Re: [RFC][PATCH] vmemmap on sparsemem v2 [1/5] generic vmemmap on sparsemem

[Heiko Carstens <heiko.carstens@de.ibm.com>]

> We can assume that total size of mem_map per section is aligned to PAGE_SIZE.
[...]
> +static int __meminit map_virtual_mem_map(unsigned long section, int node)
> +{
> +	unsigned long vmap_start, vmap_end, vmap;
> +	void *pg;
> +	pgd_t *pgd;
> +	pud_t *pud;
> +	pmd_t *pmd;
> +	pte_t *pte;
> +
> +	vmap_start = (unsigned long)pfn_to_page(section_nr_to_pfn(section));
> +	vmap_end = vmap_start + PAGES_PER_SECTION * sizeof(struct page);
> +
> +	for (vmap = vmap_start;
> +	     vmap != vmap_end;
> +	     vmap += PAGE_SIZE)
> +	{

Hmm.. maybe I'm just too tired. But why does this work? Why is vmap_start
PAGE_SIZE aligned and why is vmap_end PAGE_SIZE aligned too?

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