On Wed, Oct 24, 2012 at 5:43 AM, Lai Jiangshan [off-list ref] wrote:

Currently memory_hotplug only manages the node_states[N_HIGH_MEMORY],
it forgets to manage node_states[N_NORMAL_MEMORY]. it may cause
node_states[N_NORMAL_MEMORY] becomes incorrect.

Example, if a node is empty before online, and we online a memory
which is in ZONE_NORMAL. And after online,  node_states[N_HIGH_MEMORY]
is correct, but node_states[N_NORMAL_MEMORY] is incorrect,
the online code don't set the new online node to
node_states[N_NORMAL_MEMORY].

The same things like it will happen when offline(the offline code
don't clear the node from node_states[N_NORMAL_MEMORY] when needed).
Some memory managment code depends node_states[N_NORMAL_MEMORY],
so we have to fix up the node_states[N_NORMAL_MEMORY].

We add node_states_check_changes_online() and node_states_check_changes_offline()
to detect whether node_states[N_HIGH_MEMORY] and node_states[N_NORMAL_MEMORY]
are changed while hotpluging.

Also add @status_change_nid_normal to struct memory_notify, thus
the memory hotplug callbacks know whether the node_states[N_NORMAL_MEMORY]
are changed. (We can add a @flags and reuse @status_change_nid instead of
introducing @status_change_nid_normal, but it will add much more complicated
in memory hotplug callback in every subsystem. So introdcing
@status_change_nid_normal is better and it don't change the sematic
of @status_change_nid)

Changed from V1:
        add more comments
        change the function name

Your patch didn't fix my previous comments and don't works correctly.
Please test your own patch before resubmitting. You should consider both
zone normal only node and zone high only node.

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