Use pg_pwrite_zeros() in walmethods.c

This change impacts pg_receivewal and pg_basebackup, for the pre-padding
with zeros of all the new non-compressed WAL segments, so as the code is
more robust on partial writes.  This makes the code consistent with the
backend (XLogFileInitInternal) when wal_init_zeros is enabled for the
WAL segment initialization.

Author: Bharath Rupireddy
Reviewed-by: Nathan Bossart, Andres Freund, Thomas Munro, Michael
Paquier
Discussion: https://postgr.es/m/CALj2ACUq7nAb7=bJNbK3yYmp-SZhJcXFR_pLk8un6XgDzDF3OA@mail.gmail.com

diff --git a/src/bin/pg_basebackup/walmethods.c b/src/bin/pg_basebackup/walmethods.c
index bc2e83d02befa6d8c689fab27b30fee638a6e44c..3b06ef6269a0500ea083009a132214aa76efa962 100644 (file)
--- a/src/bin/pg_basebackup/walmethods.c
+++ b/src/bin/pg_basebackup/walmethods.c
@@ -220,22 +220,21 @@ dir_open_for_write(WalWriteMethod *wwmethod, const char *pathname,
    /* Do pre-padding on non-compressed files */
    if (pad_to_size && wwmethod->compression_algorithm == PG_COMPRESSION_NONE)
    {
-       PGAlignedXLogBlock zerobuf;
-       int         bytes;
+       ssize_t     rc;
 
-       memset(zerobuf.data, 0, XLOG_BLCKSZ);
-       for (bytes = 0; bytes < pad_to_size; bytes += XLOG_BLCKSZ)
+       rc = pg_pwrite_zeros(fd, pad_to_size);
+
+       if (rc < 0)
        {
-           errno = 0;
-           if (write(fd, zerobuf.data, XLOG_BLCKSZ) != XLOG_BLCKSZ)
-           {
-               /* If write didn't set errno, assume problem is no disk space */
-               wwmethod->lasterrno = errno ? errno : ENOSPC;
-               close(fd);
-               return NULL;
-           }
+           wwmethod->lasterrno = errno;
+           close(fd);
+           return NULL;
        }
 
+       /*
+        * pg_pwrite() (called via pg_pwrite_zeros()) may have moved the file
+        * position, so reset it (see win32pwrite.c).
+        */
        if (lseek(fd, 0, SEEK_SET) != 0)
        {
            wwmethod->lasterrno = errno;