fs/erofs/decompressor.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2019 HUAWEI, Inc.
   4  *             https://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                           u8 *obase);
  29         char *name;
  30 };
  31
  32 static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
  33                                          struct list_head *pagepool)
  34 {
  35         const unsigned int nr =
  36                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
  37         struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
  38         unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
  39                                            BITS_PER_LONG)] = { 0 };
  40         void *kaddr = NULL;
  41         unsigned int i, j, top;
  42
  43         top = 0;
  44         for (i = j = 0; i < nr; ++i, ++j) {
  45                 struct page *const page = rq->out[i];
  46                 struct page *victim;
  47
  48                 if (j >= LZ4_MAX_DISTANCE_PAGES)
  49                         j = 0;
  50
  51                 /* 'valid' bounced can only be tested after a complete round */
  52                 if (test_bit(j, bounced)) {
  53                         DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES);
  54                         DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES);
  55                         availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES];
  56                 }
  57
  58                 if (page) {
  59                         __clear_bit(j, bounced);
  60                         if (!PageHighMem(page)) {
  61                                 if (!i) {
  62                                         kaddr = page_address(page);
  63                                         continue;
  64                                 }
  65                                 if (kaddr &&
  66                                     kaddr + PAGE_SIZE == page_address(page)) {
  67                                         kaddr += PAGE_SIZE;
  68                                         continue;
  69                                 }
  70                         }
  71                         kaddr = NULL;
  72                         continue;
  73                 }
  74                 kaddr = NULL;
  75                 __set_bit(j, bounced);
  76
  77                 if (top) {
  78                         victim = availables[--top];
  79                         get_page(victim);
  80                 } else {
  81                         victim = erofs_allocpage(pagepool, GFP_KERNEL);
  82                         if (!victim)
  83                                 return -ENOMEM;
  84                         victim->mapping = Z_EROFS_MAPPING_STAGING;
  85                 }
  86                 rq->out[i] = victim;
  87         }
  88         return kaddr ? 1 : 0;
  89 }
  90
  91 static void *generic_copy_inplace_data(struct z_erofs_decompress_req *rq,
  92                                        u8 *src, unsigned int pageofs_in)
  93 {
  94         /*
  95          * if in-place decompression is ongoing, those decompressed
  96          * pages should be copied in order to avoid being overlapped.
  97          */
  98         struct page **in = rq->in;
  99         u8 *const tmp = erofs_get_pcpubuf(0);
 100         u8 *tmpp = tmp;
 101         unsigned int inlen = rq->inputsize - pageofs_in;
 102         unsigned int count = min_t(uint, inlen, PAGE_SIZE - pageofs_in);
 103
 104         while (tmpp < tmp + inlen) {
 105                 if (!src)
 106                         src = kmap_atomic(*in);
 107                 memcpy(tmpp, src + pageofs_in, count);
 108                 kunmap_atomic(src);
 109                 src = NULL;
 110                 tmpp += count;
 111                 pageofs_in = 0;
 112                 count = PAGE_SIZE;
 113                 ++in;
 114         }
 115         return tmp;
 116 }
 117
 118 static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out,
 119                                   u8 *obase)
 120 {
 121         const uint nrpages_out = PAGE_ALIGN(rq->pageofs_out +
 122                                             rq->outputsize) >> PAGE_SHIFT;
 123         unsigned int inputmargin, inlen;
 124         u8 *src, *src2;
 125         bool copied, support_0padding;
 126         int ret;
 127
 128         if (rq->inputsize > PAGE_SIZE)
 129                 return -EOPNOTSUPP;
 130
 131         src = kmap_atomic(*rq->in);
 132         src2 = src;
 133         inputmargin = 0;
 134         support_0padding = false;
 135
 136         /* decompression inplace is only safe when 0padding is enabled */
 137         if (EROFS_SB(rq->sb)->feature_incompat &
 138             EROFS_FEATURE_INCOMPAT_LZ4_0PADDING) {
 139                 support_0padding = true;
 140
 141                 while (!src[inputmargin & ~PAGE_MASK])
 142                         if (!(++inputmargin & ~PAGE_MASK))
 143                                 break;
 144
 145                 if (inputmargin >= rq->inputsize) {
 146                         kunmap_atomic(src);
 147                         return -EIO;
 148                 }
 149         }
 150
 151         copied = false;
 152         inlen = rq->inputsize - inputmargin;
 153         if (rq->inplace_io) {
 154                 const uint oend = (rq->pageofs_out +
 155                                    rq->outputsize) & ~PAGE_MASK;
 156                 if (rq->partial_decoding || !support_0padding ||
 157                     rq->out[nrpages_out - 1] != rq->in[0] ||
 158                     rq->inputsize - oend <
 159                       LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) {
 160                         src = generic_copy_inplace_data(rq, src, inputmargin);
 161                         inputmargin = 0;
 162                         copied = true;
 163                 } else {
 164                         src = obase + ((nrpages_out - 1) << PAGE_SHIFT);
 165                 }
 166         }
 167
 168         /* legacy format could compress extra data in a pcluster. */
 169         if (rq->partial_decoding || !support_0padding)
 170                 ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 171                                                   inlen, rq->outputsize,
 172                                                   rq->outputsize);
 173         else
 174                 ret = LZ4_decompress_safe(src + inputmargin, out,
 175                                           inlen, rq->outputsize);
 176
 177         if (ret != rq->outputsize) {
 178                 erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]",
 179                           ret, inlen, inputmargin, rq->outputsize);
 180
 181                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 182                                16, 1, src + inputmargin, inlen, true);
 183                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 184                                16, 1, out, rq->outputsize, true);
 185
 186                 if (ret >= 0)
 187                         memset(out + ret, 0, rq->outputsize - ret);
 188                 ret = -EIO;
 189         }
 190
 191         if (copied)
 192                 erofs_put_pcpubuf(src);
 193         else
 194                 kunmap_atomic(src2);
 195         return ret;
 196 }
 197
 198 static struct z_erofs_decompressor decompressors[] = {
 199         [Z_EROFS_COMPRESSION_SHIFTED] = {
 200                 .name = "shifted"
 201         },
 202         [Z_EROFS_COMPRESSION_LZ4] = {
 203                 .prepare_destpages = z_erofs_lz4_prepare_destpages,
 204                 .decompress = z_erofs_lz4_decompress,
 205                 .name = "lz4"
 206         },
 207 };
 208
 209 static void copy_from_pcpubuf(struct page **out, const char *dst,
 210                               unsigned short pageofs_out,
 211                               unsigned int outputsize)
 212 {
 213         const char *end = dst + outputsize;
 214         const unsigned int righthalf = PAGE_SIZE - pageofs_out;
 215         const char *cur = dst - pageofs_out;
 216
 217         while (cur < end) {
 218                 struct page *const page = *out++;
 219
 220                 if (page) {
 221                         char *buf = kmap_atomic(page);
 222
 223                         if (cur >= dst) {
 224                                 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
 225                                                        end - cur));
 226                         } else {
 227                                 memcpy(buf + pageofs_out, cur + pageofs_out,
 228                                        min_t(uint, righthalf, end - cur));
 229                         }
 230                         kunmap_atomic(buf);
 231                 }
 232                 cur += PAGE_SIZE;
 233         }
 234 }
 235
 236 static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
 237                                       struct list_head *pagepool)
 238 {
 239         const unsigned int nrpages_out =
 240                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 241         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 242         unsigned int dst_maptype;
 243         void *dst;
 244         int ret, i;
 245
 246         if (nrpages_out == 1 && !rq->inplace_io) {
 247                 DBG_BUGON(!*rq->out);
 248                 dst = kmap_atomic(*rq->out);
 249                 dst_maptype = 0;
 250                 goto dstmap_out;
 251         }
 252
 253         /*
 254          * For the case of small output size (especially much less
 255          * than PAGE_SIZE), memcpy the decompressed data rather than
 256          * compressed data is preferred.
 257          */
 258         if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 259                 dst = erofs_get_pcpubuf(0);
 260                 if (IS_ERR(dst))
 261                         return PTR_ERR(dst);
 262
 263                 rq->inplace_io = false;
 264                 ret = alg->decompress(rq, dst, NULL);
 265                 if (!ret)
 266                         copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 267                                           rq->outputsize);
 268
 269                 erofs_put_pcpubuf(dst);
 270                 return ret;
 271         }
 272
 273         ret = alg->prepare_destpages(rq, pagepool);
 274         if (ret < 0) {
 275                 return ret;
 276         } else if (ret) {
 277                 dst = page_address(*rq->out);
 278                 dst_maptype = 1;
 279                 goto dstmap_out;
 280         }
 281
 282         i = 0;
 283         while (1) {
 284                 dst = vm_map_ram(rq->out, nrpages_out, -1);
 285
 286                 /* retry two more times (totally 3 times) */
 287                 if (dst || ++i >= 3)
 288                         break;
 289                 vm_unmap_aliases();
 290         }
 291
 292         if (!dst)
 293                 return -ENOMEM;
 294
 295         dst_maptype = 2;
 296
 297 dstmap_out:
 298         ret = alg->decompress(rq, dst + rq->pageofs_out, dst);
 299
 300         if (!dst_maptype)
 301                 kunmap_atomic(dst);
 302         else if (dst_maptype == 2)
 303                 vm_unmap_ram(dst, nrpages_out);
 304         return ret;
 305 }
 306
 307 static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
 308                                      struct list_head *pagepool)
 309 {
 310         const unsigned int nrpages_out =
 311                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 312         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 313         unsigned char *src, *dst;
 314
 315         if (nrpages_out > 2) {
 316                 DBG_BUGON(1);
 317                 return -EIO;
 318         }
 319
 320         if (rq->out[0] == *rq->in) {
 321                 DBG_BUGON(nrpages_out != 1);
 322                 return 0;
 323         }
 324
 325         src = kmap_atomic(*rq->in);
 326         if (rq->out[0]) {
 327                 dst = kmap_atomic(rq->out[0]);
 328                 memcpy(dst + rq->pageofs_out, src, righthalf);
 329                 kunmap_atomic(dst);
 330         }
 331
 332         if (nrpages_out == 2) {
 333                 DBG_BUGON(!rq->out[1]);
 334                 if (rq->out[1] == *rq->in) {
 335                         memmove(src, src + righthalf, rq->pageofs_out);
 336                 } else {
 337                         dst = kmap_atomic(rq->out[1]);
 338                         memcpy(dst, src + righthalf, rq->pageofs_out);
 339                         kunmap_atomic(dst);
 340                 }
 341         }
 342         kunmap_atomic(src);
 343         return 0;
 344 }
 345
 346 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 347                        struct list_head *pagepool)
 348 {
 349         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 350                 return z_erofs_shifted_transform(rq, pagepool);
 351         return z_erofs_decompress_generic(rq, pagepool);
 352 }
 353