dm-stripe.c revision 4f7f5c675fd6bacaae3c67be44de872dcff0e3b7 
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#define DM_IO_ERROR_THRESHOLD 15
18
19struct stripe {
20	struct dm_dev *dev;
21	sector_t physical_start;
22
23	atomic_t error_count;
24};
25
26struct stripe_c {
27	uint32_t stripes;
28
29	/* The size of this target / num. stripes */
30	sector_t stripe_width;
31
32	/* stripe chunk size */
33	uint32_t chunk_shift;
34	sector_t chunk_mask;
35
36	/* Needed for handling events */
37	struct dm_target *ti;
38
39	/* Work struct used for triggering events*/
40	struct work_struct kstriped_ws;
41
42	struct stripe stripe[0];
43};
44
45static struct workqueue_struct *kstriped;
46
47/*
48 * An event is triggered whenever a drive
49 * drops out of a stripe volume.
50 */
51static void trigger_event(struct work_struct *work)
52{
53	struct stripe_c *sc = container_of(work, struct stripe_c, kstriped_ws);
54
55	dm_table_event(sc->ti->table);
56
57}
58
59static inline struct stripe_c *alloc_context(unsigned int stripes)
60{
61	size_t len;
62
63	if (array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
64			  stripes))
65		return NULL;
66
67	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
68
69	return kmalloc(len, GFP_KERNEL);
70}
71
72/*
73 * Parse a single <dev> <sector> pair
74 */
75static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
76		      unsigned int stripe, char **argv)
77{
78	unsigned long long start;
79
80	if (sscanf(argv[1], "%llu", &start) != 1)
81		return -EINVAL;
82
83	if (dm_get_device(ti, argv[0], start, sc->stripe_width,
84			  dm_table_get_mode(ti->table),
85			  &sc->stripe[stripe].dev))
86		return -ENXIO;
87
88	sc->stripe[stripe].physical_start = start;
89
90	return 0;
91}
92
93/*
94 * Construct a striped mapping.
95 * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
96 */
97static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
98{
99	struct stripe_c *sc;
100	sector_t width;
101	uint32_t stripes;
102	uint32_t chunk_size;
103	char *end;
104	int r;
105	unsigned int i;
106
107	if (argc < 2) {
108		ti->error = "Not enough arguments";
109		return -EINVAL;
110	}
111
112	stripes = simple_strtoul(argv[0], &end, 10);
113	if (*end) {
114		ti->error = "Invalid stripe count";
115		return -EINVAL;
116	}
117
118	chunk_size = simple_strtoul(argv[1], &end, 10);
119	if (*end) {
120		ti->error = "Invalid chunk_size";
121		return -EINVAL;
122	}
123
124	/*
125	 * chunk_size is a power of two
126	 */
127	if (!is_power_of_2(chunk_size) ||
128	    (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
129		ti->error = "Invalid chunk size";
130		return -EINVAL;
131	}
132
133	if (ti->len & (chunk_size - 1)) {
134		ti->error = "Target length not divisible by "
135		    "chunk size";
136		return -EINVAL;
137	}
138
139	width = ti->len;
140	if (sector_div(width, stripes)) {
141		ti->error = "Target length not divisible by "
142		    "number of stripes";
143		return -EINVAL;
144	}
145
146	/*
147	 * Do we have enough arguments for that many stripes ?
148	 */
149	if (argc != (2 + 2 * stripes)) {
150		ti->error = "Not enough destinations "
151			"specified";
152		return -EINVAL;
153	}
154
155	sc = alloc_context(stripes);
156	if (!sc) {
157		ti->error = "Memory allocation for striped context "
158		    "failed";
159		return -ENOMEM;
160	}
161
162	INIT_WORK(&sc->kstriped_ws, trigger_event);
163
164	/* Set pointer to dm target; used in trigger_event */
165	sc->ti = ti;
166
167	sc->stripes = stripes;
168	sc->stripe_width = width;
169	ti->split_io = chunk_size;
170
171	sc->chunk_mask = ((sector_t) chunk_size) - 1;
172	for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++)
173		chunk_size >>= 1;
174	sc->chunk_shift--;
175
176	/*
177	 * Get the stripe destinations.
178	 */
179	for (i = 0; i < stripes; i++) {
180		argv += 2;
181
182		r = get_stripe(ti, sc, i, argv);
183		if (r < 0) {
184			ti->error = "Couldn't parse stripe destination";
185			while (i--)
186				dm_put_device(ti, sc->stripe[i].dev);
187			kfree(sc);
188			return r;
189		}
190		atomic_set(&(sc->stripe[i].error_count), 0);
191	}
192
193	ti->private = sc;
194
195	return 0;
196}
197
198static void stripe_dtr(struct dm_target *ti)
199{
200	unsigned int i;
201	struct stripe_c *sc = (struct stripe_c *) ti->private;
202
203	for (i = 0; i < sc->stripes; i++)
204		dm_put_device(ti, sc->stripe[i].dev);
205
206	flush_workqueue(kstriped);
207	kfree(sc);
208}
209
210static int stripe_map(struct dm_target *ti, struct bio *bio,
211		      union map_info *map_context)
212{
213	struct stripe_c *sc = (struct stripe_c *) ti->private;
214
215	sector_t offset = bio->bi_sector - ti->begin;
216	sector_t chunk = offset >> sc->chunk_shift;
217	uint32_t stripe = sector_div(chunk, sc->stripes);
218
219	bio->bi_bdev = sc->stripe[stripe].dev->bdev;
220	bio->bi_sector = sc->stripe[stripe].physical_start +
221	    (chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
222	return DM_MAPIO_REMAPPED;
223}
224
225/*
226 * Stripe status:
227 *
228 * INFO
229 * #stripes [stripe_name <stripe_name>] [group word count]
230 * [error count 'A|D' <error count 'A|D'>]
231 *
232 * TABLE
233 * #stripes [stripe chunk size]
234 * [stripe_name physical_start <stripe_name physical_start>]
235 *
236 */
237
238static int stripe_status(struct dm_target *ti,
239			 status_type_t type, char *result, unsigned int maxlen)
240{
241	struct stripe_c *sc = (struct stripe_c *) ti->private;
242	char buffer[sc->stripes + 1];
243	unsigned int sz = 0;
244	unsigned int i;
245
246	switch (type) {
247	case STATUSTYPE_INFO:
248		DMEMIT("%d ", sc->stripes);
249		for (i = 0; i < sc->stripes; i++)  {
250			DMEMIT("%s ", sc->stripe[i].dev->name);
251			buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
252				'D' : 'A';
253		}
254		buffer[i] = '\0';
255		DMEMIT("1 %s", buffer);
256		break;
257
258	case STATUSTYPE_TABLE:
259		DMEMIT("%d %llu", sc->stripes,
260			(unsigned long long)sc->chunk_mask + 1);
261		for (i = 0; i < sc->stripes; i++)
262			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
263			    (unsigned long long)sc->stripe[i].physical_start);
264		break;
265	}
266	return 0;
267}
268
269static int stripe_end_io(struct dm_target *ti, struct bio *bio,
270			 int error, union map_info *map_context)
271{
272	unsigned i;
273	char major_minor[16];
274	struct stripe_c *sc = ti->private;
275
276	if (!error)
277		return 0; /* I/O complete */
278
279	if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
280		return error;
281
282	if (error == -EOPNOTSUPP)
283		return error;
284
285	memset(major_minor, 0, sizeof(major_minor));
286	sprintf(major_minor, "%d:%d",
287		bio->bi_bdev->bd_disk->major,
288		bio->bi_bdev->bd_disk->first_minor);
289
290	/*
291	 * Test to see which stripe drive triggered the event
292	 * and increment error count for all stripes on that device.
293	 * If the error count for a given device exceeds the threshold
294	 * value we will no longer trigger any further events.
295	 */
296	for (i = 0; i < sc->stripes; i++)
297		if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
298			atomic_inc(&(sc->stripe[i].error_count));
299			if (atomic_read(&(sc->stripe[i].error_count)) <
300			    DM_IO_ERROR_THRESHOLD)
301				queue_work(kstriped, &sc->kstriped_ws);
302		}
303
304	return error;
305}
306
307static struct target_type stripe_target = {
308	.name   = "striped",
309	.version = {1, 1, 0},
310	.module = THIS_MODULE,
311	.ctr    = stripe_ctr,
312	.dtr    = stripe_dtr,
313	.map    = stripe_map,
314	.end_io = stripe_end_io,
315	.status = stripe_status,
316};
317
318int __init dm_stripe_init(void)
319{
320	int r;
321
322	r = dm_register_target(&stripe_target);
323	if (r < 0)
324		DMWARN("target registration failed");
325
326	kstriped = create_singlethread_workqueue("kstriped");
327	if (!kstriped) {
328		DMERR("failed to create workqueue kstriped");
329		dm_unregister_target(&stripe_target);
330		return -ENOMEM;
331	}
332
333	return r;
334}
335
336void dm_stripe_exit(void)
337{
338	if (dm_unregister_target(&stripe_target))
339		DMWARN("target unregistration failed");
340
341	destroy_workqueue(kstriped);
342
343	return;
344}
345