v3-0004-Replace-pgwin32_is_junction-with-lstat.patch

From 4391644be135e15ffb052594c4ae54c4d83569df Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Thu, 28 Jul 2022 15:25:10 +1200
Subject: [PATCH v3 4/4] Replace pgwin32_is_junction() with lstat().

Now that lstat() reports junction points with S_IFLNK and unlink() can
unlink them, there is no need for separate code paths for Windows in a
few places.

The coding around pgwin32_is_junction() was a bit suspect anyway, as we
never checked for errors, and we also know that errors can be spuriously
reported because of transient sharing violations on this OS.  The
lstat()-based code tries to deal with that by retrying.

Discussion: https://postgr.es/m/CA%2BhUKGLfOOeyZpm5ByVcAt7x5Pn-%3DxGRNCvgiUPVVzjFLtnY0w%40mail.gmail.com
---
 src/backend/commands/tablespace.c    |  3 +--
 src/backend/replication/basebackup.c | 12 +-----------
 src/backend/storage/file/fd.c        |  5 -----
 src/backend/utils/adt/misc.c         |  7 -------
 src/bin/pg_checksums/pg_checksums.c  |  4 ----
 src/bin/pg_rewind/file_ops.c         |  4 ----
 src/common/file_utils.c              | 21 ---------------------
 src/include/port.h                   |  1 -
 src/include/port/win32_port.h        |  1 -
 src/port/dirmod.c                    | 16 ----------------
 10 files changed, 2 insertions(+), 72 deletions(-)

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 570ce3dbd5..dc0d7befd9 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -805,8 +805,7 @@ destroy_tablespace_directories(Oid tablespaceoid, bool redo)
 	/*
 	 * Try to remove the symlink.  We must however deal with the possibility
 	 * that it's a directory instead of a symlink --- this could happen during
-	 * WAL replay (see TablespaceCreateDbspace), and it is also the case on
-	 * Windows where junction points lstat() as directories.
+	 * WAL replay (see TablespaceCreateDbspace).
 	 *
 	 * Note: in the redo case, we'll return true if this final step fails;
 	 * there's no point in retrying it.  Also, ENOENT should provoke no more
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 7f85071229..a048cd5f31 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -1322,13 +1322,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
-		if (strcmp(path, "./pg_tblspc") == 0 &&
-#ifndef WIN32
-			S_ISLNK(statbuf.st_mode)
-#else
-			pgwin32_is_junction(pathbuf)
-#endif
-			)
+		if (strcmp(path, "./pg_tblspc") == 0 && S_ISLNK(statbuf.st_mode))
 		{
 #if defined(HAVE_READLINK) || defined(WIN32)
 			char		linkpath[MAXPGPATH];
@@ -1811,11 +1805,7 @@ static void
 convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
 {
 	/* If symlink, write it as a directory anyway */
-#ifndef WIN32
 	if (S_ISLNK(statbuf->st_mode))
-#else
-	if (pgwin32_is_junction(pathbuf))
-#endif
 		statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
 }
 
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index f904f60c08..566ebe26a0 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -3377,7 +3377,6 @@ SyncDataDirectory(void)
 	 */
 	xlog_is_symlink = false;
 
-#ifndef WIN32
 	{
 		struct stat st;
 
@@ -3389,10 +3388,6 @@ SyncDataDirectory(void)
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
-#else
-	if (pgwin32_is_junction("pg_wal"))
-		xlog_is_symlink = true;
-#endif
 
 #ifdef HAVE_SYNCFS
 	if (recovery_init_sync_method == RECOVERY_INIT_SYNC_METHOD_SYNCFS)
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 89690be2ed..412039ea6b 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -283,9 +283,7 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	char		sourcepath[MAXPGPATH];
 	char		targetpath[MAXPGPATH];
 	int			rllen;
-#ifndef WIN32
 	struct stat st;
-#endif
 
 	/*
 	 * It's useful to apply this function to pg_class.reltablespace, wherein
@@ -316,10 +314,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 	 * created with allow_in_place_tablespaces enabled.  If a directory is
 	 * found, a relative path to the data directory is returned.
 	 */
-#ifdef WIN32
-	if (!pgwin32_is_junction(sourcepath))
-		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#else
 	if (lstat(sourcepath, &st) < 0)
 	{
 		ereport(ERROR,
@@ -330,7 +324,6 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
 
 	if (!S_ISLNK(st.st_mode))
 		PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
-#endif
 
 	/*
 	 * In presence of a link or a junction point, return the path pointing to.
diff --git a/src/bin/pg_checksums/pg_checksums.c b/src/bin/pg_checksums/pg_checksums.c
index dc20122c89..324ccf7783 100644
--- a/src/bin/pg_checksums/pg_checksums.c
+++ b/src/bin/pg_checksums/pg_checksums.c
@@ -384,11 +384,7 @@ scan_directory(const char *basedir, const char *subdir, bool sizeonly)
 			if (!sizeonly)
 				scan_file(fn, segmentno);
 		}
-#ifndef WIN32
 		else if (S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode))
-#else
-		else if (S_ISDIR(st.st_mode) || pgwin32_is_junction(fn))
-#endif
 		{
 			/*
 			 * If going through the entries of pg_tblspc, we assume to operate
diff --git a/src/bin/pg_rewind/file_ops.c b/src/bin/pg_rewind/file_ops.c
index 6cb288f099..7d98283c79 100644
--- a/src/bin/pg_rewind/file_ops.c
+++ b/src/bin/pg_rewind/file_ops.c
@@ -431,11 +431,7 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/* recurse to handle subdirectories */
 			recurse_dir(datadir, path, callback);
 		}
-#ifndef WIN32
 		else if (S_ISLNK(fst.st_mode))
-#else
-		else if (pgwin32_is_junction(fullpath))
-#endif
 		{
 #if defined(HAVE_READLINK) || defined(WIN32)
 			char		link_target[MAXPGPATH];
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 966b987d64..71c232d983 100644
--- a/src/common/file_utils.c
+++ b/src/common/file_utils.c
@@ -79,7 +79,6 @@ fsync_pgdata(const char *pg_data,
 	 */
 	xlog_is_symlink = false;
 
-#ifndef WIN32
 	{
 		struct stat st;
 
@@ -88,10 +87,6 @@ fsync_pgdata(const char *pg_data,
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
-#else
-	if (pgwin32_is_junction(pg_wal))
-		xlog_is_symlink = true;
-#endif
 
 	/*
 	 * If possible, hint to the kernel that we're soon going to fsync the data
@@ -465,21 +460,5 @@ get_dirent_type(const char *path,
 #endif
 	}
 
-#if defined(WIN32) && !defined(_MSC_VER)
-
-	/*
-	 * If we're on native Windows (not Cygwin, which has its own POSIX
-	 * symlinks), but not using the MSVC compiler, then we're using a
-	 * readdir() emulation provided by the MinGW runtime that has no d_type.
-	 * Since the lstat() fallback code reports junction points as directories,
-	 * we need an extra system call to check if we should report them as
-	 * symlinks instead, following our convention.
-	 */
-	if (result == PGFILETYPE_DIR &&
-		!look_through_symlinks &&
-		pgwin32_is_junction(path))
-		result = PGFILETYPE_LNK;
-#endif
-
 	return result;
 }
diff --git a/src/include/port.h b/src/include/port.h
index d39b04141f..4b978f61bd 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -284,7 +284,6 @@ extern int	pgunlink(const char *path);
 #if defined(WIN32) && !defined(__CYGWIN__)
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index b8cf2e1480..72a0dd572e 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -238,7 +238,6 @@ int			setitimer(int which, const struct itimerval *value, struct itimerval *oval
  */
 extern int	pgsymlink(const char *oldpath, const char *newpath);
 extern int	pgreadlink(const char *path, char *buf, size_t size);
-extern bool pgwin32_is_junction(const char *path);
 
 #define symlink(oldpath, newpath)	pgsymlink(oldpath, newpath)
 #define readlink(path, buf, size)	pgreadlink(path, buf, size)
diff --git a/src/port/dirmod.c b/src/port/dirmod.c
index ea191e99c6..2818bfd2e9 100644
--- a/src/port/dirmod.c
+++ b/src/port/dirmod.c
@@ -362,20 +362,4 @@ pgreadlink(const char *path, char *buf, size_t size)
 	return r;
 }
 
-/*
- * Assumes the file exists, so will return false if it doesn't
- * (since a nonexistent file is not a junction)
- */
-bool
-pgwin32_is_junction(const char *path)
-{
-	DWORD		attr = GetFileAttributes(path);
-
-	if (attr == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return false;
-	}
-	return ((attr & FILE_ATTRIBUTE_REPARSE_POINT) == FILE_ATTRIBUTE_REPARSE_POINT);
-}
 #endif							/* defined(WIN32) && !defined(__CYGWIN__) */
-- 
2.37.1