Don't allow normal users to set idle IO priority

It has all the normal priority inversion problems.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/ioprio.c b/fs/ioprio.c
index 97e1f08..d1c1f2b 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -62,6 +62,8 @@
 
 			break;
 		case IOPRIO_CLASS_IDLE:
+			if (!capable(CAP_SYS_ADMIN))
+				return -EPERM;
 			break;
 		default:
 			return -EINVAL;