[PATCH v1 6/7] mtd: mtd_raid: introduce raid1 implementation

[Dongsheng Yang]

This is implementation of raid1, the main work of it
is to mapping logical address to physical address and
mapping physical address to logical address. That would
be used when we meet an error in reading and want to find
the mirror in raid1.

Signed-off-by: Dongsheng Yang <yangds.fnst at cn.fujitsu.com>
---
 drivers/mtd/mtd_raid/raid1.c | 156 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)
 create mode 100644 drivers/mtd/mtd_raid/raid1.c

diff --git a/drivers/mtd/mtd_raid/raid1.c b/drivers/mtd/mtd_raid/raid1.c
new file mode 100644
index 0000000..98c01bd
--- /dev/null
+++ b/drivers/mtd/mtd_raid/raid1.c
@@ -0,0 +1,156 @@
+/*
+ * This file is part of MTD RAID.
+ *
+ * Copyright (C) 2015 Dongsheng Yang. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * Authors: Dongsheng Yang <yangds.fnst at cn.fujitsu.com>
+ */
+
+/**
+ * This file implement raid1.
+ * RAID1:
+ *
+ * Flash A:
+ * 	------------------------------
+ * 	|  A1   |  A2   | ... |  An  |
+ * 	------------------------------
+ * Flash B:
+ * 	------------------------------
+ * 	|  B1   |  B2   | ... |  Bn  |
+ * 	------------------------------
+ * Flash C:
+ * 	------------------------------
+ * 	|  C1   |  C2   | ... |  Cn  |
+ * 	------------------------------
+ *
+ * RAID_SINGLE:
+ * 	------------------------------
+ * 	|  A1   |  A2   | ... |  An  |
+ * 	------------------------------
+ * 	------------------------------
+ * 	|  B1   |  B2   | ... |  Bn  | Mirror
+ * 	------------------------------
+ * 	------------------------------
+ * 	|  C1   |  C2   | ... |  Cn  | Mirror
+ * 	------------------------------
+ *
+ * C1 = B1 = A1. They store same data in three different flashes.
+ *
+ * Detail to see:
+ * https://en.wikipedia.org/wiki/Standard_RAID_levels
+ */
+
+#include <linux/slab.h>
+#include <linux/kthread.h>
+
+#include "mtd_raid.h"
+
+static int raid1_logical_to_physical(struct mtd_raid *raid, loff_t from, size_t len, int copy_num,
+			      int *devid, loff_t *subdev_off, size_t *size)
+{
+	*devid = copy_num;
+	*subdev_off = from;
+	*size = len;
+
+	return 0;
+}
+
+/**
+ * This function will convert the physical address to logical address.
+ */
+static int raid1_physical_to_logical(struct mtd_raid *raid, int devid, loff_t subdev_off, size_t size,
+				     loff_t *from, size_t *len)
+{
+	*from = subdev_off;
+	*len = size;
+
+	return 0;
+}
+
+struct mtd_raid *mtd_raid1_create(int *mtd_nums, int dev_count, size_t substripe_size)
+{
+	struct mtd_raid1 *raid1 = NULL;
+	struct mtd_raid *raid = NULL;
+
+	raid1 = kzalloc(sizeof(struct mtd_raid1) + sizeof(struct mtd_raid_dev) * dev_count, GFP_KERNEL);
+	if (!raid1)
+		goto out;
+
+	raid = &raid1->raid;
+	raid->raid_level = MTD_RAID_LEVEL_RAID1;
+	raid->ops = &mtd_raid1_ops;
+	raid->ncopies = dev_count;
+	raid->npebs_per_leb = 1;
+
+	return &raid1->raid;
+out:
+	return NULL;
+}
+
+static int raid1_init(struct mtd_raid *raid,
+			    int dev_count, size_t substripe_size)
+{
+	int ret = 0;
+	int i = 0;
+	int raid_id = 0;
+	struct mtd_info *mtd = &raid->mtd;
+	struct mtd_info *subdev = raid->devs[0].mtd;
+
+	raid_id = mtd_raid_list_register(MTD_RAID_LEVEL_RAID1, raid);
+	sprintf(raid->name, "mtd1-%d", raid_id);
+	mtd->name = raid->name;
+
+	/**
+	 * size and erasesize are same with subdev.
+	 */
+	mtd->size = subdev->size;
+	mtd->erasesize = subdev->erasesize;
+	for (i = 0; i < dev_count; i++) {
+		subdev = raid->devs[i].mtd;
+		if (mtd->size != subdev->size) {
+			pr_err("Incompatible size on \"%s\"",
+			       subdev->name);
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (mtd->erasesize != subdev->erasesize) {
+			pr_err("Incompatible erasesize on \"%s\"",
+			       subdev->name);
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+out:
+	return ret;
+}
+
+
+void raid1_destroy(struct mtd_raid *mtd_raid)
+{
+	struct mtd_raid1 *raid1 = MTD_RAID_RAID1(mtd_raid);
+
+	mtd_raid_list_unregister(&raid1->raid);
+	kfree(raid1);
+}
+
+const struct mtd_raid_operations mtd_raid1_ops = {
+	.init    = raid1_init,
+	.destroy = raid1_destroy,
+	.logical_to_physical = raid1_logical_to_physical,
+	.physical_to_logical = raid1_physical_to_logical,
+};
-- 
1.8.4.2