[PBCKP-150] review fixes

Author: Daniel Shelepanov

src/data.c

@@ -301,8 +301,9 @@ prepare_page(pgFile *file, XLogRecPtr prev_backup_start_lsn,
 	{
 		/* read the block */
 		int read_len = fio_pread(in, page, blknum * BLCKSZ);
-		/* avoid re-reading once buffered data, see PBCKP-150 */
-		fflush(in);
+		/* avoid re-reading once buffered data, flushing on further attempts, see PBCKP-150 */
+		if(try_again < PAGE_READ_ATTEMPTS - 1)
+			fio_fflush(in);
 
 		/* The block could have been truncated. It is fine. */
 		if (read_len == 0)