int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
int bits, struct extent_state **cached, gfp_t mask);
int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
int bits, struct extent_state **cached, gfp_t mask);
int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);