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 struct 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
  76 void btrfs_init_compress(void);
  77 void btrfs_exit_compress(void);
  78
  79 int 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);
  84 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
  85                      unsigned long start_byte, size_t srclen, size_t destlen);
  86 int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
  87                               unsigned long total_out, u64 disk_start,
  88                               struct bio *bio);
  89
  90 blk_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);
  95 blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
  96                                  int mirror_num, unsigned long bio_flags);
  97
  98 enum 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
 106 struct 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
 129 extern const struct btrfs_compress_op btrfs_zlib_compress;
 130 extern const struct btrfs_compress_op btrfs_lzo_compress;
 131
 132 #endif