Lift the bio_list code from dm-raid1.c into dm-bio-list.h

[Christophe Saout]
--- diff/drivers/md/dm-bio-list.h	1970-01-01 01:00:00.000000000 +0100
+++ source/drivers/md/dm-bio-list.h	2004-01-16 13:56:34.000000000 +0000
@@ -0,0 +1,70 @@
+/*
+ * bio queue functions
+ *
+ * Copyright (C) 2001, 2002 Sistina Software
+ *
+ * This file is released under the LGPL.
+ */
+
+#ifndef DM_BIO_LIST_H
+#define DM_BIO_LIST_H
+
+#include <linux/bio.h>
+
+struct bio_list {
+	struct bio *head;
+	struct bio *tail;
+};
+
+extern inline void bio_list_init(struct bio_list *bl)
+{
+	bl->head = bl->tail = NULL;
+}
+
+extern inline void bio_list_add(struct bio_list *bl, struct bio *bio)
+{
+	bio->bi_next = NULL;
+
+	if (bl->tail)
+		bl->tail->bi_next = bio;
+	else
+		bl->head = bio;
+
+	bl->tail = bio;
+}
+
+extern inline void bio_list_merge(struct bio_list *bl, struct bio_list *bl2)
+{
+	if (bl->tail)
+		bl->tail->bi_next = bl2->head;
+	else
+		bl->head = bl2->head;
+
+	bl->tail = bl2->tail;
+}
+
+extern inline struct bio *bio_list_pop(struct bio_list *bl)
+{
+	struct bio *bio = bl->head;
+
+	if (bio) {
+		bl->head = bl->head->bi_next;
+		if (!bl->head)
+			bl->tail = NULL;
+
+		bio->bi_next = NULL;
+	}
+
+	return bio;
+}
+
+extern inline struct bio *bio_list_get(struct bio_list *bl)
+{
+	struct bio *bio = bl->head;
+
+	bl->head = bl->tail = NULL;
+
+	return bio;
+}
+
+#endif