Last week it was discovered an EXT4 file-system corruption bug
hit the stable Linux kernel. The true cause of this EXT4 bug has now been uncovered and patched within the mainline Linux kernel.
The EXT4 corruption issue was fixed with this commit
and Ted Ts'o describes it as:
This fixes the root cause of the ext4 data corruption bug which raised a ruckus on LWN, Phoronix, and Slashdot.
This bug only showed up when non-standard mount options (journal_async_commit and/or journal_checksum) were enabled, and when the file system was not cleanly unmounted, but the root cause was the inode bitmap modifications was not being properly journaled.
This could potentially lead to minor file system corruptions (pass 5 complaints with the inode allocation bitmap) after an unclean shutdown under the wrong/unlucky workloads, but it turned into major failure if the journal_checksum and/or jouaral_async_commit was enabled.