Fix some bugs left in the failure path of run_helper by the previous patch:
it was missing one

os_close_file(fds[1])

which is conditional.  To use the goto handling model, I set the fd to -1
if it's already closed (I don't want to check if keeping one more pipe-end
open is no problem).

Also do some cosmethic cleanup:

* "err" was what we returned even on success, so just use a neutral "ret".

* use tabs, not spaces.

* a little more comments.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>