[PATCH v4 06/14] device-dax: ensure dev_dax->pgmap is valid for dynamic devices

[Joao Martins <joao.m.martins@oracle.com>]

Right now, only static dax regions have a valid @pgmap pointer in its
struct dev_dax. Dynamic dax case however, do not.

In preparation for device-dax compound devmap support, make sure that
dev_dax pgmap field is set after it has been allocated and initialized.

dynamic dax device have the @pgmap is allocated at probe() and it's
managed by devm (contrast to static dax region which a pgmap is provided
and dax core kfrees it). So in addition to ensure a valid @pgmap, clear
the pgmap when the dynamic dax device is released to avoid the same
pgmap ranges to be re-requested across multiple region device reconfigs.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 drivers/dax/bus.c    | 8 ++++++++
 drivers/dax/device.c | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 6cc4da4c713d..49dbff9ba609 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -363,6 +363,14 @@ void kill_dev_dax(struct dev_dax *dev_dax)
 
 	kill_dax(dax_dev);
 	unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+	/*
+	 * Dynamic dax region have the pgmap allocated via dev_kzalloc()
+	 * and thus freed by devm. Clear the pgmap to not have stale pgmap
+	 * ranges on probe() from previous reconfigurations of region devices.
+	 */
+	if (!is_static(dev_dax->region))
+		dev_dax->pgmap = NULL;
 }
 EXPORT_SYMBOL_GPL(kill_dev_dax);
 
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 0b82159b3564..6e348b5f9d45 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -426,6 +426,8 @@ int dev_dax_probe(struct dev_dax *dev_dax)
 	}
 
 	pgmap->type = MEMORY_DEVICE_GENERIC;
+	dev_dax->pgmap = pgmap;
+
 	addr = devm_memremap_pages(dev, pgmap);
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);
-- 
2.17.1