block: add and use scsi_blk_cmd_ioctl

Introduce a wrapper around scsi_cmd_ioctl that takes a block device.

The function will then be enhanced to detect partition block devices
and, in that case, subject the ioctls to whitelisting.

Cc: linux-scsi@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Cc: James Bottomley <JBottomley@parallels.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index fbdf0d8..a2c11f3 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -690,6 +690,13 @@
 }
 EXPORT_SYMBOL(scsi_cmd_ioctl);
 
+int scsi_cmd_blk_ioctl(struct block_device *bd, fmode_t mode,
+		       unsigned int cmd, void __user *arg)
+{
+	return scsi_cmd_ioctl(bd->bd_disk->queue, bd->bd_disk, mode, cmd, arg);
+}
+EXPORT_SYMBOL(scsi_cmd_blk_ioctl);
+
 static int __init blk_scsi_ioctl_init(void)
 {
 	blk_set_cmd_filter_defaults(&blk_default_cmd_filter);