[PATCH] loop: forward-port resource leak checks from Solar

Forward port of the patch by Solar and ported by Julio.

Compiles, boots, and passes my looptorturetest.sh.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Julio Auto <mindvortex@gmail.com>
Cc: Solar Designer <solar@openwall.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>