[Devel] [PATCH 1/15] The helper functions itselves

[Pavel Emelianov]

Many places in kernel use seq_file API to iterate over a regular
list_head. The code for such iteration is identical in all the
places, so it's worth introducing a common helpers.

Signed-off-by: Pavel Emelianov <xemul at openvz.org>

---

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 0ac22af..49194a4 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -447,3 +447,37 @@ int seq_puts(struct seq_file *m, const c
 	return -1;
 }
 EXPORT_SYMBOL(seq_puts);
+
+struct list_head *seq_list_start(struct list_head *head, loff_t pos)
+{
+	struct list_head *lh;
+
+	list_for_each(lh, head)
+		if (pos-- == 0)
+			return lh;
+
+	return NULL;
+}
+
+EXPORT_SYMBOL(seq_list_start);
+
+struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
+{
+	if (!pos)
+		return head;
+
+	return seq_list_start(head, pos - 1);
+}
+
+EXPORT_SYMBOL(seq_list_start_head);
+
+struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
+{
+	struct list_head *lh;
+
+	lh = ((struct list_head *)v)->next;
+	++*ppos;
+	return lh == head ? NULL : lh;
+}
+
+EXPORT_SYMBOL(seq_list_next);
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 3e3cccb..83783ab 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -50,5 +50,16 @@ int seq_release_private(struct inode *, 
 
 #define SEQ_START_TOKEN ((void *)1)
 
+/*
+ * Helpers for iteration over list_head-s in seq_files
+ */
+
+extern struct list_head *seq_list_start(struct list_head *head,
+		loff_t pos);
+extern struct list_head *seq_list_start_head(struct list_head *head,
+		loff_t pos);
+extern struct list_head *seq_list_next(void *v, struct list_head *head,
+		loff_t *ppos);
+
 #endif
 #endif