cpuset: update top cpuset's mems after adding a node

cpuset: update top cpuset's mems after adding a node

After adding a node into the machine, top cpuset's mems isn't updated.

By reviewing the code, we found that the update function

  cpuset_track_online_nodes()

was invoked after node_states[N_ONLINE] changes.  It is wrong because
N_ONLINE just means node has pgdat, and if node has/added memory, we use
N_HIGH_MEMORY.  So, We should invoke the update function after
node_states[N_HIGH_MEMORY] changes, just like its commit says.

This patch fixes it.  And we use notifier of memory hotplug instead of
direct calling of cpuset_track_online_nodes().

Signed-off-by: Miao Xie <[email protected]>
Acked-by: Yasunori Goto <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Paul Menage <[email protected]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>