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