dm-stripe.c revision 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 
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
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/blkdev.h>
12#include <linux/bio.h>
13#include <linux/slab.h>
14
15struct stripe {
16	struct dm_dev *dev;
17	sector_t physical_start;
18};
19
20struct stripe_c {
21	uint32_t stripes;
22
23	/* The size of this target / num. stripes */
24	sector_t stripe_width;
25
26	/* stripe chunk size */
27	uint32_t chunk_shift;
28	sector_t chunk_mask;
29
30	struct stripe stripe[0];
31};
32
33static inline struct stripe_c *alloc_context(unsigned int stripes)
34{
35	size_t len;
36
37	if (array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
38			  stripes))
39		return NULL;
40
41	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
42
43	return kmalloc(len, GFP_KERNEL);
44}
45
46/*
47 * Parse a single <dev> <sector> pair
48 */
49static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
50		      unsigned int stripe, char **argv)
51{
52	sector_t start;
53
54	if (sscanf(argv[1], SECTOR_FORMAT, &start) != 1)
55		return -EINVAL;
56
57	if (dm_get_device(ti, argv[0], start, sc->stripe_width,
58			  dm_table_get_mode(ti->table),
59			  &sc->stripe[stripe].dev))
60		return -ENXIO;
61
62	sc->stripe[stripe].physical_start = start;
63	return 0;
64}
65
66/*
67 * Construct a striped mapping.
68 * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
69 */
70static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
71{
72	struct stripe_c *sc;
73	sector_t width;
74	uint32_t stripes;
75	uint32_t chunk_size;
76	char *end;
77	int r;
78	unsigned int i;
79
80	if (argc < 2) {
81		ti->error = "dm-stripe: Not enough arguments";
82		return -EINVAL;
83	}
84
85	stripes = simple_strtoul(argv[0], &end, 10);
86	if (*end) {
87		ti->error = "dm-stripe: Invalid stripe count";
88		return -EINVAL;
89	}
90
91	chunk_size = simple_strtoul(argv[1], &end, 10);
92	if (*end) {
93		ti->error = "dm-stripe: Invalid chunk_size";
94		return -EINVAL;
95	}
96
97	/*
98	 * chunk_size is a power of two
99	 */
100	if (!chunk_size || (chunk_size & (chunk_size - 1)) ||
101	    (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
102		ti->error = "dm-stripe: Invalid chunk size";
103		return -EINVAL;
104	}
105
106	width = ti->len;
107	if (sector_div(width, stripes)) {
108		ti->error = "dm-stripe: Target length not divisable by "
109		    "number of stripes";
110		return -EINVAL;
111	}
112
113	/*
114	 * Do we have enough arguments for that many stripes ?
115	 */
116	if (argc != (2 + 2 * stripes)) {
117		ti->error = "dm-stripe: Not enough destinations "
118			"specified";
119		return -EINVAL;
120	}
121
122	sc = alloc_context(stripes);
123	if (!sc) {
124		ti->error = "dm-stripe: Memory allocation for striped context "
125		    "failed";
126		return -ENOMEM;
127	}
128
129	sc->stripes = stripes;
130	sc->stripe_width = width;
131	ti->split_io = chunk_size;
132
133	sc->chunk_mask = ((sector_t) chunk_size) - 1;
134	for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++)
135		chunk_size >>= 1;
136	sc->chunk_shift--;
137
138	/*
139	 * Get the stripe destinations.
140	 */
141	for (i = 0; i < stripes; i++) {
142		argv += 2;
143
144		r = get_stripe(ti, sc, i, argv);
145		if (r < 0) {
146			ti->error = "dm-stripe: Couldn't parse stripe "
147				"destination";
148			while (i--)
149				dm_put_device(ti, sc->stripe[i].dev);
150			kfree(sc);
151			return r;
152		}
153	}
154
155	ti->private = sc;
156	return 0;
157}
158
159static void stripe_dtr(struct dm_target *ti)
160{
161	unsigned int i;
162	struct stripe_c *sc = (struct stripe_c *) ti->private;
163
164	for (i = 0; i < sc->stripes; i++)
165		dm_put_device(ti, sc->stripe[i].dev);
166
167	kfree(sc);
168}
169
170static int stripe_map(struct dm_target *ti, struct bio *bio,
171		      union map_info *map_context)
172{
173	struct stripe_c *sc = (struct stripe_c *) ti->private;
174
175	sector_t offset = bio->bi_sector - ti->begin;
176	sector_t chunk = offset >> sc->chunk_shift;
177	uint32_t stripe = sector_div(chunk, sc->stripes);
178
179	bio->bi_bdev = sc->stripe[stripe].dev->bdev;
180	bio->bi_sector = sc->stripe[stripe].physical_start +
181	    (chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
182	return 1;
183}
184
185static int stripe_status(struct dm_target *ti,
186			 status_type_t type, char *result, unsigned int maxlen)
187{
188	struct stripe_c *sc = (struct stripe_c *) ti->private;
189	unsigned int sz = 0;
190	unsigned int i;
191
192	switch (type) {
193	case STATUSTYPE_INFO:
194		result[0] = '\0';
195		break;
196
197	case STATUSTYPE_TABLE:
198		DMEMIT("%d " SECTOR_FORMAT, sc->stripes, sc->chunk_mask + 1);
199		for (i = 0; i < sc->stripes; i++)
200			DMEMIT(" %s " SECTOR_FORMAT, sc->stripe[i].dev->name,
201			       sc->stripe[i].physical_start);
202		break;
203	}
204	return 0;
205}
206
207static struct target_type stripe_target = {
208	.name   = "striped",
209	.version= {1, 0, 2},
210	.module = THIS_MODULE,
211	.ctr    = stripe_ctr,
212	.dtr    = stripe_dtr,
213	.map    = stripe_map,
214	.status = stripe_status,
215};
216
217int __init dm_stripe_init(void)
218{
219	int r;
220
221	r = dm_register_target(&stripe_target);
222	if (r < 0)
223		DMWARN("striped target registration failed");
224
225	return r;
226}
227
228void dm_stripe_exit(void)
229{
230	if (dm_unregister_target(&stripe_target))
231		DMWARN("striped target unregistration failed");
232
233	return;
234}
235