Use memcpy_from_bvec instead of open coding the logic.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727055646.118787-13-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>