Yosemite upgrade file system verify or repair failed

I was upgrading my 3-4 years old MacBook Pro to Yosemite. It got stuck during installation with pop up " OS X Could not be installed on your computer" . File system verify or repair failed. Quit installer and try it again.

But I did it 3 times and no progress. I am afraid to loose some data. I did run "Fsck -fy" couple of times to check whether there is any problem but it shows everything is ok.

Thanks for support.