From b239f1be33ea0e54b8e661312df52af49c090882 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathandbossart@gmail.com>
Date: Tue, 26 Apr 2022 12:38:23 -0700
Subject: [PATCH v5 2/2] Remove durable_rename_excl().

A previous commit replaced all calls to this function with
durable_rename(), but the function itself was not removed in back-
branches since extensions may use it.  This change removes the
function from v16devel.

Do not back-patch.

Author: Nathan Bossart
Reviewed-by: Robert Haas, Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/20220418182336.GA2298576%40nathanxps13
---
 src/backend/storage/file/fd.c  | 63 ----------------------------------
 src/include/pg_config_manual.h |  7 ----
 src/include/storage/fd.h       |  1 -
 3 files changed, 71 deletions(-)

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 24704b6a02..f904f60c08 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -807,69 +807,6 @@ durable_unlink(const char *fname, int elevel)
 	return 0;
 }
 
-/*
- * durable_rename_excl -- rename a file in a durable manner.
- *
- * Similar to durable_rename(), except that this routine tries (but does not
- * guarantee) not to overwrite the target file.
- *
- * Note that a crash in an unfortunate moment can leave you with two links to
- * the target file.
- *
- * Log errors with the caller specified severity.
- *
- * On Windows, using a hard link followed by unlink() causes concurrency
- * issues, while a simple rename() does not cause that, so be careful when
- * changing the logic of this routine.
- *
- * Returns 0 if the operation succeeded, -1 otherwise. Note that errno is not
- * valid upon return.
- */
-int
-durable_rename_excl(const char *oldfile, const char *newfile, int elevel)
-{
-	/*
-	 * Ensure that, if we crash directly after the rename/link, a file with
-	 * valid contents is moved into place.
-	 */
-	if (fsync_fname_ext(oldfile, false, false, elevel) != 0)
-		return -1;
-
-#ifdef HAVE_WORKING_LINK
-	if (link(oldfile, newfile) < 0)
-	{
-		ereport(elevel,
-				(errcode_for_file_access(),
-				 errmsg("could not link file \"%s\" to \"%s\": %m",
-						oldfile, newfile)));
-		return -1;
-	}
-	unlink(oldfile);
-#else
-	if (rename(oldfile, newfile) < 0)
-	{
-		ereport(elevel,
-				(errcode_for_file_access(),
-				 errmsg("could not rename file \"%s\" to \"%s\": %m",
-						oldfile, newfile)));
-		return -1;
-	}
-#endif
-
-	/*
-	 * Make change persistent in case of an OS crash, both the new entry and
-	 * its parent directory need to be flushed.
-	 */
-	if (fsync_fname_ext(newfile, false, false, elevel) != 0)
-		return -1;
-
-	/* Same for parent directory */
-	if (fsync_parent_path(newfile, elevel) != 0)
-		return -1;
-
-	return 0;
-}
-
 /*
  * InitFileAccess --- initialize this module during backend startup
  *
diff --git a/src/include/pg_config_manual.h b/src/include/pg_config_manual.h
index 84ce5a4a5d..830804fdfb 100644
--- a/src/include/pg_config_manual.h
+++ b/src/include/pg_config_manual.h
@@ -163,13 +163,6 @@
 #define USE_BARRIER_SMGRRELEASE
 #endif
 
-/*
- * Define this if your operating system supports link()
- */
-#if !defined(WIN32) && !defined(__CYGWIN__)
-#define HAVE_WORKING_LINK 1
-#endif
-
 /*
  * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
  * posix_fadvise() kernel call.  Usually the automatic configure tests are
diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h
index 69549b000f..2b4a8e0ffe 100644
--- a/src/include/storage/fd.h
+++ b/src/include/storage/fd.h
@@ -187,7 +187,6 @@ extern void fsync_fname(const char *fname, bool isdir);
 extern int	fsync_fname_ext(const char *fname, bool isdir, bool ignore_perm, int elevel);
 extern int	durable_rename(const char *oldfile, const char *newfile, int loglevel);
 extern int	durable_unlink(const char *fname, int loglevel);
-extern int	durable_rename_excl(const char *oldfile, const char *newfile, int loglevel);
 extern void SyncDataDirectory(void);
 extern int	data_sync_elevel(int elevel);
 
-- 
2.25.1