[PATCH v6] Stop periodic syncing if filesystem is already shutdown.

[Christoph Hellwig]

Looks good, but one thing I'd love here is to actually print a useful
error for the typical EIO case, as the "error 5 occured" message just
confuses the heck out of people.  What it means is that we got an
EIO error from the block device, and that's what we should print.

Probably worth doing in a separate patch, so:

Reviewed-by: Christoph Hellwig <hch at lst.de>