BTRFS_BACKREF_REV_SHIFT  144 fs/btrfs/ctree.h 					 BTRFS_BACKREF_REV_SHIFT)
BTRFS_BACKREF_REV_SHIFT 1912 fs/btrfs/ctree.h 	return flags >> BTRFS_BACKREF_REV_SHIFT;
BTRFS_BACKREF_REV_SHIFT 1920 fs/btrfs/ctree.h 	flags |= (u64)rev << BTRFS_BACKREF_REV_SHIFT;