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#include <linux/device-mapper.h>
9
10#include <linux/module.h>
11#include <linux/init.h>
12#include <linux/blkdev.h>
13#include <linux/bio.h>
14#include <linux/slab.h>
15#include <linux/log2.h>
16
17#define DM_MSG_PREFIX "striped"
18#define DM_IO_ERROR_THRESHOLD 15
19
20struct stripe {
21	struct dm_dev *dev;
22	sector_t physical_start;
23
24	atomic_t error_count;
25};
26
27struct stripe_c {
28	uint32_t stripes;
29	int stripes_shift;
30
31	/* The size of this target / num. stripes */
32	sector_t stripe_width;
33
34	uint32_t chunk_size;
35	int chunk_size_shift;
36
37	/* Needed for handling events */
38	struct dm_target *ti;
39
40	/* Work struct used for triggering events*/
41	struct work_struct trigger_event;
42
43	struct stripe stripe[0];
44};
45
46/*
47 * An event is triggered whenever a drive
48 * drops out of a stripe volume.
49 */
50static void trigger_event(struct work_struct *work)
51{
52	struct stripe_c *sc = container_of(work, struct stripe_c,
53					   trigger_event);
54	dm_table_event(sc->ti->table);
55}
56
57static inline struct stripe_c *alloc_context(unsigned int stripes)
58{
59	size_t len;
60
61	if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
62			     stripes))
63		return NULL;
64
65	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
66
67	return kmalloc(len, GFP_KERNEL);
68}
69
70/*
71 * Parse a single <dev> <sector> pair
72 */
73static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
74		      unsigned int stripe, char **argv)
75{
76	unsigned long long start;
77	char dummy;
78
79	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
80		return -EINVAL;
81
82	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
83			  &sc->stripe[stripe].dev))
84		return -ENXIO;
85
86	sc->stripe[stripe].physical_start = start;
87
88	return 0;
89}
90
91/*
92 * Construct a striped mapping.
93 * <number of stripes> <chunk size> [<dev_path> <offset>]+
94 */
95static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
96{
97	struct stripe_c *sc;
98	sector_t width, tmp_len;
99	uint32_t stripes;
100	uint32_t chunk_size;
101	int r;
102	unsigned int i;
103
104	if (argc < 2) {
105		ti->error = "Not enough arguments";
106		return -EINVAL;
107	}
108
109	if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
110		ti->error = "Invalid stripe count";
111		return -EINVAL;
112	}
113
114	if (kstrtouint(argv[1], 10, &chunk_size) || !chunk_size) {
115		ti->error = "Invalid chunk_size";
116		return -EINVAL;
117	}
118
119	width = ti->len;
120	if (sector_div(width, stripes)) {
121		ti->error = "Target length not divisible by "
122		    "number of stripes";
123		return -EINVAL;
124	}
125
126	tmp_len = width;
127	if (sector_div(tmp_len, chunk_size)) {
128		ti->error = "Target length not divisible by "
129		    "chunk size";
130		return -EINVAL;
131	}
132
133	/*
134	 * Do we have enough arguments for that many stripes ?
135	 */
136	if (argc != (2 + 2 * stripes)) {
137		ti->error = "Not enough destinations "
138			"specified";
139		return -EINVAL;
140	}
141
142	sc = alloc_context(stripes);
143	if (!sc) {
144		ti->error = "Memory allocation for striped context "
145		    "failed";
146		return -ENOMEM;
147	}
148
149	INIT_WORK(&sc->trigger_event, trigger_event);
150
151	/* Set pointer to dm target; used in trigger_event */
152	sc->ti = ti;
153	sc->stripes = stripes;
154	sc->stripe_width = width;
155
156	if (stripes & (stripes - 1))
157		sc->stripes_shift = -1;
158	else
159		sc->stripes_shift = __ffs(stripes);
160
161	r = dm_set_target_max_io_len(ti, chunk_size);
162	if (r) {
163		kfree(sc);
164		return r;
165	}
166
167	ti->num_flush_bios = stripes;
168	ti->num_discard_bios = stripes;
169	ti->num_write_same_bios = stripes;
170
171	sc->chunk_size = chunk_size;
172	if (chunk_size & (chunk_size - 1))
173		sc->chunk_size_shift = -1;
174	else
175		sc->chunk_size_shift = __ffs(chunk_size);
176
177	/*
178	 * Get the stripe destinations.
179	 */
180	for (i = 0; i < stripes; i++) {
181		argv += 2;
182
183		r = get_stripe(ti, sc, i, argv);
184		if (r < 0) {
185			ti->error = "Couldn't parse stripe destination";
186			while (i--)
187				dm_put_device(ti, sc->stripe[i].dev);
188			kfree(sc);
189			return r;
190		}
191		atomic_set(&(sc->stripe[i].error_count), 0);
192	}
193
194	ti->private = sc;
195
196	return 0;
197}
198
199static void stripe_dtr(struct dm_target *ti)
200{
201	unsigned int i;
202	struct stripe_c *sc = (struct stripe_c *) ti->private;
203
204	for (i = 0; i < sc->stripes; i++)
205		dm_put_device(ti, sc->stripe[i].dev);
206
207	flush_work(&sc->trigger_event);
208	kfree(sc);
209}
210
211static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
212			      uint32_t *stripe, sector_t *result)
213{
214	sector_t chunk = dm_target_offset(sc->ti, sector);
215	sector_t chunk_offset;
216
217	if (sc->chunk_size_shift < 0)
218		chunk_offset = sector_div(chunk, sc->chunk_size);
219	else {
220		chunk_offset = chunk & (sc->chunk_size - 1);
221		chunk >>= sc->chunk_size_shift;
222	}
223
224	if (sc->stripes_shift < 0)
225		*stripe = sector_div(chunk, sc->stripes);
226	else {
227		*stripe = chunk & (sc->stripes - 1);
228		chunk >>= sc->stripes_shift;
229	}
230
231	if (sc->chunk_size_shift < 0)
232		chunk *= sc->chunk_size;
233	else
234		chunk <<= sc->chunk_size_shift;
235
236	*result = chunk + chunk_offset;
237}
238
239static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
240				    uint32_t target_stripe, sector_t *result)
241{
242	uint32_t stripe;
243
244	stripe_map_sector(sc, sector, &stripe, result);
245	if (stripe == target_stripe)
246		return;
247
248	/* round down */
249	sector = *result;
250	if (sc->chunk_size_shift < 0)
251		*result -= sector_div(sector, sc->chunk_size);
252	else
253		*result = sector & ~(sector_t)(sc->chunk_size - 1);
254
255	if (target_stripe < stripe)
256		*result += sc->chunk_size;		/* next chunk */
257}
258
259static int stripe_map_range(struct stripe_c *sc, struct bio *bio,
260			    uint32_t target_stripe)
261{
262	sector_t begin, end;
263
264	stripe_map_range_sector(sc, bio->bi_iter.bi_sector,
265				target_stripe, &begin);
266	stripe_map_range_sector(sc, bio_end_sector(bio),
267				target_stripe, &end);
268	if (begin < end) {
269		bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
270		bio->bi_iter.bi_sector = begin +
271			sc->stripe[target_stripe].physical_start;
272		bio->bi_iter.bi_size = to_bytes(end - begin);
273		return DM_MAPIO_REMAPPED;
274	} else {
275		/* The range doesn't map to the target stripe */
276		bio_endio(bio, 0);
277		return DM_MAPIO_SUBMITTED;
278	}
279}
280
281static int stripe_map(struct dm_target *ti, struct bio *bio)
282{
283	struct stripe_c *sc = ti->private;
284	uint32_t stripe;
285	unsigned target_bio_nr;
286
287	if (bio->bi_rw & REQ_FLUSH) {
288		target_bio_nr = dm_bio_get_target_bio_nr(bio);
289		BUG_ON(target_bio_nr >= sc->stripes);
290		bio->bi_bdev = sc->stripe[target_bio_nr].dev->bdev;
291		return DM_MAPIO_REMAPPED;
292	}
293	if (unlikely(bio->bi_rw & REQ_DISCARD) ||
294	    unlikely(bio->bi_rw & REQ_WRITE_SAME)) {
295		target_bio_nr = dm_bio_get_target_bio_nr(bio);
296		BUG_ON(target_bio_nr >= sc->stripes);
297		return stripe_map_range(sc, bio, target_bio_nr);
298	}
299
300	stripe_map_sector(sc, bio->bi_iter.bi_sector,
301			  &stripe, &bio->bi_iter.bi_sector);
302
303	bio->bi_iter.bi_sector += sc->stripe[stripe].physical_start;
304	bio->bi_bdev = sc->stripe[stripe].dev->bdev;
305
306	return DM_MAPIO_REMAPPED;
307}
308
309/*
310 * Stripe status:
311 *
312 * INFO
313 * #stripes [stripe_name <stripe_name>] [group word count]
314 * [error count 'A|D' <error count 'A|D'>]
315 *
316 * TABLE
317 * #stripes [stripe chunk size]
318 * [stripe_name physical_start <stripe_name physical_start>]
319 *
320 */
321
322static void stripe_status(struct dm_target *ti, status_type_t type,
323			  unsigned status_flags, char *result, unsigned maxlen)
324{
325	struct stripe_c *sc = (struct stripe_c *) ti->private;
326	char buffer[sc->stripes + 1];
327	unsigned int sz = 0;
328	unsigned int i;
329
330	switch (type) {
331	case STATUSTYPE_INFO:
332		DMEMIT("%d ", sc->stripes);
333		for (i = 0; i < sc->stripes; i++)  {
334			DMEMIT("%s ", sc->stripe[i].dev->name);
335			buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
336				'D' : 'A';
337		}
338		buffer[i] = '\0';
339		DMEMIT("1 %s", buffer);
340		break;
341
342	case STATUSTYPE_TABLE:
343		DMEMIT("%d %llu", sc->stripes,
344			(unsigned long long)sc->chunk_size);
345		for (i = 0; i < sc->stripes; i++)
346			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
347			    (unsigned long long)sc->stripe[i].physical_start);
348		break;
349	}
350}
351
352static int stripe_end_io(struct dm_target *ti, struct bio *bio, int error)
353{
354	unsigned i;
355	char major_minor[16];
356	struct stripe_c *sc = ti->private;
357
358	if (!error)
359		return 0; /* I/O complete */
360
361	if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
362		return error;
363
364	if (error == -EOPNOTSUPP)
365		return error;
366
367	memset(major_minor, 0, sizeof(major_minor));
368	sprintf(major_minor, "%d:%d",
369		MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
370		MINOR(disk_devt(bio->bi_bdev->bd_disk)));
371
372	/*
373	 * Test to see which stripe drive triggered the event
374	 * and increment error count for all stripes on that device.
375	 * If the error count for a given device exceeds the threshold
376	 * value we will no longer trigger any further events.
377	 */
378	for (i = 0; i < sc->stripes; i++)
379		if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
380			atomic_inc(&(sc->stripe[i].error_count));
381			if (atomic_read(&(sc->stripe[i].error_count)) <
382			    DM_IO_ERROR_THRESHOLD)
383				schedule_work(&sc->trigger_event);
384		}
385
386	return error;
387}
388
389static int stripe_iterate_devices(struct dm_target *ti,
390				  iterate_devices_callout_fn fn, void *data)
391{
392	struct stripe_c *sc = ti->private;
393	int ret = 0;
394	unsigned i = 0;
395
396	do {
397		ret = fn(ti, sc->stripe[i].dev,
398			 sc->stripe[i].physical_start,
399			 sc->stripe_width, data);
400	} while (!ret && ++i < sc->stripes);
401
402	return ret;
403}
404
405static void stripe_io_hints(struct dm_target *ti,
406			    struct queue_limits *limits)
407{
408	struct stripe_c *sc = ti->private;
409	unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
410
411	blk_limits_io_min(limits, chunk_size);
412	blk_limits_io_opt(limits, chunk_size * sc->stripes);
413}
414
415static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
416			struct bio_vec *biovec, int max_size)
417{
418	struct stripe_c *sc = ti->private;
419	sector_t bvm_sector = bvm->bi_sector;
420	uint32_t stripe;
421	struct request_queue *q;
422
423	stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
424
425	q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
426	if (!q->merge_bvec_fn)
427		return max_size;
428
429	bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
430	bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
431
432	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
433}
434
435static struct target_type stripe_target = {
436	.name   = "striped",
437	.version = {1, 5, 1},
438	.module = THIS_MODULE,
439	.ctr    = stripe_ctr,
440	.dtr    = stripe_dtr,
441	.map    = stripe_map,
442	.end_io = stripe_end_io,
443	.status = stripe_status,
444	.iterate_devices = stripe_iterate_devices,
445	.io_hints = stripe_io_hints,
446	.merge  = stripe_merge,
447};
448
449int __init dm_stripe_init(void)
450{
451	int r;
452
453	r = dm_register_target(&stripe_target);
454	if (r < 0) {
455		DMWARN("target registration failed");
456		return r;
457	}
458
459	return r;
460}
461
462void dm_stripe_exit(void)
463{
464	dm_unregister_target(&stripe_target);
465}
466