2 files changed, 177 insertions, 6 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index b4fd8395b72..813b2afaac2 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -856,6 +856,7 @@ 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);
@@ -1033,7 +1034,7 @@ XLogInsertRecord(XLogRecData *rdata,
 		Assert(RedoRecPtr < Insert->RedoRecPtr);
 		RedoRecPtr = Insert->RedoRecPtr;
 	}
-	doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites);
+	doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites || DataChecksumsInProgress());
 
 	if (fpw_lsn != InvalidXLogRecPtr && fpw_lsn <= RedoRecPtr && doPageWrites)
 	{
@@ -4673,10 +4674,6 @@ 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
@@ -4748,12 +4745,90 @@ GetMockAuthenticationNonce(void)
  * Are checksums enabled for data pages?
  */
 bool
-DataChecksumsEnabled(void)
+DataChecksumsNeedWrite(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.
  *
@@ -7789,6 +7864,16 @@ 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.
 	 *
 	 * Now allow backends to write WAL and update the control file status in
@@ -9542,6 +9627,22 @@ 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.
  *
@@ -9969,6 +10070,17 @@ 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
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 316edbe3c58..b76b2688911 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -24,6 +24,7 @@
 #include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "postmaster/checksumhelper.h"
 #include "replication/walreceiver.h"
 #include "storage/smgr.h"
 #include "utils/builtins.h"
@@ -698,3 +699,61 @@ pg_backup_start_time(PG_FUNCTION_ARGS)
 
 	PG_RETURN_DATUM(xtime);
 }
+
+/*
+ * Disables checksums for the cluster, unless already disabled.
+ *
+ * Has immediate effect - the checksums are set to off right away.
+ */
+Datum
+disable_data_checksums(PG_FUNCTION_ARGS)
+{
+	/*
+	 * If we don't need to write new checksums, then clearly they are already
+	 * disabled.
+	 */
+	if (!DataChecksumsNeedWrite())
+		ereport(ERROR,
+				(errmsg("data checksums already disabled")));
+
+	ShutdownChecksumHelperIfRunning();
+
+	SetDataChecksumsOff();
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Enables checksums for the cluster, unless already enabled.
+ *
+ * Supports vacuum-like cost-based throttling, to limit system load.
+ * Starts a background worker that updates checksums on existing data.
+ */
+Datum
+enable_data_checksums(PG_FUNCTION_ARGS)
+{
+	int			cost_delay = PG_GETARG_INT32(0);
+	int			cost_limit = PG_GETARG_INT32(1);
+
+	if (cost_delay < 0)
+		ereport(ERROR,
+				(errmsg("cost delay cannot be less than zero")));
+	if (cost_limit <= 0)
+		ereport(ERROR,
+				(errmsg("cost limit must be a positive value")));
+
+	/*
+	 * Allow state change from "off" or from "inprogress", since this is how
+	 * we restart the worker if necessary.
+	 */
+	if (DataChecksumsNeedVerify())
+		ereport(ERROR,
+				(errmsg("data checksums already enabled")));
+
+	SetDataChecksumsInProgress();
+	if (!StartChecksumHelperLauncher(cost_delay, cost_limit))
+		ereport(ERROR,
+				(errmsg("failed to start checksum helper process")));
+
+	PG_RETURN_VOID();
+}