On Mon, 29 Oct 2012, Michal Hocko wrote:

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N_HIGH_MEMORY stands for the nodes that has normal or high memory.
N_MEMORY stands for the nodes that has any memory.

What is the difference of those two?

Patch 5 in the series 

Strange, I do not see that one at the mailing list.

http://marc.info/?l=linux-kernel&m=135152595827692

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introduces it to be equal to N_HIGH_MEMORY, so 

So this is just a rename? If yes it would be much esier if it was
mentioned in the patch description.

It's not even a rename even though it should be, it's adding yet another 
node_states that is equal to N_HIGH_MEMORY since that state already 
includes all memory.  It's just a matter of taste but I think we should be 
renaming it instead of aliasing it (unless you actually want to make 
N_HIGH_MEMORY only include nodes with highmem, but nothing depends on 
that).