K 10
svn:author
V 4
kato
K 8
svn:date
V 27
1997-04-14T10:52:25.000000Z
K 7
svn:log
V 445
Fix `lockmgr: locking against myself' panic by multi union mount of
same directory pair.

If we do:
    mount -t union a b
    mount -t union a b
then, (1) namei tries to lock fs which has been already locked by
first union mount and (2) union_root() tries to lock locked fs.  To
avoid first deadlock condition, unlock vnode if lowerrootvp is union
node, and to avoid second case, union_mount returns EDEADLK when multi
union mount is detected.

END