fs/io/FileOutputStream: add mode CREATE_VISIBLE

src/fs/io/FileOutputStream.cxx

@@ -26,7 +26,11 @@ FileOutputStream::FileOutputStream(Path _path, Mode _mode)
 {
 	switch (mode) {
 	case Mode::CREATE:
-		OpenCreate();
+		OpenCreate(false);
+		break;
+
+	case Mode::CREATE_VISIBLE:
+		OpenCreate(true);
 		break;
 
 	case Mode::APPEND_EXISTING:
@@ -42,7 +46,7 @@ FileOutputStream::FileOutputStream(Path _path, Mode _mode)
 #ifdef WIN32
 
 inline void
-FileOutputStream::OpenCreate()
+FileOutputStream::OpenCreate(gcc_unused bool visible)
 {
 	handle = CreateFile(path.c_str(), GENERIC_WRITE, 0, nullptr,
 			    CREATE_ALWAYS,
@@ -147,11 +151,11 @@ OpenTempFile(FileDescriptor &fd, Path path)
 #endif /* HAVE_LINKAT */
 
 inline void
-FileOutputStream::OpenCreate()
+FileOutputStream::OpenCreate(bool visible)
 {
 #ifdef HAVE_LINKAT
 	/* try Linux's O_TMPFILE first */
-	is_tmpfile = OpenTempFile(fd, GetPath());
+	is_tmpfile = !visible && OpenTempFile(fd, GetPath());
 	if (!is_tmpfile) {
 #endif
 		/* fall back to plain POSIX */
@@ -241,6 +245,7 @@ FileOutputStream::Cancel()
 			unlink(GetPath().c_str());
 		break;
 
+	case Mode::CREATE_VISIBLE:
 	case Mode::APPEND_EXISTING:
 	case Mode::APPEND_OR_CREATE:
 		/* can't roll this back */

src/fs/io/FileOutputStream.hxx

@@ -65,6 +65,13 @@ public:
 		CREATE,
 
 		/**
+		 * Like #CREATE, but no attempt is made to hide file
+		 * contents during the transaction (e.g. via O_TMPFILE
+		 * or a hidden temporary file).
+		 */
+		CREATE_VISIBLE,
+
+		/**
 		 * Append to a file that already exists.  If it does
 		 * not, an exception is thrown.
 		 */
@@ -103,7 +110,7 @@ public:
 	void Cancel();
 
 private:
-	void OpenCreate();
+	void OpenCreate(bool visible);
 	void OpenAppend(bool create);
 
 	bool Close() {