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

wujianguo
2012-10-23T07:09:11Z

On 2012-10-22 15:11, Wen Congyang wrote:
> 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?
Sorry, I made a mistake here. Only if the page was allocated at booting, we should update
zone and totalram_pages(zone->present_pages and totalram_pages mean pages which are
managed by buddy system).

How about:
static inline void free_pagetable(struct page *page)
{
struct zone *zone;
bool bootmem = false;

/* bootmem page has reserved flag */
if (PageReserved(page)) {
__ClearPageReserved(page);
bootmem = true;
}

__free_page(page);

if (bootmem) {
zone = page_zone(page);
zone_span_writelock(zone);
zone->present_pages++;
zone_span_writeunlock(zone);
totalram_pages++;
}
}

>
>> +}
>> +
>> +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.
The page is only used by page table, so is safe to free it when all the page table
entries have been cleared, right?

>
>> + 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?
>
Yes, sure.

Thanks,
Jianguo Wu

> 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;
>>> }
>>>
>>> --
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>>
>>