fs/btrfs/lzo.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2008 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/slab.h>
   8 #include <linux/mm.h>
   9 #include <linux/init.h>
  10 #include <linux/err.h>
  11 #include <linux/sched.h>
  12 #include <linux/pagemap.h>
  13 #include <linux/bio.h>
  14 #include <linux/lzo.h>
  15 #include <linux/refcount.h>
  16 #include "compression.h"
  17
  18 #define LZO_LEN 4
  19
  20 /*
  21  * Btrfs LZO compression format
  22  *
  23  * Regular and inlined LZO compressed data extents consist of:
  24  *
  25  * 1.  Header
  26  *     Fixed size. LZO_LEN (4) bytes long, LE32.
  27  *     Records the total size (including the header) of compressed data.
  28  *
  29  * 2.  Segment(s)
  30  *     Variable size. Each segment includes one segment header, followd by data
  31  *     payload.
  32  *     One regular LZO compressed extent can have one or more segments.
  33  *     For inlined LZO compressed extent, only one segment is allowed.
  34  *     One segment represents at most one page of uncompressed data.
  35  *
  36  * 2.1 Segment header
  37  *     Fixed size. LZO_LEN (4) bytes long, LE32.
  38  *     Records the total size of the segment (not including the header).
  39  *     Segment header never crosses page boundary, thus it's possible to
  40  *     have at most 3 padding zeros at the end of the page.
  41  *
  42  * 2.2 Data Payload
  43  *     Variable size. Size up limit should be lzo1x_worst_compress(PAGE_SIZE)
  44  *     which is 4419 for a 4KiB page.
  45  *
  46  * Example:
  47  * Page 1:
  48  *          0     0x2   0x4   0x6   0x8   0xa   0xc   0xe     0x10
  49  * 0x0000   |  Header   | SegHdr 01 | Data payload 01 ...     |
  50  * ...
  51  * 0x0ff0   | SegHdr  N | Data payload  N     ...          |00|
  52  *                                                          ^^ padding zeros
  53  * Page 2:
  54  * 0x1000   | SegHdr N+1| Data payload N+1 ...                |
  55  */
  56
  57 struct workspace {
  58         void *mem;
  59         void *buf;      /* where decompressed data goes */
  60         void *cbuf;     /* where compressed data goes */
  61         struct list_head list;
  62 };
  63
  64 static void lzo_free_workspace(struct list_head *ws)
  65 {
  66         struct workspace *workspace = list_entry(ws, struct workspace, list);
  67
  68         kvfree(workspace->buf);
  69         kvfree(workspace->cbuf);
  70         kvfree(workspace->mem);
  71         kfree(workspace);
  72 }
  73
  74 static struct list_head *lzo_alloc_workspace(void)
  75 {
  76         struct workspace *workspace;
  77
  78         workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);
  79         if (!workspace)
  80                 return ERR_PTR(-ENOMEM);
  81
  82         workspace->mem = kvmalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
  83         workspace->buf = kvmalloc(lzo1x_worst_compress(PAGE_SIZE), GFP_KERNEL);
  84         workspace->cbuf = kvmalloc(lzo1x_worst_compress(PAGE_SIZE), GFP_KERNEL);
  85         if (!workspace->mem || !workspace->buf || !workspace->cbuf)
  86                 goto fail;
  87
  88         INIT_LIST_HEAD(&workspace->list);
  89
  90         return &workspace->list;
  91 fail:
  92         lzo_free_workspace(&workspace->list);
  93         return ERR_PTR(-ENOMEM);
  94 }
  95
  96 static inline void write_compress_length(char *buf, size_t len)
  97 {
  98         __le32 dlen;
  99
 100         dlen = cpu_to_le32(len);
 101         memcpy(buf, &dlen, LZO_LEN);
 102 }
 103
 104 static inline size_t read_compress_length(const char *buf)
 105 {
 106         __le32 dlen;
 107
 108         memcpy(&dlen, buf, LZO_LEN);
 109         return le32_to_cpu(dlen);
 110 }
 111
 112 static int lzo_compress_pages(struct list_head *ws,
 113                               struct address_space *mapping,
 114                               u64 start,
 115                               struct page **pages,
 116                               unsigned long *out_pages,
 117                               unsigned long *total_in,
 118                               unsigned long *total_out)
 119 {
 120         struct workspace *workspace = list_entry(ws, struct workspace, list);
 121         int ret = 0;
 122         char *data_in;
 123         char *cpage_out;
 124         int nr_pages = 0;
 125         struct page *in_page = NULL;
 126         struct page *out_page = NULL;
 127         unsigned long bytes_left;
 128         unsigned long len = *total_out;
 129         unsigned long nr_dest_pages = *out_pages;
 130         const unsigned long max_out = nr_dest_pages * PAGE_SIZE;
 131         size_t in_len;
 132         size_t out_len;
 133         char *buf;
 134         unsigned long tot_in = 0;
 135         unsigned long tot_out = 0;
 136         unsigned long pg_bytes_left;
 137         unsigned long out_offset;
 138         unsigned long bytes;
 139
 140         *out_pages = 0;
 141         *total_out = 0;
 142         *total_in = 0;
 143
 144         in_page = find_get_page(mapping, start >> PAGE_SHIFT);
 145         data_in = kmap(in_page);
 146
 147         /*
 148          * store the size of all chunks of compressed data in
 149          * the first 4 bytes
 150          */
 151         out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
 152         if (out_page == NULL) {
 153                 ret = -ENOMEM;
 154                 goto out;
 155         }
 156         cpage_out = kmap(out_page);
 157         out_offset = LZO_LEN;
 158         tot_out = LZO_LEN;
 159         pages[0] = out_page;
 160         nr_pages = 1;
 161         pg_bytes_left = PAGE_SIZE - LZO_LEN;
 162
 163         /* compress at most one page of data each time */
 164         in_len = min(len, PAGE_SIZE);
 165         while (tot_in < len) {
 166                 ret = lzo1x_1_compress(data_in, in_len, workspace->cbuf,
 167                                        &out_len, workspace->mem);
 168                 if (ret != LZO_E_OK) {
 169                         pr_debug("BTRFS: lzo in loop returned %d\n",
 170                                ret);
 171                         ret = -EIO;
 172                         goto out;
 173                 }
 174
 175                 /* store the size of this chunk of compressed data */
 176                 write_compress_length(cpage_out + out_offset, out_len);
 177                 tot_out += LZO_LEN;
 178                 out_offset += LZO_LEN;
 179                 pg_bytes_left -= LZO_LEN;
 180
 181                 tot_in += in_len;
 182                 tot_out += out_len;
 183
 184                 /* copy bytes from the working buffer into the pages */
 185                 buf = workspace->cbuf;
 186                 while (out_len) {
 187                         bytes = min_t(unsigned long, pg_bytes_left, out_len);
 188
 189                         memcpy(cpage_out + out_offset, buf, bytes);
 190
 191                         out_len -= bytes;
 192                         pg_bytes_left -= bytes;
 193                         buf += bytes;
 194                         out_offset += bytes;
 195
 196                         /*
 197                          * we need another page for writing out.
 198                          *
 199                          * Note if there's less than 4 bytes left, we just
 200                          * skip to a new page.
 201                          */
 202                         if ((out_len == 0 && pg_bytes_left < LZO_LEN) ||
 203                             pg_bytes_left == 0) {
 204                                 if (pg_bytes_left) {
 205                                         memset(cpage_out + out_offset, 0,
 206                                                pg_bytes_left);
 207                                         tot_out += pg_bytes_left;
 208                                 }
 209
 210                                 /* we're done, don't allocate new page */
 211                                 if (out_len == 0 && tot_in >= len)
 212                                         break;
 213
 214                                 kunmap(out_page);
 215                                 if (nr_pages == nr_dest_pages) {
 216                                         out_page = NULL;
 217                                         ret = -E2BIG;
 218                                         goto out;
 219                                 }
 220
 221                                 out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
 222                                 if (out_page == NULL) {
 223                                         ret = -ENOMEM;
 224                                         goto out;
 225                                 }
 226                                 cpage_out = kmap(out_page);
 227                                 pages[nr_pages++] = out_page;
 228
 229                                 pg_bytes_left = PAGE_SIZE;
 230                                 out_offset = 0;
 231                         }
 232                 }
 233
 234                 /* we're making it bigger, give up */
 235                 if (tot_in > 8192 && tot_in < tot_out) {
 236                         ret = -E2BIG;
 237                         goto out;
 238                 }
 239
 240                 /* we're all done */
 241                 if (tot_in >= len)
 242                         break;
 243
 244                 if (tot_out > max_out)
 245                         break;
 246
 247                 bytes_left = len - tot_in;
 248                 kunmap(in_page);
 249                 put_page(in_page);
 250
 251                 start += PAGE_SIZE;
 252                 in_page = find_get_page(mapping, start >> PAGE_SHIFT);
 253                 data_in = kmap(in_page);
 254                 in_len = min(bytes_left, PAGE_SIZE);
 255         }
 256
 257         if (tot_out >= tot_in) {
 258                 ret = -E2BIG;
 259                 goto out;
 260         }
 261
 262         /* store the size of all chunks of compressed data */
 263         cpage_out = kmap(pages[0]);
 264         write_compress_length(cpage_out, tot_out);
 265
 266         kunmap(pages[0]);
 267
 268         ret = 0;
 269         *total_out = tot_out;
 270         *total_in = tot_in;
 271 out:
 272         *out_pages = nr_pages;
 273         if (out_page)
 274                 kunmap(out_page);
 275
 276         if (in_page) {
 277                 kunmap(in_page);
 278                 put_page(in_page);
 279         }
 280
 281         return ret;
 282 }
 283
 284 static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 285 {
 286         struct workspace *workspace = list_entry(ws, struct workspace, list);
 287         int ret = 0, ret2;
 288         char *data_in;
 289         unsigned long page_in_index = 0;
 290         size_t srclen = cb->compressed_len;
 291         unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
 292         unsigned long buf_start;
 293         unsigned long buf_offset = 0;
 294         unsigned long bytes;
 295         unsigned long working_bytes;
 296         size_t in_len;
 297         size_t out_len;
 298         const size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 299         unsigned long in_offset;
 300         unsigned long in_page_bytes_left;
 301         unsigned long tot_in;
 302         unsigned long tot_out;
 303         unsigned long tot_len;
 304         char *buf;
 305         bool may_late_unmap, need_unmap;
 306         struct page **pages_in = cb->compressed_pages;
 307         u64 disk_start = cb->start;
 308         struct bio *orig_bio = cb->orig_bio;
 309
 310         data_in = kmap(pages_in[0]);
 311         tot_len = read_compress_length(data_in);
 312         /*
 313          * Compressed data header check.
 314          *
 315          * The real compressed size can't exceed the maximum extent length, and
 316          * all pages should be used (whole unused page with just the segment
 317          * header is not possible).  If this happens it means the compressed
 318          * extent is corrupted.
 319          */
 320         if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
 321             tot_len < srclen - PAGE_SIZE) {
 322                 ret = -EUCLEAN;
 323                 goto done;
 324         }
 325
 326         tot_in = LZO_LEN;
 327         in_offset = LZO_LEN;
 328         in_page_bytes_left = PAGE_SIZE - LZO_LEN;
 329
 330         tot_out = 0;
 331
 332         while (tot_in < tot_len) {
 333                 in_len = read_compress_length(data_in + in_offset);
 334                 in_page_bytes_left -= LZO_LEN;
 335                 in_offset += LZO_LEN;
 336                 tot_in += LZO_LEN;
 337
 338                 /*
 339                  * Segment header check.
 340                  *
 341                  * The segment length must not exceed the maximum LZO
 342                  * compression size, nor the total compressed size.
 343                  */
 344                 if (in_len > max_segment_len || tot_in + in_len > tot_len) {
 345                         ret = -EUCLEAN;
 346                         goto done;
 347                 }
 348
 349                 tot_in += in_len;
 350                 working_bytes = in_len;
 351                 may_late_unmap = need_unmap = false;
 352
 353                 /* fast path: avoid using the working buffer */
 354                 if (in_page_bytes_left >= in_len) {
 355                         buf = data_in + in_offset;
 356                         bytes = in_len;
 357                         may_late_unmap = true;
 358                         goto cont;
 359                 }
 360
 361                 /* copy bytes from the pages into the working buffer */
 362                 buf = workspace->cbuf;
 363                 buf_offset = 0;
 364                 while (working_bytes) {
 365                         bytes = min(working_bytes, in_page_bytes_left);
 366
 367                         memcpy(buf + buf_offset, data_in + in_offset, bytes);
 368                         buf_offset += bytes;
 369 cont:
 370                         working_bytes -= bytes;
 371                         in_page_bytes_left -= bytes;
 372                         in_offset += bytes;
 373
 374                         /* check if we need to pick another page */
 375                         if ((working_bytes == 0 && in_page_bytes_left < LZO_LEN)
 376                             || in_page_bytes_left == 0) {
 377                                 tot_in += in_page_bytes_left;
 378
 379                                 if (working_bytes == 0 && tot_in >= tot_len)
 380                                         break;
 381
 382                                 if (page_in_index + 1 >= total_pages_in) {
 383                                         ret = -EIO;
 384                                         goto done;
 385                                 }
 386
 387                                 if (may_late_unmap)
 388                                         need_unmap = true;
 389                                 else
 390                                         kunmap(pages_in[page_in_index]);
 391
 392                                 data_in = kmap(pages_in[++page_in_index]);
 393
 394                                 in_page_bytes_left = PAGE_SIZE;
 395                                 in_offset = 0;
 396                         }
 397                 }
 398
 399                 out_len = max_segment_len;
 400                 ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
 401                                             &out_len);
 402                 if (need_unmap)
 403                         kunmap(pages_in[page_in_index - 1]);
 404                 if (ret != LZO_E_OK) {
 405                         pr_warn("BTRFS: decompress failed\n");
 406                         ret = -EIO;
 407                         break;
 408                 }
 409
 410                 buf_start = tot_out;
 411                 tot_out += out_len;
 412
 413                 ret2 = btrfs_decompress_buf2page(workspace->buf, buf_start,
 414                                                  tot_out, disk_start, orig_bio);
 415                 if (ret2 == 0)
 416                         break;
 417         }
 418 done:
 419         kunmap(pages_in[page_in_index]);
 420         if (!ret)
 421                 zero_fill_bio(orig_bio);
 422         return ret;
 423 }
 424
 425 static int lzo_decompress(struct list_head *ws, unsigned char *data_in,
 426                           struct page *dest_page,
 427                           unsigned long start_byte,
 428                           size_t srclen, size_t destlen)
 429 {
 430         struct workspace *workspace = list_entry(ws, struct workspace, list);
 431         size_t in_len;
 432         size_t out_len;
 433         size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
 434         int ret = 0;
 435         char *kaddr;
 436         unsigned long bytes;
 437
 438         if (srclen < LZO_LEN || srclen > max_segment_len + LZO_LEN * 2)
 439                 return -EUCLEAN;
 440
 441         in_len = read_compress_length(data_in);
 442         if (in_len != srclen)
 443                 return -EUCLEAN;
 444         data_in += LZO_LEN;
 445
 446         in_len = read_compress_length(data_in);
 447         if (in_len != srclen - LZO_LEN * 2) {
 448                 ret = -EUCLEAN;
 449                 goto out;
 450         }
 451         data_in += LZO_LEN;
 452
 453         out_len = PAGE_SIZE;
 454         ret = lzo1x_decompress_safe(data_in, in_len, workspace->buf, &out_len);
 455         if (ret != LZO_E_OK) {
 456                 pr_warn("BTRFS: decompress failed!\n");
 457                 ret = -EIO;
 458                 goto out;
 459         }
 460
 461         if (out_len < start_byte) {
 462                 ret = -EIO;
 463                 goto out;
 464         }
 465
 466         /*
 467          * the caller is already checking against PAGE_SIZE, but lets
 468          * move this check closer to the memcpy/memset
 469          */
 470         destlen = min_t(unsigned long, destlen, PAGE_SIZE);
 471         bytes = min_t(unsigned long, destlen, out_len - start_byte);
 472
 473         kaddr = kmap_atomic(dest_page);
 474         memcpy(kaddr, workspace->buf + start_byte, bytes);
 475
 476         /*
 477          * btrfs_getblock is doing a zero on the tail of the page too,
 478          * but this will cover anything missing from the decompressed
 479          * data.
 480          */
 481         if (bytes < destlen)
 482                 memset(kaddr+bytes, 0, destlen-bytes);
 483         kunmap_atomic(kaddr);
 484 out:
 485         return ret;
 486 }
 487
 488 static void lzo_set_level(struct list_head *ws, unsigned int type)
 489 {
 490 }
 491
 492 const struct btrfs_compress_op btrfs_lzo_compress = {
 493         .alloc_workspace        = lzo_alloc_workspace,
 494         .free_workspace         = lzo_free_workspace,
 495         .compress_pages         = lzo_compress_pages,
 496         .decompress_bio         = lzo_decompress_bio,
 497         .decompress             = lzo_decompress,
 498         .set_level              = lzo_set_level,
 499 };