From 40749357f24adf89dc79db9b34f5c053288489bb Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Date: Mon, 15 Jan 2024 15:57:53 +0900
Subject: [PATCH v31 1/3] Export wal_sync_method related functions

Export several functions related to wal_sync_method for use in
subsequent commits. Since PG_O_DIRECT cannot be used in those commits,
the new function XLogGetSyncBit() will mask PG_O_DIRECT.
---
 src/backend/access/transam/xlog.c | 73 +++++++++++++++++++++----------
 src/include/access/xlog.h         |  2 +
 2 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 478377c4a2..c5f51849ee 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8403,21 +8403,29 @@ assign_wal_sync_method(int new_wal_sync_method, void *extra)
 	}
 }
 
+/*
+ * Exported version of get_sync_bit()
+ *
+ * Do not expose PG_O_DIRECT for uses outside xlog.c.
+ */
+int
+XLogGetSyncBit(void)
+{
+	return get_sync_bit(wal_sync_method) & ~PG_O_DIRECT;
+}
+
 
 /*
- * Issue appropriate kind of fsync (if any) for an XLOG output file.
+ * Issue appropriate kind of fsync (if any) according to wal_sync_method.
  *
- * 'fd' is a file descriptor for the XLOG file to be fsync'd.
- * 'segno' is for error reporting purposes.
+ * 'fd' is a file descriptor for the file to be fsync'd.
  */
-void
-issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
+const char *
+XLogFsyncFile(int fd)
 {
-	char	   *msg = NULL;
+	const char *msg = NULL;
 	instr_time	start;
 
-	Assert(tli != 0);
-
 	/*
 	 * Quick exit if fsync is disabled or write() has already synced the WAL
 	 * file.
@@ -8425,7 +8433,7 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
 	if (!enableFsync ||
 		wal_sync_method == WAL_SYNC_METHOD_OPEN ||
 		wal_sync_method == WAL_SYNC_METHOD_OPEN_DSYNC)
-		return;
+		return NULL;
 
 	/* Measure I/O timing to sync the WAL file */
 	if (track_wal_io_timing)
@@ -8460,19 +8468,6 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
 			break;
 	}
 
-	/* PANIC if failed to fsync */
-	if (msg)
-	{
-		char		xlogfname[MAXFNAMELEN];
-		int			save_errno = errno;
-
-		XLogFileName(xlogfname, tli, segno, wal_segment_size);
-		errno = save_errno;
-		ereport(PANIC,
-				(errcode_for_file_access(),
-				 errmsg(msg, xlogfname)));
-	}
-
 	pgstat_report_wait_end();
 
 	/*
@@ -8486,7 +8481,39 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
 		INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_sync_time, end, start);
 	}
 
-	PendingWalStats.wal_sync++;
+	if (msg != NULL)
+		PendingWalStats.wal_sync++;
+
+	return msg;
+}
+
+/*
+ * Issue appropriate kind of fsync (if any) for an XLOG output file.
+ *
+ * 'fd' is a file descriptor for the XLOG file to be fsync'd.
+ * 'segno' is for error reporting purposes.
+ */
+void
+issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
+{
+	const char	*msg;
+	
+	Assert(tli != 0);
+
+	msg = XLogFsyncFile(fd);
+
+	/* PANIC if failed to fsync */
+	if (msg)
+	{
+		char		xlogfname[MAXFNAMELEN];
+		int			save_errno = errno;
+
+		XLogFileName(xlogfname, tli, segno, wal_segment_size);
+		errno = save_errno;
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg(msg, xlogfname)));
+	}
 }
 
 /*
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 301c5fa11f..2a0d65b537 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -217,6 +217,8 @@ extern void xlog_redo(struct XLogReaderState *record);
 extern void xlog_desc(StringInfo buf, struct XLogReaderState *record);
 extern const char *xlog_identify(uint8 info);
 
+extern int XLogGetSyncBit(void);
+extern const char *XLogFsyncFile(int fd);
 extern void issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli);
 
 extern bool RecoveryInProgress(void);
-- 
2.39.3