summaryrefslogtreecommitdiff
path: root/fs/erofs/decompressor.c
blob: 88e33addf2298e21903dbab7b8621994479ffbe0 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2019 HUAWEI, Inc.
 *             https://www.huawei.com/
 * Created by Gao Xiang <gaoxiang25@huawei.com>
 */
#include "compress.h"
#include <linux/module.h>
#include <linux/lz4.h>

#ifndef LZ4_DISTANCE_MAX	/* history window size */
#define LZ4_DISTANCE_MAX 65535	/* set to maximum value by default */
#endif

#define LZ4_MAX_DISTANCE_PAGES	(DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
#ifndef LZ4_DECOMPRESS_INPLACE_MARGIN
#define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize)  (((srcsize) >> 8) + 32)
#endif

struct z_erofs_decompressor {
	/*
	 * if destpages have sparsed pages, fill them with bounce pages.
	 * it also check whether destpages indicate continuous physical memory.
	 */
	int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
				 struct list_head *pagepool);
	int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
	char *name;
};

int z_erofs_load_lz4_config(struct super_block *sb,
			    struct erofs_super_block *dsb,
			    struct z_erofs_lz4_cfgs *lz4, int size)
{
	struct erofs_sb_info *sbi = EROFS_SB(sb);
	u16 distance;

	if (lz4) {
		if (size < sizeof(struct z_erofs_lz4_cfgs)) {
			erofs_err(sb, "invalid lz4 cfgs, size=%u", size);
			return -EINVAL;
		}
		distance = le16_to_cpu(lz4->max_distance);

		sbi->lz4.max_pclusterblks = le16_to_cpu(lz4->max_pclusterblks);
		if (!sbi->lz4.max_pclusterblks) {
			sbi->lz4.max_pclusterblks = 1;	/* reserved case */
		} else if (sbi->lz4.max_pclusterblks >
			   Z_EROFS_PCLUSTER_MAX_SIZE / EROFS_BLKSIZ) {
			erofs_err(sb, "too large lz4 pclusterblks %u",
				  sbi->lz4.max_pclusterblks);
			return -EINVAL;
		} else if (sbi->lz4.max_pclusterblks >= 2) {
			erofs_info(sb, "EXPERIMENTAL big pcluster feature in use. Use at your own risk!");
		}
	} else {
		distance = le16_to_cpu(dsb->u1.lz4_max_distance);
		sbi->lz4.max_pclusterblks = 1;
	}

	sbi->lz4.max_distance_pages = distance ?
					DIV_ROUND_UP(distance, PAGE_SIZE) + 1 :
					LZ4_MAX_DISTANCE_PAGES;
	return erofs_pcpubuf_growsize(sbi->lz4.max_pclusterblks);
}

static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
					 struct list_head *pagepool)
{
	const unsigned int nr =
		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
	struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
	unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
					   BITS_PER_LONG)] = { 0 };
	unsigned int lz4_max_distance_pages =
				EROFS_SB(rq->sb)->lz4.max_distance_pages;
	void *kaddr = NULL;
	unsigned int i, j, top;

	top = 0;
	for (i = j = 0; i < nr; ++i, ++j) {
		struct page *const page = rq->out[i];
		struct page *victim;

		if (j >= lz4_max_distance_pages)
			j = 0;

		/* 'valid' bounced can only be tested after a complete round */
		if (test_bit(j, bounced)) {
			DBG_BUGON(i < lz4_max_distance_pages);
			DBG_BUGON(top >= lz4_max_distance_pages);
			availables[top++] = rq->out[i - lz4_max_distance_pages];
		}

		if (page) {
			__clear_bit(j, bounced);
			if (kaddr) {
				if (kaddr + PAGE_SIZE == page_address(page))
					kaddr += PAGE_SIZE;
				else
					kaddr = NULL;
			} else if (!i) {
				kaddr = page_address(page);
			}
			continue;
		}
		kaddr = NULL;
		__set_bit(j, bounced);

		if (top) {
			victim = availables[--top];
			get_page(victim);
		} else {
			victim = erofs_allocpage(pagepool,
						 GFP_KERNEL | __GFP_NOFAIL);
			set_page_private(victim, Z_EROFS_SHORTLIVED_PAGE);
		}
		rq->out[i] = victim;
	}
	return kaddr ? 1 : 0;
}

static void *z_erofs_handle_inplace_io(struct z_erofs_decompress_req *rq,
			void *inpage, unsigned int *inputmargin, int *maptype,
			bool support_0padding)
{
	unsigned int nrpages_in, nrpages_out;
	unsigned int ofull, oend, inputsize, total, i, j;
	struct page **in;
	void *src, *tmp;

	inputsize = rq->inputsize;
	nrpages_in = PAGE_ALIGN(inputsize) >> PAGE_SHIFT;
	oend = rq->pageofs_out + rq->outputsize;
	ofull = PAGE_ALIGN(oend);
	nrpages_out = ofull >> PAGE_SHIFT;

	if (rq->inplace_io) {
		if (rq->partial_decoding || !support_0padding ||
		    ofull - oend < LZ4_DECOMPRESS_INPLACE_MARGIN(inputsize))
			goto docopy;

		for (i = 0; i < nrpages_in; ++i) {
			DBG_BUGON(rq->in[i] == NULL);
			for (j = 0; j < nrpages_out - nrpages_in + i; ++j)
				if (rq->out[j] == rq->in[i])
					goto docopy;
		}
	}

	if (nrpages_in <= 1) {
		*maptype = 0;
		return inpage;
	}
	kunmap_atomic(inpage);
	might_sleep();
	src = erofs_vm_map_ram(rq->in, nrpages_in);
	if (!src)
		return ERR_PTR(-ENOMEM);
	*maptype = 1;
	return src;

docopy:
	/* Or copy compressed data which can be overlapped to per-CPU buffer */
	in = rq->in;
	src = erofs_get_pcpubuf(nrpages_in);
	if (!src) {
		DBG_BUGON(1);
		kunmap_atomic(inpage);
		return ERR_PTR(-EFAULT);
	}

	tmp = src;
	total = rq->inputsize;
	while (total) {
		unsigned int page_copycnt =
			min_t(unsigned int, total, PAGE_SIZE - *inputmargin);

		if (!inpage)
			inpage = kmap_atomic(*in);
		memcpy(tmp, inpage + *inputmargin, page_copycnt);
		kunmap_atomic(inpage);
		inpage = NULL;
		tmp += page_copycnt;
		total -= page_copycnt;
		++in;
		*inputmargin = 0;
	}
	*maptype = 2;
	return src;
}

static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
{
	unsigned int inputmargin;
	u8 *headpage, *src;
	bool support_0padding;
	int ret, maptype;

	DBG_BUGON(*rq->in == NULL);
	headpage = kmap_atomic(*rq->in);
	inputmargin = 0;
	support_0padding = false;

	/* decompression inplace is only safe when 0padding is enabled */
	if (erofs_sb_has_lz4_0padding(EROFS_SB(rq->sb))) {
		support_0padding = true;

		while (!headpage[inputmargin & ~PAGE_MASK])
			if (!(++inputmargin & ~PAGE_MASK))
				break;

		if (inputmargin >= rq->inputsize) {
			kunmap_atomic(headpage);
			return -EIO;
		}
	}

	rq->inputsize -= inputmargin;
	src = z_erofs_handle_inplace_io(rq, headpage, &inputmargin, &maptype,
					support_0padding);
	if (IS_ERR(src))
		return PTR_ERR(src);

	/* legacy format could compress extra data in a pcluster. */
	if (rq->partial_decoding || !support_0padding)
		ret = LZ4_decompress_safe_partial(src + inputmargin, out,
				rq->inputsize, rq->outputsize, rq->outputsize);
	else
		ret = LZ4_decompress_safe(src + inputmargin, out,
					  rq->inputsize, rq->outputsize);

	if (ret != rq->outputsize) {
		erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]",
			  ret, rq->inputsize, inputmargin, rq->outputsize);

		WARN_ON(1);
		print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
			       16, 1, src + inputmargin, rq->inputsize, true);
		print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
			       16, 1, out, rq->outputsize, true);

		if (ret >= 0)
			memset(out + ret, 0, rq->outputsize - ret);
		ret = -EIO;
	}

	if (maptype == 0) {
		kunmap_atomic(src);
	} else if (maptype == 1) {
		vm_unmap_ram(src, PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT);
	} else if (maptype == 2) {
		erofs_put_pcpubuf(src);
	} else {
		DBG_BUGON(1);
		return -EFAULT;
	}
	return ret;
}

static struct z_erofs_decompressor decompressors[] = {
	[Z_EROFS_COMPRESSION_SHIFTED] = {
		.name = "shifted"
	},
	[Z_EROFS_COMPRESSION_LZ4] = {
		.prepare_destpages = z_erofs_lz4_prepare_destpages,
		.decompress = z_erofs_lz4_decompress,
		.name = "lz4"
	},
};

static void copy_from_pcpubuf(struct page **out, const char *dst,
			      unsigned short pageofs_out,
			      unsigned int outputsize)
{
	const char *end = dst + outputsize;
	const unsigned int righthalf = PAGE_SIZE - pageofs_out;
	const char *cur = dst - pageofs_out;

	while (cur < end) {
		struct page *const page = *out++;

		if (page) {
			char *buf = kmap_atomic(page);

			if (cur >= dst) {
				memcpy(buf, cur, min_t(uint, PAGE_SIZE,
						       end - cur));
			} else {
				memcpy(buf + pageofs_out, cur + pageofs_out,
				       min_t(uint, righthalf, end - cur));
			}
			kunmap_atomic(buf);
		}
		cur += PAGE_SIZE;
	}
}

static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
				      struct list_head *pagepool)
{
	const unsigned int nrpages_out =
		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
	const struct z_erofs_decompressor *alg = decompressors + rq->alg;
	unsigned int dst_maptype;
	void *dst;
	int ret;

	/* two optimized fast paths only for non bigpcluster cases yet */
	if (rq->inputsize <= PAGE_SIZE) {
		if (nrpages_out == 1 && !rq->inplace_io) {
			DBG_BUGON(!*rq->out);
			dst = kmap_atomic(*rq->out);
			dst_maptype = 0;
			goto dstmap_out;
		}

		/*
		 * For the case of small output size (especially much less
		 * than PAGE_SIZE), memcpy the decompressed data rather than
		 * compressed data is preferred.
		 */
		if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
			dst = erofs_get_pcpubuf(1);
			if (IS_ERR(dst))
				return PTR_ERR(dst);

			rq->inplace_io = false;
			ret = alg->decompress(rq, dst);
			if (!ret)
				copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
						  rq->outputsize);

			erofs_put_pcpubuf(dst);
			return ret;
		}
	}

	/* general decoding path which can be used for all cases */
	ret = alg->prepare_destpages(rq, pagepool);
	if (ret < 0)
		return ret;
	if (ret) {
		dst = page_address(*rq->out);
		dst_maptype = 1;
		goto dstmap_out;
	}

	dst = erofs_vm_map_ram(rq->out, nrpages_out);
	if (!dst)
		return -ENOMEM;
	dst_maptype = 2;

dstmap_out:
	ret = alg->decompress(rq, dst + rq->pageofs_out);

	if (!dst_maptype)
		kunmap_atomic(dst);
	else if (dst_maptype == 2)
		vm_unmap_ram(dst, nrpages_out);
	return ret;
}

static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
				     struct list_head *pagepool)
{
	const unsigned int nrpages_out =
		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
	const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
	unsigned char *src, *dst;

	if (nrpages_out > 2) {
		DBG_BUGON(1);
		return -EIO;
	}

	if (rq->out[0] == *rq->in) {
		DBG_BUGON(nrpages_out != 1);
		return 0;
	}

	src = kmap_atomic(*rq->in);
	if (rq->out[0]) {
		dst = kmap_atomic(rq->out[0]);
		memcpy(dst + rq->pageofs_out, src, righthalf);
		kunmap_atomic(dst);
	}

	if (nrpages_out == 2) {
		DBG_BUGON(!rq->out[1]);
		if (rq->out[1] == *rq->in) {
			memmove(src, src + righthalf, rq->pageofs_out);
		} else {
			dst = kmap_atomic(rq->out[1]);
			memcpy(dst, src + righthalf, rq->pageofs_out);
			kunmap_atomic(dst);
		}
	}
	kunmap_atomic(src);
	return 0;
}

int z_erofs_decompress(struct z_erofs_decompress_req *rq,
		       struct list_head *pagepool)
{
	if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
		return z_erofs_shifted_transform(rq, pagepool);
	return z_erofs_decompress_generic(rq, pagepool);
}