Introduce the new helper nearest_node_nodemask() to find the closest
node in a specified nodemask from a given starting node.
Returns MAX_NUMNODES if no node is found.
Suggested-by: Yury Norov [NVIDIA] <yury.norov@xxxxxxxxx>
Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>
---
include/linux/numa.h | 7 +++++++
mm/mempolicy.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)
diff --git a/include/linux/numa.h b/include/linux/numa.h
index 31d8bf8a951a7..e6baaf6051bcf 100644
--- a/include/linux/numa.h
+++ b/include/linux/numa.h
@@ -31,6 +31,8 @@ void __init alloc_offline_node_data(int nid);
/* Generic implementation available */
int numa_nearest_node(int node, unsigned int state);
+int nearest_node_nodemask(int node, nodemask_t *mask);
+
#ifndef memory_add_physaddr_to_nid
int memory_add_physaddr_to_nid(u64 start);
#endif
@@ -47,6 +49,11 @@ static inline int numa_nearest_node(int node, unsigned int state)
return NUMA_NO_NODE;
}
+static inline int nearest_node_nodemask(int node, nodemask_t *mask)
+{
+ return NUMA_NO_NODE;
+}
+
static inline int memory_add_physaddr_to_nid(u64 start)
{
return 0;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 162407fbf2bc7..488cad280efb3 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -196,6 +196,37 @@ int numa_nearest_node(int node, unsigned int state)
}
EXPORT_SYMBOL_GPL(numa_nearest_node);
+/**
+ * nearest_node_nodemask - Find the node in @mask at the nearest distance
+ * from @node.
+ *
+ * @node: a valid node ID to start the search from.
+ * @mask: a pointer to a nodemask representing the allowed nodes.
+ *
+ * This function iterates over all nodes in @mask and calculates the
+ * distance from the starting @node, then it returns the node ID that is
+ * the closest to @node, or MAX_NUMNODES if no node is found.
+ *
+ * Note that @node must be a valid node ID usable with node_distance(),
+ * providing an invalid node ID (e.g., NUMA_NO_NODE) may result in crashes
+ * or unexpected behavior.
+ */
+int nearest_node_nodemask(int node, nodemask_t *mask)
+{
+ int dist, n, min_dist = INT_MAX, min_node = MAX_NUMNODES;
+
+ for_each_node_mask(n, *mask) {
+ dist = node_distance(node, n);
+ if (dist < min_dist) {
+ min_dist = dist;
+ min_node = n;
+ }
+ }
+
+ return min_node;
+}
+EXPORT_SYMBOL_GPL(nearest_node_nodemask);
+
struct mempolicy *get_task_policy(struct task_struct *p)
{
struct mempolicy *pol = p->mempolicy;
--
2.48.1
