Re: [PATCH v2] powerpc: Track backing pages allocated by vmemmap_populate()

[Mark Nelson <markn@au1.ibm.com>]

On Tuesday 13 April 2010 15:24:17 Michael Ellerman wrote:
> On Tue, 2010-04-13 at 14:16 +1000, Mark Nelson wrote:
> > We need to keep track of the backing pages that get allocated by
> > vmemmap_populate() so that when we use kdump, the dump-capture kernel knows
> > where these pages are.
> > 
> > We use a linked list of structures that contain the physical address of the
> > backing page and corresponding virtual address to track the backing pages.
> > We can use an hlist to save space, because we never remove nodes.
> 
> What if we remove_memory() ? Or does that not do what I think it does?

That's a good question, and one that I probably should have added to the
commit message.
But, following through, it looks like we end up calling into
__remove_section() from mm/memory_hotplug.c and if
CONFIG_SPARSEMEM_VMEMMAP is enabled we just return EBUSY as freeing
memmap with vmemmap isn't implemented yet.

So for the moment, I'm not sure we have to worry about it.

Thanks!
Mark.