On Thu, Jun 28, 2018 at 09:53:23AM -0600, Jens Axboe wrote:

On 6/27/18 2:12 PM, Bart Van Assche wrote:

quoted

Although __bio_clone_fast() copies bi_io_vec, it does not copy bi_vcnt,
the number of elements in bi_io_vec[] that contains data. Copy bi_vcnt
such that code that needs this member behaves identically for original
and for cloned requests.

Applied - it's correct for the current base.

Any users of cloned bio shouldn't use this bio's .bi_vcnt directly,
since this counter represents the original bio's actual io vector
number, nothing related with the cloned bio.

So I don't understand why we need to copy it.

Thanks,
Ming