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

Wen Congyang
2012-10-23T07:41:38Z

At 10/23/2012 03:09 PM, wujianguo Wrote:
> 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++;
> }
> }

This verson looks fine to me.

>
>>
>>> +}
>>> +
>>> +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?

Yes, but I guess we need to do more. For example, all boot memory are in memblock.reserved,
and you don't update memblock here.

Thanks
Wen Congyang

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