linux-kernel - [PATCH v4 13/14] seq_file: add seq_list_*

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Date:	Fri, 21 Jun 2013 08:58:21 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	viro@...iv.linux.org.uk, matthew@....cx, bfields@...ldses.org
Cc:	dhowells@...hat.com, sage@...tank.com, smfrench@...il.com,
	swhiteho@...hat.com, Trond.Myklebust@...app.com,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-afs@...ts.infradead.org, ceph-devel@...r.kernel.org,
	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
	cluster-devel@...hat.com, linux-nfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, piastryyy@...il.com
Subject: [PATCH v4 13/14] seq_file: add seq_list_*_percpu helpers

When we convert the file_lock_list to a set of percpu lists, we'll need
a way to iterate over them in order to output /proc/locks info. Add
some seq_list_*_percpu helpers to handle that.

Signed-off-by: Jeff Layton <jlayton@...hat.com>
Acked-by: J. Bruce Fields <bfields@...ldses.org>
---
 fs/seq_file.c            |   54 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/seq_file.h |    6 +++++
 2 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 774c1eb..3135c25 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 2da29ac..4e32edc 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
-- 
1.7.1

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