[PATCH v5 16/17] dax/hmem: introduce dax_hmem.region_idle parameter

[Dan Williams]

From: Joao Martins <joao.m.martins@xxxxxxxxxx>

Introduce a new module parameter for dax_hmem which initializes all region
devices as free, rather than allocating a pagemap for the region by
default.

All hmem devices created with dax_hmem.region_idle=1 will have full
available size for creating dynamic dax devices.

Link: https://lkml.kernel.org/r/159643106460.4062302.5868522341307530091.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20200716172913.19658-4-joao.m.martins@xxxxxxxxxx
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 drivers/dax/hmem/hmem.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
index 1a3347bb6143..1bf040dbc834 100644
--- a/drivers/dax/hmem/hmem.c
+++ b/drivers/dax/hmem/hmem.c
@@ -5,6 +5,9 @@
 #include <linux/pfn_t.h>
 #include "../bus.h"
 
+static bool region_idle;
+module_param_named(region_idle, region_idle, bool, 0644);
+
 static int dax_hmem_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -30,7 +33,7 @@ static int dax_hmem_probe(struct platform_device *pdev)
 	data = (struct dev_dax_data) {
 		.dax_region = dax_region,
 		.id = -1,
-		.size = resource_size(res),
+		.size = region_idle ? 0 : resource_size(res),
 	};
 	dev_dax = devm_create_dev_dax(&data);
 	if (IS_ERR(dev_dax))