block: clear bio->bi_bdev when putting a bio back in the cache

block: clear bio->bi_bdev when putting a bio back in the cache

commit fa44d6787b2832cd96c1cad15cc135d661a9a629 upstream.

This isn't strictly needed in terms of correctness, but it does allow
polling to know if the bio has been put already by a different task
and hence avoid polling something that we don't need to.

Cc: stable@vger.kernel.org
Fixes: 94b92e98906a ("bio: add allocation cache abstraction")
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>