The current stable Linux 4.x kernel apparently can have a data corruption problem when using the EXT4 file system - mostly when used in a RAID 0 configuration. That's not very good news, but at least it's out in the open and being fixed.
A Phoronix reader, Zoltán Tősér, wrote into Phoronix today about an unpatched EXT4 data corruption bug present as of the Linux 4.0.2 kernel. He explained, "several people were affected by an ext4 data corruption bug in Linux 4.0.2. The bug is reported to be unpatched even in the most recent stable version, Linux 4.0.4. We are not sure what exactly triggers the problem, using a RAID setup seems to have something to do with it. It is reported to affect multiple distributions, including Arch, Debian and Fedora, so it seems to be an upstream problem."Phoronix