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  */
   6 #include "compress.h"
   7 #include <linux/module.h>
   8 #include <linux/lz4.h>
   9
  10 #ifndef LZ4_DISTANCE_MAX        /* history window size */
  11 #define LZ4_DISTANCE_MAX 65535  /* set to maximum value by default */
  12 #endif
  13
  14 #define LZ4_MAX_DISTANCE_PAGES  (DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
  15 #ifndef LZ4_DECOMPRESS_INPLACE_MARGIN
  16 #define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize)  (((srcsize) >> 8) + 32)
  17 #endif
  18
  19 struct z_erofs_decompressor {
  20         /*
  21          * if destpages have sparsed pages, fill them with bounce pages.
  22          * it also check whether destpages indicate continuous physical memory.
  23          */
  24         int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
  25                                  struct list_head *pagepool);
  26         int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
  27         char *name;
  28 };
  29
  30 int z_erofs_load_lz4_config(struct super_block *sb,
  31                             struct erofs_super_block *dsb,
  32                             struct z_erofs_lz4_cfgs *lz4, int size)
  33 {
  34         struct erofs_sb_info *sbi = EROFS_SB(sb);
  35         u16 distance;
  36
  37         if (lz4) {
  38                 if (size < sizeof(struct z_erofs_lz4_cfgs)) {
  39                         erofs_err(sb, "invalid lz4 cfgs, size=%u", size);
  40                         return -EINVAL;
  41                 }
  42                 distance = le16_to_cpu(lz4->max_distance);
  43
  44                 sbi->lz4.max_pclusterblks = le16_to_cpu(lz4->max_pclusterblks);
  45                 if (!sbi->lz4.max_pclusterblks) {
  46                         sbi->lz4.max_pclusterblks = 1;  /* reserved case */
  47                 } else if (sbi->lz4.max_pclusterblks >
  48                            Z_EROFS_PCLUSTER_MAX_SIZE / EROFS_BLKSIZ) {
  49                         erofs_err(sb, "too large lz4 pclusterblks %u",
  50                                   sbi->lz4.max_pclusterblks);
  51                         return -EINVAL;
  52                 } else if (sbi->lz4.max_pclusterblks >= 2) {
  53                         erofs_info(sb, "EXPERIMENTAL big pcluster feature in use. Use at your own risk!");
  54                 }
  55         } else {
  56                 distance = le16_to_cpu(dsb->u1.lz4_max_distance);
  57                 sbi->lz4.max_pclusterblks = 1;
  58         }
  59
  60         sbi->lz4.max_distance_pages = distance ?
  61                                         DIV_ROUND_UP(distance, PAGE_SIZE) + 1 :
  62                                         LZ4_MAX_DISTANCE_PAGES;
  63         return erofs_pcpubuf_growsize(sbi->lz4.max_pclusterblks);
  64 }
  65
  66 static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
  67                                          struct list_head *pagepool)
  68 {
  69         const unsigned int nr =
  70                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
  71         struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
  72         unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
  73                                            BITS_PER_LONG)] = { 0 };
  74         unsigned int lz4_max_distance_pages =
  75                                 EROFS_SB(rq->sb)->lz4.max_distance_pages;
  76         void *kaddr = NULL;
  77         unsigned int i, j, top;
  78
  79         top = 0;
  80         for (i = j = 0; i < nr; ++i, ++j) {
  81                 struct page *const page = rq->out[i];
  82                 struct page *victim;
  83
  84                 if (j >= lz4_max_distance_pages)
  85                         j = 0;
  86
  87                 /* 'valid' bounced can only be tested after a complete round */
  88                 if (test_bit(j, bounced)) {
  89                         DBG_BUGON(i < lz4_max_distance_pages);
  90                         DBG_BUGON(top >= lz4_max_distance_pages);
  91                         availables[top++] = rq->out[i - lz4_max_distance_pages];
  92                 }
  93
  94                 if (page) {
  95                         __clear_bit(j, bounced);
  96                         if (kaddr) {
  97                                 if (kaddr + PAGE_SIZE == page_address(page))
  98                                         kaddr += PAGE_SIZE;
  99                                 else
 100                                         kaddr = NULL;
 101                         } else if (!i) {
 102                                 kaddr = page_address(page);
 103                         }
 104                         continue;
 105                 }
 106                 kaddr = NULL;
 107                 __set_bit(j, bounced);
 108
 109                 if (top) {
 110                         victim = availables[--top];
 111                         get_page(victim);
 112                 } else {
 113                         victim = erofs_allocpage(pagepool,
 114                                                  GFP_KERNEL | __GFP_NOFAIL);
 115                         set_page_private(victim, Z_EROFS_SHORTLIVED_PAGE);
 116                 }
 117                 rq->out[i] = victim;
 118         }
 119         return kaddr ? 1 : 0;
 120 }
 121
 122 static void *z_erofs_handle_inplace_io(struct z_erofs_decompress_req *rq,
 123                         void *inpage, unsigned int *inputmargin, int *maptype,
 124                         bool support_0padding)
 125 {
 126         unsigned int nrpages_in, nrpages_out;
 127         unsigned int ofull, oend, inputsize, total, i, j;
 128         struct page **in;
 129         void *src, *tmp;
 130
 131         inputsize = rq->inputsize;
 132         nrpages_in = PAGE_ALIGN(inputsize) >> PAGE_SHIFT;
 133         oend = rq->pageofs_out + rq->outputsize;
 134         ofull = PAGE_ALIGN(oend);
 135         nrpages_out = ofull >> PAGE_SHIFT;
 136
 137         if (rq->inplace_io) {
 138                 if (rq->partial_decoding || !support_0padding ||
 139                     ofull - oend < LZ4_DECOMPRESS_INPLACE_MARGIN(inputsize))
 140                         goto docopy;
 141
 142                 for (i = 0; i < nrpages_in; ++i) {
 143                         DBG_BUGON(rq->in[i] == NULL);
 144                         for (j = 0; j < nrpages_out - nrpages_in + i; ++j)
 145                                 if (rq->out[j] == rq->in[i])
 146                                         goto docopy;
 147                 }
 148         }
 149
 150         if (nrpages_in <= 1) {
 151                 *maptype = 0;
 152                 return inpage;
 153         }
 154         kunmap_atomic(inpage);
 155         might_sleep();
 156         src = erofs_vm_map_ram(rq->in, nrpages_in);
 157         if (!src)
 158                 return ERR_PTR(-ENOMEM);
 159         *maptype = 1;
 160         return src;
 161
 162 docopy:
 163         /* Or copy compressed data which can be overlapped to per-CPU buffer */
 164         in = rq->in;
 165         src = erofs_get_pcpubuf(nrpages_in);
 166         if (!src) {
 167                 DBG_BUGON(1);
 168                 kunmap_atomic(inpage);
 169                 return ERR_PTR(-EFAULT);
 170         }
 171
 172         tmp = src;
 173         total = rq->inputsize;
 174         while (total) {
 175                 unsigned int page_copycnt =
 176                         min_t(unsigned int, total, PAGE_SIZE - *inputmargin);
 177
 178                 if (!inpage)
 179                         inpage = kmap_atomic(*in);
 180                 memcpy(tmp, inpage + *inputmargin, page_copycnt);
 181                 kunmap_atomic(inpage);
 182                 inpage = NULL;
 183                 tmp += page_copycnt;
 184                 total -= page_copycnt;
 185                 ++in;
 186                 *inputmargin = 0;
 187         }
 188         *maptype = 2;
 189         return src;
 190 }
 191
 192 static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 193 {
 194         unsigned int inputmargin;
 195         u8 *headpage, *src;
 196         bool support_0padding;
 197         int ret, maptype;
 198
 199         DBG_BUGON(*rq->in == NULL);
 200         headpage = kmap_atomic(*rq->in);
 201         inputmargin = 0;
 202         support_0padding = false;
 203
 204         /* decompression inplace is only safe when 0padding is enabled */
 205         if (erofs_sb_has_lz4_0padding(EROFS_SB(rq->sb))) {
 206                 support_0padding = true;
 207
 208                 while (!headpage[inputmargin & ~PAGE_MASK])
 209                         if (!(++inputmargin & ~PAGE_MASK))
 210                                 break;
 211
 212                 if (inputmargin >= rq->inputsize) {
 213                         kunmap_atomic(headpage);
 214                         return -EIO;
 215                 }
 216         }
 217
 218         rq->inputsize -= inputmargin;
 219         src = z_erofs_handle_inplace_io(rq, headpage, &inputmargin, &maptype,
 220                                         support_0padding);
 221         if (IS_ERR(src))
 222                 return PTR_ERR(src);
 223
 224         /* legacy format could compress extra data in a pcluster. */
 225         if (rq->partial_decoding || !support_0padding)
 226                 ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 227                                 rq->inputsize, rq->outputsize, rq->outputsize);
 228         else
 229                 ret = LZ4_decompress_safe(src + inputmargin, out,
 230                                           rq->inputsize, rq->outputsize);
 231
 232         if (ret != rq->outputsize) {
 233                 erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]",
 234                           ret, rq->inputsize, inputmargin, rq->outputsize);
 235
 236                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 237                                16, 1, src + inputmargin, rq->inputsize, true);
 238                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 239                                16, 1, out, rq->outputsize, true);
 240
 241                 if (ret >= 0)
 242                         memset(out + ret, 0, rq->outputsize - ret);
 243                 ret = -EIO;
 244         }
 245
 246         if (maptype == 0) {
 247                 kunmap_atomic(src);
 248         } else if (maptype == 1) {
 249                 vm_unmap_ram(src, PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT);
 250         } else if (maptype == 2) {
 251                 erofs_put_pcpubuf(src);
 252         } else {
 253                 DBG_BUGON(1);
 254                 return -EFAULT;
 255         }
 256         return ret;
 257 }
 258
 259 static struct z_erofs_decompressor decompressors[] = {
 260         [Z_EROFS_COMPRESSION_SHIFTED] = {
 261                 .name = "shifted"
 262         },
 263         [Z_EROFS_COMPRESSION_LZ4] = {
 264                 .prepare_destpages = z_erofs_lz4_prepare_destpages,
 265                 .decompress = z_erofs_lz4_decompress,
 266                 .name = "lz4"
 267         },
 268 };
 269
 270 static void copy_from_pcpubuf(struct page **out, const char *dst,
 271                               unsigned short pageofs_out,
 272                               unsigned int outputsize)
 273 {
 274         const char *end = dst + outputsize;
 275         const unsigned int righthalf = PAGE_SIZE - pageofs_out;
 276         const char *cur = dst - pageofs_out;
 277
 278         while (cur < end) {
 279                 struct page *const page = *out++;
 280
 281                 if (page) {
 282                         char *buf = kmap_atomic(page);
 283
 284                         if (cur >= dst) {
 285                                 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
 286                                                        end - cur));
 287                         } else {
 288                                 memcpy(buf + pageofs_out, cur + pageofs_out,
 289                                        min_t(uint, righthalf, end - cur));
 290                         }
 291                         kunmap_atomic(buf);
 292                 }
 293                 cur += PAGE_SIZE;
 294         }
 295 }
 296
 297 static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
 298                                       struct list_head *pagepool)
 299 {
 300         const unsigned int nrpages_out =
 301                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 302         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 303         unsigned int dst_maptype;
 304         void *dst;
 305         int ret;
 306
 307         /* two optimized fast paths only for non bigpcluster cases yet */
 308         if (rq->inputsize <= PAGE_SIZE) {
 309                 if (nrpages_out == 1 && !rq->inplace_io) {
 310                         DBG_BUGON(!*rq->out);
 311                         dst = kmap_atomic(*rq->out);
 312                         dst_maptype = 0;
 313                         goto dstmap_out;
 314                 }
 315
 316                 /*
 317                  * For the case of small output size (especially much less
 318                  * than PAGE_SIZE), memcpy the decompressed data rather than
 319                  * compressed data is preferred.
 320                  */
 321                 if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 322                         dst = erofs_get_pcpubuf(1);
 323                         if (IS_ERR(dst))
 324                                 return PTR_ERR(dst);
 325
 326                         rq->inplace_io = false;
 327                         ret = alg->decompress(rq, dst);
 328                         if (!ret)
 329                                 copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 330                                                   rq->outputsize);
 331
 332                         erofs_put_pcpubuf(dst);
 333                         return ret;
 334                 }
 335         }
 336
 337         /* general decoding path which can be used for all cases */
 338         ret = alg->prepare_destpages(rq, pagepool);
 339         if (ret < 0)
 340                 return ret;
 341         if (ret) {
 342                 dst = page_address(*rq->out);
 343                 dst_maptype = 1;
 344                 goto dstmap_out;
 345         }
 346
 347         dst = erofs_vm_map_ram(rq->out, nrpages_out);
 348         if (!dst)
 349                 return -ENOMEM;
 350         dst_maptype = 2;
 351
 352 dstmap_out:
 353         ret = alg->decompress(rq, dst + rq->pageofs_out);
 354
 355         if (!dst_maptype)
 356                 kunmap_atomic(dst);
 357         else if (dst_maptype == 2)
 358                 vm_unmap_ram(dst, nrpages_out);
 359         return ret;
 360 }
 361
 362 static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
 363                                      struct list_head *pagepool)
 364 {
 365         const unsigned int nrpages_out =
 366                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 367         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 368         unsigned char *src, *dst;
 369
 370         if (nrpages_out > 2) {
 371                 DBG_BUGON(1);
 372                 return -EIO;
 373         }
 374
 375         if (rq->out[0] == *rq->in) {
 376                 DBG_BUGON(nrpages_out != 1);
 377                 return 0;
 378         }
 379
 380         src = kmap_atomic(*rq->in);
 381         if (rq->out[0]) {
 382                 dst = kmap_atomic(rq->out[0]);
 383                 memcpy(dst + rq->pageofs_out, src, righthalf);
 384                 kunmap_atomic(dst);
 385         }
 386
 387         if (nrpages_out == 2) {
 388                 DBG_BUGON(!rq->out[1]);
 389                 if (rq->out[1] == *rq->in) {
 390                         memmove(src, src + righthalf, rq->pageofs_out);
 391                 } else {
 392                         dst = kmap_atomic(rq->out[1]);
 393                         memcpy(dst, src + righthalf, rq->pageofs_out);
 394                         kunmap_atomic(dst);
 395                 }
 396         }
 397         kunmap_atomic(src);
 398         return 0;
 399 }
 400
 401 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 402                        struct list_head *pagepool)
 403 {
 404         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 405                 return z_erofs_shifted_transform(rq, pagepool);
 406         return z_erofs_decompress_generic(rq, pagepool);
 407 }