fix proc_fill_cache() in case of d_alloc_parallel() failure
If d_alloc_parallel() returns ERR_PTR(...), we don't want to dput()
that. Small reorganization allows to have all error-in-lookup
cases rejoin the main codepath after dput(child), avoiding the
entire problem.
Spotted-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Fixes: 0168b9e38c42 "procfs: switch instantiate_t to d_splice_alias()" Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>