14 DAY TRIAL // Apparently, there's a data corruption issue in the EXT4 file system for multiple Linux kernel branches, affecting several mainstream distributions, including Arch Linux, Fedora, and Debian GNU/Linux.
Several Arch Linux users have already reported data loss after upgrading to Linux kernel 4.0.2, the latest version available in the main software repositories of the respective operating system, which had already been flagged as out of date since May 17, 2015.
However, the EXT4 data corruption issue has not been fixed in Linux kernel 4.0.3, nor Linux kernel 4.0.4, according to an Arch Linux user who reported problems with a RAID (redundant array of independent disks) configuration a couple of days ago on the official forums of the distribution.
The issue is also confirmed by a Phoronix reader, who says, "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."
The EXT4 data corruption issue has been confirmed by Debian users too
According to a recent bug report submitted in Debian's bug tracking system, users noticed major data loss and massive filesystem corruption in the Linux kernel 4.0.2 packages. It appears that the issue was patched in the upstream Linux 4.0.3 kernel, as Softpedia reported the news last week, on May 14, 2015.
The fact of the matter is that the respective data corruption in the EXT4 file system, which was caused by delayed and unwritten extents, was patched in the Linux kernels 3.10.78 LTS and 3.14.42 LTS too. As such, all users are urged to upgrade to the latest versions of the Linux kernels available in their distributions as soon as they become live in the main repositories.