btrfs: Allow to add new compression algorithm

Make the code aware of compression type, instead of always assuming
zlib compression.

Also make the zlib workspace function as common code for all
compression types.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index ab6d74b6e647..28b44dbd1e35 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -26,7 +26,8 @@ struct extent_map {
         unsigned long flags;
         struct block_device *bdev;
         atomic_t refs;
-        int in_tree;
+        unsigned int in_tree:1;
+        unsigned int compress_type:4;
 };
 
 struct extent_map_tree {