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Subject[PATCH v3 1/2] dm-unstripe: unstripe RAID 0/dm-striped device
Date
This device mapper module remaps and unstripes IO so it lands
solely on a single drive in a RAID 0/dm-stripe target.
In a 4 drive RAID 0 the mapper exposes 1/4th of the LBA range
as a virtual drive. Each IO to that virtual drive will land on
only one of the 4 drives, selected by the user.

Signed-off-by: Scott Bauer <scott.bauer@intel.com>
Acked-by: Keith Busch <keith.busch@intel.com>
---
drivers/md/Kconfig | 10 +++
drivers/md/Makefile | 1 +
drivers/md/dm-unstripe.c | 204 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 215 insertions(+)
create mode 100644 drivers/md/dm-unstripe.c

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 83b9362be09c..948874fcc67c 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -269,6 +269,16 @@ config DM_BIO_PRISON

source "drivers/md/persistent-data/Kconfig"

+config DM_UN_STRIPE
+ tristate "Transpose IO to individual drives on a raid device"
+ depends on BLK_DEV_DM
+ ---help---
+ Enable this feature if you with to unstripe I/O on a RAID 0
+ device to the respective drive. If your hardware has physical
+ RAID 0 this module can unstripe the I/O to respective sides.
+
+ If unsure say N.
+
config DM_CRYPT
tristate "Crypt target support"
depends on BLK_DEV_DM
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index f701bb211783..2cc380b71319 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -43,6 +43,7 @@ obj-$(CONFIG_BCACHE) += bcache/
obj-$(CONFIG_BLK_DEV_MD) += md-mod.o
obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
obj-$(CONFIG_BLK_DEV_DM_BUILTIN) += dm-builtin.o
+obj-$(CONFIG_DM_UN_STRIPE) += dm-unstripe.o
obj-$(CONFIG_DM_BUFIO) += dm-bufio.o
obj-$(CONFIG_DM_BIO_PRISON) += dm-bio-prison.o
obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
diff --git a/drivers/md/dm-unstripe.c b/drivers/md/dm-unstripe.c
new file mode 100644
index 000000000000..d1105e92bb3f
--- /dev/null
+++ b/drivers/md/dm-unstripe.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright © 2017 Intel Corporation
+ *
+ * Authors:
+ * Scott Bauer <scott.bauer@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ */
+
+#include "dm.h"
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/device-mapper.h>
+
+
+struct unstripe {
+ struct dm_dev *ddisk;
+ sector_t chunk_sectors;
+ sector_t stripe_sectors;
+ u8 chunk_shift;
+ u8 cur_drive;
+};
+
+
+#define DM_MSG_PREFIX "dm-unstripe"
+static const char *parse_err = "Please provide the necessary information:"
+ "<drive> <device (0 indexed)> <total_devices>"
+ " <chunk size in 512B sectors || 0 to use max hw sector size>";
+
+/*
+ * Argument layout:
+ * <drive> <stripe/drive to extract (0 indexed)>
+ * <total_devices> <chunk size in 512B sect>
+ */
+static int set_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+ struct block_device *bbdev;
+ struct unstripe *target;
+ unsigned int chunk_size;
+ u64 tot_sec, mod;
+ u8 cur_drive, tot_drives;
+ char dummy;
+ int ret;
+
+ if (argc != 4) {
+ DMERR("%s", parse_err);
+ return -EINVAL;
+ }
+
+ if (sscanf(argv[1], "%hhu%c", &cur_drive, &dummy) != 1 ||
+ sscanf(argv[2], "%hhu%c", &tot_drives, &dummy) != 1 ||
+ sscanf(argv[3], "%u%c", &chunk_size, &dummy) != 1) {
+ DMERR("%s", parse_err);
+ return -EINVAL;
+ }
+
+ if (tot_drives == 0 || (cur_drive > tot_drives && tot_drives > 1)) {
+ DMERR("Please provide a drive between [0,%hhu)", tot_drives);
+ return -EINVAL;
+ }
+
+ target = kzalloc(sizeof(*target), GFP_KERNEL);
+
+ if (!target) {
+ DMERR("Failed to allocate space for DM unstripe!");
+ return -ENOMEM;
+ }
+
+ ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
+ &target->ddisk);
+ if (ret) {
+ kfree(target);
+ DMERR("dm-unstripe dev lookup failure! for drive %s", argv[0]);
+ return ret;
+ }
+
+ bbdev = target->ddisk->bdev;
+
+ target->cur_drive = cur_drive;
+ if (chunk_size)
+ target->chunk_sectors = chunk_size;
+ else
+ target->chunk_sectors =
+ queue_max_hw_sectors(bdev_get_queue(bbdev));
+
+ target->stripe_sectors = (tot_drives - 1) * target->chunk_sectors;
+ target->chunk_shift = fls(target->chunk_sectors) - 1;
+
+ ret = dm_set_target_max_io_len(ti, target->chunk_sectors);
+ if (ret) {
+ dm_put_device(ti, target->ddisk);
+ kfree(target);
+ DMERR("Failed to set max io len!");
+ return ret;
+ }
+ ti->private = target;
+
+ tot_sec = i_size_read(bbdev->bd_inode) >> SECTOR_SHIFT;
+ mod = tot_sec % target->chunk_sectors;
+
+ if (ti->len == 1)
+ ti->len = (tot_sec / tot_drives) - mod;
+ ti->begin = 0;
+ return 0;
+}
+
+static void set_dtr(struct dm_target *ti)
+{
+ struct unstripe *target = ti->private;
+
+ dm_put_device(ti, target->ddisk);
+ kfree(target);
+}
+
+
+static sector_t map_to_core(struct dm_target *ti, struct bio *bio)
+{
+ struct unstripe *target = ti->private;
+ unsigned long long sec = bio->bi_iter.bi_sector;
+ unsigned long long group;
+
+ group = (sec >> target->chunk_shift);
+ /* Account for what drive we're operating on */
+ sec += (target->cur_drive * target->chunk_sectors);
+ /* Shift us up to the right "row" on the drive*/
+ sec += target->stripe_sectors * group;
+ return sec;
+}
+
+static int set_map_bio(struct dm_target *ti, struct bio *bio)
+{
+ struct unstripe *target = ti->private;
+
+ if (bio_sectors(bio))
+ bio->bi_iter.bi_sector = map_to_core(ti, bio);
+
+ bio_set_dev(bio, target->ddisk->bdev);
+ submit_bio(bio);
+ return DM_MAPIO_SUBMITTED;
+}
+
+static void set_iohints(struct dm_target *ti,
+ struct queue_limits *limits)
+{
+ struct unstripe *target = ti->private;
+ struct queue_limits *lim = &bdev_get_queue(target->ddisk->bdev)->limits;
+
+ blk_limits_io_min(limits, lim->io_min);
+ blk_limits_io_opt(limits, lim->io_opt);
+ limits->chunk_sectors = target->chunk_sectors;
+}
+
+static int set_iterate(struct dm_target *ti, iterate_devices_callout_fn fn,
+ void *data)
+{
+ struct unstripe *target = ti->private;
+
+ return fn(ti, target->ddisk, 0, ti->len, data);
+}
+
+static struct target_type iset_target = {
+ .name = "unstripe",
+ .version = {1, 0, 0},
+ .module = THIS_MODULE,
+ .ctr = set_ctr,
+ .dtr = set_dtr,
+ .map = set_map_bio,
+ .iterate_devices = set_iterate,
+ .io_hints = set_iohints,
+};
+
+static int __init dm_unstripe_init(void)
+{
+ int r = dm_register_target(&iset_target);
+
+ if (r < 0)
+ DMERR("register failed %d", r);
+
+ return r;
+}
+
+static void __exit dm_unstripe_exit(void)
+{
+ dm_unregister_target(&iset_target);
+}
+
+module_init(dm_unstripe_init);
+module_exit(dm_unstripe_exit);
+
+MODULE_DESCRIPTION(DM_NAME " DM unstripe");
+MODULE_ALIAS("dm-unstripe");
+MODULE_AUTHOR("Scott Bauer <scott.bauer@intel.com>");
+MODULE_LICENSE("GPL");
--
2.11.0
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