4 files changed, 37 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);
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index ce9e563e6e1d..938eb4868f7f 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -278,6 +278,12 @@ void dax_write_cache(struct dax_device *dax_dev, bool wc)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache);
 
+bool dax_write_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
 	lockdep_assert_held(&dax_srcu);