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    btrfs: Add lzo compression support · a6fa6fae
    Li Zefan authored
    
    
    Lzo is a much faster compression algorithm than gzib, so would allow
    more users to enable transparent compression, and some users can
    choose from compression ratio and speed for different applications
    
    Usage:
    
     # mount -t btrfs -o compress[=<zlib,lzo>] dev /mnt
    or
     # mount -t btrfs -o compress-force[=<zlib,lzo>] dev /mnt
    
    "-o compress" without argument is still allowed for compatability.
    
    Compatibility:
    
    If we mount a filesystem with lzo compression, it will not be able be
    mounted in old kernels. One reason is, otherwise btrfs will directly
    dump compressed data, which sits in inline extent, to user.
    
    Performance:
    
    The test copied a linux source tarball (~400M) from an ext4 partition
    to the btrfs partition, and then extracted it.
    
    (time in second)
               lzo        zlib        nocompress
    copy:      10.6       21.7        14.9
    extract:   70.1       94.4        66.6
    
    (data size in MB)
               lzo        zlib        nocompress
    copy:      185.87     108.69      394.49
    extract:   193.80     132.36      381.21
    
    Changelog:
    
    v1 -> v2:
    - Select LZO_COMPRESS and LZO_DECOMPRESS in btrfs Kconfig.
    - Add incompability flag.
    - Fix error handling in compress code.
    
    Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
    a6fa6fae