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+KNOWN Unionfs 2.1 ISSUES:
+=========================
+
+1. Unionfs should not use lookup_one_len() on the underlying f/s as it
+ confuses NFSv4. Currently, unionfs_lookup() passes lookup intents to the
+ lower file-system, this eliminates part of the problem. The remaining
+ calls to lookup_one_len may need to be changed to pass an intent. We are
+ currently introducing VFS changes to fs/namei.c's do_path_lookup() to
+ allow proper file lookup and opening in stackable file systems.
+
+2. Lockdep (a debugging feature) isn't aware of stacking, and so it
+ incorrectly complains about locking problems. The problem boils down to
+ this: Lockdep considers all objects of a certain type to be in the same
+ class, for example, all inodes. Lockdep doesn't like to see a lock held
+ on two inodes within the same task, and warns that it could lead to a
+ deadlock. However, stackable file systems do precisely that: they lock
+ an upper object, and then a lower object, in a strict order to avoid
+ locking problems; in addition, Unionfs, as a fan-out file system, may
+ have to lock several lower inodes. We are currently looking into Lockdep
+ to see how to make it aware of stackable file systems. In the meantime,
+ if you get any warnings from Lockdep, you can safely ignore them (or feel
+ free to report them to the Unionfs maintainers, just to be sure).
+
+For more information, see <http://unionfs.filesystems.org/>.
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1.5.2.2
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