tree: add attribute numa_nodes for NVMe path object

Add a new attribute named "numa_nodes" under the NVMe path object. This
attribute is used by the iopolicy "numa". The numa_nodes value is stored
for each NVMe path and represents the NUMA node(s) associated with it.
When the iopolicy is set to "numa", I/O traffic originating from a given
NUMA node will be forwarded through the corresponding NVMe path.

The numa_nodes attribute is useful for observing which NVMe path the
kernel would choose for I/O forwarding based on NUMA affinity. To support
this, export the attribute in libnvme.map so it can be accessed via
nvme-cli.

Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Nilay Shroff <[email protected]>
Signed-off-by: Daniel Wagner <[email protected]>

Author: shroffni

src/libnvme.map

@@ -327,6 +327,7 @@ LIBNVME_1_0 {
 		nvme_path_get_ctrl;
 		nvme_path_get_name;
 		nvme_path_get_ns;
+		nvme_path_get_numa_nodes;
 		nvme_path_get_queue_depth;
 		nvme_path_get_sysfs_dir;
 		nvme_paths_filter;

src/nvme/private.h

@@ -33,6 +33,7 @@ struct nvme_path {
 	char *name;
 	char *sysfs_dir;
 	char *ana_state;
+	char *numa_nodes;
 	int grpid;
 	int queue_depth;
 };

src/nvme/tree.c

@@ -925,13 +925,19 @@ const char *nvme_path_get_ana_state(nvme_path_t p)
 	return p->ana_state;
 }
 
+const char *nvme_path_get_numa_nodes(nvme_path_t p)
+{
+	return p->numa_nodes;
+}
+
 void nvme_free_path(struct nvme_path *p)
 {
 	list_del_init(&p->entry);
 	list_del_init(&p->nentry);
 	free(p->name);
 	free(p->sysfs_dir);
 	free(p->ana_state);
+	free(p->numa_nodes);
 	free(p);
 }
 
@@ -967,6 +973,10 @@ static int nvme_ctrl_scan_path(nvme_root_t r, struct nvme_ctrl *c, char *name)
 	if (!p->ana_state)
 		p->ana_state = strdup("optimized");
 
+	p->numa_nodes = nvme_get_path_attr(p, "numa_nodes");
+	if (!p->numa_nodes)
+		p->numa_nodes = strdup("-1");
+
 	grpid = nvme_get_path_attr(p, "ana_grpid");
 	if (grpid) {
 		sscanf(grpid, "%d", &p->grpid);

src/nvme/tree.h

@@ -867,6 +867,14 @@ const char *nvme_path_get_sysfs_dir(nvme_path_t p);
  */
 const char *nvme_path_get_ana_state(nvme_path_t p);
 
+/**
+ * nvme_path_get_numa_nodes() - NUMA nodes of an nvme_path_t object
+ * @p : &nvme_path_t object
+ *
+ * Return: NUMA nodes associated to @p
+ */
+const char *nvme_path_get_numa_nodes(nvme_path_t p);
+
 /**
  * nvme_path_get_queue_depth() - Queue depth of an nvme_path_t object
  * @p: &nvme_path_t object