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