MacBook Pro 2011 rebooting on startup

Hold alt during startup, you will then be able to boot from something called "recovery partition". When that is booted, in the menu select "disk utility" and try to repair disk and/or volume.

Based on the fsck error that would be your Samsung SSD failing.

Since you can not boot in Safe mode or any other including recovery, your only option is to boot from a external drive.

Then try to repair your hard drive.

Tried everything posted here and in other Apple forums but it wouldn't work. In the end, I booted using a USB drive and deleted all existing partitions on the failing SSD. Once all partitions were cleaned, I reinstalled Yosemite and the computer is up and running again.