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    SubjectRe: [PATCH 3/6] x86/mm: Factor out of top-down direct mapping setup
    Hello tejun,

    On 09/24/2013 08:27 PM, Tejun Heo wrote:
    > On Tue, Sep 24, 2013 at 06:06:41PM +0800, Zhang Yanfei wrote:
    >> +/**
    >> + * memory_map_top_down - Map [map_start, map_end) top down
    >> + * @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 a heuristic way. In the beginning, step_size is small. The more memory we
    >> + * map memory in the next loop.
    >> + */
    >
    > The comment reads a bit weird to me. The step size is increased
    > gradually but that really isn't really a heuristic and it doesn't
    > mention mapping direction.

    Ok, will change the words and add the comment of direction.

    >
    > ...
    >> @@ -430,19 +430,13 @@ void __init init_mem_mapping(void)
    >> min_pfn_mapped = real_end >> PAGE_SHIFT;
    >> last_start = start = real_end;
    >>
    >> - /*
    >> - * We start from the top (end of memory) and go to the bottom.
    >> - * 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.
    >> - */
    >
    > I think this comment should stay here with the variable names
    > updated.

    OK, agreed

    >
    >> - while (last_start > ISA_END_ADDRESS) {
    >> + while (last_start > map_start) {
    >> if (last_start > step_size) {
    >> start = round_down(last_start - 1, step_size);
    >> - if (start < ISA_END_ADDRESS)
    >> - start = ISA_END_ADDRESS;
    >> + if (start < map_start)
    >> + start = map_start;
    >> } else
    >> - start = ISA_END_ADDRESS;
    >> + start = map_start;
    >> new_mapped_ram_size = init_range_memory_mapping(start,
    >> last_start);
    >> last_start = start;
    >> @@ -453,8 +447,32 @@ void __init init_mem_mapping(void)
    >> mapped_ram_size += new_mapped_ram_size;
    >> }
    >>
    >> - if (real_end < end)
    >> - init_range_memory_mapping(real_end, end);
    >> + if (real_end < map_end)
    >> + init_range_memory_mapping(real_end, map_end);
    >> +}
    >> +
    >> +void __init init_mem_mapping(void)
    >> +{
    >> + unsigned long end;
    >> +
    >> + probe_page_size_mask();
    >> +
    >> +#ifdef CONFIG_X86_64
    >> + end = max_pfn << PAGE_SHIFT;
    >> +#else
    >> + end = max_low_pfn << PAGE_SHIFT;
    >> +#endif
    >> +
    >> + /* the ISA range is always mapped regardless of memory holes */
    >> + init_memory_mapping(0, ISA_END_ADDRESS);
    >> +
    >> + /*
    >> + * We start from the top (end of memory) and go to the bottom.
    >> + * 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.
    >> + */
    >
    > And just mention the range and direction in the comment here?

    OK, agreed.

    Thanks

    >
    >> + memory_map_top_down(ISA_END_ADDRESS, end);
    >
    > Thanks.
    >


    --
    Thanks.
    Zhang Yanfei


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