I found an apparent bug where writing data to UDF-formatted DVD+RW discs from a packet-writing device (such as /dev/pktcdvd/pktcdvd0) in kernel 3.11.0-12-generic seems to corrupt the disc's entire filesystem.
I found this while trying to initialize a new DVD+RW disc (for the first time since upgrading to 13.10), using the normal sequence of operations: first format the fresh disc (with dvd+rw-format), then attach a new packet-writing device (with pktsetup), then create a new empty UDF filesystem on that device (with mkudffs), and then mount that new filesystem (with mount). Every time I've done this before (as far as I can remember, at least) it worked, but this time the last step failed with this error:
I then tried rebooting the system (after having detached the packet writing device, forcing it to flush the blank-filesystem data to the disc) and retrying to mount the disc (this time in read-only mode, using the plain /dev/sr0 device node instead of a packet-writin device), but got the same error.
mount: wrong fs type, bad option, bad superblock on /dev/sr0,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
Immediately prior to trying to initialize the new disc, though, I had mounted two different partially-full DVD+RW discs (which had both been initialized from 13.04, before 13.10 was released) and written new files to them. So, I tried to read both of those discs, and found that both of them now also fail to mount! Then I tried reading some older DVD+RWs that had not been written to since upgrading to 13.10, and these still seem to work correctly.
Finally, I tried rebooting into kernel version 3.8.0-31-generic, redoing the mkudffs on the new DVD+RW, and retrying to mount the new filesystem; this time, it mounted successfully, so I copied files to it, unmounted it, detached the packet-writing device, remounted the disc in read-only mode (from the plain /dev/sr0 device), and again it appears to have been mounted correctly. Unfortunately, the two other discs still fail to mount from this kernel version, so it seems they've really been corrupted. This leads me to believe that the cause of the problems is a data-corruption bug that exists in the newer kernel version but not in the older one.
Note: searching the web for "3.11" data corruption lead me to this kernel patch, which fixes a bug in the bio_copy_data block-layer API function. I looked at the linux_3.11.0.orig.tar.gz and linux_3.11.0-12.19.diff.gz source-package files, and as far as I can tell, that bugfix is not yet in Ubuntu's linux-image-3.11.0-12-generic package as of version 3.11.0-12.19.
Update 2013-10-30: Today I tried rebuilding the linux-image-3.11.0-12-generic package with that one patch added, but unfortunately the problem still occurred for me when running on the new kernel, so it looks like this is a completely different bug. I suppose I should report it upstream.