Fix for 3e8ac28, improve error messages.

We need call fflush() for buffered IO. Without fflush() fsync() could be useless.

Author: Arthur Zakirov

src/backup.c

@@ -1102,6 +1102,7 @@ pg_stop_backup(pgBackup *backup)
 		char		backup_label[MAXPGPATH];
 		FILE	   *fp;
 		pgFile	   *file;
+		size_t		len;
 
 		Assert(PQnfields(res) >= 5);
 
@@ -1114,9 +1115,13 @@ pg_stop_backup(pgBackup *backup)
 			elog(ERROR, "can't open backup label file \"%s\": %s",
 				 backup_label, strerror(errno));
 
-		fwrite(PQgetvalue(res, 0, 1), 1, strlen(PQgetvalue(res, 0, 1)), fp);
-		fsync(fileno(fp));
-		fclose(fp);
+		len = strlen(PQgetvalue(res, 0, 1));
+		if (fwrite(PQgetvalue(res, 0, 1), 1, len, fp) != len ||
+			fflush(fp) != 0 ||
+			fsync(fileno(fp)) != 0 ||
+			fclose(fp))
+			elog(ERROR, "can't write backup label file \"%s\": %s",
+				 backup_label, strerror(errno));
 
 		/*
 		 * It's vital to check if backup_files_list is initialized,
@@ -1142,9 +1147,13 @@ pg_stop_backup(pgBackup *backup)
 				elog(ERROR, "can't open tablespace map file \"%s\": %s",
 					 tablespace_map, strerror(errno));
 
-			fwrite(PQgetvalue(res, 0, 2), 1, strlen(PQgetvalue(res, 0, 2)), fp);
-			fsync(fileno(fp));
-			fclose(fp);
+			len = strlen(PQgetvalue(res, 0, 2));
+			if (fwrite(PQgetvalue(res, 0, 2), 1, len, fp) != len ||
+				fflush(fp) != 0 ||
+				fsync(fileno(fp)) != 0 ||
+				fclose(fp))
+				elog(ERROR, "can't write tablespace map file \"%s\": %s",
+					 tablespace_map, strerror(errno));
 
 			file = pgFileNew(tablespace_map, true);
 			calc_file_checksum(file);
@@ -1667,8 +1676,10 @@ write_backup_file_list(parray *files, const char *root)
 
 	print_file_list(fp, files, root);
 
-	fsync(fileno(fp));
-	fclose(fp);
+	if (fflush(fp) != 0 ||
+		fsync(fileno(fp)) != 0 ||
+		fclose(fp))
+		elog(ERROR, "cannot write file list \"%s\": %s", path, strerror(errno));
 }
 
 /*

src/data.c

@@ -357,9 +357,12 @@ backup_data_file(const char *from_root, const char *to_root,
 			 strerror(errno_tmp));
 	}
 
-	fsync(fileno(out));
+	if (fflush(out) != 0 ||
+		fsync(fileno(out)) != 0 ||
+		fclose(out))
+		elog(ERROR, "cannot write backup file \"%s\": %s",
+			 to_path, strerror(errno));
 	fclose(in);
-	fclose(out);
 
 	FIN_CRC32C(file->crc);
 
@@ -471,9 +474,11 @@ restore_file_partly(const char *from_root,const char *to_root, pgFile *file)
 			strerror(errno_tmp));
 	}
 
-	fsync(fileno(out));
+	if (fflush(out) != 0 ||
+		fsync(fileno(out)) != 0 ||
+		fclose(out))
+		elog(ERROR, "cannot write \"%s\": %s", to_path, strerror(errno));
 	fclose(in);
-	fclose(out);
 }
 
 void
@@ -607,9 +612,11 @@ restore_data_file(const char *from_root,
 			 strerror(errno_tmp));
 	}
 
-	fsync(fileno(out));
+	if (fflush(out) != 0 ||
+		fsync(fileno(out)) != 0 ||
+		fclose(out))
+		elog(ERROR, "cannot write \"%s\": %s", to_path, strerror(errno));
 	fclose(in);
-	fclose(out);
 }
 
 /*
@@ -735,9 +742,11 @@ copy_file(const char *from_root, const char *to_root, pgFile *file)
 			 strerror(errno_tmp));
 	}
 
-	fsync(fileno(out));
+	if (fflush(out) != 0 ||
+		fsync(fileno(out)) != 0 ||
+		fclose(out))
+		elog(ERROR, "cannot write \"%s\": %s", to_path, strerror(errno));
 	fclose(in);
-	fclose(out);
 
 	return true;
 }
@@ -836,9 +845,11 @@ copy_wal_file(const char *from_path, const char *to_path)
 			 strerror(errno_tmp));
 	}
 
-	fsync(fileno(out));
+	if (fflush(out) != 0 ||
+		fsync(fileno(out)) != 0 ||
+		fclose(out))
+		elog(ERROR, "cannot write \"%s\": %s", to_path, strerror(errno));
 	fclose(in);
-	fclose(out);
 }
 
 /*
@@ -961,9 +972,11 @@ copy_file_partly(const char *from_root, const char *to_root,
 	/* add meta information needed for recovery */
 	file->is_partial_copy = true;
 
-	fsync(fileno(out));
+	if (fflush(out) != 0 ||
+		fsync(fileno(out)) != 0 ||
+		fclose(out))
+		elog(ERROR, "cannot write \"%s\": %s", to_path, strerror(errno));
 	fclose(in);
-	fclose(out);
 
 	return true;
 }

src/restore.c

@@ -750,8 +750,11 @@ create_recovery_conf(time_t backup_id,
 	if (target_tli)
 		fprintf(fp, "recovery_target_timeline = '%u'\n", target_tli);
 
-	fsync(fileno(fp));
-	fclose(fp);
+	if (fflush(fp) != 0 ||
+		fsync(fileno(fp)) != 0 ||
+		fclose(fp))
+		elog(ERROR, "cannot write recovery.conf \"%s\": %s", path,
+			 strerror(errno));
 }
 
 /*