Hello tejun,
On 09/26/2013 10:48 PM, Tejun Heo wrote:
> 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.
OK, will do.
>
>> + */
>> +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?
I've explained to him. Nop, we don't need to worry about that. Because even
the min_pfn_mapped becomes ISA_END_ADDRESS in the second call below, we won't
allocate memory below the kernel because we have limited the allocation above
the kernel.
Thanks.
--
Thanks.
Zhang Yanfei
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
