Use 1 R/W spinlock

sftl.c

@@ -163,56 +163,62 @@ static void sftl_make_request(struct request_queue *q, struct bio *bio)
 	}
 	else
 	{
+		// 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 on buffer
+		// * Take write lock
 		// * Check for free space in buffer
 		// * If sufficient:
-		// ** Take write lock on translation maps so readers won't get them partially modified
 		// ** Write current bio into buffer
 		// ** Modify translation maps
-		// ** Unlock translation maps
 		// * If insufficient:
-		// ** Check flush flag (no need for atomic/etc as already within buffer lock)
+		// ** (Insufficient) Check flush flag (no need for atomic/etc as already within buffer lock)
 		// ** If someone is already flushing:
-		// *** Unlock buffer
+		// *** 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 buffer
+		// * Unlock
 		//
 		// After (Flush) operation ends:
-		// * Take write lock on the buffer (writers are already blocked, this is to block readers)
+		// * 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 buffer
+		// ** Unlock
 		// ** Wake up waiting writers
 		// * If not:
 		// ** Initiate cleaning process
-		// ** Unlock buffer
+		// ** Unlock
 		//
 		// After cleaning operation ends:
-		// * Take write lock on translation maps
+		// * Take write lock
 		// * Modify translation maps
-		// * Unlock translation maps
-		// * Take write lock on the buffer
 		// * Move free sequence pointer
 		// * If there are no more pending cleaning operations:
 		// ** Perform own remembered write operation:
-		// *** Take write lock on translation maps so readers won't get them partially modified
 		// *** Write current bio into buffer
 		// *** Modify translation maps
-		// *** Unlock translation maps
 		// ** Unset flush flag
-		// ** Unlock buffer
+		// ** Unlock
 		// ** Wake up waiting writers
 		// * Else:
 		// ** Initiate next cleaning operation
-		// ** Unlock buffer
+		// ** Unlock
 		struct sftl_map *buf_map = (struct sftl_map *)(sftl->buf + seg_clust*clust_sz) + sftl->buf_size;
 		char *buffer = __bio_kmap_atomic(bio, 0, KM_USER0);
 		memcpy(sftl->buf + clust_sz*sftl->buf_size, buffer, clust_sz);