fs/btrfs/compression.c

   1 /*
   2  * Copyright (C) 2008 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/bio.h>
  21 #include <linux/buffer_head.h>
  22 #include <linux/file.h>
  23 #include <linux/fs.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/highmem.h>
  26 #include <linux/time.h>
  27 #include <linux/init.h>
  28 #include <linux/string.h>
  29 #include <linux/backing-dev.h>
  30 #include <linux/mpage.h>
  31 #include <linux/swap.h>
  32 #include <linux/writeback.h>
  33 #include <linux/bit_spinlock.h>
  34 #include <linux/slab.h>
  35 #include "ctree.h"
  36 #include "disk-io.h"
  37 #include "transaction.h"
  38 #include "btrfs_inode.h"
  39 #include "volumes.h"
  40 #include "ordered-data.h"
  41 #include "compression.h"
  42 #include "extent_io.h"
  43 #include "extent_map.h"
  44
  45 struct compressed_bio {
  46         /* number of bios pending for this compressed extent */
  47         atomic_t pending_bios;
  48
  49         /* the pages with the compressed data on them */
  50         struct page **compressed_pages;
  51
  52         /* inode that owns this data */
  53         struct inode *inode;
  54
  55         /* starting offset in the inode for our pages */
  56         u64 start;
  57
  58         /* number of bytes in the inode we're working on */
  59         unsigned long len;
  60
  61         /* number of bytes on disk */
  62         unsigned long compressed_len;
  63
  64         /* the compression algorithm for this bio */
  65         int compress_type;
  66
  67         /* number of compressed pages in the array */
  68         unsigned long nr_pages;
  69
  70         /* IO errors */
  71         int errors;
  72         int mirror_num;
  73
  74         /* for reads, this is the bio we are copying the data into */
  75         struct bio *orig_bio;
  76
  77         /*
  78          * the start of a variable length array of checksums only
  79          * used by reads
  80          */
  81         u32 sums;
  82 };
  83
  84 static int btrfs_decompress_bio(int type, struct page **pages_in,
  85                                    u64 disk_start, struct bio *orig_bio,
  86                                    size_t srclen);
  87
  88 static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
  89                                       unsigned long disk_size)
  90 {
  91         u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
  92
  93         return sizeof(struct compressed_bio) +
  94                 (DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size;
  95 }
  96
  97 static struct bio *compressed_bio_alloc(struct block_device *bdev,
  98                                         u64 first_byte, gfp_t gfp_flags)
  99 {
 100         return btrfs_bio_alloc(bdev, first_byte >> 9, BIO_MAX_PAGES, gfp_flags);
 101 }
 102
 103 static int check_compressed_csum(struct inode *inode,
 104                                  struct compressed_bio *cb,
 105                                  u64 disk_start)
 106 {
 107         int ret;
 108         struct page *page;
 109         unsigned long i;
 110         char *kaddr;
 111         u32 csum;
 112         u32 *cb_sum = &cb->sums;
 113
 114         if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
 115                 return 0;
 116
 117         for (i = 0; i < cb->nr_pages; i++) {
 118                 page = cb->compressed_pages[i];
 119                 csum = ~(u32)0;
 120
 121                 kaddr = kmap_atomic(page);
 122                 csum = btrfs_csum_data(kaddr, csum, PAGE_SIZE);
 123                 btrfs_csum_final(csum, (u8 *)&csum);
 124                 kunmap_atomic(kaddr);
 125
 126                 if (csum != *cb_sum) {
 127                         btrfs_info(BTRFS_I(inode)->root->fs_info,
 128                            "csum failed ino %llu extent %llu csum %u wanted %u mirror %d",
 129                            btrfs_ino(inode), disk_start, csum, *cb_sum,
 130                            cb->mirror_num);
 131                         ret = -EIO;
 132                         goto fail;
 133                 }
 134                 cb_sum++;
 135
 136         }
 137         ret = 0;
 138 fail:
 139         return ret;
 140 }
 141
 142 /* when we finish reading compressed pages from the disk, we
 143  * decompress them and then run the bio end_io routines on the
 144  * decompressed pages (in the inode address space).
 145  *
 146  * This allows the checksumming and other IO error handling routines
 147  * to work normally
 148  *
 149  * The compressed pages are freed here, and it must be run
 150  * in process context
 151  */
 152 static void end_compressed_bio_read(struct bio *bio)
 153 {
 154         struct compressed_bio *cb = bio->bi_private;
 155         struct inode *inode;
 156         struct page *page;
 157         unsigned long index;
 158         int ret;
 159
 160         if (bio->bi_error)
 161                 cb->errors = 1;
 162
 163         /* if there are more bios still pending for this compressed
 164          * extent, just exit
 165          */
 166         if (!atomic_dec_and_test(&cb->pending_bios))
 167                 goto out;
 168
 169         inode = cb->inode;
 170         ret = check_compressed_csum(inode, cb,
 171                                     (u64)bio->bi_iter.bi_sector << 9);
 172         if (ret)
 173                 goto csum_failed;
 174
 175         /* ok, we're the last bio for this extent, lets start
 176          * the decompression.
 177          */
 178         ret = btrfs_decompress_bio(cb->compress_type,
 179                                       cb->compressed_pages,
 180                                       cb->start,
 181                                       cb->orig_bio,
 182                                       cb->compressed_len);
 183 csum_failed:
 184         if (ret)
 185                 cb->errors = 1;
 186
 187         /* release the compressed pages */
 188         index = 0;
 189         for (index = 0; index < cb->nr_pages; index++) {
 190                 page = cb->compressed_pages[index];
 191                 page->mapping = NULL;
 192                 put_page(page);
 193         }
 194
 195         /* do io completion on the original bio */
 196         if (cb->errors) {
 197                 bio_io_error(cb->orig_bio);
 198         } else {
 199                 int i;
 200                 struct bio_vec *bvec;
 201
 202                 /*
 203                  * we have verified the checksum already, set page
 204                  * checked so the end_io handlers know about it
 205                  */
 206                 bio_for_each_segment_all(bvec, cb->orig_bio, i)
 207                         SetPageChecked(bvec->bv_page);
 208
 209                 bio_endio(cb->orig_bio);
 210         }
 211
 212         /* finally free the cb struct */
 213         kfree(cb->compressed_pages);
 214         kfree(cb);
 215 out:
 216         bio_put(bio);
 217 }
 218
 219 /*
 220  * Clear the writeback bits on all of the file
 221  * pages for a compressed write
 222  */
 223 static noinline void end_compressed_writeback(struct inode *inode,
 224                                               const struct compressed_bio *cb)
 225 {
 226         unsigned long index = cb->start >> PAGE_SHIFT;
 227         unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
 228         struct page *pages[16];
 229         unsigned long nr_pages = end_index - index + 1;
 230         int i;
 231         int ret;
 232
 233         if (cb->errors)
 234                 mapping_set_error(inode->i_mapping, -EIO);
 235
 236         while (nr_pages > 0) {
 237                 ret = find_get_pages_contig(inode->i_mapping, index,
 238                                      min_t(unsigned long,
 239                                      nr_pages, ARRAY_SIZE(pages)), pages);
 240                 if (ret == 0) {
 241                         nr_pages -= 1;
 242                         index += 1;
 243                         continue;
 244                 }
 245                 for (i = 0; i < ret; i++) {
 246                         if (cb->errors)
 247                                 SetPageError(pages[i]);
 248                         end_page_writeback(pages[i]);
 249                         put_page(pages[i]);
 250                 }
 251                 nr_pages -= ret;
 252                 index += ret;
 253         }
 254         /* the inode may be gone now */
 255 }
 256
 257 /*
 258  * do the cleanup once all the compressed pages hit the disk.
 259  * This will clear writeback on the file pages and free the compressed
 260  * pages.
 261  *
 262  * This also calls the writeback end hooks for the file pages so that
 263  * metadata and checksums can be updated in the file.
 264  */
 265 static void end_compressed_bio_write(struct bio *bio)
 266 {
 267         struct extent_io_tree *tree;
 268         struct compressed_bio *cb = bio->bi_private;
 269         struct inode *inode;
 270         struct page *page;
 271         unsigned long index;
 272
 273         if (bio->bi_error)
 274                 cb->errors = 1;
 275
 276         /* if there are more bios still pending for this compressed
 277          * extent, just exit
 278          */
 279         if (!atomic_dec_and_test(&cb->pending_bios))
 280                 goto out;
 281
 282         /* ok, we're the last bio for this extent, step one is to
 283          * call back into the FS and do all the end_io operations
 284          */
 285         inode = cb->inode;
 286         tree = &BTRFS_I(inode)->io_tree;
 287         cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
 288         tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
 289                                          cb->start,
 290                                          cb->start + cb->len - 1,
 291                                          NULL,
 292                                          bio->bi_error ? 0 : 1);
 293         cb->compressed_pages[0]->mapping = NULL;
 294
 295         end_compressed_writeback(inode, cb);
 296         /* note, our inode could be gone now */
 297
 298         /*
 299          * release the compressed pages, these came from alloc_page and
 300          * are not attached to the inode at all
 301          */
 302         index = 0;
 303         for (index = 0; index < cb->nr_pages; index++) {
 304                 page = cb->compressed_pages[index];
 305                 page->mapping = NULL;
 306                 put_page(page);
 307         }
 308
 309         /* finally free the cb struct */
 310         kfree(cb->compressed_pages);
 311         kfree(cb);
 312 out:
 313         bio_put(bio);
 314 }
 315
 316 /*
 317  * worker function to build and submit bios for previously compressed pages.
 318  * The corresponding pages in the inode should be marked for writeback
 319  * and the compressed pages should have a reference on them for dropping
 320  * when the IO is complete.
 321  *
 322  * This also checksums the file bytes and gets things ready for
 323  * the end io hooks.
 324  */
 325 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
 326                                  unsigned long len, u64 disk_start,
 327                                  unsigned long compressed_len,
 328                                  struct page **compressed_pages,
 329                                  unsigned long nr_pages)
 330 {
 331         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 332         struct bio *bio = NULL;
 333         struct compressed_bio *cb;
 334         unsigned long bytes_left;
 335         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 336         int pg_index = 0;
 337         struct page *page;
 338         u64 first_byte = disk_start;
 339         struct block_device *bdev;
 340         int ret;
 341         int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
 342
 343         WARN_ON(start & ((u64)PAGE_SIZE - 1));
 344         cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
 345         if (!cb)
 346                 return -ENOMEM;
 347         atomic_set(&cb->pending_bios, 0);
 348         cb->errors = 0;
 349         cb->inode = inode;
 350         cb->start = start;
 351         cb->len = len;
 352         cb->mirror_num = 0;
 353         cb->compressed_pages = compressed_pages;
 354         cb->compressed_len = compressed_len;
 355         cb->orig_bio = NULL;
 356         cb->nr_pages = nr_pages;
 357
 358         bdev = fs_info->fs_devices->latest_bdev;
 359
 360         bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
 361         if (!bio) {
 362                 kfree(cb);
 363                 return -ENOMEM;
 364         }
 365         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 366         bio->bi_private = cb;
 367         bio->bi_end_io = end_compressed_bio_write;
 368         atomic_inc(&cb->pending_bios);
 369
 370         /* create and submit bios for the compressed pages */
 371         bytes_left = compressed_len;
 372         for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
 373                 page = compressed_pages[pg_index];
 374                 page->mapping = inode->i_mapping;
 375                 if (bio->bi_iter.bi_size)
 376                         ret = io_tree->ops->merge_bio_hook(page, 0,
 377                                                            PAGE_SIZE,
 378                                                            bio, 0);
 379                 else
 380                         ret = 0;
 381
 382                 page->mapping = NULL;
 383                 if (ret || bio_add_page(bio, page, PAGE_SIZE, 0) <
 384                     PAGE_SIZE) {
 385                         bio_get(bio);
 386
 387                         /*
 388                          * inc the count before we submit the bio so
 389                          * we know the end IO handler won't happen before
 390                          * we inc the count.  Otherwise, the cb might get
 391                          * freed before we're done setting it up
 392                          */
 393                         atomic_inc(&cb->pending_bios);
 394                         ret = btrfs_bio_wq_end_io(fs_info, bio,
 395                                                   BTRFS_WQ_ENDIO_DATA);
 396                         BUG_ON(ret); /* -ENOMEM */
 397
 398                         if (!skip_sum) {
 399                                 ret = btrfs_csum_one_bio(inode, bio, start, 1);
 400                                 BUG_ON(ret); /* -ENOMEM */
 401                         }
 402
 403                         ret = btrfs_map_bio(fs_info, bio, 0, 1);
 404                         if (ret) {
 405                                 bio->bi_error = ret;
 406                                 bio_endio(bio);
 407                         }
 408
 409                         bio_put(bio);
 410
 411                         bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
 412                         BUG_ON(!bio);
 413                         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 414                         bio->bi_private = cb;
 415                         bio->bi_end_io = end_compressed_bio_write;
 416                         bio_add_page(bio, page, PAGE_SIZE, 0);
 417                 }
 418                 if (bytes_left < PAGE_SIZE) {
 419                         btrfs_info(fs_info,
 420                                         "bytes left %lu compress len %lu nr %lu",
 421                                bytes_left, cb->compressed_len, cb->nr_pages);
 422                 }
 423                 bytes_left -= PAGE_SIZE;
 424                 first_byte += PAGE_SIZE;
 425                 cond_resched();
 426         }
 427         bio_get(bio);
 428
 429         ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
 430         BUG_ON(ret); /* -ENOMEM */
 431
 432         if (!skip_sum) {
 433                 ret = btrfs_csum_one_bio(inode, bio, start, 1);
 434                 BUG_ON(ret); /* -ENOMEM */
 435         }
 436
 437         ret = btrfs_map_bio(fs_info, bio, 0, 1);
 438         if (ret) {
 439                 bio->bi_error = ret;
 440                 bio_endio(bio);
 441         }
 442
 443         bio_put(bio);
 444         return 0;
 445 }
 446
 447 static u64 bio_end_offset(struct bio *bio)
 448 {
 449         struct bio_vec *last = &bio->bi_io_vec[bio->bi_vcnt - 1];
 450
 451         return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
 452 }
 453
 454 static noinline int add_ra_bio_pages(struct inode *inode,
 455                                      u64 compressed_end,
 456                                      struct compressed_bio *cb)
 457 {
 458         unsigned long end_index;
 459         unsigned long pg_index;
 460         u64 last_offset;
 461         u64 isize = i_size_read(inode);
 462         int ret;
 463         struct page *page;
 464         unsigned long nr_pages = 0;
 465         struct extent_map *em;
 466         struct address_space *mapping = inode->i_mapping;
 467         struct extent_map_tree *em_tree;
 468         struct extent_io_tree *tree;
 469         u64 end;
 470         int misses = 0;
 471
 472         last_offset = bio_end_offset(cb->orig_bio);
 473         em_tree = &BTRFS_I(inode)->extent_tree;
 474         tree = &BTRFS_I(inode)->io_tree;
 475
 476         if (isize == 0)
 477                 return 0;
 478
 479         end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
 480
 481         while (last_offset < compressed_end) {
 482                 pg_index = last_offset >> PAGE_SHIFT;
 483
 484                 if (pg_index > end_index)
 485                         break;
 486
 487                 rcu_read_lock();
 488                 page = radix_tree_lookup(&mapping->page_tree, pg_index);
 489                 rcu_read_unlock();
 490                 if (page && !radix_tree_exceptional_entry(page)) {
 491                         misses++;
 492                         if (misses > 4)
 493                                 break;
 494                         goto next;
 495                 }
 496
 497                 page = __page_cache_alloc(mapping_gfp_constraint(mapping,
 498                                                                  ~__GFP_FS));
 499                 if (!page)
 500                         break;
 501
 502                 if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
 503                         put_page(page);
 504                         goto next;
 505                 }
 506
 507                 end = last_offset + PAGE_SIZE - 1;
 508                 /*
 509                  * at this point, we have a locked page in the page cache
 510                  * for these bytes in the file.  But, we have to make
 511                  * sure they map to this compressed extent on disk.
 512                  */
 513                 set_page_extent_mapped(page);
 514                 lock_extent(tree, last_offset, end);
 515                 read_lock(&em_tree->lock);
 516                 em = lookup_extent_mapping(em_tree, last_offset,
 517                                            PAGE_SIZE);
 518                 read_unlock(&em_tree->lock);
 519
 520                 if (!em || last_offset < em->start ||
 521                     (last_offset + PAGE_SIZE > extent_map_end(em)) ||
 522                     (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
 523                         free_extent_map(em);
 524                         unlock_extent(tree, last_offset, end);
 525                         unlock_page(page);
 526                         put_page(page);
 527                         break;
 528                 }
 529                 free_extent_map(em);
 530
 531                 if (page->index == end_index) {
 532                         char *userpage;
 533                         size_t zero_offset = isize & (PAGE_SIZE - 1);
 534
 535                         if (zero_offset) {
 536                                 int zeros;
 537                                 zeros = PAGE_SIZE - zero_offset;
 538                                 userpage = kmap_atomic(page);
 539                                 memset(userpage + zero_offset, 0, zeros);
 540                                 flush_dcache_page(page);
 541                                 kunmap_atomic(userpage);
 542                         }
 543                 }
 544
 545                 ret = bio_add_page(cb->orig_bio, page,
 546                                    PAGE_SIZE, 0);
 547
 548                 if (ret == PAGE_SIZE) {
 549                         nr_pages++;
 550                         put_page(page);
 551                 } else {
 552                         unlock_extent(tree, last_offset, end);
 553                         unlock_page(page);
 554                         put_page(page);
 555                         break;
 556                 }
 557 next:
 558                 last_offset += PAGE_SIZE;
 559         }
 560         return 0;
 561 }
 562
 563 /*
 564  * for a compressed read, the bio we get passed has all the inode pages
 565  * in it.  We don't actually do IO on those pages but allocate new ones
 566  * to hold the compressed pages on disk.
 567  *
 568  * bio->bi_iter.bi_sector points to the compressed extent on disk
 569  * bio->bi_io_vec points to all of the inode pages
 570  *
 571  * After the compressed pages are read, we copy the bytes into the
 572  * bio we were passed and then call the bio end_io calls
 573  */
 574 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 575                                  int mirror_num, unsigned long bio_flags)
 576 {
 577         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 578         struct extent_io_tree *tree;
 579         struct extent_map_tree *em_tree;
 580         struct compressed_bio *cb;
 581         unsigned long compressed_len;
 582         unsigned long nr_pages;
 583         unsigned long pg_index;
 584         struct page *page;
 585         struct block_device *bdev;
 586         struct bio *comp_bio;
 587         u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
 588         u64 em_len;
 589         u64 em_start;
 590         struct extent_map *em;
 591         int ret = -ENOMEM;
 592         int faili = 0;
 593         u32 *sums;
 594
 595         tree = &BTRFS_I(inode)->io_tree;
 596         em_tree = &BTRFS_I(inode)->extent_tree;
 597
 598         /* we need the actual starting offset of this extent in the file */
 599         read_lock(&em_tree->lock);
 600         em = lookup_extent_mapping(em_tree,
 601                                    page_offset(bio->bi_io_vec->bv_page),
 602                                    PAGE_SIZE);
 603         read_unlock(&em_tree->lock);
 604         if (!em)
 605                 return -EIO;
 606
 607         compressed_len = em->block_len;
 608         cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
 609         if (!cb)
 610                 goto out;
 611
 612         atomic_set(&cb->pending_bios, 0);
 613         cb->errors = 0;
 614         cb->inode = inode;
 615         cb->mirror_num = mirror_num;
 616         sums = &cb->sums;
 617
 618         cb->start = em->orig_start;
 619         em_len = em->len;
 620         em_start = em->start;
 621
 622         free_extent_map(em);
 623         em = NULL;
 624
 625         cb->len = bio->bi_iter.bi_size;
 626         cb->compressed_len = compressed_len;
 627         cb->compress_type = extent_compress_type(bio_flags);
 628         cb->orig_bio = bio;
 629
 630         nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
 631         cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *),
 632                                        GFP_NOFS);
 633         if (!cb->compressed_pages)
 634                 goto fail1;
 635
 636         bdev = fs_info->fs_devices->latest_bdev;
 637
 638         for (pg_index = 0; pg_index < nr_pages; pg_index++) {
 639                 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
 640                                                               __GFP_HIGHMEM);
 641                 if (!cb->compressed_pages[pg_index]) {
 642                         faili = pg_index - 1;
 643                         ret = -ENOMEM;
 644                         goto fail2;
 645                 }
 646         }
 647         faili = nr_pages - 1;
 648         cb->nr_pages = nr_pages;
 649
 650         add_ra_bio_pages(inode, em_start + em_len, cb);
 651
 652         /* include any pages we added in add_ra-bio_pages */
 653         cb->len = bio->bi_iter.bi_size;
 654
 655         comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
 656         if (!comp_bio)
 657                 goto fail2;
 658         bio_set_op_attrs (comp_bio, REQ_OP_READ, 0);
 659         comp_bio->bi_private = cb;
 660         comp_bio->bi_end_io = end_compressed_bio_read;
 661         atomic_inc(&cb->pending_bios);
 662
 663         for (pg_index = 0; pg_index < nr_pages; pg_index++) {
 664                 page = cb->compressed_pages[pg_index];
 665                 page->mapping = inode->i_mapping;
 666                 page->index = em_start >> PAGE_SHIFT;
 667
 668                 if (comp_bio->bi_iter.bi_size)
 669                         ret = tree->ops->merge_bio_hook(page, 0,
 670                                                         PAGE_SIZE,
 671                                                         comp_bio, 0);
 672                 else
 673                         ret = 0;
 674
 675                 page->mapping = NULL;
 676                 if (ret || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
 677                     PAGE_SIZE) {
 678                         bio_get(comp_bio);
 679
 680                         ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
 681                                                   BTRFS_WQ_ENDIO_DATA);
 682                         BUG_ON(ret); /* -ENOMEM */
 683
 684                         /*
 685                          * inc the count before we submit the bio so
 686                          * we know the end IO handler won't happen before
 687                          * we inc the count.  Otherwise, the cb might get
 688                          * freed before we're done setting it up
 689                          */
 690                         atomic_inc(&cb->pending_bios);
 691
 692                         if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
 693                                 ret = btrfs_lookup_bio_sums(inode, comp_bio,
 694                                                             sums);
 695                                 BUG_ON(ret); /* -ENOMEM */
 696                         }
 697                         sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
 698                                              fs_info->sectorsize);
 699
 700                         ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0);
 701                         if (ret) {
 702                                 comp_bio->bi_error = ret;
 703                                 bio_endio(comp_bio);
 704                         }
 705
 706                         bio_put(comp_bio);
 707
 708                         comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
 709                                                         GFP_NOFS);
 710                         BUG_ON(!comp_bio);
 711                         bio_set_op_attrs(comp_bio, REQ_OP_READ, 0);
 712                         comp_bio->bi_private = cb;
 713                         comp_bio->bi_end_io = end_compressed_bio_read;
 714
 715                         bio_add_page(comp_bio, page, PAGE_SIZE, 0);
 716                 }
 717                 cur_disk_byte += PAGE_SIZE;
 718         }
 719         bio_get(comp_bio);
 720
 721         ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
 722         BUG_ON(ret); /* -ENOMEM */
 723
 724         if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
 725                 ret = btrfs_lookup_bio_sums(inode, comp_bio, sums);
 726                 BUG_ON(ret); /* -ENOMEM */
 727         }
 728
 729         ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0);
 730         if (ret) {
 731                 comp_bio->bi_error = ret;
 732                 bio_endio(comp_bio);
 733         }
 734
 735         bio_put(comp_bio);
 736         return 0;
 737
 738 fail2:
 739         while (faili >= 0) {
 740                 __free_page(cb->compressed_pages[faili]);
 741                 faili--;
 742         }
 743
 744         kfree(cb->compressed_pages);
 745 fail1:
 746         kfree(cb);
 747 out:
 748         free_extent_map(em);
 749         return ret;
 750 }
 751
 752 static struct {
 753         struct list_head idle_ws;
 754         spinlock_t ws_lock;
 755         /* Number of free workspaces */
 756         int free_ws;
 757         /* Total number of allocated workspaces */
 758         atomic_t total_ws;
 759         /* Waiters for a free workspace */
 760         wait_queue_head_t ws_wait;
 761 } btrfs_comp_ws[BTRFS_COMPRESS_TYPES];
 762
 763 static const struct btrfs_compress_op * const btrfs_compress_op[] = {
 764         &btrfs_zlib_compress,
 765         &btrfs_lzo_compress,
 766 };
 767
 768 void __init btrfs_init_compress(void)
 769 {
 770         int i;
 771
 772         for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
 773                 struct list_head *workspace;
 774
 775                 INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
 776                 spin_lock_init(&btrfs_comp_ws[i].ws_lock);
 777                 atomic_set(&btrfs_comp_ws[i].total_ws, 0);
 778                 init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);
 779
 780                 /*
 781                  * Preallocate one workspace for each compression type so
 782                  * we can guarantee forward progress in the worst case
 783                  */
 784                 workspace = btrfs_compress_op[i]->alloc_workspace();
 785                 if (IS_ERR(workspace)) {
 786                         pr_warn("BTRFS: cannot preallocate compression workspace, will try later\n");
 787                 } else {
 788                         atomic_set(&btrfs_comp_ws[i].total_ws, 1);
 789                         btrfs_comp_ws[i].free_ws = 1;
 790                         list_add(workspace, &btrfs_comp_ws[i].idle_ws);
 791                 }
 792         }
 793 }
 794
 795 /*
 796  * This finds an available workspace or allocates a new one.
 797  * If it's not possible to allocate a new one, waits until there's one.
 798  * Preallocation makes a forward progress guarantees and we do not return
 799  * errors.
 800  */
 801 static struct list_head *find_workspace(int type)
 802 {
 803         struct list_head *workspace;
 804         int cpus = num_online_cpus();
 805         int idx = type - 1;
 806
 807         struct list_head *idle_ws       = &btrfs_comp_ws[idx].idle_ws;
 808         spinlock_t *ws_lock             = &btrfs_comp_ws[idx].ws_lock;
 809         atomic_t *total_ws              = &btrfs_comp_ws[idx].total_ws;
 810         wait_queue_head_t *ws_wait      = &btrfs_comp_ws[idx].ws_wait;
 811         int *free_ws                    = &btrfs_comp_ws[idx].free_ws;
 812 again:
 813         spin_lock(ws_lock);
 814         if (!list_empty(idle_ws)) {
 815                 workspace = idle_ws->next;
 816                 list_del(workspace);
 817                 (*free_ws)--;
 818                 spin_unlock(ws_lock);
 819                 return workspace;
 820
 821         }
 822         if (atomic_read(total_ws) > cpus) {
 823                 DEFINE_WAIT(wait);
 824
 825                 spin_unlock(ws_lock);
 826                 prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
 827                 if (atomic_read(total_ws) > cpus && !*free_ws)
 828                         schedule();
 829                 finish_wait(ws_wait, &wait);
 830                 goto again;
 831         }
 832         atomic_inc(total_ws);
 833         spin_unlock(ws_lock);
 834
 835         workspace = btrfs_compress_op[idx]->alloc_workspace();
 836         if (IS_ERR(workspace)) {
 837                 atomic_dec(total_ws);
 838                 wake_up(ws_wait);
 839
 840                 /*
 841                  * Do not return the error but go back to waiting. There's a
 842                  * workspace preallocated for each type and the compression
 843                  * time is bounded so we get to a workspace eventually. This
 844                  * makes our caller's life easier.
 845                  *
 846                  * To prevent silent and low-probability deadlocks (when the
 847                  * initial preallocation fails), check if there are any
 848                  * workspaces at all.
 849                  */
 850                 if (atomic_read(total_ws) == 0) {
 851                         static DEFINE_RATELIMIT_STATE(_rs,
 852                                         /* once per minute */ 60 * HZ,
 853                                         /* no burst */ 1);
 854
 855                         if (__ratelimit(&_rs)) {
 856                                 pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
 857                         }
 858                 }
 859                 goto again;
 860         }
 861         return workspace;
 862 }
 863
 864 /*
 865  * put a workspace struct back on the list or free it if we have enough
 866  * idle ones sitting around
 867  */
 868 static void free_workspace(int type, struct list_head *workspace)
 869 {
 870         int idx = type - 1;
 871         struct list_head *idle_ws       = &btrfs_comp_ws[idx].idle_ws;
 872         spinlock_t *ws_lock             = &btrfs_comp_ws[idx].ws_lock;
 873         atomic_t *total_ws              = &btrfs_comp_ws[idx].total_ws;
 874         wait_queue_head_t *ws_wait      = &btrfs_comp_ws[idx].ws_wait;
 875         int *free_ws                    = &btrfs_comp_ws[idx].free_ws;
 876
 877         spin_lock(ws_lock);
 878         if (*free_ws < num_online_cpus()) {
 879                 list_add(workspace, idle_ws);
 880                 (*free_ws)++;
 881                 spin_unlock(ws_lock);
 882                 goto wake;
 883         }
 884         spin_unlock(ws_lock);
 885
 886         btrfs_compress_op[idx]->free_workspace(workspace);
 887         atomic_dec(total_ws);
 888 wake:
 889         /*
 890          * Make sure counter is updated before we wake up waiters.
 891          */
 892         smp_mb();
 893         if (waitqueue_active(ws_wait))
 894                 wake_up(ws_wait);
 895 }
 896
 897 /*
 898  * cleanup function for module exit
 899  */
 900 static void free_workspaces(void)
 901 {
 902         struct list_head *workspace;
 903         int i;
 904
 905         for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
 906                 while (!list_empty(&btrfs_comp_ws[i].idle_ws)) {
 907                         workspace = btrfs_comp_ws[i].idle_ws.next;
 908                         list_del(workspace);
 909                         btrfs_compress_op[i]->free_workspace(workspace);
 910                         atomic_dec(&btrfs_comp_ws[i].total_ws);
 911                 }
 912         }
 913 }
 914
 915 /*
 916  * given an address space and start/len, compress the bytes.
 917  *
 918  * pages are allocated to hold the compressed result and stored
 919  * in 'pages'
 920  *
 921  * out_pages is used to return the number of pages allocated.  There
 922  * may be pages allocated even if we return an error
 923  *
 924  * total_in is used to return the number of bytes actually read.  It
 925  * may be smaller then len if we had to exit early because we
 926  * ran out of room in the pages array or because we cross the
 927  * max_out threshold.
 928  *
 929  * total_out is used to return the total number of compressed bytes
 930  *
 931  * max_out tells us the max number of bytes that we're allowed to
 932  * stuff into pages
 933  */
 934 int btrfs_compress_pages(int type, struct address_space *mapping,
 935                          u64 start, unsigned long len,
 936                          struct page **pages,
 937                          unsigned long nr_dest_pages,
 938                          unsigned long *out_pages,
 939                          unsigned long *total_in,
 940                          unsigned long *total_out,
 941                          unsigned long max_out)
 942 {
 943         struct list_head *workspace;
 944         int ret;
 945
 946         workspace = find_workspace(type);
 947
 948         ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
 949                                                       start, len, pages,
 950                                                       nr_dest_pages, out_pages,
 951                                                       total_in, total_out,
 952                                                       max_out);
 953         free_workspace(type, workspace);
 954         return ret;
 955 }
 956
 957 /*
 958  * pages_in is an array of pages with compressed data.
 959  *
 960  * disk_start is the starting logical offset of this array in the file
 961  *
 962  * orig_bio contains the pages from the file that we want to decompress into
 963  *
 964  * srclen is the number of bytes in pages_in
 965  *
 966  * The basic idea is that we have a bio that was created by readpages.
 967  * The pages in the bio are for the uncompressed data, and they may not
 968  * be contiguous.  They all correspond to the range of bytes covered by
 969  * the compressed extent.
 970  */
 971 static int btrfs_decompress_bio(int type, struct page **pages_in,
 972                                    u64 disk_start, struct bio *orig_bio,
 973                                    size_t srclen)
 974 {
 975         struct list_head *workspace;
 976         int ret;
 977
 978         workspace = find_workspace(type);
 979
 980         ret = btrfs_compress_op[type-1]->decompress_bio(workspace, pages_in,
 981                                                          disk_start, orig_bio,
 982                                                          srclen);
 983         free_workspace(type, workspace);
 984         return ret;
 985 }
 986
 987 /*
 988  * a less complex decompression routine.  Our compressed data fits in a
 989  * single page, and we want to read a single page out of it.
 990  * start_byte tells us the offset into the compressed data we're interested in
 991  */
 992 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
 993                      unsigned long start_byte, size_t srclen, size_t destlen)
 994 {
 995         struct list_head *workspace;
 996         int ret;
 997
 998         workspace = find_workspace(type);
 999
1000         ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
1001                                                   dest_page, start_byte,
1002                                                   srclen, destlen);
1003
1004         free_workspace(type, workspace);
1005         return ret;
1006 }
1007
1008 void btrfs_exit_compress(void)
1009 {
1010         free_workspaces();
1011 }
1012
1013 /*
1014  * Copy uncompressed data from working buffer to pages.
1015  *
1016  * buf_start is the byte offset we're of the start of our workspace buffer.
1017  *
1018  * total_out is the last byte of the buffer
1019  */
1020 int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
1021                               unsigned long total_out, u64 disk_start,
1022                               struct bio *bio)
1023 {
1024         unsigned long buf_offset;
1025         unsigned long current_buf_start;
1026         unsigned long start_byte;
1027         unsigned long working_bytes = total_out - buf_start;
1028         unsigned long bytes;
1029         char *kaddr;
1030         struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
1031
1032         /*
1033          * start byte is the first byte of the page we're currently
1034          * copying into relative to the start of the compressed data.
1035          */
1036         start_byte = page_offset(bvec.bv_page) - disk_start;
1037
1038         /* we haven't yet hit data corresponding to this page */
1039         if (total_out <= start_byte)
1040                 return 1;
1041
1042         /*
1043          * the start of the data we care about is offset into
1044          * the middle of our working buffer
1045          */
1046         if (total_out > start_byte && buf_start < start_byte) {
1047                 buf_offset = start_byte - buf_start;
1048                 working_bytes -= buf_offset;
1049         } else {
1050                 buf_offset = 0;
1051         }
1052         current_buf_start = buf_start;
1053
1054         /* copy bytes from the working buffer into the pages */
1055         while (working_bytes > 0) {
1056                 bytes = min_t(unsigned long, bvec.bv_len,
1057                                 PAGE_SIZE - buf_offset);
1058                 bytes = min(bytes, working_bytes);
1059
1060                 kaddr = kmap_atomic(bvec.bv_page);
1061                 memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
1062                 kunmap_atomic(kaddr);
1063                 flush_dcache_page(bvec.bv_page);
1064
1065                 buf_offset += bytes;
1066                 working_bytes -= bytes;
1067                 current_buf_start += bytes;
1068
1069                 /* check if we need to pick another page */
1070                 bio_advance(bio, bytes);
1071                 if (!bio->bi_iter.bi_size)
1072                         return 0;
1073                 bvec = bio_iter_iovec(bio, bio->bi_iter);
1074
1075                 start_byte = page_offset(bvec.bv_page) - disk_start;
1076
1077                 /*
1078                  * make sure our new page is covered by this
1079                  * working buffer
1080                  */
1081                 if (total_out <= start_byte)
1082                         return 1;
1083
1084                 /*
1085                  * the next page in the biovec might not be adjacent
1086                  * to the last page, but it might still be found
1087                  * inside this working buffer. bump our offset pointer
1088                  */
1089                 if (total_out > start_byte &&
1090                     current_buf_start < start_byte) {
1091                         buf_offset = start_byte - buf_start;
1092                         working_bytes = total_out - start_byte;
1093                         current_buf_start = buf_start + buf_offset;
1094                 }
1095         }
1096
1097         return 1;
1098 }