Centralize timestamp computation of control file on updates

This commit moves the timestamp computation of the control file within
the routine of src/common/ in charge of updating the backend's control
file, which is shared by multiple frontend tools (pg_rewind,
pg_checksums and pg_resetwal) and the backend itself.

This change has as direct effect to update the control file's timestamp
when writing the control file in pg_rewind and pg_checksums, something
that is helpful to keep track of control file updates for those
operations, something also tracked by the backend at startup within its
logs.  This part is arguably a bug, as ControlFileData->time should be
updated each time a new version of the control file is written, but this
is a behavior change so no backpatch is done.

Author: Amul Sul
Reviewed-by: Nathan Bossart, Michael Paquier, Bharath Rupireddy
Discussion: https://postgr.es/m/CAAJ_b97nd_ghRpyFV9Djf9RLXkoTbOUqnocq11WGq9TisX09Fw@mail.gmail.com

Author: michaelpq

src/backend/access/transam/xlog.c

@@ -7339,7 +7339,7 @@ StartupXLOG(void)
 				ControlFile->backupEndPoint = ControlFile->minRecoveryPoint;
 			}
 		}
-		ControlFile->time = (pg_time_t) time(NULL);
+
 		/* No need to hold ControlFileLock yet, we aren't up far enough */
 		UpdateControlFile();
 
@@ -8199,7 +8199,6 @@ StartupXLOG(void)
 	 */
 	LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
 	ControlFile->state = DB_IN_PRODUCTION;
-	ControlFile->time = (pg_time_t) time(NULL);
 
 	SpinLockAcquire(&XLogCtl->info_lck);
 	XLogCtl->SharedRecoveryState = RECOVERY_STATE_DONE;
@@ -9142,7 +9141,6 @@ CreateCheckPoint(int flags)
 	{
 		LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
 		ControlFile->state = DB_SHUTDOWNING;
-		ControlFile->time = (pg_time_t) time(NULL);
 		UpdateControlFile();
 		LWLockRelease(ControlFileLock);
 	}
@@ -9412,7 +9410,6 @@ CreateCheckPoint(int flags)
 		ControlFile->state = DB_SHUTDOWNED;
 	ControlFile->checkPoint = ProcLastRecPtr;
 	ControlFile->checkPointCopy = checkPoint;
-	ControlFile->time = (pg_time_t) time(NULL);
 	/* crash recovery should always recover to the end of WAL */
 	ControlFile->minRecoveryPoint = InvalidXLogRecPtr;
 	ControlFile->minRecoveryPointTLI = 0;
@@ -9539,7 +9536,6 @@ CreateEndOfRecoveryRecord(void)
 	 * changes to this point.
 	 */
 	LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-	ControlFile->time = (pg_time_t) time(NULL);
 	ControlFile->minRecoveryPoint = recptr;
 	ControlFile->minRecoveryPointTLI = xlrec.ThisTimeLineID;
 	UpdateControlFile();
@@ -9740,7 +9736,6 @@ CreateRestartPoint(int flags)
 		{
 			LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
 			ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
-			ControlFile->time = (pg_time_t) time(NULL);
 			UpdateControlFile();
 			LWLockRelease(ControlFileLock);
 		}
@@ -9801,7 +9796,6 @@ CreateRestartPoint(int flags)
 	{
 		ControlFile->checkPoint = lastCheckPointRecPtr;
 		ControlFile->checkPointCopy = lastCheckPoint;
-		ControlFile->time = (pg_time_t) time(NULL);
 
 		/*
 		 * Ensure minRecoveryPoint is past the checkpoint record.  Normally,

src/bin/pg_resetwal/pg_resetwal.c

@@ -911,7 +911,6 @@ RewriteControlFile(void)
 	ControlFile.checkPointCopy.time = (pg_time_t) time(NULL);
 
 	ControlFile.state = DB_SHUTDOWNED;
-	ControlFile.time = (pg_time_t) time(NULL);
 	ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
 	ControlFile.minRecoveryPoint = 0;
 	ControlFile.minRecoveryPointTLI = 0;

src/common/controldata_utils.c

@@ -23,6 +23,7 @@
 #include <unistd.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <time.h>
 
 #include "access/xlog_internal.h"
 #include "catalog/pg_control.h"
@@ -168,6 +169,9 @@ update_controlfile(const char *DataDir,
 	StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE,
 					 "sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE");
 
+	/* Update timestamp  */
+	ControlFile->time = (pg_time_t) time(NULL);
+
 	/* Recalculate CRC of control file */
 	INIT_CRC32C(ControlFile->crc);
 	COMP_CRC32C(ControlFile->crc,