Be more consistent about masking xl_info with ~XLR_INFO_MASK.

Generally, WAL resource managers are only supposed to examine the
top 4 bits of a WAL record's xl_info; the rest are reserved for
the WAL mechanism itself.  A few places were not consistent about
doing this with respect to XLOG_CHECKPOINT and XLOG_SWITCH records.
There's no bug currently, since no additional bits ever get set in
these specific record types, but that might not be true forever.
Let's follow the generic coding rule here too.

Michael Paquier

src/backend/access/transam/xlog.c

@@ -903,8 +903,9 @@ XLogInsertRecord(XLogRecData *rdata, XLogRecPtr fpw_lsn)
 	pg_crc32c	rdata_crc;
 	bool		inserted;
 	XLogRecord *rechdr = (XLogRecord *) rdata->data;
+	uint8		info = rechdr->xl_info & ~XLR_INFO_MASK;
 	bool		isLogSwitch = (rechdr->xl_rmid == RM_XLOG_ID &&
-							   rechdr->xl_info == XLOG_SWITCH);
+							   info == XLOG_SWITCH);
 	XLogRecPtr	StartPos;
 	XLogRecPtr	EndPos;
 
@@ -6170,7 +6171,7 @@ StartupXLOG(void)
 		if (record != NULL)
 		{
 			memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint));
-			wasShutdown = (record->xl_info == XLOG_CHECKPOINT_SHUTDOWN);
+			wasShutdown = ((record->xl_info & ~XLR_INFO_MASK) == XLOG_CHECKPOINT_SHUTDOWN);
 			ereport(DEBUG1,
 					(errmsg("checkpoint record is at %X/%X",
 				   (uint32) (checkPointLoc >> 32), (uint32) checkPointLoc)));
@@ -6328,7 +6329,7 @@ StartupXLOG(void)
 					 (errmsg("could not locate a valid checkpoint record")));
 		}
 		memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint));
-		wasShutdown = (record->xl_info == XLOG_CHECKPOINT_SHUTDOWN);
+		wasShutdown = ((record->xl_info & ~XLR_INFO_MASK) == XLOG_CHECKPOINT_SHUTDOWN);
 	}
 
 	/*
@@ -7785,6 +7786,7 @@ ReadCheckpointRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr,
 					 int whichChkpt, bool report)
 {
 	XLogRecord *record;
+	uint8		info;
 
 	if (!XRecOffIsValid(RecPtr))
 	{
@@ -7810,6 +7812,7 @@ ReadCheckpointRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr,
 	}
 
 	record = ReadRecord(xlogreader, RecPtr, LOG, true);
+	info = record->xl_info & ~XLR_INFO_MASK;
 
 	if (record == NULL)
 	{
@@ -7852,8 +7855,8 @@ ReadCheckpointRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr,
 		}
 		return NULL;
 	}
-	if (record->xl_info != XLOG_CHECKPOINT_SHUTDOWN &&
-		record->xl_info != XLOG_CHECKPOINT_ONLINE)
+	if (info != XLOG_CHECKPOINT_SHUTDOWN &&
+		info != XLOG_CHECKPOINT_ONLINE)
 	{
 		switch (whichChkpt)
 		{

src/backend/access/transam/xlogreader.c

@@ -462,7 +462,8 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
 	/*
 	 * Special processing if it's an XLOG SWITCH record
 	 */
-	if (record->xl_rmid == RM_XLOG_ID && record->xl_info == XLOG_SWITCH)
+	if (record->xl_rmid == RM_XLOG_ID &&
+		(record->xl_info & ~XLR_INFO_MASK) == XLOG_SWITCH)
 	{
 		/* Pretend it extends to end of segment */
 		state->EndRecPtr += XLogSegSize - 1;