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 (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);
  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
  86 static 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
 113 static 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
 181 static 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
 192 static 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
 219 static 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
 280 dstmap_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
 290 static 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 = kmap_atomic(rq->out[0]);
 311                 memcpy(dst + rq->pageofs_out, src, righthalf);
 312                 kunmap_atomic(dst);
 313         }
 314
 315         if (nrpages_out == 2) {
 316                 DBG_BUGON(!rq->out[1]);
 317                 if (rq->out[1] == *rq->in) {
 318                         memmove(src, src + righthalf, rq->pageofs_out);
 319                 } else {
 320                         dst = kmap_atomic(rq->out[1]);
 321                         memcpy(dst, src + righthalf, rq->pageofs_out);
 322                         kunmap_atomic(dst);
 323                 }
 324         }
 325         kunmap_atomic(src);
 326         return 0;
 327 }
 328
 329 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 330                        struct list_head *pagepool)
 331 {
 332         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 333                 return z_erofs_shifted_transform(rq, pagepool);
 334         return z_erofs_decompress_generic(rq, pagepool);
 335 }
 336