summaryrefslogtreecommitdiffstats
path: root/common/block.c
blob: 2cf85ae9875805a57b1a7ef747de1e498bbe236e (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
/*
 * block.c - simple block layer
 *
 * Copyright (c) 2011 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */
#include <common.h>
#include <block.h>
#include <malloc.h>
#include <linux/err.h>
#include <linux/list.h>
#include <dma.h>

#define BLOCKSIZE(blk)	(1 << blk->blockbits)

/* a chunk of contigous data */
struct chunk {
	void *data; /* data buffer */
	int block_start; /* first block in this chunk */
	int dirty; /* need to write back to device */
	int num; /* number of chunk, debugging only */
	struct list_head list;
};

#define BUFSIZE (PAGE_SIZE * 16)

/*
 * Write all dirty chunks back to the device
 */
static int writebuffer_flush(struct block_device *blk)
{
	struct chunk *chunk;

	list_for_each_entry(chunk, &blk->buffered_blocks, list) {
		if (chunk->dirty) {
			blk->ops->write(blk, chunk->data, chunk->block_start, blk->rdbufsize);
			chunk->dirty = 0;
		}
	}

	return 0;
}

/*
 * get the chunk containing a given block. Will return NULL if the
 * block is not cached, the chunk otherwise.
 */
static struct chunk *chunk_get_cached(struct block_device *blk, int block)
{
	struct chunk *chunk;

	list_for_each_entry(chunk, &blk->buffered_blocks, list) {
		if (block >= chunk->block_start &&
				block < chunk->block_start + blk->rdbufsize) {
			debug("%s: found %d in %d\n", __func__, block, chunk->num);
			/*
			 * move most recently used entry to the head of the list
			 */
			list_move(&chunk->list, &blk->buffered_blocks);
			return chunk;
		}
	}

	return NULL;
}

/*
 * Get the data pointer for a given block. Will return NULL if
 * the block is not cached, the data pointer otherwise.
 */
static void *block_get_cached(struct block_device *blk, int block)
{
	struct chunk *chunk;

	chunk = chunk_get_cached(blk, block);
	if (!chunk)
		return NULL;

	return chunk->data + (block - chunk->block_start) * BLOCKSIZE(blk);
}

/*
 * Get a data chunk, either from the idle list or if the idle list
 * is empty, the least recently used is written back to disk and
 * returned.
 */
static struct chunk *get_chunk(struct block_device *blk)
{
	struct chunk *chunk;

	if (list_empty(&blk->idle_blocks)) {
		/* use last entry which is the most unused */
		chunk = list_last_entry(&blk->buffered_blocks, struct chunk, list);
		if (chunk->dirty) {
			size_t num_blocks = min(blk->rdbufsize,
					blk->num_blocks - chunk->block_start);
			blk->ops->write(blk, chunk->data, chunk->block_start,
					num_blocks);
			chunk->dirty = 0;
		}

		list_del(&chunk->list);
	} else {
		chunk = list_first_entry(&blk->idle_blocks, struct chunk, list);
		list_del(&chunk->list);
	}

	return chunk;
}

/*
 * read a block into the cache. This assumes that the block is
 * not cached already. By definition block_get_cached() for
 * the same block will succeed after this call.
 */
static int block_cache(struct block_device *blk, int block)
{
	struct chunk *chunk;
	size_t num_blocks;
	int ret;

	chunk = get_chunk(blk);
	chunk->block_start = block & ~blk->blkmask;

	debug("%s: %d to %d\n", __func__, chunk->block_start,
			chunk->num);

	num_blocks = min(blk->rdbufsize, blk->num_blocks - chunk->block_start);

	ret = blk->ops->read(blk, chunk->data, chunk->block_start, num_blocks);
	if (ret) {
		list_add_tail(&chunk->list, &blk->idle_blocks);
		return ret;
	}
	list_add(&chunk->list, &blk->buffered_blocks);

	return 0;
}

/*
 * Get the data for a block, either from the cache or from
 * the device.
 */
static void *block_get(struct block_device *blk, int block)
{
	void *outdata;
	int ret;

	if (block >= blk->num_blocks)
		return ERR_PTR(-ENXIO);

	outdata = block_get_cached(blk, block);
	if (outdata)
		return outdata;

	ret = block_cache(blk, block);
	if (ret)
		return ERR_PTR(ret);

	outdata = block_get_cached(blk, block);
	if (!outdata)
		BUG();

	return outdata;
}

static ssize_t block_op_read(struct cdev *cdev, void *buf, size_t count,
		loff_t offset, unsigned long flags)
{
	struct block_device *blk = cdev->priv;
	unsigned long mask = BLOCKSIZE(blk) - 1;
	unsigned long block = offset >> blk->blockbits;
	size_t icount = count;
	int blocks;

	if (offset & mask) {
		size_t now = BLOCKSIZE(blk) - (offset & mask);
		void *iobuf = block_get(blk, block);

		if (IS_ERR(iobuf))
			return PTR_ERR(iobuf);

		now = min(count, now);

		memcpy(buf, iobuf + (offset & mask), now);
		buf += now;
		count -= now;
		block++;
	}

	blocks = count >> blk->blockbits;

	while (blocks) {
		void *iobuf = block_get(blk, block);

		if (IS_ERR(iobuf))
			return PTR_ERR(iobuf);

		memcpy(buf, iobuf, BLOCKSIZE(blk));
		buf += BLOCKSIZE(blk);
		blocks--;
		block++;
		count -= BLOCKSIZE(blk);
	}

	if (count) {
		void *iobuf = block_get(blk, block);

		if (IS_ERR(iobuf))
			return PTR_ERR(iobuf);

		memcpy(buf, iobuf, count);
	}

	return icount;
}

#ifdef CONFIG_BLOCK_WRITE

/*
 * Put data into a block. This only overwrites the data in the
 * cache and marks the corresponding chunk as dirty.
 */
static int block_put(struct block_device *blk, const void *buf, int block)
{
	struct chunk *chunk;
	void *data;

	if (block >= blk->num_blocks)
		return -EINVAL;

	data = block_get(blk, block);
	if (IS_ERR(data))
		return PTR_ERR(data);

	memcpy(data, buf, 1 << blk->blockbits);

	chunk = chunk_get_cached(blk, block);
	chunk->dirty = 1;

	return 0;
}

static ssize_t block_op_write(struct cdev *cdev, const void *buf, size_t count,
		loff_t offset, ulong flags)
{
	struct block_device *blk = cdev->priv;
	unsigned long mask = BLOCKSIZE(blk) - 1;
	unsigned long block = offset >> blk->blockbits;
	size_t icount = count;
	int blocks, ret;

	if (offset & mask) {
		size_t now = BLOCKSIZE(blk) - (offset & mask);
		void *iobuf = block_get(blk, block);

		now = min(count, now);

		if (IS_ERR(iobuf))
			return PTR_ERR(iobuf);

		memcpy(iobuf + (offset & mask), buf, now);
		ret = block_put(blk, iobuf, block);
		if (ret)
			return ret;

		buf += now;
		count -= now;
		block++;
	}

	blocks = count >> blk->blockbits;

	while (blocks) {
		ret = block_put(blk, buf, block);
		if (ret)
			return ret;

		buf += BLOCKSIZE(blk);
		blocks--;
		block++;
		count -= BLOCKSIZE(blk);
	}

	if (count) {
		void *iobuf = block_get(blk, block);

		if (IS_ERR(iobuf))
			return PTR_ERR(iobuf);

		memcpy(iobuf, buf, count);
		ret = block_put(blk, iobuf, block);
		if (ret)
			return ret;
	}

	return icount;
}
#endif

static int block_op_close(struct cdev *cdev)
{
	struct block_device *blk = cdev->priv;

	return writebuffer_flush(blk);
}

static int block_op_flush(struct cdev *cdev)
{
	struct block_device *blk = cdev->priv;

	return writebuffer_flush(blk);
}

static struct file_operations block_ops = {
	.read	= block_op_read,
#ifdef CONFIG_BLOCK_WRITE
	.write	= block_op_write,
#endif
	.close	= block_op_close,
	.flush	= block_op_flush,
	.lseek	= dev_lseek_default,
};

int blockdevice_register(struct block_device *blk)
{
	loff_t size = (loff_t)blk->num_blocks * BLOCKSIZE(blk);
	int ret;
	int i;

	blk->cdev.size = size;
	blk->cdev.dev = blk->dev;
	blk->cdev.ops = &block_ops;
	blk->cdev.priv = blk;
	blk->rdbufsize = BUFSIZE >> blk->blockbits;

	INIT_LIST_HEAD(&blk->buffered_blocks);
	INIT_LIST_HEAD(&blk->idle_blocks);
	blk->blkmask = blk->rdbufsize - 1;

	debug("%s: rdbufsize: %d blockbits: %d blkmask: 0x%08x\n", __func__, blk->rdbufsize, blk->blockbits,
			blk->blkmask);

	for (i = 0; i < 8; i++) {
		struct chunk *chunk = xzalloc(sizeof(*chunk));
		chunk->data = dma_alloc(BUFSIZE);
		chunk->num = i;
		list_add_tail(&chunk->list, &blk->idle_blocks);
	}

	ret = devfs_create(&blk->cdev);
	if (ret)
		return ret;

	return 0;
}

int blockdevice_unregister(struct block_device *blk)
{
	struct chunk *chunk, *tmp;

	writebuffer_flush(blk);

	list_for_each_entry_safe(chunk, tmp, &blk->buffered_blocks, list) {
		dma_free(chunk->data);
		free(chunk);
	}

	list_for_each_entry_safe(chunk, tmp, &blk->idle_blocks, list) {
		dma_free(chunk->data);
		free(chunk);
	}

	devfs_remove(&blk->cdev);

	return 0;
}