[PATCH v6 08/15] memory-hotplug: Common APIs to support page tables hot-remove
Simon Jeons
simon.jeons at gmail.com
Wed Jan 30 14:27:05 EST 2013
On Wed, 2013-01-30 at 10:16 +0800, Tang Chen wrote:
> On 01/29/2013 09:04 PM, Simon Jeons wrote:
> > Hi Tang,
> > On Wed, 2013-01-09 at 17:32 +0800, Tang Chen wrote:
> >> From: Wen Congyang<wency at cn.fujitsu.com>
> >>
> >> When memory is removed, the corresponding pagetables should alse be removed.
> >> This patch introduces some common APIs to support vmemmap pagetable and x86_64
> >> architecture pagetable removing.
> >
> > Why don't need to build_all_zonelists like online_pages does during
> > hot-add path(add_memory)?
>
> Hi Simon,
>
> As you said, build_all_zonelists is done by online_pages. When the
> memory device
> is hot-added, we cannot use it. we can only use is when we online the
> pages on it.
Why?
If a node has just one memory device and memory is small, some zone will
not present like zone_highmem, then hot-add another memory device and
zone_highmem appear, if you should build_all_zonelists this time?
>
> But we can online the pages as different types, kernel or movable (which
> belongs to
> different zones), and we can online part of the memory, not all of them.
> So each time we online some pages, we should check if we need to update
> the zone list.
>
> So I think that is why we do build_all_zonelists when online_pages.
> (just my opinion)
>
> Thanks. :)
>
> >
> >>
> >> All pages of virtual mapping in removed memory cannot be freedi if some pages
> >> used as PGD/PUD includes not only removed memory but also other memory. So the
> >> patch uses the following way 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.
> >>
> >> Signed-off-by: Yasuaki Ishimatsu<isimatu.yasuaki at jp.fujitsu.com>
> >> Signed-off-by: Jianguo Wu<wujianguo at huawei.com>
> >> Signed-off-by: Wen Congyang<wency at cn.fujitsu.com>
> >> Signed-off-by: Tang Chen<tangchen at cn.fujitsu.com>
> >> ---
> >> arch/x86/include/asm/pgtable_types.h | 1 +
> >> arch/x86/mm/init_64.c | 299 ++++++++++++++++++++++++++++++++++
> >> arch/x86/mm/pageattr.c | 47 +++---
> >> include/linux/bootmem.h | 1 +
> >> 4 files changed, 326 insertions(+), 22 deletions(-)
> >>
> >> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> >> index 3c32db8..4b6fd2a 100644
> >> --- a/arch/x86/include/asm/pgtable_types.h
> >> +++ b/arch/x86/include/asm/pgtable_types.h
> >> @@ -352,6 +352,7 @@ static inline void update_page_count(int level, unsigned long pages) { }
> >> * 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__ */
> >>
> >> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> >> index 9ac1723..fe01116 100644
> >> --- a/arch/x86/mm/init_64.c
> >> +++ b/arch/x86/mm/init_64.c
> >> @@ -682,6 +682,305 @@ int arch_add_memory(int nid, u64 start, u64 size)
> >> }
> >> EXPORT_SYMBOL_GPL(arch_add_memory);
> >>
> >> +#define PAGE_INUSE 0xFD
> >> +
> >> +static void __meminit free_pagetable(struct page *page, int order)
> >> +{
> >> + struct zone *zone;
> >> + bool bootmem = false;
> >> + unsigned long magic;
> >> + unsigned int nr_pages = 1<< order;
> >> +
> >> + /* bootmem page has reserved flag */
> >> + if (PageReserved(page)) {
> >> + __ClearPageReserved(page);
> >> + bootmem = true;
> >> +
> >> + magic = (unsigned long)page->lru.next;
> >> + if (magic == SECTION_INFO || magic == MIX_SECTION_INFO) {
> >> + while (nr_pages--)
> >> + put_page_bootmem(page++);
> >> + } else
> >> + __free_pages_bootmem(page, order);
> >> + } else
> >> + free_pages((unsigned long)page_address(page), order);
> >> +
> >> + /*
> >> + * SECTION_INFO pages and MIX_SECTION_INFO pages
> >> + * are all allocated by bootmem.
> >> + */
> >> + if (bootmem) {
> >> + zone = page_zone(page);
> >> + zone_span_writelock(zone);
> >> + zone->present_pages += nr_pages;
> >> + zone_span_writeunlock(zone);
> >> + totalram_pages += nr_pages;
> >> + }
> >> +}
> >> +
> >> +static void __meminit 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))
> >> + return;
> >> + }
> >> +
> >> + /* free a pte talbe */
> >> + free_pagetable(pmd_page(*pmd), 0);
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pmd_clear(pmd);
> >> + spin_unlock(&init_mm.page_table_lock);
> >> +}
> >> +
> >> +static void __meminit 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))
> >> + return;
> >> + }
> >> +
> >> + /* free a pmd talbe */
> >> + free_pagetable(pud_page(*pud), 0);
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pud_clear(pud);
> >> + spin_unlock(&init_mm.page_table_lock);
> >> +}
> >> +
> >> +/* Return true if pgd is changed, otherwise return false. */
> >> +static bool __meminit 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))
> >> + return false;
> >> + }
> >> +
> >> + /* free a pud table */
> >> + free_pagetable(pgd_page(*pgd), 0);
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pgd_clear(pgd);
> >> + spin_unlock(&init_mm.page_table_lock);
> >> +
> >> + return true;
> >> +}
> >> +
> >> +static void __meminit
> >> +remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,
> >> + bool direct)
> >> +{
> >> + unsigned long next, pages = 0;
> >> + pte_t *pte;
> >> + void *page_addr;
> >> + phys_addr_t phys_addr;
> >> +
> >> + pte = pte_start + pte_index(addr);
> >> + for (; addr< end; addr = next, pte++) {
> >> + next = (addr + PAGE_SIZE)& PAGE_MASK;
> >> + if (next> end)
> >> + next = end;
> >> +
> >> + if (!pte_present(*pte))
> >> + continue;
> >> +
> >> + /*
> >> + * We mapped [0,1G) memory as identity mapping when
> >> + * initializing, in arch/x86/kernel/head_64.S. These
> >> + * pagetables cannot be removed.
> >> + */
> >> + phys_addr = pte_val(*pte) + (addr& PAGE_MASK);
> >> + if (phys_addr< (phys_addr_t)0x40000000)
> >> + return;
> >> +
> >> + if (IS_ALIGNED(addr, PAGE_SIZE)&&
> >> + IS_ALIGNED(next, PAGE_SIZE)) {
> >> + if (!direct) {
> >> + free_pagetable(pte_page(*pte), 0);
> >> + pages++;
> >> + }
> >> +
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pte_clear(&init_mm, addr, pte);
> >> + spin_unlock(&init_mm.page_table_lock);
> >> + } else {
> >> + /*
> >> + * If we are not removing the whole page, it means
> >> + * other ptes in this page are being used and we canot
> >> + * remove them. So fill the unused ptes with 0xFD, and
> >> + * remove the page when it is wholly filled with 0xFD.
> >> + */
> >> + memset((void *)addr, PAGE_INUSE, next - addr);
> >> + page_addr = page_address(pte_page(*pte));
> >> +
> >> + if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) {
> >> + free_pagetable(pte_page(*pte), 0);
> >> + pages++;
> >> +
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pte_clear(&init_mm, addr, pte);
> >> + spin_unlock(&init_mm.page_table_lock);
> >> + }
> >> + }
> >> + }
> >> +
> >> + /* Call free_pte_table() in remove_pmd_table(). */
> >> + flush_tlb_all();
> >> + if (direct)
> >> + update_page_count(PG_LEVEL_4K, -pages);
> >> +}
> >> +
> >> +static void __meminit
> >> +remove_pmd_table(pmd_t *pmd_start, unsigned long addr, unsigned long end,
> >> + bool direct)
> >> +{
> >> + unsigned long pte_phys, next, pages = 0;
> >> + pte_t *pte_base;
> >> + pmd_t *pmd;
> >> +
> >> + pmd = pmd_start + pmd_index(addr);
> >> + for (; addr< end; addr = next, pmd++) {
> >> + next = pmd_addr_end(addr, end);
> >> +
> >> + if (!pmd_present(*pmd))
> >> + continue;
> >> +
> >> + if (pmd_large(*pmd)) {
> >> + if (IS_ALIGNED(addr, PMD_SIZE)&&
> >> + IS_ALIGNED(next, PMD_SIZE)) {
> >> + if (!direct) {
> >> + free_pagetable(pmd_page(*pmd),
> >> + get_order(PMD_SIZE));
> >> + pages++;
> >> + }
> >> +
> >> + 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 = (pte_t *)alloc_low_page(&pte_phys);
> >> + BUG_ON(!pte_base);
> >> + __split_large_page((pte_t *)pmd, addr,
> >> + (pte_t *)pte_base);
> >> +
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pmd_populate_kernel(&init_mm, pmd, __va(pte_phys));
> >> + spin_unlock(&init_mm.page_table_lock);
> >> +
> >> + flush_tlb_all();
> >> + }
> >> +
> >> + pte_base = (pte_t *)map_low_page((pte_t *)pmd_page_vaddr(*pmd));
> >> + remove_pte_table(pte_base, addr, next, direct);
> >> + free_pte_table(pte_base, pmd);
> >> + unmap_low_page(pte_base);
> >> + }
> >> +
> >> + /* Call free_pmd_table() in remove_pud_table(). */
> >> + if (direct)
> >> + update_page_count(PG_LEVEL_2M, -pages);
> >> +}
> >> +
> >> +static void __meminit
> >> +remove_pud_table(pud_t *pud_start, unsigned long addr, unsigned long end,
> >> + bool direct)
> >> +{
> >> + unsigned long pmd_phys, next, pages = 0;
> >> + pmd_t *pmd_base;
> >> + pud_t *pud;
> >> +
> >> + pud = pud_start + pud_index(addr);
> >> + for (; addr< end; addr = next, pud++) {
> >> + next = pud_addr_end(addr, end);
> >> +
> >> + if (!pud_present(*pud))
> >> + continue;
> >> +
> >> + if (pud_large(*pud)) {
> >> + if (IS_ALIGNED(addr, PUD_SIZE)&&
> >> + IS_ALIGNED(next, PUD_SIZE)) {
> >> + if (!direct) {
> >> + free_pagetable(pud_page(*pud),
> >> + get_order(PUD_SIZE));
> >> + pages++;
> >> + }
> >> +
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pud_clear(pud);
> >> + spin_unlock(&init_mm.page_table_lock);
> >> + continue;
> >> + }
> >> +
> >> + /*
> >> + * We use 1G page, but we need to remove part of them,
> >> + * so split 1G page to 2M page.
> >> + */
> >> + pmd_base = (pmd_t *)alloc_low_page(&pmd_phys);
> >> + BUG_ON(!pmd_base);
> >> + __split_large_page((pte_t *)pud, addr,
> >> + (pte_t *)pmd_base);
> >> +
> >> + spin_lock(&init_mm.page_table_lock);
> >> + pud_populate(&init_mm, pud, __va(pmd_phys));
> >> + spin_unlock(&init_mm.page_table_lock);
> >> +
> >> + flush_tlb_all();
> >> + }
> >> +
> >> + pmd_base = (pmd_t *)map_low_page((pmd_t *)pud_page_vaddr(*pud));
> >> + remove_pmd_table(pmd_base, addr, next, direct);
> >> + free_pmd_table(pmd_base, pud);
> >> + unmap_low_page(pmd_base);
> >> + }
> >> +
> >> + if (direct)
> >> + update_page_count(PG_LEVEL_1G, -pages);
> >> +}
> >> +
> >> +/* start and end are both virtual address. */
> >> +static void __meminit
> >> +remove_pagetable(unsigned long start, unsigned long end, bool direct)
> >> +{
> >> + unsigned long next;
> >> + pgd_t *pgd;
> >> + pud_t *pud;
> >> + bool pgd_changed = false;
> >> +
> >> + for (; start< end; start = next) {
> >> + pgd = pgd_offset_k(start);
> >> + if (!pgd_present(*pgd))
> >> + continue;
> >> +
> >> + next = pgd_addr_end(start, end);
> >> +
> >> + pud = (pud_t *)map_low_page((pud_t *)pgd_page_vaddr(*pgd));
> >> + remove_pud_table(pud, start, next, direct);
> >> + if (free_pud_table(pud, pgd))
> >> + pgd_changed = true;
> >> + unmap_low_page(pud);
> >> + }
> >> +
> >> + if (pgd_changed)
> >> + sync_global_pgds(start, end - 1);
> >> +
> >> + flush_tlb_all();
> >> +}
> >> +
> >> #ifdef CONFIG_MEMORY_HOTREMOVE
> >> int __ref arch_remove_memory(u64 start, u64 size)
> >> {
> >> diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
> >> index a718e0d..7dcb6f9 100644
> >> --- a/arch/x86/mm/pageattr.c
> >> +++ b/arch/x86/mm/pageattr.c
> >> @@ -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, unsigned long address)
> >> * 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, unsigned long address)
> >> * 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;
> >> }
> >> diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
> >> index 3f778c2..190ff06 100644
> >> --- a/include/linux/bootmem.h
> >> +++ b/include/linux/bootmem.h
> >> @@ -53,6 +53,7 @@ extern void free_bootmem_node(pg_data_t *pgdat,
> >> unsigned long size);
> >> extern void free_bootmem(unsigned long physaddr, unsigned long size);
> >> extern void free_bootmem_late(unsigned long physaddr, unsigned long size);
> >> +extern void __free_pages_bootmem(struct page *page, unsigned int order);
> >>
> >> /*
> >> * Flags for reserve_bootmem (also if CONFIG_HAVE_ARCH_BOOTMEM_NODE,
> >
> >
> > --
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> >
>
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