[PATCH RESEND] crash_core: export vmemmap when CONFIG_SPARSEMEM_VMEMMAP is enabled

[Andrew Morton]

On Mon, 26 Feb 2024 10:04:33 +0800 Huang Shijie <shijie at os.amperecomputing.com> wrote:

> In memory_model.h, if CONFIG_SPARSEMEM_VMEMMAP is configed,
> kernel will use vmemmap to do the __pfn_to_page/page_to_pfn,
> and kernel will not use the "classic sparse" to do the
> __pfn_to_page/page_to_pfn.
> 
> So export the vmemmap when CONFIG_SPARSEMEM_VMEMMAP is configed.
> This makes the user applications (crash, etc) get faster
> pfn_to_page/page_to_pfn operations too.

This is significantly out of sync with development trees.  Please take
a look at linux-next and redo the patch if still needed?