dm-stripe.c revision 6f3c3f0afa50782dc1742c968646c491657d255a 
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#include <linux/log2.h>
15
16#define DM_MSG_PREFIX "striped"
17
18struct stripe {
19	struct dm_dev *dev;
20	sector_t physical_start;
21};
22
23struct stripe_c {
24	uint32_t stripes;
25
26	/* The size of this target / num. stripes */
27	sector_t stripe_width;
28
29	/* stripe chunk size */
30	uint32_t chunk_shift;
31	sector_t chunk_mask;
32
33	struct stripe stripe[0];
34};
35
36static inline struct stripe_c *alloc_context(unsigned int stripes)
37{
38	size_t len;
39
40	if (array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
41			  stripes))
42		return NULL;
43
44	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
45
46	return kmalloc(len, GFP_KERNEL);
47}
48
49/*
50 * Parse a single <dev> <sector> pair
51 */
52static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
53		      unsigned int stripe, char **argv)
54{
55	unsigned long long start;
56
57	if (sscanf(argv[1], "%llu", &start) != 1)
58		return -EINVAL;
59
60	if (dm_get_device(ti, argv[0], start, sc->stripe_width,
61			  dm_table_get_mode(ti->table),
62			  &sc->stripe[stripe].dev))
63		return -ENXIO;
64
65	sc->stripe[stripe].physical_start = start;
66	return 0;
67}
68
69/*
70 * Construct a striped mapping.
71 * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
72 */
73static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
74{
75	struct stripe_c *sc;
76	sector_t width;
77	uint32_t stripes;
78	uint32_t chunk_size;
79	char *end;
80	int r;
81	unsigned int i;
82
83	if (argc < 2) {
84		ti->error = "Not enough arguments";
85		return -EINVAL;
86	}
87
88	stripes = simple_strtoul(argv[0], &end, 10);
89	if (*end) {
90		ti->error = "Invalid stripe count";
91		return -EINVAL;
92	}
93
94	chunk_size = simple_strtoul(argv[1], &end, 10);
95	if (*end) {
96		ti->error = "Invalid chunk_size";
97		return -EINVAL;
98	}
99
100	/*
101	 * chunk_size is a power of two
102	 */
103	if (!is_power_of_2(chunk_size) ||
104	    (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
105		ti->error = "Invalid chunk size";
106		return -EINVAL;
107	}
108
109	if (ti->len & (chunk_size - 1)) {
110		ti->error = "Target length not divisible by "
111		    "chunk size";
112		return -EINVAL;
113	}
114
115	width = ti->len;
116	if (sector_div(width, stripes)) {
117		ti->error = "Target length not divisible by "
118		    "number of stripes";
119		return -EINVAL;
120	}
121
122	/*
123	 * Do we have enough arguments for that many stripes ?
124	 */
125	if (argc != (2 + 2 * stripes)) {
126		ti->error = "Not enough destinations "
127			"specified";
128		return -EINVAL;
129	}
130
131	sc = alloc_context(stripes);
132	if (!sc) {
133		ti->error = "Memory allocation for striped context "
134		    "failed";
135		return -ENOMEM;
136	}
137
138	sc->stripes = stripes;
139	sc->stripe_width = width;
140	ti->split_io = chunk_size;
141
142	sc->chunk_mask = ((sector_t) chunk_size) - 1;
143	for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++)
144		chunk_size >>= 1;
145	sc->chunk_shift--;
146
147	/*
148	 * Get the stripe destinations.
149	 */
150	for (i = 0; i < stripes; i++) {
151		argv += 2;
152
153		r = get_stripe(ti, sc, i, argv);
154		if (r < 0) {
155			ti->error = "Couldn't parse stripe destination";
156			while (i--)
157				dm_put_device(ti, sc->stripe[i].dev);
158			kfree(sc);
159			return r;
160		}
161	}
162
163	ti->private = sc;
164	return 0;
165}
166
167static void stripe_dtr(struct dm_target *ti)
168{
169	unsigned int i;
170	struct stripe_c *sc = (struct stripe_c *) ti->private;
171
172	for (i = 0; i < sc->stripes; i++)
173		dm_put_device(ti, sc->stripe[i].dev);
174
175	kfree(sc);
176}
177
178static int stripe_map(struct dm_target *ti, struct bio *bio,
179		      union map_info *map_context)
180{
181	struct stripe_c *sc = (struct stripe_c *) ti->private;
182
183	sector_t offset = bio->bi_sector - ti->begin;
184	sector_t chunk = offset >> sc->chunk_shift;
185	uint32_t stripe = sector_div(chunk, sc->stripes);
186
187	bio->bi_bdev = sc->stripe[stripe].dev->bdev;
188	bio->bi_sector = sc->stripe[stripe].physical_start +
189	    (chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
190	return DM_MAPIO_REMAPPED;
191}
192
193static int stripe_status(struct dm_target *ti,
194			 status_type_t type, char *result, unsigned int maxlen)
195{
196	struct stripe_c *sc = (struct stripe_c *) ti->private;
197	unsigned int sz = 0;
198	unsigned int i;
199
200	switch (type) {
201	case STATUSTYPE_INFO:
202		result[0] = '\0';
203		break;
204
205	case STATUSTYPE_TABLE:
206		DMEMIT("%d %llu", sc->stripes,
207			(unsigned long long)sc->chunk_mask + 1);
208		for (i = 0; i < sc->stripes; i++)
209			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
210			    (unsigned long long)sc->stripe[i].physical_start);
211		break;
212	}
213	return 0;
214}
215
216static struct target_type stripe_target = {
217	.name   = "striped",
218	.version= {1, 0, 2},
219	.module = THIS_MODULE,
220	.ctr    = stripe_ctr,
221	.dtr    = stripe_dtr,
222	.map    = stripe_map,
223	.status = stripe_status,
224};
225
226int __init dm_stripe_init(void)
227{
228	int r;
229
230	r = dm_register_target(&stripe_target);
231	if (r < 0)
232		DMWARN("target registration failed");
233
234	return r;
235}
236
237void dm_stripe_exit(void)
238{
239	if (dm_unregister_target(&stripe_target))
240		DMWARN("target unregistration failed");
241
242	return;
243}
244