R/W locking using 1 R/W spinlock and 1 event.

Reading:
* Take read lock
* Check if requested cluster is mapped into buffer
* If yes:
** Read from the buffer
* If no:
** Initiate block read operation
* Unlock

Writing:
(Start):
* Take write lock
* Check for free space in buffer
* If sufficient:
** Write current bio into buffer
** Modify translation maps
* If insufficient:
** (Insufficient) Check flush flag (no need for atomic/etc as already within buffer lock)
** If someone is already flushing:
*** Unlock
*** Wait until flushing ends using an event
*** Goto (Start)
** If no one is flushing yet:
*** Set flush flag
*** Remember current bio and initiate (Flush) operation
* Unlock

After (Flush) operation ends:
* Take write lock (writers are already blocked, this is to block readers)
* Clear buffer
* If the free sequence pointer can be moved without cleaning:
** Move pointer
** Perform own remembered write operation
** Unset flush flag
** Unlock
** Wake up waiting writers
* If not:
** Initiate cleaning process
** Unlock

After cleaning operation ends:
* Take write lock
* Modify translation maps
* Move free sequence pointer
* If there are no more pending cleaning operations:
** Perform own remembered write operation:
*** Write current bio into buffer
*** Modify translation maps
** Unset flush flag
** Unlock
** Wake up waiting writers
* Else:
** Initiate next cleaning operation
** Unlock