void merge_left(BufferHead *left, BufferHead *right);
bool can_merge_bh(BufferHead *left, BufferHead *right);
void try_merge_bh(BufferHead *bh);
+ void maybe_rebuild_buffer(BufferHead *bh);
bool is_cached(loff_t off, loff_t len) const;
bool include_all_cached_data(loff_t off, loff_t len);