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  * 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 int z_erofs_load_lz4_config(struct super_block *sb,
  32                             struct erofs_super_block *dsb,
  33                             struct z_erofs_lz4_cfgs *lz4, int size)
  34 {
  35         struct erofs_sb_info *sbi = EROFS_SB(sb);
  36         u16 distance;
  37
  38         if (lz4) {
  39                 if (size < sizeof(struct z_erofs_lz4_cfgs)) {
  40                         erofs_err(sb, "invalid lz4 cfgs, size=%u", size);
  41                         return -EINVAL;
  42                 }
  43                 distance = le16_to_cpu(lz4->max_distance);
  44
  45                 sbi->lz4.max_pclusterblks = le16_to_cpu(lz4->max_pclusterblks);
  46                 if (!sbi->lz4.max_pclusterblks) {
  47                         sbi->lz4.max_pclusterblks = 1;  /* reserved case */
  48                 } else if (sbi->lz4.max_pclusterblks >
  49                            Z_EROFS_PCLUSTER_MAX_SIZE / EROFS_BLKSIZ) {
  50                         erofs_err(sb, "too large lz4 pclusterblks %u",
  51                                   sbi->lz4.max_pclusterblks);
  52                         return -EINVAL;
  53                 } else if (sbi->lz4.max_pclusterblks >= 2) {
  54                         erofs_info(sb, "EXPERIMENTAL big pcluster feature in use. Use at your own risk!");
  55                 }
  56         } else {
  57                 distance = le16_to_cpu(dsb->u1.lz4_max_distance);
  58                 sbi->lz4.max_pclusterblks = 1;
  59         }
  60
  61         sbi->lz4.max_distance_pages = distance ?
  62                                         DIV_ROUND_UP(distance, PAGE_SIZE) + 1 :
  63                                         LZ4_MAX_DISTANCE_PAGES;
  64         return erofs_pcpubuf_growsize(sbi->lz4.max_pclusterblks);
  65 }
  66
  67 static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
  68                                          struct list_head *pagepool)
  69 {
  70         const unsigned int nr =
  71                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
  72         struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
  73         unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
  74                                            BITS_PER_LONG)] = { 0 };
  75         unsigned int lz4_max_distance_pages =
  76                                 EROFS_SB(rq->sb)->lz4.max_distance_pages;
  77         void *kaddr = NULL;
  78         unsigned int i, j, top;
  79
  80         top = 0;
  81         for (i = j = 0; i < nr; ++i, ++j) {
  82                 struct page *const page = rq->out[i];
  83                 struct page *victim;
  84
  85                 if (j >= lz4_max_distance_pages)
  86                         j = 0;
  87
  88                 /* 'valid' bounced can only be tested after a complete round */
  89                 if (test_bit(j, bounced)) {
  90                         DBG_BUGON(i < lz4_max_distance_pages);
  91                         DBG_BUGON(top >= lz4_max_distance_pages);
  92                         availables[top++] = rq->out[i - lz4_max_distance_pages];
  93                 }
  94
  95                 if (page) {
  96                         __clear_bit(j, bounced);
  97                         if (kaddr) {
  98                                 if (kaddr + PAGE_SIZE == page_address(page))
  99                                         kaddr += PAGE_SIZE;
 100                                 else
 101                                         kaddr = NULL;
 102                         } else if (!i) {
 103                                 kaddr = page_address(page);
 104                         }
 105                         continue;
 106                 }
 107                 kaddr = NULL;
 108                 __set_bit(j, bounced);
 109
 110                 if (top) {
 111                         victim = availables[--top];
 112                         get_page(victim);
 113                 } else {
 114                         victim = erofs_allocpage(pagepool,
 115                                                  GFP_KERNEL | __GFP_NOFAIL);
 116                         set_page_private(victim, Z_EROFS_SHORTLIVED_PAGE);
 117                 }
 118                 rq->out[i] = victim;
 119         }
 120         return kaddr ? 1 : 0;
 121 }
 122
 123 static void *z_erofs_handle_inplace_io(struct z_erofs_decompress_req *rq,
 124                         void *inpage, unsigned int *inputmargin, int *maptype,
 125                         bool support_0padding)
 126 {
 127         unsigned int nrpages_in, nrpages_out;
 128         unsigned int ofull, oend, inputsize, total, i, j;
 129         struct page **in;
 130         void *src, *tmp;
 131
 132         inputsize = rq->inputsize;
 133         nrpages_in = PAGE_ALIGN(inputsize) >> PAGE_SHIFT;
 134         oend = rq->pageofs_out + rq->outputsize;
 135         ofull = PAGE_ALIGN(oend);
 136         nrpages_out = ofull >> PAGE_SHIFT;
 137
 138         if (rq->inplace_io) {
 139                 if (rq->partial_decoding || !support_0padding ||
 140                     ofull - oend < LZ4_DECOMPRESS_INPLACE_MARGIN(inputsize))
 141                         goto docopy;
 142
 143                 for (i = 0; i < nrpages_in; ++i) {
 144                         DBG_BUGON(rq->in[i] == NULL);
 145                         for (j = 0; j < nrpages_out - nrpages_in + i; ++j)
 146                                 if (rq->out[j] == rq->in[i])
 147                                         goto docopy;
 148                 }
 149         }
 150
 151         if (nrpages_in <= 1) {
 152                 *maptype = 0;
 153                 return inpage;
 154         }
 155         kunmap_atomic(inpage);
 156         might_sleep();
 157         src = erofs_vm_map_ram(rq->in, nrpages_in);
 158         if (!src)
 159                 return ERR_PTR(-ENOMEM);
 160         *maptype = 1;
 161         return src;
 162
 163 docopy:
 164         /* Or copy compressed data which can be overlapped to per-CPU buffer */
 165         in = rq->in;
 166         src = erofs_get_pcpubuf(nrpages_in);
 167         if (!src) {
 168                 DBG_BUGON(1);
 169                 kunmap_atomic(inpage);
 170                 return ERR_PTR(-EFAULT);
 171         }
 172
 173         tmp = src;
 174         total = rq->inputsize;
 175         while (total) {
 176                 unsigned int page_copycnt =
 177                         min_t(unsigned int, total, PAGE_SIZE - *inputmargin);
 178
 179                 if (!inpage)
 180                         inpage = kmap_atomic(*in);
 181                 memcpy(tmp, inpage + *inputmargin, page_copycnt);
 182                 kunmap_atomic(inpage);
 183                 inpage = NULL;
 184                 tmp += page_copycnt;
 185                 total -= page_copycnt;
 186                 ++in;
 187                 *inputmargin = 0;
 188         }
 189         *maptype = 2;
 190         return src;
 191 }
 192
 193 static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 194 {
 195         unsigned int inputmargin;
 196         u8 *headpage, *src;
 197         bool support_0padding;
 198         int ret, maptype;
 199
 200         DBG_BUGON(*rq->in == NULL);
 201         headpage = kmap_atomic(*rq->in);
 202         inputmargin = 0;
 203         support_0padding = false;
 204
 205         /* decompression inplace is only safe when 0padding is enabled */
 206         if (erofs_sb_has_lz4_0padding(EROFS_SB(rq->sb))) {
 207                 support_0padding = true;
 208
 209                 while (!headpage[inputmargin & ~PAGE_MASK])
 210                         if (!(++inputmargin & ~PAGE_MASK))
 211                                 break;
 212
 213                 if (inputmargin >= rq->inputsize) {
 214                         kunmap_atomic(headpage);
 215                         return -EIO;
 216                 }
 217         }
 218
 219         rq->inputsize -= inputmargin;
 220         src = z_erofs_handle_inplace_io(rq, headpage, &inputmargin, &maptype,
 221                                         support_0padding);
 222         if (IS_ERR(src))
 223                 return PTR_ERR(src);
 224
 225         /* legacy format could compress extra data in a pcluster. */
 226         if (rq->partial_decoding || !support_0padding)
 227                 ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 228                                 rq->inputsize, rq->outputsize, rq->outputsize);
 229         else
 230                 ret = LZ4_decompress_safe(src + inputmargin, out,
 231                                           rq->inputsize, rq->outputsize);
 232
 233         if (ret != rq->outputsize) {
 234                 erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]",
 235                           ret, rq->inputsize, inputmargin, rq->outputsize);
 236
 237                 WARN_ON(1);
 238                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 239                                16, 1, src + inputmargin, rq->inputsize, true);
 240                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 241                                16, 1, out, rq->outputsize, true);
 242
 243                 if (ret >= 0)
 244                         memset(out + ret, 0, rq->outputsize - ret);
 245                 ret = -EIO;
 246         }
 247
 248         if (maptype == 0) {
 249                 kunmap_atomic(src);
 250         } else if (maptype == 1) {
 251                 vm_unmap_ram(src, PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT);
 252         } else if (maptype == 2) {
 253                 erofs_put_pcpubuf(src);
 254         } else {
 255                 DBG_BUGON(1);
 256                 return -EFAULT;
 257         }
 258         return ret;
 259 }
 260
 261 static struct z_erofs_decompressor decompressors[] = {
 262         [Z_EROFS_COMPRESSION_SHIFTED] = {
 263                 .name = "shifted"
 264         },
 265         [Z_EROFS_COMPRESSION_LZ4] = {
 266                 .prepare_destpages = z_erofs_lz4_prepare_destpages,
 267                 .decompress = z_erofs_lz4_decompress,
 268                 .name = "lz4"
 269         },
 270 };
 271
 272 static void copy_from_pcpubuf(struct page **out, const char *dst,
 273                               unsigned short pageofs_out,
 274                               unsigned int outputsize)
 275 {
 276         const char *end = dst + outputsize;
 277         const unsigned int righthalf = PAGE_SIZE - pageofs_out;
 278         const char *cur = dst - pageofs_out;
 279
 280         while (cur < end) {
 281                 struct page *const page = *out++;
 282
 283                 if (page) {
 284                         char *buf = kmap_atomic(page);
 285
 286                         if (cur >= dst) {
 287                                 memcpy(buf, cur, min_t(uint, PAGE_SIZE,
 288                                                        end - cur));
 289                         } else {
 290                                 memcpy(buf + pageofs_out, cur + pageofs_out,
 291                                        min_t(uint, righthalf, end - cur));
 292                         }
 293                         kunmap_atomic(buf);
 294                 }
 295                 cur += PAGE_SIZE;
 296         }
 297 }
 298
 299 static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
 300                                       struct list_head *pagepool)
 301 {
 302         const unsigned int nrpages_out =
 303                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 304         const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 305         unsigned int dst_maptype;
 306         void *dst;
 307         int ret;
 308
 309         /* two optimized fast paths only for non bigpcluster cases yet */
 310         if (rq->inputsize <= PAGE_SIZE) {
 311                 if (nrpages_out == 1 && !rq->inplace_io) {
 312                         DBG_BUGON(!*rq->out);
 313                         dst = kmap_atomic(*rq->out);
 314                         dst_maptype = 0;
 315                         goto dstmap_out;
 316                 }
 317
 318                 /*
 319                  * For the case of small output size (especially much less
 320                  * than PAGE_SIZE), memcpy the decompressed data rather than
 321                  * compressed data is preferred.
 322                  */
 323                 if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
 324                         dst = erofs_get_pcpubuf(1);
 325                         if (IS_ERR(dst))
 326                                 return PTR_ERR(dst);
 327
 328                         rq->inplace_io = false;
 329                         ret = alg->decompress(rq, dst);
 330                         if (!ret)
 331                                 copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
 332                                                   rq->outputsize);
 333
 334                         erofs_put_pcpubuf(dst);
 335                         return ret;
 336                 }
 337         }
 338
 339         /* general decoding path which can be used for all cases */
 340         ret = alg->prepare_destpages(rq, pagepool);
 341         if (ret < 0)
 342                 return ret;
 343         if (ret) {
 344                 dst = page_address(*rq->out);
 345                 dst_maptype = 1;
 346                 goto dstmap_out;
 347         }
 348
 349         dst = erofs_vm_map_ram(rq->out, nrpages_out);
 350         if (!dst)
 351                 return -ENOMEM;
 352         dst_maptype = 2;
 353
 354 dstmap_out:
 355         ret = alg->decompress(rq, dst + rq->pageofs_out);
 356
 357         if (!dst_maptype)
 358                 kunmap_atomic(dst);
 359         else if (dst_maptype == 2)
 360                 vm_unmap_ram(dst, nrpages_out);
 361         return ret;
 362 }
 363
 364 static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
 365                                      struct list_head *pagepool)
 366 {
 367         const unsigned int nrpages_out =
 368                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 369         const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
 370         unsigned char *src, *dst;
 371
 372         if (nrpages_out > 2) {
 373                 DBG_BUGON(1);
 374                 return -EIO;
 375         }
 376
 377         if (rq->out[0] == *rq->in) {
 378                 DBG_BUGON(nrpages_out != 1);
 379                 return 0;
 380         }
 381
 382         src = kmap_atomic(*rq->in);
 383         if (rq->out[0]) {
 384                 dst = kmap_atomic(rq->out[0]);
 385                 memcpy(dst + rq->pageofs_out, src, righthalf);
 386                 kunmap_atomic(dst);
 387         }
 388
 389         if (nrpages_out == 2) {
 390                 DBG_BUGON(!rq->out[1]);
 391                 if (rq->out[1] == *rq->in) {
 392                         memmove(src, src + righthalf, rq->pageofs_out);
 393                 } else {
 394                         dst = kmap_atomic(rq->out[1]);
 395                         memcpy(dst, src + righthalf, rq->pageofs_out);
 396                         kunmap_atomic(dst);
 397                 }
 398         }
 399         kunmap_atomic(src);
 400         return 0;
 401 }
 402
 403 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 404                        struct list_head *pagepool)
 405 {
 406         if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
 407                 return z_erofs_shifted_transform(rq, pagepool);
 408         return z_erofs_decompress_generic(rq, pagepool);
 409 }
 410