On Fri, May 30, 2014 at 11:17 AM, Richard Weinberger
<richard.weinber...@gmail.com> wrote:
> On Fri, May 30, 2014 at 10:24 AM, enjoy mindful <enjoymind...@gmail.com>
> wrote:
>> Hi,
>> When I'm trace uml kernel with gdb, I found there are two mem_map
>> (struct page) arrays.
>>
>> 1) the first one created in init_maps function, and pointed by *local*
>> pointer struct page *map in init_maps function
>>
>> arch/um/kernel/um_arch.c
>> 264 int __init linux_main(int argc, char **argv)
>> .....
>> 350 setup_physmem(uml_physmem, uml_reserved, physmem_size, highmem);
>> 351 if (init_maps(physmem_size, iomem_size, highmem)) {
>> 352 printf("Failed to allocate mem_map for %Lu bytes
>> of physical "
>> 353 "memory and %Lu bytes of highmem\n", physmem_size,
>> 354 highmem);
>> 355 exit(1);
>> 356 }
>>
>> 2) the second mem_map created in
>> start_kernel -> setup_arch -> paging_init -> free_area_init ->
>> free_area_init_core -> alloc_node_mem_map
>>
>> and it has been pointer by global pointer "contig_page_data->node_mem_map"
>>
>> Why need struct page array (the first one) for boot memory allocate? I
>> tried to deleted the 351~356 lines in linux_main function and the
>> built/run the uml kernel. The new kernel can boot and run. But it may
>> panic.
>
> Linux has only one mem_map array, defined in mm/memory.
> I also fail to see how the kernel can work if you delete the call to
> init_maps().
>
> *confused* :)
So, I gave it a try and it really works. Wut?
Feel free to send a cleanup patch which explains in details why it works.
Looks like you found old code. :D
--
Thanks,
//richard
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