drivers/staging/erofs/decompressor.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   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/module.h>
  11 #include <linux/lz4.h>
  12
  13 #ifndef LZ4_DISTANCE_MAX        /* history window size */
  14 #define LZ4_DISTANCE_MAX 65535  /* set to maximum value by default */
  15 #endif
  16
  17 #define LZ4_MAX_DISTANCE_PAGES  (DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
  18 #ifndef LZ4_DECOMPRESS_INPLACE_MARGIN
  19 #define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize)  (((srcsize) >> 8) + 32)
  20 #endif
  21
  22 struct z_erofs_decompressor {
  23         /*
  24          * if destpages have sparsed pages, fill them with bounce pages.
  25          * it also check whether destpages indicate continuous physical memory.
  26          */
  27         int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
  28                                  struct list_head *pagepool);
  29         int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
  30         char *name;
  31 };
  32
  33 static bool use_vmap;
  34 module_param(use_vmap, bool, 0444);
  35 MODULE_PARM_DESC(use_vmap, "Use vmap() instead of vm_map_ram() (default 0)");
  36
  37 static int lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
  38                                  struct list_head *pagepool)
  39 {
  40         const unsigned int nr =
  41                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
  42         struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
  43         unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
  44                                            BITS_PER_LONG)] = { 0 };
  45         void *kaddr = NULL;
  46         unsigned int i, j, top;
  47
  48         top = 0;
  49         for (i = j = 0; i < nr; ++i, ++j) {
  50                 struct page *const page = rq->out[i];
  51                 struct page *victim;
  52
  53                 if (j >= LZ4_MAX_DISTANCE_PAGES)
  54                         j = 0;
  55
  56                 /* 'valid' bounced can only be tested after a complete round */
  57                 if (test_bit(j, bounced)) {
  58                         DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES);
  59                         DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES);
  60                         availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES];
  61                 }
  62
  63                 if (page) {
  64                         __clear_bit(j, bounced);
  65                         if (kaddr) {
  66                                 if (kaddr + PAGE_SIZE == page_address(page))
  67                                         kaddr += PAGE_SIZE;
  68                                 else
  69                                         kaddr = NULL;
  70                         } else if (!i) {
  71                                 kaddr = page_address(page);
  72                         }
  73                         continue;
  74                 }
  75                 kaddr = NULL;
  76                 __set_bit(j, bounced);
  77
  78                 if (top) {
  79                         victim = availables[--top];
  80                         get_page(victim);
  81                 } else {
  82                         victim = erofs_allocpage(pagepool, GFP_KERNEL, false);
  83                         if (unlikely(!victim))
  84                                 return -ENOMEM;
  85                         victim->mapping = Z_EROFS_MAPPING_STAGING;
  86                 }
  87                 rq->out[i] = victim;
  88         }
  89         return kaddr ? 1 : 0;
  90 }
  91
  92 static void *generic_copy_inplace_data(struct z_erofs_decompress_req *rq,
  93                                        u8 *src, unsigned int pageofs_in)
  94 {
  95         /*
  96          * if in-place decompression is ongoing, those decompressed
  97          * pages should be copied in order to avoid being overlapped.
  98          */
  99         struct page **in = rq->in;
 100         u8 *const tmp = erofs_get_pcpubuf(0);
 101         u8 *tmpp = tmp;
 102         unsigned int inlen = rq->inputsize - pageofs_in;
 103         unsigned int count = min_t(uint, inlen, PAGE_SIZE - pageofs_in);
 104
 105         while (tmpp < tmp + inlen) {
 106                 if (!src)
 107                         src = kmap_atomic(*in);
 108                 memcpy(tmpp, src + pageofs_in, count);
 109                 kunmap_atomic(src);
 110                 src = NULL;
 111                 tmpp += count;
 112                 pageofs_in = 0;
 113                 count = PAGE_SIZE;
 114                 ++in;
 115         }
 116         return tmp;
 117 }
 118
 119 static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 120 {
 121         unsigned int inputmargin, inlen;
 122         u8 *src;
 123         bool copied, support_0padding;
 124         int ret;
 125
 126         if (rq->inputsize > PAGE_SIZE)
 127                 return -EOPNOTSUPP;
 128
 129         src = kmap_atomic(*rq->in);
 130         inputmargin = 0;
 131         support_0padding = false;
 132
 133         /* decompression inplace is only safe when 0padding is enabled */
 134         if (EROFS_SB(rq->sb)->requirements & EROFS_REQUIREMENT_LZ4_0PADDING) {
 135                 support_0padding = true;
 136
 137                 while (!src[inputmargin & ~PAGE_MASK])
 138                         if (!(++inputmargin & ~PAGE_MASK))
 139                                 break;
 140
 141                 if (inputmargin >= rq->inputsize) {
 142                         kunmap_atomic(src);
 143                         return -EIO;
 144                 }
 145         }
 146
 147         copied = false;
 148         inlen = rq->inputsize - inputmargin;
 149         if (rq->inplace_io) {
 150                 const uint oend = (rq->pageofs_out +
 151                                    rq->outputsize) & ~PAGE_MASK;
 152                 const uint nr = PAGE_ALIGN(rq->pageofs_out +
 153                                            rq->outputsize) >> PAGE_SHIFT;
 154
 155                 if (rq->partial_decoding || !support_0padding ||
 156                     rq->out[nr - 1] != rq->in[0] ||
 157                     rq->inputsize - oend <
 158                       LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) {
 159                         src = generic_copy_inplace_data(rq, src, inputmargin);
 160                         inputmargin = 0;
 161                         copied = true;
 162                 }
 163         }
 164
 165         ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 166                                           inlen, rq->outputsize,
 167                                           rq->outputsize);
 168         if (ret < 0) {
 169                 errln("%s, failed to decompress, in[%p, %u, %u] out[%p, %u]",
 170                       __func__, src + inputmargin, inlen, inputmargin,
 171                       out, rq->outputsize);
 172                 WARN_ON(1);
 173                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 174                                16, 1, src + inputmargin, inlen, true);
 175                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 176                                16, 1, out, rq->outputsize, true);
 177                 ret = -EIO;
 178         }
 179
 180         if (copied)
 181                 erofs_put_pcpubuf(src);
 182         else
 183                 kunmap_atomic(src);
 184         return ret;
 185 }
 186
 187 static struct z_erofs_decompressor decompressors[] = {
 188         [Z_EROFS_COMPRESSION_SHIFTED] = {
 189                 .name = "shifted"
 190         },
 191         [Z_EROFS_COMPRESSION_LZ4] = {
 192                 .prepare_destpages = lz4_prepare_destpages,
 193                 .decompress = lz4_decompress,
 194                 .name = "lz4"
 195         },
 196 };
 197
 198 static void copy_from_pcpubuf(struct page **out, const char *dst,
 199                               unsigned short pageofs_out,
 200                               unsigned int outputsize)
 201 {
 202         const char *end = dst + outputsize;
 203         const unsigned int righthalf = PAGE_SIZE - pageofs_out;
 204         const char *cur = dst - pageofs_out;
 205
 206         while (cur < end) {
 207                 struct page *const page = *out++;
 208
 209                 if (page) {
 210                         char *buf = kmap_atomic(page);
 211
 212                         if (cur >= dst) {
 213                                 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
 214                                                        end - cur));
 215                         } else {
 216                                 memcpy(buf + pageofs_out, cur + pageofs_out,
 217                                        min_t(uint, righthalf, end - cur));
 218                         }
 219                         kunmap_atomic(buf);
 220                 }
 221                 cur += PAGE_SIZE;
 222         }
 223 }
 224
 225 static void *erofs_vmap(struct page **pages, unsigned int count)
 226 {
 227         int i = 0;
 228
 229         if (use_vmap)
 230                 return vmap(pages, count, VM_MAP, PAGE_KERNEL);
 231
 232         while (1) {
 233                 void *addr = vm_map_ram(pages, count, -1, PAGE_KERNEL);
 234
 235                 /* retry two more times (totally 3 times) */
 236                 if (addr || ++i >= 3)
 237                         return addr;
 238                 vm_unmap_aliases();
 239         }
 240         return NULL;
 241 }
 242
 243 static void erofs_vunmap(const void *mem, unsigned int count)
 244 {
 245         if (!use_vmap)
 246                 vm_unmap_ram(mem, count);
 247         else
 248                 vunmap(mem);
 249 }
 250
 251 static int decompress_generic(struct z_erofs_decompress_req *rq,
 252                               struct list_head *pagepool)
 253 {
 254         const unsigned int nrpages_out =
 255                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 256         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 257         unsigned int dst_maptype;
 258         void *dst;
 259         int ret;
 260
 261         if (nrpages_out == 1 && !rq->inplace_io) {
 262                 DBG_BUGON(!*rq->out);
 263                 dst = kmap_atomic(*rq->out);
 264                 dst_maptype = 0;
 265                 goto dstmap_out;
 266         }
 267
 268         /*
 269          * For the case of small output size (especially much less
 270          * than PAGE_SIZE), memcpy the decompressed data rather than
 271          * compressed data is preferred.
 272          */
 273         if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 274                 dst = erofs_get_pcpubuf(0);
 275                 if (IS_ERR(dst))
 276                         return PTR_ERR(dst);
 277
 278                 rq->inplace_io = false;
 279                 ret = alg->decompress(rq, dst);
 280                 if (!ret)
 281                         copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 282                                           rq->outputsize);
 283
 284                 erofs_put_pcpubuf(dst);
 285                 return ret;
 286         }
 287
 288         ret = alg->prepare_destpages(rq, pagepool);
 289         if (ret < 0) {
 290                 return ret;
 291         } else if (ret) {
 292                 dst = page_address(*rq->out);
 293                 dst_maptype = 1;
 294                 goto dstmap_out;
 295         }
 296
 297         dst = erofs_vmap(rq->out, nrpages_out);
 298         if (!dst)
 299                 return -ENOMEM;
 300         dst_maptype = 2;
 301
 302 dstmap_out:
 303         ret = alg->decompress(rq, dst + rq->pageofs_out);
 304
 305         if (!dst_maptype)
 306                 kunmap_atomic(dst);
 307         else if (dst_maptype == 2)
 308                 erofs_vunmap(dst, nrpages_out);
 309         return ret;
 310 }
 311
 312 static int shifted_decompress(const struct z_erofs_decompress_req *rq,
 313                               struct list_head *pagepool)
 314 {
 315         const unsigned int nrpages_out =
 316                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 317         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 318         unsigned char *src, *dst;
 319
 320         if (nrpages_out > 2) {
 321                 DBG_BUGON(1);
 322                 return -EIO;
 323         }
 324
 325         if (rq->out[0] == *rq->in) {
 326                 DBG_BUGON(nrpages_out != 1);
 327                 return 0;
 328         }
 329
 330         src = kmap_atomic(*rq->in);
 331         if (!rq->out[0]) {
 332                 dst = NULL;
 333         } else {
 334                 dst = kmap_atomic(rq->out[0]);
 335                 memcpy(dst + rq->pageofs_out, src, righthalf);
 336         }
 337
 338         if (rq->out[1] == *rq->in) {
 339                 memmove(src, src + righthalf, rq->pageofs_out);
 340         } else if (nrpages_out == 2) {
 341                 if (dst)
 342                         kunmap_atomic(dst);
 343                 DBG_BUGON(!rq->out[1]);
 344                 dst = kmap_atomic(rq->out[1]);
 345                 memcpy(dst, src + righthalf, rq->pageofs_out);
 346         }
 347         if (dst)
 348                 kunmap_atomic(dst);
 349         kunmap_atomic(src);
 350         return 0;
 351 }
 352
 353 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 354                        struct list_head *pagepool)
 355 {
 356         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 357                 return shifted_decompress(rq, pagepool);
 358         return decompress_generic(rq, pagepool);
 359 }
 360