Hi!

I'm writing this device mapper target that stores checksums on writes and
verifies them on reads.

It's not widely tested, but you can run mke2fs on it and do basic file
operations. The to-do list is still large, and most of it can be found within
the code.

To test it, you will need to format the device using the (very rough) attached
tool, and then create the dm device with something like:

	echo 0 $SIZE csum $REALDEVICE 0 | dmsetup create $NAME


I think it can be useful for people who want to detect data corruption and are
either using the block layer directly or a filesystem that doesn't check data
integrity (which are most, if not all, of the popular ones today). Maybe it
could also be used for testing the bio-integrity extensions, although at the
moment it's completely independent and I haven't looked much, but it's on my
to-do list.

It does NOT pretend to be useful for consistency checks for security purposes.
Use something else if you do not want someone evil tampering with your data.


Comments are obviously welcome. There are also some questions embedded in the
code, if anyone cares to answer any of them, I'd really appreciate it.

Thanks a lot,
		Alberto