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List: linux-sparc
Subject: Re: [Patch v4 08/12] memory-hotplug: remove memmap of sparse-vmemmap
From: Yasuaki Ishimatsu <isimatu.yasuaki () jp ! fujitsu ! com>
Date: 2012-11-30 2:55:39
Message-ID: 50B8202B.80503 () jp ! fujitsu ! com
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Hi Jianguo,
2012/11/30 11:47, Jianguo Wu wrote:
> Hi Congyang,
>
> Thanks for your review and comments.
>
> On 2012/11/30 9:45, Wen Congyang wrote:
>
> > At 11/28/2012 05:40 PM, Jianguo Wu Wrote:
> > > 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));
> >
> > Hmm, vmemmap doesn't use vmalloc() to allocate memory.
> >
>
> yes, this can be removed.
>
> > > + 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);
> >
> > If addr or end is not alianed with PAGE_SIZE, you may leak some
> > memory.
> >
>
> yes, I think we can handle this situation with the method you mentioned in the \
> change log: 1. When removing memory, the page structs of the revmoved memory are \
> filled with 0xFD.
> 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.
>
> By the way, why is 0xFD?
There is no reason. I just filled the page with unique number.
Thanks,
Yasuaki Ishimatsu
>
> > > + }
> > > + }
> > > +
> > > + 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);
> >
> > get_zeored_page() may fail. You should handle this error.
> >
>
> That means system is out of memory, I will trigger a bug_on.
>
> > > + 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);
> >
> > The parameter for sync_global_pgds() is [start, end], not
> > [start, end)
> >
>
> yes, thanks.
>
> > > + }
> > > +}
> > > +#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)
> > Why do you change this line?
> >
>
> 0k, it is no need to change.
>
> > > {
> > > - 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)
> >
> >
> > .
> >
>
>
>
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