2 files changed, 60 insertions, 0 deletions

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 774c1eb7f1c9..3135c2525c76 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -921,3 +921,57 @@ struct hlist_node *seq_hlist_next_rcu(void *v,
                 return rcu_dereference(node->next);
 }
 EXPORT_SYMBOL(seq_hlist_next_rcu);
+
+/**
+ * seq_hlist_start_precpu - start an iteration of a percpu hlist array
+ * @head: pointer to percpu array of struct hlist_heads
+ * @cpu:  pointer to cpu "cursor"
+ * @pos:  start position of sequence
+ *
+ * Called at seq_file->op->start().
+ */
+struct hlist_node *
+seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
+{
+        struct hlist_node *node;
+
+        for_each_possible_cpu(*cpu) {
+                hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
+                        if (pos-- == 0)
+                                return node;
+                }
+        }
+        return NULL;
+}
+EXPORT_SYMBOL(seq_hlist_start_percpu);
+
+/**
+ * seq_hlist_next_percpu - move to the next position of the percpu hlist array
+ * @v:    pointer to current hlist_node
+ * @head: pointer to percpu array of struct hlist_heads
+ * @cpu:  pointer to cpu "cursor"
+ * @pos:  start position of sequence
+ *
+ * Called at seq_file->op->next().
+ */
+struct hlist_node *
+seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
+                        int *cpu, loff_t *pos)
+{
+        struct hlist_node *node = v;
+
+        ++*pos;
+
+        if (node->next)
+                return node->next;
+
+        for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
+             *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
+                struct hlist_head *bucket = per_cpu_ptr(head, *cpu);
+
+                if (!hlist_empty(bucket))
+                        return bucket->first;
+        }
+        return NULL;
+}
+EXPORT_SYMBOL(seq_hlist_next_percpu);
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 2da29ac178fc..4e32edc8f506 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -173,4 +173,10 @@ extern struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
 extern struct hlist_node *seq_hlist_next_rcu(void *v,
                                                    struct hlist_head *head,
                                                    loff_t *ppos);
+
+/* Helpers for iterating over per-cpu hlist_head-s in seq_files */
+extern struct hlist_node *seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos);
+
+extern struct hlist_node *seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head, int *cpu, loff_t *pos);
+
 #endif