libnvdimm, pmem: 'struct page' for pmem

Enable the pmem driver to handle PFN device instances.  Attaching a pmem
namespace to a pfn device triggers the driver to allocate and initialize
struct page entries for pmem.  Memory capacity for this allocation comes
exclusively from RAM for now which is suitable for low PMEM to RAM
ratios.  This mechanism will be expanded later for setting an "allocate
from PMEM" policy.

Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

tools/testing/nvdimm/test/iomap.c

@@ -108,6 +108,19 @@ void *__wrap_memremap(resource_size_t offset, size_t size,
 }
 EXPORT_SYMBOL(__wrap_memremap);
 
+void __wrap_devm_memunmap(struct device *dev, void *addr)
+{
+	struct nfit_test_resource *nfit_res;
+
+	rcu_read_lock();
+	nfit_res = get_nfit_res((unsigned long) addr);
+	rcu_read_unlock();
+	if (nfit_res)
+		return;
+	return devm_memunmap(dev, addr);
+}
+EXPORT_SYMBOL(__wrap_devm_memunmap);
+
 void __iomem *__wrap_ioremap_nocache(resource_size_t offset, unsigned long size)
 {
 	return __nfit_test_ioremap(offset, size, ioremap_nocache);