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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2019 HUAWEI, Inc.
4 * http://www.huawei.com/
5 * Created by Gao Xiang <gaoxiang25@huawei.com>
6 */
7#include "compress.h"
8#include <linux/module.h>
9#include <linux/lz4.h>
10
11#ifndef LZ4_DISTANCE_MAX /* history window size */
12#define LZ4_DISTANCE_MAX 65535 /* set to maximum value by default */
13#endif
14
15#define LZ4_MAX_DISTANCE_PAGES (DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
16#ifndef LZ4_DECOMPRESS_INPLACE_MARGIN
17#define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize) (((srcsize) >> 8) + 32)
18#endif
19
20struct z_erofs_decompressor {
21 /*
22 * if destpages have sparsed pages, fill them with bounce pages.
23 * it also check whether destpages indicate continuous physical memory.
24 */
25 int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
26 struct list_head *pagepool);
27 int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
28 char *name;
29};
30
31static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
32 struct list_head *pagepool)
33{
34 const unsigned int nr =
35 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
36 struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
37 unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
38 BITS_PER_LONG)] = { 0 };
39 void *kaddr = NULL;
40 unsigned int i, j, top;
41
42 top = 0;
43 for (i = j = 0; i < nr; ++i, ++j) {
44 struct page *const page = rq->out[i];
45 struct page *victim;
46
47 if (j >= LZ4_MAX_DISTANCE_PAGES)
48 j = 0;
49
50 /* 'valid' bounced can only be tested after a complete round */
51 if (test_bit(j, bounced)) {
52 DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES);
53 DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES);
54 availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES];
55 }
56
57 if (page) {
58 __clear_bit(j, bounced);
59 if (kaddr) {
60 if (kaddr + PAGE_SIZE == page_address(page))
61 kaddr += PAGE_SIZE;
62 else
63 kaddr = NULL;
64 } else if (!i) {
65 kaddr = page_address(page);
66 }
67 continue;
68 }
69 kaddr = NULL;
70 __set_bit(j, bounced);
71
72 if (top) {
73 victim = availables[--top];
74 get_page(victim);
75 } else {
76 victim = erofs_allocpage(pagepool, GFP_KERNEL, false);
77 if (!victim)
78 return -ENOMEM;
79 victim->mapping = Z_EROFS_MAPPING_STAGING;
80 }
81 rq->out[i] = victim;
82 }
83 return kaddr ? 1 : 0;
84}
85
86static void *generic_copy_inplace_data(struct z_erofs_decompress_req *rq,
87 u8 *src, unsigned int pageofs_in)
88{
89 /*
90 * if in-place decompression is ongoing, those decompressed
91 * pages should be copied in order to avoid being overlapped.
92 */
93 struct page **in = rq->in;
94 u8 *const tmp = erofs_get_pcpubuf(0);
95 u8 *tmpp = tmp;
96 unsigned int inlen = rq->inputsize - pageofs_in;
97 unsigned int count = min_t(uint, inlen, PAGE_SIZE - pageofs_in);
98
99 while (tmpp < tmp + inlen) {
100 if (!src)
101 src = kmap_atomic(*in);
102 memcpy(tmpp, src + pageofs_in, count);
103 kunmap_atomic(src);
104 src = NULL;
105 tmpp += count;
106 pageofs_in = 0;
107 count = PAGE_SIZE;
108 ++in;
109 }
110 return tmp;
111}
112
113static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
114{
115 unsigned int inputmargin, inlen;
116 u8 *src;
117 bool copied, support_0padding;
118 int ret;
119
120 if (rq->inputsize > PAGE_SIZE)
121 return -EOPNOTSUPP;
122
123 src = kmap_atomic(*rq->in);
124 inputmargin = 0;
125 support_0padding = false;
126
127 /* decompression inplace is only safe when 0padding is enabled */
128 if (EROFS_SB(rq->sb)->feature_incompat &
129 EROFS_FEATURE_INCOMPAT_LZ4_0PADDING) {
130 support_0padding = true;
131
132 while (!src[inputmargin & ~PAGE_MASK])
133 if (!(++inputmargin & ~PAGE_MASK))
134 break;
135
136 if (inputmargin >= rq->inputsize) {
137 kunmap_atomic(src);
138 return -EIO;
139 }
140 }
141
142 copied = false;
143 inlen = rq->inputsize - inputmargin;
144 if (rq->inplace_io) {
145 const uint oend = (rq->pageofs_out +
146 rq->outputsize) & ~PAGE_MASK;
147 const uint nr = PAGE_ALIGN(rq->pageofs_out +
148 rq->outputsize) >> PAGE_SHIFT;
149
150 if (rq->partial_decoding || !support_0padding ||
151 rq->out[nr - 1] != rq->in[0] ||
152 rq->inputsize - oend <
153 LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) {
154 src = generic_copy_inplace_data(rq, src, inputmargin);
155 inputmargin = 0;
156 copied = true;
157 }
158 }
159
160 ret = LZ4_decompress_safe_partial(src + inputmargin, out,
161 inlen, rq->outputsize,
162 rq->outputsize);
163 if (ret < 0) {
164 erofs_err(rq->sb, "failed to decompress, in[%u, %u] out[%u]",
165 inlen, inputmargin, rq->outputsize);
166 WARN_ON(1);
167 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
168 16, 1, src + inputmargin, inlen, true);
169 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
170 16, 1, out, rq->outputsize, true);
171 ret = -EIO;
172 }
173
174 if (copied)
175 erofs_put_pcpubuf(src);
176 else
177 kunmap_atomic(src);
178 return ret;
179}
180
181static struct z_erofs_decompressor decompressors[] = {
182 [Z_EROFS_COMPRESSION_SHIFTED] = {
183 .name = "shifted"
184 },
185 [Z_EROFS_COMPRESSION_LZ4] = {
186 .prepare_destpages = z_erofs_lz4_prepare_destpages,
187 .decompress = z_erofs_lz4_decompress,
188 .name = "lz4"
189 },
190};
191
192static void copy_from_pcpubuf(struct page **out, const char *dst,
193 unsigned short pageofs_out,
194 unsigned int outputsize)
195{
196 const char *end = dst + outputsize;
197 const unsigned int righthalf = PAGE_SIZE - pageofs_out;
198 const char *cur = dst - pageofs_out;
199
200 while (cur < end) {
201 struct page *const page = *out++;
202
203 if (page) {
204 char *buf = kmap_atomic(page);
205
206 if (cur >= dst) {
207 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
208 end - cur));
209 } else {
210 memcpy(buf + pageofs_out, cur + pageofs_out,
211 min_t(uint, righthalf, end - cur));
212 }
213 kunmap_atomic(buf);
214 }
215 cur += PAGE_SIZE;
216 }
217}
218
219static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
220 struct list_head *pagepool)
221{
222 const unsigned int nrpages_out =
223 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
224 const struct z_erofs_decompressor *alg = decompressors + rq->alg;
225 unsigned int dst_maptype;
226 void *dst;
227 int ret, i;
228
229 if (nrpages_out == 1 && !rq->inplace_io) {
230 DBG_BUGON(!*rq->out);
231 dst = kmap_atomic(*rq->out);
232 dst_maptype = 0;
233 goto dstmap_out;
234 }
235
236 /*
237 * For the case of small output size (especially much less
238 * than PAGE_SIZE), memcpy the decompressed data rather than
239 * compressed data is preferred.
240 */
241 if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
242 dst = erofs_get_pcpubuf(0);
243 if (IS_ERR(dst))
244 return PTR_ERR(dst);
245
246 rq->inplace_io = false;
247 ret = alg->decompress(rq, dst);
248 if (!ret)
249 copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
250 rq->outputsize);
251
252 erofs_put_pcpubuf(dst);
253 return ret;
254 }
255
256 ret = alg->prepare_destpages(rq, pagepool);
257 if (ret < 0) {
258 return ret;
259 } else if (ret) {
260 dst = page_address(*rq->out);
261 dst_maptype = 1;
262 goto dstmap_out;
263 }
264
265 i = 0;
266 while (1) {
267 dst = vm_map_ram(rq->out, nrpages_out, -1, PAGE_KERNEL);
268
269 /* retry two more times (totally 3 times) */
270 if (dst || ++i >= 3)
271 break;
272 vm_unmap_aliases();
273 }
274
275 if (!dst)
276 return -ENOMEM;
277
278 dst_maptype = 2;
279
280dstmap_out:
281 ret = alg->decompress(rq, dst + rq->pageofs_out);
282
283 if (!dst_maptype)
284 kunmap_atomic(dst);
285 else if (dst_maptype == 2)
286 vm_unmap_ram(dst, nrpages_out);
287 return ret;
288}
289
290static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
291 struct list_head *pagepool)
292{
293 const unsigned int nrpages_out =
294 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
295 const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
296 unsigned char *src, *dst;
297
298 if (nrpages_out > 2) {
299 DBG_BUGON(1);
300 return -EIO;
301 }
302
303 if (rq->out[0] == *rq->in) {
304 DBG_BUGON(nrpages_out != 1);
305 return 0;
306 }
307
308 src = kmap_atomic(*rq->in);
309 if (!rq->out[0]) {
310 dst = NULL;
311 } else {
312 dst = kmap_atomic(rq->out[0]);
313 memcpy(dst + rq->pageofs_out, src, righthalf);
314 }
315
316 if (rq->out[1] == *rq->in) {
317 memmove(src, src + righthalf, rq->pageofs_out);
318 } else if (nrpages_out == 2) {
319 if (dst)
320 kunmap_atomic(dst);
321 DBG_BUGON(!rq->out[1]);
322 dst = kmap_atomic(rq->out[1]);
323 memcpy(dst, src + righthalf, rq->pageofs_out);
324 }
325 if (dst)
326 kunmap_atomic(dst);
327 kunmap_atomic(src);
328 return 0;
329}
330
331int z_erofs_decompress(struct z_erofs_decompress_req *rq,
332 struct list_head *pagepool)
333{
334 if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
335 return z_erofs_shifted_transform(rq, pagepool);
336 return z_erofs_decompress_generic(rq, pagepool);
337}
338