scsi: Silence unnecessary warnings about ioctl to partition

commit 6d935928 upstream.

Sometimes, warnings about ioctls to partition happen often enough that they
form majority of the warnings in the kernel log and users complain. In some
cases warnings are about ioctls such as SG_IO so it's not good to get rid of
the warnings completely as they can ease debugging of userspace problems
when ioctl is refused.

Since I have seen warnings from lots of commands, including some proprietary
userspace applications, I don't think disallowing the ioctls for processes
with CAP_SYS_RAWIO will happen in the near future if ever. So lets just
stop warning for processes with CAP_SYS_RAWIO for which ioctl is allowed.

CC: Paolo Bonzini <pbonzini@redhat.com>
CC: James Bottomley <JBottomley@parallels.com>
CC: linux-scsi@vger.kernel.org
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[bwh: Backported to 3.2: use ENOTTY, not ENOIOCTLCMD]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

block/scsi_ioctl.c

@@ -721,11 +721,14 @@ int scsi_verify_blk_ioctl(struct block_device *bd, unsigned int cmd)
 		break;
 	}
 
+	if (capable(CAP_SYS_RAWIO))
+		return 0;
+
 	/* In particular, rule out all resets and host-specific ioctls.  */
 	printk_ratelimited(KERN_WARNING
 			   "%s: sending ioctl %x to a partition!\n", current->comm, cmd);
 
-	return capable(CAP_SYS_RAWIO) ? 0 : -ENOTTY;
+	return -ENOTTY;
 }
 EXPORT_SYMBOL(scsi_verify_blk_ioctl);