Fix inconsistencies and typos in the tree

This is numbered take 7, and addresses a set of issues around:
- Fixes for typos and incorrect reference names.
- Removal of unneeded comments.
- Removal of unreferenced functions and structures.
- Fixes regarding variable name consistency.

Author: Alexander Lakhin
Discussion: https://postgr.es/m/10bfd4ac-3e7c-40ab-2b2e-355ed15495e8@gmail.com

src/backend/storage/buffer/bufmgr.c

@@ -438,7 +438,8 @@ static void PinBuffer_Locked(BufferDesc *buf);
 static void UnpinBuffer(BufferDesc *buf, bool fixOwner);
 static void BufferSync(int flags);
 static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
-static int	SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *flush_context);
+static int	SyncOneBuffer(int buf_id, bool skip_recently_used,
+						  WritebackContext *wb_context);
 static void WaitIO(BufferDesc *buf);
 static bool StartBufferIO(BufferDesc *buf, bool forInput);
 static void TerminateBufferIO(BufferDesc *buf, bool clear_dirty,
@@ -2346,7 +2347,7 @@ BgBufferSync(WritebackContext *wb_context)
  *	BUF_REUSABLE: buffer is available for replacement, ie, it has
  *		pin count 0 and usage count 0.
  *
- * (BUF_WRITTEN could be set in error if FlushBuffers finds the buffer clean
+ * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
  * after locking it, but we don't care all that much.)
  *
  * Note: caller must have done ResourceOwnerEnlargeBuffers.

src/backend/storage/file/buffile.c

@@ -664,7 +664,7 @@ BufFileSeek(BufFile *file, int fileno, off_t offset, int whence)
 
 			/*
 			 * Relative seek considers only the signed offset, ignoring
-			 * fileno. Note that large offsets (> 1 gig) risk overflow in this
+			 * fileno. Note that large offsets (> 1 GB) risk overflow in this
 			 * add, unless we have 64-bit off_t.
 			 */
 			newFile = file->curFile;

src/backend/storage/file/fd.c

@@ -897,7 +897,7 @@ count_usable_fds(int max_to_probe, int *usable_fds, int *already_open)
 
 /*
  * set_max_safe_fds
- *		Determine number of filedescriptors that fd.c is allowed to use
+ *		Determine number of file descriptors that fd.c is allowed to use
  */
 void
 set_max_safe_fds(void)

src/backend/storage/freespace/freespace.c

@@ -223,7 +223,7 @@ XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
 }
 
 /*
- * GetRecordedFreePage - return the amount of free space on a particular page,
+ * GetRecordedFreeSpace - return the amount of free space on a particular page,
  *		according to the FSM.
  */
 Size
@@ -417,7 +417,7 @@ fsm_space_cat_to_avail(uint8 cat)
 
 /*
  * Which category does a page need to have, to accommodate x bytes of data?
- * While fsm_size_to_avail_cat() rounds down, this needs to round up.
+ * While fsm_space_avail_to_cat() rounds down, this needs to round up.
  */
 static uint8
 fsm_space_needed_to_cat(Size needed)

src/backend/storage/lmgr/lock.c

@@ -216,9 +216,9 @@ static PROCLOCK *FastPathGetRelationLockEntry(LOCALLOCK *locallock);
 
 /*
  * To make the fast-path lock mechanism work, we must have some way of
- * preventing the use of the fast-path when a conflicting lock might be
- * present.  We partition* the locktag space into FAST_PATH_HASH_BUCKETS
- * partitions, and maintain an integer count of the number of "strong" lockers
+ * preventing the use of the fast-path when a conflicting lock might be present.
+ * We partition* the locktag space into FAST_PATH_STRONG_LOCK_HASH_PARTITIONS,
+ * and maintain an integer count of the number of "strong" lockers
  * in each partition.  When any "strong" lockers are present (which is
  * hopefully not very often), the fast-path mechanism can't be used, and we
  * must fall back to the slower method of pushing matching locks directly
@@ -2709,7 +2709,7 @@ FastPathTransferRelationLocks(LockMethod lockMethodTable, const LOCKTAG *locktag
 }
 
 /*
- * FastPathGetLockEntry
+ * FastPathGetRelationLockEntry
  *		Return the PROCLOCK for a lock originally taken via the fast-path,
  *		transferring it to the primary lock table if necessary.
  *
@@ -2896,8 +2896,8 @@ GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode, int *countp)
 			 * the lock, then we needn't examine the individual relation IDs
 			 * at all; none of them can be relevant.
 			 *
-			 * See FastPathTransferLocks() for discussion of why we do this
-			 * test after acquiring the lock.
+			 * See FastPathTransferRelationLocks() for discussion of why we do
+			 * this test after acquiring the lock.
 			 */
 			if (proc->databaseId != locktag->locktag_field1)
 			{

src/backend/storage/lmgr/predicate.c

@@ -3405,8 +3405,8 @@ ReleasePredicateLocks(bool isCommit, bool isReadOnlySafe)
 	 *
 	 * If this value is changing, we don't care that much whether we get the
 	 * old or new value -- it is just used to determine how far
-	 * GlobalSerializableXmin must advance before this transaction can be
-	 * fully cleaned up.  The worst that could happen is we wait for one more
+	 * SxactGlobalXmin must advance before this transaction can be fully
+	 * cleaned up.  The worst that could happen is we wait for one more
 	 * transaction to complete before freeing some RAM; correctness of visible
 	 * behavior is not affected.
 	 */
@@ -4820,7 +4820,7 @@ OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
  *
  * If a dangerous structure is found, the pivot (the near conflict) is
  * marked for death, because rolling back another transaction might mean
- * that we flail without ever making progress.  This transaction is
+ * that we fail without ever making progress.  This transaction is
  * committing writes, so letting it commit ensures progress.  If we
  * canceled the far conflict, it might immediately fail again on retry.
  */