That means you have a lot of files that baloo needs to index (same for every distro shipping baloo).
To get rid of it increase the limit for baloo, check your current limit:
cat /proc/sys/fs/inotify/max_user_watches
To raise, create a new file, example:
kdesu kate /etc/sysctl.d/97-kde-baloo-filewatch-inotify.conf
and write:
fs.inotify.max_user_watches = 32768 or raise to 65536