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 bool use_vmap;
  32 module_param(use_vmap, bool, 0444);
  33 MODULE_PARM_DESC(use_vmap, "Use vmap() instead of vm_map_ram() (default 0)");
  34
  35 static int lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
  36                                  struct list_head *pagepool)
  37 {
  38         const unsigned int nr =
  39                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
  40         struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
  41         unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
  42                                            BITS_PER_LONG)] = { 0 };
  43         void *kaddr = NULL;
  44         unsigned int i, j, top;
  45
  46         top = 0;
  47         for (i = j = 0; i < nr; ++i, ++j) {
  48                 struct page *const page = rq->out[i];
  49                 struct page *victim;
  50
  51                 if (j >= LZ4_MAX_DISTANCE_PAGES)
  52                         j = 0;
  53
  54                 /* 'valid' bounced can only be tested after a complete round */
  55                 if (test_bit(j, bounced)) {
  56                         DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES);
  57                         DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES);
  58                         availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES];
  59                 }
  60
  61                 if (page) {
  62                         __clear_bit(j, bounced);
  63                         if (kaddr) {
  64                                 if (kaddr + PAGE_SIZE == page_address(page))
  65                                         kaddr += PAGE_SIZE;
  66                                 else
  67                                         kaddr = NULL;
  68                         } else if (!i) {
  69                                 kaddr = page_address(page);
  70                         }
  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 (unlikely(!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 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)->requirements & EROFS_REQUIREMENT_LZ4_0PADDING) {
 133                 support_0padding = true;
 134
 135                 while (!src[inputmargin & ~PAGE_MASK])
 136                         if (!(++inputmargin & ~PAGE_MASK))
 137                                 break;
 138
 139                 if (inputmargin >= rq->inputsize) {
 140                         kunmap_atomic(src);
 141                         return -EIO;
 142                 }
 143         }
 144
 145         copied = false;
 146         inlen = rq->inputsize - inputmargin;
 147         if (rq->inplace_io) {
 148                 const uint oend = (rq->pageofs_out +
 149                                    rq->outputsize) & ~PAGE_MASK;
 150                 const uint nr = PAGE_ALIGN(rq->pageofs_out +
 151                                            rq->outputsize) >> PAGE_SHIFT;
 152
 153                 if (rq->partial_decoding || !support_0padding ||
 154                     rq->out[nr - 1] != rq->in[0] ||
 155                     rq->inputsize - oend <
 156                       LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) {
 157                         src = generic_copy_inplace_data(rq, src, inputmargin);
 158                         inputmargin = 0;
 159                         copied = true;
 160                 }
 161         }
 162
 163         ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 164                                           inlen, rq->outputsize,
 165                                           rq->outputsize);
 166         if (ret < 0) {
 167                 errln("%s, failed to decompress, in[%p, %u, %u] out[%p, %u]",
 168                       __func__, src + inputmargin, inlen, inputmargin,
 169                       out, 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 = lz4_prepare_destpages,
 191                 .decompress = 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 void *erofs_vmap(struct page **pages, unsigned int count)
 224 {
 225         int i = 0;
 226
 227         if (use_vmap)
 228                 return vmap(pages, count, VM_MAP, PAGE_KERNEL);
 229
 230         while (1) {
 231                 void *addr = vm_map_ram(pages, count, -1, PAGE_KERNEL);
 232
 233                 /* retry two more times (totally 3 times) */
 234                 if (addr || ++i >= 3)
 235                         return addr;
 236                 vm_unmap_aliases();
 237         }
 238         return NULL;
 239 }
 240
 241 static void erofs_vunmap(const void *mem, unsigned int count)
 242 {
 243         if (!use_vmap)
 244                 vm_unmap_ram(mem, count);
 245         else
 246                 vunmap(mem);
 247 }
 248
 249 static int decompress_generic(struct z_erofs_decompress_req *rq,
 250                               struct list_head *pagepool)
 251 {
 252         const unsigned int nrpages_out =
 253                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 254         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 255         unsigned int dst_maptype;
 256         void *dst;
 257         int ret;
 258
 259         if (nrpages_out == 1 && !rq->inplace_io) {
 260                 DBG_BUGON(!*rq->out);
 261                 dst = kmap_atomic(*rq->out);
 262                 dst_maptype = 0;
 263                 goto dstmap_out;
 264         }
 265
 266         /*
 267          * For the case of small output size (especially much less
 268          * than PAGE_SIZE), memcpy the decompressed data rather than
 269          * compressed data is preferred.
 270          */
 271         if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 272                 dst = erofs_get_pcpubuf(0);
 273                 if (IS_ERR(dst))
 274                         return PTR_ERR(dst);
 275
 276                 rq->inplace_io = false;
 277                 ret = alg->decompress(rq, dst);
 278                 if (!ret)
 279                         copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 280                                           rq->outputsize);
 281
 282                 erofs_put_pcpubuf(dst);
 283                 return ret;
 284         }
 285
 286         ret = alg->prepare_destpages(rq, pagepool);
 287         if (ret < 0) {
 288                 return ret;
 289         } else if (ret) {
 290                 dst = page_address(*rq->out);
 291                 dst_maptype = 1;
 292                 goto dstmap_out;
 293         }
 294
 295         dst = erofs_vmap(rq->out, nrpages_out);
 296         if (!dst)
 297                 return -ENOMEM;
 298         dst_maptype = 2;
 299
 300 dstmap_out:
 301         ret = alg->decompress(rq, dst + rq->pageofs_out);
 302
 303         if (!dst_maptype)
 304                 kunmap_atomic(dst);
 305         else if (dst_maptype == 2)
 306                 erofs_vunmap(dst, nrpages_out);
 307         return ret;
 308 }
 309
 310 static int shifted_decompress(const struct z_erofs_decompress_req *rq,
 311                               struct list_head *pagepool)
 312 {
 313         const unsigned int nrpages_out =
 314                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 315         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 316         unsigned char *src, *dst;
 317
 318         if (nrpages_out > 2) {
 319                 DBG_BUGON(1);
 320                 return -EIO;
 321         }
 322
 323         if (rq->out[0] == *rq->in) {
 324                 DBG_BUGON(nrpages_out != 1);
 325                 return 0;
 326         }
 327
 328         src = kmap_atomic(*rq->in);
 329         if (!rq->out[0]) {
 330                 dst = NULL;
 331         } else {
 332                 dst = kmap_atomic(rq->out[0]);
 333                 memcpy(dst + rq->pageofs_out, src, righthalf);
 334         }
 335
 336         if (rq->out[1] == *rq->in) {
 337                 memmove(src, src + righthalf, rq->pageofs_out);
 338         } else if (nrpages_out == 2) {
 339                 if (dst)
 340                         kunmap_atomic(dst);
 341                 DBG_BUGON(!rq->out[1]);
 342                 dst = kmap_atomic(rq->out[1]);
 343                 memcpy(dst, src + righthalf, rq->pageofs_out);
 344         }
 345         if (dst)
 346                 kunmap_atomic(dst);
 347         kunmap_atomic(src);
 348         return 0;
 349 }
 350
 351 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 352                        struct list_head *pagepool)
 353 {
 354         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 355                 return shifted_decompress(rq, pagepool);
 356         return decompress_generic(rq, pagepool);
 357 }
 358