linkat

fn linkat(
    ev: *Evented,
    cancel_region: *CancelRegion,
    old_dir: fd_t,
    old_path: [*:0]const u8,
    new_dir: fd_t,
    new_path: [*:0]const u8,
    flags: u32,
) File.HardLinkError!void {
    // allowed flags: https://man7.org/linux/man-pages/man2/linkat.2.html
    assert(flags & ~(@as(u32, linux.AT.SYMLINK_FOLLOW | linux.AT.EMPTY_PATH)) == 0);
    while (true) {
        const thread = try cancel_region.awaitIoUring();
        thread.enqueue().* = .{
            .opcode = .LINKAT,
            .flags = 0,
            .ioprio = 0,
            .fd = old_dir,
            .off = @intFromPtr(new_path),
            .addr = @intFromPtr(old_path),
            .len = @bitCast(new_dir),
            .rw_flags = flags,
            .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,
            .DQUOT => return error.DiskQuota,
            .EXIST => return error.PathAlreadyExists,
            .IO => return error.HardwareFailure,
            .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,
            .PERM => return error.PermissionDenied,
            .ROFS => return error.ReadOnlyFileSystem,
            .XDEV => return error.CrossDevice,
            .ILSEQ => return error.BadPathName,
            .FAULT => |err| return errnoBug(err),
            .INVAL => |err| return errnoBug(err),
            else => |err| return unexpectedErrno(err),
        }
    }
}