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

Jianguo Wu
2012-11-28T09:40:16Z

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));
+ 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);
+ }
+ }
+
+ 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);
+ 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);
+ }
+}
+#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)
{
- 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)
--
1.7.6.1

On 2012/11/27 18:00, 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>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
> Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
> Signed-off-by: Wen Congyang <wency@cn.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 | 19 ++++----
> 8 files changed, 165 insertions(+), 24 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 5657670..94d5ccd 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 ccc11b6..7797e91 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -301,19 +301,6 @@ 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;
> @@ -330,9 +317,9 @@ 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..c723bc2 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)
> +static void free_map_bootmem(struct page *page)
> {
> + vmemmap_free_bootmem(page, PAGES_PER_SECTION);
> }
> #else
> static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
> @@ -658,10 +659,14 @@ static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
> get_order(sizeof(struct page) * nr_pages));
> }
>
> -static void free_map_bootmem(struct page *page, unsigned long nr_pages)
> +static void free_map_bootmem(struct page *page)
> {
> unsigned long maps_section_nr, removing_section_nr, i;
> unsigned long magic;
> + unsigned long nr_pages;
> +
> + nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
> + >> PAGE_SHIFT;
>
> for (i = 0; i < nr_pages; i++, page++) {
> magic = (unsigned long) page->lru.next;
> @@ -688,7 +693,6 @@ static void free_map_bootmem(struct page *page, unsigned long nr_pages)
> static void free_section_usemap(struct page *memmap, unsigned long *usemap)
> {
> struct page *usemap_page;
> - unsigned long nr_pages;
>
> if (!usemap)
> return;
> @@ -713,10 +717,7 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
> struct page *memmap_page;
> memmap_page = virt_to_page(memmap);
>
> - nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
> - >> PAGE_SHIFT;
> -
> - free_map_bootmem(memmap_page, nr_pages);
> + free_map_bootmem(memmap_page);
> }
> }
>