The only complication I can think of, offhand, is when two processes open a
file on an "underlying" file system and one then decides to write to the
thing. When that happens, the kernel obviously needs to copy the file. Now
what happens to the other process? Easy, it still has the inode of the old
file open and it'll keep that inode. This obviously means that no two
processes can open the same underlying file for writing because the kernel
would then have to create two distinct new files with the same name, but
IMHO that's not (much of) a problem.
Unix file system semantics don't work well with unionized file systems,
anyway. Use Plan 9 when you want to do that. ;-)
--
Matthias Urlichs \ noris network GmbH / Xlink-POP N�rnberg
Schleiermacherstra�e 12 \ Linux+Internet / EMail: urlichs@noris.de
90491 N�rnberg (Germany) \ Consulting+Programming+Networking+etc'ing
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