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

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 3c732d8f8014a6c5f6d31933499adbd2711650bd..06a16d1fb7d73ddcb4f892452940627de7574ac0 100644 (file)
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1565,6 +1565,7 @@ 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/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index 3e12d63530e288764743dbd53645c3cbb24e66a4..b2891431eae000330a70dd6af6a3af3130d655b2 100644 (file)
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -138,6 +138,7 @@ 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 */
@@ -1129,6 +1130,7 @@ HandleCopyStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline,
                                        }
                                }
 
+                               errno = 0;
                                if (write(walfile,
                                                  copybuf + hdr_len + bytes_written,
                                                  bytes_to_write) != bytes_to_write)