[PATCH v3 6/9] dax/kmem: use a single static memory group for a single probed unit

[David Hildenbrand <david@xxxxxxxxxx>]

Although dax/kmem users often disable auto-onlining and instead online
memory manually (usually to ZONE_MOVABLE), there is still value in
having auto-onlining be aware of the relationship of memory blocks.

Let's treat one probed unit as a single static memory device, similar to
a single ACPI memory device.

Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 drivers/dax/kmem.c | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 99e0f60c4c26..a37622060fff 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -37,15 +37,16 @@ static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
 
 struct dax_kmem_data {
 	const char *res_name;
+	int mgid;
 	struct resource *res[];
 };
 
 static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 {
 	struct device *dev = &dev_dax->dev;
+	unsigned long total_len = 0;
 	struct dax_kmem_data *data;
-	int rc = -ENOMEM;
-	int i, mapped = 0;
+	int i, rc, mapped = 0;
 	int numa_node;
 
 	/*
@@ -61,24 +62,44 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		return -EINVAL;
 	}
 
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct range range;
+
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc) {
+			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
+					i, range.start, range.end);
+			continue;
+		}
+		total_len += range_len(&range);
+	}
+
+	if (!total_len) {
+		dev_warn(dev, "rejecting DAX region without any memory after alignment\n");
+		return -EINVAL;
+	}
+
 	data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
 
+	rc = -ENOMEM;
 	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
 	if (!data->res_name)
 		goto err_res_name;
 
+	rc = memory_group_register_static(numa_node, total_len);
+	if (rc < 0)
+		goto err_reg_mgid;
+	data->mgid = rc;
+
 	for (i = 0; i < dev_dax->nr_range; i++) {
 		struct resource *res;
 		struct range range;
 
 		rc = dax_kmem_range(dev_dax, i, &range);
-		if (rc) {
-			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
-					i, range.start, range.end);
+		if (rc)
 			continue;
-		}
 
 		/* Region is permanently reserved if hotremove fails. */
 		res = request_mem_region(range.start, range_len(&range), data->res_name);
@@ -108,8 +129,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		 * Ensure that future kexec'd kernels will not treat
 		 * this as RAM automatically.
 		 */
-		rc = add_memory_driver_managed(numa_node, range.start,
-				range_len(&range), kmem_name, MHP_NONE);
+		rc = add_memory_driver_managed(data->mgid, range.start,
+				range_len(&range), kmem_name, MHP_NID_IS_MGID);
 
 		if (rc) {
 			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
@@ -129,6 +150,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 	return 0;
 
 err_request_mem:
+	memory_group_unregister(data->mgid);
+err_reg_mgid:
 	kfree(data->res_name);
 err_res_name:
 	kfree(data);
@@ -171,6 +194,7 @@ static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
 	}
 
 	if (success >= dev_dax->nr_range) {
+		memory_group_unregister(data->mgid);
 		kfree(data->res_name);
 		kfree(data);
 		dev_set_drvdata(dev, NULL);
-- 
2.31.1