btrfs: prepare incompat flags for more compression methods

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: lz4: add wrapper functions and enable it

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: add lz4hc incompat bits

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: add lz4hc wrapper and enable it

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: reduce duplicate code in lz4_wrapper.c

Add generic functions for compress_pages and alloc that accept an argument to
enable high compression, and replace the lz4/lz4hc variants of both with
wrappers for these.

Signed-off-by: Andrew Mahone <andrew.mahone@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Btrfs need LZ4 api
Revert "Merge remote-tracking branch 'btrfs-unstable/dev/lz4-311' into 3.11/btrfs-lz4"

This reverts commit 9789e094ddeb7d3ea1f4c8906908a60636f44e63, reversing
changes made to 5ae90d8e467e625e447000cb4335c4db973b1095.
Merge branch '3.11/btrfs-lz4' into 3.11/my