nodemask: make NODEMASK_ALLOC more general

This is 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.

This patch:

NODEMASK_ALLOC(x, m) assumes x is a type of struct, which is unnecessary.
It's perfectly reasonable to use this macro to allocate a nodemask_t,
which is anonymous, either dynamically or on the stack depending on
NODES_SHIFT.
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Eric Whitney <eric.whitney@hp.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/nodemask.h

@@ -481,14 +481,14 @@ static inline int num_node_state(enum node_states state)
 
 /*
  * For nodemask scrach area.(See CPUMASK_ALLOC() in cpumask.h)
+ * NODEMASK_ALLOC(x, m) allocates an object of type 'x' with the name 'm'.
  */
-
 #if NODES_SHIFT > 8 /* nodemask_t > 64 bytes */
-#define NODEMASK_ALLOC(x, m) struct x *m = kmalloc(sizeof(*m), GFP_KERNEL)
+#define NODEMASK_ALLOC(x, m)		x *m = kmalloc(sizeof(*m), GFP_KERNEL)
 #define NODEMASK_FREE(m)		kfree(m)
 #else
-#define NODEMASK_ALLOC(x, m) struct x _m, *m = &_m
-#define NODEMASK_FREE(m)
+#define NODEMASK_ALLOC(x, m)		x _m, *m = &_m
+#define NODEMASK_FREE(m)		do {} while (0)
 #endif
 
 /* A example struture for using NODEMASK_ALLOC, used in mempolicy. */
@@ -497,7 +497,8 @@ struct nodemask_scratch {
 	nodemask_t	mask2;
 };
 
-#define NODEMASK_SCRATCH(x) NODEMASK_ALLOC(nodemask_scratch, x)
+#define NODEMASK_SCRATCH(x)	\
+		NODEMASK_ALLOC(struct nodemask_scratch, x)
 #define NODEMASK_SCRATCH_FREE(x)	NODEMASK_FREE(x)