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_lz4_decompress_ctx {
  20         struct z_erofs_decompress_req *rq;
  21         /* # of encoded, decoded pages */
  22         unsigned int inpages, outpages;
  23         /* decoded block total length (used for in-place decompression) */
  24         unsigned int oend;
  25 };
  26
  27 int z_erofs_load_lz4_config(struct super_block *sb,
  28                             struct erofs_super_block *dsb,
  29                             struct z_erofs_lz4_cfgs *lz4, int size)
  30 {
  31         struct erofs_sb_info *sbi = EROFS_SB(sb);
  32         u16 distance;
  33
  34         if (lz4) {
  35                 if (size < sizeof(struct z_erofs_lz4_cfgs)) {
  36                         erofs_err(sb, "invalid lz4 cfgs, size=%u", size);
  37                         return -EINVAL;
  38                 }
  39                 distance = le16_to_cpu(lz4->max_distance);
  40
  41                 sbi->lz4.max_pclusterblks = le16_to_cpu(lz4->max_pclusterblks);
  42                 if (!sbi->lz4.max_pclusterblks) {
  43                         sbi->lz4.max_pclusterblks = 1;  /* reserved case */
  44                 } else if (sbi->lz4.max_pclusterblks >
  45                            Z_EROFS_PCLUSTER_MAX_SIZE / EROFS_BLKSIZ) {
  46                         erofs_err(sb, "too large lz4 pclusterblks %u",
  47                                   sbi->lz4.max_pclusterblks);
  48                         return -EINVAL;
  49                 } else if (sbi->lz4.max_pclusterblks >= 2) {
  50                         erofs_info(sb, "EXPERIMENTAL big pcluster feature in use. Use at your own risk!");
  51                 }
  52         } else {
  53                 distance = le16_to_cpu(dsb->u1.lz4_max_distance);
  54                 sbi->lz4.max_pclusterblks = 1;
  55         }
  56
  57         sbi->lz4.max_distance_pages = distance ?
  58                                         DIV_ROUND_UP(distance, PAGE_SIZE) + 1 :
  59                                         LZ4_MAX_DISTANCE_PAGES;
  60         return erofs_pcpubuf_growsize(sbi->lz4.max_pclusterblks);
  61 }
  62
  63 /*
  64  * Fill all gaps with bounce pages if it's a sparse page list. Also check if
  65  * all physical pages are consecutive, which can be seen for moderate CR.
  66  */
  67 static int z_erofs_lz4_prepare_dstpages(struct z_erofs_lz4_decompress_ctx *ctx,
  68                                         struct page **pagepool)
  69 {
  70         struct z_erofs_decompress_req *rq = ctx->rq;
  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 < ctx->outpages; ++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_lz4_handle_overlap(struct z_erofs_lz4_decompress_ctx *ctx,
 123                         void *inpage, unsigned int *inputmargin, int *maptype,
 124                         bool may_inplace)
 125 {
 126         struct z_erofs_decompress_req *rq = ctx->rq;
 127         unsigned int omargin, total, i, j;
 128         struct page **in;
 129         void *src, *tmp;
 130
 131         if (rq->inplace_io) {
 132                 omargin = PAGE_ALIGN(ctx->oend) - ctx->oend;
 133                 if (rq->partial_decoding || !may_inplace ||
 134                     omargin < LZ4_DECOMPRESS_INPLACE_MARGIN(rq->inputsize))
 135                         goto docopy;
 136
 137                 for (i = 0; i < ctx->inpages; ++i) {
 138                         DBG_BUGON(rq->in[i] == NULL);
 139                         for (j = 0; j < ctx->outpages - ctx->inpages + i; ++j)
 140                                 if (rq->out[j] == rq->in[i])
 141                                         goto docopy;
 142                 }
 143         }
 144
 145         if (ctx->inpages <= 1) {
 146                 *maptype = 0;
 147                 return inpage;
 148         }
 149         kunmap_atomic(inpage);
 150         might_sleep();
 151         src = erofs_vm_map_ram(rq->in, ctx->inpages);
 152         if (!src)
 153                 return ERR_PTR(-ENOMEM);
 154         *maptype = 1;
 155         return src;
 156
 157 docopy:
 158         /* Or copy compressed data which can be overlapped to per-CPU buffer */
 159         in = rq->in;
 160         src = erofs_get_pcpubuf(ctx->inpages);
 161         if (!src) {
 162                 DBG_BUGON(1);
 163                 kunmap_atomic(inpage);
 164                 return ERR_PTR(-EFAULT);
 165         }
 166
 167         tmp = src;
 168         total = rq->inputsize;
 169         while (total) {
 170                 unsigned int page_copycnt =
 171                         min_t(unsigned int, total, PAGE_SIZE - *inputmargin);
 172
 173                 if (!inpage)
 174                         inpage = kmap_atomic(*in);
 175                 memcpy(tmp, inpage + *inputmargin, page_copycnt);
 176                 kunmap_atomic(inpage);
 177                 inpage = NULL;
 178                 tmp += page_copycnt;
 179                 total -= page_copycnt;
 180                 ++in;
 181                 *inputmargin = 0;
 182         }
 183         *maptype = 2;
 184         return src;
 185 }
 186
 187 /*
 188  * Get the exact inputsize with zero_padding feature.
 189  *  - For LZ4, it should work if zero_padding feature is on (5.3+);
 190  *  - For MicroLZMA, it'd be enabled all the time.
 191  */
 192 int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
 193                          unsigned int padbufsize)
 194 {
 195         const char *padend;
 196
 197         padend = memchr_inv(padbuf, 0, padbufsize);
 198         if (!padend)
 199                 return -EFSCORRUPTED;
 200         rq->inputsize -= padend - padbuf;
 201         rq->pageofs_in += padend - padbuf;
 202         return 0;
 203 }
 204
 205 static int z_erofs_lz4_decompress_mem(struct z_erofs_lz4_decompress_ctx *ctx,
 206                                       u8 *out)
 207 {
 208         struct z_erofs_decompress_req *rq = ctx->rq;
 209         bool support_0padding = false, may_inplace = false;
 210         unsigned int inputmargin;
 211         u8 *headpage, *src;
 212         int ret, maptype;
 213
 214         DBG_BUGON(*rq->in == NULL);
 215         headpage = kmap_atomic(*rq->in);
 216
 217         /* LZ4 decompression inplace is only safe if zero_padding is enabled */
 218         if (erofs_sb_has_zero_padding(EROFS_SB(rq->sb))) {
 219                 support_0padding = true;
 220                 ret = z_erofs_fixup_insize(rq, headpage + rq->pageofs_in,
 221                                 min_t(unsigned int, rq->inputsize,
 222                                       EROFS_BLKSIZ - rq->pageofs_in));
 223                 if (ret) {
 224                         kunmap_atomic(headpage);
 225                         return ret;
 226                 }
 227                 may_inplace = !((rq->pageofs_in + rq->inputsize) &
 228                                 (EROFS_BLKSIZ - 1));
 229         }
 230
 231         inputmargin = rq->pageofs_in;
 232         src = z_erofs_lz4_handle_overlap(ctx, headpage, &inputmargin,
 233                                          &maptype, may_inplace);
 234         if (IS_ERR(src))
 235                 return PTR_ERR(src);
 236
 237         /* legacy format could compress extra data in a pcluster. */
 238         if (rq->partial_decoding || !support_0padding)
 239                 ret = LZ4_decompress_safe_partial(src + inputmargin, out,
 240                                 rq->inputsize, rq->outputsize, rq->outputsize);
 241         else
 242                 ret = LZ4_decompress_safe(src + inputmargin, out,
 243                                           rq->inputsize, rq->outputsize);
 244
 245         if (ret != rq->outputsize) {
 246                 erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]",
 247                           ret, rq->inputsize, inputmargin, rq->outputsize);
 248
 249                 print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 250                                16, 1, src + inputmargin, rq->inputsize, true);
 251                 print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
 252                                16, 1, out, rq->outputsize, true);
 253
 254                 if (ret >= 0)
 255                         memset(out + ret, 0, rq->outputsize - ret);
 256                 ret = -EIO;
 257         } else {
 258                 ret = 0;
 259         }
 260
 261         if (maptype == 0) {
 262                 kunmap_atomic(headpage);
 263         } else if (maptype == 1) {
 264                 vm_unmap_ram(src, ctx->inpages);
 265         } else if (maptype == 2) {
 266                 erofs_put_pcpubuf(src);
 267         } else {
 268                 DBG_BUGON(1);
 269                 return -EFAULT;
 270         }
 271         return ret;
 272 }
 273
 274 static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq,
 275                                   struct page **pagepool)
 276 {
 277         struct z_erofs_lz4_decompress_ctx ctx;
 278         unsigned int dst_maptype;
 279         void *dst;
 280         int ret;
 281
 282         ctx.rq = rq;
 283         ctx.oend = rq->pageofs_out + rq->outputsize;
 284         ctx.outpages = PAGE_ALIGN(ctx.oend) >> PAGE_SHIFT;
 285         ctx.inpages = PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT;
 286
 287         /* one optimized fast path only for non bigpcluster cases yet */
 288         if (ctx.inpages == 1 && ctx.outpages == 1 && !rq->inplace_io) {
 289                 DBG_BUGON(!*rq->out);
 290                 dst = kmap_atomic(*rq->out);
 291                 dst_maptype = 0;
 292                 goto dstmap_out;
 293         }
 294
 295         /* general decoding path which can be used for all cases */
 296         ret = z_erofs_lz4_prepare_dstpages(&ctx, pagepool);
 297         if (ret < 0) {
 298                 return ret;
 299         } else if (ret > 0) {
 300                 dst = page_address(*rq->out);
 301                 dst_maptype = 1;
 302         } else {
 303                 dst = erofs_vm_map_ram(rq->out, ctx.outpages);
 304                 if (!dst)
 305                         return -ENOMEM;
 306                 dst_maptype = 2;
 307         }
 308
 309 dstmap_out:
 310         ret = z_erofs_lz4_decompress_mem(&ctx, dst + rq->pageofs_out);
 311         if (!dst_maptype)
 312                 kunmap_atomic(dst);
 313         else if (dst_maptype == 2)
 314                 vm_unmap_ram(dst, ctx.outpages);
 315         return ret;
 316 }
 317
 318 static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
 319                                      struct page **pagepool)
 320 {
 321         const unsigned int nrpages_out =
 322                 PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 323         const unsigned int righthalf = min_t(unsigned int, rq->outputsize,
 324                                              PAGE_SIZE - rq->pageofs_out);
 325         unsigned char *src, *dst;
 326
 327         if (nrpages_out > 2) {
 328                 DBG_BUGON(1);
 329                 return -EIO;
 330         }
 331
 332         if (rq->out[0] == *rq->in) {
 333                 DBG_BUGON(nrpages_out != 1);
 334                 return 0;
 335         }
 336
 337         src = kmap_atomic(*rq->in) + rq->pageofs_in;
 338         if (rq->out[0]) {
 339                 dst = kmap_atomic(rq->out[0]);
 340                 memcpy(dst + rq->pageofs_out, src, righthalf);
 341                 kunmap_atomic(dst);
 342         }
 343
 344         if (nrpages_out == 2) {
 345                 DBG_BUGON(!rq->out[1]);
 346                 if (rq->out[1] == *rq->in) {
 347                         memmove(src, src + righthalf, rq->pageofs_out);
 348                 } else {
 349                         dst = kmap_atomic(rq->out[1]);
 350                         memcpy(dst, src + righthalf, rq->pageofs_out);
 351                         kunmap_atomic(dst);
 352                 }
 353         }
 354         kunmap_atomic(src);
 355         return 0;
 356 }
 357
 358 static struct z_erofs_decompressor decompressors[] = {
 359         [Z_EROFS_COMPRESSION_SHIFTED] = {
 360                 .decompress = z_erofs_shifted_transform,
 361                 .name = "shifted"
 362         },
 363         [Z_EROFS_COMPRESSION_LZ4] = {
 364                 .decompress = z_erofs_lz4_decompress,
 365                 .name = "lz4"
 366         },
 367 #ifdef CONFIG_EROFS_FS_ZIP_LZMA
 368         [Z_EROFS_COMPRESSION_LZMA] = {
 369                 .decompress = z_erofs_lzma_decompress,
 370                 .name = "lzma"
 371         },
 372 #endif
 373 };
 374
 375 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
 376                        struct page **pagepool)
 377 {
 378         return decompressors[rq->alg].decompress(rq, pagepool);
 379 }