Fix inconsistencies and typos in the tree

This is numbered take 8, and addresses again a set of issues with code
comments, variable names and unreferenced variables.

Author: Alexander Lakhin
Discussion: https://postgr.es/m/b137b5eb-9c95-9c2f-586e-38aba7d59788@gmail.com

src/backend/access/common/bufmask.c

@@ -20,7 +20,7 @@
 #include "access/bufmask.h"
 
 /*
- * mask_page_lsn
+ * mask_page_lsn_and_checksum
  *
  * In consistency checks, the LSN of the two pages compared will likely be
  * different because of concurrent operations when the WAL is generated and

src/backend/access/gin/gindatapage.c

@@ -1371,7 +1371,7 @@ disassembleLeaf(Page page)
 	if (GinPageIsCompressed(page))
 	{
 		/*
-		 * Create a leafSegment entry for each segment.
+		 * Create a leafSegmentInfo entry for each segment.
 		 */
 		seg = GinDataLeafPageGetPostingList(page);
 		segbegin = (Pointer) seg;

src/backend/access/heap/rewriteheap.c

@@ -237,7 +237,7 @@ static void logical_end_heap_rewrite(RewriteState state);
  * new_heap		new, locked heap relation to insert tuples to
  * oldest_xmin	xid used by the caller to determine which tuples are dead
  * freeze_xid	xid before which tuples will be frozen
- * min_multi	multixact before which multis will be removed
+ * cutoff_multi	multixact before which multis will be removed
  * use_wal		should the inserts to the new heap be WAL-logged?
  *
  * Returns an opaque RewriteState, allocated in current memory context,
@@ -787,7 +787,7 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
  * Instead we simply write the mapping files out to disk, *before* the
  * XLogInsert() is performed. That guarantees that either the XLogInsert() is
  * inserted after the checkpoint's redo pointer or that the checkpoint (via
- * LogicalRewriteHeapCheckpoint()) has flushed the (partial) mapping file to
+ * CheckPointLogicalRewriteHeap()) has flushed the (partial) mapping file to
  * disk. That leaves the tail end that has not yet been flushed open to
  * corruption, which is solved by including the current offset in the
  * xl_heap_rewrite_mapping records and truncating the mapping file to it

src/backend/access/spgist/spgvacuum.c

@@ -842,7 +842,7 @@ spgvacuumscan(spgBulkDeleteState *bds)
 		}
 	}
 
-	/* Propagate local lastUsedPage cache to metablock */
+	/* Propagate local lastUsedPages cache to metablock */
 	SpGistUpdateMetaPage(index);
 
 	/*

src/backend/access/transam/xact.c

@@ -1988,7 +1988,7 @@ StartTransaction(void)
 
 	/*
 	 * Advertise it in the proc array.  We assume assignment of
-	 * LocalTransactionID is atomic, and the backendId should be set already.
+	 * localTransactionId is atomic, and the backendId should be set already.
 	 */
 	Assert(MyProc->backendId == vxid.backendId);
 	MyProc->lxid = vxid.localTransactionId;

src/backend/access/transam/xlog.c

@@ -1796,11 +1796,11 @@ WaitXLogInsertionsToFinish(XLogRecPtr upto)
 		do
 		{
 			/*
-			 * See if this insertion is in progress. LWLockWait will wait for
-			 * the lock to be released, or for the 'value' to be set by a
-			 * LWLockUpdateVar call.  When a lock is initially acquired, its
-			 * value is 0 (InvalidXLogRecPtr), which means that we don't know
-			 * where it's inserting yet.  We will have to wait for it.  If
+			 * See if this insertion is in progress.  LWLockWaitForVar will
+			 * wait for the lock to be released, or for the 'value' to be set
+			 * by a LWLockUpdateVar call.  When a lock is initially acquired,
+			 * its value is 0 (InvalidXLogRecPtr), which means that we don't
+			 * know where it's inserting yet.  We will have to wait for it. If
 			 * it's a small insertion, the record will most likely fit on the
 			 * same page and the inserter will release the lock without ever
 			 * calling LWLockUpdateVar.  But if it has to sleep, it will
@@ -6024,7 +6024,10 @@ recoveryApplyDelay(XLogReaderState *record)
 		TimestampDifference(GetCurrentTimestamp(), recoveryDelayUntilTime,
 							&secs, &microsecs);
 
-		/* NB: We're ignoring waits below min_apply_delay's resolution. */
+		/*
+		 * NB: We're ignoring waits below recovery_min_apply_delay's
+		 * resolution.
+		 */
 		if (secs <= 0 && microsecs / 1000 <= 0)
 			break;