Btrfs: Add backport for the kthread work on kernels older than 2.6.20

 * Boston, MA 021110-1307, USA.

 */

#include <linux/version.h>

#include <linux/kthread.h>

#include <linux/list.h>

#include <linux/spinlock.h>

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,20)

# include <linux/freezer.h>

#else

# include <linux/sched.h>

#endif

#include "async-thread.h"

/*