libnvdimm: fix devm_nvdimm_memremap() error path

The internal alloc_nvdimm_map() helper might fail, particularly if the
memory region is already busy.  Report request_mem_region() failures and
check for the failure.

Reported-by: Ryan Chen <ryan.chan105@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c
index 715583f69d28..4d7bbd2df5c0 100644
--- a/drivers/nvdimm/core.c
+++ b/drivers/nvdimm/core.c
@@ -99,8 +99,11 @@ static struct nvdimm_map *alloc_nvdimm_map(struct device *dev,
         nvdimm_map->size = size;
         kref_init(&nvdimm_map->kref);
 
-        if (!request_mem_region(offset, size, dev_name(&nvdimm_bus->dev)))
+        if (!request_mem_region(offset, size, dev_name(&nvdimm_bus->dev))) {
+                dev_err(&nvdimm_bus->dev, "failed to request %pa + %zd for %s\n",
+                                &offset, size, dev_name(dev));
                 goto err_request_region;
+        }
 
         if (flags)
                 nvdimm_map->mem = memremap(offset, size, flags);
@@ -171,6 +174,9 @@ void *devm_nvdimm_memremap(struct device *dev, resource_size_t offset,
                 kref_get(&nvdimm_map->kref);
         nvdimm_bus_unlock(dev);
 
+        if (!nvdimm_map)
+                return NULL;
+
         if (devm_add_action_or_reset(dev, nvdimm_map_put, nvdimm_map))
                 return NULL;