LXR linux/fs/btrfs/compression.h

   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#ifndef __BTRFS_COMPRESSION_
  20#define __BTRFS_COMPRESSION_
  21
  22/*
  23 * We want to make sure that amount of RAM required to uncompress an extent is
  24 * reasonable, so we limit the total size in ram of a compressed extent to
  25 * 128k.  This is a crucial number because it also controls how easily we can
  26 * spread reads across cpus for decompression.
  27 *
  28 * We also want to make sure the amount of IO required to do a random read is
  29 * reasonably small, so we limit the size of a compressed extent to 128k.
  30 */
  31
  32/* Maximum length of compressed data stored on disk */
  33#define BTRFS_MAX_COMPRESSED            (SZ_128K)
  34/* Maximum size of data before compression */
  35#define BTRFS_MAX_UNCOMPRESSED          (SZ_128K)
  36
  37struct compressed_bio {
  38        /* number of bios pending for this compressed extent */
  39        refcount_t pending_bios;
  40
  41        /* the pages with the compressed data on them */
  42        struct page **compressed_pages;
  43
  44        /* inode that owns this data */
  45        struct inode *inode;
  46
  47        /* starting offset in the inode for our pages */
  48        u64 start;
  49
  50        /* number of bytes in the inode we're working on */
  51        unsigned long len;
  52
  53        /* number of bytes on disk */
  54        unsigned long compressed_len;
  55
  56        /* the compression algorithm for this bio */
  57        int compress_type;
  58
  59        /* number of compressed pages in the array */
  60        unsigned long nr_pages;
  61
  62        /* IO errors */
  63        int errors;
  64        int mirror_num;
  65
  66        /* for reads, this is the bio we are copying the data into */
  67        struct bio *orig_bio;
  68
  69        /*
  70         * the start of a variable length array of checksums only
  71         * used by reads
  72         */
  73        u32 sums;
  74};
  75
  76void btrfs_init_compress(void);
  77void btrfs_exit_compress(void);
  78
  79int btrfs_compress_pages(int type, struct address_space *mapping,
  80                         u64 start, struct page **pages,
  81                         unsigned long *out_pages,
  82                         unsigned long *total_in,
  83                         unsigned long *total_out);
  84int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
  85                     unsigned long start_byte, size_t srclen, size_t destlen);
  86int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
  87                              unsigned long total_out, u64 disk_start,
  88                              struct bio *bio);
  89
  90blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
  91                                  unsigned long len, u64 disk_start,
  92                                  unsigned long compressed_len,
  93                                  struct page **compressed_pages,
  94                                  unsigned long nr_pages);
  95blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
  96                                 int mirror_num, unsigned long bio_flags);
  97
  98enum btrfs_compression_type {
  99        BTRFS_COMPRESS_NONE  = 0,
 100        BTRFS_COMPRESS_ZLIB  = 1,
 101        BTRFS_COMPRESS_LZO   = 2,
 102        BTRFS_COMPRESS_TYPES = 2,
 103        BTRFS_COMPRESS_LAST  = 3,
 104};
 105
 106struct btrfs_compress_op {
 107        struct list_head *(*alloc_workspace)(void);
 108
 109        void (*free_workspace)(struct list_head *workspace);
 110
 111        int (*compress_pages)(struct list_head *workspace,
 112                              struct address_space *mapping,
 113                              u64 start,
 114                              struct page **pages,
 115                              unsigned long *out_pages,
 116                              unsigned long *total_in,
 117                              unsigned long *total_out);
 118
 119        int (*decompress_bio)(struct list_head *workspace,
 120                                struct compressed_bio *cb);
 121
 122        int (*decompress)(struct list_head *workspace,
 123                          unsigned char *data_in,
 124                          struct page *dest_page,
 125                          unsigned long start_byte,
 126                          size_t srclen, size_t destlen);
 127};
 128
 129extern const struct btrfs_compress_op btrfs_zlib_compress;
 130extern const struct btrfs_compress_op btrfs_lzo_compress;
 131
 132#endif
 133