Re: [PATCH 8/10] memory-hotplug : remove page table of x86_64 architecture

Wen Congyang
2012-10-22T07:11:17Z

Hi, Wu

Sorry for late reply.

At 10/09/2012 04:26 PM, wujianguo Wrote:
> Hi Congyang,
> I think we should also free pages which are used by page tables after removing
> page tables of the memory.

It is OK to do it.

>
> From: Jianguo Wu <wujianguo@huawei.com>
>
> Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> ---
> arch/x86/mm/init_64.c | 110 +++++++++++++++++++++++++++++++++++++++---------
> 1 files changed, 89 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 5596dfa..81f9c3b 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -675,6 +675,74 @@ int arch_add_memory(int nid, u64 start, u64 size)
> }
> EXPORT_SYMBOL_GPL(arch_add_memory);
>
> +static inline void free_pagetable(struct page *page)
> +{
> + struct zone *zone;
> +
> + __ClearPageReserved(page);
> + __free_page(page);
> +
> + zone = page_zone(page);
> + zone_span_writelock(zone);
> + zone->present_pages++;
> + zone_span_writeunlock(zone);
> + totalram_pages++;

Why do you update zone and totalram_pages here?

> +}
> +
> +static void free_pte_table(pte_t *pte_start, pmd_t *pmd)
> +{
> + pte_t *pte;
> + int i;
> +
> + for (i = 0; i < PTRS_PER_PTE; i++) {
> + pte = pte_start + i;
> + if (pte_val(*pte))
> + break;
> + }
> +
> + /* free a pte talbe */
> + if (i == PTRS_PER_PTE) {
> + free_pagetable(pmd_page(*pmd));

The memory may be allocated at booting. So it is very dangerous to
free it without any check.

> + pmd_clear(pmd);
> + }
> +}
> +
> +static void free_pmd_table(pmd_t *pmd_start, pud_t *pud)
> +{
> + pmd_t *pmd;
> + int i;
> +
> + for (i = 0; i < PTRS_PER_PMD; i++) {
> + pmd = pmd_start + i;
> + if (pmd_val(*pmd))
> + break;
> + }
> +
> + /* free a pmd talbe */
> + if (i == PTRS_PER_PMD) {
> + free_pagetable(pud_page(*pud));
> + pud_clear(pud);
> + }
> +}
> +
> +static void free_pud_table(pud_t *pud_start, pgd_t *pgd)
> +{
> + pud_t *pud;
> + int i;
> +
> + for (i = 0; i < PTRS_PER_PUD; i++) {
> + pud = pud_start + i;
> + if (pud_val(*pud))
> + break;
> + }
> +
> + /* free a pud table */
> + if (i == PTRS_PER_PUD) {
> + free_pagetable(pgd_page(*pgd));
> + pgd_clear(pgd);
> + }
> +}
> +
> static void __meminit
> phys_pte_remove(pte_t *pte_page, unsigned long addr, unsigned long end)
> {
> @@ -704,21 +772,19 @@ phys_pmd_remove(pmd_t *pmd_page, unsigned long addr, unsigned long end)
> unsigned long pages = 0, next;
> int i = pmd_index(addr);
>
> - for (; i < PTRS_PER_PMD; i++, addr = next) {
> + for (; i < PTRS_PER_PMD && addr < end; i++, addr = next) {
> unsigned long pte_phys;
> pmd_t *pmd = pmd_page + pmd_index(addr);
> pte_t *pte;
>
> - if (addr >= end)
> - break;
> -
> - next = (addr & PMD_MASK) + PMD_SIZE;
> + next = pmd_addr_end(addr, end);
>
> if (!pmd_present(*pmd))
> continue;
>
> if (pmd_large(*pmd)) {
> - if ((addr & ~PMD_MASK) == 0 && next <= end) {
> + if (IS_ALIGNED(addr, PMD_SIZE) &&
> + IS_ALIGNED(next, PMD_SIZE)) {
> set_pmd(pmd, __pmd(0));
> pages++;
> continue;
> @@ -729,7 +795,8 @@ phys_pmd_remove(pmd_t *pmd_page, unsigned long addr, unsigned long end)
> * so split 2M page to 4K page.
> */
> pte = alloc_low_page(&pte_phys);
> - __split_large_page((pte_t *)pmd, addr, pte);
> + __split_large_page((pte_t *)pmd,
> + (unsigned long)__va(addr), pte);
>
> spin_lock(&init_mm.page_table_lock);
> pmd_populate_kernel(&init_mm, pmd, __va(pte_phys));
> @@ -738,7 +805,8 @@ phys_pmd_remove(pmd_t *pmd_page, unsigned long addr, unsigned long end)
>
> spin_lock(&init_mm.page_table_lock);
> pte = map_low_page((pte_t *)pmd_page_vaddr(*pmd));
> - phys_pte_remove(pte, addr, end);
> + phys_pte_remove(pte, addr, next);
> + free_pte_table(pte, pmd);
> unmap_low_page(pte);
> spin_unlock(&init_mm.page_table_lock);
> }
> @@ -751,21 +819,19 @@ phys_pud_remove(pud_t *pud_page, unsigned long addr, unsigned long end)
> unsigned long pages = 0, next;
> int i = pud_index(addr);
>
> - for (; i < PTRS_PER_PUD; i++, addr = next) {
> + for (; i < PTRS_PER_PUD && addr < end; i++, addr = next) {
> unsigned long pmd_phys;
> pud_t *pud = pud_page + pud_index(addr);
> pmd_t *pmd;
>
> - if (addr >= end)
> - break;
> -
> - next = (addr & PUD_MASK) + PUD_SIZE;
> + next = pud_addr_end(addr, end);
>
> if (!pud_present(*pud))
> continue;
>
> if (pud_large(*pud)) {
> - if ((addr & ~PUD_MASK) == 0 && next <= end) {
> + if (IS_ALIGNED(addr, PUD_SIZE) &&
> + IS_ALIGNED(next, PUD_SIZE)) {
> set_pud(pud, __pud(0));
> pages++;
> continue;
> @@ -776,15 +842,18 @@ phys_pud_remove(pud_t *pud_page, unsigned long addr, unsigned long end)
> * so split 1G page to 2M page.
> */
> pmd = alloc_low_page(&pmd_phys);
> - __split_large_page((pte_t *)pud, addr, (pte_t *)pmd);
> + __split_large_page((pte_t *)pud,
> + (unsigned long)__va(addr),
> + (pte_t *)pmd);
>
> spin_lock(&init_mm.page_table_lock);
> pud_populate(&init_mm, pud, __va(pmd_phys));
> spin_unlock(&init_mm.page_table_lock);
> }
>
> - pmd = map_low_page(pmd_offset(pud, 0));
> - phys_pmd_remove(pmd, addr, end);
> + pmd = map_low_page((pmd_t *)pud_page_vaddr(*pud));

Hmm, pmd_offset(pud, 0) is equal to (pmd_t *)pud_page_vaddr(*pud).

Is it OK to merge your patch into my patch?

Thanks
Wen Congyang

> + phys_pmd_remove(pmd, addr, next);
> + free_pmd_table(pmd, pud);
> unmap_low_page(pmd);
> __flush_tlb_all();
> }
> @@ -805,15 +874,14 @@ kernel_physical_mapping_remove(unsigned long start, unsigned long end)
> pgd_t *pgd = pgd_offset_k(start);
> pud_t *pud;
>
> - next = (start + PGDIR_SIZE) & PGDIR_MASK;
> - if (next > end)
> - next = end;
> + next = pgd_addr_end(start, end);
>
> if (!pgd_present(*pgd))
> continue;
>
> pud = map_low_page((pud_t *)pgd_page_vaddr(*pgd));
> - phys_pud_remove(pud, __pa(start), __pa(end));
> + phys_pud_remove(pud, __pa(start), __pa(next));
> + free_pud_table(pud, pgd);
> unmap_low_page(pud);
> }
>
> -- 1.7.6.1 .
>
>
> On 2012-10-5 10:36, Yasuaki Ishimatsu wrote:
>> From: Wen Congyang <wency@cn.fujitsu.com>
>>
>> For hot removing memory, we sholud remove page table about the memory.
>> So the patch searches a page table about the removed memory, and clear
>> page table.
>>
>> 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>
>> CC: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
>> ---
>> arch/x86/include/asm/pgtable_types.h | 1
>> arch/x86/mm/init_64.c | 147 +++++++++++++++++++++++++++++++++++
>> arch/x86/mm/pageattr.c | 47 +++++------
>> 3 files changed, 173 insertions(+), 22 deletions(-)
>>
>> Index: linux-3.6/arch/x86/mm/init_64.c
>> ===================================================================
>> --- linux-3.6.orig/arch/x86/mm/init_64.c 2012-10-04 18:30:21.171698416 +0900
>> +++ linux-3.6/arch/x86/mm/init_64.c 2012-10-04 18:30:27.317704652 +0900
>> @@ -675,6 +675,151 @@ int arch_add_memory(int nid, u64 start,
>> }
>> EXPORT_SYMBOL_GPL(arch_add_memory);
>>
>> +static void __meminit
>> +phys_pte_remove(pte_t *pte_page, unsigned long addr, unsigned long end)
>> +{
>> + unsigned pages = 0;
>> + int i = pte_index(addr);
>> +
>> + pte_t *pte = pte_page + pte_index(addr);
>> +
>> + for (; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE, pte++) {
>> +
>> + if (addr >= end)
>> + break;
>> +
>> + if (!pte_present(*pte))
>> + continue;
>> +
>> + pages++;
>> + set_pte(pte, __pte(0));
>> + }
>> +
>> + update_page_count(PG_LEVEL_4K, -pages);
>> +}
>> +
>> +static void __meminit
>> +phys_pmd_remove(pmd_t *pmd_page, unsigned long addr, unsigned long end)
>> +{
>> + unsigned long pages = 0, next;
>> + int i = pmd_index(addr);
>> +
>> + for (; i < PTRS_PER_PMD; i++, addr = next) {
>> + unsigned long pte_phys;
>> + pmd_t *pmd = pmd_page + pmd_index(addr);
>> + pte_t *pte;
>> +
>> + if (addr >= end)
>> + break;
>> +
>> + next = (addr & PMD_MASK) + PMD_SIZE;
>> +
>> + if (!pmd_present(*pmd))
>> + continue;
>> +
>> + if (pmd_large(*pmd)) {
>> + if ((addr & ~PMD_MASK) == 0 && next <= end) {
>> + set_pmd(pmd, __pmd(0));
>> + pages++;
>> + continue;
>> + }
>> +
>> + /*
>> + * We use 2M page, but we need to remove part of them,
>> + * so split 2M page to 4K page.
>> + */
>> + pte = alloc_low_page(&pte_phys);
>> + __split_large_page((pte_t *)pmd, addr, pte);
>> +
>> + spin_lock(&init_mm.page_table_lock);
>> + pmd_populate_kernel(&init_mm, pmd, __va(pte_phys));
>> + spin_unlock(&init_mm.page_table_lock);
>> + }
>> +
>> + spin_lock(&init_mm.page_table_lock);
>> + pte = map_low_page((pte_t *)pmd_page_vaddr(*pmd));
>> + phys_pte_remove(pte, addr, end);
>> + unmap_low_page(pte);
>> + spin_unlock(&init_mm.page_table_lock);
>> + }
>> + update_page_count(PG_LEVEL_2M, -pages);
>> +}
>> +
>> +static void __meminit
>> +phys_pud_remove(pud_t *pud_page, unsigned long addr, unsigned long end)
>> +{
>> + unsigned long pages = 0, next;
>> + int i = pud_index(addr);
>> +
>> + for (; i < PTRS_PER_PUD; i++, addr = next) {
>> + unsigned long pmd_phys;
>> + pud_t *pud = pud_page + pud_index(addr);
>> + pmd_t *pmd;
>> +
>> + if (addr >= end)
>> + break;
>> +
>> + next = (addr & PUD_MASK) + PUD_SIZE;
>> +
>> + if (!pud_present(*pud))
>> + continue;
>> +
>> + if (pud_large(*pud)) {
>> + if ((addr & ~PUD_MASK) == 0 && next <= end) {
>> + set_pud(pud, __pud(0));
>> + pages++;
>> + continue;
>> + }
>> +
>> + /*
>> + * We use 1G page, but we need to remove part of them,
>> + * so split 1G page to 2M page.
>> + */
>> + pmd = alloc_low_page(&pmd_phys);
>> + __split_large_page((pte_t *)pud, addr, (pte_t *)pmd);
>> +
>> + spin_lock(&init_mm.page_table_lock);
>> + pud_populate(&init_mm, pud, __va(pmd_phys));
>> + spin_unlock(&init_mm.page_table_lock);
>> + }
>> +
>> + pmd = map_low_page(pmd_offset(pud, 0));
>> + phys_pmd_remove(pmd, addr, end);
>> + unmap_low_page(pmd);
>> + __flush_tlb_all();
>> + }
>> + __flush_tlb_all();
>> +
>> + update_page_count(PG_LEVEL_1G, -pages);
>> +}
>> +
>> +void __meminit
>> +kernel_physical_mapping_remove(unsigned long start, unsigned long end)
>> +{
>> + unsigned long next;
>> +
>> + start = (unsigned long)__va(start);
>> + end = (unsigned long)__va(end);
>> +
>> + for (; start < end; start = next) {
>> + pgd_t *pgd = pgd_offset_k(start);
>> + pud_t *pud;
>> +
>> + next = (start + PGDIR_SIZE) & PGDIR_MASK;
>> + if (next > end)
>> + next = end;
>> +
>> + if (!pgd_present(*pgd))
>> + continue;
>> +
>> + pud = map_low_page((pud_t *)pgd_page_vaddr(*pgd));
>> + phys_pud_remove(pud, __pa(start), __pa(end));
>> + unmap_low_page(pud);
>> + }
>> +
>> + __flush_tlb_all();
>> +}
>> +
>> #ifdef CONFIG_MEMORY_HOTREMOVE
>> int __ref arch_remove_memory(u64 start, u64 size)
>> {
>> @@ -687,6 +832,8 @@ int __ref arch_remove_memory(u64 start,
>> ret = __remove_pages(zone, start_pfn, nr_pages);
>> WARN_ON_ONCE(ret);
>>
>> + kernel_physical_mapping_remove(start, start + size);
>> +
>> return ret;
>> }
>> #endif
>> Index: linux-3.6/arch/x86/include/asm/pgtable_types.h
>> ===================================================================
>> --- linux-3.6.orig/arch/x86/include/asm/pgtable_types.h 2012-10-04 18:26:51.925486954 +0900
>> +++ linux-3.6/arch/x86/include/asm/pgtable_types.h 2012-10-04 18:30:27.322704656 +0900
>> @@ -334,6 +334,7 @@ static inline void update_page_count(int
>> * as a pte too.
>> */
>> extern pte_t *lookup_address(unsigned long address, unsigned int *level);
>> +extern int __split_large_page(pte_t *kpte, unsigned long address, pte_t *pbase);
>>
>> #endif /* !__ASSEMBLY__ */
>>
>> Index: linux-3.6/arch/x86/mm/pageattr.c
>> ===================================================================
>> --- linux-3.6.orig/arch/x86/mm/pageattr.c 2012-10-04 18:26:51.923486952 +0900
>> +++ linux-3.6/arch/x86/mm/pageattr.c 2012-10-04 18:30:27.328704662 +0900
>> @@ -501,21 +501,13 @@ out_unlock:
>> return do_split;
>> }
>>
>> -static int split_large_page(pte_t *kpte, unsigned long address)
>> +int __split_large_page(pte_t *kpte, unsigned long address, pte_t *pbase)
>> {
>> unsigned long pfn, pfninc = 1;
>> unsigned int i, level;
>> - pte_t *pbase, *tmp;
>> + pte_t *tmp;
>> pgprot_t ref_prot;
>> - struct page *base;
>> -
>> - if (!debug_pagealloc)
>> - spin_unlock(&cpa_lock);
>> - base = alloc_pages(GFP_KERNEL | __GFP_NOTRACK, 0);
>> - if (!debug_pagealloc)
>> - spin_lock(&cpa_lock);
>> - if (!base)
>> - return -ENOMEM;
>> + struct page *base = virt_to_page(pbase);
>>
>> spin_lock(&pgd_lock);
>> /*
>> @@ -523,10 +515,11 @@ static int split_large_page(pte_t *kpte,
>> * up for us already:
>> */
>> tmp = lookup_address(address, &level);
>> - if (tmp != kpte)
>> - goto out_unlock;
>> + if (tmp != kpte) {
>> + spin_unlock(&pgd_lock);
>> + return 1;
>> + }
>>
>> - pbase = (pte_t *)page_address(base);
>> paravirt_alloc_pte(&init_mm, page_to_pfn(base));
>> ref_prot = pte_pgprot(pte_clrhuge(*kpte));
>> /*
>> @@ -579,17 +572,27 @@ static int split_large_page(pte_t *kpte,
>> * going on.
>> */
>> __flush_tlb_all();
>> + spin_unlock(&pgd_lock);
>>
>> - base = NULL;
>> + return 0;
>> +}
>>
>> -out_unlock:
>> - /*
>> - * If we dropped out via the lookup_address check under
>> - * pgd_lock then stick the page back into the pool:
>> - */
>> - if (base)
>> +static int split_large_page(pte_t *kpte, unsigned long address)
>> +{
>> + pte_t *pbase;
>> + struct page *base;
>> +
>> + if (!debug_pagealloc)
>> + spin_unlock(&cpa_lock);
>> + base = alloc_pages(GFP_KERNEL | __GFP_NOTRACK, 0);
>> + if (!debug_pagealloc)
>> + spin_lock(&cpa_lock);
>> + if (!base)
>> + return -ENOMEM;
>> +
>> + pbase = (pte_t *)page_address(base);
>> + if (__split_large_page(kpte, address, pbase))
>> __free_page(base);
>> - spin_unlock(&pgd_lock);
>>
>> return 0;
>> }
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: email@kvack.org
>>