block: assign bi_bdev for cloned bios in blk_rq_prep_clone

bio_clone_fast() sets the cloned bio to have the same ->bi_bdev as the
source bio. This means that when request-based dm called setup_clone(),
the cloned bio had its ->bi_bdev pointing to the dm device. After Commit
0b6e522 ("blk-mq: use ->bi_bdev for I/O accounting")
__blk_account_io_start() started using the request's ->bio->bi_bdev for
I/O accounting, if it was set. This caused IO going to the underlying
devices to use the dm device for their I/O accounting.

Set up the proper ->bi_bdev in blk_rq_prep_clone based on the whole
device bdev for the queue the request is cloned onto.

Fixes: 0b6e522 ("blk-mq: use ->bi_bdev for I/O accounting")
Reported-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
[hch: the commit message is mostly from a different patch from Benjamin]
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
Link: https://lore.kernel.org/r/20220118070444.1241739-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -2976,6 +2976,7 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
 		bio = bio_clone_fast(bio_src, gfp_mask, bs);
 		if (!bio)
 			goto free_and_out;
+		bio->bi_bdev = rq->q->disk->part0;
 
 		if (bio_ctr && bio_ctr(bio, bio_src, data))
 			goto free_and_out;