3 files changed, 31 insertions, 16 deletions

diff --git a/drivers/dax/device-dax.h b/drivers/dax/device-dax.h
index fdcd9769ffde..688b051750bd 100644
--- a/drivers/dax/device-dax.h
+++ b/drivers/dax/device-dax.h
@@ -21,5 +21,5 @@ struct dax_region *alloc_dax_region(struct device *parent,
                 int region_id, struct resource *res, unsigned int align,
                 void *addr, unsigned long flags);
 struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
-                struct resource *res, int count);
+                int id, struct resource *res, int count);
 #endif /* __DEVICE_DAX_H__ */
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 12943d19bfc4..e9f3b3e4bbf4 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -529,7 +529,8 @@ static void dev_dax_release(struct device *dev)
         struct dax_region *dax_region = dev_dax->region;
         struct dax_device *dax_dev = dev_dax->dax_dev;
 
-        ida_simple_remove(&dax_region->ida, dev_dax->id);
+        if (dev_dax->id >= 0)
+                ida_simple_remove(&dax_region->ida, dev_dax->id);
         dax_region_put(dax_region);
         put_dax(dax_dev);
         kfree(dev_dax);
@@ -559,7 +560,7 @@ static void unregister_dev_dax(void *dev)
 }
 
 struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
-                struct resource *res, int count)
+                int id, struct resource *res, int count)
 {
         struct device *parent = dax_region->dev;
         struct dax_device *dax_dev;
@@ -567,7 +568,10 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
         struct inode *inode;
         struct device *dev;
         struct cdev *cdev;
-        int rc = 0, i;
+        int rc, i;
+
+        if (!count)
+                return ERR_PTR(-EINVAL);
 
         dev_dax = kzalloc(sizeof(*dev_dax) + sizeof(*res) * count, GFP_KERNEL);
         if (!dev_dax)
@@ -587,10 +591,16 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
         if (i < count)
                 goto err_id;
 
-        dev_dax->id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
-        if (dev_dax->id < 0) {
-                rc = dev_dax->id;
-                goto err_id;
+        if (id < 0) {
+                id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
+                dev_dax->id = id;
+                if (id < 0) {
+                        rc = id;
+                        goto err_id;
+                }
+        } else {
+                /* region provider owns @id lifetime */
+                dev_dax->id = -1;
         }
 
         /*
@@ -598,8 +608,10 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
          * device outside of mmap of the resulting character device.
          */
         dax_dev = alloc_dax(dev_dax, NULL, NULL);
-        if (!dax_dev)
+        if (!dax_dev) {
+                rc = -ENOMEM;
                 goto err_dax;
+        }
 
         /* from here on we're committed to teardown via dax_dev_release() */
         dev = &dev_dax->dev;
@@ -620,7 +632,7 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
         dev->parent = parent;
         dev->groups = dax_attribute_groups;
         dev->release = dev_dax_release;
-        dev_set_name(dev, "dax%d.%d", dax_region->id, dev_dax->id);
+        dev_set_name(dev, "dax%d.%d", dax_region->id, id);
 
         rc = cdev_device_add(cdev, dev);
         if (rc) {
@@ -636,7 +648,8 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
         return dev_dax;
 
  err_dax:
-        ida_simple_remove(&dax_region->ida, dev_dax->id);
+        if (dev_dax->id >= 0)
+                ida_simple_remove(&dax_region->ida, dev_dax->id);
  err_id:
         kfree(dev_dax);
 
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index 9f2a0b4fd801..8d8c852ba8f2 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -58,13 +58,12 @@ static void dax_pmem_percpu_kill(void *data)
 
 static int dax_pmem_probe(struct device *dev)
 {
-        int rc;
         void *addr;
         struct resource res;
+        int rc, id, region_id;
         struct nd_pfn_sb *pfn_sb;
         struct dev_dax *dev_dax;
         struct dax_pmem *dax_pmem;
-        struct nd_region *nd_region;
         struct nd_namespace_io *nsio;
         struct dax_region *dax_region;
         struct nd_namespace_common *ndns;
@@ -123,14 +122,17 @@ static int dax_pmem_probe(struct device *dev)
         /* adjust the dax_region resource to the start of data */
         res.start += le64_to_cpu(pfn_sb->dataoff);
 
-        nd_region = to_nd_region(dev->parent);
-        dax_region = alloc_dax_region(dev, nd_region->id, &res,
+        rc = sscanf(dev_name(&ndns->dev), "namespace%d.%d", &region_id, &id);
+        if (rc != 2)
+                return -EINVAL;
+
+        dax_region = alloc_dax_region(dev, region_id, &res,
                         le32_to_cpu(pfn_sb->align), addr, PFN_DEV|PFN_MAP);
         if (!dax_region)
                 return -ENOMEM;
 
         /* TODO: support for subdividing a dax region... */
-        dev_dax = devm_create_dev_dax(dax_region, &res, 1);
+        dev_dax = devm_create_dev_dax(dax_region, id, &res, 1);
 
         /* child dev_dax instances now own the lifetime of the dax_region */
         dax_region_put(dax_region);