Reset properly errno before calling write()

6cb3372 enforces errno to ENOSPC when less bytes than what is expected
have been written when it is unset, though it forgot to properly reset
errno before doing a system call to write(), causing errno to
potentially come from a previous system call.

Reported-by: Tom Lane
Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/31797.1533326676@sss.pgh.pa.us

7 files changed, 10 insertions, 0 deletions

diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index dd03543b6b3..c8fa62daeb9 100644
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -1164,6 +1164,7 @@ heap_xlog_logical_rewrite(XLogReaderState *r)
 	len = xlrec->num_mappings * sizeof(LogicalRewriteMappingData);
 
 	/* write out tail end of mapping file (again) */
+	errno = 0;
 	if (write(fd, data, len) != len)
 	{
 		/* if write didn't set errno, assume problem is no disk space */
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index faf590b7709..25d1a0d7694 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1577,6 +1577,7 @@ RecreateTwoPhaseFile(TransactionId xid, void *content, int len)
 						path)));
 
 	/* Write content and CRC */
+	errno = 0;
 	if (write(fd, content, len) != len)
 	{
 		int			save_errno = errno;
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index 4ecd6a9eae0..94832a105bf 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -547,6 +547,7 @@ CheckPointReplicationOrigin(void)
 						tmppath)));
 
 	/* write magic */
+	errno = 0;
 	if ((write(tmpfd, &magic, sizeof(magic))) != sizeof(magic))
 	{
 		int			save_errno = errno;
@@ -590,6 +591,7 @@ CheckPointReplicationOrigin(void)
 		/* make sure we only write out a commit that's persistent */
 		XLogFlush(local_lsn);
 
+		errno = 0;
 		if ((write(tmpfd, &disk_state, sizeof(disk_state))) !=
 			sizeof(disk_state))
 		{
@@ -612,6 +614,7 @@ CheckPointReplicationOrigin(void)
 
 	/* write out the CRC */
 	FIN_CRC32C(crc);
+	errno = 0;
 	if ((write(tmpfd, &crc, sizeof(crc))) != sizeof(crc))
 	{
 		int			save_errno = errno;
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 3606e9ec7ff..b73ac5b9243 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2369,6 +2369,7 @@ ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 
 	ondisk->size = sz;
 
+	errno = 0;
 	if (write(fd, rb->outbuf, ondisk->size) != ondisk->size)
 	{
 		int save_errno = errno;
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 2c96fbd5067..7a06fe086f6 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1571,6 +1571,7 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 		ereport(ERROR,
 				(errmsg("could not open file \"%s\": %m", path)));
 
+	errno = 0;
 	if ((write(fd, ondisk, needed_length)) != needed_length)
 	{
 		int			save_errno = errno;
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index a5bc452d812..b42861d6259 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1028,6 +1028,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
 				SnapBuildOnDiskChecksummedSize);
 	FIN_CRC32C(cp.checksum);
 
+	errno = 0;
 	if ((write(fd, &cp, sizeof(cp))) != sizeof(cp))
 	{
 		int			save_errno = errno;
diff --git a/src/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index 71f3fb59b7c..fb70b204f79 100644
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -157,6 +157,7 @@ open_walfile(XLogRecPtr startpoint, uint32 timeline, char *basedir,
 	zerobuf = pg_malloc0(XLOG_BLCKSZ);
 	for (bytes = 0; bytes < XLogSegSize; bytes += XLOG_BLCKSZ)
 	{
+		errno = 0;
 		if (write(f, zerobuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
 		{
 			/* if write didn't set errno, assume problem is no disk space */
@@ -1217,6 +1218,7 @@ ProcessXLogDataMsg(PGconn *conn, char *copybuf, int len,
 			}
 		}
 
+		errno = 0;
 		if (write(walfile,
 				  copybuf + hdr_len + bytes_written,
 				  bytes_to_write) != bytes_to_write)