dax, kmem: calculate abstract distance with general interface

Previously, a fixed abstract distance MEMTIER_DEFAULT_DAX_ADISTANCE is
used for slow memory type in kmem driver.  This limits the usage of kmem
driver, for example, it cannot be used for HBM (high bandwidth memory).

So, we use the general abstract distance calculation mechanism in kmem
drivers to get more accurate abstract distance on systems with proper
support.  The original MEMTIER_DEFAULT_DAX_ADISTANCE is used as fallback
only.

Now, multiple memory types may be managed by kmem.  These memory types are
put into the "kmem_memory_types" list and protected by
kmem_memory_type_lock.

Link: https://lkml.kernel.org/r/20230926060628.265989-5-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Bharata B Rao <bharata@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Rafael J Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/dax/kmem.c

@@ -49,14 +49,52 @@ struct dax_kmem_data {
 	struct resource *res[];
 };
 
-static struct memory_dev_type *dax_slowmem_type;
+static DEFINE_MUTEX(kmem_memory_type_lock);
+static LIST_HEAD(kmem_memory_types);
+
+static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
+{
+	bool found = false;
+	struct memory_dev_type *mtype;
+
+	mutex_lock(&kmem_memory_type_lock);
+	list_for_each_entry(mtype, &kmem_memory_types, list) {
+		if (mtype->adistance == adist) {
+			found = true;
+			break;
+		}
+	}
+	if (!found) {
+		mtype = alloc_memory_type(adist);
+		if (!IS_ERR(mtype))
+			list_add(&mtype->list, &kmem_memory_types);
+	}
+	mutex_unlock(&kmem_memory_type_lock);
+
+	return mtype;
+}
+
+static void kmem_put_memory_types(void)
+{
+	struct memory_dev_type *mtype, *mtn;
+
+	mutex_lock(&kmem_memory_type_lock);
+	list_for_each_entry_safe(mtype, mtn, &kmem_memory_types, list) {
+		list_del(&mtype->list);
+		put_memory_type(mtype);
+	}
+	mutex_unlock(&kmem_memory_type_lock);
+}
+
 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;
+	struct memory_dev_type *mtype;
 	int i, rc, mapped = 0;
 	int numa_node;
+	int adist = MEMTIER_DEFAULT_DAX_ADISTANCE;
 
 	/*
 	 * Ensure good NUMA information for the persistent memory.
@@ -71,6 +109,11 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		return -EINVAL;
 	}
 
+	mt_calc_adistance(numa_node, &adist);
+	mtype = kmem_find_alloc_memory_type(adist);
+	if (IS_ERR(mtype))
+		return PTR_ERR(mtype);
+
 	for (i = 0; i < dev_dax->nr_range; i++) {
 		struct range range;
 
@@ -88,7 +131,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
 		return -EINVAL;
 	}
 
-	init_node_memory_type(numa_node, dax_slowmem_type);
+	init_node_memory_type(numa_node, mtype);
 
 	rc = -ENOMEM;
 	data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
@@ -167,7 +210,7 @@ err_reg_mgid:
 err_res_name:
 	kfree(data);
 err_dax_kmem_data:
-	clear_node_memory_type(numa_node, dax_slowmem_type);
+	clear_node_memory_type(numa_node, mtype);
 	return rc;
 }
 
@@ -219,7 +262,7 @@ static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
 		 * for that. This implies this reference will be around
 		 * till next reboot.
 		 */
-		clear_node_memory_type(node, dax_slowmem_type);
+		clear_node_memory_type(node, NULL);
 	}
 }
 #else
@@ -251,12 +294,6 @@ static int __init dax_kmem_init(void)
 	if (!kmem_name)
 		return -ENOMEM;
 
-	dax_slowmem_type = alloc_memory_type(MEMTIER_DEFAULT_DAX_ADISTANCE);
-	if (IS_ERR(dax_slowmem_type)) {
-		rc = PTR_ERR(dax_slowmem_type);
-		goto err_dax_slowmem_type;
-	}
-
 	rc = dax_driver_register(&device_dax_kmem_driver);
 	if (rc)
 		goto error_dax_driver;
@@ -264,8 +301,7 @@ static int __init dax_kmem_init(void)
 	return rc;
 
 error_dax_driver:
-	put_memory_type(dax_slowmem_type);
-err_dax_slowmem_type:
+	kmem_put_memory_types();
 	kfree_const(kmem_name);
 	return rc;
 }
@@ -275,7 +311,7 @@ static void __exit dax_kmem_exit(void)
 	dax_driver_unregister(&device_dax_kmem_driver);
 	if (!any_hotremove_failed)
 		kfree_const(kmem_name);
-	put_memory_type(dax_slowmem_type);
+	kmem_put_memory_types();
 }
 
 MODULE_AUTHOR("Intel Corporation");

include/linux/memory-tiers.h

@@ -24,6 +24,8 @@ struct memory_tier;
 struct memory_dev_type {
 	/* list of memory types that are part of same tier as this type */
 	struct list_head tier_sibling;
+	/* list of memory types that are managed by one driver */
+	struct list_head list;
 	/* abstract distance for this specific memory type */
 	int adistance;
 	/* Nodes of same abstract distance */

mm/memory-tiers.c

@@ -586,13 +586,14 @@ EXPORT_SYMBOL_GPL(init_node_memory_type);
 void clear_node_memory_type(int node, struct memory_dev_type *memtype)
 {
 	mutex_lock(&memory_tier_lock);
-	if (node_memory_types[node].memtype == memtype)
+	if (node_memory_types[node].memtype == memtype || !memtype)
 		node_memory_types[node].map_count--;
 	/*
 	 * If we umapped all the attached devices to this node,
 	 * clear the node memory type.
 	 */
 	if (!node_memory_types[node].map_count) {
+		memtype = node_memory_types[node].memtype;
 		node_memory_types[node].memtype = NULL;
 		put_memory_type(memtype);
 	}