Apply memory policies to top two highest zones when highest zone is ZONE_MOVABLE

The NUMA layer only supports NUMA policies for the highest zone.  When
ZONE_MOVABLE is configured with kernelcore=, the the highest zone becomes
ZONE_MOVABLE.  The result is that policies are only applied to allocations
like anonymous pages and page cache allocated from ZONE_MOVABLE when the
zone is used.

This patch applies policies to the two highest zones when the highest zone
is ZONE_MOVABLE.  As ZONE_MOVABLE consists of pages from the highest "real"
zone, it's always functionally equivalent.

The patch has been tested on a variety of machines both NUMA and non-NUMA
covering x86, x86_64 and ppc64.  No abnormal results were seen in
kernbench, tbench, dbench or hackbench.  It passes regression tests from
the numactl package with and without kernelcore= once numactl tests are
patched to wait for vmstat counters to update.

akpm: this is the nasty hack to fix NUMA mempolicies in the presence of
ZONE_MOVABLE and kernelcore= in 2.6.23.  Christoph says "For .24 either merge
the mobility or get the other solution that Mel is working on.  That solution
would only use a single zonelist per node and filter on the fly.  That may
help performance and also help to make memory policies work better."

Signed-off-by: Mel Gorman <[email protected]>
Acked-by:  Lee Schermerhorn <[email protected]>
Tested-by:  Lee Schermerhorn <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Paul Mundt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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