PGPRO-646: Set need_repair to false before SetLatch().

Otherwise next call of WalSndRequestRepairBlock() could fail because of RprBlockState->need_repair checking.

Author: za-arthur

src/backend/replication/walsender.c

@@ -2037,9 +2037,9 @@ ProcessStandbyRepairBlockMessage(void)
 
 	/* Send signal to backend that block is in shared memory */
 	RprBlockState->block_is_read = true;
+	RprBlockState->need_repair = false;
 	SetLatch(RprBlockState->backendLatch);
 
-	RprBlockState->need_repair = false;
 	/* Set flag that walsenders are ready to repair another block */
 	pg_atomic_clear_flag(&WalSndCtl->block_repair_flag);
 }
@@ -3647,7 +3647,7 @@ LagTrackerRead(int head, XLogRecPtr lsn, TimestampTz now)
  * Backend requests walsender to a repair block. Backend will wait for the
  * repair block from a walreceiver.
  */
-void
+bool
 WalSndRequestRepairBlock(RelFileNode rnode,
 						 ForkNumber forkNum, BlockNumber blockNum,
 						 XLogRecPtr wal_lsn, Latch *backendLatch)
@@ -3656,7 +3656,7 @@ WalSndRequestRepairBlock(RelFileNode rnode,
 	{
 		ereport(WARNING,
 				(errmsg("walsender reads a repair block already")));
-		return;
+		return false;
 	}
 
 	RprBlockState->rnode = rnode;
@@ -3673,6 +3673,8 @@ WalSndRequestRepairBlock(RelFileNode rnode,
 
 	RprBlockState->need_repair = true;
 	WalSndWakeup();
+
+	return true;
 }
 
 /*

src/backend/storage/buffer/block_repair.c

@@ -37,9 +37,10 @@ RepairCorruptedBlock(SMgrRelation smgr, ForkNumber forkNum,
 	currentLSN = GetXLogWriteRecPtr();
 	LWLockAcquire(RepairLockInfo->repair_lock, LW_EXCLUSIVE);
 
-	WalSndRequestRepairBlock(smgr->smgr_rnode.node,
-							 forkNum, blockNum, currentLSN,
-							 MyLatch);
+	if (!WalSndRequestRepairBlock(smgr->smgr_rnode.node,
+								  forkNum, blockNum, currentLSN,
+								  MyLatch))
+		return false;
 
 	elog(DEBUG1, "repairing block %u of tablespace %u, database %u, "
 		 "relation %u, fork %d, checkpoint %X/%X",

src/include/replication/walsender.h

@@ -55,7 +55,7 @@ extern void WalSndWaitStopping(void);
 extern void HandleWalSndInitStopping(void);
 extern void WalSndRqstFileReload(void);
 
-extern void WalSndRequestRepairBlock(RelFileNode rnode,
+extern bool WalSndRequestRepairBlock(RelFileNode rnode,
 									 ForkNumber forkNum, BlockNumber blockNum,
 									 XLogRecPtr wal_lsn,
 									 Latch *backendLatch);