fs/erofs/decompressor.c

   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
  20 struct 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
  31 static 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 (!PageHighMem(page)) {
  60                                 if (!i) {
  61                                         kaddr = page_address(page);
  62                                         continue;
  63                                 }
  64                                 if (kaddr &&
  65                                     kaddr + PAGE_SIZE == page_address(page)) {
  66                                         kaddr += PAGE_SIZE;
  67                                         continue;
  68                                 }
  69                         }
  70                         kaddr = NULL;
  71                         continue;
  72                 }
  73                 kaddr = NULL;
  74                 __set_bit(j, bounced);
  75
  76                 if (top) {
  77                         victim = availables[--top];
  78                         get_page(victim);
  79                 } else {
  80                         victim = erofs_allocpage(pagepool, GFP_KERNEL, false);
  81                         if (!victim)
  82                                 return -ENOMEM;
  83                         victim->mapping = Z_EROFS_MAPPING_STAGING;
  84                 }
  85                 rq->out[i] = victim;
  86         }
  87         return kaddr ? 1 : 0;
  88 }
  89
  90 static void *generic_copy_inplace_data(struct z_erofs_decompress_req *rq,
  91                                        u8 *src, unsigned int pageofs_in)
  92 {
  93         /*
  94          * if in-place decompression is ongoing, those decompressed
  95          * pages should be copied in order to avoid being overlapped.
  96          */
  97         struct page **in = rq->in;
  98         u8 *const tmp = erofs_get_pcpubuf(0);
  99         u8 *tmpp = tmp;
 100         unsigned int inlen = rq->inputsize - pageofs_in;
 101         unsigned int count = min_t(uint, inlen, PAGE_SIZE - pageofs_in);
 102
 103         while (tmpp < tmp + inlen) {
 104                 if (!src)
 105                         src = kmap_atomic(*in);
 106                 memcpy(tmpp, src + pageofs_in, count);
 107                 kunmap_atomic(src);
 108                 src = NULL;
 109                 tmpp += count;
 110                 pageofs_in = 0;
 111                 count = PAGE_SIZE;
 112                 ++in;
 113         }
 114         return tmp;
 115 }
 116
 117 static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 118 {
 119         unsigned int inputmargin, inlen;
 120         u8 *src;
 121         bool copied, support_0padding;
 122         int ret;
 123
 124         if (rq->inputsize > PAGE_SIZE)
 125                 return -EOPNOTSUPP;
 126
 127         src = kmap_atomic(*rq->in);
 128         inputmargin = 0;
 129         support_0padding = false;
 130
 131         /* decompression inplace is only safe when 0padding is enabled */
 132         if (EROFS_SB(rq->sb)->feature_incompat &
 133             EROFS_FEATURE_INCOMPAT_LZ4_0PADDING) {
 134                 support_0padding = true;
 135
 136                 while (!src[inputmargin & ~PAGE_MASK])
 137                         if (!(++inputmargin & ~PAGE_MASK))
 138                                 break;
 139
 140                 if (inputmargin >= rq->inputsize) {
 141                         kunmap_atomic(src);
 142                         return -EIO;
 143                 }
 144         }
 145
 146         copied = false;
 147         inlen = rq->inputsize - inputmargin;
 148         if (rq->inplace_io) {
 149                 const uint oend = (rq->pageofs_out +
 150                                    rq->outputsize) & ~PAGE_MASK;
 151                 const uint nr = PAGE_ALIGN(rq->pageofs_out +
 152                                            rq->outputsize) >> PAGE_SHIFT;
 153
 154                 if (rq->partial_decoding || !support_0padding ||
 155                     rq->out[nr - 1] != rq->in[0] ||
 156                     rq->inputsize - oend <
 157                       LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) {
 158                         src = generic_copy_inplace_data(rq, src, inputmargin);
 159                         inputmargin = 0;
 160                         copied = true;
 161                 }
 162         }
 163
 164         ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 165                                           inlen, rq->outputsize,
 166                                           rq->outputsize);
 167         if (ret < 0) {
 168                 erofs_err(rq->sb, "failed to decompress, in[%u, %u] out[%u]",
 169                           inlen, inputmargin, rq->outputsize);
 170                 WARN_ON(1);
 171                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 172                                16, 1, src + inputmargin, inlen, true);
 173                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 174                                16, 1, out, rq->outputsize, true);
 175                 ret = -EIO;
 176         }
 177
 178         if (copied)
 179                 erofs_put_pcpubuf(src);
 180         else
 181                 kunmap_atomic(src);
 182         return ret;
 183 }
 184
 185 static struct z_erofs_decompressor decompressors[] = {
 186         [Z_EROFS_COMPRESSION_SHIFTED] = {
 187                 .name = "shifted"
 188         },
 189         [Z_EROFS_COMPRESSION_LZ4] = {
 190                 .prepare_destpages = z_erofs_lz4_prepare_destpages,
 191                 .decompress = z_erofs_lz4_decompress,
 192                 .name = "lz4"
 193         },
 194 };
 195
 196 static void copy_from_pcpubuf(struct page **out, const char *dst,
 197                               unsigned short pageofs_out,
 198                               unsigned int outputsize)
 199 {
 200         const char *end = dst + outputsize;
 201         const unsigned int righthalf = PAGE_SIZE - pageofs_out;
 202         const char *cur = dst - pageofs_out;
 203
 204         while (cur < end) {
 205                 struct page *const page = *out++;
 206
 207                 if (page) {
 208                         char *buf = kmap_atomic(page);
 209
 210                         if (cur >= dst) {
 211                                 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
 212                                                        end - cur));
 213                         } else {
 214                                 memcpy(buf + pageofs_out, cur + pageofs_out,
 215                                        min_t(uint, righthalf, end - cur));
 216                         }
 217                         kunmap_atomic(buf);
 218                 }
 219                 cur += PAGE_SIZE;
 220         }
 221 }
 222
 223 static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
 224                                       struct list_head *pagepool)
 225 {
 226         const unsigned int nrpages_out =
 227                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 228         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 229         unsigned int dst_maptype;
 230         void *dst;
 231         int ret, i;
 232
 233         if (nrpages_out == 1 && !rq->inplace_io) {
 234                 DBG_BUGON(!*rq->out);
 235                 dst = kmap_atomic(*rq->out);
 236                 dst_maptype = 0;
 237                 goto dstmap_out;
 238         }
 239
 240         /*
 241          * For the case of small output size (especially much less
 242          * than PAGE_SIZE), memcpy the decompressed data rather than
 243          * compressed data is preferred.
 244          */
 245         if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 246                 dst = erofs_get_pcpubuf(0);
 247                 if (IS_ERR(dst))
 248                         return PTR_ERR(dst);
 249
 250                 rq->inplace_io = false;
 251                 ret = alg->decompress(rq, dst);
 252                 if (!ret)
 253                         copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 254                                           rq->outputsize);
 255
 256                 erofs_put_pcpubuf(dst);
 257                 return ret;
 258         }
 259
 260         ret = alg->prepare_destpages(rq, pagepool);
 261         if (ret < 0) {
 262                 return ret;
 263         } else if (ret) {
 264                 dst = page_address(*rq->out);
 265                 dst_maptype = 1;
 266                 goto dstmap_out;
 267         }
 268
 269         i = 0;
 270         while (1) {
 271                 dst = vm_map_ram(rq->out, nrpages_out, -1, PAGE_KERNEL);
 272
 273                 /* retry two more times (totally 3 times) */
 274                 if (dst || ++i >= 3)
 275                         break;
 276                 vm_unmap_aliases();
 277         }
 278
 279         if (!dst)
 280                 return -ENOMEM;
 281
 282         dst_maptype = 2;
 283
 284 dstmap_out:
 285         ret = alg->decompress(rq, dst + rq->pageofs_out);
 286
 287         if (!dst_maptype)
 288                 kunmap_atomic(dst);
 289         else if (dst_maptype == 2)
 290                 vm_unmap_ram(dst, nrpages_out);
 291         return ret;
 292 }
 293
 294 static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
 295                                      struct list_head *pagepool)
 296 {
 297         const unsigned int nrpages_out =
 298                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 299         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 300         unsigned char *src, *dst;
 301
 302         if (nrpages_out > 2) {
 303                 DBG_BUGON(1);
 304                 return -EIO;
 305         }
 306
 307         if (rq->out[0] == *rq->in) {
 308                 DBG_BUGON(nrpages_out != 1);
 309                 return 0;
 310         }
 311
 312         src = kmap_atomic(*rq->in);
 313         if (rq->out[0]) {
 314                 dst = kmap_atomic(rq->out[0]);
 315                 memcpy(dst + rq->pageofs_out, src, righthalf);
 316                 kunmap_atomic(dst);
 317         }
 318
 319         if (nrpages_out == 2) {
 320                 DBG_BUGON(!rq->out[1]);
 321                 if (rq->out[1] == *rq->in) {
 322                         memmove(src, src + righthalf, rq->pageofs_out);
 323                 } else {
 324                         dst = kmap_atomic(rq->out[1]);
 325                         memcpy(dst, src + righthalf, rq->pageofs_out);
 326                         kunmap_atomic(dst);
 327                 }
 328         }
 329         kunmap_atomic(src);
 330         return 0;
 331 }
 332
 333 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 334                        struct list_head *pagepool)
 335 {
 336         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 337                 return z_erofs_shifted_transform(rq, pagepool);
 338         return z_erofs_decompress_generic(rq, pagepool);
 339 }
 340