btrfs: Add lzo compression support

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: Li Zefan <lizf@cn.fujitsu.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 9b5f2f3..f7ce217 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -73,5 +73,6 @@ struct btrfs_compress_op {
 };
 
 extern struct btrfs_compress_op btrfs_zlib_compress;
+extern struct btrfs_compress_op btrfs_lzo_compress;
 
 #endif