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

Tang Chen
2012-12-04T09:13:27Z

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)