Re: [Patch](memory hotplug) Hot-add with sparsemem-vmemmap

[mel@skynet.ie (Mel Gorman)]

On (17/08/07 16:08), Yasunori Goto didst pronounce:
> Hello.
> 
> This patch is to avoid panic when memory hot-add is executed with
> sparsemem-vmemmap. Current vmemmap-sparsemem code doesn't support
> memory hot-add. Vmemmap must be populated when hot-add.
> This is for 2.6.23-rc2-mm2.
> 
> Todo: # Even if this patch is applied, the message "[xxxx-xxxx] potential
>         offnode page_structs" is displayed. To allocate memmap on its node,
>         memmap (and pgdat) must be initialized itself like chicken and
>         egg relationship.
> 
>       # vmemmap_unpopulate will be necessary for followings.
>          - For cancel hot-add due to error.
>          - For unplug.
> 
> Please comment.
> 
> Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
> 
> ---
>  include/linux/mm.h  |    2 +-
>  mm/sparse-vmemmap.c |    2 +-
>  mm/sparse.c         |   24 +++++++++++++++++++++---
>  3 files changed, 23 insertions(+), 5 deletions(-)
> 
> Index: vmemmap/mm/sparse-vmemmap.c
> ===================================================================
> --- vmemmap.orig/mm/sparse-vmemmap.c	2007-08-10 20:17:19.000000000 +0900
> +++ vmemmap/mm/sparse-vmemmap.c	2007-08-10 21:12:54.000000000 +0900
> @@ -170,7 +170,7 @@ int __meminit vmemmap_populate(struct pa
>  }
>  #endif /* !CONFIG_ARCH_POPULATES_SPARSEMEM_VMEMMAP */
>  
> -struct page __init *sparse_early_mem_map_populate(unsigned long pnum, int nid)
> +struct page *sparse_mem_map_populate(unsigned long pnum, int nid)

__meminit here instead of __init?

>  {
>  	struct page *map = pfn_to_page(pnum * PAGES_PER_SECTION);
>  	int error = vmemmap_populate(map, PAGES_PER_SECTION, nid);
> Index: vmemmap/include/linux/mm.h
> ===================================================================
> --- vmemmap.orig/include/linux/mm.h	2007-08-10 20:17:19.000000000 +0900
> +++ vmemmap/include/linux/mm.h	2007-08-10 21:06:34.000000000 +0900
> @@ -1146,7 +1146,7 @@ extern int randomize_va_space;
>  
>  const char * arch_vma_name(struct vm_area_struct *vma);
>  
> -struct page *sparse_early_mem_map_populate(unsigned long pnum, int nid);
> +struct page *sparse_mem_map_populate(unsigned long pnum, int nid);
>  int vmemmap_populate(struct page *start_page, unsigned long pages, int node);
>  int vmemmap_populate_pmd(pud_t *, unsigned long, unsigned long, int);
>  void *vmemmap_alloc_block(unsigned long size, int node);
> Index: vmemmap/mm/sparse.c
> ===================================================================
> --- vmemmap.orig/mm/sparse.c	2007-08-10 20:17:19.000000000 +0900
> +++ vmemmap/mm/sparse.c	2007-08-10 21:21:01.000000000 +0900
> @@ -259,7 +259,7 @@ static unsigned long *sparse_early_usema
>  }
>  
>  #ifndef CONFIG_SPARSEMEM_VMEMMAP
> -struct page __init *sparse_early_mem_map_populate(unsigned long pnum, int nid)
> +struct page __init *sparse_mem_map_populate(unsigned long pnum, int nid)

__meminit again possibly.

>  {
>  	struct page *map;
>  
> @@ -284,7 +284,7 @@ struct page __init *sparse_early_mem_map
>  	struct mem_section *ms = __nr_to_section(pnum);
>  	int nid = sparse_early_nid(ms);
>  
> -	map = sparse_early_mem_map_populate(pnum, nid);
> +	map = sparse_mem_map_populate(pnum, nid);
>  	if (map)
>  		return map;
>  
> @@ -322,6 +322,17 @@ void __init sparse_init(void)
>  }
>  
>  #ifdef CONFIG_MEMORY_HOTPLUG
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> +static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
> +						 unsigned long nr_pages)
> +{
> +	return sparse_mem_map_populate(pnum, nid);
> +}

In the other version of __kmalloc_section_memmap(), pages get allocated
from alloc_pages() and it's obvious it's allocated there. A one line
comment saying that sparse_mem_map_populate() will make the necessary
allocations eventually would be nice.

Not a big deal though.

> +static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
> +{
> +	return; /* XXX: Not implemented yet */
> +}
> +#else
>  static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
>  {
>  	struct page *page, *ret;
> @@ -344,6 +355,12 @@ got_map_ptr:
>  	return ret;
>  }
>  
> +static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
> +						  unsigned long nr_pages)
> +{
> +	return __kmalloc_section_memmap(nr_pages);
> +}
> +
>  static int vaddr_in_vmalloc_area(void *addr)
>  {
>  	if (addr >= (void *)VMALLOC_START &&
> @@ -360,6 +377,7 @@ static void __kfree_section_memmap(struc
>  		free_pages((unsigned long)memmap,
>  			   get_order(sizeof(struct page) * nr_pages));
>  }
> +#endif /* CONFIG_SPARSEMEM_VMEMMAP */
>  
>  /*
>   * returns the number of sections whose mem_maps were properly
> @@ -382,7 +400,7 @@ int sparse_add_one_section(struct zone *
>  	 * plus, it does a kmalloc
>  	 */
>  	sparse_index_init(section_nr, pgdat->node_id);
> -	memmap = __kmalloc_section_memmap(nr_pages);
> +	memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, nr_pages);
>  	usemap = __kmalloc_section_usemap();
>  
>  	pgdat_resize_lock(pgdat, &flags);
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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