summaryrefslogtreecommitdiffstats
path: root/drivers/md/dm-ebs-target.c
blob: 512cc6cea095a3c0f5c4ccc7780ec417fed668cf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
/*
 * Copyright (C) 2020 Red Hat GmbH
 *
 * This file is released under the GPL.
 *
 * Device-mapper target to emulate smaller logical block
 * size on backing devices exposing (natively) larger ones.
 *
 * E.g. 512 byte sector emulation on 4K native disks.
 */

#include "dm.h"
#include <linux/module.h>
#include <linux/workqueue.h>
#include <linux/dm-bufio.h>

#define DM_MSG_PREFIX "ebs"

static void ebs_dtr(struct dm_target *ti);

/* Emulated block size context. */
struct ebs_c {
	struct dm_dev *dev;		/* Underlying device to emulate block size on. */
	struct dm_bufio_client *bufio;	/* Use dm-bufio for read and read-modify-write processing. */
	struct workqueue_struct *wq;	/* Workqueue for ^ processing of bios. */
	struct work_struct ws;		/* Work item used for ^. */
	struct bio_list bios_in;	/* Worker bios input list. */
	spinlock_t lock;		/* Guard bios input list above. */
	sector_t start;			/* <start> table line argument, see ebs_ctr below. */
	unsigned int e_bs;		/* Emulated block size in sectors exposed to upper layer. */
	unsigned int u_bs;		/* Underlying block size in sectors retrieved from/set on lower layer device. */
	unsigned char block_shift;	/* bitshift sectors -> blocks used in dm-bufio API. */
	bool u_bs_set:1;		/* Flag to indicate underlying block size is set on table line. */
};

static inline sector_t __sector_to_block(struct ebs_c *ec, sector_t sector)
{
	return sector >> ec->block_shift;
}

static inline sector_t __block_mod(sector_t sector, unsigned int bs)
{
	return sector & (bs - 1);
}

/* Return number of blocks for a bio, accounting for misalignment of start and end sectors. */
static inline unsigned int __nr_blocks(struct ebs_c *ec, struct bio *bio)
{
	sector_t end_sector = __block_mod(bio->bi_iter.bi_sector, ec->u_bs) + bio_sectors(bio);

	return __sector_to_block(ec, end_sector) + (__block_mod(end_sector, ec->u_bs) ? 1 : 0);
}

static inline bool __ebs_check_bs(unsigned int bs)
{
	return bs && is_power_of_2(bs);
}

/*
 * READ/WRITE:
 *
 * copy blocks between bufio blocks and bio vector's (partial/overlapping) pages.
 */
static int __ebs_rw_bvec(struct ebs_c *ec, enum req_op op, struct bio_vec *bv,
			 struct bvec_iter *iter)
{
	int r = 0;
	unsigned char *ba, *pa;
	unsigned int cur_len;
	unsigned int bv_len = bv->bv_len;
	unsigned int buf_off = to_bytes(__block_mod(iter->bi_sector, ec->u_bs));
	sector_t block = __sector_to_block(ec, iter->bi_sector);
	struct dm_buffer *b;

	if (unlikely(!bv->bv_page || !bv_len))
		return -EIO;

	pa = bvec_virt(bv);

	/* Handle overlapping page <-> blocks */
	while (bv_len) {
		cur_len = min(dm_bufio_get_block_size(ec->bufio) - buf_off, bv_len);

		/* Avoid reading for writes in case bio vector's page overwrites block completely. */
		if (op == REQ_OP_READ || buf_off || bv_len < dm_bufio_get_block_size(ec->bufio))
			ba = dm_bufio_read(ec->bufio, block, &b);
		else
			ba = dm_bufio_new(ec->bufio, block, &b);

		if (IS_ERR(ba)) {
			/*
			 * Carry on with next buffer, if any, to issue all possible
			 * data but return error.
			 */
			r = PTR_ERR(ba);
		} else {
			/* Copy data to/from bio to buffer if read/new was successful above. */
			ba += buf_off;
			if (op == REQ_OP_READ) {
				memcpy(pa, ba, cur_len);
				flush_dcache_page(bv->bv_page);
			} else {
				flush_dcache_page(bv->bv_page);
				memcpy(ba, pa, cur_len);
				dm_bufio_mark_partial_buffer_dirty(b, buf_off, buf_off + cur_len);
			}

			dm_bufio_release(b);
		}

		pa += cur_len;
		bv_len -= cur_len;
		buf_off = 0;
		block++;
	}

	return r;
}

/* READ/WRITE: iterate bio vector's copying between (partial) pages and bufio blocks. */
static int __ebs_rw_bio(struct ebs_c *ec, enum req_op op, struct bio *bio)
{
	int r = 0, rr;
	struct bio_vec bv;
	struct bvec_iter iter;

	bio_for_each_bvec(bv, bio, iter) {
		rr = __ebs_rw_bvec(ec, op, &bv, &iter);
		if (rr)
			r = rr;
	}

	return r;
}

/*
 * Discard bio's blocks, i.e. pass discards down.
 *
 * Avoid discarding partial blocks at beginning and end;
 * return 0 in case no blocks can be discarded as a result.
 */
static int __ebs_discard_bio(struct ebs_c *ec, struct bio *bio)
{
	sector_t block, blocks, sector = bio->bi_iter.bi_sector;

	block = __sector_to_block(ec, sector);
	blocks = __nr_blocks(ec, bio);

	/*
	 * Partial first underlying block (__nr_blocks() may have
	 * resulted in one block).
	 */
	if (__block_mod(sector, ec->u_bs)) {
		block++;
		blocks--;
	}

	/* Partial last underlying block if any. */
	if (blocks && __block_mod(bio_end_sector(bio), ec->u_bs))
		blocks--;

	return blocks ? dm_bufio_issue_discard(ec->bufio, block, blocks) : 0;
}

/* Release blocks them from the bufio cache. */
static void __ebs_forget_bio(struct ebs_c *ec, struct bio *bio)
{
	sector_t blocks, sector = bio->bi_iter.bi_sector;

	blocks = __nr_blocks(ec, bio);

	dm_bufio_forget_buffers(ec->bufio, __sector_to_block(ec, sector), blocks);
}

/* Worker function to process incoming bios. */
static void __ebs_process_bios(struct work_struct *ws)
{
	int r;
	bool write = false;
	sector_t block1, block2;
	struct ebs_c *ec = container_of(ws, struct ebs_c, ws);
	struct bio *bio;
	struct bio_list bios;

	bio_list_init(&bios);

	spin_lock_irq(&ec->lock);
	bios = ec->bios_in;
	bio_list_init(&ec->bios_in);
	spin_unlock_irq(&ec->lock);

	/* Prefetch all read and any mis-aligned write buffers */
	bio_list_for_each(bio, &bios) {
		block1 = __sector_to_block(ec, bio->bi_iter.bi_sector);
		if (bio_op(bio) == REQ_OP_READ)
			dm_bufio_prefetch(ec->bufio, block1, __nr_blocks(ec, bio));
		else if (bio_op(bio) == REQ_OP_WRITE && !(bio->bi_opf & REQ_PREFLUSH)) {
			block2 = __sector_to_block(ec, bio_end_sector(bio));
			if (__block_mod(bio->bi_iter.bi_sector, ec->u_bs))
				dm_bufio_prefetch(ec->bufio, block1, 1);
			if (__block_mod(bio_end_sector(bio), ec->u_bs) && block2 != block1)
				dm_bufio_prefetch(ec->bufio, block2, 1);
		}
	}

	bio_list_for_each(bio, &bios) {
		r = -EIO;
		if (bio_op(bio) == REQ_OP_READ)
			r = __ebs_rw_bio(ec, REQ_OP_READ, bio);
		else if (bio_op(bio) == REQ_OP_WRITE) {
			write = true;
			r = __ebs_rw_bio(ec, REQ_OP_WRITE, bio);
		} else if (bio_op(bio) == REQ_OP_DISCARD) {
			__ebs_forget_bio(ec, bio);
			r = __ebs_discard_bio(ec, bio);
		}

		if (r < 0)
			bio->bi_status = errno_to_blk_status(r);
	}

	/*
	 * We write dirty buffers after processing I/O on them
	 * but before we endio thus addressing REQ_FUA/REQ_SYNC.
	 */
	r = write ? dm_bufio_write_dirty_buffers(ec->bufio) : 0;

	while ((bio = bio_list_pop(&bios))) {
		/* Any other request is endioed. */
		if (unlikely(r && bio_op(bio) == REQ_OP_WRITE))
			bio_io_error(bio);
		else
			bio_endio(bio);
	}
}

/*
 * Construct an emulated block size mapping: <dev_path> <offset> <ebs> [<ubs>]
 *
 * <dev_path>: path of the underlying device
 * <offset>: offset in 512 bytes sectors into <dev_path>
 * <ebs>: emulated block size in units of 512 bytes exposed to the upper layer
 * [<ubs>]: underlying block size in units of 512 bytes imposed on the lower layer;
 * 	    optional, if not supplied, retrieve logical block size from underlying device
 */
static int ebs_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
	int r;
	unsigned short tmp1;
	unsigned long long tmp;
	char dummy;
	struct ebs_c *ec;

	if (argc < 3 || argc > 4) {
		ti->error = "Invalid argument count";
		return -EINVAL;
	}

	ec = ti->private = kzalloc(sizeof(*ec), GFP_KERNEL);
	if (!ec) {
		ti->error = "Cannot allocate ebs context";
		return -ENOMEM;
	}

	r = -EINVAL;
	if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1 ||
	    tmp != (sector_t)tmp ||
	    (sector_t)tmp >= ti->len) {
		ti->error = "Invalid device offset sector";
		goto bad;
	}
	ec->start = tmp;

	if (sscanf(argv[2], "%hu%c", &tmp1, &dummy) != 1 ||
	    !__ebs_check_bs(tmp1) ||
	    to_bytes(tmp1) > PAGE_SIZE) {
		ti->error = "Invalid emulated block size";
		goto bad;
	}
	ec->e_bs = tmp1;

	if (argc > 3) {
		if (sscanf(argv[3], "%hu%c", &tmp1, &dummy) != 1 || !__ebs_check_bs(tmp1)) {
			ti->error = "Invalid underlying block size";
			goto bad;
		}
		ec->u_bs = tmp1;
		ec->u_bs_set = true;
	} else
		ec->u_bs_set = false;

	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &ec->dev);
	if (r) {
		ti->error = "Device lookup failed";
		ec->dev = NULL;
		goto bad;
	}

	r = -EINVAL;
	if (!ec->u_bs_set) {
		ec->u_bs = to_sector(bdev_logical_block_size(ec->dev->bdev));
		if (!__ebs_check_bs(ec->u_bs)) {
			ti->error = "Invalid retrieved underlying block size";
			goto bad;
		}
	}

	if (!ec->u_bs_set && ec->e_bs == ec->u_bs)
		DMINFO("Emulation superfluous: emulated equal to underlying block size");

	if (__block_mod(ec->start, ec->u_bs)) {
		ti->error = "Device offset must be multiple of underlying block size";
		goto bad;
	}

	ec->bufio = dm_bufio_client_create(ec->dev->bdev, to_bytes(ec->u_bs), 1,
					   0, NULL, NULL, 0);
	if (IS_ERR(ec->bufio)) {
		ti->error = "Cannot create dm bufio client";
		r = PTR_ERR(ec->bufio);
		ec->bufio = NULL;
		goto bad;
	}

	ec->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
	if (!ec->wq) {
		ti->error = "Cannot create dm-" DM_MSG_PREFIX " workqueue";
		r = -ENOMEM;
		goto bad;
	}

	ec->block_shift = __ffs(ec->u_bs);
	INIT_WORK(&ec->ws, &__ebs_process_bios);
	bio_list_init(&ec->bios_in);
	spin_lock_init(&ec->lock);

	ti->num_flush_bios = 1;
	ti->num_discard_bios = 1;
	ti->num_secure_erase_bios = 0;
	ti->num_write_zeroes_bios = 0;
	return 0;
bad:
	ebs_dtr(ti);
	return r;
}

static void ebs_dtr(struct dm_target *ti)
{
	struct ebs_c *ec = ti->private;

	if (ec->wq)
		destroy_workqueue(ec->wq);
	if (ec->bufio)
		dm_bufio_client_destroy(ec->bufio);
	if (ec->dev)
		dm_put_device(ti, ec->dev);
	kfree(ec);
}

static int ebs_map(struct dm_target *ti, struct bio *bio)
{
	struct ebs_c *ec = ti->private;

	bio_set_dev(bio, ec->dev->bdev);
	bio->bi_iter.bi_sector = ec->start + dm_target_offset(ti, bio->bi_iter.bi_sector);

	if (unlikely(bio_op(bio) == REQ_OP_FLUSH))
		return DM_MAPIO_REMAPPED;
	/*
	 * Only queue for bufio processing in case of partial or overlapping buffers
	 * -or-
	 * emulation with ebs == ubs aiming for tests of dm-bufio overhead.
	 */
	if (likely(__block_mod(bio->bi_iter.bi_sector, ec->u_bs) ||
		   __block_mod(bio_end_sector(bio), ec->u_bs) ||
		   ec->e_bs == ec->u_bs)) {
		spin_lock_irq(&ec->lock);
		bio_list_add(&ec->bios_in, bio);
		spin_unlock_irq(&ec->lock);

		queue_work(ec->wq, &ec->ws);

		return DM_MAPIO_SUBMITTED;
	}

	/* Forget any buffer content relative to this direct backing device I/O. */
	__ebs_forget_bio(ec, bio);

	return DM_MAPIO_REMAPPED;
}

static void ebs_status(struct dm_target *ti, status_type_t type,
		       unsigned status_flags, char *result, unsigned maxlen)
{
	struct ebs_c *ec = ti->private;

	switch (type) {
	case STATUSTYPE_INFO:
		*result = '\0';
		break;
	case STATUSTYPE_TABLE:
		snprintf(result, maxlen, ec->u_bs_set ? "%s %llu %u %u" : "%s %llu %u",
			 ec->dev->name, (unsigned long long) ec->start, ec->e_bs, ec->u_bs);
		break;
	case STATUSTYPE_IMA:
		*result = '\0';
		break;
	}
}

static int ebs_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
{
	struct ebs_c *ec = ti->private;
	struct dm_dev *dev = ec->dev;

	/*
	 * Only pass ioctls through if the device sizes match exactly.
	 */
	*bdev = dev->bdev;
	return !!(ec->start || ti->len != bdev_nr_sectors(dev->bdev));
}

static void ebs_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
	struct ebs_c *ec = ti->private;

	limits->logical_block_size = to_bytes(ec->e_bs);
	limits->physical_block_size = to_bytes(ec->u_bs);
	limits->alignment_offset = limits->physical_block_size;
	blk_limits_io_min(limits, limits->logical_block_size);
}

static int ebs_iterate_devices(struct dm_target *ti,
				  iterate_devices_callout_fn fn, void *data)
{
	struct ebs_c *ec = ti->private;

	return fn(ti, ec->dev, ec->start, ti->len, data);
}

static struct target_type ebs_target = {
	.name		 = "ebs",
	.version	 = {1, 0, 1},
	.features	 = DM_TARGET_PASSES_INTEGRITY,
	.module		 = THIS_MODULE,
	.ctr		 = ebs_ctr,
	.dtr		 = ebs_dtr,
	.map		 = ebs_map,
	.status		 = ebs_status,
	.io_hints	 = ebs_io_hints,
	.prepare_ioctl	 = ebs_prepare_ioctl,
	.iterate_devices = ebs_iterate_devices,
};

static int __init dm_ebs_init(void)
{
	int r = dm_register_target(&ebs_target);

	if (r < 0)
		DMERR("register failed %d", r);

	return r;
}

static void dm_ebs_exit(void)
{
	dm_unregister_target(&ebs_target);
}

module_init(dm_ebs_init);
module_exit(dm_ebs_exit);

MODULE_AUTHOR("Heinz Mauelshagen <dm-devel@redhat.com>");
MODULE_DESCRIPTION(DM_NAME " emulated block size target");
MODULE_LICENSE("GPL");