dm-stripe.c revision 1f4e0ff07980820977f45d6a5dbc81d3bb9ce4d3 
1/*
2 * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
3 *
4 * This file is released under the GPL.
5 */
6
7#include <linux/device-mapper.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	int stripes_shift;
29
30	/* The size of this target / num. stripes */
31	sector_t stripe_width;
32
33	uint32_t chunk_size;
34	int chunk_size_shift;
35
36	/* Needed for handling events */
37	struct dm_target *ti;
38
39	/* Work struct used for triggering events*/
40	struct work_struct trigger_event;
41
42	struct stripe stripe[0];
43};
44
45/*
46 * An event is triggered whenever a drive
47 * drops out of a stripe volume.
48 */
49static void trigger_event(struct work_struct *work)
50{
51	struct stripe_c *sc = container_of(work, struct stripe_c,
52					   trigger_event);
53	dm_table_event(sc->ti->table);
54}
55
56static inline struct stripe_c *alloc_context(unsigned int stripes)
57{
58	size_t len;
59
60	if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
61			     stripes))
62		return NULL;
63
64	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
65
66	return kmalloc(len, GFP_KERNEL);
67}
68
69/*
70 * Parse a single <dev> <sector> pair
71 */
72static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
73		      unsigned int stripe, char **argv)
74{
75	unsigned long long start;
76	char dummy;
77
78	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
79		return -EINVAL;
80
81	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
82			  &sc->stripe[stripe].dev))
83		return -ENXIO;
84
85	sc->stripe[stripe].physical_start = start;
86
87	return 0;
88}
89
90/*
91 * Construct a striped mapping.
92 * <number of stripes> <chunk size> [<dev_path> <offset>]+
93 */
94static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
95{
96	struct stripe_c *sc;
97	sector_t width;
98	uint32_t stripes;
99	uint32_t chunk_size;
100	int r;
101	unsigned int i;
102
103	if (argc < 2) {
104		ti->error = "Not enough arguments";
105		return -EINVAL;
106	}
107
108	if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
109		ti->error = "Invalid stripe count";
110		return -EINVAL;
111	}
112
113	if (kstrtouint(argv[1], 10, &chunk_size) || !chunk_size) {
114		ti->error = "Invalid chunk_size";
115		return -EINVAL;
116	}
117
118	width = ti->len;
119	if (sector_div(width, chunk_size)) {
120		ti->error = "Target length not divisible by "
121		    "chunk size";
122		return -EINVAL;
123	}
124
125	if (sector_div(width, stripes)) {
126		ti->error = "Target length not divisible by "
127		    "number of stripes";
128		return -EINVAL;
129	}
130
131	/*
132	 * Do we have enough arguments for that many stripes ?
133	 */
134	if (argc != (2 + 2 * stripes)) {
135		ti->error = "Not enough destinations "
136			"specified";
137		return -EINVAL;
138	}
139
140	sc = alloc_context(stripes);
141	if (!sc) {
142		ti->error = "Memory allocation for striped context "
143		    "failed";
144		return -ENOMEM;
145	}
146
147	INIT_WORK(&sc->trigger_event, trigger_event);
148
149	/* Set pointer to dm target; used in trigger_event */
150	sc->ti = ti;
151	sc->stripes = stripes;
152	sc->stripe_width = width;
153
154	if (stripes & (stripes - 1))
155		sc->stripes_shift = -1;
156	else
157		sc->stripes_shift = __ffs(stripes);
158
159	r = dm_set_target_max_io_len(ti, chunk_size);
160	if (r)
161		return r;
162
163	ti->num_flush_requests = stripes;
164	ti->num_discard_requests = stripes;
165
166	sc->chunk_size = chunk_size;
167	if (chunk_size & (chunk_size - 1))
168		sc->chunk_size_shift = -1;
169	else
170		sc->chunk_size_shift = __ffs(chunk_size);
171
172	/*
173	 * Get the stripe destinations.
174	 */
175	for (i = 0; i < stripes; i++) {
176		argv += 2;
177
178		r = get_stripe(ti, sc, i, argv);
179		if (r < 0) {
180			ti->error = "Couldn't parse stripe destination";
181			while (i--)
182				dm_put_device(ti, sc->stripe[i].dev);
183			kfree(sc);
184			return r;
185		}
186		atomic_set(&(sc->stripe[i].error_count), 0);
187	}
188
189	ti->private = sc;
190
191	return 0;
192}
193
194static void stripe_dtr(struct dm_target *ti)
195{
196	unsigned int i;
197	struct stripe_c *sc = (struct stripe_c *) ti->private;
198
199	for (i = 0; i < sc->stripes; i++)
200		dm_put_device(ti, sc->stripe[i].dev);
201
202	flush_work_sync(&sc->trigger_event);
203	kfree(sc);
204}
205
206static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
207			      uint32_t *stripe, sector_t *result)
208{
209	sector_t chunk = dm_target_offset(sc->ti, sector);
210	sector_t chunk_offset;
211
212	if (sc->chunk_size_shift < 0)
213		chunk_offset = sector_div(chunk, sc->chunk_size);
214	else {
215		chunk_offset = chunk & (sc->chunk_size - 1);
216		chunk >>= sc->chunk_size_shift;
217	}
218
219	if (sc->stripes_shift < 0)
220		*stripe = sector_div(chunk, sc->stripes);
221	else {
222		*stripe = chunk & (sc->stripes - 1);
223		chunk >>= sc->stripes_shift;
224	}
225
226	if (sc->chunk_size_shift < 0)
227		chunk *= sc->chunk_size;
228	else
229		chunk <<= sc->chunk_size_shift;
230
231	*result = chunk + chunk_offset;
232}
233
234static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
235				    uint32_t target_stripe, sector_t *result)
236{
237	uint32_t stripe;
238
239	stripe_map_sector(sc, sector, &stripe, result);
240	if (stripe == target_stripe)
241		return;
242
243	/* round down */
244	sector = *result;
245	if (sc->chunk_size_shift < 0)
246		*result -= sector_div(sector, sc->chunk_size);
247	else
248		*result = sector & ~(sector_t)(sc->chunk_size - 1);
249
250	if (target_stripe < stripe)
251		*result += sc->chunk_size;		/* next chunk */
252}
253
254static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
255			      uint32_t target_stripe)
256{
257	sector_t begin, end;
258
259	stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
260	stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
261				target_stripe, &end);
262	if (begin < end) {
263		bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
264		bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
265		bio->bi_size = to_bytes(end - begin);
266		return DM_MAPIO_REMAPPED;
267	} else {
268		/* The range doesn't map to the target stripe */
269		bio_endio(bio, 0);
270		return DM_MAPIO_SUBMITTED;
271	}
272}
273
274static int stripe_map(struct dm_target *ti, struct bio *bio,
275		      union map_info *map_context)
276{
277	struct stripe_c *sc = ti->private;
278	uint32_t stripe;
279	unsigned target_request_nr;
280
281	if (bio->bi_rw & REQ_FLUSH) {
282		target_request_nr = map_context->target_request_nr;
283		BUG_ON(target_request_nr >= sc->stripes);
284		bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
285		return DM_MAPIO_REMAPPED;
286	}
287	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
288		target_request_nr = map_context->target_request_nr;
289		BUG_ON(target_request_nr >= sc->stripes);
290		return stripe_map_discard(sc, bio, target_request_nr);
291	}
292
293	stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
294
295	bio->bi_sector += sc->stripe[stripe].physical_start;
296	bio->bi_bdev = sc->stripe[stripe].dev->bdev;
297
298	return DM_MAPIO_REMAPPED;
299}
300
301/*
302 * Stripe status:
303 *
304 * INFO
305 * #stripes [stripe_name <stripe_name>] [group word count]
306 * [error count 'A|D' <error count 'A|D'>]
307 *
308 * TABLE
309 * #stripes [stripe chunk size]
310 * [stripe_name physical_start <stripe_name physical_start>]
311 *
312 */
313
314static int stripe_status(struct dm_target *ti, status_type_t type,
315			 unsigned status_flags, char *result, unsigned maxlen)
316{
317	struct stripe_c *sc = (struct stripe_c *) ti->private;
318	char buffer[sc->stripes + 1];
319	unsigned int sz = 0;
320	unsigned int i;
321
322	switch (type) {
323	case STATUSTYPE_INFO:
324		DMEMIT("%d ", sc->stripes);
325		for (i = 0; i < sc->stripes; i++)  {
326			DMEMIT("%s ", sc->stripe[i].dev->name);
327			buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
328				'D' : 'A';
329		}
330		buffer[i] = '\0';
331		DMEMIT("1 %s", buffer);
332		break;
333
334	case STATUSTYPE_TABLE:
335		DMEMIT("%d %llu", sc->stripes,
336			(unsigned long long)sc->chunk_size);
337		for (i = 0; i < sc->stripes; i++)
338			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
339			    (unsigned long long)sc->stripe[i].physical_start);
340		break;
341	}
342	return 0;
343}
344
345static int stripe_end_io(struct dm_target *ti, struct bio *bio,
346			 int error, union map_info *map_context)
347{
348	unsigned i;
349	char major_minor[16];
350	struct stripe_c *sc = ti->private;
351
352	if (!error)
353		return 0; /* I/O complete */
354
355	if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
356		return error;
357
358	if (error == -EOPNOTSUPP)
359		return error;
360
361	memset(major_minor, 0, sizeof(major_minor));
362	sprintf(major_minor, "%d:%d",
363		MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
364		MINOR(disk_devt(bio->bi_bdev->bd_disk)));
365
366	/*
367	 * Test to see which stripe drive triggered the event
368	 * and increment error count for all stripes on that device.
369	 * If the error count for a given device exceeds the threshold
370	 * value we will no longer trigger any further events.
371	 */
372	for (i = 0; i < sc->stripes; i++)
373		if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
374			atomic_inc(&(sc->stripe[i].error_count));
375			if (atomic_read(&(sc->stripe[i].error_count)) <
376			    DM_IO_ERROR_THRESHOLD)
377				schedule_work(&sc->trigger_event);
378		}
379
380	return error;
381}
382
383static int stripe_iterate_devices(struct dm_target *ti,
384				  iterate_devices_callout_fn fn, void *data)
385{
386	struct stripe_c *sc = ti->private;
387	int ret = 0;
388	unsigned i = 0;
389
390	do {
391		ret = fn(ti, sc->stripe[i].dev,
392			 sc->stripe[i].physical_start,
393			 sc->stripe_width, data);
394	} while (!ret && ++i < sc->stripes);
395
396	return ret;
397}
398
399static void stripe_io_hints(struct dm_target *ti,
400			    struct queue_limits *limits)
401{
402	struct stripe_c *sc = ti->private;
403	unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
404
405	blk_limits_io_min(limits, chunk_size);
406	blk_limits_io_opt(limits, chunk_size * sc->stripes);
407}
408
409static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
410			struct bio_vec *biovec, int max_size)
411{
412	struct stripe_c *sc = ti->private;
413	sector_t bvm_sector = bvm->bi_sector;
414	uint32_t stripe;
415	struct request_queue *q;
416
417	stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
418
419	q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
420	if (!q->merge_bvec_fn)
421		return max_size;
422
423	bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
424	bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
425
426	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
427}
428
429static struct target_type stripe_target = {
430	.name   = "striped",
431	.version = {1, 5, 0},
432	.module = THIS_MODULE,
433	.ctr    = stripe_ctr,
434	.dtr    = stripe_dtr,
435	.map    = stripe_map,
436	.end_io = stripe_end_io,
437	.status = stripe_status,
438	.iterate_devices = stripe_iterate_devices,
439	.io_hints = stripe_io_hints,
440	.merge  = stripe_merge,
441};
442
443int __init dm_stripe_init(void)
444{
445	int r;
446
447	r = dm_register_target(&stripe_target);
448	if (r < 0) {
449		DMWARN("target registration failed");
450		return r;
451	}
452
453	return r;
454}
455
456void dm_stripe_exit(void)
457{
458	dm_unregister_target(&stripe_target);
459}
460