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Date: Wed, 13 Dec 2017 16:11:44 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Scott Bauer <scott.bauer@...el.com>, dm-devel@...hat.com
Cc: snitzer@...hat.com, agk@...hat.com, linux-kernel@...r.kernel.org,
keith.busch@...el.com, jonathan.derrick@...el.com
Subject: Re: [PATCH v3 1/2] dm-unstripe: unstripe RAID 0/dm-striped device
On 12/13/2017 01:33 PM, Scott Bauer wrote:
> 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@...el.com>
> Acked-by: Keith Busch <keith.busch@...el.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.
Please use tabs (consistenly) at the beginning of each line (after "config").
> +
> + If unsure say N.
> +
> config DM_CRYPT
> tristate "Crypt target support"
> depends on BLK_DEV_DM
> 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@...el.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;
Did you build this on 32-bit also? Is that '%' OK on 32-bit?
> +
> + if (ti->len == 1)
> + ti->len = (tot_sec / tot_drives) - mod;
> + ti->begin = 0;
> + return 0;
> +}
--
~Randy
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