__bio_clone: don't calculate hw/phys segment counts

If the users sets a new ->bi_bdev on the bio after __bio_clone() has
returned it, the "segment counts valid" flag still remains even though
it may be different with the new target. So don't calculate segment
counts in __bio_clone().

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/bio.c

@@ -248,20 +248,20 @@ inline int bio_hw_segments(struct request_queue *q, struct bio *bio)
  */
 void __bio_clone(struct bio *bio, struct bio *bio_src)
 {
-	struct request_queue *q = bdev_get_queue(bio_src->bi_bdev);
-
 	memcpy(bio->bi_io_vec, bio_src->bi_io_vec,
 		bio_src->bi_max_vecs * sizeof(struct bio_vec));
 
+	/*
+	 * most users will be overriding ->bi_bdev with a new target,
+	 * so we don't set nor calculate new physical/hw segment counts here
+	 */
 	bio->bi_sector = bio_src->bi_sector;
 	bio->bi_bdev = bio_src->bi_bdev;
 	bio->bi_flags |= 1 << BIO_CLONED;
 	bio->bi_rw = bio_src->bi_rw;
 	bio->bi_vcnt = bio_src->bi_vcnt;
 	bio->bi_size = bio_src->bi_size;
 	bio->bi_idx = bio_src->bi_idx;
-	bio_phys_segments(q, bio);
-	bio_hw_segments(q, bio);
 }
 
 /**