Right now, if it's an open of a negative dentry, a race is possible
with several openers who all try to instantiate/rehash the same
dentry and would hit a BUG_ON in d_add.
But in fact if we got a negative dentry in atomic_open, that means
we just revalidated it so no point in talking to MDS at all,
just return ENOENT and make the race go away completely.
Signed-off-by: Oleg Drokin <email@example.com>
Cc: stable <firstname.lastname@example.org> # 4.7+
Signed-off-by: Greg Kroah-Hartman <email@example.com>