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
  37 void btrfs_init_compress(void);
  38 void btrfs_exit_compress(void);
  39
  40 int btrfs_compress_pages(int type, struct address_space *mapping,
  41                          u64 start, struct page **pages,
  42                          unsigned long *out_pages,
  43                          unsigned long *total_in,
  44                          unsigned long *total_out);
  45 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
  46                      unsigned long start_byte, size_t srclen, size_t destlen);
  47 int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
  48                               unsigned long total_out, u64 disk_start,
  49                               struct bio *bio);
  50
  51 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
  52                                   unsigned long len, u64 disk_start,
  53                                   unsigned long compressed_len,
  54                                   struct page **compressed_pages,
  55                                   unsigned long nr_pages);
  56 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
  57                                  int mirror_num, unsigned long bio_flags);
  58
  59 enum btrfs_compression_type {
  60         BTRFS_COMPRESS_NONE  = 0,
  61         BTRFS_COMPRESS_ZLIB  = 1,
  62         BTRFS_COMPRESS_LZO   = 2,
  63         BTRFS_COMPRESS_TYPES = 2,
  64         BTRFS_COMPRESS_LAST  = 3,
  65 };
  66
  67 struct btrfs_compress_op {
  68         struct list_head *(*alloc_workspace)(void);
  69
  70         void (*free_workspace)(struct list_head *workspace);
  71
  72         int (*compress_pages)(struct list_head *workspace,
  73                               struct address_space *mapping,
  74                               u64 start,
  75                               struct page **pages,
  76                               unsigned long *out_pages,
  77                               unsigned long *total_in,
  78                               unsigned long *total_out);
  79
  80         int (*decompress_bio)(struct list_head *workspace,
  81                                  struct page **pages_in,
  82                                  u64 disk_start,
  83                                  struct bio *orig_bio,
  84                                  size_t srclen);
  85
  86         int (*decompress)(struct list_head *workspace,
  87                           unsigned char *data_in,
  88                           struct page *dest_page,
  89                           unsigned long start_byte,
  90                           size_t srclen, size_t destlen);
  91 };
  92
  93 extern const struct btrfs_compress_op btrfs_zlib_compress;
  94 extern const struct btrfs_compress_op btrfs_lzo_compress;
  95
  96 #endif