stat() vs ERROR_DELETE_PENDING, round N + 1

From 5990d14bb4f9a0ca83fd1b6c7c6e0a6a23786a0d Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 17:07:44 +1200
Subject: [PATCH] Fix Windows basebackup by renaming before unlinking.

Rename files before unlinking on Windows.  This solves a problem where
basebackup could fail because other backends have a file handle to a
deleted file, so stat() and open() fail with ERROR_ACCESS_DENIED.

Suggested by Kyotaro Horiguchi <horikyota.ntt@gmail.com>.

XXX This is only a rough sketch to try the idea out!

Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 src/backend/replication/basebackup.c |  7 +++++
 src/backend/storage/file/fd.c        | 38 +++++++++++++++++++++++++---
 src/backend/storage/smgr/md.c        |  6 ++---
 src/include/storage/fd.h             |  1 +
 4 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index e71d7406ed..7961a7041b 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -19,6 +19,7 @@
 #include "access/xlog_internal.h"	/* for pg_start/stop_backup */
 #include "catalog/pg_type.h"
 #include "common/file_perm.h"
+#include "common/string.h"
 #include "commands/progress.h"
 #include "lib/stringinfo.h"
 #include "libpq/libpq.h"
@@ -1268,6 +1269,12 @@ sendDir(const char *path, int basepathlen, bool sizeonly, List *tablespaces,
 					strlen(PG_TEMP_FILE_PREFIX)) == 0)
 			continue;
 
+#ifdef WIN32
+		/* Skip unlinked files */
+		if (pg_str_endswith(de->d_name, ".unlinked"))
+			continue;
+#endif
+
 		/*
 		 * Check if the postmaster has signaled us to exit, and abort with an
 		 * error in that case. The error handler further up will call
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 501652654e..43f24d4ceb 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -72,6 +72,7 @@
 
 #include "postgres.h"
 
+#include <common/string.h>
 #include <dirent.h>
 #include <sys/file.h>
 #include <sys/param.h>
@@ -683,6 +684,35 @@ pg_truncate(const char *path, off_t length)
 #endif
 }
 
+/*
+ * Unlink a file.  On Windows, rename to a temporary filename before unlinking
+ * so that "path" is available for new files immediately even if other backends
+ * hold descriptors to the one we unlink.
+ */
+int
+pg_unlink(const char *path)
+{
+#ifdef WIN32
+	for (;;)
+	{
+		char		tmp_path[MAXPGPATH];
+
+		snprintf(tmp_path, sizeof(tmp_path), "%s.%ld.unlinked", path, random());
+		if (!MoveFileEx(path, tmp_path, 0))
+		{
+			if (GetLastError() == ERROR_FILE_EXISTS)
+				continue;		/* try a new random number */
+			_dosmaperr(GetLastError());
+			return -1;
+		}
+
+		return unlink(tmp_path);
+	}
+#else
+	return unlink(path);
+#endif
+}
+
 /*
  * fsync_fname -- fsync a file or directory, handling errors properly
  *
@@ -3269,8 +3299,9 @@ CleanupTempFiles(bool isCommit, bool isProcExit)
  * postmaster session
  *
  * This should be called during postmaster startup.  It will forcibly
- * remove any leftover files created by OpenTemporaryFile and any leftover
- * temporary relation files created by mdcreate.
+ * remove any leftover files created by OpenTemporaryFile, any leftover
+ * temporary relation files created by mdcreate, and anything left
+ * behind by pg_unlink() on crash.
  *
  * During post-backend-crash restart cycle, this routine is called when
  * remove_temp_files_after_crash GUC is enabled. Multiple crashes while
@@ -3448,7 +3479,8 @@ RemovePgTempRelationFilesInDbspace(const char *dbspacedirname)
 
 	while ((de = ReadDirExtended(dbspace_dir, dbspacedirname, LOG)) != NULL)
 	{
-		if (!looks_like_temp_rel_name(de->d_name))
+		if (!looks_like_temp_rel_name(de->d_name) &&
+			!pg_str_endswith(de->d_name, ".unlinked"))
 			continue;
 
 		snprintf(rm_path, sizeof(rm_path), "%s/%s",
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 8592d47e95..d519855d59 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -374,7 +374,7 @@ mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
 		/* Next unlink the file, unless it was already found to be missing */
 		if (ret == 0 || errno != ENOENT)
 		{
-			ret = unlink(path);
+			ret = pg_unlink(path);
 			if (ret < 0 && errno != ENOENT)
 				ereport(WARNING,
 						(errcode_for_file_access(),
@@ -422,7 +422,7 @@ mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
 				register_forget_request(rnode, forkNum, segno);
 			}
 
-			if (unlink(segpath) < 0)
+			if (pg_unlink(segpath) < 0)
 			{
 				/* ENOENT is expected after the last segment... */
 				if (errno != ENOENT)
@@ -1753,7 +1753,7 @@ mdunlinkfiletag(const FileTag *ftag, char *path)
 	pfree(p);
 
 	/* Try to unlink the file. */
-	return unlink(path);
+	return pg_unlink(path);
 }
 
 /*
diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h
index 329c7eba9a..be38f6a979 100644
--- a/src/include/storage/fd.h
+++ b/src/include/storage/fd.h
@@ -189,6 +189,7 @@ extern ssize_t pg_pwritev_with_retry(int fd,
 									 int iovcnt,
 									 off_t offset);
 extern int	pg_truncate(const char *path, off_t length);
+extern int	pg_unlink(const char *path);
 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);
-- 
2.30.2

From 10768af742ccf3c7dcdc8373a7b7f693edff6b81 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 23:49:23 +1200
Subject: [PATCH] Handle STATUS_DELETE_PENDING on Windows.

1.  Update our open() wrapper to check for STATUS_DELETE_PENDING and
translate it to appropriate errors.

2.  Remove non-working code that intended to do the same thing in our
stat() wrapper, and build on top of open() instead.

XXX Work in progress, see TODO notes in the code

Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 src/include/port.h   |   1 +
 src/port/open.c      |  72 +++++++++++------
 src/port/win32stat.c | 180 ++++---------------------------------------
 3 files changed, 65 insertions(+), 188 deletions(-)

diff --git a/src/include/port.h b/src/include/port.h
index 82f63de325..88b2711121 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -290,6 +290,7 @@ extern bool rmtree(const char *path, bool rmtopdir);
  * passing of other special options.
  */
 #define		O_DIRECT	0x80000000
+#define		O_X_STAT	0x40000000
 extern int	pgwin32_open(const char *, int,...);
 extern FILE *pgwin32_fopen(const char *, const char *);
 #define		open(a,b,c) pgwin32_open(a,b,c)
diff --git a/src/port/open.c b/src/port/open.c
index 14c6debba9..de976fc7e3 100644
--- a/src/port/open.c
+++ b/src/port/open.c
@@ -23,6 +23,34 @@
 #include <assert.h>
 #include <sys/stat.h>
 
+#include <ntstatus.h>
+
+typedef NTSTATUS (__stdcall *RtlGetLastNtStatus_t)(void);
+
+static RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+static int
+initialize_ntdll(void)
+{
+	HMODULE module;
+
+	if (pg_RtlGetLastNtStatus)
+		return 0;
+	module = LoadLibraryEx("ntdll.dll", NULL, 0);
+	if (!module)
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+	pg_RtlGetLastNtStatus = (RtlGetLastNtStatus_t) (pg_funcptr_t)
+		GetProcAddress(module, "RtlGetLastNtStatus");
+	if (!pg_RtlGetLastNtStatus)
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+	return 0;
+}
 
 static int
 openFlagsToCreateFileFlags(int openFlags)
@@ -66,13 +94,18 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 	SECURITY_ATTRIBUTES sa;
 	int			loops = 0;
 
+	if (initialize_ntdll() < 0)
+		return -1;
+
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
 						 (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
 						 _O_SHORT_LIVED | O_DSYNC | O_DIRECT |
+						 O_X_STAT |
 						 (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
 #ifndef FRONTEND
-	Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
+	/* XXX When called by stat very early on, this fails! */
+	//Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
 #endif
 
 #ifdef FRONTEND
@@ -102,6 +135,7 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 						   &sa,
 						   openFlagsToCreateFileFlags(fileFlags),
 						   FILE_ATTRIBUTE_NORMAL |
+						   ((fileFlags & O_X_STAT) ? FILE_FLAG_BACKUP_SEMANTICS : 0) |
 						   ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
 						   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
 						   ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
@@ -140,32 +174,20 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 		/*
 		 * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
 		 * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
-		 * case we want to wait a bit and try again, giving up after 1 second
-		 * (since this condition should never persist very long).  However,
-		 * there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
-		 * so care is needed.  In particular that happens if we try to open a
-		 * directory, or of course if there's an actual file-permissions
-		 * problem.  To distinguish these cases, try a stat().  In the
-		 * delete-pending case, it will either also get STATUS_DELETE_PENDING,
-		 * or it will see the file as gone and fail with ENOENT.  In other
-		 * cases it will usually succeed.  The only somewhat-likely case where
-		 * this coding will uselessly wait is if there's a permissions problem
-		 * with a containing directory, which we hope will never happen in any
-		 * performance-critical code paths.
+		 * case, we'd better ask for the NT status too so we can translate it
+		 * to a more Unix-like error.
+		 *
+		 * If there's no O_CREAT flag, then we'll pretend the file is
+		 * invisible.  With O_CREAT, we have no choice but to report that
+		 * there's a file in the way (which wouldn't happen on Unix).
 		 */
-		if (err == ERROR_ACCESS_DENIED)
+		if (err == ERROR_ACCESS_DENIED &&
+			pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
 		{
-			if (loops < 10)
-			{
-				struct stat st;
-
-				if (stat(fileName, &st) != 0)
-				{
-					pg_usleep(100000);
-					loops++;
-					continue;
-				}
-			}
+			if (fileFlags & O_CREAT)
+				err = ERROR_FILE_EXISTS;
+			else
+				err = ERROR_FILE_NOT_FOUND;
 		}
 
 		_dosmaperr(err);
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 2ad8ee1359..efe5c3221c 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -18,53 +18,6 @@
 #include "c.h"
 #include <windows.h>
 
-/*
- * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
- * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
- * library.
- */
-#if _WIN32_WINNT < 0x0600
-#include <winternl.h>
-
-#if !defined(__MINGW32__) && !defined(__MINGW64__)
-/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
-typedef struct _FILE_STANDARD_INFORMATION
-{
-	LARGE_INTEGER AllocationSize;
-	LARGE_INTEGER EndOfFile;
-	ULONG		NumberOfLinks;
-	BOOLEAN		DeletePending;
-	BOOLEAN		Directory;
-} FILE_STANDARD_INFORMATION;
-#define FileStandardInformation 5
-#endif							/* !defined(__MINGW32__) &&
-								 * !defined(__MINGW64__) */
-
-typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
-			(IN HANDLE FileHandle,
-			 OUT PIO_STATUS_BLOCK IoStatusBlock,
-			 OUT PVOID FileInformation,
-			 IN ULONG Length,
-			 IN FILE_INFORMATION_CLASS FileInformationClass);
-
-static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;
-
-static HMODULE ntdll = NULL;
-
-/*
- * Load DLL file just once regardless of how many functions we load/call in it.
- */
-static void
-LoadNtdll(void)
-{
-	if (ntdll != NULL)
-		return;
-	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
-}
-
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-
 /*
  * Convert a FILETIME struct into a 64 bit time_t.
  */
@@ -161,125 +114,31 @@ fileinfo_to_stat(HANDLE hFile, struct stat *buf)
 int
 _pgstat64(const char *name, struct stat *buf)
 {
+	int			fd;
+	int			rc;
+	int			save_errno;
+
 	/*
-	 * We must use a handle so lstat() returns the information of the target
-	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
-	 * NtQueryInformationFile from Windows 2000 or
-	 * GetFileInformationByHandleEx from Server 2008 / Vista.
+	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We pass
+	 * in a special private flag to say that it's _pgstat64() calling, to
+	 * activate a mode that allows directories to be opened for limited
+	 * purposes.
+	 *
+	 * XXX Think about fd pressure, since we're opening an fd?
 	 */
-	SECURITY_ATTRIBUTES sa;
-	HANDLE		hFile;
-	int			ret;
-#if _WIN32_WINNT < 0x0600
-	IO_STATUS_BLOCK ioStatus;
-	FILE_STANDARD_INFORMATION standardInfo;
-#else
-	FILE_STANDARD_INFO standardInfo;
-#endif
-
-	if (name == NULL || buf == NULL)
-	{
-		errno = EINVAL;
-		return -1;
-	}
+	fd = pgwin32_open(name, O_RDONLY | O_X_STAT, 0);
 
-	/* fast not-exists check */
-	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
+	if (fd < 0)
 		return -1;
-	}
 
-	/* get a file handle as lightweight as we can */
-	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-	hFile = CreateFile(name,
-					   GENERIC_READ,
-					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-					   &sa,
-					   OPEN_EXISTING,
-					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
-						FILE_FLAG_OVERLAPPED),
-					   NULL);
-	if (hFile == INVALID_HANDLE_VALUE)
-	{
-		DWORD		err = GetLastError();
+	rc = _pgfstat64(fd, buf);
+	save_errno = errno;
 
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-
-	memset(&standardInfo, 0, sizeof(standardInfo));
-
-#if _WIN32_WINNT < 0x0600
-	if (_NtQueryInformationFile == NULL)
-	{
-		/* First time through: load ntdll.dll and find NtQueryInformationFile */
-		LoadNtdll();
-		if (ntdll == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-
-		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
-			GetProcAddress(ntdll, "NtQueryInformationFile");
-		if (_NtQueryInformationFile == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-	}
+	close(fd);
 
-	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
-											sizeof(standardInfo),
-											FileStandardInformation)))
-	{
-		DWORD		err = GetLastError();
+	errno = save_errno;
 
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#else
-	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
-									  sizeof(standardInfo)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-	if (standardInfo.DeletePending)
-	{
-		/*
-		 * File has been deleted, but is not gone from the filesystem yet.
-		 * This can happen when some process with FILE_SHARE_DELETE has it
-		 * open, and it will be fully removed once that handle is closed.
-		 * Meanwhile, we can't open it, so indicate that the file just doesn't
-		 * exist.
-		 */
-		CloseHandle(hFile);
-		errno = ENOENT;
-		return -1;
-	}
-
-	/* At last we can invoke fileinfo_to_stat */
-	ret = fileinfo_to_stat(hFile, buf);
-
-	CloseHandle(hFile);
-	return ret;
+	return rc;
 }
 
 /*
@@ -296,11 +155,6 @@ _pgfstat64(int fileno, struct stat *buf)
 		return -1;
 	}
 
-	/*
-	 * Since we already have a file handle there is no need to check for
-	 * ERROR_DELETE_PENDING.
-	 */
-
 	return fileinfo_to_stat(hFile, buf);
 }
 
-- 
2.30.2

From 123bac7edb71ef27748187132d0912e617da5b44 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 23:49:23 +1200
Subject: [PATCH v2] Check for STATUS_DELETE_PENDING on Windows.

1.  Update our open() wrapper to check for NT's STATUS_DELETE_PENDING
and translate it to appropriate errors.

2.  Remove non-working code that was trying to do something similar for
stat(), and just reuse the open() code.

XXX TODO: resolve order-of-operations problem: pgwin32_open_handle() is
caled by _pgstat64() before the Windows signal emulation is started up,
but it might call pg_usleep().

Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 configure                     |   6 ++
 configure.ac                  |   1 +
 src/include/port.h            |   1 +
 src/include/port/win32ntdll.h |  22 +++++
 src/port/open.c               | 101 +++++++++++----------
 src/port/win32ntdll.c         |  63 +++++++++++++
 src/port/win32stat.c          | 164 ++--------------------------------
 src/tools/msvc/Mkvcbuild.pm   |   3 +-
 8 files changed, 156 insertions(+), 205 deletions(-)
 create mode 100644 src/include/port/win32ntdll.h
 create mode 100644 src/port/win32ntdll.c

diff --git a/configure b/configure
index c550cacd5a..adfe03f3f2 100755
--- a/configure
+++ b/configure
@@ -16818,6 +16818,12 @@ esac
  ;;
 esac
 
+  case " $LIBOBJS " in
+  *" win32ntdll.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS win32ntdll.$ac_objext"
+ ;;
+esac
+
   case " $LIBOBJS " in
   *" win32security.$ac_objext "* ) ;;
   *) LIBOBJS="$LIBOBJS win32security.$ac_objext"
diff --git a/configure.ac b/configure.ac
index 2ee710102f..2819b91a8c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1922,6 +1922,7 @@ if test "$PORTNAME" = "win32"; then
   AC_LIBOBJ(system)
   AC_LIBOBJ(win32env)
   AC_LIBOBJ(win32error)
+  AC_LIBOBJ(win32ntdll)
   AC_LIBOBJ(win32security)
   AC_LIBOBJ(win32setlocale)
   AC_LIBOBJ(win32stat)
diff --git a/src/include/port.h b/src/include/port.h
index 82f63de325..ec64be429c 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -290,6 +290,7 @@ extern bool rmtree(const char *path, bool rmtopdir);
  * passing of other special options.
  */
 #define		O_DIRECT	0x80000000
+extern HANDLE pgwin32_open_handle(const char *, int, bool);
 extern int	pgwin32_open(const char *, int,...);
 extern FILE *pgwin32_fopen(const char *, const char *);
 #define		open(a,b,c) pgwin32_open(a,b,c)
diff --git a/src/include/port/win32ntdll.h b/src/include/port/win32ntdll.h
new file mode 100644
index 0000000000..76b2becf8b
--- /dev/null
+++ b/src/include/port/win32ntdll.h
@@ -0,0 +1,22 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32_ntdll.h
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/port/win32ntdll.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include <ntstatus.h>
+
+typedef NTSTATUS (__stdcall *RtlGetLastNtStatus_t)(void);
+
+extern RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+extern int initialize_ntdll(void);
diff --git a/src/port/open.c b/src/port/open.c
index 14c6debba9..8fddd45c57 100644
--- a/src/port/open.c
+++ b/src/port/open.c
@@ -19,6 +19,8 @@
 #include "postgres_fe.h"
 #endif
 
+#include "port/win32ntdll.h"
+
 #include <fcntl.h>
 #include <assert.h>
 #include <sys/stat.h>
@@ -56,37 +58,28 @@ openFlagsToCreateFileFlags(int openFlags)
 }
 
 /*
- *	 - file attribute setting, based on fileMode?
+ * Internal function used by pgwin32_open() and _pgstat64().  When
+ * backup_semantics is true, directories may be opened (for limited uses).  On
+ * failure, INVALID_HANDLE_VALUE is returned and errno is set.
  */
-int
-pgwin32_open(const char *fileName, int fileFlags,...)
+HANDLE
+pgwin32_open_handle(const char *fileName, int fileFlags, bool backup_semantics)
 {
-	int			fd;
-	HANDLE		h = INVALID_HANDLE_VALUE;
+	HANDLE		h;
 	SECURITY_ATTRIBUTES sa;
 	int			loops = 0;
 
+	if (initialize_ntdll() < 0)
+		return INVALID_HANDLE_VALUE;
+
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
 						 (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
 						 _O_SHORT_LIVED | O_DSYNC | O_DIRECT |
 						 (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
 #ifndef FRONTEND
-	Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
-#endif
-
-#ifdef FRONTEND
-
-	/*
-	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
-	 * fopen() can be used by frontends, having as side-effect to switch the
-	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
-	 * Caller may want to enforce the binary or text mode, but if nothing is
-	 * defined make sure that the default mode maps with what versions older
-	 * than 12 have been doing.
-	 */
-	if ((fileFlags & O_BINARY) == 0)
-		fileFlags |= O_TEXT;
+	/* XXX When called by stat very early on, this fails! */
+	//Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
 #endif
 
 	sa.nLength = sizeof(sa);
@@ -102,6 +95,7 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 						   &sa,
 						   openFlagsToCreateFileFlags(fileFlags),
 						   FILE_ATTRIBUTE_NORMAL |
+						   (backup_semantics ? FILE_FLAG_BACKUP_SEMANTICS : 0) |
 						   ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
 						   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
 						   ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
@@ -140,38 +134,55 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 		/*
 		 * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
 		 * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
-		 * case we want to wait a bit and try again, giving up after 1 second
-		 * (since this condition should never persist very long).  However,
-		 * there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
-		 * so care is needed.  In particular that happens if we try to open a
-		 * directory, or of course if there's an actual file-permissions
-		 * problem.  To distinguish these cases, try a stat().  In the
-		 * delete-pending case, it will either also get STATUS_DELETE_PENDING,
-		 * or it will see the file as gone and fail with ENOENT.  In other
-		 * cases it will usually succeed.  The only somewhat-likely case where
-		 * this coding will uselessly wait is if there's a permissions problem
-		 * with a containing directory, which we hope will never happen in any
-		 * performance-critical code paths.
+		 * case, we'd better ask for the NT status too so we can translate it
+		 * to a more Unix-like error.  We hope that nothing clobbers the NT
+		 * status in between the internal NtCreateFile() call and CreateFile()
+		 * returning.
+		 *
+		 * If there's no O_CREAT flag, then we'll pretend the file is
+		 * invisible.  With O_CREAT, we have no choice but to report that
+		 * there's a file in the way (which wouldn't happen on Unix).
 		 */
-		if (err == ERROR_ACCESS_DENIED)
+		if (err == ERROR_ACCESS_DENIED &&
+			pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
 		{
-			if (loops < 10)
-			{
-				struct stat st;
-
-				if (stat(fileName, &st) != 0)
-				{
-					pg_usleep(100000);
-					loops++;
-					continue;
-				}
-			}
+			if (fileFlags & O_CREAT)
+				err = ERROR_FILE_EXISTS;
+			else
+				err = ERROR_FILE_NOT_FOUND;
 		}
 
 		_dosmaperr(err);
-		return -1;
+		return INVALID_HANDLE_VALUE;
 	}
 
+	return h;
+}
+
+int
+pgwin32_open(const char *fileName, int fileFlags,...)
+{
+	HANDLE h;
+	int fd;
+
+	h = pgwin32_open_handle(fileName, fileFlags, false);
+	if (h == INVALID_HANDLE_VALUE)
+		return -1;
+
+#ifdef FRONTEND
+
+	/*
+	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
+	 * fopen() can be used by frontends, having as side-effect to switch the
+	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
+	 * Caller may want to enforce the binary or text mode, but if nothing is
+	 * defined make sure that the default mode maps with what versions older
+	 * than 12 have been doing.
+	 */
+	if ((fileFlags & O_BINARY) == 0)
+		fileFlags |= O_TEXT;
+#endif
+
 	/* _open_osfhandle will, on error, set errno accordingly */
 	if ((fd = _open_osfhandle((intptr_t) h, fileFlags & O_APPEND)) < 0)
 		CloseHandle(h);			/* will not affect errno */
diff --git a/src/port/win32ntdll.c b/src/port/win32ntdll.c
new file mode 100644
index 0000000000..eaadafbe9a
--- /dev/null
+++ b/src/port/win32ntdll.c
@@ -0,0 +1,63 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.c
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/win32ntdll.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include "port/win32ntdll.h"
+
+RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+int
+initialize_ntdll(void)
+{
+	static bool initialized;
+	HMODULE module;
+
+	static const struct {
+		const char *name;
+		pg_funcptr_t *address;
+	} routines[] = {
+		{"RtlGetLastNtStatus", (pg_funcptr_t *) &pg_RtlGetLastNtStatus}
+	};
+
+	if (initialized)
+		return 0;
+
+	if (!(module = LoadLibraryEx("ntdll.dll", NULL, 0)))
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+
+	for (int i = 0; i < lengthof(routines); ++i)
+	{
+		pg_funcptr_t	address;
+
+		address = (pg_funcptr_t) GetProcAddress(module, routines[i].name);
+		if (!address)
+		{
+			_dosmaperr(GetLastError());
+			FreeLibrary(module);
+
+			return -1;
+		}
+
+		*(pg_funcptr_t *) routines[i].address = address;
+	}
+
+	initialized = true;
+
+	return 0;
+}
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 2ad8ee1359..c851400dc8 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -18,53 +18,6 @@
 #include "c.h"
 #include <windows.h>
 
-/*
- * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
- * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
- * library.
- */
-#if _WIN32_WINNT < 0x0600
-#include <winternl.h>
-
-#if !defined(__MINGW32__) && !defined(__MINGW64__)
-/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
-typedef struct _FILE_STANDARD_INFORMATION
-{
-	LARGE_INTEGER AllocationSize;
-	LARGE_INTEGER EndOfFile;
-	ULONG		NumberOfLinks;
-	BOOLEAN		DeletePending;
-	BOOLEAN		Directory;
-} FILE_STANDARD_INFORMATION;
-#define FileStandardInformation 5
-#endif							/* !defined(__MINGW32__) &&
-								 * !defined(__MINGW64__) */
-
-typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
-			(IN HANDLE FileHandle,
-			 OUT PIO_STATUS_BLOCK IoStatusBlock,
-			 OUT PVOID FileInformation,
-			 IN ULONG Length,
-			 IN FILE_INFORMATION_CLASS FileInformationClass);
-
-static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;
-
-static HMODULE ntdll = NULL;
-
-/*
- * Load DLL file just once regardless of how many functions we load/call in it.
- */
-static void
-LoadNtdll(void)
-{
-	if (ntdll != NULL)
-		return;
-	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
-}
-
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-
 /*
  * Convert a FILETIME struct into a 64 bit time_t.
  */
@@ -162,120 +115,18 @@ int
 _pgstat64(const char *name, struct stat *buf)
 {
 	/*
-	 * We must use a handle so lstat() returns the information of the target
-	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
-	 * NtQueryInformationFile from Windows 2000 or
-	 * GetFileInformationByHandleEx from Server 2008 / Vista.
+	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
+	 * request FILE_FLAG_BACKUP_SEMANTICS so that we can open directories too,
+	 * for limited purposes.  We use the private handle-based version, so we
+	 * don't risk running out of fds.
 	 */
-	SECURITY_ATTRIBUTES sa;
 	HANDLE		hFile;
 	int			ret;
-#if _WIN32_WINNT < 0x0600
-	IO_STATUS_BLOCK ioStatus;
-	FILE_STANDARD_INFORMATION standardInfo;
-#else
-	FILE_STANDARD_INFO standardInfo;
-#endif
-
-	if (name == NULL || buf == NULL)
-	{
-		errno = EINVAL;
-		return -1;
-	}
 
-	/* fast not-exists check */
-	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return -1;
-	}
-
-	/* get a file handle as lightweight as we can */
-	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-	hFile = CreateFile(name,
-					   GENERIC_READ,
-					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-					   &sa,
-					   OPEN_EXISTING,
-					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
-						FILE_FLAG_OVERLAPPED),
-					   NULL);
+	hFile = pgwin32_open_handle(name, O_RDONLY, true);
 	if (hFile == INVALID_HANDLE_VALUE)
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
 		return -1;
-	}
-
-	memset(&standardInfo, 0, sizeof(standardInfo));
-
-#if _WIN32_WINNT < 0x0600
-	if (_NtQueryInformationFile == NULL)
-	{
-		/* First time through: load ntdll.dll and find NtQueryInformationFile */
-		LoadNtdll();
-		if (ntdll == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-
-		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
-			GetProcAddress(ntdll, "NtQueryInformationFile");
-		if (_NtQueryInformationFile == NULL)
-		{
-			DWORD		err = GetLastError();
 
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-	}
-
-	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
-											sizeof(standardInfo),
-											FileStandardInformation)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#else
-	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
-									  sizeof(standardInfo)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-	if (standardInfo.DeletePending)
-	{
-		/*
-		 * File has been deleted, but is not gone from the filesystem yet.
-		 * This can happen when some process with FILE_SHARE_DELETE has it
-		 * open, and it will be fully removed once that handle is closed.
-		 * Meanwhile, we can't open it, so indicate that the file just doesn't
-		 * exist.
-		 */
-		CloseHandle(hFile);
-		errno = ENOENT;
-		return -1;
-	}
-
-	/* At last we can invoke fileinfo_to_stat */
 	ret = fileinfo_to_stat(hFile, buf);
 
 	CloseHandle(hFile);
@@ -296,11 +147,6 @@ _pgfstat64(int fileno, struct stat *buf)
 		return -1;
 	}
 
-	/*
-	 * Since we already have a file handle there is no need to check for
-	 * ERROR_DELETE_PENDING.
-	 */
-
 	return fileinfo_to_stat(hFile, buf);
 }
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 84f15f7e85..bebb0578dc 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -107,7 +107,8 @@ sub mkvcbuild
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
 	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c bsearch_arg.c quotes.c system.c
 	  strerror.c tar.c thread.c
-	  win32env.c win32error.c win32security.c win32setlocale.c win32stat.c);
+	  win32env.c win32error.c win32ntdll.c
+	  win32security.c win32setlocale.c win32stat.c);
 
 	push(@pgportfiles, 'strtof.c') if ($vsVersion < '14.00');
 
-- 
2.30.2

From 4959e4dc6d96d7634ec5ac0c8f55f11ec37b6adb Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 23:49:23 +1200
Subject: [PATCH] Use NtCreateFile() to open files on Windows.

1.  Update our open() wrapper to bypass Win32 and use NT interfaces to
open files.  This allows us to check for NT's STATUS_DELETE_PENDING and
translate it to appropriate errors.

2.  Remove non-working code from our stat() wrapper that tried to handle
the same problem, and reuse the open() wrapper.

XXX TODO: resolve order-of-operations problem: pgwin32_open_handle() is
caled by _pgstat64() before the Windows signal emulation is started up,
but it might call pg_usleep().

XXX TODO: there are some macro redefinition warnings from MSVC on CI;
apparently we need some well placed #define and #undef of
WIN32_NO_STATUS.

Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 configure                     |   6 +
 configure.ac                  |   1 +
 src/include/port.h            |   1 +
 src/include/port/win32ntdll.h |  42 ++++++
 src/port/open.c               | 255 ++++++++++++++++++++--------------
 src/port/win32ntdll.c         |  68 +++++++++
 src/port/win32stat.c          | 164 +---------------------
 src/tools/msvc/Mkvcbuild.pm   |   3 +-
 8 files changed, 276 insertions(+), 264 deletions(-)
 create mode 100644 src/include/port/win32ntdll.h
 create mode 100644 src/port/win32ntdll.c

diff --git a/configure b/configure
index c550cacd5a..adfe03f3f2 100755
--- a/configure
+++ b/configure
@@ -16818,6 +16818,12 @@ esac
  ;;
 esac
 
+  case " $LIBOBJS " in
+  *" win32ntdll.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS win32ntdll.$ac_objext"
+ ;;
+esac
+
   case " $LIBOBJS " in
   *" win32security.$ac_objext "* ) ;;
   *) LIBOBJS="$LIBOBJS win32security.$ac_objext"
diff --git a/configure.ac b/configure.ac
index 2ee710102f..2819b91a8c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1922,6 +1922,7 @@ if test "$PORTNAME" = "win32"; then
   AC_LIBOBJ(system)
   AC_LIBOBJ(win32env)
   AC_LIBOBJ(win32error)
+  AC_LIBOBJ(win32ntdll)
   AC_LIBOBJ(win32security)
   AC_LIBOBJ(win32setlocale)
   AC_LIBOBJ(win32stat)
diff --git a/src/include/port.h b/src/include/port.h
index 82f63de325..ec64be429c 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -290,6 +290,7 @@ extern bool rmtree(const char *path, bool rmtopdir);
  * passing of other special options.
  */
 #define		O_DIRECT	0x80000000
+extern HANDLE pgwin32_open_handle(const char *, int, bool);
 extern int	pgwin32_open(const char *, int,...);
 extern FILE *pgwin32_fopen(const char *, const char *);
 #define		open(a,b,c) pgwin32_open(a,b,c)
diff --git a/src/include/port/win32ntdll.h b/src/include/port/win32ntdll.h
new file mode 100644
index 0000000000..14e70c6f42
--- /dev/null
+++ b/src/include/port/win32ntdll.h
@@ -0,0 +1,42 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32_ntdll.h
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/port/win32ntdll.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include <ntstatus.h>
+#include <winternl.h>
+
+typedef NTSTATUS (__stdcall *NtCreateFile_t)(PHANDLE FileHandle,
+											 ACCESS_MASK DesiredAccess,
+											 POBJECT_ATTRIBUTES ObjectAttributes,
+											 PIO_STATUS_BLOCK IoStatusBlock,
+											 PLARGE_INTEGER AllocationSize,
+											 ULONG FileAttributes,
+											 ULONG ShareAccess,
+											 ULONG CreateDisposition,
+											 ULONG CreateOptions,
+											 PVOID EaBuffer,
+											 ULONG EaLength);
+
+typedef BOOLEAN (__stdcall *RtlDosPathNameToNtPathName_U_t)(PCWSTR DosName,
+															PUNICODE_STRING NtName,
+															PCWSTR *PartName,
+															void *RelativeName);
+
+typedef ULONG (__stdcall *RtlNtStatusToDosError_t)(NTSTATUS Status);
+
+extern NtCreateFile_t pg_NtCreateFile;
+extern RtlDosPathNameToNtPathName_U_t pg_RtlDosPathNameToNtPathName_U;
+extern RtlNtStatusToDosError_t pg_RtlNtStatusToDosError;
+
+extern int initialize_ntdll(void);
diff --git a/src/port/open.c b/src/port/open.c
index 14c6debba9..122e1b4ab7 100644
--- a/src/port/open.c
+++ b/src/port/open.c
@@ -19,52 +19,38 @@
 #include "postgres_fe.h"
 #endif
 
+#include "port/win32ntdll.h"
+
 #include <fcntl.h>
 #include <assert.h>
 #include <sys/stat.h>
 
-
-static int
-openFlagsToCreateFileFlags(int openFlags)
-{
-	switch (openFlags & (O_CREAT | O_TRUNC | O_EXCL))
-	{
-			/* O_EXCL is meaningless without O_CREAT */
-		case 0:
-		case O_EXCL:
-			return OPEN_EXISTING;
-
-		case O_CREAT:
-			return OPEN_ALWAYS;
-
-			/* O_EXCL is meaningless without O_CREAT */
-		case O_TRUNC:
-		case O_TRUNC | O_EXCL:
-			return TRUNCATE_EXISTING;
-
-		case O_CREAT | O_TRUNC:
-			return CREATE_ALWAYS;
-
-			/* O_TRUNC is meaningless with O_CREAT */
-		case O_CREAT | O_EXCL:
-		case O_CREAT | O_TRUNC | O_EXCL:
-			return CREATE_NEW;
-	}
-
-	/* will never get here */
-	return 0;
-}
-
 /*
- *	 - file attribute setting, based on fileMode?
+ * Internal function used by pgwin32_open() and _pgstat64().  When
+ * backup_semantics is true, directories may be opened (for limited uses).  On
+ * failure, INVALID_HANDLE_VALUE is returned and errno is set.
  */
-int
-pgwin32_open(const char *fileName, int fileFlags,...)
+HANDLE
+pgwin32_open_handle(const char *fileName, int fileFlags, bool backup_semantics)
 {
-	int			fd;
 	HANDLE		h = INVALID_HANDLE_VALUE;
-	SECURITY_ATTRIBUTES sa;
 	int			loops = 0;
+	wchar_t		wideFileName[MAX_PATH];
+	size_t		wideFileNameSize;
+	wchar_t		buffer[MAX_PATH];
+	UNICODE_STRING ntFileName;
+	ACCESS_MASK	desiredAccess;
+	OBJECT_ATTRIBUTES objectAttributes;
+	IO_STATUS_BLOCK ioStatusBlock;
+	ULONG		fileAttributes;
+	ULONG		shareAccess;
+	ULONG		createDisposition;
+	ULONG		createOptions;
+	NTSTATUS	status;
+	DWORD		err;
+
+	if (initialize_ntdll() < 0)
+		return INVALID_HANDLE_VALUE;
 
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
@@ -72,51 +58,116 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 						 _O_SHORT_LIVED | O_DSYNC | O_DIRECT |
 						 (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
 #ifndef FRONTEND
-	Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
+	/* XXX When called by stat very early on, this fails! */
+	//Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
 #endif
 
-#ifdef FRONTEND
+	/* Convert char string to wchar_t string. */
+	wideFileNameSize = MultiByteToWideChar(CP_ACP, 0, fileName, -1,
+										   wideFileName,
+										   lengthof(wideFileName));
+	if (wideFileNameSize == 0)
+	{
+		_dosmaperr(GetLastError());
+		return INVALID_HANDLE_VALUE;
+	}
 
-	/*
-	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
-	 * fopen() can be used by frontends, having as side-effect to switch the
-	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
-	 * Caller may want to enforce the binary or text mode, but if nothing is
-	 * defined make sure that the default mode maps with what versions older
-	 * than 12 have been doing.
-	 */
-	if ((fileFlags & O_BINARY) == 0)
-		fileFlags |= O_TEXT;
-#endif
+	/* Convert DOS/Win32 path to fully qualified NT path. */
+	ntFileName.Length = 0;
+	ntFileName.MaximumLength = sizeof(buffer);
+	ntFileName.Buffer = buffer;
+	if (!pg_RtlDosPathNameToNtPathName_U(wideFileName,
+										 &ntFileName,
+										 NULL,
+										 NULL))
+	{
+		/* XXX does GetLastError() work for this function?  need the
+		 * _WithStatus version maybe? */
+		_dosmaperr(GetLastError());
+		return INVALID_HANDLE_VALUE;
+	}
 
-	sa.nLength = sizeof(sa);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-
-	while ((h = CreateFile(fileName,
-	/* cannot use O_RDONLY, as it == 0 */
-						   (fileFlags & O_RDWR) ? (GENERIC_WRITE | GENERIC_READ) :
-						   ((fileFlags & O_WRONLY) ? GENERIC_WRITE : GENERIC_READ),
-	/* These flags allow concurrent rename/unlink */
-						   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-						   &sa,
-						   openFlagsToCreateFileFlags(fileFlags),
-						   FILE_ATTRIBUTE_NORMAL |
-						   ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
-						   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
-						   ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
-						   ((fileFlags & O_TEMPORARY) ? FILE_FLAG_DELETE_ON_CLOSE : 0) |
-						   ((fileFlags & O_DIRECT) ? FILE_FLAG_NO_BUFFERING : 0) |
-						   ((fileFlags & O_DSYNC) ? FILE_FLAG_WRITE_THROUGH : 0),
-						   NULL)) == INVALID_HANDLE_VALUE)
+	/* Convert other parameters. */
+	desiredAccess =
+		FILE_READ_ATTRIBUTES |		/* allow fstat() even if O_WRONLY */
+		((fileFlags & O_TEMPORARY) ? DELETE : 0) |
+		((fileFlags & O_RDWR) ? FILE_GENERIC_WRITE | FILE_GENERIC_READ :
+		 (fileFlags & O_WRONLY) ? FILE_GENERIC_WRITE : FILE_GENERIC_READ);
+	shareAccess = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
+	InitializeObjectAttributes(&objectAttributes, &ntFileName,
+							   OBJ_CASE_INSENSITIVE | OBJ_INHERIT, NULL, NULL);
+	fileAttributes =
+		((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0);
+	if (fileAttributes == 0)
+		fileAttributes = FILE_ATTRIBUTE_NORMAL;
+	if (fileFlags & O_CREAT)
 	{
+		if (fileFlags & O_EXCL)
+			createDisposition = FILE_CREATE;
+		else if (fileFlags & O_TRUNC)
+			createDisposition = FILE_OVERWRITE_IF;
+		else
+			createDisposition = FILE_OPEN_IF;
+	}
+	else if (fileFlags & O_TRUNC)
+		createDisposition = FILE_OVERWRITE;
+	else
+		createDisposition = FILE_OPEN;
+	createOptions =
+		FILE_SYNCHRONOUS_IO_NONALERT |
+		(backup_semantics ? FILE_OPEN_FOR_BACKUP_INTENT : 0) |
+		((fileFlags & O_RANDOM) ? FILE_RANDOM_ACCESS : 0) |
+		((fileFlags & O_SEQUENTIAL) ? FILE_SEQUENTIAL_ONLY : 0) |
+		((fileFlags & O_DIRECT) ? FILE_NO_INTERMEDIATE_BUFFERING : 0) |
+		((fileFlags & O_DSYNC) ? FILE_WRITE_THROUGH : 0) |
+		((fileFlags & O_TEMPORARY) ? FILE_DELETE_ON_CLOSE : 0);
+
+	for (;;)
+	{
+		status = pg_NtCreateFile(&h,
+								 desiredAccess,
+								 &objectAttributes,
+								 &ioStatusBlock,
+								 NULL,
+								 fileAttributes,
+								 shareAccess,
+								 createDisposition,
+								 createOptions,
+								 NULL,
+								 0);
+
+		if (NT_SUCCESS(status))
+			break;
+
+		/*
+		 * Translate STATUS_DELETE_PENDING to a more Unix-like error.
+		 *
+		 * If there's no O_CREAT flag, then we'll pretend the file is
+		 * invisible.  With O_CREAT, we have no choice but to report that
+		 * there's a file in the way (which wouldn't happen on Unix).
+		 */
+		if (status == STATUS_DELETE_PENDING)
+		{
+			if (fileFlags & O_CREAT)
+				err = ERROR_FILE_EXISTS;
+			else
+				err = ERROR_FILE_NOT_FOUND;
+			_dosmaperr(err);
+			return INVALID_HANDLE_VALUE;
+		}
+
+		/*
+		 * For everything else, convert the NT error into a DOS error.  This
+		 * is where STATUS_DELETE_PENDING would normally be mapped to
+		 * ERROR_ACCESS_DENIED, and lost to us.
+		 */
+		err = pg_RtlNtStatusToDosError(status);
+
 		/*
 		 * Sharing violation or locking error can indicate antivirus, backup
 		 * or similar software that's locking the file.  Wait a bit and try
 		 * again, giving up after 30 seconds.
 		 */
-		DWORD		err = GetLastError();
-
 		if (err == ERROR_SHARING_VIOLATION ||
 			err == ERROR_LOCK_VIOLATION)
 		{
@@ -137,41 +188,37 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 			}
 		}
 
-		/*
-		 * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
-		 * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
-		 * case we want to wait a bit and try again, giving up after 1 second
-		 * (since this condition should never persist very long).  However,
-		 * there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
-		 * so care is needed.  In particular that happens if we try to open a
-		 * directory, or of course if there's an actual file-permissions
-		 * problem.  To distinguish these cases, try a stat().  In the
-		 * delete-pending case, it will either also get STATUS_DELETE_PENDING,
-		 * or it will see the file as gone and fail with ENOENT.  In other
-		 * cases it will usually succeed.  The only somewhat-likely case where
-		 * this coding will uselessly wait is if there's a permissions problem
-		 * with a containing directory, which we hope will never happen in any
-		 * performance-critical code paths.
-		 */
-		if (err == ERROR_ACCESS_DENIED)
-		{
-			if (loops < 10)
-			{
-				struct stat st;
-
-				if (stat(fileName, &st) != 0)
-				{
-					pg_usleep(100000);
-					loops++;
-					continue;
-				}
-			}
-		}
-
 		_dosmaperr(err);
-		return -1;
+		return INVALID_HANDLE_VALUE;
 	}
 
+	return h;
+}
+
+int
+pgwin32_open(const char *fileName, int fileFlags,...)
+{
+	HANDLE h;
+	int fd;
+
+	h = pgwin32_open_handle(fileName, fileFlags, false);
+	if (h == INVALID_HANDLE_VALUE)
+		return -1;
+
+#ifdef FRONTEND
+
+	/*
+	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
+	 * fopen() can be used by frontends, having as side-effect to switch the
+	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
+	 * Caller may want to enforce the binary or text mode, but if nothing is
+	 * defined make sure that the default mode maps with what versions older
+	 * than 12 have been doing.
+	 */
+	if ((fileFlags & O_BINARY) == 0)
+		fileFlags |= O_TEXT;
+#endif
+
 	/* _open_osfhandle will, on error, set errno accordingly */
 	if ((fd = _open_osfhandle((intptr_t) h, fileFlags & O_APPEND)) < 0)
 		CloseHandle(h);			/* will not affect errno */
diff --git a/src/port/win32ntdll.c b/src/port/win32ntdll.c
new file mode 100644
index 0000000000..fc9d1b84bb
--- /dev/null
+++ b/src/port/win32ntdll.c
@@ -0,0 +1,68 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.c
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/win32ntdll.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include "port/win32ntdll.h"
+
+NtCreateFile_t pg_NtCreateFile;
+RtlDosPathNameToNtPathName_U_t pg_RtlDosPathNameToNtPathName_U;
+RtlNtStatusToDosError_t pg_RtlNtStatusToDosError;
+
+int
+initialize_ntdll(void)
+{
+	static bool initialized;
+	HMODULE module;
+
+	static const struct {
+		const char *name;
+		pg_funcptr_t *address;
+	} routines[] = {
+		{"NtCreateFile", (pg_funcptr_t *) &pg_NtCreateFile},
+		{"RtlDosPathNameToNtPathName_U",
+		 (pg_funcptr_t *) &pg_RtlDosPathNameToNtPathName_U},
+		{"RtlNtStatusToDosError", (pg_funcptr_t *) &pg_RtlNtStatusToDosError}
+	};
+
+	if (initialized)
+		return 0;
+
+	if (!(module = LoadLibraryEx("ntdll.dll", NULL, 0)))
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+
+	for (int i = 0; i < lengthof(routines); ++i)
+	{
+		pg_funcptr_t	address;
+
+		address = (pg_funcptr_t) GetProcAddress(module, routines[i].name);
+		if (!address)
+		{
+			_dosmaperr(GetLastError());
+			FreeLibrary(module);
+
+			return -1;
+		}
+
+		*(pg_funcptr_t *) routines[i].address = address;
+	}
+
+	initialized = true;
+
+	return 0;
+}
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 2ad8ee1359..c851400dc8 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -18,53 +18,6 @@
 #include "c.h"
 #include <windows.h>
 
-/*
- * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
- * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
- * library.
- */
-#if _WIN32_WINNT < 0x0600
-#include <winternl.h>
-
-#if !defined(__MINGW32__) && !defined(__MINGW64__)
-/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
-typedef struct _FILE_STANDARD_INFORMATION
-{
-	LARGE_INTEGER AllocationSize;
-	LARGE_INTEGER EndOfFile;
-	ULONG		NumberOfLinks;
-	BOOLEAN		DeletePending;
-	BOOLEAN		Directory;
-} FILE_STANDARD_INFORMATION;
-#define FileStandardInformation 5
-#endif							/* !defined(__MINGW32__) &&
-								 * !defined(__MINGW64__) */
-
-typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
-			(IN HANDLE FileHandle,
-			 OUT PIO_STATUS_BLOCK IoStatusBlock,
-			 OUT PVOID FileInformation,
-			 IN ULONG Length,
-			 IN FILE_INFORMATION_CLASS FileInformationClass);
-
-static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;
-
-static HMODULE ntdll = NULL;
-
-/*
- * Load DLL file just once regardless of how many functions we load/call in it.
- */
-static void
-LoadNtdll(void)
-{
-	if (ntdll != NULL)
-		return;
-	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
-}
-
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-
 /*
  * Convert a FILETIME struct into a 64 bit time_t.
  */
@@ -162,120 +115,18 @@ int
 _pgstat64(const char *name, struct stat *buf)
 {
 	/*
-	 * We must use a handle so lstat() returns the information of the target
-	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
-	 * NtQueryInformationFile from Windows 2000 or
-	 * GetFileInformationByHandleEx from Server 2008 / Vista.
+	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
+	 * request FILE_FLAG_BACKUP_SEMANTICS so that we can open directories too,
+	 * for limited purposes.  We use the private handle-based version, so we
+	 * don't risk running out of fds.
 	 */
-	SECURITY_ATTRIBUTES sa;
 	HANDLE		hFile;
 	int			ret;
-#if _WIN32_WINNT < 0x0600
-	IO_STATUS_BLOCK ioStatus;
-	FILE_STANDARD_INFORMATION standardInfo;
-#else
-	FILE_STANDARD_INFO standardInfo;
-#endif
-
-	if (name == NULL || buf == NULL)
-	{
-		errno = EINVAL;
-		return -1;
-	}
 
-	/* fast not-exists check */
-	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return -1;
-	}
-
-	/* get a file handle as lightweight as we can */
-	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-	hFile = CreateFile(name,
-					   GENERIC_READ,
-					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-					   &sa,
-					   OPEN_EXISTING,
-					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
-						FILE_FLAG_OVERLAPPED),
-					   NULL);
+	hFile = pgwin32_open_handle(name, O_RDONLY, true);
 	if (hFile == INVALID_HANDLE_VALUE)
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
 		return -1;
-	}
-
-	memset(&standardInfo, 0, sizeof(standardInfo));
-
-#if _WIN32_WINNT < 0x0600
-	if (_NtQueryInformationFile == NULL)
-	{
-		/* First time through: load ntdll.dll and find NtQueryInformationFile */
-		LoadNtdll();
-		if (ntdll == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-
-		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
-			GetProcAddress(ntdll, "NtQueryInformationFile");
-		if (_NtQueryInformationFile == NULL)
-		{
-			DWORD		err = GetLastError();
 
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-	}
-
-	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
-											sizeof(standardInfo),
-											FileStandardInformation)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#else
-	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
-									  sizeof(standardInfo)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-	if (standardInfo.DeletePending)
-	{
-		/*
-		 * File has been deleted, but is not gone from the filesystem yet.
-		 * This can happen when some process with FILE_SHARE_DELETE has it
-		 * open, and it will be fully removed once that handle is closed.
-		 * Meanwhile, we can't open it, so indicate that the file just doesn't
-		 * exist.
-		 */
-		CloseHandle(hFile);
-		errno = ENOENT;
-		return -1;
-	}
-
-	/* At last we can invoke fileinfo_to_stat */
 	ret = fileinfo_to_stat(hFile, buf);
 
 	CloseHandle(hFile);
@@ -296,11 +147,6 @@ _pgfstat64(int fileno, struct stat *buf)
 		return -1;
 	}
 
-	/*
-	 * Since we already have a file handle there is no need to check for
-	 * ERROR_DELETE_PENDING.
-	 */
-
 	return fileinfo_to_stat(hFile, buf);
 }
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 84f15f7e85..bebb0578dc 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -107,7 +107,8 @@ sub mkvcbuild
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
 	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c bsearch_arg.c quotes.c system.c
 	  strerror.c tar.c thread.c
-	  win32env.c win32error.c win32security.c win32setlocale.c win32stat.c);
+	  win32env.c win32error.c win32ntdll.c
+	  win32security.c win32setlocale.c win32stat.c);
 
 	push(@pgportfiles, 'strtof.c') if ($vsVersion < '14.00');
 
-- 
2.30.2

From 6ab7d5e6b5cc6bf62513a5264641e13fc007ebc7 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 23:49:23 +1200
Subject: [PATCH v3] Check for STATUS_DELETE_PENDING on Windows.

1.  Update our open() wrapper to check for NT's STATUS_DELETE_PENDING
and translate it to appropriate errors.  This is done with
RtlGetLastNtStatus(), which is dynamically loaded from ntdll.  A new
file win32ntdll.c centralizes lookup of NT functions, in case we decide
to add more in the future.

2.  Remove non-working code that was trying to do something similar for
stat(), and just reuse the open() wrapper code.  As a side effect,
stat() also gains resilience against "sharing violation" errors.

3.  Since stat() is used very early in process startup, remove the
requirement that the Win32 signal event has been created before
pgwin32_open_handle() is reached.  Instead, teach pg_usleep() to fall
back to a non-interruptible sleep if reached before the signal event is
available.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 configure                       |   6 ++
 configure.ac                    |   1 +
 src/backend/port/win32/signal.c |  12 ++-
 src/include/port.h              |   1 +
 src/include/port/win32_port.h   |   7 ++
 src/include/port/win32ntdll.h   |  18 ++++
 src/port/open.c                 | 102 ++++++++++----------
 src/port/win32ntdll.c           |  64 +++++++++++++
 src/port/win32stat.c            | 164 +-------------------------------
 src/tools/msvc/Mkvcbuild.pm     |   3 +-
 10 files changed, 169 insertions(+), 209 deletions(-)
 create mode 100644 src/include/port/win32ntdll.h
 create mode 100644 src/port/win32ntdll.c

diff --git a/configure b/configure
index c550cacd5a..adfe03f3f2 100755
--- a/configure
+++ b/configure
@@ -16818,6 +16818,12 @@ esac
  ;;
 esac
 
+  case " $LIBOBJS " in
+  *" win32ntdll.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS win32ntdll.$ac_objext"
+ ;;
+esac
+
   case " $LIBOBJS " in
   *" win32security.$ac_objext "* ) ;;
   *) LIBOBJS="$LIBOBJS win32security.$ac_objext"
diff --git a/configure.ac b/configure.ac
index 2ee710102f..2819b91a8c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1922,6 +1922,7 @@ if test "$PORTNAME" = "win32"; then
   AC_LIBOBJ(system)
   AC_LIBOBJ(win32env)
   AC_LIBOBJ(win32error)
+  AC_LIBOBJ(win32ntdll)
   AC_LIBOBJ(win32security)
   AC_LIBOBJ(win32setlocale)
   AC_LIBOBJ(win32stat)
diff --git a/src/backend/port/win32/signal.c b/src/backend/port/win32/signal.c
index 580a517f3f..61f06a29f6 100644
--- a/src/backend/port/win32/signal.c
+++ b/src/backend/port/win32/signal.c
@@ -52,7 +52,17 @@ static BOOL WINAPI pg_console_handler(DWORD dwCtrlType);
 void
 pg_usleep(long microsec)
 {
-	Assert(pgwin32_signal_event != NULL);
+	if (unlikely(pgwin32_signal_event == NULL))
+	{
+		/*
+		 * If we're reached by pgwin32_open_handle() early in startup before
+		 * the signal event is set up, just fall back to a regular
+		 * non-interruptible sleep.
+		 */
+		SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
+		return;
+	}
+
 	if (WaitForSingleObject(pgwin32_signal_event,
 							(microsec < 500 ? 1 : (microsec + 500) / 1000))
 		== WAIT_OBJECT_0)
diff --git a/src/include/port.h b/src/include/port.h
index 82f63de325..ec64be429c 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -290,6 +290,7 @@ extern bool rmtree(const char *path, bool rmtopdir);
  * passing of other special options.
  */
 #define		O_DIRECT	0x80000000
+extern HANDLE pgwin32_open_handle(const char *, int, bool);
 extern int	pgwin32_open(const char *, int,...);
 extern FILE *pgwin32_fopen(const char *, const char *);
 #define		open(a,b,c) pgwin32_open(a,b,c)
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index 05c5a53442..f11ac5e47a 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -43,9 +43,16 @@
 #define _WINSOCKAPI_
 #endif
 
+/*
+ * Tell windows.h that we're going to include ntstatus.h, to avoid
+ * double-definition of some macros.
+ */
+ #define UMDF_USING_NTSTATUS
+
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include <windows.h>
+#include <ntstatus.h>
 #undef small
 #include <process.h>
 #include <signal.h>
diff --git a/src/include/port/win32ntdll.h b/src/include/port/win32ntdll.h
new file mode 100644
index 0000000000..c4d6a9c00e
--- /dev/null
+++ b/src/include/port/win32ntdll.h
@@ -0,0 +1,18 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.h
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/port/win32ntdll.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+typedef NTSTATUS (__stdcall *RtlGetLastNtStatus_t)(void);
+
+extern RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+extern int initialize_ntdll(void);
diff --git a/src/port/open.c b/src/port/open.c
index 14c6debba9..6c7a70c367 100644
--- a/src/port/open.c
+++ b/src/port/open.c
@@ -19,11 +19,12 @@
 #include "postgres_fe.h"
 #endif
 
+#include "port/win32ntdll.h"
+
 #include <fcntl.h>
 #include <assert.h>
 #include <sys/stat.h>
 
-
 static int
 openFlagsToCreateFileFlags(int openFlags)
 {
@@ -56,38 +57,25 @@ openFlagsToCreateFileFlags(int openFlags)
 }
 
 /*
- *	 - file attribute setting, based on fileMode?
+ * Internal function used by pgwin32_open() and _pgstat64().  When
+ * backup_semantics is true, directories may be opened (for limited uses).  On
+ * failure, INVALID_HANDLE_VALUE is returned and errno is set.
  */
-int
-pgwin32_open(const char *fileName, int fileFlags,...)
+HANDLE
+pgwin32_open_handle(const char *fileName, int fileFlags, bool backup_semantics)
 {
-	int			fd;
-	HANDLE		h = INVALID_HANDLE_VALUE;
+	HANDLE		h;
 	SECURITY_ATTRIBUTES sa;
 	int			loops = 0;
 
+	if (initialize_ntdll() < 0)
+		return INVALID_HANDLE_VALUE;
+
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
 						 (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
 						 _O_SHORT_LIVED | O_DSYNC | O_DIRECT |
 						 (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
-#ifndef FRONTEND
-	Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
-#endif
-
-#ifdef FRONTEND
-
-	/*
-	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
-	 * fopen() can be used by frontends, having as side-effect to switch the
-	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
-	 * Caller may want to enforce the binary or text mode, but if nothing is
-	 * defined make sure that the default mode maps with what versions older
-	 * than 12 have been doing.
-	 */
-	if ((fileFlags & O_BINARY) == 0)
-		fileFlags |= O_TEXT;
-#endif
 
 	sa.nLength = sizeof(sa);
 	sa.bInheritHandle = TRUE;
@@ -102,6 +90,7 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 						   &sa,
 						   openFlagsToCreateFileFlags(fileFlags),
 						   FILE_ATTRIBUTE_NORMAL |
+						   (backup_semantics ? FILE_FLAG_BACKUP_SEMANTICS : 0) |
 						   ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
 						   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
 						   ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
@@ -140,38 +129,55 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 		/*
 		 * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
 		 * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
-		 * case we want to wait a bit and try again, giving up after 1 second
-		 * (since this condition should never persist very long).  However,
-		 * there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
-		 * so care is needed.  In particular that happens if we try to open a
-		 * directory, or of course if there's an actual file-permissions
-		 * problem.  To distinguish these cases, try a stat().  In the
-		 * delete-pending case, it will either also get STATUS_DELETE_PENDING,
-		 * or it will see the file as gone and fail with ENOENT.  In other
-		 * cases it will usually succeed.  The only somewhat-likely case where
-		 * this coding will uselessly wait is if there's a permissions problem
-		 * with a containing directory, which we hope will never happen in any
-		 * performance-critical code paths.
+		 * case, we'd better ask for the NT status too so we can translate it
+		 * to a more Unix-like error.  We hope that nothing clobbers the NT
+		 * status in between the internal NtCreateFile() call and CreateFile()
+		 * returning.
+		 *
+		 * If there's no O_CREAT flag, then we'll pretend the file is
+		 * invisible.  With O_CREAT, we have no choice but to report that
+		 * there's a file in the way (which wouldn't happen on Unix).
 		 */
-		if (err == ERROR_ACCESS_DENIED)
+		if (err == ERROR_ACCESS_DENIED &&
+			pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
 		{
-			if (loops < 10)
-			{
-				struct stat st;
-
-				if (stat(fileName, &st) != 0)
-				{
-					pg_usleep(100000);
-					loops++;
-					continue;
-				}
-			}
+			if (fileFlags & O_CREAT)
+				err = ERROR_FILE_EXISTS;
+			else
+				err = ERROR_FILE_NOT_FOUND;
 		}
 
 		_dosmaperr(err);
-		return -1;
+		return INVALID_HANDLE_VALUE;
 	}
 
+	return h;
+}
+
+int
+pgwin32_open(const char *fileName, int fileFlags,...)
+{
+	HANDLE		h;
+	int			fd;
+
+	h = pgwin32_open_handle(fileName, fileFlags, false);
+	if (h == INVALID_HANDLE_VALUE)
+		return -1;
+
+#ifdef FRONTEND
+
+	/*
+	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
+	 * fopen() can be used by frontends, having as side-effect to switch the
+	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
+	 * Caller may want to enforce the binary or text mode, but if nothing is
+	 * defined make sure that the default mode maps with what versions older
+	 * than 12 have been doing.
+	 */
+	if ((fileFlags & O_BINARY) == 0)
+		fileFlags |= O_TEXT;
+#endif
+
 	/* _open_osfhandle will, on error, set errno accordingly */
 	if ((fd = _open_osfhandle((intptr_t) h, fileFlags & O_APPEND)) < 0)
 		CloseHandle(h);			/* will not affect errno */
diff --git a/src/port/win32ntdll.c b/src/port/win32ntdll.c
new file mode 100644
index 0000000000..b010becadf
--- /dev/null
+++ b/src/port/win32ntdll.c
@@ -0,0 +1,64 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.c
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/win32ntdll.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include "port/win32ntdll.h"
+
+RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+int
+initialize_ntdll(void)
+{
+	static bool initialized;
+	HMODULE		module;
+
+	static const struct
+	{
+		const char *name;
+		pg_funcptr_t *address;
+	}			routines[] = {
+		{"RtlGetLastNtStatus", (pg_funcptr_t *) &pg_RtlGetLastNtStatus}
+	};
+
+	if (initialized)
+		return 0;
+
+	if (!(module = LoadLibraryEx("ntdll.dll", NULL, 0)))
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+
+	for (int i = 0; i < lengthof(routines); ++i)
+	{
+		pg_funcptr_t address;
+
+		address = (pg_funcptr_t) GetProcAddress(module, routines[i].name);
+		if (!address)
+		{
+			_dosmaperr(GetLastError());
+			FreeLibrary(module);
+
+			return -1;
+		}
+
+		*(pg_funcptr_t *) routines[i].address = address;
+	}
+
+	initialized = true;
+
+	return 0;
+}
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 2ad8ee1359..c851400dc8 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -18,53 +18,6 @@
 #include "c.h"
 #include <windows.h>
 
-/*
- * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
- * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
- * library.
- */
-#if _WIN32_WINNT < 0x0600
-#include <winternl.h>
-
-#if !defined(__MINGW32__) && !defined(__MINGW64__)
-/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
-typedef struct _FILE_STANDARD_INFORMATION
-{
-	LARGE_INTEGER AllocationSize;
-	LARGE_INTEGER EndOfFile;
-	ULONG		NumberOfLinks;
-	BOOLEAN		DeletePending;
-	BOOLEAN		Directory;
-} FILE_STANDARD_INFORMATION;
-#define FileStandardInformation 5
-#endif							/* !defined(__MINGW32__) &&
-								 * !defined(__MINGW64__) */
-
-typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
-			(IN HANDLE FileHandle,
-			 OUT PIO_STATUS_BLOCK IoStatusBlock,
-			 OUT PVOID FileInformation,
-			 IN ULONG Length,
-			 IN FILE_INFORMATION_CLASS FileInformationClass);
-
-static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;
-
-static HMODULE ntdll = NULL;
-
-/*
- * Load DLL file just once regardless of how many functions we load/call in it.
- */
-static void
-LoadNtdll(void)
-{
-	if (ntdll != NULL)
-		return;
-	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
-}
-
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-
 /*
  * Convert a FILETIME struct into a 64 bit time_t.
  */
@@ -162,120 +115,18 @@ int
 _pgstat64(const char *name, struct stat *buf)
 {
 	/*
-	 * We must use a handle so lstat() returns the information of the target
-	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
-	 * NtQueryInformationFile from Windows 2000 or
-	 * GetFileInformationByHandleEx from Server 2008 / Vista.
+	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
+	 * request FILE_FLAG_BACKUP_SEMANTICS so that we can open directories too,
+	 * for limited purposes.  We use the private handle-based version, so we
+	 * don't risk running out of fds.
 	 */
-	SECURITY_ATTRIBUTES sa;
 	HANDLE		hFile;
 	int			ret;
-#if _WIN32_WINNT < 0x0600
-	IO_STATUS_BLOCK ioStatus;
-	FILE_STANDARD_INFORMATION standardInfo;
-#else
-	FILE_STANDARD_INFO standardInfo;
-#endif
-
-	if (name == NULL || buf == NULL)
-	{
-		errno = EINVAL;
-		return -1;
-	}
 
-	/* fast not-exists check */
-	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return -1;
-	}
-
-	/* get a file handle as lightweight as we can */
-	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-	hFile = CreateFile(name,
-					   GENERIC_READ,
-					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-					   &sa,
-					   OPEN_EXISTING,
-					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
-						FILE_FLAG_OVERLAPPED),
-					   NULL);
+	hFile = pgwin32_open_handle(name, O_RDONLY, true);
 	if (hFile == INVALID_HANDLE_VALUE)
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
 		return -1;
-	}
-
-	memset(&standardInfo, 0, sizeof(standardInfo));
-
-#if _WIN32_WINNT < 0x0600
-	if (_NtQueryInformationFile == NULL)
-	{
-		/* First time through: load ntdll.dll and find NtQueryInformationFile */
-		LoadNtdll();
-		if (ntdll == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-
-		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
-			GetProcAddress(ntdll, "NtQueryInformationFile");
-		if (_NtQueryInformationFile == NULL)
-		{
-			DWORD		err = GetLastError();
 
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-	}
-
-	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
-											sizeof(standardInfo),
-											FileStandardInformation)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#else
-	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
-									  sizeof(standardInfo)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-	if (standardInfo.DeletePending)
-	{
-		/*
-		 * File has been deleted, but is not gone from the filesystem yet.
-		 * This can happen when some process with FILE_SHARE_DELETE has it
-		 * open, and it will be fully removed once that handle is closed.
-		 * Meanwhile, we can't open it, so indicate that the file just doesn't
-		 * exist.
-		 */
-		CloseHandle(hFile);
-		errno = ENOENT;
-		return -1;
-	}
-
-	/* At last we can invoke fileinfo_to_stat */
 	ret = fileinfo_to_stat(hFile, buf);
 
 	CloseHandle(hFile);
@@ -296,11 +147,6 @@ _pgfstat64(int fileno, struct stat *buf)
 		return -1;
 	}
 
-	/*
-	 * Since we already have a file handle there is no need to check for
-	 * ERROR_DELETE_PENDING.
-	 */
-
 	return fileinfo_to_stat(hFile, buf);
 }
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 84f15f7e85..bebb0578dc 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -107,7 +107,8 @@ sub mkvcbuild
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
 	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c bsearch_arg.c quotes.c system.c
 	  strerror.c tar.c thread.c
-	  win32env.c win32error.c win32security.c win32setlocale.c win32stat.c);
+	  win32env.c win32error.c win32ntdll.c
+	  win32security.c win32setlocale.c win32stat.c);
 
 	push(@pgportfiles, 'strtof.c') if ($vsVersion < '14.00');
 
-- 
2.30.2

From e5e70c03d29f11c3939791ae2d7ff3a94958be38 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 23:49:23 +1200
Subject: [PATCH v4 1/3] Check for STATUS_DELETE_PENDING on Windows.

1.  Update our open() wrapper to check for NT's STATUS_DELETE_PENDING
and translate it to appropriate errors.  This is done with
RtlGetLastNtStatus(), which is dynamically loaded from ntdll.  A new
file win32ntdll.c centralizes lookup of NT functions, in case we decide
to add more in the future.

2.  Remove non-working code that was trying to do something similar for
stat(), and just reuse the open() wrapper code.  As a side effect,
stat() also gains resilience against "sharing violation" errors.

3.  Since stat() is used very early in process startup, remove the
requirement that the Win32 signal event has been created before
pgwin32_open_handle() is reached.  Instead, teach pg_usleep() to fall
back to a non-interruptible sleep if reached before the signal event is
available.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 configure                       |   6 ++
 configure.ac                    |   1 +
 src/backend/port/win32/signal.c |  12 ++-
 src/include/port.h              |   1 +
 src/include/port/win32_port.h   |   8 ++
 src/include/port/win32ntdll.h   |  18 ++++
 src/port/open.c                 | 102 ++++++++++----------
 src/port/win32ntdll.c           |  64 +++++++++++++
 src/port/win32stat.c            | 164 +-------------------------------
 src/tools/msvc/Mkvcbuild.pm     |   3 +-
 10 files changed, 170 insertions(+), 209 deletions(-)
 create mode 100644 src/include/port/win32ntdll.h
 create mode 100644 src/port/win32ntdll.c

diff --git a/configure b/configure
index 5f842a86b2..3b19105328 100755
--- a/configure
+++ b/configure
@@ -16738,6 +16738,12 @@ esac
  ;;
 esac
 
+  case " $LIBOBJS " in
+  *" win32ntdll.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS win32ntdll.$ac_objext"
+ ;;
+esac
+
   case " $LIBOBJS " in
   *" win32security.$ac_objext "* ) ;;
   *) LIBOBJS="$LIBOBJS win32security.$ac_objext"
diff --git a/configure.ac b/configure.ac
index 566a6010dd..e77d4dcf2d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1932,6 +1932,7 @@ if test "$PORTNAME" = "win32"; then
   AC_LIBOBJ(system)
   AC_LIBOBJ(win32env)
   AC_LIBOBJ(win32error)
+  AC_LIBOBJ(win32ntdll)
   AC_LIBOBJ(win32security)
   AC_LIBOBJ(win32setlocale)
   AC_LIBOBJ(win32stat)
diff --git a/src/backend/port/win32/signal.c b/src/backend/port/win32/signal.c
index 580a517f3f..61f06a29f6 100644
--- a/src/backend/port/win32/signal.c
+++ b/src/backend/port/win32/signal.c
@@ -52,7 +52,17 @@ static BOOL WINAPI pg_console_handler(DWORD dwCtrlType);
 void
 pg_usleep(long microsec)
 {
-	Assert(pgwin32_signal_event != NULL);
+	if (unlikely(pgwin32_signal_event == NULL))
+	{
+		/*
+		 * If we're reached by pgwin32_open_handle() early in startup before
+		 * the signal event is set up, just fall back to a regular
+		 * non-interruptible sleep.
+		 */
+		SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
+		return;
+	}
+
 	if (WaitForSingleObject(pgwin32_signal_event,
 							(microsec < 500 ? 1 : (microsec + 500) / 1000))
 		== WAIT_OBJECT_0)
diff --git a/src/include/port.h b/src/include/port.h
index 806fb795ed..fd9c9d6f94 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -296,6 +296,7 @@ extern bool rmtree(const char *path, bool rmtopdir);
  * passing of other special options.
  */
 #define		O_DIRECT	0x80000000
+extern HANDLE pgwin32_open_handle(const char *, int, bool);
 extern int	pgwin32_open(const char *, int,...);
 extern FILE *pgwin32_fopen(const char *, const char *);
 #define		open(a,b,c) pgwin32_open(a,b,c)
diff --git a/src/include/port/win32_port.h b/src/include/port/win32_port.h
index c1c4831595..cadc34636c 100644
--- a/src/include/port/win32_port.h
+++ b/src/include/port/win32_port.h
@@ -51,9 +51,17 @@
  */
 #define WIN32_LEAN_AND_MEAN
 
+/*
+ * Tell windows.h that we're going to include ntstatus.h, to avoid double
+ * definition errors.
+ */
+ #define UMDF_USING_NTSTATUS
+
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include <windows.h>
+#include <ntstatus.h>
+#include <winternl.h>
 #undef small
 #include <process.h>
 #include <signal.h>
diff --git a/src/include/port/win32ntdll.h b/src/include/port/win32ntdll.h
new file mode 100644
index 0000000000..c4d6a9c00e
--- /dev/null
+++ b/src/include/port/win32ntdll.h
@@ -0,0 +1,18 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.h
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/port/win32ntdll.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+typedef NTSTATUS (__stdcall *RtlGetLastNtStatus_t)(void);
+
+extern RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+extern int initialize_ntdll(void);
diff --git a/src/port/open.c b/src/port/open.c
index 14c6debba9..6c7a70c367 100644
--- a/src/port/open.c
+++ b/src/port/open.c
@@ -19,11 +19,12 @@
 #include "postgres_fe.h"
 #endif
 
+#include "port/win32ntdll.h"
+
 #include <fcntl.h>
 #include <assert.h>
 #include <sys/stat.h>
 
-
 static int
 openFlagsToCreateFileFlags(int openFlags)
 {
@@ -56,38 +57,25 @@ openFlagsToCreateFileFlags(int openFlags)
 }
 
 /*
- *	 - file attribute setting, based on fileMode?
+ * Internal function used by pgwin32_open() and _pgstat64().  When
+ * backup_semantics is true, directories may be opened (for limited uses).  On
+ * failure, INVALID_HANDLE_VALUE is returned and errno is set.
  */
-int
-pgwin32_open(const char *fileName, int fileFlags,...)
+HANDLE
+pgwin32_open_handle(const char *fileName, int fileFlags, bool backup_semantics)
 {
-	int			fd;
-	HANDLE		h = INVALID_HANDLE_VALUE;
+	HANDLE		h;
 	SECURITY_ATTRIBUTES sa;
 	int			loops = 0;
 
+	if (initialize_ntdll() < 0)
+		return INVALID_HANDLE_VALUE;
+
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
 						 (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
 						 _O_SHORT_LIVED | O_DSYNC | O_DIRECT |
 						 (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
-#ifndef FRONTEND
-	Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
-#endif
-
-#ifdef FRONTEND
-
-	/*
-	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
-	 * fopen() can be used by frontends, having as side-effect to switch the
-	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
-	 * Caller may want to enforce the binary or text mode, but if nothing is
-	 * defined make sure that the default mode maps with what versions older
-	 * than 12 have been doing.
-	 */
-	if ((fileFlags & O_BINARY) == 0)
-		fileFlags |= O_TEXT;
-#endif
 
 	sa.nLength = sizeof(sa);
 	sa.bInheritHandle = TRUE;
@@ -102,6 +90,7 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 						   &sa,
 						   openFlagsToCreateFileFlags(fileFlags),
 						   FILE_ATTRIBUTE_NORMAL |
+						   (backup_semantics ? FILE_FLAG_BACKUP_SEMANTICS : 0) |
 						   ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
 						   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
 						   ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
@@ -140,38 +129,55 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 		/*
 		 * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
 		 * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
-		 * case we want to wait a bit and try again, giving up after 1 second
-		 * (since this condition should never persist very long).  However,
-		 * there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
-		 * so care is needed.  In particular that happens if we try to open a
-		 * directory, or of course if there's an actual file-permissions
-		 * problem.  To distinguish these cases, try a stat().  In the
-		 * delete-pending case, it will either also get STATUS_DELETE_PENDING,
-		 * or it will see the file as gone and fail with ENOENT.  In other
-		 * cases it will usually succeed.  The only somewhat-likely case where
-		 * this coding will uselessly wait is if there's a permissions problem
-		 * with a containing directory, which we hope will never happen in any
-		 * performance-critical code paths.
+		 * case, we'd better ask for the NT status too so we can translate it
+		 * to a more Unix-like error.  We hope that nothing clobbers the NT
+		 * status in between the internal NtCreateFile() call and CreateFile()
+		 * returning.
+		 *
+		 * If there's no O_CREAT flag, then we'll pretend the file is
+		 * invisible.  With O_CREAT, we have no choice but to report that
+		 * there's a file in the way (which wouldn't happen on Unix).
 		 */
-		if (err == ERROR_ACCESS_DENIED)
+		if (err == ERROR_ACCESS_DENIED &&
+			pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
 		{
-			if (loops < 10)
-			{
-				struct stat st;
-
-				if (stat(fileName, &st) != 0)
-				{
-					pg_usleep(100000);
-					loops++;
-					continue;
-				}
-			}
+			if (fileFlags & O_CREAT)
+				err = ERROR_FILE_EXISTS;
+			else
+				err = ERROR_FILE_NOT_FOUND;
 		}
 
 		_dosmaperr(err);
-		return -1;
+		return INVALID_HANDLE_VALUE;
 	}
 
+	return h;
+}
+
+int
+pgwin32_open(const char *fileName, int fileFlags,...)
+{
+	HANDLE		h;
+	int			fd;
+
+	h = pgwin32_open_handle(fileName, fileFlags, false);
+	if (h == INVALID_HANDLE_VALUE)
+		return -1;
+
+#ifdef FRONTEND
+
+	/*
+	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
+	 * fopen() can be used by frontends, having as side-effect to switch the
+	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
+	 * Caller may want to enforce the binary or text mode, but if nothing is
+	 * defined make sure that the default mode maps with what versions older
+	 * than 12 have been doing.
+	 */
+	if ((fileFlags & O_BINARY) == 0)
+		fileFlags |= O_TEXT;
+#endif
+
 	/* _open_osfhandle will, on error, set errno accordingly */
 	if ((fd = _open_osfhandle((intptr_t) h, fileFlags & O_APPEND)) < 0)
 		CloseHandle(h);			/* will not affect errno */
diff --git a/src/port/win32ntdll.c b/src/port/win32ntdll.c
new file mode 100644
index 0000000000..b010becadf
--- /dev/null
+++ b/src/port/win32ntdll.c
@@ -0,0 +1,64 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.c
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/win32ntdll.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include "port/win32ntdll.h"
+
+RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+int
+initialize_ntdll(void)
+{
+	static bool initialized;
+	HMODULE		module;
+
+	static const struct
+	{
+		const char *name;
+		pg_funcptr_t *address;
+	}			routines[] = {
+		{"RtlGetLastNtStatus", (pg_funcptr_t *) &pg_RtlGetLastNtStatus}
+	};
+
+	if (initialized)
+		return 0;
+
+	if (!(module = LoadLibraryEx("ntdll.dll", NULL, 0)))
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+
+	for (int i = 0; i < lengthof(routines); ++i)
+	{
+		pg_funcptr_t address;
+
+		address = (pg_funcptr_t) GetProcAddress(module, routines[i].name);
+		if (!address)
+		{
+			_dosmaperr(GetLastError());
+			FreeLibrary(module);
+
+			return -1;
+		}
+
+		*(pg_funcptr_t *) routines[i].address = address;
+	}
+
+	initialized = true;
+
+	return 0;
+}
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 426e01f0ef..29e13409e6 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -18,53 +18,6 @@
 #include "c.h"
 #include <windows.h>
 
-/*
- * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
- * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
- * library.
- */
-#if _WIN32_WINNT < 0x0600
-#include <winternl.h>
-
-#if !defined(__MINGW32__) && !defined(__MINGW64__)
-/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
-typedef struct _FILE_STANDARD_INFORMATION
-{
-	LARGE_INTEGER AllocationSize;
-	LARGE_INTEGER EndOfFile;
-	ULONG		NumberOfLinks;
-	BOOLEAN		DeletePending;
-	BOOLEAN		Directory;
-} FILE_STANDARD_INFORMATION;
-#define FileStandardInformation 5
-#endif							/* !defined(__MINGW32__) &&
-								 * !defined(__MINGW64__) */
-
-typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
-			(IN HANDLE FileHandle,
-			 OUT PIO_STATUS_BLOCK IoStatusBlock,
-			 OUT PVOID FileInformation,
-			 IN ULONG Length,
-			 IN FILE_INFORMATION_CLASS FileInformationClass);
-
-static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;
-
-static HMODULE ntdll = NULL;
-
-/*
- * Load DLL file just once regardless of how many functions we load/call in it.
- */
-static void
-LoadNtdll(void)
-{
-	if (ntdll != NULL)
-		return;
-	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
-}
-
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-
 /*
  * Convert a FILETIME struct into a 64 bit time_t.
  */
@@ -162,120 +115,18 @@ int
 _pgstat64(const char *name, struct stat *buf)
 {
 	/*
-	 * We must use a handle so lstat() returns the information of the target
-	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
-	 * NtQueryInformationFile from Windows 2000 or
-	 * GetFileInformationByHandleEx from Server 2008 / Vista.
+	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
+	 * request FILE_FLAG_BACKUP_SEMANTICS so that we can open directories too,
+	 * for limited purposes.  We use the private handle-based version, so we
+	 * don't risk running out of fds.
 	 */
-	SECURITY_ATTRIBUTES sa;
 	HANDLE		hFile;
 	int			ret;
-#if _WIN32_WINNT < 0x0600
-	IO_STATUS_BLOCK ioStatus;
-	FILE_STANDARD_INFORMATION standardInfo;
-#else
-	FILE_STANDARD_INFO standardInfo;
-#endif
-
-	if (name == NULL || buf == NULL)
-	{
-		errno = EINVAL;
-		return -1;
-	}
 
-	/* fast not-exists check */
-	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return -1;
-	}
-
-	/* get a file handle as lightweight as we can */
-	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-	hFile = CreateFile(name,
-					   GENERIC_READ,
-					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-					   &sa,
-					   OPEN_EXISTING,
-					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
-						FILE_FLAG_OVERLAPPED),
-					   NULL);
+	hFile = pgwin32_open_handle(name, O_RDONLY, true);
 	if (hFile == INVALID_HANDLE_VALUE)
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
 		return -1;
-	}
-
-	memset(&standardInfo, 0, sizeof(standardInfo));
-
-#if _WIN32_WINNT < 0x0600
-	if (_NtQueryInformationFile == NULL)
-	{
-		/* First time through: load ntdll.dll and find NtQueryInformationFile */
-		LoadNtdll();
-		if (ntdll == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-
-		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
-			GetProcAddress(ntdll, "NtQueryInformationFile");
-		if (_NtQueryInformationFile == NULL)
-		{
-			DWORD		err = GetLastError();
 
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-	}
-
-	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
-											sizeof(standardInfo),
-											FileStandardInformation)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#else
-	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
-									  sizeof(standardInfo)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-	if (standardInfo.DeletePending)
-	{
-		/*
-		 * File has been deleted, but is not gone from the filesystem yet.
-		 * This can happen when some process with FILE_SHARE_DELETE has it
-		 * open, and it will be fully removed once that handle is closed.
-		 * Meanwhile, we can't open it, so indicate that the file just doesn't
-		 * exist.
-		 */
-		CloseHandle(hFile);
-		errno = ENOENT;
-		return -1;
-	}
-
-	/* At last we can invoke fileinfo_to_stat */
 	ret = fileinfo_to_stat(hFile, buf);
 
 	CloseHandle(hFile);
@@ -316,11 +167,6 @@ _pgfstat64(int fileno, struct stat *buf)
 		return 0;
 	}
 
-	/*
-	 * Since we already have a file handle there is no need to check for
-	 * ERROR_DELETE_PENDING.
-	 */
-
 	return fileinfo_to_stat(hFile, buf);
 }
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 5a374a4727..404c45a6f3 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -107,7 +107,8 @@ sub mkvcbuild
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
 	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c bsearch_arg.c quotes.c system.c
 	  strerror.c tar.c thread.c
-	  win32env.c win32error.c win32security.c win32setlocale.c win32stat.c);
+	  win32env.c win32error.c win32ntdll.c
+	  win32security.c win32setlocale.c win32stat.c);
 
 	push(@pgportfiles, 'strtof.c') if ($vsVersion < '14.00');
 
-- 
2.33.1

From d04cee422b37b299443ea6aeec651336a5f2c85a Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Sun, 5 Sep 2021 23:49:23 +1200
Subject: [PATCH v5 1/3] Check for STATUS_DELETE_PENDING on Windows.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

1.  Update our open() wrapper to check for NT's STATUS_DELETE_PENDING
and translate it to appropriate errors.  This is done with
RtlGetLastNtStatus(), which is dynamically loaded from ntdll.  A new
file win32ntdll.c centralizes lookup of NT functions, in case we decide
to add more in the future.

2.  Remove non-working code that was trying to do something similar for
stat(), and just reuse the open() wrapper code.  As a side effect,
stat() also gains resilience against "sharing violation" errors.

3.  Since stat() is used very early in process startup, remove the
requirement that the Win32 signal event has been created before
pgwin32_open_handle() is reached.  Instead, teach pg_usleep() to fall
back to a non-interruptible sleep if reached before the signal event is
available.

Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGJz_pZTF9mckn6XgSv69%2BjGwdgLkxZ6b3NWGLBCVjqUZA%40mail.gmail.com
---
 configure                       |   6 ++
 configure.ac                    |   1 +
 src/backend/port/win32/signal.c |  12 ++-
 src/include/port.h              |   1 +
 src/include/port/win32ntdll.h   |  27 ++++++
 src/port/open.c                 | 104 ++++++++++----------
 src/port/win32ntdll.c           |  66 +++++++++++++
 src/port/win32stat.c            | 164 +-------------------------------
 src/tools/msvc/Mkvcbuild.pm     |   3 +-
 9 files changed, 175 insertions(+), 209 deletions(-)
 create mode 100644 src/include/port/win32ntdll.h
 create mode 100644 src/port/win32ntdll.c

diff --git a/configure b/configure
index 5f842a86b2..3b19105328 100755
--- a/configure
+++ b/configure
@@ -16738,6 +16738,12 @@ esac
  ;;
 esac
 
+  case " $LIBOBJS " in
+  *" win32ntdll.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS win32ntdll.$ac_objext"
+ ;;
+esac
+
   case " $LIBOBJS " in
   *" win32security.$ac_objext "* ) ;;
   *) LIBOBJS="$LIBOBJS win32security.$ac_objext"
diff --git a/configure.ac b/configure.ac
index 566a6010dd..e77d4dcf2d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1932,6 +1932,7 @@ if test "$PORTNAME" = "win32"; then
   AC_LIBOBJ(system)
   AC_LIBOBJ(win32env)
   AC_LIBOBJ(win32error)
+  AC_LIBOBJ(win32ntdll)
   AC_LIBOBJ(win32security)
   AC_LIBOBJ(win32setlocale)
   AC_LIBOBJ(win32stat)
diff --git a/src/backend/port/win32/signal.c b/src/backend/port/win32/signal.c
index 580a517f3f..61f06a29f6 100644
--- a/src/backend/port/win32/signal.c
+++ b/src/backend/port/win32/signal.c
@@ -52,7 +52,17 @@ static BOOL WINAPI pg_console_handler(DWORD dwCtrlType);
 void
 pg_usleep(long microsec)
 {
-	Assert(pgwin32_signal_event != NULL);
+	if (unlikely(pgwin32_signal_event == NULL))
+	{
+		/*
+		 * If we're reached by pgwin32_open_handle() early in startup before
+		 * the signal event is set up, just fall back to a regular
+		 * non-interruptible sleep.
+		 */
+		SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
+		return;
+	}
+
 	if (WaitForSingleObject(pgwin32_signal_event,
 							(microsec < 500 ? 1 : (microsec + 500) / 1000))
 		== WAIT_OBJECT_0)
diff --git a/src/include/port.h b/src/include/port.h
index 806fb795ed..fd9c9d6f94 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -296,6 +296,7 @@ extern bool rmtree(const char *path, bool rmtopdir);
  * passing of other special options.
  */
 #define		O_DIRECT	0x80000000
+extern HANDLE pgwin32_open_handle(const char *, int, bool);
 extern int	pgwin32_open(const char *, int,...);
 extern FILE *pgwin32_fopen(const char *, const char *);
 #define		open(a,b,c) pgwin32_open(a,b,c)
diff --git a/src/include/port/win32ntdll.h b/src/include/port/win32ntdll.h
new file mode 100644
index 0000000000..4d8808b3aa
--- /dev/null
+++ b/src/include/port/win32ntdll.h
@@ -0,0 +1,27 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.h
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/port/win32ntdll.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*
+ * Because this includes NT headers that normally conflict with Win32 headers,
+ * any translation unit that includes it should #define UMDF_USING_NTSTATUS
+ * before including <windows.h>.
+ */
+
+#include <ntstatus.h>
+#include <winternl.h>
+
+typedef NTSTATUS (__stdcall *RtlGetLastNtStatus_t) (void);
+
+extern RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+extern int	initialize_ntdll(void);
diff --git a/src/port/open.c b/src/port/open.c
index 14c6debba9..7b52bd83c2 100644
--- a/src/port/open.c
+++ b/src/port/open.c
@@ -13,17 +13,20 @@
 
 #ifdef WIN32
 
+#define UMDF_USING_NTSTATUS
+
 #ifndef FRONTEND
 #include "postgres.h"
 #else
 #include "postgres_fe.h"
 #endif
 
+#include "port/win32ntdll.h"
+
 #include <fcntl.h>
 #include <assert.h>
 #include <sys/stat.h>
 
-
 static int
 openFlagsToCreateFileFlags(int openFlags)
 {
@@ -56,38 +59,25 @@ openFlagsToCreateFileFlags(int openFlags)
 }
 
 /*
- *	 - file attribute setting, based on fileMode?
+ * Internal function used by pgwin32_open() and _pgstat64().  When
+ * backup_semantics is true, directories may be opened (for limited uses).  On
+ * failure, INVALID_HANDLE_VALUE is returned and errno is set.
  */
-int
-pgwin32_open(const char *fileName, int fileFlags,...)
+HANDLE
+pgwin32_open_handle(const char *fileName, int fileFlags, bool backup_semantics)
 {
-	int			fd;
-	HANDLE		h = INVALID_HANDLE_VALUE;
+	HANDLE		h;
 	SECURITY_ATTRIBUTES sa;
 	int			loops = 0;
 
+	if (initialize_ntdll() < 0)
+		return INVALID_HANDLE_VALUE;
+
 	/* Check that we can handle the request */
 	assert((fileFlags & ((O_RDONLY | O_WRONLY | O_RDWR) | O_APPEND |
 						 (O_RANDOM | O_SEQUENTIAL | O_TEMPORARY) |
 						 _O_SHORT_LIVED | O_DSYNC | O_DIRECT |
 						 (O_CREAT | O_TRUNC | O_EXCL) | (O_TEXT | O_BINARY))) == fileFlags);
-#ifndef FRONTEND
-	Assert(pgwin32_signal_event != NULL);	/* small chance of pg_usleep() */
-#endif
-
-#ifdef FRONTEND
-
-	/*
-	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
-	 * fopen() can be used by frontends, having as side-effect to switch the
-	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
-	 * Caller may want to enforce the binary or text mode, but if nothing is
-	 * defined make sure that the default mode maps with what versions older
-	 * than 12 have been doing.
-	 */
-	if ((fileFlags & O_BINARY) == 0)
-		fileFlags |= O_TEXT;
-#endif
 
 	sa.nLength = sizeof(sa);
 	sa.bInheritHandle = TRUE;
@@ -102,6 +92,7 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 						   &sa,
 						   openFlagsToCreateFileFlags(fileFlags),
 						   FILE_ATTRIBUTE_NORMAL |
+						   (backup_semantics ? FILE_FLAG_BACKUP_SEMANTICS : 0) |
 						   ((fileFlags & O_RANDOM) ? FILE_FLAG_RANDOM_ACCESS : 0) |
 						   ((fileFlags & O_SEQUENTIAL) ? FILE_FLAG_SEQUENTIAL_SCAN : 0) |
 						   ((fileFlags & _O_SHORT_LIVED) ? FILE_ATTRIBUTE_TEMPORARY : 0) |
@@ -140,38 +131,55 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 		/*
 		 * ERROR_ACCESS_DENIED is returned if the file is deleted but not yet
 		 * gone (Windows NT status code is STATUS_DELETE_PENDING).  In that
-		 * case we want to wait a bit and try again, giving up after 1 second
-		 * (since this condition should never persist very long).  However,
-		 * there are other commonly-hit cases that return ERROR_ACCESS_DENIED,
-		 * so care is needed.  In particular that happens if we try to open a
-		 * directory, or of course if there's an actual file-permissions
-		 * problem.  To distinguish these cases, try a stat().  In the
-		 * delete-pending case, it will either also get STATUS_DELETE_PENDING,
-		 * or it will see the file as gone and fail with ENOENT.  In other
-		 * cases it will usually succeed.  The only somewhat-likely case where
-		 * this coding will uselessly wait is if there's a permissions problem
-		 * with a containing directory, which we hope will never happen in any
-		 * performance-critical code paths.
+		 * case, we'd better ask for the NT status too so we can translate it
+		 * to a more Unix-like error.  We hope that nothing clobbers the NT
+		 * status in between the internal NtCreateFile() call and CreateFile()
+		 * returning.
+		 *
+		 * If there's no O_CREAT flag, then we'll pretend the file is
+		 * invisible.  With O_CREAT, we have no choice but to report that
+		 * there's a file in the way (which wouldn't happen on Unix).
 		 */
-		if (err == ERROR_ACCESS_DENIED)
+		if (err == ERROR_ACCESS_DENIED &&
+			pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
 		{
-			if (loops < 10)
-			{
-				struct stat st;
-
-				if (stat(fileName, &st) != 0)
-				{
-					pg_usleep(100000);
-					loops++;
-					continue;
-				}
-			}
+			if (fileFlags & O_CREAT)
+				err = ERROR_FILE_EXISTS;
+			else
+				err = ERROR_FILE_NOT_FOUND;
 		}
 
 		_dosmaperr(err);
-		return -1;
+		return INVALID_HANDLE_VALUE;
 	}
 
+	return h;
+}
+
+int
+pgwin32_open(const char *fileName, int fileFlags,...)
+{
+	HANDLE		h;
+	int			fd;
+
+	h = pgwin32_open_handle(fileName, fileFlags, false);
+	if (h == INVALID_HANDLE_VALUE)
+		return -1;
+
+#ifdef FRONTEND
+
+	/*
+	 * Since PostgreSQL 12, those concurrent-safe versions of open() and
+	 * fopen() can be used by frontends, having as side-effect to switch the
+	 * file-translation mode from O_TEXT to O_BINARY if none is specified.
+	 * Caller may want to enforce the binary or text mode, but if nothing is
+	 * defined make sure that the default mode maps with what versions older
+	 * than 12 have been doing.
+	 */
+	if ((fileFlags & O_BINARY) == 0)
+		fileFlags |= O_TEXT;
+#endif
+
 	/* _open_osfhandle will, on error, set errno accordingly */
 	if ((fd = _open_osfhandle((intptr_t) h, fileFlags & O_APPEND)) < 0)
 		CloseHandle(h);			/* will not affect errno */
diff --git a/src/port/win32ntdll.c b/src/port/win32ntdll.c
new file mode 100644
index 0000000000..4d60d00f7d
--- /dev/null
+++ b/src/port/win32ntdll.c
@@ -0,0 +1,66 @@
+/*-------------------------------------------------------------------------
+ *
+ * win32ntdll.c
+ *	  Dynamically loaded Windows NT functions.
+ *
+ * Portions Copyright (c) 2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/win32ntdll.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#define UMDF_USING_NTSTATUS
+
+#include "c.h"
+
+#include "port/win32ntdll.h"
+
+RtlGetLastNtStatus_t pg_RtlGetLastNtStatus;
+
+int
+initialize_ntdll(void)
+{
+	static bool initialized;
+	HMODULE		module;
+
+	static const struct
+	{
+		const char *name;
+		pg_funcptr_t *address;
+	}			routines[] = {
+		{"RtlGetLastNtStatus", (pg_funcptr_t *) &pg_RtlGetLastNtStatus}
+	};
+
+	if (initialized)
+		return 0;
+
+	if (!(module = LoadLibraryEx("ntdll.dll", NULL, 0)))
+	{
+		_dosmaperr(GetLastError());
+		return -1;
+	}
+
+	for (int i = 0; i < lengthof(routines); ++i)
+	{
+		pg_funcptr_t address;
+
+		address = (pg_funcptr_t) GetProcAddress(module, routines[i].name);
+		if (!address)
+		{
+			_dosmaperr(GetLastError());
+			FreeLibrary(module);
+
+			return -1;
+		}
+
+		*(pg_funcptr_t *) routines[i].address = address;
+	}
+
+	initialized = true;
+
+	return 0;
+}
diff --git a/src/port/win32stat.c b/src/port/win32stat.c
index 426e01f0ef..29e13409e6 100644
--- a/src/port/win32stat.c
+++ b/src/port/win32stat.c
@@ -18,53 +18,6 @@
 #include "c.h"
 #include <windows.h>
 
-/*
- * In order to support MinGW and MSVC2013 we use NtQueryInformationFile as an
- * alternative for GetFileInformationByHandleEx. It is loaded from the ntdll
- * library.
- */
-#if _WIN32_WINNT < 0x0600
-#include <winternl.h>
-
-#if !defined(__MINGW32__) && !defined(__MINGW64__)
-/* MinGW includes this in <winternl.h>, but it is missing in MSVC */
-typedef struct _FILE_STANDARD_INFORMATION
-{
-	LARGE_INTEGER AllocationSize;
-	LARGE_INTEGER EndOfFile;
-	ULONG		NumberOfLinks;
-	BOOLEAN		DeletePending;
-	BOOLEAN		Directory;
-} FILE_STANDARD_INFORMATION;
-#define FileStandardInformation 5
-#endif							/* !defined(__MINGW32__) &&
-								 * !defined(__MINGW64__) */
-
-typedef NTSTATUS (NTAPI * PFN_NTQUERYINFORMATIONFILE)
-			(IN HANDLE FileHandle,
-			 OUT PIO_STATUS_BLOCK IoStatusBlock,
-			 OUT PVOID FileInformation,
-			 IN ULONG Length,
-			 IN FILE_INFORMATION_CLASS FileInformationClass);
-
-static PFN_NTQUERYINFORMATIONFILE _NtQueryInformationFile = NULL;
-
-static HMODULE ntdll = NULL;
-
-/*
- * Load DLL file just once regardless of how many functions we load/call in it.
- */
-static void
-LoadNtdll(void)
-{
-	if (ntdll != NULL)
-		return;
-	ntdll = LoadLibraryEx("ntdll.dll", NULL, 0);
-}
-
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-
 /*
  * Convert a FILETIME struct into a 64 bit time_t.
  */
@@ -162,120 +115,18 @@ int
 _pgstat64(const char *name, struct stat *buf)
 {
 	/*
-	 * We must use a handle so lstat() returns the information of the target
-	 * file.  To have a reliable test for ERROR_DELETE_PENDING, we use
-	 * NtQueryInformationFile from Windows 2000 or
-	 * GetFileInformationByHandleEx from Server 2008 / Vista.
+	 * Our open wrapper will report STATUS_DELETE_PENDING as ENOENT.  We
+	 * request FILE_FLAG_BACKUP_SEMANTICS so that we can open directories too,
+	 * for limited purposes.  We use the private handle-based version, so we
+	 * don't risk running out of fds.
 	 */
-	SECURITY_ATTRIBUTES sa;
 	HANDLE		hFile;
 	int			ret;
-#if _WIN32_WINNT < 0x0600
-	IO_STATUS_BLOCK ioStatus;
-	FILE_STANDARD_INFORMATION standardInfo;
-#else
-	FILE_STANDARD_INFO standardInfo;
-#endif
-
-	if (name == NULL || buf == NULL)
-	{
-		errno = EINVAL;
-		return -1;
-	}
 
-	/* fast not-exists check */
-	if (GetFileAttributes(name) == INVALID_FILE_ATTRIBUTES)
-	{
-		_dosmaperr(GetLastError());
-		return -1;
-	}
-
-	/* get a file handle as lightweight as we can */
-	sa.nLength = sizeof(SECURITY_ATTRIBUTES);
-	sa.bInheritHandle = TRUE;
-	sa.lpSecurityDescriptor = NULL;
-	hFile = CreateFile(name,
-					   GENERIC_READ,
-					   (FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE),
-					   &sa,
-					   OPEN_EXISTING,
-					   (FILE_FLAG_NO_BUFFERING | FILE_FLAG_BACKUP_SEMANTICS |
-						FILE_FLAG_OVERLAPPED),
-					   NULL);
+	hFile = pgwin32_open_handle(name, O_RDONLY, true);
 	if (hFile == INVALID_HANDLE_VALUE)
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
 		return -1;
-	}
-
-	memset(&standardInfo, 0, sizeof(standardInfo));
-
-#if _WIN32_WINNT < 0x0600
-	if (_NtQueryInformationFile == NULL)
-	{
-		/* First time through: load ntdll.dll and find NtQueryInformationFile */
-		LoadNtdll();
-		if (ntdll == NULL)
-		{
-			DWORD		err = GetLastError();
-
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-
-		_NtQueryInformationFile = (PFN_NTQUERYINFORMATIONFILE) (pg_funcptr_t)
-			GetProcAddress(ntdll, "NtQueryInformationFile");
-		if (_NtQueryInformationFile == NULL)
-		{
-			DWORD		err = GetLastError();
 
-			CloseHandle(hFile);
-			_dosmaperr(err);
-			return -1;
-		}
-	}
-
-	if (!NT_SUCCESS(_NtQueryInformationFile(hFile, &ioStatus, &standardInfo,
-											sizeof(standardInfo),
-											FileStandardInformation)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#else
-	if (!GetFileInformationByHandleEx(hFile, FileStandardInfo, &standardInfo,
-									  sizeof(standardInfo)))
-	{
-		DWORD		err = GetLastError();
-
-		CloseHandle(hFile);
-		_dosmaperr(err);
-		return -1;
-	}
-#endif							/* _WIN32_WINNT < 0x0600 */
-
-	if (standardInfo.DeletePending)
-	{
-		/*
-		 * File has been deleted, but is not gone from the filesystem yet.
-		 * This can happen when some process with FILE_SHARE_DELETE has it
-		 * open, and it will be fully removed once that handle is closed.
-		 * Meanwhile, we can't open it, so indicate that the file just doesn't
-		 * exist.
-		 */
-		CloseHandle(hFile);
-		errno = ENOENT;
-		return -1;
-	}
-
-	/* At last we can invoke fileinfo_to_stat */
 	ret = fileinfo_to_stat(hFile, buf);
 
 	CloseHandle(hFile);
@@ -316,11 +167,6 @@ _pgfstat64(int fileno, struct stat *buf)
 		return 0;
 	}
 
-	/*
-	 * Since we already have a file handle there is no need to check for
-	 * ERROR_DELETE_PENDING.
-	 */
-
 	return fileinfo_to_stat(hFile, buf);
 }
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 5a374a4727..404c45a6f3 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -107,7 +107,8 @@ sub mkvcbuild
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
 	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c bsearch_arg.c quotes.c system.c
 	  strerror.c tar.c thread.c
-	  win32env.c win32error.c win32security.c win32setlocale.c win32stat.c);
+	  win32env.c win32error.c win32ntdll.c
+	  win32security.c win32setlocale.c win32stat.c);
 
 	push(@pgportfiles, 'strtof.c') if ($vsVersion < '14.00');
 
-- 
2.33.1