [PATCH 09/12] soon.

I am rebasing the whole patch set now. And I think I chould finish part
of your work too. A new patch-set is coming soon, and your rework is
also welcome. :)

Thanks. :)
Jianguo Wu - Dec. 5, 2012, 3:23 a.m.
Hi Tang,

On 2012/12/5 10:07, Tang Chen wrote:

> Hi Wu,
> 
> On 12/04/2012 08:20 PM, Jianguo Wu wrote:
> (snip)
>>>
>>> Seems that we have different ways to handle pages allocated by bootmem
>>> or by regular allocator. Is the checking way in [PATCH 09/12] available
>>> here ?
>>>
>>> +    /* bootmem page has reserved flag */
>>> +    if (PageReserved(page)) {
>>> ......
>>> +    }
>>>
>>> If so, I think we can just merge these two functions.
>>
>> Hmm, direct mapping table isn't allocated by bootmem allocator such as memblock, can't be free by put_page_bootmem().
>> But I will try to merge these two functions.
>>
> 
> Oh, I didn't notice this, thanks. :)
> 
> (snip)
> 
>>>> +
>>>> +    __split_large_page(kpte, address, pbase);
>>>
>>> Is this patch going to replace [PATCH 08/12] ?
>>>
>>
>> I wish to replace [PATCH 08/12], but need Congyang and Yasuaki to confirm first:)
>>
>>> If so, __split_large_page() was added and exported in [PATCH 09/12],
>>> then we should move it here, right ?
>>
>> yes.
>>
>> and what do you think about moving vmemmap_pud[pmd/pte]_remove() to arch/x86/mm/init_64.c,
>> to be consistent with vmemmap_populate() ?
> 
> It is a good idea since pud/pmd/pte related code could be platform
> dependent. And I'm also trying to move vmemmap_free() to
> arch/x86/mm/init_64.c too. I want to have a common interface just
> like vmemmap_populate(). :)
> 

Great.

>>
>> I will rework [PATCH 08/12] and [PATCH 09/12] soon.
> 
> I am rebasing the whole patch set now. And I think I chould finish part
> of your work too. A new patch-set is coming soon, and your rework is
> also welcome. :)
>

Since you are rebasing now, I will wait for your new patche-set :).

Thanks.
Jianguo Wu

> Thanks. :)
> 
> 
> 
> .
>
Tang Chen - Dec. 7, 2012, 1:42 a.m.
Hi Wu,

I met some problems when I was digging into the code. It's very
kind of you if you could help me with that. :)

If I misunderstood your code, please tell me.
Please see below. :)

On 12/03/2012 10:23 AM, Jianguo Wu wrote:
> Signed-off-by: Jianguo Wu<wujianguo@huawei.com>
> Signed-off-by: Jiang Liu<jiang.liu@huawei.com>
> ---
>   include/linux/mm.h  |    1 +
>   mm/sparse-vmemmap.c |  231 +++++++++++++++++++++++++++++++++++++++++++++++++++
>   mm/sparse.c         |    3 +-
>   3 files changed, 234 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5657670..1f26af5 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1642,6 +1642,7 @@ 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_free(struct page *memmap, unsigned long nr_pages);
>
>   enum mf_flags {
>   	MF_COUNT_INCREASED = 1<<  0,
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 1b7e22a..748732d 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -29,6 +29,10 @@
>   #include<asm/pgalloc.h>
>   #include<asm/pgtable.h>
>
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +#include<asm/tlbflush.h>
> +#endif
> +
>   /*
>    * Allocate a block of memory to be used to back the virtual memory map
>    * or to back the page tables that are used to create the mapping.
> @@ -224,3 +228,230 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>   		vmemmap_buf_end = NULL;
>   	}
>   }
> +
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +
> +#define PAGE_INUSE 0xFD
> +
> +static void vmemmap_free_pages(struct page *page, int order)
> +{
> +	struct zone *zone;
> +	unsigned long magic;
> +
> +	magic = (unsigned long) page->lru.next;
> +	if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
> +		put_page_bootmem(page);
> +
> +		zone = page_zone(page);
> +		zone_span_writelock(zone);
> +		zone->present_pages++;
> +		zone_span_writeunlock(zone);
> +		totalram_pages++;
> +	} else
> +		free_pages((unsigned long)page_address(page), order);

Here, I think SECTION_INFO and MIX_SECTION_INFO pages are all allocated
by bootmem, so I put this function this way.

I'm not sure if parameter order is necessary here. It will always be 0
in your code. Is this OK to you ?

static void free_pagetable(struct page *page)
{
         struct zone *zone;
         bool bootmem = false;
         unsigned long magic;

         /* bootmem page has reserved flag */
         if (PageReserved(page)) {
                 __ClearPageReserved(page);
                 bootmem = true;
         }

         magic = (unsigned long) page->lru.next;
         if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
                 put_page_bootmem(page);
         else
                 __free_page(page);

         /*
          * SECTION_INFO pages and MIX_SECTION_INFO pages
          * are all allocated by bootmem.
          */
         if (bootmem) {
                 zone = page_zone(page);
                 zone_span_writelock(zone);
                 zone->present_pages++;
                 zone_span_writeunlock(zone);
                 totalram_pages++;
         }
}

(snip)

> +
> +static void vmemmap_pte_remove(pmd_t *pmd, unsigned long addr, unsigned long end)
> +{
> +	pte_t *pte;
> +	unsigned long next;
> +	void *page_addr;
> +
> +	pte = pte_offset_kernel(pmd, addr);
> +	for (; addr<  end; pte++, addr += PAGE_SIZE) {
> +		next = (addr + PAGE_SIZE)&  PAGE_MASK;
> +		if (next>  end)
> +			next = end;
> +
> +		if (pte_none(*pte))

Here, you checked xxx_none() in your vmemmap_xxx_remove(), but you used
!xxx_present() in your x86_64 patches. Is it OK if I only check
!xxx_present() ?

> +			continue;
> +		if (IS_ALIGNED(addr, PAGE_SIZE)&&
> +		    IS_ALIGNED(next, PAGE_SIZE)) {
> +			vmemmap_free_pages(pte_page(*pte), 0);
> +			spin_lock(&init_mm.page_table_lock);
> +			pte_clear(&init_mm, addr, pte);
> +			spin_unlock(&init_mm.page_table_lock);
> +		} else {
> +			/*
> +			 * Removed page structs are filled with 0xFD.
> +			 */
> +			memset((void *)addr, PAGE_INUSE, next - addr);
> +			page_addr = page_address(pte_page(*pte));
> +
> +			if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
> +				spin_lock(&init_mm.page_table_lock);
> +				pte_clear(&init_mm, addr, pte);
> +				spin_unlock(&init_mm.page_table_lock);

Here, since we clear pte, we should also free the page, right ?

> +			}
> +		}
> +	}
> +
> +	free_pte_table(pmd);
> +	__flush_tlb_all();
> +}
> +
> +static void vmemmap_pmd_remove(pud_t *pud, unsigned long addr, unsigned long end)
> +{
> +	unsigned long next;
> +	pmd_t *pmd;
> +
> +	pmd = pmd_offset(pud, addr);
> +	for (; addr<  end; addr = next, pmd++) {
> +		next = (addr, end);

And by the way, there isn't pte_addr_end() in kernel, why ?
I saw you calculated it like this:

                 next = (addr + PAGE_SIZE) & PAGE_MASK;
                 if (next > end)
                         next = end;

This logic is very similar to {pmd|pud|pgd}_addr_end(). Shall we add a
pte_addr_end() or something ? :)
Since there is no such code in kernel for a long time, I think there
must be some reasons.

I merged free_xxx_table() and remove_xxx_table() as common interfaces.

And again, thanks for your patient and nice explanation. :)

(snip)
Jianguo Wu - Dec. 7, 2012, 2:20 a.m.
Hi Tang,

On 2012/12/7 9:42, Tang Chen wrote:

> Hi Wu,
> 
> I met some problems when I was digging into the code. It's very
> kind of you if you could help me with that. :)
> 
> If I misunderstood your code, please tell me.
> Please see below. :)
> 
> On 12/03/2012 10:23 AM, Jianguo Wu wrote:
>> Signed-off-by: Jianguo Wu<wujianguo@huawei.com>
>> Signed-off-by: Jiang Liu<jiang.liu@huawei.com>
>> ---
>>   include/linux/mm.h  |    1 +
>>   mm/sparse-vmemmap.c |  231 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>   mm/sparse.c         |    3 +-
>>   3 files changed, 234 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 5657670..1f26af5 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1642,6 +1642,7 @@ 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_free(struct page *memmap, unsigned long nr_pages);
>>
>>   enum mf_flags {
>>       MF_COUNT_INCREASED = 1<<  0,
>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>> index 1b7e22a..748732d 100644
>> --- a/mm/sparse-vmemmap.c
>> +++ b/mm/sparse-vmemmap.c
>> @@ -29,6 +29,10 @@
>>   #include<asm/pgalloc.h>
>>   #include<asm/pgtable.h>
>>
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +#include<asm/tlbflush.h>
>> +#endif
>> +
>>   /*
>>    * Allocate a block of memory to be used to back the virtual memory map
>>    * or to back the page tables that are used to create the mapping.
>> @@ -224,3 +228,230 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
>>           vmemmap_buf_end = NULL;
>>       }
>>   }
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +
>> +#define PAGE_INUSE 0xFD
>> +
>> +static void vmemmap_free_pages(struct page *page, int order)
>> +{
>> +    struct zone *zone;
>> +    unsigned long magic;
>> +
>> +    magic = (unsigned long) page->lru.next;
>> +    if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
>> +        put_page_bootmem(page);
>> +
>> +        zone = page_zone(page);
>> +        zone_span_writelock(zone);
>> +        zone->present_pages++;
>> +        zone_span_writeunlock(zone);
>> +        totalram_pages++;
>> +    } else
>> +        free_pages((unsigned long)page_address(page), order);
> 
> Here, I think SECTION_INFO and MIX_SECTION_INFO pages are all allocated
> by bootmem, so I put this function this way.
> 
> I'm not sure if parameter order is necessary here. It will always be 0
> in your code. Is this OK to you ?
> 

parameter order is necessary in cpu_has_pse case:
	vmemmap_pmd_remove
		free_pagetable(pmd_page(*pmd), get_order(PMD_SIZE))

> static void free_pagetable(struct page *page)
> {
>         struct zone *zone;
>         bool bootmem = false;
>         unsigned long magic;
> 
>         /* bootmem page has reserved flag */
>         if (PageReserved(page)) {
>                 __ClearPageReserved(page);
>                 bootmem = true;
>         }
> 
>         magic = (unsigned long) page->lru.next;
>         if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
>                 put_page_bootmem(page);
>         else
>                 __free_page(page);
> 
>         /*
>          * SECTION_INFO pages and MIX_SECTION_INFO pages
>          * are all allocated by bootmem.
>          */
>         if (bootmem) {
>                 zone = page_zone(page);
>                 zone_span_writelock(zone);
>                 zone->present_pages++;
>                 zone_span_writeunlock(zone);
>                 totalram_pages++;
>         }
> }
> 
> (snip)
> 
>> +
>> +static void vmemmap_pte_remove(pmd_t *pmd, unsigned long addr, unsigned long end)
>> +{
>> +    pte_t *pte;
>> +    unsigned long next;
>> +    void *page_addr;
>> +
>> +    pte = pte_offset_kernel(pmd, addr);
>> +    for (; addr<  end; pte++, addr += PAGE_SIZE) {
>> +        next = (addr + PAGE_SIZE)&  PAGE_MASK;
>> +        if (next>  end)
>> +            next = end;
>> +
>> +        if (pte_none(*pte))
> 
> Here, you checked xxx_none() in your vmemmap_xxx_remove(), but you used
> !xxx_present() in your x86_64 patches. Is it OK if I only check
> !xxx_present() ?

It is Ok.

> 
>> +            continue;
>> +        if (IS_ALIGNED(addr, PAGE_SIZE)&&
>> +            IS_ALIGNED(next, PAGE_SIZE)) {
>> +            vmemmap_free_pages(pte_page(*pte), 0);
>> +            spin_lock(&init_mm.page_table_lock);
>> +            pte_clear(&init_mm, addr, pte);
>> +            spin_unlock(&init_mm.page_table_lock);
>> +        } else {
>> +            /*
>> +             * Removed page structs are filled with 0xFD.
>> +             */
>> +            memset((void *)addr, PAGE_INUSE, next - addr);
>> +            page_addr = page_address(pte_page(*pte));
>> +
>> +            if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
>> +                spin_lock(&init_mm.page_table_lock);
>> +                pte_clear(&init_mm, addr, pte);
>> +                spin_unlock(&init_mm.page_table_lock);
> 
> Here, since we clear pte, we should also free the page, right ?
> 

Right, I forgot here, sorry.

>> +            }
>> +        }
>> +    }
>> +
>> +    free_pte_table(pmd);
>> +    __flush_tlb_all();
>> +}
>> +
>> +static void vmemmap_pmd_remove(pud_t *pud, unsigned long addr, unsigned long end)
>> +{
>> +    unsigned long next;
>> +    pmd_t *pmd;
>> +
>> +    pmd = pmd_offset(pud, addr);
>> +    for (; addr<  end; addr = next, pmd++) {
>> +        next = (addr, end);
> 
> And by the way, there isn't pte_addr_end() in kernel, why ?
> I saw you calculated it like this:
> 
>                 next = (addr + PAGE_SIZE) & PAGE_MASK;
>                 if (next > end)
>                         next = end;
> 
> This logic is very similar to {pmd|pud|pgd}_addr_end(). Shall we add a
> pte_addr_end() or something ? :)

Maybe just keep this for now if no other place need pte_addr_end()?

> Since there is no such code in kernel for a long time, I think there
> must be some reasons.

Maybe in current kernel, doesn't deal not PTE_SIZE alignment address´╝č
 

> 
> I merged free_xxx_table() and remove_xxx_table() as common interfaces.

Greate!

Thanks for your work:).

> 
> And again, thanks for your patient and nice explanation. :)
> 
> (snip)
> 
> .
>

Patch

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5657670..1f26af5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1642,6 +1642,7 @@  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_free(struct page *memmap, unsigned long nr_pages);
 
 enum mf_flags {
 	MF_COUNT_INCREASED = 1 << 0,
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 1b7e22a..748732d 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -29,6 +29,10 @@ 
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
 
+#ifdef CONFIG_MEMORY_HOTREMOVE
+#include <asm/tlbflush.h>
+#endif
+
 /*
  * Allocate a block of memory to be used to back the virtual memory map
  * or to back the page tables that are used to create the mapping.
@@ -224,3 +228,230 @@  void __init sparse_mem_maps_populate_node(struct page **map_map,
 		vmemmap_buf_end = NULL;
 	}
 }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+
+#define PAGE_INUSE 0xFD
+
+static void vmemmap_free_pages(struct page *page, int order)
+{
+	struct zone *zone;
+	unsigned long magic;
+
+	magic = (unsigned long) page->lru.next;
+	if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
+		put_page_bootmem(page);
+
+		zone = page_zone(page);
+		zone_span_writelock(zone);
+		zone->present_pages++;
+		zone_span_writeunlock(zone);
+		totalram_pages++;
+	} else
+		free_pages((unsigned long)page_address(page), order);
+}
+
+static void free_pte_table(pmd_t *pmd)
+{
+	pte_t *pte, *pte_start;
+	int i;
+
+	pte_start = (pte_t *)pmd_page_vaddr(*pmd);
+	for (i = 0; i < PTRS_PER_PTE; i++) {
+		pte = pte_start + i;
+		if (pte_val(*pte))
+			return;
+	}
+
+	/* free a pte talbe */
+	vmemmap_free_pages(pmd_page(*pmd), 0);
+	spin_lock(&init_mm.page_table_lock);
+	pmd_clear(pmd);
+	spin_unlock(&init_mm.page_table_lock);
+}
+
+static void free_pmd_table(pud_t *pud)
+{
+	pmd_t *pmd, *pmd_start;
+	int i;
+
+	pmd_start = (pmd_t *)pud_page_vaddr(*pud);
+	for (i = 0; i < PTRS_PER_PMD; i++) {
+		pmd = pmd_start + i;
+		if (pmd_val(*pmd))
+			return;
+	}
+
+	/* free a pmd talbe */
+	vmemmap_free_pages(pud_page(*pud), 0);
+	spin_lock(&init_mm.page_table_lock);
+	pud_clear(pud);
+	spin_unlock(&init_mm.page_table_lock);
+}
+
+static void free_pud_table(pgd_t *pgd)
+{
+	pud_t *pud, *pud_start;
+	int i;
+
+	pud_start = (pud_t *)pgd_page_vaddr(*pgd);
+	for (i = 0; i < PTRS_PER_PUD; i++) {
+		pud = pud_start + i;
+		if (pud_val(*pud))
+			return;
+	}
+
+	/* free a pud table */
+	vmemmap_free_pages(pgd_page(*pgd), 0);
+	spin_lock(&init_mm.page_table_lock);
+	pgd_clear(pgd);
+	spin_unlock(&init_mm.page_table_lock);
+}
+
+static int split_large_page(pte_t *kpte, unsigned long address, pte_t *pbase)
+{
+	struct page *page = pmd_page(*(pmd_t *)kpte);
+	int i = 0;
+	unsigned long magic;
+	unsigned long section_nr;
+
+	__split_large_page(kpte, address, pbase);
+	__flush_tlb_all();
+
+	magic = (unsigned long) page->lru.next;
+	if (magic == SECTION_INFO) {
+		section_nr = pfn_to_section_nr(page_to_pfn(page));
+		while (i < PTRS_PER_PMD) {
+			page++;
+			i++;
+			get_page_bootmem(section_nr, page, SECTION_INFO);
+		}
+	}
+
+	return 0;
+}
+
+static void vmemmap_pte_remove(pmd_t *pmd, unsigned long addr, unsigned long end)
+{
+	pte_t *pte;
+	unsigned long next;
+	void *page_addr;
+
+	pte = pte_offset_kernel(pmd, addr);
+	for (; addr < end; pte++, addr += PAGE_SIZE) {
+		next = (addr + PAGE_SIZE) & PAGE_MASK;
+		if (next > end)
+			next = end;
+
+		if (pte_none(*pte))
+			continue;
+		if (IS_ALIGNED(addr, PAGE_SIZE) &&
+		    IS_ALIGNED(next, PAGE_SIZE)) {
+			vmemmap_free_pages(pte_page(*pte), 0);
+			spin_lock(&init_mm.page_table_lock);
+			pte_clear(&init_mm, addr, pte);
+			spin_unlock(&init_mm.page_table_lock);
+		} else {
+			/*
+			 * Removed page structs are filled with 0xFD.
+			 */
+			memset((void *)addr, PAGE_INUSE, next - addr);
+			page_addr = page_address(pte_page(*pte));
+
+			if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
+				spin_lock(&init_mm.page_table_lock);
+				pte_clear(&init_mm, addr, pte);
+				spin_unlock(&init_mm.page_table_lock);
+			}
+		}
+	}
+
+	free_pte_table(pmd);
+	__flush_tlb_all();
+}
+
+static void vmemmap_pmd_remove(pud_t *pud, unsigned long addr, unsigned long end)
+{
+	unsigned long next;
+	pmd_t *pmd;
+
+	pmd = pmd_offset(pud, addr);
+	for (; addr < end; addr = next, pmd++) {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none(*pmd))
+			continue;
+
+		if (cpu_has_pse) {
+			unsigned long pte_base;
+
+			if (IS_ALIGNED(addr, PMD_SIZE) &&
+			    IS_ALIGNED(next, PMD_SIZE)) {
+				vmemmap_free_pages(pmd_page(*pmd),
+						   get_order(PMD_SIZE));
+				spin_lock(&init_mm.page_table_lock);
+				pmd_clear(pmd);
+				spin_unlock(&init_mm.page_table_lock);
+				continue;
+			}
+
+			/*
+			 * We use 2M page, but we need to remove part of them,
+			 * so split 2M page to 4K page.
+			 */
+			pte_base = get_zeroed_page(GFP_ATOMIC | __GFP_NOTRACK);
+			if (!pte_base) {
+				WARN_ON(1);
+				continue;
+			}
+
+			split_large_page((pte_t *)pmd, addr, (pte_t *)pte_base);
+			__flush_tlb_all();
+
+			spin_lock(&init_mm.page_table_lock);
+			pmd_populate_kernel(&init_mm, pmd, (pte_t *)pte_base);
+			spin_unlock(&init_mm.page_table_lock);
+		}
+
+		vmemmap_pte_remove(pmd, addr, next);
+	}
+
+	free_pmd_table(pud);
+	__flush_tlb_all();
+}
+
+static void vmemmap_pud_remove(pgd_t *pgd, unsigned long addr, unsigned long end)
+{
+	unsigned long next;
+	pud_t *pud;
+
+	pud = pud_offset(pgd, addr);
+	for (; addr < end; addr = next, pud++) {
+		next = pud_addr_end(addr, end);
+		if (pud_none(*pud))
+			continue;
+
+		vmemmap_pmd_remove(pud, addr, next);
+	}
+
+	free_pud_table(pgd);
+	__flush_tlb_all();
+}
+
+void vmemmap_free(struct page *memmap, unsigned long nr_pages)
+{
+	unsigned long addr = (unsigned long)memmap;
+	unsigned long end = (unsigned long)(memmap + nr_pages);
+	unsigned long next;
+
+	for (; addr < end; addr = next) {
+		pgd_t *pgd = pgd_offset_k(addr);
+
+		next = pgd_addr_end(addr, end);
+		if (!pgd_present(*pgd))
+			continue;
+
+		vmemmap_pud_remove(pgd, addr, next);
+		sync_global_pgds(addr, next - 1);
+	}
+}
+#endif
diff --git a/mm/sparse.c b/mm/sparse.c
index fac95f2..4060229 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -615,10 +615,11 @@  static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
 }
 static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
 {
-	return; /* XXX: Not implemented yet */
+	vmemmap_free(memmap, nr_pages);
 }
 static void free_map_bootmem(struct page *page, unsigned long nr_pages)
 {
+	vmemmap_free(page, nr_pages);
 }
 #else
 static struct page *__kmalloc_section_memmap(unsigned long nr_pages)