Root/drivers/md/dm-linear.c

1/*
2 * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm.h"
8#include <linux/module.h>
9#include <linux/init.h>
10#include <linux/blkdev.h>
11#include <linux/bio.h>
12#include <linux/slab.h>
13#include <linux/device-mapper.h>
14
15#define DM_MSG_PREFIX "linear"
16
17/*
18 * Linear: maps a linear range of a device.
19 */
20struct linear_c {
21    struct dm_dev *dev;
22    sector_t start;
23};
24
25/*
26 * Construct a linear mapping: <dev_path> <offset>
27 */
28static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
29{
30    struct linear_c *lc;
31    unsigned long long tmp;
32    char dummy;
33
34    if (argc != 2) {
35        ti->error = "Invalid argument count";
36        return -EINVAL;
37    }
38
39    lc = kmalloc(sizeof(*lc), GFP_KERNEL);
40    if (lc == NULL) {
41        ti->error = "dm-linear: Cannot allocate linear context";
42        return -ENOMEM;
43    }
44
45    if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1) {
46        ti->error = "dm-linear: Invalid device sector";
47        goto bad;
48    }
49    lc->start = tmp;
50
51    if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev)) {
52        ti->error = "dm-linear: Device lookup failed";
53        goto bad;
54    }
55
56    ti->num_flush_bios = 1;
57    ti->num_discard_bios = 1;
58    ti->num_write_same_bios = 1;
59    ti->private = lc;
60    return 0;
61
62      bad:
63    kfree(lc);
64    return -EINVAL;
65}
66
67static void linear_dtr(struct dm_target *ti)
68{
69    struct linear_c *lc = (struct linear_c *) ti->private;
70
71    dm_put_device(ti, lc->dev);
72    kfree(lc);
73}
74
75static sector_t linear_map_sector(struct dm_target *ti, sector_t bi_sector)
76{
77    struct linear_c *lc = ti->private;
78
79    return lc->start + dm_target_offset(ti, bi_sector);
80}
81
82static void linear_map_bio(struct dm_target *ti, struct bio *bio)
83{
84    struct linear_c *lc = ti->private;
85
86    bio->bi_bdev = lc->dev->bdev;
87    if (bio_sectors(bio))
88        bio->bi_sector = linear_map_sector(ti, bio->bi_sector);
89}
90
91static int linear_map(struct dm_target *ti, struct bio *bio)
92{
93    linear_map_bio(ti, bio);
94
95    return DM_MAPIO_REMAPPED;
96}
97
98static void linear_status(struct dm_target *ti, status_type_t type,
99              unsigned status_flags, char *result, unsigned maxlen)
100{
101    struct linear_c *lc = (struct linear_c *) ti->private;
102
103    switch (type) {
104    case STATUSTYPE_INFO:
105        result[0] = '\0';
106        break;
107
108    case STATUSTYPE_TABLE:
109        snprintf(result, maxlen, "%s %llu", lc->dev->name,
110                (unsigned long long)lc->start);
111        break;
112    }
113}
114
115static int linear_ioctl(struct dm_target *ti, unsigned int cmd,
116            unsigned long arg)
117{
118    struct linear_c *lc = (struct linear_c *) ti->private;
119    struct dm_dev *dev = lc->dev;
120    int r = 0;
121
122    /*
123     * Only pass ioctls through if the device sizes match exactly.
124     */
125    if (lc->start ||
126        ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
127        r = scsi_verify_blk_ioctl(NULL, cmd);
128
129    return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
130}
131
132static int linear_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
133            struct bio_vec *biovec, int max_size)
134{
135    struct linear_c *lc = ti->private;
136    struct request_queue *q = bdev_get_queue(lc->dev->bdev);
137
138    if (!q->merge_bvec_fn)
139        return max_size;
140
141    bvm->bi_bdev = lc->dev->bdev;
142    bvm->bi_sector = linear_map_sector(ti, bvm->bi_sector);
143
144    return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
145}
146
147static int linear_iterate_devices(struct dm_target *ti,
148                  iterate_devices_callout_fn fn, void *data)
149{
150    struct linear_c *lc = ti->private;
151
152    return fn(ti, lc->dev, lc->start, ti->len, data);
153}
154
155static struct target_type linear_target = {
156    .name = "linear",
157    .version = {1, 2, 1},
158    .module = THIS_MODULE,
159    .ctr = linear_ctr,
160    .dtr = linear_dtr,
161    .map = linear_map,
162    .status = linear_status,
163    .ioctl = linear_ioctl,
164    .merge = linear_merge,
165    .iterate_devices = linear_iterate_devices,
166};
167
168int __init dm_linear_init(void)
169{
170    int r = dm_register_target(&linear_target);
171
172    if (r < 0)
173        DMERR("register failed %d", r);
174
175    return r;
176}
177
178void dm_linear_exit(void)
179{
180    dm_unregister_target(&linear_target);
181}
182

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