Re: [RFC PATCH v3 11/13] memory-hotplug : free memmap of sparse-vmemmap
From: Wen Congyang
Date: Wed Jul 11 2012 - 01:02:01 EST
At 07/09/2012 06:33 PM, Yasuaki Ishimatsu Wrote:
> I don't think that all pages of virtual mapping in removed memory can be
> freed, since page which type is MIX_SECTION_INFO is difficult to free.
> So, the patch only frees page which type is SECTION_INFO at first.
>
> CC: David Rientjes <rientjes@xxxxxxxxxx>
> CC: Jiang Liu <liuj97@xxxxxxxxx>
> CC: Len Brown <len.brown@xxxxxxxxx>
> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> CC: Paul Mackerras <paulus@xxxxxxxxx>
> CC: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> CC: Wen Congyang <wency@xxxxxxxxxxxxxx>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
>
> ---
> arch/x86/mm/init_64.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mm.h | 2 +
> mm/memory_hotplug.c | 5 ++
> mm/sparse.c | 5 +-
> 4 files changed, 101 insertions(+), 2 deletions(-)
>
> Index: linux-3.5-rc4/include/linux/mm.h
> ===================================================================
> --- linux-3.5-rc4.orig/include/linux/mm.h 2012-07-03 14:22:18.530011567 +0900
> +++ linux-3.5-rc4/include/linux/mm.h 2012-07-03 14:22:20.999983872 +0900
> @@ -1588,6 +1588,8 @@ int vmemmap_populate(struct page *start_
> void vmemmap_populate_print_last(void);
> void register_page_bootmem_memmap(unsigned long section_nr, struct page *map,
> unsigned long size);
> +void vmemmap_kfree(struct page *memmpa, unsigned long nr_pages);
> +void vmemmap_free_bootmem(struct page *memmpa, unsigned long nr_pages);
>
> enum mf_flags {
> MF_COUNT_INCREASED = 1 << 0,
> Index: linux-3.5-rc4/mm/sparse.c
> ===================================================================
> --- linux-3.5-rc4.orig/mm/sparse.c 2012-07-03 14:21:45.071429805 +0900
> +++ linux-3.5-rc4/mm/sparse.c 2012-07-03 14:22:21.000983767 +0900
> @@ -614,12 +614,13 @@ static inline struct page *kmalloc_secti
> /* 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)
> {
> - return; /* XXX: Not implemented yet */
> + vmemmap_kfree(page, nr_pages);
Hmm, I think you try to free the memory allocated in kmalloc_section_memmap().
> }
> static void free_map_bootmem(struct page *page, unsigned long nr_pages)
> {
> + vmemmap_free_bootmem(page, nr_pages);
> }
Hmm, which function is the memory you try to free allocated in?
> #else
> static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
> Index: linux-3.5-rc4/arch/x86/mm/init_64.c
> ===================================================================
> --- linux-3.5-rc4.orig/arch/x86/mm/init_64.c 2012-07-03 14:22:18.538011465 +0900
> +++ linux-3.5-rc4/arch/x86/mm/init_64.c 2012-07-03 14:22:21.007983103 +0900
> @@ -978,6 +978,97 @@ vmemmap_populate(struct page *start_page
> return 0;
> }
>
> +unsigned long find_and_clear_pte_page(unsigned long addr, unsigned long end,
> + struct page **pp)
> +{
> + pgd_t *pgd;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *pte;
> + unsigned long next;
> +
> + *pp = NULL;
> +
> + pgd = pgd_offset_k(addr);
> + if (pgd_none(*pgd))
> + return (addr + PAGE_SIZE) & PAGE_MASK;
Hmm, why not goto next pgd?
> +
> + pud = pud_offset(pgd, addr);
> + if (pud_none(*pud))
> + return (addr + PAGE_SIZE) & PAGE_MASK;
> +
> + if (!cpu_has_pse) {
> + next = (addr + PAGE_SIZE) & PAGE_MASK;
> + pmd = pmd_offset(pud, addr);
> + if (pmd_none(*pmd))
> + return next;
> +
> + pte = pte_offset_kernel(pmd, addr);
> + if (pte_none(*pte))
> + return next;
> +
> + *pp = pte_page(*pte);
> + pte_clear(&init_mm, addr, pte);
I think you should flush tlb here.
> + } else {
> + next = pmd_addr_end(addr, end);
> +
> + pmd = pmd_offset(pud, addr);
> + if (pmd_none(*pmd))
> + return next;
> +
> + *pp = pmd_page(*pmd);
> + pmd_clear(pmd);
> + }
> +
> + return next;
> +}
> +
> +void __meminit
> +vmemmap_kfree(struct page *memmap, unsigned long nr_pages)
> +{
> + unsigned long addr = (unsigned long)memmap;
> + unsigned long end = (unsigned long)(memmap + nr_pages);
> + unsigned long next;
> + unsigned int order;
> + struct page *page;
> +
> + for (; addr < end; addr = next) {
> + page = NULL;
> + next = find_and_clear_pte_page(addr, end, &page);
> + if (!page)
> + continue;
> +
> + if (is_vmalloc_addr(page_address(page)))
> + vfree(page_address(page));
Hmm, the memory is allocated in vmemmap_alloc_block(), and the address
can not be vmalloc address.
> + else {
> + order = next - addr;
> + free_pages((unsigned long)page_address(page),
> + get_order(order));
OOPS. I think we cannot free pages here.
sizeof(struct page) is less than PAGE_SIZE. We store more than one struct
page in the same page. If you free it here while the other struct page
is in use, it is very dangerous.
> + }
> + }
> +}
> +
> +void __meminit
> +vmemmap_free_bootmem(struct page *memmap, unsigned long nr_pages)
> +{
> + unsigned long addr = (unsigned long)memmap;
> + unsigned long end = (unsigned long)(memmap + nr_pages);
> + unsigned long next;
> + struct page *page;
> + unsigned long magic;
> +
> + for (; addr < end; addr = next) {
> + page = NULL;
> + next = find_and_clear_pte_page(addr, end, &page);
> + if (!page)
> + continue;
> +
> + magic = (unsigned long) page->lru.next;
> + if (magic == SECTION_INFO)
> + put_page_bootmem(page);
> + }
> +}
> +
> void __meminit
> register_page_bootmem_memmap(unsigned long section_nr, struct page *start_page,
> unsigned long size)
> Index: linux-3.5-rc4/mm/memory_hotplug.c
> ===================================================================
> --- linux-3.5-rc4.orig/mm/memory_hotplug.c 2012-07-03 14:22:18.522011667 +0900
> +++ linux-3.5-rc4/mm/memory_hotplug.c 2012-07-03 14:22:21.012982694 +0900
> @@ -303,6 +303,8 @@ static int __meminit __add_section(int n
> #ifdef CONFIG_SPARSEMEM_VMEMMAP
I think this line can be removed now.
Thanks
Wen Congyang
> static int __remove_section(struct zone *zone, struct mem_section *ms)
> {
> + unsigned long flags;
> + struct pglist_data *pgdat = zone->zone_pgdat;
> int ret;
>
> if (!valid_section(ms))
> @@ -310,6 +312,9 @@ static int __remove_section(struct zone
>
> ret = unregister_memory_section(ms);
>
> + pgdat_resize_lock(pgdat, &flags);
> + sparse_remove_one_section(zone, ms);
> + pgdat_resize_unlock(pgdat, &flags);
> return ret;
> }
> #else
>
>
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