[PATCH] drivers/block/loop.c: don't return garbage if LOOP_SET_STATUS not called

While writing a version of losetup, I ran into the problem that the loop
device was returning total garbage.

It turns out the problem was that this losetup was only issuing the
LOOP_SET_FD ioctl and not issuing a subsequent LOOP_SET_STATUS ioctl.  This
losetup didn't have any special status to set, so it left out the call.

The deeper cause is that loop_set_fd sets the transfer function to NULL,
which causes no transfer to happen lo_do_transfer.

This patch fixes the problem by setting transfer to transfer_none in
loop_set_fd.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/block/loop.c

@@ -818,7 +818,7 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
 	lo->lo_device = bdev;
 	lo->lo_flags = lo_flags;
 	lo->lo_backing_file = file;
-	lo->transfer = NULL;
+	lo->transfer = transfer_none;
 	lo->ioctl = NULL;
 	lo->lo_sizelimit = 0;
 	lo->old_gfp_mask = mapping_gfp_mask(mapping);