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 11eb695feb636fa5211067189cad25ac073e7fe5 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: be4d234d7aeb ("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>