Comment 8 for bug 515937

This does sound possible - is this commit in a mainline Ubuntu kernel, and if so, which?

Quote from https://bugzilla.kernel.org/show_bug.cgi?id=16006

Comment #4 From Tejun Heo 2010-05-19 14:40:31 -------

FLUSH_EXT timed out which shouldn't happen but can. libata as of 2.6.32
doesn't retry after any FLUSH failure and just returns the error to upper layer
leading to fs ro remounting the device. The reason for the behavior is that
FLUSH failure often indicates (abort by device always does) data loss so
continuing RW operation is likely to cause massive filesystem corruption. As
the behavior caused some spurious failures like this, EH was updated to
distinguish between various FLUSH failure modes and retry unless it's certain
that the device aborted it. So, in short, please upgrade to newer kernel or
tell your distro to backport the update.

Thanks.