libnvdimm, pmem: direct map legacy pmem by default

The expectation is that the legacy / non-standard pmem discovery method
(e820 type-12) will only ever be used to describe small quantities of
persistent memory.  Larger capacities will be described via the ACPI
NFIT.  When "allocate struct page from pmem" support is added this default
policy can be overridden by assigning a legacy pmem namespace to a pfn
device, however this would be only be necessary if a platform used the
legacy mechanism to define a very large range.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 30 insertions, 5 deletions

diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 9303ca29be9b..0955b2cb10fe 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/slab.h>
+#include <linux/pmem.h>
 #include <linux/nd.h>
 #include "nd-core.h"
 #include "nd.h"
@@ -76,11 +77,32 @@ static bool is_namespace_io(struct device *dev)
         return dev ? dev->type == &namespace_io_device_type : false;
 }
 
+bool pmem_should_map_pages(struct device *dev)
+{
+        struct nd_region *nd_region = to_nd_region(dev->parent);
+
+        if (!IS_ENABLED(CONFIG_ZONE_DEVICE))
+                return false;
+
+        if (!test_bit(ND_REGION_PAGEMAP, &nd_region->flags))
+                return false;
+
+        if (is_nd_pfn(dev) || is_nd_btt(dev))
+                return false;
+
+#ifdef ARCH_MEMREMAP_PMEM
+        return ARCH_MEMREMAP_PMEM == MEMREMAP_WB;
+#else
+        return false;
+#endif
+}
+EXPORT_SYMBOL(pmem_should_map_pages);
+
 const char *nvdimm_namespace_disk_name(struct nd_namespace_common *ndns,
                 char *name)
 {
         struct nd_region *nd_region = to_nd_region(ndns->dev.parent);
-        const char *suffix = "";
+        const char *suffix = NULL;
 
         if (ndns->claim) {
                 if (is_nd_btt(ndns->claim))
@@ -93,13 +115,16 @@ const char *nvdimm_namespace_disk_name(struct nd_namespace_common *ndns,
                                         dev_name(ndns->claim));
         }
 
-        if (is_namespace_pmem(&ndns->dev) || is_namespace_io(&ndns->dev))
-                sprintf(name, "pmem%d%s", nd_region->id, suffix);
-        else if (is_namespace_blk(&ndns->dev)) {
+        if (is_namespace_pmem(&ndns->dev) || is_namespace_io(&ndns->dev)) {
+                if (!suffix && pmem_should_map_pages(&ndns->dev))
+                        suffix = "m";
+                sprintf(name, "pmem%d%s", nd_region->id, suffix ? suffix : "");
+        } else if (is_namespace_blk(&ndns->dev)) {
                 struct nd_namespace_blk *nsblk;
 
                 nsblk = to_nd_namespace_blk(&ndns->dev);
-                sprintf(name, "ndblk%d.%d%s", nd_region->id, nsblk->id, suffix);
+                sprintf(name, "ndblk%d.%d%s", nd_region->id, nsblk->id,
+                                suffix ? suffix : "");
         } else {
                 return NULL;
         }