Re: [Patch v4 08/12] memory-hotplug: remove memmap of sparse-vmemmap

Jianguo Wu
2012-12-04T12:20:18Z

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)
>
>
> .
>