drivers/staging/erofs/decompressor.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/drivers/staging/erofs/decompressor.c
   4  *
   5  * Copyright (C) 2019 HUAWEI, Inc.
   6  *             http://www.huawei.com/
   7  * Created by Gao Xiang <gaoxiang25@huawei.com>
   8  */
   9 #include "compress.h"
  10 #include <linux/lz4.h>
  11
  12 #ifndef LZ4_DISTANCE_MAX        /* history window size */
  13 #define LZ4_DISTANCE_MAX 65535  /* set to maximum value by default */
  14 #endif
  15
  16 #define LZ4_MAX_DISTANCE_PAGES  (DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
  17 #ifndef LZ4_DECOMPRESS_INPLACE_MARGIN
  18 #define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize)  (((srcsize) >> 8) + 32)
  19 #endif
  20
  21 struct z_erofs_decompressor {
  22         /*
  23          * if destpages have sparsed pages, fill them with bounce pages.
  24          * it also check whether destpages indicate continuous physical memory.
  25          */
  26         int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
  27                                  struct list_head *pagepool);
  28         int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
  29         char *name;
  30 };
  31
  32 static int 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 (kaddr) {
  61                                 if (kaddr + PAGE_SIZE == page_address(page))
  62                                         kaddr += PAGE_SIZE;
  63                                 else
  64                                         kaddr = NULL;
  65                         } else if (!i) {
  66                                 kaddr = page_address(page);
  67                         }
  68                         continue;
  69                 }
  70                 kaddr = NULL;
  71                 __set_bit(j, bounced);
  72
  73                 if (top) {
  74                         victim = availables[--top];
  75                         get_page(victim);
  76                 } else {
  77                         if (!list_empty(pagepool)) {
  78                                 victim = lru_to_page(pagepool);
  79                                 list_del(&victim->lru);
  80                                 DBG_BUGON(page_ref_count(victim) != 1);
  81                         } else {
  82                                 victim = alloc_pages(GFP_KERNEL, 0);
  83                                 if (!victim)
  84                                         return -ENOMEM;
  85                         }
  86                         victim->mapping = Z_EROFS_MAPPING_STAGING;
  87                 }
  88                 rq->out[i] = victim;
  89         }
  90         return kaddr ? 1 : 0;
  91 }
  92
  93 static void *generic_copy_inplace_data(struct z_erofs_decompress_req *rq,
  94                                        u8 *src, unsigned int pageofs_in)
  95 {
  96         /*
  97          * if in-place decompression is ongoing, those decompressed
  98          * pages should be copied in order to avoid being overlapped.
  99          */
 100         struct page **in = rq->in;
 101         u8 *const tmp = erofs_get_pcpubuf(0);
 102         u8 *tmpp = tmp;
 103         unsigned int inlen = rq->inputsize - pageofs_in;
 104         unsigned int count = min_t(uint, inlen, PAGE_SIZE - pageofs_in);
 105
 106         while (tmpp < tmp + inlen) {
 107                 if (!src)
 108                         src = kmap_atomic(*in);
 109                 memcpy(tmpp, src + pageofs_in, count);
 110                 kunmap_atomic(src);
 111                 src = NULL;
 112                 tmpp += count;
 113                 pageofs_in = 0;
 114                 count = PAGE_SIZE;
 115                 ++in;
 116         }
 117         return tmp;
 118 }
 119
 120 static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 121 {
 122         unsigned int inputmargin, inlen;
 123         u8 *src;
 124         bool copied, support_0padding;
 125         int ret;
 126
 127         if (rq->inputsize > PAGE_SIZE)
 128                 return -ENOTSUPP;
 129
 130         src = kmap_atomic(*rq->in);
 131         inputmargin = 0;
 132         support_0padding = false;
 133
 134         /* decompression inplace is only safe when 0padding is enabled */
 135         if (EROFS_SB(rq->sb)->requirements & EROFS_REQUIREMENT_LZ4_0PADDING) {
 136                 support_0padding = true;
 137
 138                 while (!src[inputmargin & ~PAGE_MASK])
 139                         if (!(++inputmargin & ~PAGE_MASK))
 140                                 break;
 141
 142                 if (inputmargin >= rq->inputsize) {
 143                         kunmap_atomic(src);
 144                         return -EIO;
 145                 }
 146         }
 147
 148         copied = false;
 149         inlen = rq->inputsize - inputmargin;
 150         if (rq->inplace_io) {
 151                 const uint oend = (rq->pageofs_out +
 152                                    rq->outputsize) & ~PAGE_MASK;
 153                 const uint nr = PAGE_ALIGN(rq->pageofs_out +
 154                                            rq->outputsize) >> PAGE_SHIFT;
 155
 156                 if (rq->partial_decoding || !support_0padding ||
 157                     rq->out[nr - 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                 }
 164         }
 165
 166         ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 167                                           inlen, rq->outputsize,
 168                                           rq->outputsize);
 169         if (ret < 0) {
 170                 errln("%s, failed to decompress, in[%p, %u, %u] out[%p, %u]",
 171                       __func__, src + inputmargin, inlen, inputmargin,
 172                       out, rq->outputsize);
 173                 WARN_ON(1);
 174                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 175                                16, 1, src + inputmargin, inlen, true);
 176                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 177                                16, 1, out, rq->outputsize, true);
 178                 ret = -EIO;
 179         }
 180
 181         if (copied)
 182                 erofs_put_pcpubuf(src);
 183         else
 184                 kunmap_atomic(src);
 185         return ret;
 186 }
 187
 188 static struct z_erofs_decompressor decompressors[] = {
 189         [Z_EROFS_COMPRESSION_SHIFTED] = {
 190                 .name = "shifted"
 191         },
 192         [Z_EROFS_COMPRESSION_LZ4] = {
 193                 .prepare_destpages = lz4_prepare_destpages,
 194                 .decompress = lz4_decompress,
 195                 .name = "lz4"
 196         },
 197 };
 198
 199 static void copy_from_pcpubuf(struct page **out, const char *dst,
 200                               unsigned short pageofs_out,
 201                               unsigned int outputsize)
 202 {
 203         const char *end = dst + outputsize;
 204         const unsigned int righthalf = PAGE_SIZE - pageofs_out;
 205         const char *cur = dst - pageofs_out;
 206
 207         while (cur < end) {
 208                 struct page *const page = *out++;
 209
 210                 if (page) {
 211                         char *buf = kmap_atomic(page);
 212
 213                         if (cur >= dst) {
 214                                 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
 215                                                        end - cur));
 216                         } else {
 217                                 memcpy(buf + pageofs_out, cur + pageofs_out,
 218                                        min_t(uint, righthalf, end - cur));
 219                         }
 220                         kunmap_atomic(buf);
 221                 }
 222                 cur += PAGE_SIZE;
 223         }
 224 }
 225
 226 static int decompress_generic(struct z_erofs_decompress_req *rq,
 227                               struct list_head *pagepool)
 228 {
 229         const unsigned int nrpages_out =
 230                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 231         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 232         unsigned int dst_maptype;
 233         void *dst;
 234         int ret;
 235
 236         if (nrpages_out == 1 && !rq->inplace_io) {
 237                 DBG_BUGON(!*rq->out);
 238                 dst = kmap_atomic(*rq->out);
 239                 dst_maptype = 0;
 240                 goto dstmap_out;
 241         }
 242
 243         /*
 244          * For the case of small output size (especially much less
 245          * than PAGE_SIZE), memcpy the decompressed data rather than
 246          * compressed data is preferred.
 247          */
 248         if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 249                 dst = erofs_get_pcpubuf(0);
 250                 if (IS_ERR(dst))
 251                         return PTR_ERR(dst);
 252
 253                 rq->inplace_io = false;
 254                 ret = alg->decompress(rq, dst);
 255                 if (!ret)
 256                         copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 257                                           rq->outputsize);
 258
 259                 erofs_put_pcpubuf(dst);
 260                 return ret;
 261         }
 262
 263         ret = alg->prepare_destpages(rq, pagepool);
 264         if (ret < 0) {
 265                 return ret;
 266         } else if (ret) {
 267                 dst = page_address(*rq->out);
 268                 dst_maptype = 1;
 269                 goto dstmap_out;
 270         }
 271
 272         dst = erofs_vmap(rq->out, nrpages_out);
 273         if (!dst)
 274                 return -ENOMEM;
 275         dst_maptype = 2;
 276
 277 dstmap_out:
 278         ret = alg->decompress(rq, dst + rq->pageofs_out);
 279
 280         if (!dst_maptype)
 281                 kunmap_atomic(dst);
 282         else if (dst_maptype == 2)
 283                 erofs_vunmap(dst, nrpages_out);
 284         return ret;
 285 }
 286
 287 static int shifted_decompress(const struct z_erofs_decompress_req *rq,
 288                               struct list_head *pagepool)
 289 {
 290         const unsigned int nrpages_out =
 291                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 292         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 293         unsigned char *src, *dst;
 294
 295         if (nrpages_out > 2) {
 296                 DBG_BUGON(1);
 297                 return -EIO;
 298         }
 299
 300         if (rq->out[0] == *rq->in) {
 301                 DBG_BUGON(nrpages_out != 1);
 302                 return 0;
 303         }
 304
 305         src = kmap_atomic(*rq->in);
 306         if (!rq->out[0]) {
 307                 dst = NULL;
 308         } else {
 309                 dst = kmap_atomic(rq->out[0]);
 310                 memcpy(dst + rq->pageofs_out, src, righthalf);
 311         }
 312
 313         if (rq->out[1] == *rq->in) {
 314                 memmove(src, src + righthalf, rq->pageofs_out);
 315         } else if (nrpages_out == 2) {
 316                 if (dst)
 317                         kunmap_atomic(dst);
 318                 DBG_BUGON(!rq->out[1]);
 319                 dst = kmap_atomic(rq->out[1]);
 320                 memcpy(dst, src + righthalf, rq->pageofs_out);
 321         }
 322         if (dst)
 323                 kunmap_atomic(dst);
 324         kunmap_atomic(src);
 325         return 0;
 326 }
 327
 328 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 329                        struct list_head *pagepool)
 330 {
 331         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 332                 return shifted_decompress(rq, pagepool);
 333         return decompress_generic(rq, pagepool);
 334 }
 335