List mounted filesystems.

def _get_mounts(fs_type=None):
    '''
    List mounted filesystems.
    '''
    mounts = {}
    with salt.utils.files.fopen('/proc/mounts') as fhr:
        for line in fhr.readlines():
            line = salt.utils.stringutils.to_unicode(line)
            device, mntpnt, fstype, options, fs_freq, fs_passno = line.strip().split(" ")
            if fs_type and fstype != fs_type:
                continue
            if mounts.get(device) is None:
                mounts[device] = []

            data = {
                'mount_point': mntpnt,
                'options': options.split(",")
            }
            if not fs_type:
                data['type'] = fstype
            mounts[device].append(data)
    return mounts