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

Wen Congyang
2012-11-30T01:45:21Z

At 11/28/2012 05:40 PM, Jianguo Wu Wrote:
> Hi Congyang,
>
> I think vmemmap's pgtable pages should be freed after all entries are cleared, I have a patch to do this.
> The code logic is the same as [Patch v4 09/12] memory-hotplug: remove page table of x86_64 architecture.
>
> How do you think about this?
>
> 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 | 214 +++++++++++++++++++++++++++++++++++++++++++++++++++
> mm/sparse.c | 5 +-
> 3 files changed, 218 insertions(+), 2 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..242cb28 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 +228,213 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> vmemmap_buf_end = NULL;
> }
> }
> +
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +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 {
> + if (is_vmalloc_addr(page_address(page)))
> + vfree(page_address(page));

Hmm, vmemmap doesn't use vmalloc() to allocate memory.

> + 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;
> +
> + 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(end, 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);

If addr or end is not alianed with PAGE_SIZE, you may leak some
memory.

> + }
> + }
> +
> + 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);

get_zeored_page() may fail. You should handle this error.

> + 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);

The parameter for sync_global_pgds() is [start, end], not
[start, end)

> + }
> +}
> +#endif
> diff --git a/mm/sparse.c b/mm/sparse.c
> index fac95f2..3a16d68 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)
Why do you change this line?

> {
> - return; /* XXX: Not implemented yet */
> + vmemmap_free(page, 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)