ab4c142488
Implement barrier support for single device DM devices
This patch implements barrier support in DM for the common case of dm linear
just remapping a single underlying device. In this case we can safely
pass the barrier through because there can be no reordering between
devices.
NB. Any DM device might cease to support barriers if it gets
reconfigured so code must continue to allow for a possible
-EOPNOTSUPP on every barrier bio submitted. - agk
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
161 lines
3.3 KiB
C
161 lines
3.3 KiB
C
/*
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* Copyright (C) 2001-2003 Sistina Software (UK) Limited.
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*
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* This file is released under the GPL.
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*/
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#include "dm.h"
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/blkdev.h>
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#include <linux/bio.h>
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#include <linux/slab.h>
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#include <linux/device-mapper.h>
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#define DM_MSG_PREFIX "linear"
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/*
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* Linear: maps a linear range of a device.
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*/
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struct linear_c {
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struct dm_dev *dev;
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sector_t start;
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};
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/*
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* Construct a linear mapping: <dev_path> <offset>
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*/
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static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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{
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struct linear_c *lc;
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unsigned long long tmp;
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if (argc != 2) {
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ti->error = "Invalid argument count";
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return -EINVAL;
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}
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lc = kmalloc(sizeof(*lc), GFP_KERNEL);
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if (lc == NULL) {
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ti->error = "dm-linear: Cannot allocate linear context";
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return -ENOMEM;
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}
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if (sscanf(argv[1], "%llu", &tmp) != 1) {
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ti->error = "dm-linear: Invalid device sector";
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goto bad;
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}
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lc->start = tmp;
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if (dm_get_device(ti, argv[0], lc->start, ti->len,
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dm_table_get_mode(ti->table), &lc->dev)) {
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ti->error = "dm-linear: Device lookup failed";
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goto bad;
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}
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ti->private = lc;
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return 0;
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bad:
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kfree(lc);
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return -EINVAL;
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}
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static void linear_dtr(struct dm_target *ti)
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{
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struct linear_c *lc = (struct linear_c *) ti->private;
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dm_put_device(ti, lc->dev);
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kfree(lc);
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}
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static sector_t linear_map_sector(struct dm_target *ti, sector_t bi_sector)
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{
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struct linear_c *lc = ti->private;
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return lc->start + (bi_sector - ti->begin);
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}
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static void linear_map_bio(struct dm_target *ti, struct bio *bio)
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{
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struct linear_c *lc = ti->private;
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bio->bi_bdev = lc->dev->bdev;
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bio->bi_sector = linear_map_sector(ti, bio->bi_sector);
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}
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static int linear_map(struct dm_target *ti, struct bio *bio,
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union map_info *map_context)
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{
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linear_map_bio(ti, bio);
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return DM_MAPIO_REMAPPED;
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}
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static int linear_status(struct dm_target *ti, status_type_t type,
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char *result, unsigned int maxlen)
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{
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struct linear_c *lc = (struct linear_c *) ti->private;
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switch (type) {
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case STATUSTYPE_INFO:
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result[0] = '\0';
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break;
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case STATUSTYPE_TABLE:
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snprintf(result, maxlen, "%s %llu", lc->dev->name,
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(unsigned long long)lc->start);
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break;
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}
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return 0;
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}
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static int linear_ioctl(struct dm_target *ti, unsigned int cmd,
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unsigned long arg)
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{
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struct linear_c *lc = (struct linear_c *) ti->private;
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return __blkdev_driver_ioctl(lc->dev->bdev, lc->dev->mode, cmd, arg);
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}
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static int linear_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
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struct bio_vec *biovec, int max_size)
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{
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struct linear_c *lc = ti->private;
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struct request_queue *q = bdev_get_queue(lc->dev->bdev);
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if (!q->merge_bvec_fn)
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return max_size;
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bvm->bi_bdev = lc->dev->bdev;
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bvm->bi_sector = linear_map_sector(ti, bvm->bi_sector);
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return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
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}
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static struct target_type linear_target = {
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.name = "linear",
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.version= {1, 0, 3},
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.module = THIS_MODULE,
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.ctr = linear_ctr,
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.dtr = linear_dtr,
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.map = linear_map,
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.status = linear_status,
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.ioctl = linear_ioctl,
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.merge = linear_merge,
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.features = DM_TARGET_SUPPORTS_BARRIERS,
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};
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int __init dm_linear_init(void)
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{
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int r = dm_register_target(&linear_target);
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if (r < 0)
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DMERR("register failed %d", r);
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return r;
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}
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void dm_linear_exit(void)
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{
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dm_unregister_target(&linear_target);
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}
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