dm-stripe.c revision 4ee218cd67b385759993a6c840ea45f0ee0a8b30 
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	unsigned long long start;
53
54	if (sscanf(argv[1], "%llu", &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	if (((uint32_t)ti->len) & (chunk_size - 1)) {
107		ti->error = "dm-stripe: Target length not divisible by "
108		    "chunk size";
109		return -EINVAL;
110	}
111
112	width = ti->len;
113	if (sector_div(width, stripes)) {
114		ti->error = "dm-stripe: Target length not divisible by "
115		    "number of stripes";
116		return -EINVAL;
117	}
118
119	/*
120	 * Do we have enough arguments for that many stripes ?
121	 */
122	if (argc != (2 + 2 * stripes)) {
123		ti->error = "dm-stripe: Not enough destinations "
124			"specified";
125		return -EINVAL;
126	}
127
128	sc = alloc_context(stripes);
129	if (!sc) {
130		ti->error = "dm-stripe: Memory allocation for striped context "
131		    "failed";
132		return -ENOMEM;
133	}
134
135	sc->stripes = stripes;
136	sc->stripe_width = width;
137	ti->split_io = chunk_size;
138
139	sc->chunk_mask = ((sector_t) chunk_size) - 1;
140	for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++)
141		chunk_size >>= 1;
142	sc->chunk_shift--;
143
144	/*
145	 * Get the stripe destinations.
146	 */
147	for (i = 0; i < stripes; i++) {
148		argv += 2;
149
150		r = get_stripe(ti, sc, i, argv);
151		if (r < 0) {
152			ti->error = "dm-stripe: Couldn't parse stripe "
153				"destination";
154			while (i--)
155				dm_put_device(ti, sc->stripe[i].dev);
156			kfree(sc);
157			return r;
158		}
159	}
160
161	ti->private = sc;
162	return 0;
163}
164
165static void stripe_dtr(struct dm_target *ti)
166{
167	unsigned int i;
168	struct stripe_c *sc = (struct stripe_c *) ti->private;
169
170	for (i = 0; i < sc->stripes; i++)
171		dm_put_device(ti, sc->stripe[i].dev);
172
173	kfree(sc);
174}
175
176static int stripe_map(struct dm_target *ti, struct bio *bio,
177		      union map_info *map_context)
178{
179	struct stripe_c *sc = (struct stripe_c *) ti->private;
180
181	sector_t offset = bio->bi_sector - ti->begin;
182	sector_t chunk = offset >> sc->chunk_shift;
183	uint32_t stripe = sector_div(chunk, sc->stripes);
184
185	bio->bi_bdev = sc->stripe[stripe].dev->bdev;
186	bio->bi_sector = sc->stripe[stripe].physical_start +
187	    (chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
188	return 1;
189}
190
191static int stripe_status(struct dm_target *ti,
192			 status_type_t type, char *result, unsigned int maxlen)
193{
194	struct stripe_c *sc = (struct stripe_c *) ti->private;
195	unsigned int sz = 0;
196	unsigned int i;
197
198	switch (type) {
199	case STATUSTYPE_INFO:
200		result[0] = '\0';
201		break;
202
203	case STATUSTYPE_TABLE:
204		DMEMIT("%d %llu", sc->stripes,
205			(unsigned long long)sc->chunk_mask + 1);
206		for (i = 0; i < sc->stripes; i++)
207			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
208			    (unsigned long long)sc->stripe[i].physical_start);
209		break;
210	}
211	return 0;
212}
213
214static struct target_type stripe_target = {
215	.name   = "striped",
216	.version= {1, 0, 2},
217	.module = THIS_MODULE,
218	.ctr    = stripe_ctr,
219	.dtr    = stripe_dtr,
220	.map    = stripe_map,
221	.status = stripe_status,
222};
223
224int __init dm_stripe_init(void)
225{
226	int r;
227
228	r = dm_register_target(&stripe_target);
229	if (r < 0)
230		DMWARN("striped target registration failed");
231
232	return r;
233}
234
235void dm_stripe_exit(void)
236{
237	if (dm_unregister_target(&stripe_target))
238		DMWARN("striped target unregistration failed");
239
240	return;
241}
242