From a228cc13aeabff308d6dfc98a1015865f5393fce Mon Sep 17 00:00:00 2001
From: Magnus Hagander <magnus@hagander.net>
Date: Mon, 9 Apr 2018 19:02:42 +0200
Subject: Revert "Allow on-line enabling and disabling of data checksums"

This reverts the backend sides of commit 1fde38beaa0c3e66c340efc7cc0dc272d6254bb0.
I have, at least for now, left the pg_verify_checksums tool in place, as
this tool can be very valuable without the rest of the patch as well,
and since it's a read-only tool that only runs when the cluster is down
it should be a lot safer.
---
 src/backend/access/transam/xlog.c | 124 ++------------------------------------
 1 file changed, 6 insertions(+), 118 deletions(-)

(limited to 'src/backend/access/transam/xlog.c')

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 4a47395174c..a51df6b0b90 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -856,7 +856,6 @@ static void SetLatestXTime(TimestampTz xtime);
 static void SetCurrentChunkStartTime(TimestampTz xtime);
 static void CheckRequiredParameterValues(void);
 static void XLogReportParameters(void);
-static void XlogChecksums(ChecksumType new_type);
 static void checkTimeLineSwitch(XLogRecPtr lsn, TimeLineID newTLI,
 					TimeLineID prevTLI);
 static void LocalSetXLogInsertAllowed(void);
@@ -1034,7 +1033,7 @@ XLogInsertRecord(XLogRecData *rdata,
 		Assert(RedoRecPtr < Insert->RedoRecPtr);
 		RedoRecPtr = Insert->RedoRecPtr;
 	}
-	doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites || DataChecksumsInProgress());
+	doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites);
 
 	if (fpw_lsn != InvalidXLogRecPtr && fpw_lsn <= RedoRecPtr && doPageWrites)
 	{
@@ -4674,6 +4673,10 @@ ReadControlFile(void)
 		(SizeOfXLogLongPHD - SizeOfXLogShortPHD);
 
 	CalculateCheckpointSegments();
+
+	/* Make the initdb settings visible as GUC variables, too */
+	SetConfigOption("data_checksums", DataChecksumsEnabled() ? "yes" : "no",
+					PGC_INTERNAL, PGC_S_OVERRIDE);
 }
 
 void
@@ -4745,90 +4748,12 @@ GetMockAuthenticationNonce(void)
  * Are checksums enabled for data pages?
  */
 bool
-DataChecksumsNeedWrite(void)
+DataChecksumsEnabled(void)
 {
 	Assert(ControlFile != NULL);
 	return (ControlFile->data_checksum_version > 0);
 }
 
-bool
-DataChecksumsNeedVerify(void)
-{
-	Assert(ControlFile != NULL);
-
-	/*
-	 * Only verify checksums if they are fully enabled in the cluster. In
-	 * inprogress state they are only updated, not verified.
-	 */
-	return (ControlFile->data_checksum_version == PG_DATA_CHECKSUM_VERSION);
-}
-
-bool
-DataChecksumsInProgress(void)
-{
-	Assert(ControlFile != NULL);
-	return (ControlFile->data_checksum_version == PG_DATA_CHECKSUM_INPROGRESS_VERSION);
-}
-
-void
-SetDataChecksumsInProgress(void)
-{
-	Assert(ControlFile != NULL);
-	if (ControlFile->data_checksum_version > 0)
-		return;
-
-	XlogChecksums(PG_DATA_CHECKSUM_INPROGRESS_VERSION);
-
-	LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-	ControlFile->data_checksum_version = PG_DATA_CHECKSUM_INPROGRESS_VERSION;
-	UpdateControlFile();
-	LWLockRelease(ControlFileLock);
-}
-
-void
-SetDataChecksumsOn(void)
-{
-	Assert(ControlFile != NULL);
-
-	LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-
-	if (ControlFile->data_checksum_version != PG_DATA_CHECKSUM_INPROGRESS_VERSION)
-	{
-		LWLockRelease(ControlFileLock);
-		elog(ERROR, "Checksums not in inprogress mode");
-	}
-
-	ControlFile->data_checksum_version = PG_DATA_CHECKSUM_VERSION;
-	UpdateControlFile();
-	LWLockRelease(ControlFileLock);
-
-	XlogChecksums(PG_DATA_CHECKSUM_VERSION);
-}
-
-void
-SetDataChecksumsOff(void)
-{
-	LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-
-	ControlFile->data_checksum_version = 0;
-	UpdateControlFile();
-	LWLockRelease(ControlFileLock);
-
-	XlogChecksums(0);
-}
-
-/* guc hook */
-const char *
-show_data_checksums(void)
-{
-	if (ControlFile->data_checksum_version == PG_DATA_CHECKSUM_VERSION)
-		return "on";
-	else if (ControlFile->data_checksum_version == PG_DATA_CHECKSUM_INPROGRESS_VERSION)
-		return "inprogress";
-	else
-		return "off";
-}
-
 /*
  * Returns a fake LSN for unlogged relations.
  *
@@ -7863,16 +7788,6 @@ StartupXLOG(void)
 	 */
 	CompleteCommitTsInitialization();
 
-	/*
-	 * If we reach this point with checksums in inprogress state, we notify
-	 * the user that they need to manually restart the process to enable
-	 * checksums.
-	 */
-	if (ControlFile->data_checksum_version == PG_DATA_CHECKSUM_INPROGRESS_VERSION)
-		ereport(WARNING,
-				(errmsg("checksum state is \"inprogress\" with no worker"),
-				 errhint("Either disable or enable checksums by calling the pg_disable_data_checksums() or pg_enable_data_checksums() functions.")));
-
 	/*
 	 * All done with end-of-recovery actions.
 	 *
@@ -9626,22 +9541,6 @@ XLogReportParameters(void)
 	}
 }
 
-/*
- * Log the new state of checksums
- */
-static void
-XlogChecksums(ChecksumType new_type)
-{
-	xl_checksum_state xlrec;
-
-	xlrec.new_checksumtype = new_type;
-
-	XLogBeginInsert();
-	XLogRegisterData((char *) &xlrec, sizeof(xl_checksum_state));
-
-	XLogInsert(RM_XLOG_ID, XLOG_CHECKSUMS);
-}
-
 /*
  * Update full_page_writes in shared memory, and write an
  * XLOG_FPW_CHANGE record if necessary.
@@ -10070,17 +9969,6 @@ xlog_redo(XLogReaderState *record)
 		/* Keep track of full_page_writes */
 		lastFullPageWrites = fpw;
 	}
-	else if (info == XLOG_CHECKSUMS)
-	{
-		xl_checksum_state state;
-
-		memcpy(&state, XLogRecGetData(record), sizeof(xl_checksum_state));
-
-		LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
-		ControlFile->data_checksum_version = state.new_checksumtype;
-		UpdateControlFile();
-		LWLockRelease(ControlFileLock);
-	}
 }
 
 #ifdef WAL_DEBUG
-- 
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