hugetlb: V9 numa control of persistent huge pages alloc/free

PATCH 0/11 hugetlb: numa control of persistent huge pages alloc/free

Against:  2.6.31-mmotm-090925-1435 plus David Rientjes'
"nodemask: make NODEMASK_ALLOC more general" patch applied

This is V9 of a series of patches to provide control over the location
of the allocation and freeing of persistent huge pages on a NUMA
platform.   Please consider for merging into mmotm.

This series uses two mechanisms to constrain the nodes from which
persistent huge pages are allocated:  1) the task NUMA mempolicy of
the task modifying  a new sysctl "nr_hugepages_mempolicy", based on
a suggestion by Mel Gorman; and 2) a subset of the hugepages hstate
sysfs attributes have been added [in V4] to each node system device
under:

	/sys/devices/node/node[0-9]*/hugepages.

The per node attibutes allow direct assignment of a huge page
count on a specific node, regardless of the task's mempolicy or
cpuset constraints.

V5 addressed review comments -- changes described in patch descriptions.

V6 addressed more review comments, described in the patches.

V6 also included a 3 patch series that implements an enhancement suggested
by David Rientjes:   the default huge page nodes allowed mask will be the
nodes with memory rather than all on-line nodes and we will allocate per
node hstate attributes only for nodes with memory.  This requires that we
register a memory on/off-line notifier and [un]register the attributes on
transitions to/from memoryless state.

V7 addressed review comments, described in the patches, and included a
new patch, originally from Mel Gorman, to define a new vm sysctl and
sysfs global hugepages attribute "nr_hugepages_mempolicy" rather than
apply mempolicy contraints to pool adujstments via the pre-existing
"nr_hugepages".  The 3 patches to restrict hugetlb to visiting only
nodes with memory and to add/remove per node hstate attributes on
memory hotplug completed V7.

V8 reorganized the sysctl and sysfs attribute handlers to default
the nodes to default or define the nodes_allowed mask up in the
handlers and pass nodes_allowed [pointer] to set_max_huge_pages().
This cleanup was suggested by David Rientjes.  V8 also merged Mel
Gorman's "nr_hugepages_mempolicy" back into the patch to compute
nodes_allowed from mempolicy.

V8 turned out to be too large a reorg to pull off without botching
something.  V9 fixes these.  In the meantime, David Rientjes has
posted a patch to generalize NODEMASK_ALLOC.  This causes a build error
in my series.  David provided a patch to fix the build failure.  I
have included David's fixup as patch NN.  This causes V9 to depend
on David's patch.

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