diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 4e0756059e8..94fd721517b 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1237,12 +1237,17 @@ ReadTwoPhaseFile(TransactionId xid, bool give_warnings)
 	 */
 	if (fstat(fd, &stat))
 	{
+		int			save_errno = errno;
+
 		CloseTransientFile(fd);
 		if (give_warnings)
+		{
+			errno = save_errno;
 			ereport(WARNING,
 					(errcode_for_file_access(),
 					 errmsg("could not stat two-phase state file \"%s\": %m",
 							path)));
+		}
 		return NULL;
 	}
 
@@ -1269,12 +1274,17 @@ ReadTwoPhaseFile(TransactionId xid, bool give_warnings)
 
 	if (read(fd, buf, stat.st_size) != stat.st_size)
 	{
+		int			save_errno = errno;
+
 		CloseTransientFile(fd);
 		if (give_warnings)
+		{
+			errno = save_errno;
 			ereport(WARNING,
 					(errcode_for_file_access(),
 					 errmsg("could not read two-phase state file \"%s\": %m",
 							path)));
+		}
 		pfree(buf);
 		return NULL;
 	}
@@ -1562,14 +1572,24 @@ RecreateTwoPhaseFile(TransactionId xid, void *content, int len)
 	/* Write content and CRC */
 	if (write(fd, content, len) != len)
 	{
+		int			save_errno = errno;
+
 		CloseTransientFile(fd);
+
+		/* if write didn't set errno, assume problem is no disk space */
+		errno = save_errno ? save_errno : ENOSPC;
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not write two-phase state file: %m")));
 	}
 	if (write(fd, &statefile_crc, sizeof(pg_crc32)) != sizeof(pg_crc32))
 	{
+		int			save_errno = errno;
+
 		CloseTransientFile(fd);
+
+		/* if write didn't set errno, assume problem is no disk space */
+		errno = save_errno ? save_errno : ENOSPC;
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not write two-phase state file: %m")));
@@ -1581,7 +1601,10 @@ RecreateTwoPhaseFile(TransactionId xid, void *content, int len)
 	 */
 	if (pg_fsync(fd) != 0)
 	{
+		int			save_errno = errno;
+
 		CloseTransientFile(fd);
+		errno = save_errno;
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not fsync two-phase state file: %m")));
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 618d4273772..f788d70e5a3 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2364,7 +2364,10 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 
 	if (pg_fsync(fd) != 0)
 	{
+		int			save_errno = errno;
+
 		close(fd);
+		errno = save_errno;
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not fsync file \"%s\": %m", tmppath)));
@@ -9777,8 +9780,10 @@ retry:
 	if (lseek(readFile, (off_t) readOff, SEEK_SET) < 0)
 	{
 		char		fname[MAXFNAMELEN];
+		int			save_errno = errno;
 
 		XLogFileName(fname, curFileTLI, readSegNo);
+		errno = save_errno;
 		ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen),
 				(errcode_for_file_access(),
 				 errmsg("could not seek in log segment %s to offset %u: %m",
@@ -9789,8 +9794,10 @@ retry:
 	if (read(readFile, readBuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
 	{
 		char		fname[MAXFNAMELEN];
+		int			save_errno = errno;
 
 		XLogFileName(fname, curFileTLI, readSegNo);
+		errno = save_errno;
 		ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen),
 				(errcode_for_file_access(),
 				 errmsg("could not read from log segment %s, offset %u: %m",
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 587d7d61c2a..53a5bf6d41c 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -379,6 +379,8 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 			fp = AllocateFile(pathbuf, "rb");
 			if (fp == NULL)
 			{
+				int			save_errno = errno;
+
 				/*
 				 * Most likely reason for this is that the file was already
 				 * removed by a checkpoint, so check for that to get a better
@@ -386,6 +388,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 				 */
 				CheckXLogRemoved(segno, tli);
 
+				errno = save_errno;
 				ereport(ERROR,
 						(errcode_for_file_access(),
 						 errmsg("could not open file \"%s\": %m", pathbuf)));
diff --git a/src/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index 49ae0a598ce..3e12d63530e 100644
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -140,6 +140,9 @@ open_walfile(XLogRecPtr startpoint, uint32 timeline, char *basedir,
 	{
 		if (write(f, zerobuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
 		{
+			/* if write didn't set errno, assume problem is no disk space */
+			if (errno == 0)
+				errno = ENOSPC;
 			fprintf(stderr,
 					_("%s: could not pad transaction log file \"%s\": %s\n"),
 					progname, fn, strerror(errno));
@@ -382,7 +385,9 @@ writeTimeLineHistoryFile(char *basedir, TimeLineID tli, char *filename,
 		 */
 		close(fd);
 		unlink(tmppath);
-		errno = save_errno;
+
+		/* if write didn't set errno, assume problem is no disk space */
+		errno = save_errno ? save_errno : ENOSPC;
 
 		fprintf(stderr, _("%s: could not write timeline history file \"%s\": %s\n"),
 				progname, tmppath, strerror(errno));
@@ -391,7 +396,10 @@ writeTimeLineHistoryFile(char *basedir, TimeLineID tli, char *filename,
 
 	if (fsync(fd) != 0)
 	{
+		int			save_errno = errno;
+
 		close(fd);
+		errno = save_errno;
 		fprintf(stderr, _("%s: could not fsync file \"%s\": %s\n"),
 				progname, tmppath, strerror(errno));
 		return false;
@@ -1125,6 +1133,12 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
 						  copybuf + hdr_len + bytes_written,
 						  bytes_to_write) != bytes_to_write)
 				{
+					/*
+					 * If write didn't set errno, assume problem is no disk
+					 * space.
+					 */
+					if (errno == 0)
+						errno = ENOSPC;
 					fprintf(stderr,
 							_("%s: could not write %u bytes to WAL file \"%s\": %s\n"),
 							progname, bytes_to_write, current_walfile_name,