Re: [PATCH v5 4/6] x86/mem-hotplug: Support initialize page tablesin bottom-up

[Tejun Heo]

Hello,

On Wed, Sep 25, 2013 at 02:30:51AM +0800, Zhang Yanfei wrote:
> +/**
> + * memory_map_bottom_up - Map [map_start, map_end) bottom up
> + * @map_start: start address of the target memory range
> + * @map_end: end address of the target memory range
> + *
> + * This function will setup direct mapping for memory range
> + * [map_start, map_end) in bottom-up.

Ditto about the comment.

> + */
> +static void __init memory_map_bottom_up(unsigned long map_start,
> +					unsigned long map_end)
> +{
> +	unsigned long next, new_mapped_ram_size, start;
> +	unsigned long mapped_ram_size = 0;
> +	/* step_size need to be small so pgt_buf from BRK could cover it */
> +	unsigned long step_size = PMD_SIZE;
> +
> +	start = map_start;
> +	min_pfn_mapped = start >> PAGE_SHIFT;
> +
> +	/*
> +	 * We start from the bottom (@map_start) and go to the top (@map_end).
> +	 * The memblock_find_in_range() gets us a block of RAM from the
> +	 * end of RAM in [min_pfn_mapped, max_pfn_mapped) used as new pages
> +	 * for page table.
> +	 */
> +	while (start < map_end) {
> +		if (map_end - start > step_size) {
> +			next = round_up(start + 1, step_size);
> +			if (next > map_end)
> +				next = map_end;
> +		} else
> +			next = map_end;
> +
> +		new_mapped_ram_size = init_range_memory_mapping(start, next);
> +		start = next;
> +
> +		if (new_mapped_ram_size > mapped_ram_size)
> +			step_size <<= STEP_SIZE_SHIFT;
> +		mapped_ram_size += new_mapped_ram_size;
> +	}
> +}

As Yinghai pointed out in another thread, do we need to worry about
falling back to top-down?

Thanks.

-- 
tejun
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