Below variables are defined per compress type.
 - struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES]
 - spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES]
 - int comp_num_workspace[BTRFS_COMPRESS_TYPES]
 - atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES]
 - wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES]

BTW, while accessing one compress type of these variables, the next or
before address is other compress types of it.
So this patch puts these variables in a struct to make cache friendly.
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NByongho Lee <bhlee.kernel@gmail.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>