dirCreateDir

fn dirCreateDir(
    userdata: ?*anyopaque,
    dir: Dir,
    sub_path: []const u8,
    permissions: Dir.Permissions,
) Dir.CreateDirError!void {
    const ev: *Evented = @ptrCast(@alignCast(userdata));

    var path_buffer: [PATH_MAX]u8 = undefined;
    const sub_path_posix = try pathToPosix(sub_path, &path_buffer);

    var cancel_region: CancelRegion = .init();
    defer cancel_region.deinit();
    while (true) {
        const thread = try cancel_region.awaitIoUring();
        thread.enqueue().* = .{
            .opcode = .MKDIRAT,
            .flags = 0,
            .ioprio = 0,
            .fd = dir.handle,
            .off = 0,
            .addr = @intFromPtr(sub_path_posix.ptr),
            .len = permissions.toMode(),
            .rw_flags = 0,
            .user_data = @intFromPtr(cancel_region.fiber),
            .buf_index = 0,
            .personality = 0,
            .splice_fd_in = 0,
            .addr3 = 0,
            .resv = 0,
        };
        ev.yield(null, .nothing);
        switch (cancel_region.errno()) {
            .SUCCESS => return,
            .INTR, .CANCELED => {},
            .ACCES => return error.AccessDenied,
            .BADF => |err| return errnoBug(err), // File descriptor used after closed.
            .PERM => return error.PermissionDenied,
            .DQUOT => return error.DiskQuota,
            .EXIST => return error.PathAlreadyExists,
            .FAULT => |err| return errnoBug(err),
            .LOOP => return error.SymLinkLoop,
            .MLINK => return error.LinkQuotaExceeded,
            .NAMETOOLONG => return error.NameTooLong,
            .NOENT => return error.FileNotFound,
            .NOMEM => return error.SystemResources,
            .NOSPC => return error.NoSpaceLeft,
            .NOTDIR => return error.NotDir,
            .ROFS => return error.ReadOnlyFileSystem,
            .ILSEQ => return error.BadPathName,
            else => |err| return unexpectedErrno(err),
        }
    }
}