10 weeks ago,
  http://linux.bkbits.com:8080/linux-2.5/cset@415b3380pxf4sB97gM8ujLqDxi6GfQ

The patch was mostly right, and fixed a real problem, but missed a bit.

It passed the job of checking if an inode had a current alias off to
d_find_alias instead of open-coding it in d_alloc_anon.  However there is one
case where d_alloc_anon would not return the right dentry.  That case being
when the inode was for the root of the filesystem.

The root is a special case because it is not hashed.  All other dentries that
are not hashed are quite un-interesting: There are "unlinked" but not yet
closed.  The root of a filesystem is unhashed, but is interesting.

Allowing d_find_alias to return an unhashed alias for a directory solves this
problem.  It is safe because callers of d_find_alias on a directory inode
either have a name for the inode already (so finding an unlinked directory by
mistake is impossible) or will soon be looking for a name and will drop the
dentry if a name is not found.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>