Add Task 20 description

Task20/task20.txt

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+This is Task 20 of the Eudyptula Challenge
+------------------------------------------
+
+Networking filters turned out to be not all that complex in the end,
+great work with that.
+
+So, here's the final task.
+
+There might be other tasks that get created and sent out later on, but
+the original challenge had 20 tasks, so after finishing this one, you
+can consider yourself done!
+
+Let's try something a bit harder.  Something that might cause some data
+loss on a filesystem, always a fun thing to play with, if for no other
+reason than to not be afraid of things like that in the future.
+
+This task requires you to work on the fat filesystem code:
+  - Add an ioctl to modify the volume label of a mounted fat filesystem.
+    Be sure to handle both 16 and 32 bit fat filesystems {hint!}
+  - Provide a userspace .c program to test this new ioctl.
+
+That's it!  Seems so simple, right?  I wonder why that option isn't in
+the kernel tree already...
+
+Anyway, provide a patch to the kernel, and the .c file used to test the
+new ioctl, as well as "proof" of this working.  Make sure you don't run
+into 32/64bit kernel issues with the ioctl, if you do things correctly,
+you shouldn't have any problems.
+
+I recommend doing this work on either a loop-back fat filesystem on your
+"normal" filesystem, or on a USB stick.  Either will work just as well,
+and make things easier to debug and test.
+
+Watch out for locking issues, as well as dirty filesystem state
+problems.
+
+Best of luck!